Method and apparatus for mitigating differences in edge roller shape

Abstract

A glass manufacturing method includes forming a glass ribbon from a molten material. The glass ribbon includes a first surface and a second surface. The method includes contacting the first surface with a first edge roller and the second surface with a second edge roller, rotating the first edge roller at a first rotational speed and rotating the second edge roller at a second rotational speed. The method includes generating a first torque signal representative of a torque applied to the first edge roller and a second torque signal representative of a second torque applied to the second edge roller. The method also includes time-dependently modulating the first rotational speed and the second rotational speed to counter variations in a torque sum signal of the first torque signal and the second torque signal.

Description

[Technical Field]

[0001] [Cross-reference with related applications] This application claims priority under Section 119 of the United States Patent Act to U.S. Provisional Patent Application No. 63 / 220,110, filed on 9 July 2021, the contents of which are reliable and are incorporated herein by reference in their entirety.

[0002] This specification generally relates to apparatus and methods for manufacturing glass ribbons. [Background technology]

[0003] Glass molding equipment is commonly used to form various glass products, such as glass sheets used in LCD displays. These glass sheets can be manufactured using the down-draw method, which forms a continuous glass ribbon by flowing molten glass downwards onto a molding wedge. In the down-draw method, various rollers can be used to apply traction to the continuous glass ribbon, apply tension to the ribbon, or guide the glass ribbon. For example, edge rollers can guide the glass ribbon by gripping its edges. Such edge rollers can be arranged in pairs so as to contact both sides of the glass ribbon. If the edge rollers do not have a corresponding shape, the separation distance between the rollers may change as a function of time (e.g., with the rotation of the edge rollers), which can cause variations in the thickness of the glass sheet. Such variations in thickness can make the glass sheet unsuitable for certain applications, such as high-definition displays. [Overview of the project] [Means for solving the problem]

[0004] A first aspect of the present disclosure is a glass manufacturing method comprising: forming a glass ribbon including a first surface and a second surface from a predetermined amount of molten material; bringing the first surface into contact with a first edge roller and the second surface into contact with a second edge roller; rotating the first edge roller at a first rotational speed and rotating the second edge roller at a second rotational speed; generating a first torque signal representing the torque applied to the first edge roller and a second torque signal representing the second torque applied to the second edge roller; generating a torque sum signal of the first torque signal and the second torque signal; and modulating the first rotational speed and the second rotational speed in a time-dependent manner to cancel out fluctuations in the torque sum signal.

[0005] A second aspect of this disclosure involves modulating the first and second rotational speeds in a time-dependent manner using the following equation: ω T =A*sin(θ 1,2 +Φ)+ω N , using the target rotation speed ω T This involves periodically modulating the first and second rotational speeds by calculating Θ, where A is the modulation amplitude and Θ 1、2 is the angular position of the first or second edge roller, Φ is the modulation phase, and ω N The first edge roller and the second edge roller Official The method includes a first embodiment, where the rotational speed is the rotational speed.

[0006] A third aspect of the present disclosure includes a method according to the first or second aspect, further comprising determining a time delay between a roll position signal representing an angular position and a torque sum signal, and determining the modulation phase by converting the time delay into a phase angle.

[0007] A fourth aspect of the present disclosure further includes filtering the torque sum signal using a bandpass filter having an upper cutoff frequency and a lower cutoff frequency before determining the modulation phase, ω NHowever, this includes a method according to any of the first to third embodiments, which lies between the upper cutoff frequency and the lower cutoff frequency.

[0008] A fifth aspect of the present disclosure includes a method according to any of the first to fourth aspects, further comprising sensing the thickness of a glass ribbon downstream of a first edge roller and a second edge roller, and determining a modulation amplitude A based on the thickness of the glass ribbon.

[0009] A sixth aspect of the present disclosure includes a method according to any of the first to fifth aspects, wherein determining a modulation amplitude A includes periodically modulating a first angular velocity and a second angular velocity using a first value of the modulation amplitude A; determining whether the thickness variation of the glass ribbon has decreased as a result of the first value; and, if the thickness variation of the glass ribbon has decreased as a result of the first value, increasing the modulation amplitude A until no further decrease in thickness variation is observed.

[0010] A seventh aspect of the present disclosure includes a method according to any of the first to sixth aspects, wherein the first edge roller and the second edge roller have different cross-sectional shapes such that the separation distance between the first edge roller and the second edge roller changes periodically as the first edge roller and the second edge roller rotate.

[0011] An eighth aspect of the present disclosure includes a method according to any of the first to seventh aspects, wherein the torque sum signal functions as a substitute for the separation distance such that the separation distance is greater than the average distance when the torque sum signal is greater than the average torque value.

[0012] A ninth aspect of the present disclosure includes a method according to any of the first to eighth aspects, wherein modulating a first rotational speed and a second rotational speed to cancel out a change in the torque sum signal includes decreasing at least one of the first rotational speed and the second rotational speed during periods when the separation distance is increasing, and increasing at least one of the first rotational speed and the second rotational speed during periods when the separation distance is decreasing.

[0013] A tenth aspect of the present disclosure includes a method according to any of the first to ninth aspects, wherein modulating the first rotational speed and the second rotational speed to cancel out changes in the torque sum signal reduces the moving window thickness range of the glass ribbon achieved when the first rotational speed and the second rotational speed are not modulated.

[0014] An eleventh aspect of the present disclosure is a glass manufacturing method, comprising: forming a glass ribbon including a first surface and a second surface from a predetermined amount of molten material; contacting the first surface with a first edge roller and the second surface with a second edge roller, wherein the first edge roller and the second edge roller have different cross-sectional shapes such that the separation distance between the first edge roller and the second edge roller changes periodically according to the speeds at which the first edge roller and the second edge roller rotate; driving the first edge roller and the second edge roller at a first rotational speed and a second rotational speed respectively; generating a torque sum signal representing the total torque applied to the first edge roller and the second edge roller; determining a time delay between the torque sum signal and an electrical roll position signal representing one or both of the first rotational position and the second rotational position; and updating the first rotational speed and the second rotational speed based on the time delay, the first rotational position, and the second rotational position.

[0015] A twelfth aspect of the present disclosure includes a method according to the eleventh aspect, wherein the updating step includes modulating the first rotational speed and the second rotational speed as a function of time.

[0016] <00000​​​​​​​​​​​N is the rotational speed of the first edge roller and the second edge roller, and includes the method according to any one of aspects 11 to 13. Official

[0017] A fourteenth aspect of the present disclosure further includes sensing the thickness of the glass ribbon downstream of the first edge roller and the second edge roller, and determining the modulation amplitude A based on the thickness of the glass ribbon, and includes the method according to any one of aspects 11 to 13.

[0018] A fifteenth aspect of the present disclosure is that determining the modulation amplitude A includes periodically modulating the first angular velocity and the second angular velocity using a first value of the modulation amplitude A, and determining whether the thickness variation of the glass ribbon has decreased as a result of the first value, and increasing the modulation amplitude A until the decrease in the thickness variation is no longer observed when the thickness variation of the glass ribbon has decreased as a result of the first value, and includes the method according to any one of aspects 11 to 14.

[0019] A sixteenth aspect of the present disclosure includes the method according to any one of aspects 11 to 15, in which the torque sum signal functions as a substitute for the separation distance such that the separation distance becomes greater than the average distance when the torque sum signal is greater than the average torque value.

[0020] A seventeenth aspect of the present disclosure includes the method according to any one of aspects 11 to 16, in which the step of updating includes increasing the first rotational speed.

[0021] ​An eighteenth aspect of the present disclosure relates to a glass manufacturing apparatus, comprising a forming body configured to form a glass ribbon from a predetermined amount of molten material, defining a stretching path extending from the forming body on which a glass ribbon can be formed; and an edge roll assembly comprising an edge roller pair, the first having a first cross-sectional shape and the second having a second cross-sectional shape, disposed on both sides of the stretching path, wherein the first cross-sectional shape differs from the second cross-sectional shape such that they are separated from each other by a separation distance that varies with the speed at which the first and second edge rollers rotate; and a first edge roller mechanically coupled to the first and second edge rollers, the first edge roller rotating The apparatus includes one or more drive units configured to rotate a second edge roller at a first rotational speed around a second rotation axis and to rotate a second edge roller at a second rotational speed around a second rotation axis, and further configured to generate a first torque signal representing a first torque applied to the first edge roller and a second torque signal representing a second torque applied to the second edge roller; and a controller communicatively coupled to one or more drive units and operable to generate a torque sum signal from the first torque signal and the second torque signal, and to use the torque sum signal to modulate the first rotational speed and the second rotational speed such that the first rotational speed and the second rotational speed are inversely proportional to a variable separation distance.

[0022] A 19th aspect of the present disclosure includes an apparatus according to the 18th aspect, further comprising a thickness sensor configured to sense the thickness of a glass ribbon downstream of a first edge roller and a second edge roller, wherein a controller is operable to modulate a first rotational speed and a second rotational speed based on the thickness of the glass ribbon.

[0023] A 20th aspect of the present disclosure includes an apparatus according to the 18th or 19th aspect, wherein the controller is operable to periodically modulate a first rotational speed and a second rotational speed using a modulation phase calculated based on a time delay between a torque sum signal and an electric roll position signal generated by one or more drive units, and the electric roll position signal represents the rotational position of at least one of the first edge roller or the second edge roller.

[0024] The following detailed description illustrates further features and advantages of a glass ribbon manufacturing apparatus and method, and of interchangeable heating cartridges used in such apparatus and method, some of which will be readily apparent to those skilled in the art from this description, or will be recognized by carrying out the embodiments described herein, including the detailed description and accompanying drawings in accordance with the claims.

[0025] The general description above and the detailed description below describe various embodiments, which should be understood as intended to provide an overview or framework for understanding the nature and characteristics of the claimed subject matter. The accompanying drawings are included to provide a further understanding of the various embodiments and are incorporated herein and constitute part of this specification. These drawings illustrate the various embodiments described herein and serve together with this specification to illustrate the principles and operation of the claimed subject matter. [Brief explanation of the drawing]

[0026] [Figure 1] This is a schematic diagram of a glass manufacturing apparatus according to one or more embodiments illustrated and described herein. [Figure 2] This is a schematic cross-sectional view of a glass manufacturing apparatus according to one or more embodiments described herein, taken along line 2-2 in Figure 1. [Figure 3A] This is a schematic cross-sectional view of a glass manufacturing apparatus according to one or more embodiments described herein, taken along line 3-3 in Figure 2. [Figure 3B]This is a schematic diagram of a plot of the separation distance between edge rollers of an edge roller pair in a glass manufacturing apparatus shown in Figures 1 to 3A, according to one or more embodiments described herein. [Figure 4A] This figure shows a plot of the torque sum signal of the torque supplied to the edge rollers of an edge roller pair in a glass manufacturing apparatus, according to one or more embodiments described herein. [Figure 4B] This figure shows the periodic domain transformation of the torque sum signal plot shown in Figure 4A, according to one or more embodiments described herein. [Figure 5A] This figure shows a frequency domain plot of the low-pass filter portion of a band-pass filter used to filter a torque sum signal according to one or more embodiments described herein. [Figure 5B] This figure shows a frequency domain plot of the high-pass filter portion of a bandpass filter used to filter a torque sum signal according to one or more embodiments described herein. [Figure 6A] This is a plot of the unfiltered torque sum signal of the torque supplied to the edge rollers of an edge roller pair of a glass manufacturing apparatus according to one or more embodiments described herein. [Figure 6B] This figure shows a plot of the filtered torque sum signal generated by filtering the torque sum signal in Figure 6A using the bandpass filters shown in Figures 4A and 4B, according to one or more embodiments described herein. [Figure 7] This figure shows a plot including a torque sum signal overlaid on an electric roller position signal, according to one or more embodiments described herein. [Figure 8] This is a flowchart illustrating a method for modulating the rotational speed of an edge roller in a glass manufacturing apparatus, according to one or more embodiments described herein. [Figure 9] This is a flowchart of a method for determining the modulation phase and modulation amplitude that can be used to modulate the rotational speed in the method of Figure 8, according to one or more embodiments described herein. [Figure 10] This figure shows a plot of the thickness flapping tendency of a glass ribbon generated by using multiple modulation amplitudes to modulate the rotational speed of an edge roller, according to one or more embodiments described herein. [Modes for carrying out the invention]

[0027] The following describes in detail embodiments of a glass ribbon manufacturing apparatus and method in which the rotational speed of edge rollers is modulated in a time-dependent manner to cancel out changes in the torque summation signal associated with the edge roller pair. Wherever possible, the same reference numerals are used throughout the drawings for references to the same or similar parts. The glass ribbon manufacturing apparatus of this disclosure may include a glass forming body that forms a glass ribbon from a predetermined amount of molten material, and a plurality of edge rollers positioned downstream from the glass forming body. The plurality of edge rollers may include an edge roller pair, which includes a first edge roller and a second edge roller positioned to contact both sides of the glass ribbon. One or more drive units can rotate the first and second edge rollers at first and second rotational speeds, and generate a torque signal representing the torque applied to the first and second edge rollers. The first edge roller has a different cross-sectional shape from the second edge roller, so that the separation distance between the first and second edge rollers can change as a function of time, and thus the torque signal also changes as a function of time. A controller can receive the torque signal and generate a torque summation signal. The controller can modulate the rotational speed at which one or more drive units rotate the first and second edge rollers in order to cancel out fluctuations in the torque sum signal. Such time-dependent modulation can reduce variations in the separation distance between the first and second edge rollers, thereby suppressing variations in the thickness of the glass ribbon. As a result, glass sheets manufactured through the apparatus described herein can have a more uniform wall thickness than glass sheets manufactured without time-dependent roller speed modulation.

[0028] As used herein, the term "thickness flapping" refers to periodic thickness fluctuations that occur in the stretching direction near the edges of a glass ribbon while it is being formed using a downdraw method (e.g., fusion draw method, slot draw method).

[0029] Figure 1 schematically shows an embodiment of an apparatus 10 for manufacturing glass such as glass ribbon 12. The apparatus 10 generally includes a melting vessel 15 configured to receive batch material 16 from a storage bin 18. The batch material 16 can be introduced into the melting vessel 15 by a batch delivery device 20 driven by a motor 22. An optional controller 24 can be provided to operate the motor 22, and a molten glass level probe 28 can be used to measure the glass melting level in a standpipe 30 and transmit the measured information to the controller 24.

[0030] The apparatus 10 may also include a fining vessel 38, such as a fining tube, located downstream of the molten vessel 15 and connected to the molten vessel 15 via a first connecting pipe 36. A mixing vessel 42 may also be located downstream of the fining vessel 38. A dispensing vessel 46 may be located downstream of the mixing vessel 42. As shown in the figure, a second connecting pipe 40 connects the fining vessel 38 to the mixing vessel 42, and a third connecting pipe 44 connects the mixing vessel 42 to the dispensing vessel 46. Furthermore, as shown in the figure, a downcomer 48 is located to dispensing the molten glass from the dispensing vessel 46 to the inlet 50 of the molding vessel 60. The schematic embodiment shown in Figure 1 is an example of various glass processing stations in which the molten vessel 15, fining vessel 38, mixing vessel 42, dispensing vessel 46, and molding vessel 60 can be arranged in series along the apparatus 10.

[0031] The melting vessel 15 is typically formed from a refractory material such as refractory (e.g., ceramic) brick. The apparatus 10 may further include components typically formed from platinum or platinum-containing metals such as platinum-rhodium, platinum-iridium, and combinations thereof, but these components may also include refractory metals such as molybdenum, palladium, rhenium, tantalum, titanium, tungsten, ruthenium, osmium, zirconium, and alloys thereof and / or zirconium dioxide. The platinum-containing components may include one or more of the first connecting pipe 36, clarifying vessel 38, second connecting pipe 40, standpipe 30, mixing vessel 42, third connecting pipe 44, delivery vessel 46, descending pipe 48, and inlet 50. The forming vessel 60 may also be formed from a refractory material and is designed to form the glass molten material into a glass ribbon 12.

[0032] Figure 2 is a cross-sectional perspective view of the apparatus 10 along line 2-2 in Figure 1. As shown, the molding vessel 60 includes a forming wedge 62, which includes a pair of downwardly inclined forming surface portions 66a, 66b extending between its ends 64a, 64b. The downwardly inclined forming surface portions 66a, 66b converge along the stretching direction 68 to form a bottom edge, which will hereafter be called the root 70. The molten glass 17 can fill the trough extending between the ends 64a, 64b, extend downward along the downwardly inclined forming surface portions 66a, 66b, and converge at the root 70 to form a glass ribbon 12. The stretching surface 72 penetrates the root 70. The glass ribbon 12 can be drawn out along the stretching surface 72 in the stretching direction 68. The stretched surface 72 penetrates the base 70 perpendicularly, dividing the molding container 60 in two. However, it should be understood that in other configurations, the stretched surface 72 does not penetrate the base 70 perpendicularly. Figures 1 and 2 show a rough illustration of one embodiment of a glass molding apparatus and molding container, but it should be understood that embodiments of this disclosure can be used with various other molding container configurations.

[0033] Referring next to Figures 1 and 2, the apparatus 10 also includes at least one edge roller assembly for drawing the glass ribbon from the base 70 of the molding container 60. For example, the illustrated apparatus 10 includes first and second edge roller assemblies 130a and 130b (see Figure 1). The first edge roller assembly 130a includes a first pair of edge rollers 132 configured to engage with a first edge of the glass ribbon 12 as the glass ribbon 12 is drawn from the base 70 of the molding wedge 62. The second edge roller assembly 130b includes a second pair of edge rollers 134 configured to engage with another second edge of the glass ribbon 12 as the glass ribbon 12 is drawn from the base 70 of the molding wedge 62. The first and second edge roller assemblies 130a and 130b assist in drawing the glass ribbon 12 from the base 70 of the molding wedge 62. For example, the first and second edge roller assemblies 130a, 130b can provide the desired edge characteristics and correct fusion of the edge portions of the molten glass 17 drawn from both sides of the downward-sloping molding surface portions 66a, 66b. In some embodiments, the first and second edge roller assemblies 130a, 130b can be positioned at various locations within the viscous region of the glass drawn from the base 70. For example, in some embodiments, the first and second edge roller assemblies 130a, 130b can be positioned directly below the base 70. In some embodiments, the first and second edge roller assemblies 130a, 130b are positioned below the base 70 by a distance that may depend on the composition of the glass ribbon 60 and other factors in the manufacturing process (e.g., stretching speed, thickness of the glass ribbon, etc.).

[0034] Figures 2 and 3A show one embodiment of the first edge roller assembly 130a. The second edge roller assembly 130b (see Figure 1) can be substantially identical in structure to the first edge roller assembly 130a in some embodiments. As shown in Figure 2, the first edge roller assembly 130a includes a first edge roller pair 132. The first edge roller pair 132 includes a first edge roller 132a and a second edge roller 132b. The first and second edge rollers 132a and 132b are configured to engage simultaneously with the first main surface 110a and the second main surface 110b of the glass ribbon 12, respectively, when the glass ribbon 12 is pulled out from the base 70 of the forming wedge 62. The first edge roller assembly 130a includes a first shaft 136 mechanically coupled to the first edge roller 132a and a second shaft 138 mechanically coupled to the second edge roller 132b. Figure 2 shows the first and second shafts 136, 138 as substantially cylindrical and extending linearly between the first and second edge rollers 132a, 132b in a direction perpendicular to the stretching direction 68 (e.g., the x-direction of the coordinate axes shown in Figure 2). In embodiments, the first and second shafts 136, 138 may pass through a housing (not shown) that houses the glass ribbon 12. The housing can help shield components of the apparatus 10 (e.g., one or more drive units 137, the controller 150 shown in Figure 1) and maintain a controlled environment around the glass ribbon. Other forms of the first and second shafts 136, 138 are also conceivable and within the scope of this disclosure. For example, in embodiments, the first and second shafts 136, 138 may extend at least partially in the stretching direction 68 (e.g., obliquely to the x-axis shown in Figure 2).

[0035] In the embodiment, the first and second shafts 136, 138 are rotationally driven by one or more drive units 137. One or more drive units 137 are mechanically coupled to the first and second edge rollers 132a, 132b so as to rotate the first edge roller 132a around the first rotation axis 140a at a first rotational speed ω1 and the second edge roller 132b around the second rotation axis 140b at a second rotational speed ω2. In the embodiment, the first and second rotational speeds ω1, ω2 are equal to and opposite to each other (for example, the first edge roller 132a can rotate clockwise and the second edge roller 132b can rotate counterclockwise so that the first edge roller assembly 130a guides the glass ribbon 12 in the stretching direction 68). In the embodiment, the first and second rotational speeds ω1, ω2 are selected to correspond to a desired stretching speed of the glass ribbon.

[0036] In the embodiment, one or more drive units 137 include a preferred drive mechanism (e.g., a preferred motor such as an electric motor or hydraulic motor, or other preferred actuator) configured to rotate the first and second edge rollers 132a, 132b around the first and second rotation shafts 140a, 140b. It should be understood that the one or more drive units 137 can take various forms. For example, in the embodiment, the first and second shafts 136, 138 are mechanically linked, and a single drive unit rotates both the first and second shafts 136, 138 with a single mechanical output such as a rotary drive shaft. In the embodiment, the mechanical output of one or more drive units 137 can be mechanically connected to the first and second shafts 136, 138 by a transmission or the like, causing the first and second shafts 136, 138 to rotate in a desired series of directions. One or more drive units 137 may include a first drive unit mechanically coupled to a first shaft 136 and a second drive unit mechanically coupled to a second shaft 138. In such embodiments, each drive unit can individually rotate one of the first and second edge rollers 132a, 132b.

[0037] In the embodiment, the apparatus 10 includes one or more pull roller assemblies (not shown) in addition to the first and second edge roller assemblies 130a, 130b. One or more pull roller assemblies can contact the first and second main surfaces 110a, 110b of the glass ribbon 12 to apply tension to the glass in order to determine the thickness 166 of the glass ribbon 12. The first and second edge roller assemblies 130a, 130b can cancel out variations in the width of the glass ribbon 12 (e.g., in the ±X directions shown on the coordinate axes of Figure 1) caused by the tension applied by the pull roller assemblies. The first and second edge roller assemblies 130a, 130b can be cooled to a temperature below the temperature of the glass ribbon 12 in order to cool the edges of the glass ribbon 12 so as to help suppress lateral contraction of the glass ribbon 12 below the base 70. The first and second edge roller assemblies 130a, 130b can also help to fuse different flows of molten glass 17 moving over the inclined molding surface portions 66a, 66b. In embodiments, one or more edge rollers of the first and second edge roller assemblies 130a, 130b include knurled surfaces which can prevent slippage of the glass ribbon 12 and provide further cooling.

[0038] Referring to Figures 1 and 2, in the embodiment, the apparatus 10 may include a thickness sensor 160 oriented to sense the thickness 166 of the glass ribbon 12. Although the thickness sensor 160 is shown to be aligned with the central portion of the glass ribbon 12 (for example, located between the first and second edge roller assemblies 130a, 130b), the thickness sensor 160 can be positioned to measure the thickness 166 at any location within the glass ribbon 12. For example, the thickness sensor 160 may be positioned below the first edge roller assembly 130a in the downward stretching direction (for example, the -Z direction of the coordinate axes shown in the figure). The thickness sensor 160 may be movable to measure the thickness 166 at various locations in the glass ribbon 12.

[0039] The thickness sensor 160 can take various forms depending on the implementation. For example, the thickness sensor 160 may include solid probes that contact the first and second main surfaces 110a and 110b to measure the thickness 166. In another example, the thickness sensor may employ a fluid (e.g., a gas) to sense the thickness 166 of the glass ribbon 12 based on feedback (e.g., pressure feedback) from a fluid flow impacting the first and second main surfaces 110a and 110b. In yet another example, the thickness sensor 160 may include an acoustic sensor. In the illustrated embodiment, the thickness sensor 160 is a laser sensor that emits a laser beam that is incident on the glass ribbon 12 at the measurement position 170. A first portion of the laser beam is reflected from the first main surface 110a, and a second portion of the laser beam passes through the glass ribbon and is reflected from the second main surface 110b. The reflected light is detected by the thickness sensor, and the difference between the signals reflected from the first and second main surfaces 110a and 110b can be used to measure the thickness 166. Figures 1 and 2 show a single thickness sensor 160, but some embodiments of the device 10 may also include multiple thickness sensors to measure the thickness 166 simultaneously at various locations.

[0040] In this embodiment, the thickness sensor 160 is communicatively coupled to the controller 150 of the device 10. As described herein, the thickness measurement can be used to determine the modulation amplitude A that the controller 150 uses to modulate the first and second rotational speeds ω1 and ω2 of the first and second edge rollers 132a and 132b. For example, the measurement from the thickness sensor 160 can be used to determine whether the variation in thickness 166 decreases over a predetermined measurement period (e.g., 10 minutes, 30 minutes, 60 minutes) by a particular modulation amplitude A, and whether the modulation amplitude A should be adjusted.

[0041] Referring to Figures 1, 3A, and 3B, the first and second edge rollers 132a and 132b may have different cross-sectional shapes. In the example shown in Figure 3A, for illustrative purposes, the first edge roller 132a is shown to include a first cross-sectional shape 142a that is substantially elliptical, while the second edge roller 132b is shown to include a second cross-sectional shape 142b that is substantially circular. Such different cross-sections may result from wear and / or machining errors of the first and second edge rollers 132a and 132b. As a result, the first and second edge rollers 132a and 132b may separate from each other (in a direction perpendicular to the extension direction 68) by a variable separation distance 144 as the first and second edge rollers 132a and 132b rotate. The variable separation distance 144 can vary depending on the rotational position of the first and second edge rollers 132a and 132b, respectively. For example, when the first and second edge rollers 132a and 132b rotate around the first and second rotation axes 140a and 140b (see Figure 2), the rotational positions of the first and second edge rollers 132a and 132b change as a function of time, depending on the first and second rotational velocities ω1 and ω2. As the first and second edge rollers 132a and 132b rotate, the portions of the first and second edge rollers 132a and 132b that are closest to each other in a direction perpendicular to the extension direction 68 (for example, the ±y direction shown in Figure 3) may change. For example, if the first and second rotational velocities ω1 and ω2 are of the same magnitude, the variable separation distance 144 can change periodically as a function of the first and second rotational velocities ω1 and ω2. The cross-sectional shapes shown by the first and second edge rollers 132a and 132b are just examples. As a result of mechanical wear of the first and second edge rollers 132a and 132b, the surface profile of the rollers may become complex, such that the variable separation distance 144 changes in a way different from that shown in Figure 3B as a function of rotational position.

[0042] Figure 3B shows a plot 300 of the variable separation distance 144 in an example where the first and second edge rollers 132a and 132b rotate at the same rotational speed. The x-axis in Figure 3B is normalized time (e.g., as a ratio to the rotation period), and the y-axis is the magnitude of the normalized variable separation distance. As shown in the figure, the variable separation distance 144 changes according to a sine wave having a period corresponding to the rotational speed of the first and second edge rollers 132a and 132b (determined, for example, by one or more drive units 137). In one example, the variable separation distance 144 can change as the first and second edge rollers 132a, 132b rotate at the same speed according to a function having multiple frequency components, the frequency components of which change according to the difference in the radial dimension between the first and second edge rollers 132a, 132b at corresponding angular positions on the first and second edge rollers 132a, 132b (for example, related to how the first and second edge rollers 132a, 132b are initially aligned before being actuated by one or more drive units 137).

[0043] Due to the variable separation distance 144, the volume of molten glass in the glass ribbon 12 per unit time across the first edge roller pair 132 can vary as a function of the magnitude of the variable separation distance 144. For example, during time intervals when the first and second edge rollers 132a, 132b are relatively close to each other (e.g., within time interval 304 shown in Figure 3B), the flow of molten glass 17 between the first and second edge rollers 132a, 132b may be more obstructed than when they are relatively far apart (e.g., within time interval 302 shown in Figure 3B). If the flow of molten glass 17 through the first edge roller pair 132 is not constant in this way, the thickness of the glass ribbon 12 may fluctuate. In the example described herein with respect to Figures 3A and 3B, the thickness of the glass ribbon 12 near the edge to which the first edge roller pair 132 engages may fluctuate periodically according to the sine wave shown in Figure 3B. These thickness variations (thickness flapping) may render the glass sheets cut from the glass ribbon 12 unsuitable for some applications, such as use in high-definition displays. The roundness (out-of-roundness) of the edge rollers in the apparatus 10 may ultimately lead to thickness flapping of the glass ribbon.

[0044] In light of the foregoing, the apparatus 10 includes a controller 150 communicably coupled to one or more drive units 137 that control the rotation of the first and second edge rollers 132a, 132b. The controller 150 may include computer-readable instructions stored in memory 152 and executed by a processor 154. The processor 154 can access these instructions according to an addressing scheme that controls the operation of the first and second edge roller assemblies 130a, 130b in a manner described herein. The memory 152 may include one or more control modules configured to operate the first and second edge roller assemblies 130a, 130b using a feedback control scheme that utilizes torque signals generated by one or more drive units 137. For example, in an embodiment in which one or more drive units 137 include a single drive unit configured to rotate both the first and second shafts 136, 138, the single drive unit may generate a torque signal representing the total torque generated and transmitted to the first and second edge rollers 132a, 132b. In an embodiment in which one or more drive units 137 include a pair of drive units, and each drive unit is configured to rotate one of the first and second shafts 136, 138 individually, each drive unit can individually generate a torque signal representing the torque that is generated and transmitted to the first and second edge rollers 132a, 132b, respectively. A control module stored in memory 152 can analyze the torque signals generated via one or more drive units 137 and cause the processor 154 to use these torque signals to control the first and second angular velocities ω1, ω2.

[0045] Figures 4A and 4B show plots of the torque sum signal received by the controller 150 of the apparatus 10 described herein with respect to Figures 1 to 3B. Figure 4A shows a time-domain plot 400 of the torque sum signal (representing, for example, the sum of torques applied to the first and second shafts 136, 138 via one or more drive units 137). Figure 4B shows a period-domain (seconds) converted plot 402 of the torque sum signal shown in Figure 4A. As shown in Figure 4B, the torque sum signal includes a dominant periodic component 404 with a period of 12.5 seconds (s). In this example, the dominant periodic component 404 of the torque sum signal coincides with the rotation period of the first and second edge rollers 132a, 132b. While we do not wish to be bound by theory, the periodicity of the torque sum signal is thought to arise from the variable separation distance 144 (see Figure 3A). When the variable separation distance 144 is decreasing (or less than the average or median), it is assumed that one or more drive units 137 apply a relatively high torque to the first and second edge rollers 132a and 132b (for example, compared to when the variable separation distance 144 is at its minimum) in order to maintain the rotation of the first and second edge rollers 132a and 132b at the programmed speed due to friction with the glass ribbon 12. When the variable separation distance 144 is increasing (or greater than the median or average), it is assumed that a lower torque is applied to the first and second edge rollers 132a and 132b than when the variable separation distance 144 is decreasing (for example, compared to when the variable separation distance 144 is at its maximum). The larger the separation distance, the less friction there is with the molten glass 17, and the lower the torque required to maintain the nominal rotational speed.

[0046] Thus, the torque signals generated by one or more drive units 137 provide a feedback signal that substitutes for the magnitude of the variable separation distance 144. Referring to Figure 1 with this in mind, the controller 150 receives the torque signals and (for example, if one or more drive units 137 generate individual torque signals associated with each edge roller) generates a torque sum signal from the torque signals and can time-dependently modulate the first and second rotational speeds ω1, ω2 to cancel out the changes in the torque sum signal. For example, the controller 150 can suppress thickness flapping of the glass ribbon 12 by rotating the first and second shafts 136, 138 at variable speeds and controlling the operation of one or more drive units 137 to reduce the variability of the entire glass being pulled between the first and second edge rollers 132a, 132b.

[0047] In this embodiment, the controller 150 periodically modulates the first and second rotational speeds ω1 and ω2 of the first and second edge rollers 132a and 132b. In this embodiment, the controller 150 periodically modulates the first rotational speed ω1 and the second rotational speed ω2 according to the following: ω T =A*sin(θ 1,2 +Φ)+ω N (1) Here, ω T ω1 is the target speed related to the first rotational speed ω1 and the second rotational speed ω2, A is the modulation amplitude, and θ is the target speed related to the first rotational speed ω1 and the second rotational speed ω2, where A is the modulation amplitude and θ is the target speed related to the first rotational speed ω1 and the second rotational speed ω2, respectively. 1、2 is the angular position of the first edge roller 132a or the second edge roller 132b, Φ is the modulation phase, and ω N This is the nominal rotational speed of the first edge roller 132a and the second edge roller 132b (for example, related to the stretching speed of the glass ribbon 12).

[0048] In this embodiment, the controller 150 controls the value θ of equation 1. 1,2The system is configured to receive roll position signals indicating the position of the first and second shafts 136, 138 relative to a reference position. For example, in one embodiment, one or more drive units 137 include encoders that output electric roll position signals (e.g., voltage, current) that vary in proportion to the rotational position of the first and second shafts 136, 138 (e.g., in the range of 0° to just under 360°). The electric roll position signals generated by the encoders of one or more drive units 137 can vary periodically as a function of the first and second rotational speeds ω1, ω2. In one embodiment, the first and second rotational speeds ω1, ω2 are equal to the nominal rotational speed (e.g., before modulation) ω N Corresponds to the nominal rotational speed ω N This can be input to the controller 150 as a predetermined input related to the desired stretching speed of the glass ribbon 12.

[0049] The angular positions θ of the first edge roller 132a and the second edge roller 132b 1,2 This allows us to determine the magnitude of the variable separation distance 144. That is, the angular position θ 1,2 The size of the variable separation distance 144 can be determined according to the cross-sectional shapes of the first and second edge rollers 132a and 132b. However, accurate geometric information regarding the cross-sectional shapes of the first and second edge rollers 132a and 132b may not always be available (for example, the shapes of the first and second edge rollers 132a and 132b may change over the long-term operation of the device 10). Therefore, the electric roll position signals generated via one or more drive units 137 cancel out the variation in the variable separation distance 144 ω N In order to determine the degree of modulation, it may not be sufficient to determine the degree to which the variable separation distance 144 changes over time.

[0050] As described herein with reference to Figures 1, 3A, 3B, 4A, and 4B, the periodic fluctuation of the torque sum signal generated via one or more drive units 137 can serve as a substitute for a variable separation distance 144. The magnitude of the variable separation distance 144 can be estimated by the fluctuation of the torque sum signal with respect to the mean or median of the torque sum signal. Thus, using the torque sum signal, the ω in equation 1 can be expressed as N The degree of modulation can be determined.

[0051] The modulation phase Φ in equation 1 allows the controller 150 to determine the timing to modulate the first and second angular velocities ω1 and ω2 to a specific degree. The magnitude of the variable separation distance 144 is related to the rotational positions θ of the first and second edge rollers 132a and 132b, which are related to the magnitude of the torque sum signal as described above. 1,2 Considering its dependence, the modulation phase Φ can be determined based on the delay time between the reference electronic roll position signal and the torque sum signal. For example, the modulation phase Φ in equation 1 can be determined using the time delay between the start points of the corresponding periods of the torque sum signal and the electronic roll position signal. An example of determining such a time delay is illustrated in this specification with reference to Figure 7.

[0052] As shown in Figures 4A and 4B, the torque sum signal representing the torque applied to the first and second edge rollers 132a and 132b via one or more drive units 137 includes multiple frequency (or period) components in addition to the dominant period component 404 in the period associated with the first and second rotational speeds ω1 and ω2. As shown in the figure, the torque sum signal also includes multiple low-period (or high-frequency) components 406 and multiple high-period (or low-frequency) components 408.

[0053] In embodiments, the electric roll position signal may be independent of the precise geometric shapes of the first and second edge rollers 132a, 132b (and may not contain components derived from mechanical interaction between the rollers), so the electric roll position signal generated by the encoders of one or more drive units 137 may not contain the low-period component 406 and high-period component 408 of the torque sum signal. The low-period component 406 and high-period component 408 may not be due to radial variations in the edge roller shape. In embodiments, the low-period component 406 and high-period component 408 are due to mechanical and / or electrical noise. Therefore, since the phase difference measured between the torque sum signal and the electric roll position signal may vary during consecutive rotation periods, the low-period component 406 and high-period component 408 may cause inaccurate estimation of the modulation phase Φ described herein. Accordingly, the controller 150 of the apparatus 10 (see Figure 1) may include filtering logic to filter the torque sum signal generated by one or more drive units 137. The filtering logic is (for example, the nominal rotational speed ω in equation 1) N A bandpass filter can be implemented that passes through the spectral band of interest near component 404, which includes the targets for the first and second rotation speeds ω1 and ω2 (corresponding to ).

[0054] Figures 5A and 5B show frequency domain plots of the low-pass filter portion 500 and the high-pass filter portion 504 of a bandpass filter used for filtering a torque sum signal according to one embodiment. The low-pass filter portion 500 and the high-pass filter portion 504 can be used to filter out several low-period components 406 and high-period components 408 of the torque sum signal shown in Figures 4A and 4B. In this example, the dominant periodic component 404 (see Figure 4B) has a period of 12.5 s corresponding to a frequency of 0.08 Hz. As shown in Figure 5A, the low-pass filter portion 500 filters out signal components with frequencies above a cutoff frequency 502 of approximately 0.09 Hz. As shown in Figure 5B, the high-pass filter portion 504 filters out signal components with frequencies below a cutoff frequency 506 of approximately 0.02 Hz. Therefore, the frequencies associated with the dominant periodic component 404 (see Figure 4B) lie between the cutoff frequencies 502 and 506 of the bandpass filter shown in Figures 5A and 5B.

[0055] In the example shown in Figures 5A and 5B, the cutoff frequency 502 associated with the low-pass filter section 500 is closer to the dominant periodic component 404 than the cutoff frequency 506 of the high-pass filter section 504 (for example, in this example, the difference between the cutoff frequency 502 and the dominant periodic component 404 is 0.01 Hz). That is, the band-pass filter is configured to filter out high-frequency components having frequencies greater than 0.01 Hz above the frequency associated with the dominant periodic component 404. The reason such a configuration is considered beneficial is that higher frequency components are closer to the dominant frequency component 404 and tend to reduce the accuracy of the modulation phase Φ described herein more significantly than lower frequency components. The cutoff frequencies 502 and 506 are configurable parameters and can be selected based on the desired speeds of the first and second edge rollers 132a and 132b. In the embodiment, the cutoff frequencies 502, 506 are determined by analyzing the filtered torque sum signal to determine values ​​for the cutoff frequencies 502, 506 that produce consistent results for determining the modulation phase Φ as described herein. The specific cutoff frequencies 502, 506 used may also be different, and their relationship to the dominant periodic component 404 may differ from those shown in Figures 5A-5B.

[0056] Referring to Figure 1, in embodiments, filtering the torque signals generated by one or more drive units 137 using a bandpass filter, such as the bandpass filter described herein with reference to Figures 5A-5B, may introduce a phase shift into the torque sum signal. Such a filter-induced phase shift may degrade the accuracy of the modulation phase Φ generated using the methods described herein. Therefore, in embodiments, the memory 152 may include filter compensation logic configured to phase shift the filtered torque sum signal by the amount necessary to compensate for the filter-induced phase shift associated with the bandpass filter. In embodiments, a bandpass filter is used to filter multiple torque sum signals containing multiple different dominant frequency components (e.g., different frequencies), and established filtering theory algebraic expressions are used to determine the phase shift of each torque sum signal. Using such relationships based on the frequency associated with the dominant periodic component 404 (see Figure 4B), the phase shift used to process the filtered torque signal can be calculated.

[0057] Figure 6A shows a time-series plot 602 of the raw torque sum signal generated by one or more drive units 137 (see Figure 1A). Figure 6B shows a time-series plot 604 of the filtered torque sum signal, which represents the raw torque sum signal shown in Figure 6A filtered by the bandpass filter described herein with respect to Figures 5A and 5B, and then phase-shifted to compensate for the filter-induced phase shift. As shown, the filtered torque sum signal is a generally smooth periodic signal with a period associated with the dominant periodic component 404 (see Figure 4B). As shown in Figure 6B, the amplitude of the filtered signal changes periodically at a frequency lower than the frequency associated with the dominant periodic component 404. While we do not wish to be bound by theory, such periodic fluctuations in amplitude are thought to be a result of the mechanical interaction between the first and second edge rollers 132a, 132b. The filtered torque sum signal shown in Figure 6B provides a baseline for establishing a time delay with the electric roll position signal generated via one or more drive units 137.

[0058] Figure 7 shows a time-series plot 680 including a raw torque sum signal 700 generated by one or more drive units 137, a filtered torque sum signal 702, an electric roll position signal 704 generated via one or more drive units 137, and an overlay of time delays 706 related to the corresponding portions of the filtered torque sum signal 702 and the electric roll position signal 704. As shown in Figure 7, the electric roll position signal 704 includes a sawtooth function in which the amplitude of the signal changes from a minimum value when the rotational position of one or more drive units 137 is 0° to a maximum value when the rotational position of one or more drive units 137 is slightly less than 360°. The transition between the maximum and minimum values ​​(shown as vertical lines in the electric roll position signal 704) represents the point in time when one of the first and second edge rollers 132a, 132b (see Figure 1) has completed its rotation.

[0059] Referring to Figures 1 and 7, the raw torque sum signal 700 can represent the sum of torque signals generated by one or more drive units 137 during the rotation of the first and second edge rollers 132a and 132b. For example, the raw torque sum signal 700 can represent the sum of a first torque signal generated by the first drive unit rotating the first edge roller 132a around the first rotation axis 140a and a second torque signal generated by the second drive unit rotating the second edge roller 132b around the second rotation axis 140b. The filtered torque sum signal 702 can be generated by processing the raw torque sum signal 700 using a bandpass filter, such as the bandpass filter described herein with reference to Figures 5A and 5B. Both the raw torque sum signal 700 and the filtered torque sum signal 702 are normalized with respect to a reference value.

[0060] As shown in Figure 7, the time delay 706 between the filtered torque sum signal 702 and the electric roll position signal 704 can be determined by calculating the difference between a first time point in time when one of the first and second edge rollers 132a, 132b completes its rotation (or rotation period) and a second time point in time when the filtered torque sum signal 702 begins its fluctuation period. In the embodiment, the fluctuation period begins when the filtered torque sum signal 702 includes the average value of the periodic oscillation of the amplitude of the filtered torque sum signal 702. In the embodiment, the value of the time delay 706 can be converted to the modulation phase Φ described herein by multiplying the value of the time delay 706 by a dominant frequency of interest, as shown by component 404 in Figure 4B.

[0061] In the embodiment, the value of the time delay 706 is calculated for multiple consecutive periods of each of the electric roll position signal 704 and the filtered torque sum signal 702, and the average of these values ​​is used to calculate the modulation phase Φ described herein. Averaging multiple values ​​of the time delay 706 over multiple cycles benefits in obtaining a more accurate estimate of the time delay, and therefore a calculation of the modulation phase Φ that reduces thickness flapping more significantly than in embodiments that rely on the calculation of a single time delay 706 to calculate the modulation phase Φ. In the embodiment, the controller 150 automatically calculates the value of the time delay 706 based on the measurement time associated with the filtered torque sum signal 702 and the electric roll position signal 704, which have specific values ​​(for example, when the filtered torque sum signal 702 includes an average or median value, and when the electric roll position signal 704 includes a maximum or minimum value).

[0062] Figure 8 is a flowchart of method 800 for modulating the rotational speed of the edge rollers of a glass molding apparatus using a torque sum signal. Method 800 can be performed by the controller 150 of the apparatus 10 described herein with respect to Figures 1 to 3. Accordingly, various components shown in Figures 1 to 3 will be referenced to aid in the explanation of method 800. As a result of performing method 800, the glass ribbon 12 can have a more uniform thickness 166 than when the first and second edge roller assemblies 130a, 130b are operated at a constant rotational speed. Here, we refer to the first edge roller assembly 130a, but method 800 can also be performed to control the rotation of the edge rollers of the second edge roller assembly 130b or any other edge roller assembly in the apparatus 10.

[0063] In block 802, the controller 150 receives torque signals associated with the edge rollers located on both sides of the glass ribbon 12. For example, the controller 150 may receive torque signals generated by one or more drive units 137 used to rotate the first and second edge rollers 132a, 132b of the first edge roller assembly 130a described herein. In embodiments, the controller 150 may receive a single torque signal associated with a particular pair of edge rollers. For example, in embodiments, both the first edge roller 132a and the second edge roller 132b can be rotated using a single drive unit such that the controller 150 receives a single torque signal (representing a torque sum signal). In such embodiments, the controller can generate a torque sum signal by receiving torque signals from a single drive unit.

[0064] In block 804, the controller 150 combines the torque signals received in block 802 into a torque sum signal. For example, in embodiments where separate drive units (e.g., separate motors) are used to rotate the first and second edge rollers 132a and 132b, each drive unit can generate a torque signal. The controller 150 can receive each individual torque signal and combine them into a torque sum signal. The torque sum signal can be filtered using a bandpass filter, as described herein with reference to Figures 5A and 5B, to remove frequency components outside a predetermined frequency range related to the target rotational speed of the first and second edge rollers 132a and 132b (e.g., the target rotational speed may be based on a desired stretching speed of the glass ribbon 12). After filtering, the filtered torque sum signal can be phase-shifted based on a predetermined filter-inductive phase shift related to the bandpass filter. Subsequently, the modulation phase Φ can be determined using this filtered and phase-shifted torque sum signal, as described herein.

[0065] In block 806, the controller 150 modulates the first and second rotational speeds ω1 and ω2 of the first and second edge rollers 132a and 132b in a time-dependent manner to counteract the change in the torque sum signal. As described herein, time intervals in which the torque sum signal increases with time can indicate a decrease in the variable separation distance 144 (see Figure 3A). During such time intervals, the controller 150 can increase the rotational speeds of the first and second edge rollers 132a and 132b (e.g., increase the first and second rotational speeds ω1 and ω2) to maintain the speed at which the glass passes through the first edge roller assembly 130a. Time intervals in which the torque sum signal decreases with time can indicate an increase in the variable separation distance (see Figure 3B). During such time intervals, the controller 150 can decrease the rotational speeds of the first and second edge rollers 132a and 132b (e.g., decrease the first and second rotational speeds ω1 and ω2). In the embodiment, the controller 150 can supply control signals to increase or decrease the first and second rotational speeds ω1 and ω2 by a predetermined amount (for example, stored in a lookup table) based on the trend of the torque sum signal. For example, if the torque sum signal increases by a threshold amplitude over a predetermined period (for example, about 1 / 4 of the rotation period of the first and second edge rollers 132a and 132b), the controller 150 can increase the first and second rotational speeds ω1 and ω2 until a decrease in the amplitude of the torque sum signal is detected. The degree of modulation of the first and second rotational speeds ω1 and ω2 can change in proportion to the degree of increase or decrease of the torque sum signal. Modulating the first and second rotational speeds ω1 and ω2 can reduce the influence of the variable separation distance 144 (see Figure 3A) on the thickness of the glass ribbon over the rotation period of the first and second edge rollers 132a and 132b. This modulation reduces the effect of the first and second edge rollers 132a and 132b not being perfectly circular.

[0066] In this embodiment, the controller 150 periodically modulates the first and second rotational speeds ω1 and ω2. In this embodiment, when the controller 150 first receives the torque signal in block 802, the first and second edge rollers 132a and 132b set to the nominal target angular velocity ω N They can rotate at a nominal target angular velocity ω1, ω2. By periodically modulating the first and second rotational speeds ω1, ω2, the first and second edge rollers 132a, 132b can rotate at a speed dependent on their angular position (measured, for example, by an electric roll position signal generated by one or more drive units 137 described herein). For example, in an embodiment, the controller 150 rotates one or more drive units 137 at an angular velocity that changes as a function of the angular position of the first and second edge rollers 132a, 132b. The controller identifies the angular positions of the first and second edge rollers 132a, 132b where the torque sum signal is increasing and decreasing from the average value, and modulates the first and second rotational speeds ω1, ω2 to the nominal target angular velocity ω N It can be raised or lowered above or below that level.

[0067] In an embodiment, the controller 150 periodically modulates the first and second rotational speeds ω1 and ω2 according to equation 1 herein. In such an embodiment, the controller 150 can generate the modulation amplitude A and modulation phase Φ parameter values ​​described herein by performing the method 900 shown in Figure 9. In block 902, the controller 150 can determine the modulation phase Φ of equation 1 based on the time delay between the electric roll position signal and the torque sum signal. For example, the controller 150 can calculate the time delay using a filtered and phase-shifted torque sum signal and the electric roll position signal generated via an encoder associated with one or more drive units 137, using a procedure similar to that described above with respect to Figure 7 (for example, by determining the time difference between the point in time when the electric roll position signal indicates the start of the rotation period and the point in time when the torque sum signal is the mean or median). In an embodiment, the controller 150 may include verification logic to verify the modulation phase Φ calculated as described herein. For example, the controller can use the estimated modulation phase Φ to phase-shift a previously measured torque sum signal using the estimated modulation phase Φ. The controller 150 can compare the phase-shifted torque sum signal with the electric roll position signal to determine whether the estimated modulation phase Φ meets the tolerance. If it does not meet the tolerance, the modulation phase Φ can be re-estimated by measuring further cycles of the torque sum signal and the electric roll position signal.

[0068] In block 904, the controller 150 can determine the modulation amplitude A in equation 1. The modulation amplitude A can be determined using a trial-and-error method of gradually increasing the modulation amplitude A. While the modulation amplitude A is kept constant, the controller 150 can monitor the thickness 166 (for example, using measurements from the thickness sensor 160). For example, the controller 150 can continuously monitor the thickness 166 and determine the thickness range of the glass ribbon 12 over a predetermined measurement period (e.g., 5 seconds, 10 seconds, 30 seconds, 1 minute, 3 minutes, 5 minutes, 10 minutes, 30 minutes, 1 hour, 2 hours). This measured thickness range can be compared to a previously measured value associated with the previous modulation amplitude A. If a decrease in the thickness range is measured, the controller 150 can increase the modulation amplitude A by a predetermined increment (e.g., 0.1, 0.2, 0.3, 0.4) and determine whether the increase in modulation amplitude A further decreases the thickness range. If an increase in the thickness range is observed at a particular modulation amplitude A value, the controller 150 can reduce the modulation amplitude A to a previous value (e.g., the last value of modulation amplitude A at which a decrease in the thickness range was observed). The controller 150 can gradually increase the modulation amplitude A using a fixed or variable increment until no further decrease in thickness variation (or range) is observed. The increment used by the controller 150 to update the modulation amplitude A can vary depending on the degree of decrease in the observed thickness variation. [Examples]

[0069] The embodiments described herein are further clarified by the following examples. Figure 10 shows plot 1000 of experimental results of modulating the rotational speed of an edge roller using equation 1 herein. These experimental results were achieved during the manufacture of Corning Lotus® NXT glass. The modulation phase Φ was determined using the method described herein with respect to Figure 7. Line 1002 in plot 1000 represents the moving window range of the measured glass ribbon thickness. Vertical lines 1006, 1008, 1010, 1012, 1014, 1016, 1018 and 1020 represent the points in time when the modulation amplitude A increased according to method 900 described herein with respect to Figure 9.

[0070] During the period to the left of vertical line 1006, the rotational speed of the edge roller was not modulated. As shown in the figure, the thickness movement window range was greater than 4 micrometers (μm) for substantially the entire duration of this period. Between vertical lines 1006 and 1008, the modulation amplitude A was set to 0.3. As a result, the thickness movement window range was less than 4 μm within this time window. Therefore, when the modulation amplitude A was increased to 0.5 at vertical line 1008, the thickness movement window range decreased further. This decrease in the thickness movement window range continued to be observed until the modulation amplitude was set to 0.9 after vertical line 1012. Between vertical lines 0.9 and 1.1, the thickness movement window range was measured to be less than 3.0 μm, a significant improvement over the unmodulated case. When the modulation amplitude A was increased to 1.1 at vertical line 1014, the thickness movement window range increased compared to the thickness movement window range when the modulation amplitude A was 0.9. Furthermore, when the modulation amplitude A was increased to 1.3 at vertical line 1016, the thickness movement window range increased further. Consequently, when the modulation amplitude A was decreased to 1.1 at vertical line 1018, a decrease in the thickness movement window range was observed again compared to when the modulation amplitude A was 1.3. Therefore, when the modulation amplitude A was further decreased to 0.9, the initial minimum thickness movement window range was observed. This embodiment demonstrates how determining the modulation amplitude A can significantly reduce thickness variations in the glass ribbon.

[0071] The operation method of the drive unit for the edge rollers of the glass manufacturing apparatus has been illustrated and explained above. It has been shown that when the rotational speed of the edge rollers is modulated in a time-dependent manner to cancel out the fluctuations observed in the torque sum signal, the thickness flapping caused by edge rollers with different cross-sectional shapes is substantially reduced. The torque sum signal functions usefully as a substitute for the variable separation distance between edge rollers caused by the different cross-sectional shapes of the edge rollers, and indicates the period during which variations in the thickness of the glass ribbon can be reduced and a glass sheet of more uniform thickness can be obtained by increasing or decreasing the rotational speed of the edge rollers above the nominal target speed to maintain the flow of glass through the edge rollers.

[0072] Those skilled in the art will see that various modifications and variations can be made to the embodiments described herein without departing from the spirit and scope of the claimed subject matter. Accordingly, this specification is intended to cover modifications and variations to the various embodiments described herein, provided that such modifications and variations fall within the scope of the appended claims and their equivalents. [Explanation of symbols]

[0073] 12 Glass Ribbons 17. Molten glass 60 Molded containers 62 Molded Wedge 64a End of molded wedge 66a, 66b Molding surface portion of the molded wedge 70 Base 72 Stretched surface 110b Second main surface of the glass ribbon 130a First edge roller assembly 132 First Edge Roller Pair 132a First edge roller 132b Second edge roller 136 First shaft 137 Drive Unit 138 Second shaft 140a First rotation axis 140b Second axis of rotation 160 Thickness Sensor 166 Glass ribbon thickness 170 Measurement position

Claims

1. A method for manufacturing glass, Forming a glass ribbon including a first surface and a second surface from a predetermined amount of molten material, The first surface is brought into contact with the first edge roller, and the second surface is brought into contact with the second edge roller, The first edge roller is rotated at a first rotational speed, and the second edge roller is rotated at a second rotational speed, To generate a first torque signal representing the torque applied to the first edge roller, and a second torque signal representing the second torque applied to the second edge roller, To generate a torque sum signal of the first torque signal and the second torque signal, The first rotational speed and the second rotational speed are modulated in a time-dependent manner to cancel out fluctuations in the torque sum signal, A method characterized by including the following.

2. The time-dependent modulation of the first and second rotational speeds is expressed by the following equation: oh T =A*sin(θ 1,2 +Φ)+ω N 、 Using the target rotation speed ω T This includes periodically modulating the first rotational speed and the second rotational speed by calculating the following: In the equation, A is the modulation amplitude, and Θ 1、2 ω is the angular position of the first edge roller or the second edge roller, Φ is the modulation phase, and ω N is the nominal rotational speed of the first edge roller and the second edge roller. The method according to claim 1.

3. The time delay between the roll position signal representing the angular position and the torque sum signal is determined. Convert the aforementioned time delay into a phase angle. This further includes determining the modulation phase by The method according to claim 2.

4. Before determining the modulation phase, the process further includes filtering the torque sum signal using a bandpass filter having an upper cutoff frequency and a lower cutoff frequency, ω N This is the frequency between the upper limit cutoff frequency and the lower limit cutoff frequency. The method according to claim 3.

5. To sense the thickness of the glass ribbon downstream of the first edge roller and the second edge roller, The modulation amplitude A is determined based on the thickness of the glass ribbon, The method according to claim 2, further comprising:

6. Determining the modulation amplitude A means that The first rotational speed and the second rotational speed are periodically modulated using the first value of the modulation amplitude A. Based on the result of the first value, it is determined whether the thickness variation of the glass ribbon has decreased, If the first value results in a decrease in the thickness variation of the glass ribbon, the modulation amplitude A is increased until the decrease in the thickness variation is no longer observed. The method according to claim 5, including the method described in claim 5.

7. Modulating the first rotational speed and the second rotational speed in such a way as to cancel out the change in the torque sum signal is: During the period in which the separation distance is increasing, at least one of the first rotational speed and the second rotational speed is reduced. During the period in which the separation distance is decreasing, increase at least one of the first rotational speed and the second rotational speed. Includes, The method according to claim 1, wherein the separation distance is the distance between the first edge roller and the second edge roller.

8. Modulating the first and second rotational speeds in such a way as to cancel out the change in the torque sum signal reduces the range of the glass ribbon's moving window thickness achieved when the first and second rotational speeds are not modulated. The method according to claim 1.

9. A method for manufacturing glass, The steps include forming a glass ribbon including a first surface and a second surface from a predetermined amount of molten material, A step of bringing the first surface into contact with a first edge roller and the second surface into contact with a second edge roller, wherein the first edge roller and the second edge roller have different cross-sectional shapes such that the separation distance between the first edge roller and the second edge roller changes periodically depending on the rotational speed of the first edge roller and the second edge roller. The steps include driving the first edge roller and the second edge roller at a first rotational speed and a second rotational speed, respectively, A step of generating a torque sum signal representing the total torque applied to the first edge roller and the second edge roller, The steps include determining a time delay between the torque sum signal and an electric roll position signal representing one or both of the first and second rotational positions, The steps include updating the first rotation speed and the second rotation speed based on the time delay, the first rotation position, and the second rotation position, A method characterized by including the following.

10. A glass manufacturing apparatus, A forming body configured to form a glass ribbon from a predetermined amount of molten material, comprising a forming body that defines an extension path extending from the forming body, on which the glass ribbon can be formed, An edge roll assembly including an edge roller pair, which includes a first edge roller having a first cross-sectional shape and a second edge roller having a second cross-sectional shape, arranged on both sides of the extension path, wherein the first cross-sectional shape differs from the second cross-sectional shape so as to separate them from each other by a separation distance that changes according to the rotational speed of the first edge roller and the second edge roller, One or more drive units are mechanically coupled to the first edge roller and the second edge roller, and are configured to rotate the first edge roller around a first rotation axis at a first rotational speed and the second edge roller around a second rotation axis at a second rotational speed, and are further configured to generate a first torque signal representing a first torque applied to the first edge roller and a second torque signal representing a second torque applied to the second edge roller. The drive unit is connected to one or more drive units in a communicative manner, A torque sum signal is generated from the first torque signal and the second torque signal. Using the torque sum signal, the first rotational speed and the second rotational speed are modulated such that they are inversely proportional to the variable separation distance. A controller capable of operating in this manner, A glass manufacturing apparatus characterized by being equipped with the following features.

11. The system further comprises thickness sensors configured to sense the thickness of the glass ribbon downstream of the first edge roller and the second edge roller, and the controller is operable to modulate the first rotational speed and the second rotational speed based on the thickness of the glass ribbon. The glass manufacturing apparatus according to claim 10.

12. The controller is operable to periodically modulate the first rotational speed and the second rotational speed using a modulation phase calculated based on the time delay between the torque sum signal and the electric roll position signal generated by the one or more drive units, wherein the electric roll position signal represents the rotational position of at least one of the first edge roller or the second edge roller. The glass manufacturing apparatus according to claim 11.

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