JP7530959B2 - Laser devitrification material removal system and method - Google Patents

Description

Related Applications

This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Patent Application No. 62/877,025, filed July 22, 2019, the entire contents of which are incorporated herein by reference.

The present disclosure relates to the manufacture of glass sheets, and more particularly to an apparatus and method for inhibiting the accumulation of devitrified glass during glass sheet manufacture.

Glass sheets are used in a variety of applications. For example, they may be used in glass display panels for mobile devices, laptops, tablets, computer monitors, television displays, and the like. Glass sheets may be manufactured by a fusion downdraw process in which molten glass is pulled over a glass forming apparatus to create a glass sheet. In some instances, the glass forming apparatus includes an edge director that directs the molten glass toward the edge of the glass sheet being formed. However, devitrification of the molten glass can often occur on the edge director. As used herein, devitrification refers to the crystallization of an originally amorphous glass. The crystallized material is referred to herein as devitrifying material and/or devitrifying material. For example, FIG. 12 illustrates accumulated devitrifying material 102 on an edge director 104.

Accumulated devitrification material on edge directors can cause molten glass to fall onto unwanted parts of the glass forming equipment. Accumulated devitrification material on edge directors can also cause hollow beads to form in the molten glass, which can cause cracks in the formed glass. Accumulated devitrification material can also cause pulling of narrower glass ribbons during the glass forming process, which is often an undesirable effect. Thus, opportunities exist for improving glass sheet production.

Features disclosed herein allow for the removal or prevention of devitrification materials on glass forming devices, such as edge directors. Devitrification materials may include, for example, cristobalite, mullite, and/or tridymite crystals.

In some examples, the devitrification material suppression system may direct a laser (e.g., a laser beam) to heat a particular area of the glass forming apparatus that has already accumulated or is prone to accumulate a significant amount of devitrification material. The devitrification material suppression system may include a mirror system that can be controlled to direct the laser to a particular location for a determined amount of time and deliver a determined amount of energy. The energy provided by the laser allows the crystal to be heated, for example, above the glass liquidus temperature (i.e., the lowest temperature at which the glass is completely liquid).

In some examples, an optical fiber coupled to a laser generator (also known as a laser source or laser), such as a diode laser generator, _CO2 laser generator, or fiber laser generator, can be controlled to heat the area of the glass forming device where the devitrified material is formed, such as an edge director. The laser passes through the optical fiber to an optical collimator where it is collimated. In some examples, the collimator can return control information to a monitoring device for laser beam control.

In some examples, a beam shaping element, such as a diffractive optical element (DOE) or a spatial light modulator (SLM), may be used by the devitrification material suppression system. The beam shaping element shapes (e.g., shapes) the incident laser beam so that the laser beam pattern projected onto the accumulated or expected devitrification material has a predetermined energy distribution. The devitrification material suppression system may tailor the spatial distribution of energy provided by the laser to meet the application requirements (e.g., uniform energy across the accumulated devitrification material, energy gradients across the accumulated devitrification material that reflect the contour and temperature characteristics of the edge director, etc.).

In some examples, the devitrification material suppression system can control one or more tightly focused high power laser beams to remove (e.g., vaporize) accumulated crystals and remove large crystal growths from portions of the glass forming apparatus, such as edge directors. The energy from the laser beam heats the devitrification material and physically removes it from the glass forming apparatus until all (or most) of it is removed.

The present disclosure describes, in one embodiment, an apparatus including a memory device storing instructions and a controller having at least one processor and configured to execute the instructions, which, when executed, cause the controller to preselect a portion of a glass forming apparatus, configure a reflector to reflect a laser beam from a laser generator to the preselected portion of the glass forming apparatus, and operate the laser generator to generate the laser beam and heat the preselected portion of the glass forming apparatus to inhibit devitrification.

In another embodiment, the present disclosure describes an apparatus including a laser generator operable to generate a laser beam, a reflector configured to reflect the laser beam from the laser generator to a glass forming apparatus, and a controller communicatively coupled to the laser generator and the reflector. The controller may be configured to preselect a portion of the glass forming apparatus, configure the reflector to reflect the laser beam from the laser generator to the preselected portion of the glass forming apparatus, and operate the laser generator to generate the laser beam and heat the preselected portion of the glass forming apparatus for devitrification inhibition.

In yet another embodiment, the present disclosure describes a method for removing devitrified material from a glass forming apparatus, the method including the steps of preselecting a portion of the glass forming apparatus, configuring a reflector to reflect a laser beam from a laser generator to the preselected portion of the glass forming apparatus, and operating the laser generator to generate the laser beam and heat the preselected portion of the glass forming apparatus.

In another embodiment, the present disclosure describes an apparatus that includes a laser generator operable to generate a laser beam, a reflector configured to reflect the laser beam from the laser generator to a glass forming apparatus, and a controller communicatively coupled to the laser generator and the reflector. The controller may be configured to preselect a portion of the glass forming apparatus, configure the reflector to reflect the laser beam from the laser generator to the preselected portion of the glass forming apparatus, and operate the laser generator to generate the laser beam. A devitrified material is located on the glass forming apparatus, molten glass is located along a path of the laser beam between the preselected portion of the glass forming apparatus and the laser generator, and the laser beam heats the molten glass.

In yet another embodiment, the present disclosure describes a method for removing devitrified material from a glass forming apparatus. The method includes preselecting a portion of the glass forming apparatus, configuring a reflector to reflect a laser beam from a laser generator onto the preselected portion of the glass forming apparatus, and activating the laser generator to generate the laser beam. A devitrified material is located on the glass forming apparatus, molten glass is located along a path of the laser beam between the preselected portion of the glass forming apparatus and the laser generator, and the laser beam heats the molten glass.

The above summary and the following detailed description of example embodiments may be read in conjunction with the accompanying drawings, which illustrate some of the embodiments described herein. As explained further below, the claims are not limited to the example embodiments. For clarity and ease of reading, the drawings may omit the illustration of certain features.
1 illustrates a schematic diagram of an exemplary glass forming apparatus having a devitrification material suppression system according to some examples. 2A-2C are schematic diagrams illustrating portions of the exemplary glass forming apparatus of FIG. 1 according to some examples. FIG. 1 is a block diagram of an exemplary devitrification material mitigation system according to some examples. FIG. 1 is a block diagram of an exemplary devitrification material mitigation system according to some examples. FIG. 1 is a block diagram of an exemplary devitrification material mitigation system according to some examples. FIG. 1 is a block diagram of an exemplary devitrification material mitigation system according to some examples. 1 illustrates a thermal model of a laser heated glass layer according to some examples. 1 illustrates an infrared transmission spectrum of cristobalite that may be used to direct a laser with a devitrification material suppression system according to some examples. 1 illustrates the infrared transmission spectrum of tridymite that may be used to direct a laser with a devitrification material suppression system according to some examples. 1 illustrates transmission graphs of various devitrifying materials that may be used to direct a laser with a devitrifying material suppression system according to some examples. 1 illustrates a devitrification material mitigation system including sensor feedback according to some examples. 1 illustrates an exemplary method that may be implemented by a devitrification material mitigation system according to some examples. 1 illustrates the accumulation of devitrified material on a conventional glass forming apparatus.

This application discloses exemplary embodiments. The disclosure is not limited to these exemplary embodiments. Accordingly, many embodiments of the claims will vary from the exemplary embodiments. Various modifications may be made to the claims without departing from the spirit and scope of the disclosure. The claims are intended to include such modified embodiments.

At times, this disclosure uses directional terms (e.g., front, back, top, bottom, left, right, etc.) to give the reader context when viewing the figures. However, the claims are not limited to the orientation shown in the figures. Any absolute term (e.g., high, low, etc.) may be understood to disclose the corresponding relative term (e.g., higher, lower, etc.).

This disclosure provides an apparatus and method for removing devitrification material buildup on an edge director by heating the area of the edge director where the devitrification material accumulates with a laser to remove (e.g., melt) the accumulated material. In some examples, the apparatus and method may be used to close hollow beads that may result from failure of molten glass to properly fuse beneath the edge director. As known in the art, "bead" specifically refers to the edge region of a glass ribbon formed during manufacture by a fusion draw process.

In some examples, a laser wavelength is determined for the laser to be directed at the devitrified material to allow for effective removal of the devitrified material. In some examples, the laser wavelength (or wavelengths) can be selected such that the laser penetrates the molten glass flowing over the edge director and is significantly absorbed by the devitrified material, raising the temperature of the devitrified material to its melting point (or in some examples, at least its softening point). The molten glass flow can carry the devitrified material away from the edge director.

In some examples, the molten glass is heated directly with a laser, which can heat the accumulated devitrification material through conduction and radiation effects. In some examples, the molten glass can be rerouted away from the edge director (e.g., by tilting the forming device) to expose the devitrification material, which can be heated directly with a laser until it pools away from the edge director. In yet other examples, a platinum edge director can be heated using a laser instead of the devitrification material. The platinum edge director can conduct heat to the area where the devitrification material contacts the edge director. A sufficient increase in temperature causes the devitrification material to melt at the interface between the platinum and the devitrification material, freeing it from its attachment to the platinum edge director.

In some examples, the directed laser energy can be used to remove (e.g., melt or vaporize) devitrified material crystal growth on the edge director. The laser pulse energy, beam width, power level, and/or wavelength can be adjusted to match the material absorption and vaporization characteristics of the devitrified material crystal. These examples are useful for applications requiring significant crystal removal (e.g., chipping away at the devitrified material crystal until only a thin layer remains, at which point one of the above examples can be used to thermally remove the remaining material from the edge director).

In some examples, a control system may be used to position a mirror to reflect the laser beam to a location of interest, such as an edge director having accumulated devitrification material. The control system may include a one-dimensional or two-dimensional galvanometer driven mirror set, a rotating polygon, an acousto-optic modulator, a voice coil driven mirror set, a servo or stepper motor set, or a combination thereof to position the mirror. In some examples, a two-dimensional galvanometer driven mirror set may be used to scan the laser beam across the devitrification material while a thermal imaging camera may be used as feedback to precisely control the delivery of laser energy. The position and energy may be controlled so that neither the forming device nor the edge director may inadvertently overheat, causing thermo-mechanical stresses that may crack or deform the part. In some examples, an imaging camera may also be used to provide mirror position feedback during operation.

In some examples, the laser may be raster scanned (e.g., at a rate between 0.001 Hz and 10,000 Hz) across the edge director in a sustained mode to periodically clean the edge director in a preset pattern. In some examples, the formation of devitrification material may be prevented by periodically heating the edge director, such as once a month, once a week, or at any other interval. The control system may configure mirrors to redirect the laser beam across one or more edge directors in a predetermined pattern. In some examples, the devitrification material may be uniformly heated based on a thermal image of the devitrification material provided by a thermal imaging camera. The control system may also program the laser to deliver a predetermined energy to the edge director to remove or prevent accumulated devitrification material.

Referring to FIG. 1, the glass forming apparatus 20 includes a forming wedge 22 having an open channel 24 with longitudinal sides defined by walls 25 and 26. The walls 25 and 26 terminate at their upper portions in opposed, longitudinally extending overflow weirs 27 and 28, respectively. The overflow weirs 27 and 28 are integral with a pair of opposed, generally vertical forming surfaces 30, which are integral with a pair of opposed, downwardly inclined converging forming surfaces 32. The pair of downwardly inclined converging surfaces 32 terminate in generally horizontal lower apexes that form the root 34 of the forming wedge 22. Each downwardly inclined converging surface 32 may include a pair of edge directors 50. Only one downwardly inclined converging surface 32 and corresponding pair of edge directors are shown in FIG. 1.

Molten glass is delivered into the open channel 24 through a delivery passage 38 in fluid communication with the open channel 24. A pair of dams 40 are provided adjacent the ends of the open channel 24 above the overflow weirs 27 and 28 to direct the overflow of the free surface 42 of the molten glass over the overflow weirs 27 and 28 as separate streams of molten glass. Only the pair of dams 40 located at the ends of the open channel 24 adjacent the delivery passage 38 are shown in FIG. 1. The separate streams of molten glass flow over a pair of opposing generally vertical forming surfaces 30 and a pair of opposing downwardly inclined converging forming surfaces 32 down to the root 34 where the separate streams of molten glass, shown in dashed lines in FIG. 1, converge to form a glass ribbon 44. Each pair of edge directors 50 keeps the molten glass along the downwardly inclined converging forming surfaces 32 until the molten glass reaches the root 34.

A pulling roll 46 is positioned downstream of the root 34 of the forming wedge 22 and engages opposite side edges 48 of the glass ribbon 44 to apply tension to the glass ribbon 44. The pulling roll 46 may be positioned sufficiently below the root 34 such that the thickness of the glass ribbon 44 is substantially determined at that location. As the glass ribbon is forming at the root 34, the pulling roll 46 may pull the glass ribbon 44 downward at a predetermined rate that establishes the thickness of the glass ribbon.

1 also illustrates an exemplary devitrification material suppression system 10 that may include a laser generator 12 configured to generate and emit a laser beam 13. In one embodiment, the laser beam 13 increases the temperature of the molten glass flowing over the location of the devitrification material, which in turn raises the temperature of the devitrification material to near or above the melting point of the devitrification material, such that the viscous flow of the molten glass may dislodge the devitrification material from the forming device 20 and/or the edge director 50. As shown in FIG. 1, the laser beam 13 may be directed by the laser generator 12 to either of the pair of edge directors 50, for example, via a reflector 14.

In one embodiment, the reflecting device 14 may include a reflective surface 15 configured to receive and reflect the emitted laser beam 13 generated by the laser generator 12 to at least a predetermined area of the edge director 50. The reflecting device 14 may be, for example, a mirror configured to redirect the laser beam from the laser generator 12. Thus, the reflecting device 14 may function as a beam steering and/or scanning device. In FIG. 1, the laser beam 13 is shown as being directed by the reflecting device 14 as a reflected laser beam 17 to a plurality of preselected portions of the edge director 50.

In one example, the reflective surface 15 may comprise a gold-coated mirror, although in other examples other types of mirrors may be used. Gold-coated mirrors may be desirable in some applications to provide consistent and superior reflectivity, for example with infrared lasers. Also, the reflectivity of gold-coated mirrors is substantially independent of the angle of incidence of the laser beam 13, making gold-coated mirrors particularly useful as scanning or laser beam steering devices.

1 may also include an adjustment mechanism 16 configured to adjust the attitude of the reflecting surface 15 of the reflecting device 14 with respect to receipt of the laser beam 13 and the position of the preselected portion of the edge director 50. For example, the reflecting device 14 may rotate or tilt the reflecting surface 15 to direct the laser beam 13 as a reflected laser beam 17 toward the preselected portion of the edge director 50.

According to one example, the adjustment mechanism 16 may include a galvanometer in operative association with the reflective surface 15, which may rotate the reflective surface 15 about an axis relative to the glass ribbon 44. For example, the reflective surface 15 may be mounted on a rotatable shaft 18 that is driven by a galvanometer motor and rotated about an axis 18a as indicated by double-headed arrow 19.

2 shows another view of the reflector 14 directing the laser beam 13 from the laser generator 12 to the edge director 50. Although the reflector 14 is shown directing the laser beam 13 to only one edge director 50, the reflector 14 may move the reflective surface 15 to direct the laser beam 13 to the other edge director 50. In some examples, the reflector 14 may alternately direct the laser beam 13 to a portion of one edge director 50 and a portion of the other edge director 50.

In some examples, the devitrification material suppression system 10 may heat the devitrification material on the edge director 50 to at least the liquidus temperature of the devitrification material by directing the laser beam 13 to the edge director 50 and applying energy to the devitrification material formed on the edge director 50. As a result, the devitrification material formed on the edge director 50 may melt or flake off from the edge director 50. In some examples, the devitrification material suppression system 10 routinely (e.g., periodically or occasionally) directs the laser beam 13 to the edge director 50 regardless of whether devitrification material is formed on the edge director 50. In this manner, the energy from the laser beam 13 causes the edge director 50 to maintain a minimum temperature such that devitrification material is not or is not likely to form on the edge director 50.

In some examples, the devitrification material suppression system 10 may be operated continuously. In some examples, the devitrification material suppression system 10 may be operated during scheduled maintenance periods.

In some examples, the pulse energy, beam width, power level, and/or wavelength of laser beam 13 may be selected such that the energy from laser beam 13 sufficiently heats the accumulated devitrification material without inadvertently overheating other components of devitrification material suppression system 10. For example, laser generator 12 may use a diode laser (e.g., a diode laser emitting a laser beam with a wavelength of 0.976 μm). In some examples, laser generator 12 uses a _CO2 laser.

In some examples, the power level of the laser beam 13 can be selected such that energy from the laser beam 13 heats at least one of the forming apparatus 20, the edge director 50, the molten glass on and/or adjacent to the forming apparatus 20 and/or the edge director 50, and the devitrified material on and/or adjacent to the forming apparatus 20 and/or the edge director 50 or in or around the molten glass.

3 shows a portion of a representative devitrification material suppression system 10, with solid arrowed lines representing laser beams (e.g., laser beam 13, reflected laser beam 17) and dashed lines representing electrical control signals. In this example, the devitrification material suppression system 10 may include a laser power controller 55 and a control computer 52. Each of the laser power controller 55 and the control computer 52 may include one or more processors, one or more field programmable gate arrays (FPGAs), one or more application specific integrated circuits (ASICs), one or more state machines, digital circuits, or any other suitable circuitry. In some embodiments, one or more of the laser power controller 55 and the control computer 52 may be implemented in any suitable hardware or hardware and software (e.g., one or more processors executing instructions stored in memory). For example, a non-transitory computer-readable medium, such as a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), a flash memory, a removable disk, a CD-ROM, any non-volatile memory, or any other suitable memory, may store instructions that can be retrieved and executed by the laser power control 55 and any one or more processors of the control computer 52 to perform one or more of the functions described herein.

The laser power control unit 55 can control the operation of the laser generator 12 so that the pulse energy, beam width, power level, and/or wavelength of the laser beam 13 generated by the laser generator 12 assumes a preselected value. The laser power control unit 55 can also control the period during which the laser generator 12 generates the laser beam 13. The control computer 52 is provided for controlling the operation of the laser power control unit 55, which can cause the laser generator 12 to generate a laser beam 13 of a preselected wavelength and power characteristics for a preselected period. At the same time, the control computer 52 can control the function of the adjustment mechanism 16 in operative association with the reflecting device 14 and, in the example using a galvanometer, the motor of the galvanometer. Thus, the control computer 52 can adjust the attitude and position of the reflecting surface 15 with respect to the reception of the laser beam 13 by the reflecting surface 15 and the position of a preselected portion of the edge directing member 50 to remove or prevent devitrification.

For example, the control computer 52 may configure the adjustment mechanism 16 to adjust (e.g., tilt or rotate) the reflecting surface 15 of the reflecting device 14 to a number of different orientations for receiving the laser beam 13 and reflecting the laser beam at the reflecting surface 15 of the reflecting device 14 for a preselected period of time. As a result, the laser beam 13 may be directed at a number of preselected portions of the edge director 50 for respective preselected periods of time, thereby inhibiting the accumulation of devitrified material on the edge director 50, as shown, for example, by the reflected laser beam 17 in FIG. 1 .

Figure 4 shows a block diagram of an example devitrification material suppression system 400 that may be used in place of or in conjunction with the devitrification material suppression system 10 of Figure 1. Those skilled in the art will readily appreciate that Figure 4 and the following description represent possible embodiments of a devitrification material suppression system, and that other configurations consistent with the teachings presented herein of a devitrification material suppression system are possible and contemplated by this disclosure. In this example, the devitrification material suppression system 400 may include a devitrification material removal device 401 having a moving mirror 402 configured to reflect a laser beam, such as laser beam 13 from a laser generator 12 (not shown), to an edge director 50 of the forming device. In some examples, the devitrification material removal device 401 includes a laser generator for generating a laser beam.

The devitrification material removal device 401 may further include a thermal imaging camera 420 that may capture a thermal image reflected by a thermal imaging camera mirror 422. For example, each thermal imaging camera mirror 422 may be configured (e.g., arranged) to reflect an image of the corresponding edge director 50 (and, e.g., adjacent regions) to the corresponding thermal imaging camera 420. In some examples, each thermal imaging camera may be a cooled thermal imaging camera, e.g., a water-cooled thermal imaging camera, and may further include an air purge system. For example, the devitrification material removal device 401 may include an air purge inlet 411 that may allow the introduction of air into the devitrification material removal device 401 to perform air purging, e.g., through the optical system 404. The optical system 404 may allow the generated laser beam to reach the moving mirror 402. The purge air entering the devitrification material removal device 401 through the air purge inlet 411 may also reduce/control the temperature of components within the devitrification material removal device 401, maintain a positive pressure within the devitrification material removal device 401 to prevent or minimize contamination from the external environment (e.g., airborne particles, gases (e.g., from a glass melting furnace), etc.), and/or prevent or minimize condensation on the optical components, e.g., components 402, 404.

The devitrification material removal apparatus 401 may also include transparent windows 408 located between adjacent window frames 410. The window frames 410 may be water-cooled window frames, and an air purge may be provided to other portions (e.g., the front) of the devitrification material removal apparatus 401, such as the mirror surface 402. This purge air may serve to prevent or minimize condensation of gases, such as those released during the glass manufacturing process, on the window and/or mirror surface, and to cool the window and/or mirror, e.g., low heat resistant materials may be used for these components. The moving mirror 402 may direct a reflected laser beam, e.g., the reflected laser beam 17, through the transparent window 408 to one or more of the forming device 20 and/or the edge director 50. The devitrification material removal apparatus 401 may further include spacers 414 made of fiberboard, stainless steel, a combination of fiberboard and stainless steel, or other suitable material. Each spacer 414 is coupled to the furnace wall 412. The furnace wall 412 can reduce or eliminate heat from the environment external to the devitrification material removal device 401, for example, heat generated by a glass furnace.

In some examples, the controller 406 may configure the mirrors 422 to reflect an image of the edge director 50 to the corresponding thermal imaging camera 420. The controller 406 may also configure each thermal imaging camera 420 to capture a thermal image of the edge director 50 (and, for example, adjacent regions) and provide the image to the controller. Based on the thermal image, the controller 406 may determine that devitrification material is present on the edge director. For example, the controller 406 may determine that a thermal gradient across the edge director 50 indicates that the edge director has accumulated devitrification material. In one embodiment, the edge director is at a lower temperature than the devitrification material, and the devitrification material, being crystallized and below its liquidus temperature, is at a lower temperature than the glass ribbon. The controller 406 is configured to detect these temperature differences between the forming device or edge director, the devitrification material, and the glass ribbon. As a non-limiting example, the controller 406 may detect a temperature discontinuity and determine that the discontinuity indicates the presence of devitrification material. In addition, the thermal imaging capability may also be used to target and/or control the location of the laser beam on the forming device, edge director, glass ribbon, and/or devitrified material associated with each. As another non-limiting example, the controller 406 may detect a temperature discontinuity between a desired target area of the laser beam and the actual location of the laser beam on, but not limited to, the forming device, edge director, glass ribbon, and/or devitrified material associated with each (which may be away from the desired target area). In this manner, a safety function of the laser beam is achieved.

In some examples, when the controller 406 determines that the edge director has accumulated devitrification material, the controller 406 may cause the laser generator to generate a laser beam, such as laser beam 13. In one embodiment, the laser generator is located in the controller 406 block. The controller 406 may also position a mirror 402 that moves to reflect the generated laser beam (e.g., reflected laser beam 17) to one or more portions of the edge director. For example, the controller 406 may direct energy from the generated laser to be reflected by the mirror 402 horizontally and vertically across the edge director 50. In some examples, the laser beam may be directed over a vertical range that includes the height of the edge director 50. In some examples, the laser beam may be directed over a vertical range that includes the lower portion of each edge director 50 (e.g., the portion where devitrification material is most likely to accumulate). In some examples, the laser beam may be directed over a horizontal range that includes the width of each edge director 50. In some examples, the laser beam may be directed across a horizontal range that includes a portion of the width of each edge director 50.

In other embodiments, other configurations of the components shown in devitrification material removal device 401 are possible, as one of ordinary skill in the art would understand. As a non-limiting example, optics 404 and moving mirror 402 may be combined. As another non-limiting example, optics 404, moving mirror 402, and controller 406 may be combined with a laser scanning/patterning module.

5 shows a block diagram of an example devitrification material suppression system 500 including a laser source 502, which may be a laser generator such as the laser generator 12 of FIG. 1, generating a laser through a fiber optic cable 503 and an adapter 506 to a collimator 508. The collimator 508 directs the laser through a tube 510, which may be a ceramic tube, to the devitrification material 102 accumulated on the edge director 50. The tube 510 may be attached to (or through) a ball joint 520 attached to a pedestal base 512 of a base 511. FIG. 5 shows the components 506, 508, and 510 in various positions due to the movement of the ball joint 520. The pedestal base 512 may be, for example, a gimbal base. The base 511 may be configured to direct the laser beam generated by the laser source 502 to the devitrification material 102 accumulated on the edge director 50. For example, the pedestal base 512 may be positioned to direct the laser beam exiting the tube 510 to a predetermined portion of the edge director 50. In some examples, the devitrification material suppression system 500 may include an air purge system to clear the tube 510. In some examples, the base 511 may be mechanically positioned to direct the laser beam. In some examples, the base 511 may be positioned, for example, by the control computer 52, to direct the laser beam.

The devitrification material suppression system 500 may also include a target laser source 504 that may be used to visually identify the portion of the edge director 50 that receives the laser generated by the laser source 502. For example, the target laser source 504 (also known in the art as a "tracker laser") may generate a green laser beam (also known in the art as a "tracker beam") that exits through a tube 510. The green laser beam may be used to visually position the pedestal base 512 so that the green laser beam, and in turn the laser beam generated by the laser source 502, is aligned with the edge director 50 or a portion thereof. For example, the controller may activate the target laser source 504 and a user may adjust the pedestal base 512 until the green laser beam is visible over at least a portion of the devitrification material that has accumulated on the edge director 50. The controller may then (e.g., upon receiving user input) activate the laser source 502, such as a diode laser or _CO2 laser, to direct laser energy to the devitrification material 102 that has accumulated on the edge director 50.

6 shows a block diagram of an example devitrification material suppression system 600 similar to the devitrification material suppression system 500 of FIG. 5 but without the collimator 508. Instead, the devitrification material suppression system 600 may include an optical coupler 602 that directs the laser beam generated by the laser source 502 through an optical fiber 605, such as a sapphire optical fiber, through a tube 604. Also, because the laser is guided through the optical fiber 605 in the tube 604, the devitrification material suppression system 600 may not require an air purge system. As shown, the devitrification material suppression system 600 may also include a target laser source 504 to visually align the target of the emitted laser, in this example the devitrification material 102 accumulated on the edge director 50.

In the examples of Figures 5 and 6, a diode laser operating at 1 μm or about 1 μm wavelength can be used. In some examples, a fiber-coupled laser can be used. As known in the art, a fiber-coupled laser includes a laser source, the output of which is coupled to a fiber that can be used as a gain medium. Fiber-coupled lasers are convenient for routing and/or aligning the laser beam. Fiber-coupled lasers can have better mode quality than other laser configurations, and the laser beam can be delivered using, for example, a single mode fiber.

5 and 6 use a laser to heat the devitrified material, in other examples, resistive heating (e.g., heat lamps or flash lamps), infrared light emitting diodes (LEDs), magnetrons, or laser-induced gas discharge lamps may be used to generate the energy directed to the edge director 50. In some examples, an atmospheric plasma jet may be used to heat the devitrified material. This approach can generate a relatively extremely hot gas jet and may be used when laser power is insufficient to cause devitrified material melting.

7 illustrates a thermal model ₇₀₀ showing the increase in surface temperature of a flowing glass, such as molten glass, along the downward inclined focusing shaping surface 32 to the root 34 based on distance from the former surface (e.g., downward inclined focusing shaping surface 32) when heated by a laser, such as a _CO2 laser (e.g., a 10.6 μm CO2 laser) used by the devitrification material suppression system as described herein. As shown, location 702 is the target for each of the two lasers. Specifically, the chart shows the increase in glass surface temperature for a _CO2 laser emitting at 20 watts of power and having a beam diameter of about 8 mm in a first example. The chart also shows the increase in glass surface temperature for a _CO2 laser emitting at 50 watts of power and having a beam diameter of about 10 mm in a second example.

For each laser, the molten glass close to the former surface as well as the former surface itself does not experience a significant temperature rise (near 0 degrees Celsius) when irradiated by the laser compared to the temperature rise of the surface of the molten glass farther from the former surface (e.g., at a distance of about 0.8 inches or more). Thermal modeling also shows that a _CO2 laser emitting at 20 watts raises the temperature of the molten glass more than a _CO2 laser emitting at 50 watts measured at the same distance from the former surface. In some instances, the devitrification material suppression system described herein may use one of these lasers when components under the devitrification material layer need to be protected from high temperatures or temperature fluctuations.

Figures 8A and 8B show infrared transmission spectrum graphs of different devitrified material crystals, namely, cristobalite and tridymite, respectively. Each graph has wavenumber (cm ^-1 ) on the X-axis and the transmitted fraction of laser energy on the Y-axis. As shown in Figure 8A, cristobalite may absorb a maximum amount of laser energy (i.e., provided by a laser described herein) at a wavenumber near 1100 cm ^{- 1, with more than about 90% of the laser energy being absorbed (and less than about 10% of the laser energy being transmitted through the cristobalite). Figure 8B shows that tridymite may absorb a maximum amount of laser energy at a wavenumber slightly less than 1100 cm-1} , with more than about 60% of the laser energy being absorbed (and less than about 40% of the laser energy being transmitted through the tridymite).

In some examples, a devitrification material suppression system described herein, e.g., devitrification material suppression system 10, devitrification material suppression system 400, devitrification material suppression system 500, or devitrification material suppression system 600, may include a table indicating the transmission absorptance for one or more devitrification material crystals. The table may be stored, e.g., in a memory device. The devitrification material suppression system may determine the wavelength of the laser based on the table. For example, the devitrification material suppression system may configure a laser generator, e.g., laser generator 12, to generate a laser having a wavelength corresponding to a wavelength that causes the devitrification material to absorb a maximum or nearly maximum amount of laser energy.

In some examples, the devitrification material suppression system may receive data identifying the type of devitrification material (e.g., the type of crystal that makes up the devitrification material) and determine the laser wavelength based on the type of devitrification material. In some examples, more than one type of devitrification material may be identified. The devitrification material suppression system may program the laser generator to generate a laser beam of a wavelength determined for each type of devitrification material, and the laser generator may periodically and/or occasionally and/or based on an input signal change the wavelength of the laser beam output from the laser generator from one determined wavelength to another (e.g., the laser generator includes two or more laser sources and the devitrification material suppression system may switch from one laser source to another laser source). In other embodiments, the devitrification material suppression system may use two or more lasers and/or two or more wavelengths. Multiple lasers and/or multiple wavelengths may be used simultaneously to remove and/or suppress multiple types of devitrification materials that may be present.

FIG. 9 shows a graph illustrating the transmission percentages of different devitrification material crystals, namely yttria, spinel, sapphire, aron, and mullite. The graph shows wave numbers and corresponding wavelengths on the bottom and top X-axes, respectively, and the transmission percentage of laser energy on the Y-axis. As discussed above with respect to FIG. 8, the devitrification material suppression system described herein may determine the wavelength of the laser based on the transmission percentages identified in the graph for the various devitrification material crystals.

10 shows a simplified block diagram of a devitrification material suppression system 1000 including a controller 1004 receiving an input 1002 and an error/sensor signal 1011 from a plurality of sensors 1010. The input 1002 and the error/sensor signal 1011 are combined at a combiner 1012 to generate a controller input signal 1013. The controller 1004 may include one or more processors, such as a GPU (graphic processing unit), a CPU (central processing unit), or any other suitable processing device. The input 1002 may include, for example, the current wavelength and/or power of the laser and the current devitrification material position (e.g., the position of the devitrification material on the edge director 50). The plurality of sensors 1010 may include, for example, one or more of a temperature camera, a visual camera, a laser power sensor, and a position sensor (e.g., a galvanometer position sensor). The controller 1004 may generate adjustment data 1005 based on the controller input signal 1013. The adjustment data 1005 may specify and represent, for example, adjustments to the current pulse energy, beam width, power level, and/or wavelength of the laser, the direction/target position of the laser, whether to turn the laser on or off, the location of the devitrifying material (e.g., a different location on the edge director), or the sensor 1010 (e.g., changing the orientation or position sensor of a thermal camera). The scan recipe 1006 receives the adjustment data 1005 and generates output 1008 to implement the changes specified by the adjustment data 1005 by controlling corresponding equipment, such as galvanometers for laser mirror placement, a laser generator for laser power, and the sensor 1010. The output 1008 may include, for example, a change to any of the sensors 1010, a change to the laser wavelength, power, or orientation, a change to enable or disable the laser, or any other suitable change.

For example, based on the input 1002 and the plurality of sensors 1010, the controller 1004 may generate adjustment data 1005 to disable the laser, tilt and/or rotate a mirror directing the reflected beam of the laser, and/or enable the laser. In some examples, the controller 1004 may receive thermal imaging data from the sensor 1010 that identifies and represents a thermal image of the accumulated devitrified material on the edge director. Based on the thermal imaging data, the controller 1004 may generate adjustment data 1005 to tilt and/or rotate a mirror to direct the reflected laser beam from the laser generator to the accumulated devitrified material. The controller 1004 may then generate adjustment data 1005 to turn on the laser. The controller 1004 may leave the laser enabled until the controller 1004 determines, based on the thermal imaging data received from the sensor 1010, that the temperature of the devitrified material has reached at least the liquidus temperature. The controller 1004 may then generate adjustment data 1005 to turn off the laser and reposition the mirrors to direct the reflected laser beam from the laser generator to another edge director 50.

11 illustrates an exemplary method that may be performed by one or more computing devices, such as control computer 52. Beginning at step 1102, a location of edge director 50 on glass forming apparatus 20 may be identified. For example, the location of edge director 50 may be determined based on image data from a camera pointed at glass forming apparatus 20. At step 1104, a first thermal image of edge director 50 at the identified location is obtained from a thermal camera, such as thermal camera 420. For example, control computer 52 may point the thermal camera to obtain thermal images from locations including the identified location and receive thermal image data identifying and representing the thermal image.

Proceeding to step 1106, the presence of devitrification material on the edge director 50 may be determined based on the first thermal image. For example, the control computer 52 may determine that devitrification material has accumulated on the edge director 50 based on thermal mismatches across the edge director 50 identified by the thermal imaging data. In step 1108, a mirror may be positioned to direct the laser beam to the located devitrification material. For example, the control computer 52 may control the reflector 14 to reposition the reflector surface 15 to direct the laser beam 13 to the located devitrification material on the edge director 50. In step 1110, the laser source may be controlled to direct the laser beam to the mirror. For example, the control computer 52 may enable the laser generator 12 to generate a laser beam that is directed to the reflector surface 15 of the reflector 14. The laser beam may then be directed to the devitrification material as described above.

Proceeding to step 1112, a second thermal image of the edge director 50 at the located position may be obtained from the thermal camera. In step 1114, it may be determined whether the located devitrification material has melted and/or been removed. For example, the control computer 52 may determine whether the accumulated devitrification material has reached at least a liquidus temperature based on the second thermal image. If it is determined that the devitrification material has not melted, the method may return to step 1108 and the mirror may be controlled to direct the laser beam to the same or a different portion of the located devitrification material. Otherwise, if it is determined that the devitrification material has melted, the method may proceed to step 1116. In step 1116, the mirror and the laser source may be controlled to direct the laser beam across the edge director 50 (e.g., vertically and/or horizontally) to maintain a minimum temperature at the edge director. Alternatively, the laser may be turned off. The minimum temperature may be, for example, a temperature identified to prevent accumulation of devitrification material on the edge director 50. The control computer 52 may determine whether the temperature of the edge director is at least a minimum temperature based on thermal image data from, for example, a thermal camera.

Although the methods described above refer to exemplary flow charts, it will be appreciated that many other ways of performing the operations associated with the methods may be used. For example, the order of some operations may be changed and some of the described operations may be omitted.

In addition, the methods and systems described herein may be embodied at least in part in the form of computer-executed processes and apparatuses for performing the processes. The methods of the present disclosure may also be embodied at least in part in the form of a tangible non-transitory machine-readable storage medium having computer program code stored thereon. For example, the steps of the method may be embodied in hardware, executable instructions (e.g., software) executed by a processor, or a combination of the two. The medium may include, for example, a RAM, a ROM, a CD-ROM, a DVD-ROM, a BD-ROM, a hard disk drive, a flash memory, or any other non-transitory machine-readable storage medium. When the computer program code is loaded and executed on a computer, the computer becomes an apparatus for performing the method. The method may also be embodied at least in part in the form of a computer on which the computer program code is loaded and executed, becoming a dedicated computer for performing the method. When executed on a general-purpose processor, the computer program code segments configure the processor to generate specific logic circuits. Alternatively, the method may be embodied at least in part in an application-specific integrated circuit for performing the method.

The above description is provided for the purpose of illustrating, explaining, and describing embodiments of the present disclosure. Modifications and variations to these embodiments will be apparent to those skilled in the art and may be made without departing from the scope and spirit of the present disclosure.

The following describes preferred embodiments of the present invention.

EMBODIMENT 1
An apparatus comprising:
a memory device for storing instructions;
a controller having at least one processor and configured to execute the instructions, the instructions causing the controller to preselect a portion of a glass forming apparatus;
a reflector configured to reflect a laser beam from a laser generator onto said preselected portion of said glass forming apparatus;
and activating said laser generator to generate said laser beam and heat said preselected portion of said glass forming apparatus for devitrification inhibition.

EMBODIMENT 2
the controller receives sensor data from at least one sensor;
determining a power level of the laser beam;
2. The apparatus of embodiment 1, configured to configure the laser generator to generate a laser beam at the determined power level.

EMBODIMENT 3
The controller receives a user input identifying a type of devitrification material for devitrification material suppression;
determining a power level of the laser beam based on the type of devitrified material;
2. The apparatus of embodiment 1, configured to configure the laser generator to generate a laser beam at the determined power level.

EMBODIMENT 4
2. The apparatus of embodiment 1, wherein the preselected portion of the glass forming apparatus comprises an edge director.

EMBODIMENT 5
the controller receives first thermal image data from a thermal imaging device;
determining that devitrified material has accumulated on the preselected portion of the glass forming apparatus;
2. The apparatus of claim 1, configured to operate the laser generator to generate the laser beam and heat the preselected portion of the glass forming apparatus to remove the determined devitrified material.

EMBODIMENT 6
the controller receives second thermal image data from the thermal imaging device;
determining that the devitrified material has been removed based on the second thermal imaging data;
6. The apparatus of embodiment 5, configured to shut down the laser generator to disable the laser beam.

EMBODIMENT 7
the controller determines a raster pattern for applying the laser beam to the preselected portion of the glass forming apparatus;
configuring the reflector to reflect a laser beam from the laser generator to the preselected portion of the glass forming apparatus according to the determined raster pattern;
2. The apparatus of claim 1, configured to operate the laser generator to generate the laser beam and heat the preselected portion of the glass forming apparatus according to the determined raster pattern.

EMBODIMENT 8
1. An apparatus comprising:
a laser generator operable to generate a laser beam;
a reflector configured to reflect a laser beam from the laser generator to a glass forming apparatus;
a controller communicatively coupled to the laser generator and the reflector, the controller configured to preselect a portion of the glass forming apparatus;
configuring the reflector to reflect a laser beam from the laser generator onto the preselected portion of the glass forming apparatus;
an apparatus configured to operate the laser generator to generate the laser beam and heat the preselected portion of the glass forming apparatus for devitrification inhibition.

EMBODIMENT 9
Equipped with a thermal imaging device,
the controller is operably coupled to the thermal imaging device;
receiving first thermal imaging data of the preselected portion of the glass forming apparatus from the thermal imaging device;
detecting devitrified material on the preselected portion of the glass forming apparatus based on the first thermal imaging data;
9. The apparatus of claim 8, configured to operate the laser generator to generate the laser beam and heat the preselected portion of the glass forming apparatus to remove the detected devitrified material.

EMBODIMENT 10
the controller receives second thermal image data from the thermal imaging device;
determining that the detected devitrified material has been removed based on the second thermal imaging data;
10. The apparatus of embodiment 9, configured to shut down the laser generator to disable the laser beam.

EMBODIMENT 11
9. The apparatus of embodiment 8, wherein the preselected portion of the glass forming apparatus is an edge director.

EMBODIMENT 12
Equipped with a position sensor,
the controller is communicatively coupled to the position sensor;
configured to receive position data from the position sensor identifying a position of the reflector;
9. The apparatus of claim 8, wherein configuring the reflecting device to reflect the laser beam from the laser generator to the preselected portion of the glass forming apparatus comprises at least one of rotating or tilting a reflective surface of the reflecting device based on the received position data.

EMBODIMENT 13
1. A method for removing devitrified material from a glass forming apparatus, comprising:
preselecting a portion of the glass forming equipment;
configuring a reflector to reflect a laser beam from a laser generator onto the preselected portion of the glass forming apparatus;
and operating the laser generator to generate the laser beam and heat the preselected portion of the glass forming apparatus.

EMBODIMENT 14
determining a power level of the laser beam based on the type of devitrified material;
14. The method of claim 13, further comprising: configuring the laser generator to generate a laser beam at the determined power level.

EMBODIMENT 15
receiving a user input identifying a type of the devitrified material;
determining a power level of the laser beam based on the type of devitrified material;
14. The method of claim 13, further comprising: configuring the laser generator to generate a laser beam at the determined power level.

EMBODIMENT 16
14. The method of claim 13, wherein the preselected portion of the glass forming apparatus comprises an edge director.

EMBODIMENT 17
receiving first thermal imaging data from a thermal imaging device;
and determining that the devitrified material has accumulated on the preselected portion of the glass forming apparatus.

EMBODIMENT 18
receiving second thermal imaging data from the thermal imaging device;
determining that the devitrified material has been removed based on the second thermal imaging data; and
18. The method of claim 17, further comprising the step of shutting down the laser generator to disable the laser beam.

EMBODIMENT 19
determining a raster pattern for applying the laser beam to the preselected portion of the glass forming apparatus;
and configuring the reflector to reflect the laser beam from the laser generator to the preselected portion of the glass forming apparatus according to the determined raster pattern;
14. The method of embodiment 13, wherein the step of activating the laser generator comprises activating the laser generator according to the determined raster pattern.

EMBODIMENT 20
receiving position data from a position sensor identifying a position of the reflector;
14. The method of claim 13, wherein configuring the reflector to reflect the laser beam from the laser generator to the preselected portion of the glass forming apparatus comprises at least one of rotating or tilting a reflective surface of the reflector based on the received position data.

EMBODIMENT 21
a laser generator operable to generate a laser beam;
a reflector configured to reflect a laser beam from the laser generator to a glass forming apparatus;
a controller communicatively coupled to the laser generator and the reflector,
preselecting a portion of the glass forming apparatus;
configuring the reflector to reflect a laser beam from the laser generator onto the preselected portion of the glass forming apparatus;
a controller configured to operate the laser generator to generate the laser beam;
a devitrified material is positioned on the glass forming apparatus and molten glass is positioned along the path of the laser beam between the preselected portion of the glass forming apparatus and the laser generator;
The laser beam heats the molten glass.

EMBODIMENT 22
1. A method for removing devitrified material from a glass forming apparatus, comprising:
preselecting a portion of the glass forming equipment;
configuring a reflector to reflect a laser beam from a laser generator onto the preselected portion of the glass forming apparatus;
and operating the laser generator to generate the laser beam;
a devitrified material is positioned on the glass forming apparatus and molten glass is positioned along the path of the laser beam between the preselected portion of the glass forming apparatus and the laser generator;
The method wherein the laser beam heats the molten glass.

10 Devitrification material suppression system 12 Laser generator 13 Laser beam 14 Reflector 15 Reflector surface 16 Adjustment mechanism 17 Reflected laser beam 18 Rotating shaft 20 Glass forming device 22 Forming wedge 24 Open channel 25, 26 Wall 27, 28 Overflow weir 30 Forming surface 32 Downwardly inclined focusing forming surface 34 Root 38 Delivery passage 40 Dam 42 Free surface 44 Glass ribbon 46 Pulling roll 48 Side edge 50 Edge guide member 52 Control computer 55 Laser power control 102 Devitrification material 104 Edge guide member 401 Devitrification material removal device 402 Moving mirror 404 Optical system 406 Controller 408 Window 410 Window frame 411 Air purge inlet 412 Furnace wall 414 Spacer 420 Thermal imaging camera 422 Mirror

Claims (12)

An apparatus comprising:
a laser generator operable to generate a laser beam;
a reflector configured to reflect a laser beam from the laser generator to a glass forming apparatus;
a controller communicatively coupled to the laser generator and the reflector, the controller configured to preselect a portion of the glass forming apparatus;
configuring the reflector to reflect a laser beam from the laser generator onto the preselected portion of the glass forming apparatus;
configured to operate the laser generator to generate the laser beam and heat the preselected portion of the glass forming apparatus for devitrification inhibition ;
The preselected portion of the glass forming apparatus is an edge director . Equipped with a thermal imaging device,
the controller is operably coupled to the thermal imaging device;
receiving first thermal imaging data of the preselected portion of the glass forming apparatus from the thermal imaging device;
detecting devitrified material on the preselected portion of the glass forming apparatus based on the first thermal imaging data;
2. The apparatus of claim 1 configured to operate the laser generator to generate the laser beam to heat the preselected portion of the glass forming apparatus to remove the detected devitrified material. the controller receives second thermal image data from the thermal imaging device;
determining that the detected devitrified material has been removed based on the second thermal imaging data;
The apparatus of claim 2 configured to shut down the laser generator to disable the laser beam. Equipped with a position sensor,
the controller is communicatively coupled to the position sensor;
configured to receive position data from the position sensor identifying a position of the reflector;
2. The apparatus of claim 1, wherein configuring the reflecting device to reflect the laser beam from the laser generator to the preselected portion of the glass forming apparatus comprises at least one of rotating or tilting a reflective surface of the reflecting device based on the received position data. 1. A method for removing devitrified material from a glass forming apparatus, comprising:
preselecting a portion of the glass forming equipment;
configuring a reflector to reflect a laser beam from a laser generator onto the preselected portion of the glass forming apparatus;
operating the laser generator to generate the laser beam and heat the preselected portion of the glass forming apparatus;
The method includes: determining a power level of the laser beam based on the type of devitrified material;
configuring the laser generator to generate a laser beam at the determined power level;
The method of claim 5 further comprising: receiving a user input identifying a type of the devitrified material;
determining a power level of the laser beam based on the type of devitrified material;
configuring the laser generator to generate a laser beam at the determined power level;
The method of claim 5 further comprising: The method of claim 5 , wherein said preselected portion of said glass forming apparatus comprises an edge director. receiving first thermal imaging data from a thermal imaging device;
determining that the devitrified material has accumulated on the preselected portion of the glass forming apparatus;
The method of claim 5 further comprising: receiving second thermal imaging data from the thermal imaging device;
determining that the devitrified material has been removed based on the second thermal imaging data; and
shutting down the laser generator to disable the laser beam;
10. The method of claim 9 further comprising: determining a raster pattern for applying the laser beam to the preselected portion of the glass forming apparatus;
configuring the reflector to reflect a laser beam from the laser generator to the preselected portion of the glass forming apparatus according to the determined raster pattern;
Further comprising:
The method of claim 5 , wherein the step of activating a laser generator comprises activating the laser generator according to the determined raster pattern. receiving position data from a position sensor identifying a position of the reflector;
6. The method of claim 5, wherein configuring the reflecting device to reflect the laser beam from the laser generator to the preselected portion of the glass forming apparatus comprises at least one of rotating or tilting a reflective surface of the reflecting device based on the received position data.

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