Apparatus and method for controlling substrate thickness

A control apparatus for controlling a thickness of a substrate, such as a glass ribbon. The control apparatus comprises a laser assembly and a shielding assembly. The laser assembly generates an elongated laser beam traveling in a propagation direction along an optical path. The shielding assembly comprises at least one shield selectively disposed in the optical path. The shield is configured to decrease an optical intensity of a region of the elongated laser beam. The shielding assembly is configured to change an intensity profile of the elongated laser beam from an initial intensity profile to a targeted intensity profile. A desired targeted intensity profile can be dictated by an arrangement of the shield(s) relative to the optical path, and can be selected to affect a temperature change at portions of the substrate determined to benefit from a reduction in thickness.

BACKGROUND

Field

The present disclosure generally relates to apparatuses and methods for making substrates such as glass. More particularly, it relates to apparatuses and methods for controlling the thickness of glass substrates in glass making processes.

Technical Background

For a variety of applications, the close control of the thickness of manufactured substrates can be important. For example, diverse procedures have been implemented and proposed for controlling thickness variations that can occur in liquid crystal display (LCD) glass (or glass for other display types) manufactured by a fusion downdraw method and other glass production methods causing variations in the thickness of the glass ribbon. Thermo-mechanical and glass flow conditions can be uneven across the entirety or portions of a width of the glass ribbon as it is being formed in the fusion downdraw method. Typically, the surface tension at the glass ribbon as it is being formed is inadequate to entirely obviate the variations that can occur in the thickness of the glass ribbon. Although the variations may be a few microns in size, the consequences of such variations can be significant with respect to display glass end use applications for example.

A conventional technique for addressing glass ribbon thickness variations entails placement of a high thermal conductivity plate near the glass ribbon at a location where a temperature of the glass ribbon is at its softening point. A bank of tubes are arranged behind the plate, each ejecting a cooling fluid onto the plate. The objective is to generate thermal gradients across the glass ribbon, perpendicular to the direction of glass travel. These thermal gradients change the localized viscosity of the glass, and thus local thickness, from the downward pull force. The fluid flow from each tube is individually controllable. By adjusting the fluid flow from the tubes, the local temperature on the front face of the plate can be controlled. This local temperature affects the local heat loss, and thus the local temperature of the molten glass, which, in turn, affects the final thickness distribution across the width of the ribbon. For example, if a thickness trace of the glass ribbon indicates that a particular area across the width of the glass ribbon is thicker than desired, the thickness trace is corrected by cooling zones of the glass ribbon adjacent to the thicker area (e.g., cooling the thinner zones by delivering the cooling fluid through the tubes corresponding with the thinner zones, and not delivering the cooling fluid through the tube(s) corresponding with the thicker area).

While well accepted, the glass thickness control techniques described above may not be able to generate a high resolution temperature gradient meeting rigorous thickness uniformity specifications. Other concepts, such as heating small segments of the glass ribbon with a conventional spot-type laser beam scanned across the glass ribbon are cost prohibitive and can entail complex mechanisms ill-suited for high temperature environments, such as those associated with glass ribbon production.

Accordingly, alternative apparatuses and methods for controlling a thickness of a substrate, such as a continuously moving a glass ribbon in a glass manufacturing process, are disclosed herein.

SUMMARY

Some embodiments of the present disclosure relate to a control apparatus for controlling a thickness of at least a portion of a substrate, such as a glass ribbon. The control apparatus comprises a laser assembly and a shielding assembly. The laser assembly is configured to generate an elongated laser beam traveling in a propagation direction along an optical path. The elongated laser beam has a shape in a plane perpendicular to the propagation direction, and the shape of the elongated laser beam defines a major axis. The shielding assembly comprises a shield selectively disposed in the optical path. The shield is configured to decrease an optical intensity of a region of the elongated laser beam. The shielding assembly is configured to change an intensity profile of the elongated laser beam across the major axis from an initial intensity profile to a targeted intensity profile. In some embodiments, the shielding assembly generates the targeted intensity profile to have one or more regions of elevated optical intensity, and one or more regions of reduced optical intensity (including zero laser energy or power). A laser energy or power of the region(s) of elevated optical intensity is sufficient to raise a temperature and reduce a viscosity of a substrate, such as glass ribbon, in a viscous state; the laser energy or power of the region(s) of reduced optical intensity is not sufficient to raise a temperature and reduce a viscosity of the substrate in the viscous state. In some embodiments, the shielding assembly includes two or more shields and an actuator associated with each of the shields for articulating respective ones of the shields into and out of the optical path.

Yet other embodiments of the present disclosure relate to a system for forming a glass ribbon. The system comprises a glass forming apparatus and a control apparatus. The glass forming apparatus is configured to produce a glass ribbon. The control apparatus comprises a laser assembly and a shielding assembly. The laser assembly is configured to generate an elongated laser beam traveling in a propagation direction along an optical path. The elongated laser beam has a shape in a plane perpendicular to the propagation direction. The shape of the elongated laser beam defines a major axis. The shielding assembly comprises a shield selectively disposed in the optical path (i.e., the shielding assembly permits for or facilitates operational arrangements in which the shield is disposed or located in the optical path and for other operational arrangements in which the shield is not disposed or located in the optical path). The shield is configured to decrease an optical intensity of a region of the elongated laser beam. The shielding assembly is configured to change an intensity profile of the elongated laser beam across the major axis from an initial intensity profile to a targeted intensity profile. The control apparatus is configured to control and direct the elongated laser beam with the targeted intensity profile onto the glass ribbon to decrease a thickness of a portion of the glass ribbon.

Yet other embodiments of the present disclosure relate to a method for controlling a thickness of at least one preselected portion of a substrate, such as a glass ribbon. The method comprises generating an elongated laser beam traveling in a propagation direction. The elongated laser beam comprises a shape in a plane perpendicular to the propagation direction. The shape defines a major axis. The elongated laser beam further comprises an intensity profile across the major axis. A region of the elongated laser beam is shielded to change the intensity profile from an initial intensity profile to a targeted intensity profile. The targeted intensity profile comprises a first region and a second region, and an optical intensity of the second region is less than an optical intensity of the first region. The elongated laser beam with the targeted intensity profile is directed onto the substrate. In this regard, the first region corresponds with a first portion of the substrate and the second region corresponds with a second portion of the substrate to cause a reduction in the thickness of the substrate at the first portion. In some embodiments, the method further comprises monitoring a thickness of the substrate and manipulating shields relative to the optical path to generate the targeted intensity profile as a function of the monitored thickness.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of apparatuses and methods for controlling a thickness of a substrate, such as a glass ribbon and glass manufacturing operations. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts.

It can be the case in the production of a substrate such as a glass or plastic substrate for example that the thickness of the substrate that is produced is non-uniform. The non-uniformity can be localized, in which case the non-uniformity would be present at a somewhat discrete portion of the substrate as viewed across the width. On the other hand, a plurality of non-uniformities can exist, even in some cases across the entire width of the substrate.

It is usually the case that in the production of a substrate, such as glass or plastic substrate for example, that particular thickness non-uniformities in the substrate, if not corrected, will continue to be manifested as the substrate is continued to be produced. According some aspects of the present disclosure, these thickness non-uniformities are identified and pre-selected for attention so that the non-uniformities can be essentially eliminated in the subsequently-produced substrate. The correction of the thickness non-uniformities is accomplished by increasing the temperature and decreasing the viscosity of the portion(s) of the substrate at which the non-uniformities are present, while the substrate is in a viscous state. As a result, the respective thickness of each non-uniform portion of the substrate is made uniform in the subsequently-produced substrate as described in greater detail below.

A substrate is considered to be in a viscous state so long as its viscosity is such that the response of the substrate to the application of a stress is intermediate the behavior of a pure liquid and an elastic solid. Whenever the response of the substrate is that of an elastic solid, the thickness of the substrate is considered to be “fixed” as that term is used and applied herein.

Some aspects of the present disclosure provide glass ribbon production systems in which a continuously formed glass ribbon is subjected to conditions that promote control or correction of thickness non-uniformities. Although the systems, apparatuses and methods are described herein as being useful with glass ribbons or glass sheets, the systems, apparatuses and methods of the present disclosure can also be employed with other substrates such as plastic substrates. With this mind,FIG.1illustrates one embodiment of a system20in accordance with principles of the present disclosure and useful in forming a glass ribbon22having a width W and a thickness T. The system20includes a glass forming apparatus, indicated generally at30, and a control apparatus, indicated generally at32. In general terms, the glass forming apparatus30generates the glass ribbon22, and the control apparatus32is operable to correct or address non-uniformities in the thickness T of the glass ribbon22, such as by directing an elongated laser beam34onto the glass ribbon22. As described in greater detail below, the control apparatus32formats the elongated laser beam34to have or exhibit a targeted intensity profile at the glass ribbon22that varies applied laser energy across the width W.

In some non-limiting embodiments, the glass forming apparatus30can be a downdraw glass forming apparatus. Downdraw glass forming processes for manufacturing glass substrates such as the glass ribbon22and employing equipment such as the glass forming apparatus30are sometimes referred to as fusion processes, overflow processes or overflow downdraw processes. The schematic representations of the glass forming apparatus30and the control apparatus32are referred to herein with respect to the descriptions to follow of aspects, embodiments and examples of methods an apparatuses that concern the control of the thickness of a glass substrate such as the glass ribbon22for example.

Included in the embodiment of the glass forming apparatus30illustrated inFIG.1is a forming body (e.g., wedge)50that includes an open channel52(referenced generally) and a pair of converging forming surfaces54,56that converge at lower apex that comprises a root58of the forming body50. Molten glass is delivered into the open channel52and overflows the walls thereof, thereby separating into two individual flows or streams60,62that flow over the forming surfaces54,56. When the separate flows60,62of molten glass reach the root58, the recombine, or fuse, to form a single ribbon of viscous molten glass (i.e., the glass ribbon22) that descends from the root58. At approximately this point the glass ribbon22is in a viscous state and the thickness of the glass ribbon22has not become fixed so that the thickness of the glass ribbon22can be altered according to some aspects of the present disclosure. The glass ribbon22is drawn away from the root58, as indicated by arrow64. For example, pulling rollers (not shown) or similar devices can be located downstream of the root58and operate to apply tension to the glass ribbon22. The pulling rollers can be positioned sufficiently below the root58that the thickness of the glass ribbon22is essentially fixed at that location. The pulling rollers draw the glass ribbon22downwardly from the root58at a prescribed rate that establishes the thickness of the glass ribbon22as it is formed at the root58. Aspects of the present disclosure are equally applicable to other substrate (e.g., glass ribbon) forming techniques, such as a single sided overflow process or a slot draw process, which basic processes are well known to those skilled in the art.

In the aspect illustrated inFIG.1, the control apparatus32is configured to generate and emit the elongated laser beam34adequate to increase the temperature and decrease the viscosity of at least one preselected portion of a glass substrate in a viscous state, such as the glass ribbon22in a viscous state for example, when the elongated laser beam34is directed onto the glass substrate in a viscous state and thereby alter the thickness of the at least one preselected portion of the glass substrate. As illustrated in the aspect ofFIG.1, the elongated profile laser beam34is directed to the glass ribbon22at a location adjacent the root58of the forming body50where the glass ribbon22is in a viscous state. However, the elongated laser beam34can be directed to the glass ribbon22at other locations where the glass ribbon22is in a viscous state.

In one aspect and depending upon the characteristics of the glass substrate, the viscosity of the glass substrate in a viscous state would be greater than approximately 100,000 poise but not so great that the thickness of the substrate would be fixed. At viscosities greater than 100,000 poise but less than the viscosity of the glass substrate when the thickness is fixed, the application of heat to the glass substrate effectively decreases the viscosity of the glass substrate at the point at which the heat is applied, and the heat is not dissipated in the glass substrate as would occur at lower substrate viscosities.

The adequacy of a laser beam for the purpose of increasing the temperature and decreasing the viscosity of at least one preselected portion of a glass ribbon is a function primarily of the characteristics of the glass ribbon in a viscous state, the wavelength and the power level of the laser beam, and whether an objective is to alter the thickness of a limited or a large number of preselected portions of the glass substrate. For example, according to one aspect, where the glass substrate comprises a single layer, the wavelength of the laser beam can be selected so that the laser beam is substantially absorbed by the glass substrate and does not readily pass through the glass substrate.

With the above in mind,FIG.2illustrates one embodiment of the control apparatus32in block form. The control apparatus32includes a laser assembly100and a shielding assembly102. In general terms, the laser assembly100is configured to generate the elongated laser beam34(an outer extent of which is represented by dashed lines) traveling in a propagation direction104. The shielding assembly102includes one or more shields106(drawn generally) disposed in an optical path of the elongated laser beam34that are each configured to decrease an optical intensity of a portion of the elongated laser beam34. As a result, an optical intensity profile of the elongated laser beam34is altered by the shielding assembly102from an initial intensity profile to a targeted intensity profile. In other words, the elongated laser beam34, as generated by the laser assembly100, has or exhibits the initial intensity profile optically before or upstream of the shielding assembly102(generally identified by the region108ainFIG.2). The initial intensity profile is changed to the targeted intensity profile by the shielding assembly102. The resultant targeted intensity profile thus exists optically after or downstream of the shielding assembly102(generally identified by the region108binFIG.2). As described below, the targeted intensity profile of the elongated laser beam34is selected to more distinctly affect portions of the glass ribbon22designated as having thickness non-uniformities.

As used throughout this disclosure, a “shape” of the elongated laser beam34is in reference to a perimeter shape or extent of the elongated laser beam34in a plane perpendicular to the propagation direction104. The laser assembly100is configured to generate the elongated laser beam34such that the shape is elongated (e.g., is not a circle). For example, the elongated laser beam34can have an elliptical shape in the plane perpendicular to the propagation direction104as represented byFIG.3A. Other elongated shapes are also acceptable that may or may not be or include an ellipse (e.g., the elongated shape can be a line or planar). Regardless, and with cross-reference betweenFIGS.2and3A, the elongated shape of the elongated laser beam34in a plane perpendicular to the propagation direction104(that is otherwise into a plane of the page ofFIG.3A) defines a major axis110and a minor axis112orthogonal to the major axis110. A width WL of the shape of the elongated laser beam34is defined as the dimension along the major axis110, and a height HL is defined as the dimension along the minor axis112. It will be understood that the elongated laser beam34, may experience divergence as it propagates in space, and in some embodiments this divergence is more pronounced along the major axis110. Thus, the width WL, and optionally the height HL, can vary as a function of the distance between the reference point and the laser assembly100. However, the laser assembly100is configured and arranged relative to the glass ribbon22(or other substrate of interest) such that at the point where the elongated laser beam34impinges upon the glass ribbon22, the width:height (WL:HL) aspect ratio of the elongated laser beam34is 4:1 or more, optionally 10:1 or more. In some non-limiting embodiments, the width WL of the elongated laser beam34at the glass ribbon22can be on the order of 60-1000 millimeters (mm), and the height HL can be on the order of 1-4 mm. Other dimensions are also acceptable.FIG.2further reflects that in some embodiments, the laser assembly100is located such that at the point of impingement on the glass ribbon22(or other substrate of interest), the shape of the elongated laser beam34spans the entire width W of the glass ribbon22. For example, where the elongated laser beam34diverges from the laser assembly100(and/or from the shielding assembly102), the laser assembly100can be located at an appropriate distance from the glass ribbon22such that at the point of impingement, the width WL of the elongated laser beam34can approximate or can be greater than the width W of the glass ribbon22. In other embodiments, a configuration of the laser assembly100and/or an arrangement of the laser assembly100relative to the glass ribbon22can be such that the width WL of the elongated laser beam34is less than the width W of the glass ribbon22at the point of impingement.

The elongated laser beam34can have various energy distribution profiles along the width WL. In general terms, energy distribution profile of the elongate laser beam34exhibits a maximal intensity Imax(W) along the width WL; the width WL can be defined as the linear distance in the width direction from the point on one side of the beam having an intensity of Imax(W)·e−2to the point on the opposite side of the beam having an intensity of Imax(W)·e−2, where e is Euler's irrational number. In some embodiments, the elongated laser beam34can have a non-Gaussian energy distribution profile. For example, the elongated laser beam34can have a flat-top-mode distribution along the width WL as schematically illustrated inFIG.3B. A “flat-top-mode” means the energy intensity distribution of the laser beam along a given direction is substantially non-Gaussian and exhibits a relatively flat top as described, for example, in U.S. Pat. No. 9,302,346 the entire teaching of which are incorporated herein by reference. Other examples of energy distribution profiles useful with the present disclosure include, but are not limited to, a Gaussian energy distribution profile, a D-mode energy distribution profile, etc.

The laser assembly100can assume various forms appropriate for generating the elongated laser beam34as described above, and includes at least one laser source120. The laser source120, as an example, can comprise a high-intensity infrared laser generator such as a carbon dioxide (CO2) laser generator of a type that is available from numerous commercial sources. The wavelengths of the light produced and the power generated by CO2laser generators are variable and can be selected so that the laser beam generated is adequate to increase the temperature and decrease the viscosity of portions of a glass substrate in a viscous state, such as the glass ribbon22, sufficiently to correct thickness variations in the glass substrate. For example, a laser beam with a wavelength from approximately 9.4 micrometers to approximately 10.6 micrometers and a power output of thousands of watts can be suitable for increasing the temperature and decreasing the viscosity of portions of a glass substrate in a viscous state such as the glass ribbon22. However, because differing glass substrates will absorb laser beams to differing degrees at differing wavelengths, wavelengths outside the range of approximately 9.4 micrometers to approximately 10.6 micrometers can be employed. For example, in other embodiments useful wavelengths that can be employed range from about 1 micrometer to about 11 micrometers, with the laser beam being generated by a variety of different laser sources such as a fiber laser, a solid-state laser, a CO2laser, a quantum cascaded laser, laser diode, etc. In yet other embodiments, the laser source120comprises two or more laser generators, each configured to emit a laser beam with differing properties (e.g., different wavelengths). The combination of at least two wavelengths can facilitate more precise control of temperature across the glass substrate. For example, the elongated laser beam34can be generated as a combination of a laser beam emitted from a quantum cascaded laser generator with a wavelength of about 5 micrometers and a laser beam emitted from a CO2laser generator with a wavelength of about 10.6 micrometers, and can be capable of heating a glass substrate through the thickness thereof more uniformly as compared to a CO2laser generator-emitted laser beam alone. In this case, the quantum cascaded laser beam portion of the elongated laser beam34is absorbed by a thick layer of a glass substrate, while the CO2laser beam portion of the elongated laser beam34is completely depleted after tens of micrometers. By controlling the power ratio of the two laser generators, a variety of temperature profiles can be generated. Localized thermal profile will be able to control thermal tension and compression force in local areas, hence glass local shape can be changed. Other process variables of laser thickness control can include laser exposure time, energy peak width, energy peak height, exposed glass viscosity, laser penetration depth, and glass flow density/flow rate. For example, the control apparatus32can be arranged such that the elongated laser beam34impinges upon the glass ribbon22at a location where the glass ribbon22has a viscosity, temperature, thickness or other characteristic(s) appropriate to achieve a desired heat flux depth into the glass ribbon22. The wave length, size, exposure time, etc., of the elongated laser beam34at this selected location may more precisely create the needed viscosity gradient to achieve a desired heat profile and thus thickness change.

Regardless of an exact construction, the laser source120emits a source laser beam122. In some embodiments, a construction of the laser source120is such that the source laser beam122has a circular shape or similar shape that is not elongated. With these and related embodiments, the laser assembly100can incorporate various configurations for modifying the source laser beam122into the elongated laser beam34. For example, in some optional embodiments the laser assembly100further includes one or more optical components124arranged in the optical path of the source laser beam122. Optical components appropriate for transforming a circular beam into an elongated beam shape are known to those of ordinary skill, for example one or more cylindrical and/or aspheric lenses arranged to focus or expand a circular laser beam primarily in one axis. In one non-limiting example ofFIGS.4A and4B, the optical components124can include a cylindrical plano-concave lens130and a cylindrical plano-convex lens (e.g., a rectangular cylinder)132. The source laser beam122(emitted from the laser source120) is incident upon the cylindrical plano-concave lens130and is caused to expand (identified as an intermediate laser beam134inFIGS.4A and4B). The intermediate laser beam134is incident upon the cylindrical plano-convex lens142and is caused to further expand in primarily one direction, resulting in the elongated laser beam34.FIGS.4C-4Eprovide simplified representations of a shape of the laser beam in a plane perpendicular to the propagation direction104as formed by the optical components132(i.e.,FIG.4Cillustrates the shape of the source laser beam122prior to the cylindrical plano-concave lens130;FIG.4Dillustrates the shape of the intermediate laser beam134after the plano-concave lens130and prior to the cylindrical plano-convex lens132;FIG.4Eillustrates the shape of the elongated laser beam34after the plano-convex lens132).

Returning toFIG.2, other optical components appropriate for transforming a circular beam are also acceptable (e.g., one or more aspheric lenses). In yet other embodiments, the elongated laser beam34can be generated by a combination of two or more overlapping laser beams. Another example laser assembly140in accordance with principles of the present disclosure is shown inFIG.5. The laser assembly140includes a plurality of laser sources, such as laser sources142a,142b,142c,142d, that each emit a source laser beam (identified as144a,144b,144c,144d, respectively). The laser sources142a,142b,142c,142dare arranged relative to one another (e.g., side-by-side) and at an appropriate distance from the glass ribbon22(or other substrate) such that the source laser beams144a,144b,144c,144doverlap one another to collectively form the elongated laser beam34at the glass ribbon22. WhileFIG.5illustrates the laser assembly140as including four of the laser sources142a,142b,142c,142d, any other number, either greater or lesser, is also acceptable. With the example ofFIG.5, the plurality of laser sources can assume various forms appropriate for emitting a line-type source laser beam, such as a beam scanner (e.g., a laser source incorporating a spinning polygonal mirror that creates one long and narrow laser beam).

Returning toFIG.2, the shielding assembly102is generally configured to alter the optical intensity profile of the elongated laser beam34across the major axis110(FIG.3A) by selectively inserting the one or more shields or shielding bodies106into the optical path. With this in mind, one example of the shielding assembly102is shown in greater detail inFIGS.6A and6B. The shielding assembly102includes the one or more shields106, a housing150, one or more actuators152, and a controller154. The one or more shields106are maintained within the housing150, and are selectively maneuvered into and out of the optical path of the elongated laser beam34by a corresponding one of the actuators152. Operation of the actuators152, in turn, is controlled by the controller154. With this construction, the shielding assembly102is operable to create a desired targeted intensity profile in the elongated laser beam34as described in greater detail below.

In the non-limiting example ofFIGS.6A and6B, the one or more shields106includes first, second, third, fourth and fifth shields106a,106b,106c,106d,106e. Any other number, either greater or lesser, is equally acceptable. Where two or more of the shields106are provided, the shields106can be similar or identical in terms of size, shape and/or material(s), but need not be. Regardless, in some embodiments, each of the shields106can be a plate (e.g., a rectangular block) with a perimeter/edge shape selected such that adjacent ones of the shields106overlap one another (e.g., the second shield106boverlaps with the first and third shields106a,106c) in a manner preventing the elongated laser beam34from passing between adjacent ones of the shields106when arranged in the optical path. A material and construction of the each of the shields106is configured to partially or completely block, absorb or scatter laser beam energy. For example, each of the shields106(or at least a surface of each of the shields106positioned to face the incoming elongated laser beam34) can be formed of a metal, ceramic or composite material appropriate for blocking, absorbing or scattering laser beam energy. Further, at least a surface of each of the shields106otherwise positioned to face the incoming elongated laser beam34can have small topological features (e.g., pores, ribs, etc.) that scatter the elongated laser beam34and disperse the energy of the elongated laser beam34. In some non-limiting examples, each of the shields106(or at least a surface of each of the shields106that is otherwise positioned to face the incoming elongated laser beam34) can be formed of a closed cell or porous metal or ceramic, such as oxidized aluminum, stainless steel, titanium, silicon carbide, etc. A laser shielding material available from Kentek Corp. (Pittsfield, NH) under the trade name Ever-Guard® could be used as one or more of the shields106.

The housing150can assume various forms appropriate for housing and maintaining the shields106(and optionally the actuators152and other optional components) in an environment of the substrate being acted upon (e.g., the glass ribbon22(FIG.1)). For example, in some embodiments described in greater detail below, the housing150can be, or can be akin to, a shroud that provides thermal and/or moisture protection.

In some embodiments, a respective one of the actuators152is provided for each of the shields106. Thus,FIG.6Billustrates the shielding assembly102as including first, second, third, fourth, and fifth actuators152a,152b,152c,152d,152e, although any other number corresponding to the number of shields106is equally acceptable. In other embodiments, a single one of the actuators152can be associated with two (or more) of the shields106. Each of the actuators152can have a mechanical and/or pneumatic configuration appropriate for at least moving the corresponding shield150into and out of the optical path of the elongated laser beam34. In the non-limiting example ofFIG.6B, each of the actuators152is configured to raise and lower the corresponding shield106(e.g., the first actuator152aoperates to raise and lower the first shield106a, etc.). As a point of reference, in the view ofFIG.6B, each of the first-fifth actuators152a-152eis operating to locate the corresponding shield106a-106ein the optical path of the elongated laser beam34; in the view ofFIG.6C, the second and fourth actuators152b,152dhave been operated to lower the corresponding second and fourth shields106b,106dout of the optical path of the elongated laser beam34. In other words, in the arrangement ofFIG.6C, a portion of the elongated laser beam34is blocked or otherwise affected by the first, third and fifth shields106a,106c,106e, and other portions of the elongated laser beam34freely pass or not otherwise affected by the shielding assembly102at locations between the first and third shields106a,106c(i.e., a location of the second shield106bwere the second shield106bto have been located in the optical path) and between the third and fifth shields106c,106e(i.e., a location of the fourth shield106dwere the fourth shield106dto have been located in the optical path). In some embodiments, the shielding assembly102can be arranged such that one or more of the shields106effects a partial block of the elongated laser beam34. For example, in the exemplary arrangement ofFIG.6D, the first and fifth shields106a,106eare arranged to encompass or block an entirety of the height HL of the elongated laser beam34, the second and fourth shields106b,106dare arranged entirely outside of the elongated laser beam34(e.g., no blocking), and the third shield106cis arranged to effect a partial block of the elongated laser beam34(e.g., the third shield106cextends along a portion, but not an entirety, of the height HL).

In some optional embodiments, one or more of the actuators152is further configured to selectively rotate the corresponding shield106(e.g., motor-driven rotation, pneumatic-driven rotation, etc.). By way of further explanation,FIGS.7A and7Billustrates a single one of the shields106and a corresponding one of the actuators152in isolation, along with portion of the elongated laser beam34and the propagation direction104. A shape of the shield106defines a major plane160. In the configuration ofFIGS.7A and7B, the shield106is arranged such that the major plane160is substantially perpendicular (i.e., within 5 degrees of a truly perpendicular arrangement) to the propagation direction104. With optional embodiments in which the actuator152is further configured to selectively rotate the shield106, the shield106can be rotated to the arrangement ofFIGS.8A and8B, for example. As shown, the shield106has been rotated or arranged such that the major plane160is not substantially perpendicular to the propagation direction104and instead is at a non-perpendicular and non-parallel orientation (relative to the propagation direction104). A comparison ofFIGS.7A and7BwithFIGS.8A and8Breveals that rotating the shield106relative to the propagation direction104lessens the surface area or “size” of obstruction the shield106presents to the elongated laser beam34. In particular, when the major plane160is arranged substantially perpendicular to the propagation direction104as inFIGS.7A and7B, a region of laser beam obstruction (generally represented at162inFIG.7A) presented by the shield106to the elongated laser beam34is maximized. Rotating the shield106such that the major plane160is not substantially perpendicular to the propagation direction104as inFIGS.8A and8B, decreases a size of the region of laser beam obstruction (generally represented at162′ inFIG.8A).

Returning toFIGS.6A-6C, the controller154can be or include a computer or computer-like device (e.g., a programmable logic controller) that is electronically connected to each of the actuators152. The controller154dictates operation of each of the actuators152, and thus a position of each of the shields106relative to the optical path of the elongated laser beam34(i.e., in the optical path of the elongated laser beam34, or out of the optical path). The controller154can be programmed or can operate on programming (e.g., software, hardware, etc.) with one or more algorithms that identify a desired arrangement of the shields106as described in greater detail below. In some optional embodiments, the controller154can be electronically programmed to control operation of other components, such as the laser source120as shown inFIG.2.

Returning toFIG.2, during use the control apparatus32emits the elongated laser beam34with a targeted intensity profile onto the glass ribbon22, with the targeted intensity profile entailing one or more regions of relatively high laser energy or optical intensity, and one or more regions of no (or relatively low) laser energy or optical intensity, across the width WL of the elongated laser beam34. The region(s) of relatively high laser energy or optical intensity effect an increase in temperature and corresponding decrease in viscosity at the glass ribbon22sufficient to result in a reduction in thickness T, whereas the regions of no (or relatively low) laser energy or optical intensity do not. Thus, although an entirety of the width W of the glass ribbon22can be within the width WL (FIG.3A) of the elongated laser beam34in some embodiments, selected portions of the glass ribbon22across the width W will be subjected to the relatively high laser energy or optical intensity, whereas other portions of the glass ribbon22across the width W and within the width WL of the elongated laser beam34will not. The targeted intensity profile thus corresponds with the desired selected portions of the glass ribbon22, and is imparted into the elongated laser beam34by the shielding assembly102.

Operation of the shielding assembly102in modifying the optical intensity profile of the elongated laser beam34(as initially generated by the laser assembly100) to a targeted intensity profile is further explained with initial reference toFIG.9Athat otherwise represents the laser assembly100emitting the elongated laser beam34onto the glass ribbon22. In the representation ofFIG.9A, the shields106(FIG.6) described above are not in the optical path of the elongated laser beam34. In other words, the intensity profile of the elongated laser beam34as generated by the laser assembly100is not altered or changed prior to impinging upon the glass ribbon22.FIG.9Bis a simplified representation of the elongated laser beam34on the glass ribbon22under the scenario ofFIG.9A. Shading of the elongated laser beam34inFIG.9Brepresents laser energy being applied onto the glass ribbon22. Laser energy is applied to the glass ribbon22at all regions of the glass ribbon22within the shape of the elongated laser beam34. Returning toFIG.9A, a representation of an intensity profile170of the elongated laser beam34at the glass ribbon22is shown by a trace or plot line. The intensity profile170of the elongated laser beam34is consistent across the entire width WL of the elongated laser beam34and thus across the entire width W of the glass ribbon22. In that there are no shields or barriers in the optical path, the intensity profile170shown inFIG.9Ais the initial intensity profile of the elongated laser beam34as generated by the laser assembly100. The initial intensity profile170can have a wide flat plateau shape; and as represented inFIG.9B, this initial intensity profile170applies laser energy across the entire width W of the glass ribbon22with no interruptions.

In the illustration ofFIG.10A, one of the shields106is inserted into the elongated laser beam34via operation of the shielding assembly102(referenced generally). That is to say, the laser beam output of the laser assembly100and relationship relative to the glass ribbon22is identical inFIGS.9A and10A, but unlike the arrangement ofFIG.9A, the shield106is inserted into the optical path of the elongated laser beam34inFIG.10A. By way of non-limiting example and with reference to the example shielding assembly102ofFIGS.6B and6C, the shielding assembly102can be operated to position the third shield106cin the optical path, and withdraw the first, second, fourth and fifth shields106a,106b,106d,106efrom the optical path. Returning toFIG.10A, the shield106obstructs a portion of the elongated laser beam34(schematically represented at180inFIG.10A) as the elongated laser beam34travels in the propagation direction104(FIG.2) and impinges upon the glass ribbon22. The shield106decreases an optical intensity of a region of the elongated laser beam34such that at the glass ribbon22, the elongated laser beam34has a targeted intensity profile182. A region of reduced optical intensity is identified at184. By way of further clarification, recall that the initial intensity profile170ofFIG.9Arepresents the intensity profile of the elongated laser beam34inFIG.10Aoptically before or upstream of the shield106; a comparison of the initial intensity profile170with the targeted intensity profile182illustrates an effect of the shield106in generating the region of reduced optical intensity184. Further,FIG.10Bis a simplified representation of the elongated laser beam34on the glass ribbon22under the scenario ofFIG.10A. Shading of the elongated laser beam34inFIG.10Brepresents laser energy being applied onto the glass ribbon22; as shown, the region of reduced optical intensity184is an interruption in the optical intensity of the elongated laser beam34across the width W of the glass ribbon22.

In some embodiments, the shield106completely blocks the elongated laser beam34at the obstructed portion180.FIG.10Billustrates that under these circumstances, no laser energy impinges upon the glass ribbon22at the region of reduced optical intensity184. In other embodiments, some laser energy may pass through and/or around the shield106, with some laser energy reaching the glass ribbon22at the region of reduced optical intensity184. Regardless, the targeted intensity profile182at the glass ribbon22includes the region of reduced optical intensity184and one or more regions of elevated optical intensity (such as regions186identified inFIGS.10A and10B). The optical intensity of the elongated laser beam34is lesser at the region of reduced optical intensity184as compared to the region(s) of elevated optical intensity186. Laser energy as applied to the glass ribbon22at the region(s) of elevated optical intensity186increases the temperature and decrease the viscosity of the glass ribbon22(in a viscous state) sufficient to reduce a thickness of portions of the glass ribbon22at the region(s) of elevated optical intensity186. Conversely, laser energy, if any, applied to the glass ribbon22at the region of reduced optical intensity184is either not sufficient to increase the temperature of the glass ribbon22at the region of reduced optical intensity184, or increases the temperature and decreases the viscosity of the glass ribbon22at the region of reduced optical intensity184to a lesser extent (as compared to the region(s) of elevated optical intensity186) such that a reduction in thickness of the glass ribbon22at the region of reduced optical intensity184, if any, is less than that at the region(s) of elevated optical intensity186.

FIG.10Ais one non-limiting example of an arrangement of the shielding assembly102.FIG.11Aillustrates another possible arrangement in which the shielding assembly102(referenced generally) has been operated to insert two of the shields into the optical path of the elongated laser beam34, identified as the shields106b,106d. That is to say, the laser beam output of the laser assembly100and relationship relative to the glass ribbon22is identical inFIGS.9A and11A, but unlike the arrangement ofFIG.9A, the shields106b,106dare inserted into the optical path of the elongated laser beam34inFIG.11A. By way of non-limiting example and with reference to the example shielding assembly102ofFIGS.6B and6C, the shielding assembly102can be operated to position the second and fourth shields106b,106din the optical path, and withdraw the first, third, and fifth shields106a,106c,106efrom the optical path. Regardless, and returning toFIG.11A, the shields106b,106deach obstruct a portion of the elongated laser beam34(schematically represented at190and192, respectively, inFIG.11A) as the elongated laser beam34travels in the propagation direction104(FIG.2) and impinges upon the glass ribbon22. The shields106b,106deach decrease an optical intensity of a region of the elongated laser beam34such that at the glass ribbon22, the elongated laser beam34has a targeted intensity profile194. Corresponding first and second regions of reduced optical intensity are identified at196and198, respectively. By way of further clarification, recall that the initial intensity profile170ofFIG.9Arepresents the intensity profile of the elongated laser beam34inFIG.11Aoptically before or upstream of the shields106b,106d; a comparison of the initial intensity profile170with the targeted intensity profile194illustrates an effect of the shields106b,106din generating the regions of reduced optical intensity196,198. Further,FIG.11Bis a simplified representation of the elongated laser beam34on the glass ribbon22under the scenario ofFIG.11A. Shading of the elongated laser beam34inFIG.11Brepresents laser energy being applied onto the glass ribbon22; as shown, the regions of reduced optical intensity196,198are each an interruption in the optical intensity of the elongated laser beam34across the width W of the glass ribbon22.

The targeted intensity profile194at the glass ribbon22includes the regions of reduced optical intensity196,198and one or more regions of elevated optical intensity (such as regions200identified inFIGS.11A and11B). The optical intensity of the elongated laser beam34is lesser at the regions of reduced optical intensity196,198as compared to the region(s) of elevated optical intensity200. Laser energy as applied to the glass ribbon22at the region(s) of elevated optical intensity200increases the temperature and decreases the viscosity of the glass ribbon22(in a viscous state) sufficient to reduce a thickness of portions of the glass ribbon22at the region(s) of elevated optical intensity200. Conversely, laser energy, if any, applied to the glass ribbon22at the regions of reduced optical intensity196,198is either not sufficient to increase the temperature of the glass ribbon22, or increases the temperature and decreases the viscosity of the glass ribbon22to a lesser extent (as compared to the region(s) of elevated optical intensity200) such that a reduction in thickness of the glass ribbon22at the regions of reduced optical intensity196,198, if any, is less than that at the region(s) of elevated optical intensity200.

As previously described with respect toFIGS.7A-8B, in some embodiments the shielding assembly102can be configured to facilitate rotation of one or more of the shields106relative to the propagation direction104. With this in mind,FIG.12Aillustrates another possible arrangement of the shielding assembly102highly akin to that ofFIG.11A(i.e., the second and fourth shields106b,106dhave been interested into the optical path of the elongated laser beam34), except that the fourth shield106dhas been rotated relative to the propagation direction104. Once again, the shields106b,106deach obstruct a portion of the elongated laser beam34(schematically represented at190and210, respectively, inFIG.12A) as the elongated laser beam34travels in the propagation direction104and impinges upon the glass ribbon22. The shields106b,106deach decrease an optical intensity of a region of the elongated laser beam34such that at the glass ribbon22, the elongated laser beam34has a targeted intensity profile212. Corresponding first and second regions of reduced optical intensity are identified at196and214, respectively. A comparison ofFIGS.11A and12Areveals that by rotating the fourth shield106d, a size (relative to the width W of the glass ribbon22) of the corresponding region of reduced optical intensity214is lessened (as compared to the region of reduced optical intensity198inFIG.11A). Further,FIG.12Bis a simplified representation of the elongated laser beam34on the glass ribbon22under the scenario ofFIG.12A. Shading of the elongated laser beam34inFIG.12Brepresents laser energy being applied onto the glass ribbon22; as shown, the regions of reduced optical intensity196,214are each an interruption in the optical intensity of the elongated laser beam34across the width W of the glass ribbon22, with a size of the region of reduced optical intensity214generated by the fourth shield106dbeing less than that of the region of reduced optical intensity196generated by the second shield106b.

The targeted intensity profile212at the glass ribbon22includes the regions of reduced optical intensity196,214and one or more regions of elevated optical intensity (such as regions216identified inFIGS.12A and12B). The optical intensity of the elongated laser beam34is lesser at the regions of reduced optical intensity196,214as compared to the region(s) of elevated optical intensity216. Laser energy as applied to the glass ribbon22at the region(s) of elevated optical intensity216increases the temperature and decrease the viscosity of the glass ribbon22(in a viscous state) sufficient to reduce a thickness of the glass ribbon22at the region(s) of elevated optical intensity216. Conversely, laser energy, if any, applied to the glass ribbon22at the regions of reduced optical intensity196,214is either not sufficient to increase the temperature of the glass ribbon22, or increases the temperature and decreases the viscosity of the glass ribbon22to a lesser extent (as compared to the region(s) of elevated optical intensity216) such that a reduction in thickness of the glass ribbon22at the regions of reduced optical intensity196,214, if any, is less than that at the region(s) of elevated optical intensity216.

While the shields106have been generally illustrated as being plate-like, other constructions are also acceptable. For example, portions of another control apparatus250in accordance with principles of the present disclosure are shown inFIG.13, along with the glass ribbon22. The control apparatus250includes the laser assembly100as described above, along with a shielding assembly252. Commensurate with the descriptions above, the laser assembly100operates to emit the elongated laser beam34, and the shielding assembly252operates to decrease an optical intensity of regions of the elongated laser beam34. As a result, the elongated laser beam34has a targeted intensity profile at the point of impingement with the glass ribbon22.

The shielding assembly252includes a housing (or shroud)254and a plurality of pins256. The housing254can take any of the forms described in the present disclosure, and is generally configured for installation relative to the laser assembly100and the glass ribbon22in a manner that locates the pins256in an optical path of the elongated laser beam34. The pins256are each formed of a material that absorbs, blocks, or scatters laser beam energy as described above. The pins256can be arranged within the housing254in a grid or array-like format, for example as first and second rows258,260, all though any other number of rows (greater or lesser than two) is also acceptable. Also, the number of pins256provided in each of the rows258,260can be greater or lesser than otherwise reflected by the simplified representation ofFIG.13(e.g., as a function of a size or diameter of each of the pins256). Regardless, the pins256can be selectively manipulated relative to the optical path of the elongated laser beam34. For example, the shielding assembly252can include a shelf (not shown) or similar structure that supports each of the pins256in a manner permitting manual insertion/removal of individual ones of the pins256into/out of the housing254. Alternatively or in addition, the shielding assembly252can include one or more mechanisms (not shown) that facilitate automated movement of the pins256relative to housing254so as to selectively locate individual ones of the pins256either in or out of the optical path. By way of further explanation, each of the pins256visible in the view ofFIG.14Aare located in the optical path of the elongated laser beam34. With additional reference toFIG.13, it will be understood thatFIG.14Ashows the pins256of the first row258; the pins256of the second row260are hidden inFIG.14A. By optionally including two (or more) rows of the pins256, the ability to more completely block laser beam energy at desired regions of the elongated laser beam34can be enhanced. For example, laser beam energy that undesirably “leaks” between two immediately adjacent ones of the pins256of the first row258can be blocked, absorbed or scattered by the pins256of the second row260otherwise located immediately behind the pins256of the first row258. The two or more rows of the pins256can provide other laser beam intensity control options as described below.

During use, the pins256of the shielding assembly252can be configured to effectuate the desired targeted intensity profile.FIG.14Bprovides one possible arrangement of the shielding assembly252in which several of the pins256have been removed (from both of the first and second rows258,260(FIG.13), resulting in open segments262. The elongated laser beam34is blocked (or dissipated) by the pins256except at the open sections262. A resultant targeted intensity profile of the elongated laser beam34exiting the shielding assembly252will have regions of elevated optical intensity corresponding with the open sections262, and regions of reduced optical intensity (e.g., zero optical intensity) at regions corresponding with the pins256. The arrangement of the pins256can thus be selected to create a desired targeted intensity profile.

Another possible arrangement of the pins256is shown inFIG.15. The pins256of the first and second rows258,260have been removed at an open section264, and every other one of the pins256of the first row258has been removed at a partially open section266(e.g., the pins256of the second row260are present or not removed at the partially open section266). With this and similar constructions, an optical intensity of the elongated laser beam34is not affected or reduced by the shielding assembly252at the open section264, is partially reduced (but not completely blocked) at the partially open section266, and is substantially completely blocked at all other segments (i.e., blocked to a greater extent than at the partially open section266). A resultant targeted intensity profile of the elongated laser beam34exiting the shielding assembly252will have a region of elevated optical intensity corresponding with the open section264, a region of intermediate optical intensity corresponding to the partially open section266, and regions of reduced optical intensity (e.g., zero optical intensity) at all other location. An optical intensity of the region of optical intensity will be less than that of the region of elevated optical intensity and greater than that of the regions of reduced optical intensity. Thus, by removing some, but not all, of the pins256from the shielding assembly252in a direction perpendicular to the propagation direction104, an intensity of the elongated laser beam34can be reduced, but not eliminated entirely, in a desired manner.

Returning toFIG.1, the control apparatus32of the present disclosure can optionally include one or more additional features that further facilitate controlled thickness modifications across a width of a substrate, such as the glass ribbon22. For example, portions of another control apparatus270in accordance with principles of the present disclosure are shown in simplified form inFIG.16A, along with the glass ribbon22. The control apparatus270is akin to the control apparatus32(FIG.2), and includes the laser assembly100and the shielding assembly102(referenced generally) as described above, along with a cooling assembly272. Commensurate with the above descriptions, the laser assembly100operates to emit the elongated laser beam34, and the shielding assembly102operates to decrease an optical intensity of regions of the elongated laser beam34(such as by inserting one or more of the shields106into the optical path). As a result, the elongated laser beam34has a targeted intensity profile (represented by the trace or plot line274) at the point of impingement with the glass ribbon22. The cooling assembly272operates to direct a flow of cooling medium276onto one or more selected portions of the glass ribbon22, alternatively in a direction of the glass ribbon22but not actually impinging upon the glass ribbon22, thus extracting heat from the glass ribbon22at the selected portions as described below. As a point of clarification, the flow of cooling medium276is schematically represented inFIG.16Aand does not necessarily implicate that the elongated laser beam34is being disrupted or altered by the flow of cooling medium276.

The cooling assembly272can assume various forms appropriate for directing a cooling medium onto the glass ribbon22. For example, the cooling assembly272can include a delivery tube280and a flow controller282. The delivery tube280is generally configured for directing the flow of cooling medium276(gas such as air, liquid, etc.) in a focused pattern from a dispensing end284. For example, the delivery tube280can be a small diameter tube that may or may not carry a nozzle at the dispensing end284. The flow controller282is in fluid communication with a source (not shown) of the cooling medium (e.g., a pressurized source of air), and regulates the delivery of cooling medium from the source to the delivery tube280. In some embodiments, the cooling assembly272can further include one or more mechanisms or supports (not shown) that are operable for selectively positioning the dispensing end284relative to the glass ribbon22(e.g., increasing or decreasing a distance between the dispensing end284and the glass ribbon22, shifting the dispensing end284relative to the width W of the glass ribbon22, etc.). While the cooling assembly272is illustrated as consisting of the single delivery tube280, in other embodiments, two or more of the delivery tubes280can be provided. With these and related embodiments, a separate flow controller282can be provided for each individual delivery tube280; alternatively, two or more of the delivery tubes280can be connected to a single one of the flow controllers282. In yet other embodiments, the cooling assembly272can be arranged at an opposite side of the glass ribbon22(opposite the laser assembly100); in related embodiments, one or more cooling assemblies272can be arranged at both sides of the glass ribbon22.

During use, the elongated laser beam34is directed onto the glass ribbon22with the targeted intensity profile274. While a multitude of different targeted intensity profiles can be effectuated by the shielding assembly102, in the example ofFIG.16A, the targeted intensity profile274includes regions of reduced optical intensity290, and first, second and third regions of elevated optical intensity292,294,296. The first, second and third regions of elevated optical intensity impinge upon the glass ribbon22at first, second and third portions300,302,304, respectively. The cooling assembly272simultaneously operates to direct the flow of cooling medium276onto the glass ribbon22at the third portion304(i.e., a location corresponding with the third region of elevated optical intensity296). While the elongated laser beam34acts to raise a temperature of the third portion304of the glass ribbon22via the third region of elevated optical intensity296, the flow of cooling medium276simultaneously cools the third portion304. As a result, the increase in temperature (if any) experienced by the glass ribbon22at the third portion304is lesser as compared to the first and second portions300,302(at which the first and second regions of elevated optical intensity292,294, respectively, impinge upon the glass ribbon22), such that the decrease in viscosity (if any) and corresponding reduction in thickness (if any) of the glass ribbon22at the third portion304is also lesser as compared to the first and second portions300,302. A trace or plot line306inFIG.16Billustrates the increase in temperature across the width W of the glass ribbon22under the arrangement ofFIG.16A. As shown, the net increase in temperature at the third portion304is less than that at the first and second portions300,302due to the flow of cooling medium276. With these and similar embodiments, the cooling assembly272can operate to “fine-tune” the temperature profile at the glass ribbon22without reconfiguring the shielding assembly102.

Portions of another control apparatus310in accordance with principles of the present disclosure are shown in simplified form inFIG.17A, along with the glass ribbon22. The control apparatus310is akin to the control apparatus32(FIG.2), and includes the laser assembly100and the shielding assembly102(referenced generally) as described above, along with an intensity assembly312(referenced generally). Commensurate with the above descriptions, the laser assembly100operates to emit the elongated laser beam34, and the shielding assembly102operates to decrease an optical intensity of regions of the elongated laser beam34by inserting one or more shields into the optical path, such as the first and second shields314a,314bidentified inFIG.17A. With the non-limiting embodiment ofFIG.17A, the shielding assembly102has been configured or arranged akin to that described above with respect toFIGS.12A and12B. Further, at least the second shield314bpresents a surface (e.g., a mirror) that reflects laser beam energy.

The intensity assembly312includes a reflection body316. At least a surface of the reflection body316is formed of a material that reflects laser beam energy (e.g., a mirror). While the reflection body316is illustrated as being generally planar, other shapes or laser beam-affecting properties can be employed. The intensity assembly312can further include one or more mechanisms or supports (not shown) that are operable for selectively positioning the reflection body316relative to the shielding assembly102(e.g. toward or away from the shields, such as the second shield314b, rotating, etc.). Regardless, the intensity assembly312is configured to arrange the reflection body316so as to reflect laser beam energy directed thereon by one or more of the shields, such as the second shield314bin the arrangement ofFIG.17A, and direct the so-reflected laser beam energy at a desired portion of the glass ribbon22as generally indicated by lines318inFIG.17A.

With the above construction, the control apparatus310operates to deliver laser energy onto the glass ribbon22with a targeted intensity profile, and example of which is shown by a trace or plot line320inFIG.17A. With the non-limiting arrangement of FIG.17A (including a configuration of the shielding assembly102and the intensity assembly312), the targeted intensity profile320includes first, second and third regions of elevated optical intensity322,324,326, respectively, and regions of reduced optical intensity328(one of which is labeled inFIG.17A). As a point of reference, the targeted intensity profile320represents a combination of the elongated laser beam34(as modified by the shielding assembly102) and the reflected laser energy318. Absent the intensity assembly312, the targeted intensity profile would instead be akin to the targeted intensity profile212shown inFIG.12A. The reflected laser energy318serves to increase the intensity of the first region of elevated optical intensity322(as compared to the second and third regions of elevated optical intensity324,326). As a result, the glass ribbon22experiences a greater increase in temperature and decrease in viscosity at the portion corresponding with the first region of elevated optical intensity322as compared to the portions of the glass ribbon22at which the second and third regions of elevated optical intensity324,326impinge.FIG.17Bis a simplified representation of the laser energy on the glass ribbon22under the scenario ofFIG.17A. Shading inFIG.17Brepresents the elongated laser beam34applied onto the glass ribbon22; as shown, the regions of reduced optical intensity328are each an interruption in the optical intensity of the laser energy across the width W of the glass ribbon22.

Returning toFIG.2, in some embodiments the control apparatuses of the present disclosure can include a single laser assembly and a single shielding assembly (along with other optional features described above), such as the laser assembly100and the shielding assembly102as illustrated for the control apparatus32. In other embodiments, two or more of the laser assemblies100and a corresponding number of the shielding assemblies can be included. For example,FIG.18illustrates another embodiment control apparatus350that includes a plurality of control units352, such as first, second, third and fourth control units352a,352b,352c,352d. While four of the control units352are shown, any other number, either greater or lesser, is also acceptable. In some embodiments, each of the control units352can have a similar construction akin to one or more of the control apparatuses described in the pending disclosure, for example each including the laser assembly100and the shielding assembly102as described above (labeled for the first control unit352a). Each of the control units352operates to emit an elongated laser beam, for example elongated laser beams354a,354b,354c,354didentified inFIG.18. The control units352are arranged such that the elongated laser beams354a,354b,354c,354deach impinge upon a section of the glass ribbon22, and collectively encompass an entirety (or near entirety) of the width W of the glass ribbon22. Operation of each of the control units352(e.g., an arrangement of each of the shields or other laser blocking body associated with the corresponding shielding assembly102) can be controlled by a controller356; in other embodiments, each of the control units352can include a dedicated controller. Regardless, with the optional construction ofFIG.18, the control units352can be installed in relatively close proximity to the glass ribbon22, and the laser source120associate with each of the laser assemblies100can operate at a relatively low power setting (as compared to other embodiment control apparatuses employing an elongated laser beam from a single laser source to encompass the entire width W of the glass ribbon22).

Returning toFIG.1, the control apparatus32has been shown and described as directing the elongated laser beam34onto one side or face of the glass ribbon22(i.e., the side labeled at360inFIG.1). In other embodiments of the present disclosure, one or more additional control apparatuses can be provided that emit an elongated laser beam onto an opposite side (i.e., opposite of the side360). The control apparatuses of these alternative constructions can assume any of the forms described in the pending application, and may or may not be identical. Further, operation of the two or more control apparatuses can be dictated by a common controller, or can each have a dedicated controller.

The control apparatuses of the present disclosure can be installed relative to the substrate of interest in various fashions. With non-limiting embodiments in which the control apparatus is employed to control the thickness of a glass ribbon, additional optional components can be provided. For example,FIG.19illustrates one exemplary installation of a control system400in accordance principles of the present disclosure relative to the glass forming apparatus30described above with respect toFIG.1. Once again, the glass forming apparatus30can include the forming body50terminating at the root58and from which the glass ribbon22is drawn in the direction62. In some constructions, the glass forming apparatus30further includes an insulated housing or muffle402, and the control system400can be installed to the insulated housing402as described below.

The control system400can include a control apparatus410that can assume any of the forms described in the present disclosure. For example, the control apparatus410includes a laser assembly412and a shielding assembly414. The laser assembly412includes a laser source and optional optics adapted to generate the elongated laser beam34as described above. The shielding assembly414includes two or more laser beam shielding bodies (e.g., plates, pins, etc.), one of which is schematically shown at416. As described above, the each of the shielding bodies416is selectively located in or out of an optical path of the elongated laser beam34, for example by a corresponding actuator418as described above. Further, the shielding assembly414can include a housing or shroud420within which the shielding bodies416and the actuators418are maintained. Components associated with the laser assembly412(e.g., optics that transform a circular laser beam into an elongated laser beam, etc.) are also optionally located within the shroud420.

The control system400can include components for mounting the control apparatus410to the existing insulated housing402at a location proximate the forming body50such that the elongated laser beam34impinges upon the glass ribbon22near the root58. As a point of reference, whileFIG.19illustrates the control apparatus410arranged such that the elongated laser beam34impinges upon the glass ribbon22slightly downstream of the root58, other installation arrangement are also acceptable, including the elongated laser beam34impinging upon the glass ribbon22(or a flow of the molten glass combining into the glass ribbon22) slightly upstream of the root58. It will be understood that under normal glass forming conditions, temperatures at this optional installation location can be extremely high when producing molten glass. The control system400can include features that protect the laser assembly412and other components (e.g., the actuators418) in this high heat environment. For example, the shroud420can have an air tight construction, and includes a jacket422and a window424. The jacket422can be formed of a material exhibiting low thermal transfers, and optionally forms internal passages connected to a flow of a cooling fluid (e.g., the jacket422can be a water cooled jacket). At least the laser source of the laser assembly412can be mounted in series on the shroud420as shown. The window424is formed of a material that maintains the air tight construction of the shroud420and that is optically transparent to laser beam energy. In some non-limiting embodiments for example, the window424can be a zinc selenide (ZnSe) material.

In addition or alternatively, the control system400can further include a bracket430that connects or mounts the shroud420to the insulated housing402of the glass forming apparatus30. As a point of reference, the bracket430can be installed to a pre-existing opening432in the insulated housing402; alternatively, the opening432can be formed as part of the installation process. Regardless, the bracket430can be formed of a material differing from that of the jacket422(e.g., differing thermal transfer properties). Because the bracket430is interposed between the shroud420and the insulated housing402(i.e., the shroud420does not directly contact the insulated housing402), thermal conduction from the insulated housing402to the shroud420is limited. Conversely, to offset a possible heat sink effect (i.e., undesired loss of heat from the glass forming apparatus30due to the presence of the opening432and the control system400), the control system400can optionally include one or more active heater components434. The active heater component(s)434can assume various forms known in the art, for example a metallic heating element (such as iron-chromium-aluminum (FeCrAl) alloys, nickel-chromium (NiCr) alloys, etc.), an infrared emitter (such as a halogen infrared emitter), etc. As a point of reference,FIG.19illustrates that the glass forming apparatus30can include heaters436pre-assembled to the insulated housing402. The active heater components434of the control system400can be in addition to, and mounted to, the existing heaters436. Alternatively, the glass forming apparatus30may not have pre-existing heaters436. Regardless, the optional active heater component(s)434are mounted in the opening432and operated to mitigate the possible heat sink effect.

To mitigate condensation on the window424, the control system400can include one or more moisture control devices438, such as a replaceable silica gel cartridge or a replaceable water cooling cartridge. The moisture control device(s)438can be mounted to the bracket430in relatively close proximity to the window424. Further, the control system400can provide for purging of air in a region of the window424and moisture control device(s)438, such as by air flow passages through the bracket430.

The control system400is but one non-limiting example of the installation of the control apparatuses of the present disclosure relative to a substrate, such as the glass ribbon22. A plethora of other installation configurations are equally acceptable, and may or may not include one or more of the components described above with respect to the control system400.

Returning toFIG.2and based on the foregoing descriptions, it will be understood that, according to some aspects, a method is provided of controlling a thickness of at least one preselected portion of a substrate, such as the glass ribbon22. The method can comprise generating an elongated laser beam, effecting a targeted intensity profile into the elongated laser beam, and directed the elongated laser beam with the targeted intensity profile onto the substrate in a viscous state, wherein the thickness of the substrate at a location of the elongated laser beam is not fixed. At least one region of the targeted intensity profile possesses adequate energy to increase a temperature and reduce a viscosity of the at least one preselected portion of the substrate in the viscous state sufficiently to alter the thickness of the at least one preselected portion of the substrate. Consequently, at least one preselected portion of the substrate can be caused to attain a desired thickness. In some embodiments, two or more regions of the targeted intensity profile possess adequate energy to increase a temperature and reduce a viscosity of the substrate such that the elongated laser beam simultaneously alters the thickness of two or more preselected portions of the substrate.

FIG.20comprises a block diagram that illustrates an aspect of a method of the present disclosure of controlling a thickness of a substrate, such as the glass ribbon22. At step500, a thickness of the substrate across the width of the substrate (e.g., a thickness profile) is measured, determined or estimated. For example, and with additional reference toFIG.21that otherwise illustrates the glass ribbon22being formed at the forming body50and being drawn in the direction62, a thickness profile of the glass ribbon22across the width W of the glass ribbon22can be measured, determined or estimated at a location downstream of where the elongated laser beam (not shown) will be applied. InFIG.21, the expected location of the elongated laser beam is designated generally at550, and one possible location of the thickness measurement is designated generally at552. In some embodiments, a thickness measurement trace can be carried out on the glass ribbon22for the purpose of identifying thickness non-uniformities that are present in the glass ribbon22. Also by way of example, the thickness profile of the glass ribbon22can be monitored in real time as the glass ribbon22is produced. The monitoring or determination of the thickness of the glass ribbon22can be accomplished with various techniques known in the art, such as interference measurement, chromatic confocal measurement, white light topography, white light interferometry, etc. Where the substrate in question is a material other than a glass ribbon, other thickness measurement techniques can alternatively be employed that are appropriate for the particular composition and/or format of the substrate.

The so-determined thickness trace or profile is signaled to the controller154(FIG.2) at step502. The controller154can be programmed to analyze the thickness profile. In some embodiments, any segments of elevated thickness in the thickness profile can be identified (e.g., a thickness exceeding a pre-determined absolute value; a thickness at one segment that exceeds the thickness at other segments by a pre-determined value or percentage, etc.), and the location (and optionally the size) of the identified segment(s) can be correlated with an area or areas of the glass ribbon22across the width W of the glass ribbon22. By way of non-limiting example, a hypothetical thickness trace or profile554generated at the measurement location552is shown inFIG.21. The thickness trace554terminates at a start point556and an end point558. The thickness trace554can be interpreted as exhibiting segments of acceptable thickness560, and first and second segments of elevated thickness562,564. As a point of reference, the start point556corresponds with a first edge570of the glass ribbon22, and the end point558corresponds with an opposing, second edge572. The first and second segments of elevated thickness562,564in the thickness trace554correspond with first and second targeted areas574,576(drawn with imaginary lines inFIG.21) across the width W of the glass ribbon22(e.g., where the first segment of elevated thickness562initiates 10 millimeters (mm) from the start point556, the first targeted areas574initiates 10 mm from the first edge570in the direction of the width W). Based on the above analyses, the first and second targeted areas574,576can be designated or selected as benefitting from a reduction in thickness. All other areas of the glass ribbon22across the width W (i.e., other than the first and second targeted areas574,576) can be designated or selected as not requiring a reduction in thickness.

At step504, the controller154operates to configure the shielding assembly in accordance with the identifications made at step502. By way of non-limiting example and with additional reference to the exemplary shielding assembly102ofFIGS.6A-6C, the serial arrangement of the shields106a-106ecan correlate with the width W of the glass ribbon22, including the first shield106acorresponding with the first edge570(i.e., presence or absence of the first shield106ain the optical path of the elongated laser beam34will affect an optical intensity of the elongated laser beam34at the first edge570), and the fifth shield106ecorresponding with the second edge572. Because the shields106a-106ehave given or known dimensions, a relationship of each of the shields106a-106erelative to a corresponding portion of the glass ribbon22across the width W can be determined. Additionally or alternatively, a correlation of each of the shields106a-106erelative to the measured thickness profile or trace is also known or can be determined. For example,FIG.22illustrates a relationship between the shields106a-106eand the thickness trace554; as shown, each of the shields106a-106ecorresponds with a different segment of the thickness trace554. From one or both of these relationships, a determination can then be made as to how the shields106a-106eshould be arranged relative to the optical path in order to effectuate a thickness reduction at selected portions of the glass ribbon22. Continuing the above hypothetical, and returning toFIGS.6A-6C and21, it can be determined that relative to the width W of the glass ribbon22, the second shield106bcorresponds with the first targeted area574, and the fourth shield106dcorresponds with the second targeted area576. Alternatively or in addition, it can be determined that relative to the thickness trace554, the second shield106bcorresponds with the first segment of elevated thickness562, and the fourth shield106dcorresponds with the second segment of elevated thickness564. Based on one or both of these determinations, the shielding assembly102is configured at step504(e.g., the controller154operates the actuators152) such that the second and fourth shields106b,106dare removed from the optical path, and the first, third and fifth shields106a,106c,106eare inserted into the optical path (i.e., the arrangement ofFIG.6C).

At step506, the control apparatus is operated to emit the elongated laser beam34with a targeted intensity profile onto the glass ribbon22. The targeted intensity profile is dictated by the shielding assembly as configured at step504. Continuing the above hypothetical, the elongated laser beam34is shown as impinging upon the glass ribbon22inFIG.23. The targeted intensity profile of the elongated laser beam34is represented by a trace580, and includes a first region of elevated intensity582, a second region of elevated intensity584, and regions of reduced intensity586(e.g., minimal or zero laser beam energy). The first and second regions of elevated intensity582,584are also schematically shown in the depiction of the elongated laser beam34. The first and second regions of elevated intensity582,584correspond with the first and second targeted areas574,576, respectively, relative to the width W of the glass ribbon22. In other words, a location of the first region of elevated intensity582relative to the first edge570(or any other point of reference along the width W) can be the same as a location of the first targeted area574relative to the first edge570, and a location of the second region of elevated intensity584relative to the first edge570can be the same as a location of the second targeted area576. At the remaining regions586of the targeted intensity profile580, an optical intensity of the elongated laser beam34at the glass ribbon22is minimal or zero (i.e., where the elongated laser beam34has been blocked by the first, third and fifth shields106a,106c,106e). As a result, laser beam energy sufficient to raise a temperature and reduce a viscosity of the glass ribbon22is applied at selected portions of the glass ribbon22that otherwise correspond with the first and second targeted areas574,576.

More particularly, a laser beam zone590can be designated along the glass ribbon22and at which the elongated laser beam34is applied. The laser beam zone590encompasses the entire width W of the glass ribbon22, and can be considered as comprising a series of consecutive portions from the first edge570to the second edge572. By way of further explanation,FIG.24identifies hypothetical first, second, third, fourth and fifth portions592-600extending in the direction of the width W across the laser beam zone590. With reference betweenFIGS.23and24, impingement of the elongated laser beam34on the glass ribbon22can be described as including the first region of elevated intensity582being aligned with and applying laser energy to the second portion594, the second region of elevated intensity584being aligned with and applying laser to the fourth portion598, and the regions of reduced intensity586being aligned with respective ones of the first, third and fifth portions592,596,600. It will be understood that in some embodiments, the regions of reduced intensity586are characterized by the complete absence of any laser energy or laser power; under these circumstances, no laser energy is applied to the first, third and fifth portions592,596,600. The illustration of the elongated laser beam34inFIG.23schematically reflects this scenario. In other embodiments, some minimal level of laser energy may be applied. Regardless, with the example ofFIGS.23and24, the second and fourth portions594,598constitute portions of the glass ribbon22preselected to receive laser beam energy sufficient to raise a temperature and reduce a viscosity of the glass ribbon22. The reduction in viscosity can result in a reduction in thickness at the preselected portions594,598. The remaining portions592,596,600of the laser beam zone590do not receive laser beam energy sufficient to raise a temperature and reduce a viscosity of the glass ribbon22in response to application of the elongated laser beam34onto the glass ribbon22.

It will be understood that the above hypothetical is but one of a plethora of different substrate thickness non-uniformity scenarios that can be addressed or controlled by the methods and apparatuses of the present disclosure. In more general terms, a targeted intensity profile appropriate for addressing a particular thickness profile across the width W of the glass ribbon22can be imparted into the elongated laser beam34by a corresponding arrangement of the shielding assembly. In this regard, a resolution or precision of the size and location (relative to the width W) of the region(s) of elevated intensity in the targeted intensity profile can be a function of the number, size and spatial articulation of the shields provided with the shielding assembly. Regardless, the elongated laser beam34can remain stationary relative to the glass ribbon22. With embodiments in which the glass ribbon22(or other substrate) is moving, such as when the glass ribbon22is being continuously drawn in the direction62, the area of the glass ribbon22acted upon by the elongated laser beam34will eventually reach the location552at which thickness is being measured. The corresponding, updated thickness trace may no longer exhibit segments of elevated thickness. In other scenarios, the updated thickness trace may exhibit one or more segments of elevated thickness. The controller154(or other computer controlling operation of the controller154) can continuously receive the updated thickness traces and can be programmed to operate an appropriate closed-loop control algorithm to effect a new configuration of the shielding assembly, and thus a new targeted intensity profile in the elongated laser beam34.

While the methods ofFIG.20implicate automated control over an arrangement of the shields provided with the shielding assembly. In other embodiments, an operator can manually arrange the shields based upon, for example, thickness information. Regardless, the control apparatuses and methods of the present disclosure are well-suited for addressing thickness non-uniformities in a substrate, such as part of the production of a glass ribbon in a draw operation (or other glass ribbon formation techniques).

For example,FIG.25presents the results of a simulation in which an elongated laser beam with a targeted intensity profile impinges upon a glass ribbon (or “sheet”) with thickness non-uniformities. Thickness plot line610represents the thickness of the glass ribbon at various locations across the width. As a point of reference, the “Position on Sheet” axis inFIG.25presents incremental distances from an edge of the glass sheet in the width direction, starting with a location 1500 mm from the edge and ending at a location 1900 mm from the edge. In the representation ofFIG.25, the thickness plot line610shows that prior to the application of the elongated laser beam, the glass ribbon has one area of elevated thickness between approximately 1650 mm and approximately 1710, and another area of elevated thickness initiating at approximately 1800 mm. The simulation assumed that an elongated laser beam could be applied to the glass ribbon, and arranged such that a left-most outer extent of the elongated laser beam would impinge on the glass ribbon at a location of approximately 1585 mm, and a right-most outer extent of the elongated laser beam would impinge on the glass ribbon at a location of approximately 1825 mm (i.e., the elongated laser beam has a width of approximately 240 mm). It was further assumed that a laser energy density of the elongated laser beam was sufficient to raise the temperature of the glass by 7 degrees Celsius (° C.), and that a temperature of the thickest part of the thickness profile of the glass ribbon can be raised by 4° C. in order to effect a change in thickness approximately matching the thinnest part of the thickness profile. To simulate shielding of portions of the elongated laser beam, the glass ribbon was divided into 5 mm sections that were either open or closed to the incident energy of the elongated laser beam. Sections closed to the incident energy (i.e., representing portions of the elongated laser beam that were blocked by a shield) are identified at612; sections open to the incident energy (i.e., representing portions of the elongated laser beam that impinged upon the glass ribbon) are identified at614. The glass ribbon did not experience a temperature change at the closed sections612, and experienced a 7° C. temperature increase at the open sections614. By patterning the closed and open sections612,614as shown, the simulation generated an effective temperature change across a portion of the width of the glass ribbon, represented by temperature change plot line616. As shown, the temperature change plot line616mimics the corresponding region of the thickness plot line610, illustrating that an elongated laser beam distributing uniform energy density across the glass ribbon can be intermittently “blocked” so as to create a temperature change profile that will act to cancel existing thickness non-uniformities.

From the foregoing explanations, it is expected that glass manufacturing systems (e.g., downdraw glass forming apparatus) implementing the control apparatuses and methods of the present disclosure when utilized with the manufacture of glass are capable of producing glass with a thickness uniformity of less than 1 micrometer deviation in thickness over 100 mm distance.

Various modifications and variations can be made to the embodiments described herein without departing from the scope of the claimed subject matter. Thus it is intended that the specification cover the modifications and variations of the various embodiments described herein provided such modifications and variations come within the scope of the appended claims and their equivalents.