WO2009070262A1

WO2009070262A1 - Method of and apparatus for detecting change in shape of a moving substrate

Info

Publication number: WO2009070262A1
Application number: PCT/US2008/013060
Authority: WO
Inventors: Shawn R Markham
Original assignee: Corning Incorporated
Priority date: 2007-11-30
Filing date: 2008-11-24
Publication date: 2009-06-04
Also published as: TW200938830A; CN101910782B; JP5906288B2; JP2011505559A; CN101910782A; KR101529744B1; KR20100116579A; JP5654354B2; JP2015014608A; TWI385378B

Abstract

A method is disclosed for detecting a change in shape of a continuous substrate, the method comprising providing a continuous substrate continuously moving through a measurement zone, providing an optical position sensor in optical communication with at least a portion of the measurement zone, irradiating at least a portion of the continuous substrate within at least a portion of the measurement zone with laser radiation and detecting a reflection of the laser radiation, and then determining a distance between the irradiated portion of the continuous substrate and the optical position sensor.

Description

METHOD OF AND APPARATUS FOR DETECTING CHANGE IN SHAPE OF A MOVING SUBSTRATE

CLAIM OF PRIORITY

[0001] This application claims priority to co-pending and commonly assigned U.S. Patent Provisional Application Serial No. 61/004,782, filed November 30, 2007, for METHOD FOR DETECTING CHANGE IN SHAPE OF A MOVING SUBSTRATE.

FIELD OF THE INVENTION

[0002] The present invention relates to a measuring device, and more particularly, to an apparatus and method for measuring changes in shape of a planar material.

TECHNICAL BACKGROUND

[0003] The fusion process is one of the basic techniques used to produce sheet glass and can produce sheet glass having surfaces with superior flatness and smoothness relative to sheet glass produced by alternative processes, such as for example, the float and slot drawn processes. As a result, the fusion process has found advantageous use in the production of glass substrates used in, for example, the manufacture of light emitting displays, such as liquid crystal displays (LCDs).

[0004] The fusion process, specifically, the overflow downdraw fusion process, includes a supply pipe which provides molten glass to a collection trough formed in a refractory body known as an isopipe. During the overflow downdraw fusion process, molten glass passes from the supply pipe to the trough and then overflows the top of the trough on both sides, thus forming two sheets of glass that flow downward and then inward along the outer surfaces of the isopipe. The two sheets meet at the bottom or root of the isopipe, where they fuse together into a single ribbon of glass. The single ribbon is then fed to drawing equipment that controls the thickness of the sheet by the rate at which the sheet is drawn away from the root. The drawing equipment is located well downstream of the root so that the single ribbon has cooled and become rigid before coming into contact with the equipment. The outer surfaces of the final glass ribbon do not contact any part of the outside surface of the isopipe during any part of the process. In this way, the superior properties of the outer surfaces of the final sheet are achieved.

[0005] As the glass ribbon travels from the isopipe and through a setting zone, changes in the shape of the glass ribbon can occur. Such changes in shape can result in a final glass sheet having, for example, high stress, or an out of plain distortion, such as a bow. Glass having, for example, high stress and/or out of plain distortions is typically discarded, resulting in wasted product and added manufacturing cost.

[0006] To detect changes in shape of the glass ribbon, conventional glass manufacturing systems utilize either intermittent off-line destructive product quality checks to detect out of plain sheet distortions, and/or temperature sensors, such as thermocouples, positioned close to the glass ribbon. The off-line shape measurement device is destructive therefore making 100% sampling ineffective. In a thermocouple system, a shape change resulting in a distortion such as a bow, in the glass ribbon can cause the position of the hot glass ribbon to change with respect the temperature sensor. The response of the thermocouples is slower than the optical sheet position sensors therefore changes in shape that occur rapidly and subsequently reverse are not identifiable with the air temperature readings. The thermocouples can also produce false positives. The temperature alarm limits may be activated by short term air flow or glass flow changes when there was no change in glass position.

[0007] Thus, there is a need to address the aforementioned problems and other shortcomings associated with the traditional approaches to detecting changes in the shape of a glass ribbon. These needs and other needs are satisfied by the position sensor technology of the present invention.

SUMMARY

[0008] The present invention relates to a measuring device, and more particularly, to an apparatus and method for measuring changes in shape of a planar material. The present invention addresses at least a portion of the problems described above through the use of a position sensor used, for example, to detect the position of one or more portions of a glass ribbon, and thus, detect a change in shape.

[0009] In a first detailed aspect, the present invention provides a method for detecting a change in shape of a continuous substrate, the method comprising irradiating with laser radiation at least a portion of a continuous substrate within at least a portion of a measurement zone, detecting on an optical position sensor at least a portion of a reflection of the laser radiation, and then determining a distance between the irradiated portion of the continuous substrate and the optical position sensor, and then comparing the distance to a predetermined value, a difference in which indicates a change in shape of the continuous substrate. [0010] Additional aspects and advantages of the invention will be set forth, in part, in the detailed description and any claims which follow, and in part will be derived from the detailed description or can be learned by practice of the invention. The advantages described below will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several aspects described below. Like numbers represent the same elements throughout the figures.

[0012] FIG. 1 is a schematic diagram illustrating a representative construction for an isopipe for use in an overflow downdraw fusion process for making sheet glass, in accordance with one aspect of the present invention.

[0013] FIG. 2 is an exemplary schematic of an optical position sensor and a substrate, in accordance with various aspects of the present invention.

[0014] FIG. 3 is a schematic diagram illustrating a position sensor configured so as to direct laser radiation (dashed line) in a direction normal to the surface of a glass ribbon having a bow, in accordance with various aspects of the present invention. The arrow indicates the direction of glass travel during the forming process.

[0015] FIG. 4 is a schematic diagram illustrating a position sensor configured so as to direct laser radiation (dashed line) in a direction normal to the surface of a glass ribbon, in accordance with various aspects of the present invention. The arrow indicates the direction of glass travel during the forming process.

[0016] FIG. 5 is a graph illustrating the stress profile of the top edge of consecutive samples of a continuous glass substrate collected during a shape change using an optical position sensor, in accordance with various aspects of the present invention.

[0017] FIG. 6 is a graph illustrating the stress profile of the top edge of consecutive samples of a continuous glass substrate collected using conventional thermocouple alarms. DETAILED DESCRIPTION

[0018] The present invention can be understood more readily by reference to the following detailed description, examples, and claims, and their previous and following description. However, before the present compositions, articles, devices, and methods are disclosed and described, it is to be understood that this invention is not limited to the specific compositions, articles, devices, and methods disclosed unless otherwise specified, as such can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting. [0019] The following description of the invention is provided as an enabling teaching of the invention in its currently known embodiments. To this end, those skilled in the relevant art will recognize and appreciate that many changes can be made to the various aspects of the invention described herein, while still obtaining the beneficial results of the present invention. It will also be apparent that some of the desired benefits of the present invention can be obtained by selecting some of the features of the present invention without utilizing other features. Accordingly, those who work in the art will recognize that many modifications and adaptations to the present invention are possible and can even be desirable in certain circumstances and are a part of the present invention. Thus, the following description is provided as illustrative of the principles of the present invention and not in limitation thereof. [0020] Disclosed are materials, compounds, compositions, and components that can be used for, can be used in conjunction with, can be used in preparation for, or are products of the disclosed method and compositions. These and other materials are disclosed herein, and it is understood that when combinations, subsets, interactions, groups, etc. of these materials are disclosed that while specific reference of each various individual and collective combinations and permutation of these compounds may not be explicitly disclosed, each is specifically contemplated and described herein. Thus, if a class of substituents A, B, and C are disclosed as well as a class of substituents D, E, and F and an example of a combination embodiment, A-D is disclosed, then each is individually and collectively contemplated. Thus, in this example, each of the combinations A-E, A-F, B-D, B-E, B-F, C-D, C-E, and C- F are specifically contemplated and should be considered disclosed from disclosure of A, B, and C; D, E, and F; and the example combination A-D. Likewise, any subset or combination of these is also specifically contemplated and disclosed. Thus, for example, the sub-group of A-E, B-F, and C-E are specifically contemplated and should be considered disclosed from disclosure of A, B, and C; D, E, and F; and the example combination A-D. This concept applies to all aspects of this disclosure including, but not limited to any components of the compositions and steps in methods of making and using the disclosed compositions. Thus, if there are a variety of additional steps that can be performed it is understood that each of these additional steps can be performed with any specific embodiment or combination of embodiments of the disclosed methods, and that each such combination is specifically contemplated and should be considered disclosed.

[0021] hi this specification and in the claims which follow, reference will be made to a number of terms which shall be defined to have the following meanings:

[0022] As used herein, the singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a "compound" includes aspects having two or more such compounds, unless the context clearly indicates otherwise.

[0023] "Optional" or "optionally" means that the subsequently described event or circumstance can or cannot occur, and that the description includes instances where the event or circumstance occurs and instances where it does not. For example, the phrase "optionally substituted component" means that the component can or can not be substituted and that the description includes both unsubstituted and substituted aspects of the invention.

[0024] Ranges can be expressed herein as from "about" one particular value, and/or to

"about" another particular value. When such a range is expressed, another aspect includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0025] As briefly introduced above, the present invention provides for a method for detecting a change in shape of, for example, a glass ribbon. The present invention also provides a system for detecting a change in shape of a glass ribbon during, for example, the glass manufacturing process, through the use of an optical position sensor.

[0026] In a conventional overflow downdraw fusion process for the manufacture of sheet glass, molten glass is allowed to overflow a trough and form a continuous ribbon of glass.

With reference to FIG. 1, a conventional isopipe and sheet glass manufacturing system comprises a supply pipe 9 that provides molten glass to a collection trough 11 formed in a refractory body 13 known as an isopipe. During operation, molten glass can flow from the supply pipe to the trough where it can overflow the top of the trough of both sides, forming two sheets of glass that flow downward and then inward along the outer surfaces of the isopipe. The two sheets meet at the bottom or root 15 of the isopipe where they can fuse together into a single ribbon. The single ribbon is then fed to drawing equipment (represented by arrows 17), which controls the rate at which the ribbon is drawn away from the root, and thus, the thickness of the sheet. The drawing equipment is typically positioned downstream of the root such that the formed sheet glass has sufficiently cooled and become rigid before contacting the equipment. It should be noted that the methods and systems of the present invention can be used with any manufacturing process wherein a continuous ribbon of a planar material is formed, and the present invention is not intended to be limited to an overflow downdraw fusion process for manufacturing sheet glass.

[0027] The glass forming process can be tailored to produce glass having a variety of shapes and magnitudes. In one aspect, a glass forming process can produce sheet glass that is planar. In another aspect, a glass forming process can produce sheet glass having a specific feature, such as a bow or curve. Changes in the shape of a glass ribbon, such as, for example, when the glass passes through a setting zone located between the isopipe and the drawing equipment, can result in stress and glass breakage. Shape changes can vary in type and magnitude. In one aspect, a shape change represents the formation of a bow from a planar substrate. In another aspect, a shape change represents a flattening or further bowing of a bow. hi another aspect, a shape change represents a distortion, such as a twist or flex, in a glass ribbon. The magnitude of a shape change, and the significance and/or stress resulting therefrom can vary. In various aspects, a shape change can represent a change in, for example, a distance from the optical position sensor to the substrate of from about 10 μm to about 50,000 μm or more, for example, about 10, 20, 40, 80, 100, 200, 400, 600, 1,000, 2,500, 3,500, 5,000, 7,500, 9,000, 10,000 , 20,000, 30,000, 40,000, 50,000 μm or more. In other aspects, a shape change can represent a deviation from a predetermined value of the distance between the optical position sensor and the substrate. In other aspects, a shape change can be less than about 10 μm or greater than about 50,000 μm. [0028] Off-line product quality checks can provide information to quantify the quality of one or more portions of glass when the glass ribbon is stable. Stable, as used herein, is intended to refer to glass that continuously maintains the same position and shape throughout the setting zone of a glass forming process. When the ribbon shape changes while traveling through the setting zone, those shape changes can be formed into the glass sheet, resulting in stress. In a downstream process, differences in glass shape from one piece to another can cause product quality problems. [0029] To detect changes in shape of the glass ribbon, conventional glass manufacturing systems utilize either intermittent off-line destructive product quality checks to detect out of plain sheet distortions, and/or temperature sensors, such as thermocouples, positioned close to the glass ribbon. Off-line shape measurement techniques are destructive and thus, unable to effectively sample substantial portions of produced sheet glass. In a thermocouple system, a shape change resulting in a distortion such as a bow, in the glass ribbon can cause the position of the hot glass ribbon to change with respect the temperature sensor. While thermocouple systems can detect changes in glass position and hence, changes in the shape of a glass ribbon, thermocouple systems suffer from limited sensitivity, environmental errors, and slow response times. Further, thermocouple systems can produce false positive results with changes in glass flow, airflow, or environmental conditions adjacent to the glass ribbon and/or the thermocouple, hi addition, the slow response time typical for thermocouple systems will not detect changes in shape that occur rapidly and subsequently reverse. [0030] The present invention provides a method of detecting changes in shape of a continuously moving planar substrate, such as a glass ribbon, through the use of an optical position sensor, hi one aspect, the optical position sensor of the present system can be used to identify isolated changes in the shape of a substrate that are not detectable by conventional shape identification tools, such as a thermocouple system or intermittent off-line destructive product quality checks. In another aspect, the optical position sensor of the present invention can be used to detect transient changes in shape that occur rapidly during, for example, the glass manufacturing process.

[0031] The optical position sensor of the present invention can direct laser radiation onto a portion of a continuously moving substrate, such as a glass ribbon formed in the overflow downdraw fusion process, and detect onto, for example, a photodiode detector, a reflected portion of the laser radiation, hi one aspect, the laser radiation directed onto the substrate does not track the movement of the substrate. In another aspect, the portion of a continuously moving substrate onto which laser radiation is directed changes at about the same rate which the substrate is moving relative to the optical position sensor, hi one aspect, the laser radiation is directed on at least a portion of the substrate positioned within a measurement zone, hi a glass forming process, the measurement zone can, in various aspects, comprise the area from the root of an isopipe to the drawing equipment in which the glass ribbon travels. In other aspects, laser radiation can be directed onto a portion of the continuous substrate that is within or downstream of a setting zone of, for example, a glass manufacturing process. [0032] The optical position sensor can then determine the distance between the irradiated portion of the continuously moving substrate and the optical position sensor, and thus, determine the relative position of at least the irradiated portion of the substrate. In one aspect, the optical position sensor can detect at least a portion of a reflection of the laser radiation incident upon the substrate, determine a distance between the irradiated portion of the substrate and the optical position sensor, and then compare the distance to a predetermined value, a difference in which can indicate a change in the shape of at least a portion of the substrate. In one aspect, the optical position sensor can determine the relative position of the irradiated portion of a glass sheet onto which the laser radiation is directed. In another aspect, the optical position sensor can determine the relative position of a glass sheet or a portion thereof at a specific location in the glass forming process. [0033] The optical position sensor of the present invention can also provide a signal to indicate that a given portion of glass will have a different shape relative to other portions of the glass ribbon. In one aspect, the optical position sensor can be used to trigger an alarm to identify one or more portions of glass that, once cut from the ribbon, can be removed for further testing, discarded, or recycled. In another aspect, the optical position sensor can provide a signal to a control system that can automatically cut and remove a portion of glass from, for example, a glass ribbon, hi yet another aspect, the optical position sensor has a response time sufficient to allow detection and identification of a single piece of glass that is subsequently cut from a continuous glass ribbon.

[0034] The optical position sensor can provide, during a glass forming process, a continuous stream of data regarding the position of a glass ribbon to an optional control system. The control system, if utilized, identify a shape change and indicate that one or more individual glass sheets should be removed or subjected to further testing. [0035] The optical position sensor of the present invention can provide a cost effective method to quickly and accurately measure the distortion of one or more locations on a substrate, such as, for example, a planar glass ribbon. Moreover, since the optical position sensor of the present invention can remain in a fixed position during the course of a measurement and/or during the glass forming process, the position sensor system can be stable and robust. In one aspect, the optical position sensor is not subject to errors, such as false positive readings, from changes in glass flow, airflow, and/or environmental conditions adjacent to the glass ribbon and/or the position sensor.

[0036] The optical position sensor of the present invention can comprise any suitable optical equipment capable of determining the position and/or a change in position of an object in optical communication therewith. In various aspects, the optical position sensor is a distance sensor, a displacement sensor, a position sensor, or a combination thereof. In a specific aspect, the optical position sensor is a laser rangefinder, such as, for example, an Acuity AccuRange 4000 laser rangefinder, available from Schmitt Measurement Systems, Inc., Portland, Oregon, USA.

[0037] The optical position sensor can be configured to emit radiation in any suitable form that can be detected and detect, for example, a position change, in accordance with the various aspects of the present invention. In one aspect, the optical position sensor emits laser radiation. In a specific aspect, the optical position sensor emits laser radiation having a wavelength of about 780 nm. The specific wavelength and/or intensity of radiation emitted by an optical position sensor can vary, and the present invention is not intended to be limited to any particular wavelength and/or intensity of radiation.

[0038] The operation and detection methods of a particular optical position sensor can vary, depending on the specific equipment employed, and the present invention is not limited to the use of any particular equipment and/or theory of operation. In one aspect, a laser position sensor can utilize a time of flight method, wherein the amount of time a beam of light takes to travel to and from a target, such as, for example, a substrate, is determined. In such an exemplary aspect, as depicted in FIG. 2, a radiation source 22, such as, for example, a laser diode, can emit laser radiation (dashed line) in the direction of a substrate 10, as indicated by the arrows in FIG. 2. A portion of the light reflected from the substrate 10 can be collected using a lens 26, which can focus the collected laser radiation reflected from the substrate onto a detector 28, such as a photodiode detector.

[0039] In other aspects, an optical position sensor can comprise other optical and/or electronic components, such as, for example, band pass filters, that can improve the accuracy of measurements. In yet other aspects, the environment in which an optical position sensor is placed and operated can be controlled so as to limit ambient light that could interfere with and/or limit detection and/or accuracy of the optical position sensor. [0040] The optical position sensor can, in various aspects, detect position changes of about 100 μm or greater, for example, about 100, 200, 250, 300, 500, 800, 1,000, 3,000, 5,000, 8,000, 10,000, 15,000, 20,000, 25,000, 30,000, 35,000, 40,000, 45,000, 50,000 μm, or more. The detection range of a particular optical position sensor can vary and can be less than or greater than the expected and/or typical change in shape of a substrate in a given manufacturing process. In another aspect, the detection range of an optical position sensor is greater than the expected range of movement of a substrate. [0041] The optical position sensor of the present invention can be positioned in any location or configuration suitable for use in detecting a distortion or change in the shape of at least a portion of a substrate such as, for example, a glass ribbon. In one aspect, the optical position sensor is positioned so as to direct laser radiation in a direction substantially normal to the surface of a glass ribbon. FIG. 3 illustrates an exemplary schematic wherein an optical position sensor 20 is positioned to direct laser radiation towards a bowed glass ribbon 10 in a direction normal to the surface of the glass ribbon. FIG. 4 illustrates an exemplary schematic wherein an optical position sensor 20 is positioned to direct laser radiation towards a planar glass ribbon 10 in a direction normal to the surface of the glass ribbon. In another aspect, the optical position sensor is positioned so as to direct laser radiation at an angle, for example, from about 15° to about 165° relative to the plane of the substrate. In yet another aspect, the optical position sensor is positioned so as to direct laser radiation at an angle, for example, from about 75° to about 105° relative to the plane of the substrate. If an optical position sensor is configured and/or positioned so as to direct laser radiation towards a substrate at an angle, the laser, can, in various aspects, be separated from the detector, so as to detect a specular reflection or a substantial portion thereof of the laser radiation reflected from the substrate. When the optical position sensor is positioned normal to or substantially normal to the plane of the substrate, the laser and detector of the optical position sensor can be positioned in various arrangements, such as, for example, adjacent to each other or concentrically positioned as illustrated in FIG. 2. In a preferred aspect, the laser and detector are positioned are concentrically positioned at an angle of about 90° ± 1.5° relative to the plane of the substrate.

[0042] The optical position sensor of the present invention can be positioned at any distance from the substrate suitable for the optical position measuring technique. In various aspects, the optical position sensor is positioned from about 6 inches to about 600 inches (50 feet) or more, for example, about 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 12, 15, 20, 30, 40, 50, 75, 80, 100, 120, 140, 160, 180, 200, 225, 250, 275, 300, 325, 350, 375, 400, 450, 500, 550, or 600 inches or more from the substrate; preferably from about 6 to about 36 inches, for example, about 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 12, 15, 20, 30, 34, or 36 inches from the substrate; or more preferably from about 8.5 to about 9.5 inches, for example, about 8.5, 8.75, 9, 9.25, or 9.5 inches from the substrate.

[0043] Depending on the specific environmental conditions in which an optical position sensor is used, thermal controls and/or insulation can be provided to maintain a suitable operating environment for the optical position sensor. In various aspects, an optical position sensor positioned in a glass manufacturing process can be cooled via air and/or water so as to maintain the operating environment of the sensor in accordance with the design specifications and tolerances for the equipment. As specific equipment designs and tolerances can vary, the thermal controls and methods can also vary depending upon the specific equipment used and the intended application and environmental conditions thereof, hi one aspect, the optical position sensor is positioned so as to maximize accuracy and limit interference from, for example thermal noise.

[0044] The optical position sensor of the present invention can comprise one or multiple individual position sensors, hi one aspect, the optical position sensor comprises a single position sensor configured to detect a position and/or shape change at a single location on a glass ribbon, hi another aspect, the optical position sensor comprises two position sensors configured so as to detect position and/or shape changes at separate discrete locations on a glass ribbon, hi other aspect, the optical position sensor can comprise 3, 4, 5, or more individual position sensors configured to detect position and/or shape changes at multiple individual locations on a glass ribbon. If multiple position sensors are utilized, each of the multiple position sensors can be positioned on either the same side or an opposing side of, for example, a glass ribbon. In one aspect, two optical position sensors are employed and are positioned at separate locations on the same side of a glass ribbon, hi another aspect, two optical position sensors are employed and are positioned at separate location on opposing sides of a glass ribbon.

[0045] Although several aspects of the present invention have been described in the detailed description, it should be understood that the invention is not limited to the aspects disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the spirit of the invention as set forth and defined by the following claims.

EXAMPLES

[0046] To further illustrate the principles of the present invention, the following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how the compositions, articles, devices, and methods claimed herein are made and evaluated. They are intended to be purely exemplary of the invention and are not intended to limit the scope of what the inventors regard as their invention. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperatures, etc.); however, some errors and deviations should be accounted for. Unless indicated otherwise, temperature is °C or is at ambient temperature, and pressure is at or near atmospheric. There are numerous variations and combinations of process conditions that can be used to optimize product quality and performance. Only reasonable and routine experimentation will be required to optimize such process conditions.

Example 1 - Comparison of Optical Position Sensor and Thermocouple Detection of Shape Change

[0047] In a first example, an optical position sensor was compared to a conventional thermocouple system for detecting shape changes in a continuous glass substrate formed by an overflow downdraw fusion process. A series of consecutive measurement samples were acquired, each sample comprising multiple individual measurements across the surface of the glass. FIG. 5 illustrates the acquired data, each line representing a sample of multiple individual measurements at positions 1-23 along the x-axis. The y-axis represents the stress profile of the glass. All but one of the samples had comparable deviations and thus, comparable stress levels. The remaining sample exhibited a significant deviation and thus, a significant stress level.

[0048] FIG. 6 illustrates the acquired data for similar samples of a glass substrate when a conventional thermocouple system was used. As in FIG. 5, each line represents a sample of multiple individual measurements at positions 1-23 along the x-axis. No significant deviations were detected when using the conventional thermocouple system. [0049] The optical position sensor of the present invention, as used in FIG. 5 was readily able to detect a transient deviation occurring in the glass substrate. In contrast, the conventional thermocouple system was unable to detect such a deviation. Thus, the use of an optical position sensor to detect deviations in the position of a glass substrate, and thus, changes in shape, can provide improved detection of defects, facilitating improved quality control.

[0050] Various modifications and variations can be made to the compositions, articles, devices, and methods described herein. Other aspects of the compositions, articles, devices, and methods described herein will be apparent from consideration of the specification and practice of the compositions, articles, devices, and methods disclosed herein. It is intended that the specification and examples be considered as exemplary.

Claims

CLAIMSWhat is claimed is:

1. A method for detecting a change in shape of a continuous substrate, the method comprising:

(a) irradiating with laser radiation at least a portion of a continuous substrate within a measurement zone,

(b) detecting on an optical position sensor at least a portion of a reflection of the laser radiation, and then

(c) determining a distance between the irradiated portion of the continuous substrate and the optical position sensor, and then

(d) comparing the distance to a predetermined value, a difference in which indicates a change in shape of the continuous substrate.

2. The method of claim 1, wherein the optical position sensor is in a predetermined fixed position with respect to the measurement zone.

3. The method of claim 1, wherein the continuous substrate is continuously moving through the measurement zone.

4. The method of claim 1, wherein steps (c) and (d) are performed for a plurality of iterations.

5. The method of claim 4, wherein the distance between the irradiated portion of the continuous substrate and the optical position sensor for each of the plurality of iterations are compared.

6. The method of claim 5, further comprising a control system capable of producing an alarm if the distance between the irradiated portion of the continuous substrate and the optical position sensor for each of the plurality of iterations varies by a predetermined amount.

7. The method of claim 6, wherein the continuous substrate is cut into a plurality of pieces after passing through the measurement zone, and wherein the control system is capable of identifying any of the plurality of pieces that comprised a portion of the continuous substrate wherein the distance between the irradiated portion of the continuous substrate and the optical position sensor varied by a predetermined amount while passing through the measurement zone.

8. The method of claim 1, wherein steps (c) and (d) are performed in a continuous manner.

9. The method of claim 1, further comprising providing at least one additional optical position sensor in optical communication with at least a portion of the measurement zone, wherein each of the optical position sensor and the at least one additional optical position sensor irradiates a separate portion of the continuous substrate within at least a portion of the measurement zone with laser radiation and detects a reflection thereof, and wherein a distance between each of the irradiated portions of the continuous substrate and the respective optical position sensor is determined.

10. The method of claim 1, wherein the continuous substrate comprises a glass ribbon.

1 1. The method of claim 1, wherein the continuous substrate comprises a glass ribbon formed from an overflow downdraw fusion process.

12. The method of claim 1, wherein the irradiated portion of the continuous substrate is within a setting zone or downstream of a setting zone of a glass forming process.

13. The method of claim 1, wherein the difference between the distance and the predetermined value is from about 100 μm to about 50,000 μm.

14. The method of claim 1 , wherein the difference between the distance and the predetermined value is from about 1,000 μm to about 30,000 μm.

15. The method of claim 1, wherein the optical position sensor is capable of detecting a difference in distance of from about 100 μm to about 50,000 μm.

16. The method of claim 1, wherein the optical position sensor is capable of detecting a difference in distance of from about 1,000 μm to about 30,000 μm.

17. An apparatus for detecting a change in shape of a continuous substrate, the apparatus comprising:

(a) laser radiating at least a portion of a continuous substrate within a measurement zone,

(b) an optical position sensor detecting at least a portion of a reflection of the laser radiation, and

(c) a control system that determines a distance between the irradiated portion of the continuous substrate and the optical position sensor, compares the distance to a predetermined value, and indicates a change in shape of the continuous substrate.

18. The apparatus of claim 17, wherein:

(a) the continuous substrate continuously moves past the optical position sensor, and

(b) the control system continuously iteratively determines the distance between the irradiated portion of the continuous substrate and compares the determined distance from iteration to iteration and calculates a variation in the determined distance between iterations.

19. The apparatus of claim 18, wherein the control system produces an alarm if the variation in the determined distance between iterations varies by more than a predetermined amount.

20. The apparatus of claim 19, further comprising:

(a) a cutting mechanism for cutting the continuous substrate into a plurality of sheets after passing through the measurement zone, and

(b) wherein the control system identifies any of the plurality of sheets that comprised a portion of the continuous substrate for which variation in the determined distance between iterations varies by more than a predetermined amount while passing through the measurement zone.