CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of U.S. Provisional Application Serial No. 62/659,353 filed on April 18, 2018 the contents of which are relied upon and

incorporated herein by reference in their entirety as if fully set forth below.

BACKGROUND

FIELD

[0002] The present disclosure relates to an apparatus for dressing an abrasive wheel, and more specifically for in situ dressing of the abrasive wheel.

TECHNICAL BACKGROUND

[0003] Glass sheets are used to form display panels used in a variety of electronic devices, including televisions, computer monitors, cell phones, electronic tablets and so forth. The glass sheets as used in the manufacture of display panels are cut from larger glass sheets, leaving sharp, easily-damaged edges. The edges are routinely ground (e.g., chamfered) using a first abrasive wheel, then polished with a second abrasive wheel to smooth and clean the ground edge. Over time, the surface of the second abrasive wheel forms a groove that can become clogged with debris from the polishing operation and must be cleaned of this debris to regain polishing effectiveness in a process known as“dressing.”

SUMMARY

[0004] Abrasive wheel dressing can be performed off-line and off-site. That is, the abrasive wheel is removed from the finishing apparatus and sent to a separate facility, for example the abrasive wheel manufacturer, for dressing. However, such off-site dressing can result in an out-of-true wheel, wherein the renewed abrasive surface is not precisely concentric with the axis of rotation of the abrasive wheel. Moreover, the vendor responsible for dressing the wheel can remove more material than necessary, which can result in a shortened wheel life after multiple dressings.

[0005] In accordance with the present disclosure, a glass finishing apparatus is disclosed that can facilitate on-line and on-site dressing of an abrasive wheel, for example in a glass edge finishing process, the glass finishing apparatus comprising a spindle rotatable about an axis of rotation, and movable in a direction along a length of the axis of rotation, an abrasive wheel mounted to the spindle, a shroud extending around at least a portion of the abrasive wheel, and a cutting tool. By on-site and on-line what is meant is that the glass finishing apparatus can be installed in a working glass finishing operation wherein grinding and/or polishing of a glass sheet occurs. The finishing operation can be halted when the efficacy of an abrasive wheel is sufficiently reduced, and dressing of the abrasive can be performed without removing the abrasive wheel from the glass finishing apparatus. When the dressing operation is completed, the glass finishing apparatus can be placed back into operation by withdrawing the dressing (cutting) tool from the abrasive wheel and engaging a new glass sheet against the newly dressed abrasive surface of the abrasive wheel.

[0006] The finishing apparatus may further include a coolant nozzle arranged to direct a coolant at the abrasive wheel, and an exhaust duct configured to exhaust particles and coolant from within the shroud. For example, the nozzle can be arranged to direct coolant at a point of contact between the cutting tool and the abrasive wheel.

[0007] The cutting tool is movable between a disengaged and an engaged position relative to the abrasive wheel. That is, the cutting tool is moveable between a disengaged position wherein the cutting tool does not contact the contact surface of the abrasive wheel, and an engaged position wherein the cutting tool contacts the contact surface of the abrasive wheel.

[0008] The shroud can comprise a slot sized to receive an edge portion of a glass sheet, wherein an edge surface of the glass sheet can engage with the abrasive wheel.

[0009] In other embodiments, a method of in-line dressing of an abrasive wheel is disclosed comprising rotating the abrasive wheel and a spindle mounted thereto about an axis of rotation of the spindle, forming a plurality of grooves across a contact surface of the abrasive wheel by engaging the contact surface with edges of a first plurality of glass sheets. The method may further comprise engaging the contact surface of the abrasive wheel with a cutting tool without removing the abrasive wheel from the spindle while traversing the abrasive wheel in a direction along the axis of rotation, the cutting tool removing a layer of abrasive material from the contact surface and forming a new contact surface, and engaging the new contact surface with a subsequent glass sheet. The abrasive wheel is rotating during the removing, for example at a rate in a range from about 500 RPM to about 700 RPM.

[0010] In some embodiment, the cutting tool can comprise diamond.

[0011] In some embodiments, a thickness of the layer of abrasive material can be equal to or less than about 1.5 mm, for example equal to or less than about 1.0 mm. [0012] In some embodiments, a speed of the traversing can be in a range from about 40 millimeters/sec to about 80 millimeters/second.

[0013] Additional features and advantages of the embodiments disclosed herein will be set forth in the detailed description that follows, and in part will be apparent to those skilled in the art from that description or recognized by practicing the embodiments described herein, including the detailed description which follows, the claims, as well as the appended drawings.

[0014] It is to be understood that both the foregoing general description and the following detailed description present embodiments intended to provide an overview or framework for understanding the nature and character of the embodiments disclosed herein. The

accompanying drawings are included to provide further understanding, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the disclosure, and together with the description serve to explain the principles and operations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG. l is a side view of an exemplary abrasive wheel engaged with a glass sheet;

[0016] FIG. 2 is a cross-sectional view of a groove formed in an edge surface of an abrasive wheel and illustrating partial clogging of the groove;

[0017] FIG. 3 is a top view of an exemplary finishing apparatus illustrating a cutting tool for reworking a contact surface of the abrasive wheel;

[0018] FIG. 4 is a side view of the finishing apparatus of FIG. 3;

[0019] FIG. 5 is a side cross-sectional view of a portion of an abrasive wheel comprising a series of grooves in a contact surface thereof formed by contact with the edge surface of a glass sheet; and

[0020] FIG. 6 is a cross-sectional side view of the abrasive wheel of FIG. 5, showing surface layer removal by a cutting tool.

DETAILED DESCRIPTION

[0021] Reference will now be made in detail to embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. However, this disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. [0022] 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 embodiment includes from the one particular value 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 embodiment. 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.

[0023] Directional terms as used herein - for example up, down, right, left, front, back, top, bottom - are made only with reference to the figures as drawn and are not intended to imply absolute orientation.

[0024] Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order, nor that with any apparatus, specific orientations be required. Accordingly, where a method claim does not actually recite an order to be followed by its steps, or that any apparatus claim does not actually recite an order or orientation to individual components, or it is not otherwise specifically stated in the claims or description that the steps are to be limited to a specific order, or that a specific order or orientation to components of an apparatus is not recited, it is in no way intended that an order or orientation be inferred in any respect. This holds for any possible non-express basis for interpretation, including: matters of logic with respect to arrangement of steps, operational flow, order of components, or orientation of components; plain meaning derived from grammatical organization or punctuation, and; the number or type of embodiments described in the specification.

[0025] As used herein, the singular forms "a," "an" and "the" include plural references unless the context clearly dictates otherwise. Thus, for example, reference to“a” component includes aspects having two or more such components, unless the context clearly indicates otherwise.

[0026] The word“exemplary,”“example,” or various forms thereof are used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as “exemplary” or as an “example” is not necessarily to be construed as preferred or advantageous over other aspects or designs. Furthermore, examples are provided solely for purposes of clarity and understanding and are not meant to limit or restrict the disclosed subject matter or relevant portions of this disclosure in any manner. It is to be appreciated that a myriad of additional or alternate examples of varying scope could have been presented, but have been omitted for purposes of brevity. [0027] Glass sheets as commercially utilized typically begin as large“mother” sheets, wherein smaller glass sheets are obtained by cutting the mother glass sheets into smaller “daughters”. The cutting process can be performed by a score and break process, wherein a score line is produced in a score direction across one surface of the mother sheet, followed by imparting a bending moment on the mother sheet that places a tension stress across the score line. The tension stress causes a crack along the score line to extend through the thickness of the glass sheet that separates the glass sheet into daughters. The score line can be formed by mechanical means, for example via a score wheel, a scribe (e.g., diamond or carbide-tipped scribe tool), or using a laser, such as a C0 ₂ laser. In some embodiments, a small flaw (e.g., a scratch or chip) can be formed along an edge of the mother sheet. A laser beam, for example a C0 ₂ laser beam, can be used to heat the glass sheet along a cutting path, followed by rapid cooling of the cutting path, such as with a cooling fluid delivered by a nozzle assembly. The rapid change in temperature created by the cooling causes a thermal stress along the cutting path that drives a crack through the thickness of the glass sheet and along the cutting path, thereby separating the mother sheet into daughters. In still other embodiments, laser cutting of the mother sheet can be accomplished without the need for fluid cutting. In short, there are a variety of ways in which a large glass sheet can be separated into smaller glass sheets. However, it is desirable that the selected cutting process produce an initially mirror-like surface free from cracks, chips, shards and other defects.

[0028] It is well known that breakage of glass sheets typically originates from a defect at an edge of the glass sheet, since the edges are most prone to physical contact. Moreover, the edges where the cut edge surface intersects the major surfaces of the glass sheet (intersection edges) are extremely sharp and can pose a safety hazard to personnel that may handle the glass sheet. Accordingly, the edges of a glass sheet after cutting are typically ground and polished, for example to form a chamfer, thereby removing the sharp intersection edges and small defects on the edge surface.

[0029] One method of removing the intersection edges is by grinding and/or polishing with an abrasive wheel, wherein the edge forms a non-planar edge surface and a complementary groove in the abrasive wheel. As used herein, the term complementary refers to shapes that are opposite and fit together, for example like jigsaw puzzle pieces. In some embodiments, the grinding forms a chamfered edge surface comprising adjacent flat edge surfaces, while in other embodiments, the edge surface can be formed to an arcuate edge surface, for example a semicircular edge surface. It should be apparent that after grinding, the ground edge surface of the glass sheet is rough and includes debris from the grinding process, for example particles of glass and abrasive. Accordingly, once the edge has been shaped with a first abrasive wheel, the edge can be polished with a second abrasive wheel to remove the roughness and clean the edge of the glass sheet.

[0030] Referring to FIG. 1, an exemplary abrasive wheel 10 is illustrated as a generally cylindrical disc including a contact surface 12 for contacting an edge of a glass sheet, the abrasive wheel comprising an abrasive material, e.g., aluminum oxide (e.g., alpha alumina), titanium diboride, titanium nitride, cubic boron nitride, silicon carbide, boron carbide, tungsten carbide, titanium carbide, garnet, alumina-zirconia, cerium oxide, zirconium oxide, titanium oxide, sol-gel derived abrasive particles, diamond, and combinations thereof. While in some embodiments the abrasive particles can be bonded together in a cementing matrix, in other embodiments, the abrasive material can be dispersed and bonded together in a compliant material, such as a rubber or rubber-like material. Abrasive wheel 10 can have a generally flat circumferential contact surface 12 parallel with the axis of rotation 14. For example, contact surface 12 can be concentric with axis of rotation 14. As abrasive wheel 10 is rotated about axis of rotation 14, a peripheral edge surface 16 of a glass sheet 18 (e.g., mother or daughter) is frictionally contacted against contact surface 12 and relative motion between the abrasive wheel and the glass sheet abrades the glass sheet and removes glass material from the glass sheet along a length of the peripheral edge portion. In addition to peripheral edge surface 16, glass sheet 18 comprises a first major surface 20, a second major surface 22 generally parallel with first major surface 20, and a thickness Tg defined therebetween. Peripheral edge surface 16 connects first major surface 20 with second major surface 22. In some cases, glass sheet 18 can be moved relative to a stationary abrasive wheel 10 during the contacting, while in other cases, glass sheet 18 can be stationary and abrasive wheel 10 is moved relative to the glass sheet during the contacting. In still other instances both abrasive wheel 10 and glass sheet 18 can be moved during the contacting.

[0031] As the peripheral edge surface 16 of glass sheet 18 is pressed into contact surface 12 of abrasive wheel 10 with a predetermined force, abrasive particles are dulled (e.g., smoothed), and the resultant increased friction with the glass edge can loosen and remove abrasive particles from the contact surface. After a time, a groove 24 forms in the contact surface. As the groove deepens, debris can fill the groove and prevent full contact between the abrasive wheel and edge surface 16, thereby reducing the efficacy of abrasive wheel 10.

[0032] Accordingly, to ensure full contact between the glass sheet edge surface 16 and abrasive wheel 10, abrasive wheel 10 can be shifted in a direction along the rotational axis of the abrasive wheel such that subsequent glass sheet edges brought into contact with the abrasive wheel bear against a previously unused surface portion of the abrasive wheel. This process is repeated each time the efficacy of the abrasive wheel is sufficiently reduced. It should be apparent that in further embodiments, subsequent glass sheets 18 can be shifted in a direction parallel to the axis of rotation of abrasive wheel 10 to an unused portion of the contact surface rather than changing a position of the abrasive wheel. However, abrasive wheel 10 may be contained within a shroud or other protective enclosure to prevent escape of particles, and this enclosure can prevent displacement of the glass sheet parallel to the axis of rotation.

[0033] Each time a groove 24 deepens to the point where the abrasive effect of the abrasive wheel is diminished, the abrasive wheel can be shifted in a direction along the axis of rotation to expose an unused portion of contact surface 12 to an edge surface of a glass sheet. Eventually, contact surface 12 is filled with grooves, for example 10 to 12 grooves, at which point the abrasive wheel can be discarded, or, more cost effectively, contact surface 12 can be reworked (dressed) to expose a new, unused abrasive contact surface.

[0034] In some instances, abrasive wheel 10 can be removed from the finishing apparatus and mounted to a separate abrasive wheel dressing apparatus. The separate abrasive wheel dressing apparatus can be used to remove a layer from the grooved surface of the abrasive wheel to a depth greater than a depth of the deepest groove, after which the abrasive wheel is removed from the separate abrasive wheel dressing apparatus and re-mounted to the finishing apparatus. However, dismounting the abrasive wheel to perform off-line dressing of the abrasive wheel can result in unacceptable run-out of the abrasive wheel when the abrasive wheel is remounted to the finishing apparatus (wherein the axis of rotation of the spindle on which the abrasive wheel is mounted is non-concentric with the contact surface).

[0035] FIGS. 3 and 4 show, respectively, a top view and a side view of an exemplary glass finishing apparatus 100 that can be used both to grind and/or polish the edge surface of a glass sheet and to dress the abrasive surface of an abrasive wheel mounted to the glass finishing apparatus without removing the abrasive wheel from the glass finishing apparatus. Exemplary glass finishing apparatus 100 can comprise an abrasive wheel 102 mounted to a spindle 112 via a bore through the abrasive wheel sized to receive spindle 112, abrasive wheel 102 rotatable via spindle 112 about an axis of rotation 114. Abrasive wheel 102 comprises a first major surface 104 and a second major surface 106 defining a thickness Tw therebetween, and an abrasive contact surface 116 that connects first major surface 104 with second major surface 106. In some embodiments, contact surface 116 can be orthogonal to first and second major surfaces 104 and 106, and parallel to and concentric with axis of rotation 114. In embodiments, abrasive wheel 102 can be a polishing wheel comprising a fine grit size (e.g., in a range from about 180 grit to about 400 grit) dispersed in a compliant matrix material.

[0036] Glass finishing apparatus 100 can further include an enclosure 118 (e.g., shroud) extending at least partially around abrasive wheel 102, a cutting tool 120 configured to engage abrasive wheel 102, a coolant nozzle 122 arranged to direct a stream 124 of coolant 126 (e.g., water) at abrasive wheel 102, and an exhaust duct 128 in fluid communication with air handler 108 (e.g., blower) and configured to exhaust particles and coolant from within the region circumscribed by shroud 118.

[0037] Spindle 112 can be configured to vary in position along axis of rotation 114. That is, spindle 112, and therefore abrasive wheel 102, can move along axis of rotation 114 (i.e., in the ± Z direction) via drive apparatus 130 to which spindle 112 is coupled. Drive apparatus 130 includes a drive motor (not shown) for rotating abrasive wheel 102, and may further include a mechanism for moving spindle 112 in the Z, -Z directions along axis of rotation 114.

[0038] Cutting tool 120 can be any suitable cutting tool configured to remove a layer of material from a surface of abrasive wheel 102. For example, cutting tool 120 can be formed of tool steel (e.g., steel with a carbon content in a range from about 0.5% to about 1.5% by weight), and may be further alloyed or coated with tungsten, chromium, vanadium, molybdenum, cobalt, or combinations thereof, or cutting tool 120 can be a cemented carbide, including tungsten carbide, titanium carbide, or tantalum carbide. In further embodiments, cutting tool 120 may be a diamond cutting tool.

[0039] Cutting tool 120 can be mounted in a holder 132, for example a moveable stage, providing movement in at least the X, -X directions (toward or away from abrasive wheel 102, e.g., contact surface 116) perpendicular to axis of rotation 114. For example, in some embodiments, cutting tool 120 may be coupled to a micrometer adjusting device 134 mounted in holder 132 that provides for fine movement of cutting tool 120 in the X, -X directions, thereby allowing accurate and precise removal of a layer of predetermined thickness from abrasive wheel 102 (e.g., from contact surface 116). Holder 132 may be further movable in the Z, -Z directions (parallel with axis of rotation 116), and in some embodiments, also the Y, -Y directions.

[0040] FIGS. 5 and 6 show cross-sectional views of a portion of abrasive wheel 102 depicting contact surface 116 with a plurality of grooves 136 resulting from contacting glass sheets. FIG. 5 illustrates abrasive wheel 102 with cutting tool 120 in an initial disengaged position not in contact with abrasive wheel 102 (e.g., contact surface 116). FIG. 6 depicts cutting tool 120 having moved toward and engaged with contact surface 116 as abrasive wheel 102 is both rotated and moved in the -Z direction such that cutting tool 120 moves across contact surface 116 of abrasive wheel 102 and removes surface layer 138 with a predetermined thickness“t” in a radial direction orthogonal to axis of rotation 114. In some embodiments, cutting tool 120 can be arranged to engage contact surface 116 at a position spaced apart from the adjacent major surface (e.g., second major surface 106) of abrasive wheel 102 by a spacing distance R in a range from about 0.2 mm to about 0.3 mm. In embodiments, thickness t of surface layer 138 can be equal to or less than 1.5 mm, for example equal to or less than about 1.2 mm, equal to or less than about 1.0 mm, equal to or less than about 0.8 mm, or equal to or less than about 0.6 mm. Abrasive wheel 102 can be rotated about axis of rotation 114 at a rotation speed in a range from about 500 revolutions per minute (RPM) to about 700 RPM, for example in a range from about 550 RPM to about 650 RPM, such as about 600 RPM.

[0041] During the period in which cutting tool 120 is engaged with abrasive wheel 102 and removing surface layer 138 therefrom, abrasive wheel 102 may be traversed in either one of the Z or -Z directions with a traverse speed in a range from about 40 millimeters/second (mm/s) to about 80 mm/s, for example in a range from about 50 mm/s to about 70 mm/s. For example, in some embodiments, abrasive wheel 102 can be moved in the Z or -Z direction at a transverse speed of about 60 mm/second. In the embodiment of FIG. 6, abrasive wheel 102 is shown being moved in a -Z direction, as indicated by arrow 144.

[0042] Once abrasive wheel 102 has been dressed and contact surface 116 has been renewed (surface layer 138 removed), the renewed contact surface 116 can then be contacted by a subsequent glass sheet 18 to perform a finishing operation on the subsequent glass sheet. For example, glass sheet 18 can oriented such that a plane of glass sheet 18 (e.g., a plane of first or second major surface 20, 22) is orthogonal to axis of rotation 114 and glass sheet 18 inserted into slot 142 in shroud 118 and into contact with abrasive wheel 102. Glass sheet 18 can then be traversed, for example in a direction 146, such as opposite the direction of rotation of abrasive wheel 102 at the point of contact between the abrasive wheel and the glass sheet (see FIG. 3).

[0043] It will be apparent to those skilled in the art that various modifications and variations can be made to embodiments of the present disclosure without departing from the spirit and scope of the disclosure. Thus it is intended that the present disclosure cover such modifications and variations provided they come within the scope of the appended claims and their equivalents.