Method and apparatus for finishing a glass sheet
An apparatus for finishing a glass sheet comprising a pair of fluid bearings having bearing surfaces in opposing relation, the bearing surfaces spaced apart to define a channel for receiving the glass sheet, each bearing surface having a plurality of pores through which jets are introduced into the channel, the pores positioned on the bearing surface such that the jets produce a uniform fluid pressure across the bearing surface.
The invention relates generally to apparatus and methods for finishing glass. More particularly, the invention relates to an apparatus and a method for finishing a glass sheet having one or more pristine surfaces.
Glass sheets having surfaces that are pristine and of fire-polished quality are usually made by fusion processes. Such glass sheets are useful in making devices such as flat panel displays. A typical fusion process is illustrated in
As the continuous glass sheet 114 emerges from the draw 112, a piece of glass sheet is cut therefrom. The piece of glass sheet is then subjected to a finishing process, which typically includes precision cutting of the glass sheet into a desired size using mechanical scoring, followed by edge grinding and/or polishing to remove any sharp corners and edges. Glass cutting by mechanical scoring and traditional edge finishing by grinding and polishing produce glass particles that can contaminate the quality surface of the glass sheet. Extensive washing and drying are needed to wash off the glass particles. This extensive washing and drying impact the finishing line and manufacturing costs. The glass particles can also damage the quality surface of the glass sheet.
From the foregoing, there continues to be a desire for improvements in finishing a glass sheet that would minimize the finishing line and manufacturing costs and maintain the quality surface of the glass sheet in a pristine condition.
SUMMARY OF THE INVENTIONIn one aspect, the invention relates to an apparatus for finishing a glass sheet which comprises a pair of fluid bearings having bearing surfaces in opposing relation. The bearing surfaces are spaced apart to define a channel for receiving the glass sheet. Each bearing surface has a plurality of pores through which jets are introduced into the channel. The pores are positioned on the bearing surface such that the jets produce a uniform fluid pressure across the bearing surface.
In another aspect, the invention relates to a method of finishing a glass sheet which comprises loading a glass sheet in a channel defined between a pair of fluid bearings having bearing surfaces, wherein each bearing surface has a plurality of pores through which jets are introduced into the channel and the pores are such that the jets produce a uniform fluid pressure across the bearing surface, and finishing edges of the glass sheet.
Other features and advantages of the invention will be apparent from the following description and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in detail with reference to a few preferred embodiments, as illustrated in accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to one skilled in the art that the invention may be practiced without some or all of these specific details. In other instances, well-known features and/or process steps have not been described in detail in order to not unnecessarily obscure the invention. The features and advantages of the invention may be better understood with reference to the drawings and discussions that follow.
Inlet devices 215 have inlets 214 through which fluid from a fluid source (not shown) may be communicated in between the flow plate 212 and support plate 216. The flow plate 212 has openings or pores (213 in
In general, plenum design to achieve uniform fluid pressure across a vertical bearing surface is much simpler when the flow plate 212 is made of a porous material. Porous materials create resistance to vertical flow due to gravity, thereby allowing uniform fluid spread across the plenum surface and thickness. A flow plate 212 made of a porous material exhibiting the properties described above is preferred, i.e., diameter of the pores on the bearing surface 211 is greater than ½ the distance between adjacent pores. The use of thick, e.g., greater than approximately ⅛ in. (3.175 mm), porous material simplifies plenum design because fluid can redistribute itself evenly across the bearing surface 211. Examples of porous materials include, but are not limited to, ultra-high molecular weight (UHMW) high density polyethylene (HDPE), available from, for example, GenPore, Reading, Pa. Porous materials having an average pore size in a range from 5 μm to 150 μm, preferably 10 μm to 100 μm, more preferably 50 μm to 80 μm has been found to be useful. The pores in the porous material may or may not be evenly distributed and may have a variable size. The porous material thickness typically ranges from 10 mm to 50 mm, preferably around 25 mm. The fluid pressure drop through the thickness of the flow plate is preferably no greater 50%.
The first and second alignment devices 408, 414 may be operated to adjust the position of the fluid bearing system 200, or components thereof, as necessary, for example, relative to the platform 404 or glass sheet 202 or processing devices 500. The first and second alignment devices 408, 414 may be translation stages capable of translating components of the fluid bearing system 200 in one or more dimensions. For example, the first and second alignment devices 408, 414 may be x-y stages, which may be driven manually or automatically, for example, using motors, such as DC or stepper motors or servomotors. The x-y stages may be compound stages or may be made of individual translation stages. A stage or actuator providing translation in fewer than two dimensions may also be used as the alignment devices 408, 414. For example, adjusting components of the fluid bearing system 200 along the y-axis only may suffice. The alignment devices 408, 414 may also incorporate tilt platforms to allow for angular adjustment of the fluid bearing system 200.
The support frame 410 supports third and fourth translation stages 418, 420. A processing device 500 for finishing an edge of the glass sheet 202 may be coupled to each of the third and fourth translation stages 418, 420. Only the processing device 500 coupled to the third translation stage 418 is visible in the drawing. The third and fourth translation stages 418, 420 may extend the processing devices 500 to the fluid bearing system 200 in order to finish the edges of the glass sheet 202 supported in the fluid bearing system 200. A retractable bottom conveyor 424 is mounted on the fixture 406. The bottom conveyor 424 may be used to transport the glass sheet 202 into the fluid bearing system 200. After the edge grippers (208 in
The processing device 500 could be any suitable device that can be used to finish an edge of the glass sheet 202, such as a grinding, scoring, or polishing device. Preferably, the processing device 500 prevents contaminants generated during processing of the edges of the glass sheet 202 from reaching the quality zone of the glass sheet. A suitable processing device is disclosed in U.S. Patent Application Publication No. US 2005/0090189 (Brown et al.), the content of which is incorporated herein.
When the edges of the glass sheet are cut using a processing device with a shroud, the quality zone of the glass sheet is protected from the contaminants produced during the finishing process. The edges of the glass sheet can be finished with tools such as grinding and scoring wheel. Other finishing devices, such as slurry jet or nitrogen jet, may also be used in place of the grinding wheel. A shroud may be used with the slurry or nitrogen jet devices to enclose the edges of the glass sheet. The shroud allows a chemical coolant or other lubricant to be used during the finishing process. The coolant is contained within the shroud, thereby avoiding staining of the quality zone of the glass. Use of a coolant, such as one that is silane-based, can increase the effectiveness of the finishing tool, e.g., the grinding wheel, and can help heal cracks in the edges of the glass, resulting in stronger edges. The edge debris after finishing can be cleaned by water jet contained within the shroud.
Various arrangements of the processing devices 500 relative to the fluid bearing system 200 are possible.
The various arrangements described above could also be configured in a horizontal orientation rather than the vertical orientation depicted in the figures. In a horizontal arrangement, the fluid bearing would be horizontal. Any auxiliary equipment for handling the glass sheet, such as bottom or overhead conveyor, edge grippers, robot suction cups, preferably touches the glass sheet in the non-quality area, typically 5-10 mm from the edges of the glass sheet. Using the arrangements above, if the fluid in the fluid bearing is liquid, the glass sheet is kept wet inside the fluid bearing during edge finishing, which prevents particle buildup on the glass sheet due to electrostatic charges. Keeping the glass sheet wet also prevents fluid stains on the glass sheet.
The following finishing process examples are presented for illustration purposes and are not to be construed as limiting the invention as otherwise described herein.
EXAMPLE 1A continuous glass sheet is formed by a fusion process. As the continuous glass sheet emerges from the draw, a glass sheet of desired size is cut from the continuous glass sheet using a traveling anvil method (TAM). TAM involves scoring the continuous glass sheet using a scoring assembly that travels alongside the continuous glass sheet at a speed that matches the speed of the continuous glass sheet. In a standard TAM cut, the scoring device is a mechanical scoring wheel. Just before scoring the continuous glass sheet, a robot hand applies suction cups to the continuous glass sheet. The robot end-effectors coupled to the suction cups travel with the moving sheet as well. Once the sheet is scored with TAM, the robot bends the sheet to separate it from the continuous glass sheet. The robot then hands the sheet over to an overhead conveyor, which moves the sheet to another station. In this example, a set of rollers (or edge guides) grip the edges of the continuous glass sheet as the continuous glass sheet passes through the draw, as is well-known in the art. In this case, the next station is a station where vertical bead removal (VBS) occurs, i.e., trimming of the vertical edges of the glass to remove beads. Typically, the beads are removed before the glass sheet is cold; otherwise, too much stress may set into the glass sheet. VBS is not needed if the edges of the continuous glass sheet do not pass through rollers (or edge guides) in the draw.
EXAMPLE 2A glass sheet as prepared in EXAMPLE 1 is processed on a finishing line including one or more of the fluid bearing system of the invention. The finishing process includes cutting the glass sheet to size using a thermal shock cutting process. Thermal shock cutting processes are described in, for example, U.S. Pat. Nos. 6713720, 6204472, 6327875, 6407360, 6420678, 6541730, and 6112967, the tutorial contents of which are incorporated herein by reference. In general, the thermal shock cutting process involves heating the glass sheet along a narrow line using a heat source such as a laser or plasma torch. Heating of the glass sheet along the narrow line is immediately followed by rapid cooling of the glass sheet along the narrow line. The heating and cooling cycle creates a thermal shock in the glass in the vicinity of the narrow line, which results in a crack that propagates along the narrow line. The glass sheet separates or can be easily separated from the glass sheet along the crack.
The glass sheet may be supported on an air bearing during the thermal shock cutting process. Air bearings can be simple, e.g., with holes blowing air to suspend the glass or air/vacuum combination such as NEW WAY® air bearings, available from New Way Air Bearings, Aston, Pa., or Core Flow air bearings. Alternatively, the fluid bearing system described above may be used with air as the fluid. After cutting the glass sheet to size, the edges of the glass sheet are finished while supporting the glass sheet in the fluid bearing system. A first set of opposite edges of the glass sheet may be finished (cut and ground/polished) simultaneously. Then, the remaining set of opposite edges of the glass sheet may also be finished simultaneously with or without rotating the glass sheet. The glass sheet is then washed because TAM and VBS in EXAMPLE 1 are not clean. After washing the glass sheet, the glass sheet is dried using an air knife. The glass sheet is then inspected. After inspection, the glass sheet may be coated with a protective coating. The glass sheet is then packed for shipping and/or storage.
EXAMPLE 3A glass sheet is finished as in EXAMPLE 2, except that the glass sheet is cut to size while supporting the glass sheet in a fluid bearing system and using processing devices with shroud.
EXAMPLE 4A glass sheet is prepared as in EXAMPLE 1, except that TAM cut and VBS is by thermal shock process. The thermal shock process is clean and does not produce glass chips that can contaminate the quality zone of the glass sheet. The glass sheet is then finished as in EXAMPLE 2 or EXAMPLE 3, except that final washing of glass sheet is not needed because TAM cut and VBS are clean.
The invention typically provides the following advantages. Extensive washing and drying of the glass sheet typically associated with prior art finishing processes can be avoided where TAM cut and VBS are clean as described in, for example, EXAMPLE 4 above. The finishing processes described above can be easily integrated with fusion processes. The fluid bearing system provides support to the glass sheet during the edge finishing process without contacting the quality zone of the glass sheet. The fluid bearing system adds stiffness to the glass, enabling more precise cut and preventing deformation during edge finishing of the glass sheet. The fluid bearing system can be used to control the temperature of the glass sheet to maximize edge processing efficiency. The footprint of the processing line in the vertical orientation is significantly reduced over a horizontal orientation. Contamination of the quality zone of the glass sheet while the glass sheet is in the fluid bearing system is avoided by shrouding the edges of the glass sheet during edge processing.
While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.
Claims
1. An apparatus for finishing a glass sheet, comprising:
- a pair of fluid bearings having bearing surfaces in opposing relation, the bearing surfaces spaced apart to define a channel for receiving the glass sheet, each bearing surface having a plurality of pores through which jets are introduced into the channel, the pores positioned on the bearing surface such that the jets produce a uniform fluid pressure across the bearing surface.
2. The apparatus of claim 1, wherein the pores are positioned such that the jets produced from the pores interact.
3. The apparatus of claim 1, wherein a diameter of the pores is greater than one-half the distance between adjacent pores.
4. The apparatus of claim 1, wherein each fluid bearing comprises a flow plate, and a surface of the flow plate provides the bearing surface.
5. The apparatus of claim 4, wherein the pores in the bearing surface are provided by perforations in the flow plate.
6. The apparatus of claim 4, wherein the flow plate is made of a porous material.
7. The apparatus of claim 6, wherein the porous material has an average pore size in a range from 5 μm to 150 μm.
8. The apparatus of claim 6, wherein the porous material has an average pore size in a range from 10 μm to 100 μm.
9. The apparatus of claim 6, wherein the porous material has an average pore size in a range from 50 μm to 80 μm.
10. The apparatus of claim 6, wherein a thickness of the flow plate is in a range from 10 mm to 50 mm.
11. The apparatus of claim 4, wherein each fluid bearing further comprises an inlet through which fluid can be communicated to the flow plate.
12. The apparatus of claim 1, further comprising a processing device adjacent the fluid bearings for processing an edge of the glass sheet.
13. The apparatus of claim 12, wherein the processing device includes a finishing device for processing the edge of the glass sheet and a shroud for containing contaminants generated during the processing.
14. The apparatus of claim 12, further comprising a mechanism coupled to the processing device for moving the processing device relative to the fluid bearings.
15. The apparatus of claim 12, further comprising a mechanism configured to engage the glass sheet and move the glass sheet relative to the fluid bearings.
16. The apparatus of claim 15, wherein the mechanism comprises a set of edge grippers and a linear slide coupled to the set of edge grippers.
17. The apparatus of claim 1, further comprising a conveyor for transporting the glass sheet into or out of the channel.
18. The apparatus of claim 17, wherein the conveyor is retractable to allow a processing device access to an edge of the glass sheet.
19. The apparatus of claim 1, further comprising edge grippers extending into the channel for gripping edges of the glass sheet.
20. The apparatus of claim 1, wherein each fluid bearing comprises a plurality of the bearing surfaces in a stack.
21. A method of finishing a glass sheet, comprising:
- loading a glass sheet in a channel defined between a pair of fluid bearings having bearing surfaces, wherein each bearing surface has a plurality of pores through which jets are introduced into the channel and the pores are such that the jets produce a uniform fluid pressure across the bearing surface; and
- finishing edges of the glass sheet.
22. The method of claim 21, wherein finishing edges of the glass sheet comprises grinding and/or polishing opposite edges of the glass sheet.
23. The method of claim 21, wherein finishing edges of the glass sheet comprises advancing a finishing device to the edges of the glass sheet and moving the finishing device relative to the edges of the glass sheet.
24. The method of claim 21, wherein finishing edges of the glass sheet comprises advancing a finishing device to the edges of the glass sheet and moving the edges of the glass sheet relative to the finishing device.
25. The method of claim 21, wherein finishing edges of the glass sheet comprises finishing opposite edges of the glass sheet simultaneously.
26. The method of claim 21, further comprising cutting the glass sheet from a continuous glass sheet prior to loading the glass sheet into the channel.
27. The method of claim 26, wherein the continuous glass sheet is produced by a fusion process and cutting the glass sheet is by a travel anvil method.
28. The method of claim 27, wherein cutting the glass sheet is by a thermal shock process.
29. The method of claim 26, further comprising removing beads from edges of the glass sheet prior to loading the glass sheet into the channel.
30. The method of claim 27, wherein removing beads is by a thermal shock process.
31. The method of claim 21, wherein finishing edges of the glass sheet comprises finishing a first set of edges of the glass sheet followed by finishing a second set of edges of the glass sheet.
32. The method of claim 31, further comprising rotating the glass sheet prior to finishing the second set of edges of the glass sheet.
33. The method of claim 32, wherein the glass sheet is removed from the channel prior to rotating the glass sheet and loaded into another channel defined by a pair of fluid bearings prior to finishing the second set of edges of the glass sheet.
34. The method of claim 21, further comprising washing the glass sheet.
35. The method of claim 21, further comprising drying the glass sheet.
36. The method of claim 21, further comprising coating the glass sheet with a protective coating.
Type: Application
Filed: Dec 16, 2005
Publication Date: Jun 21, 2007
Inventors: James Brown (Painted Post, NY), Charles Darcangelo (Corning, NY), Yawei Sun (Horseheads, NY), Ljerka Ukrainczyk (Painted Post, NY)
Application Number: 11/305,386
International Classification: B65H 20/00 (20060101);