Patent Application
20150299020
The present disclosure relates to apparatus and methods of forming a scribing mark, and methods of cutting a sheet of glass and, more particularly, to apparatus and methods of cutting a thin glass sheet, and methods of forming a scribing mark on a sheet of thin glass.
One conventional way to cut a portion out of a sheet of glass involves forming a scribing mark on the sheet of glass and bending the sheet of glass around the scribing mark so as to detach or separate the portion from the rest of the sheet. In such a process, the quality of the scribing mark can affect the overall edge quality of the sheet of glass which, in turn, affects the glass strength. There is a need to repeatedly form scribing marks of satisfactory quality. However, it is difficult to form scribe marks on thin sheets of glass, for example, those with thickness of 0.2 mm or less, because typical glass cutters are designed for sheets of glass of higher thickness and cannot form scribe marks of acceptable quality on the thinner sheets of glass.
Therefore, there is a need for apparatus and methods of forming scribing marks on thin sheets of glass.
In a first aspect, a pad is configured to be subjected to a compressive force applied substantially along a thickness direction. The pad has variable viscoelasticity such that, as an applied compressive stress is continuously increased in an order of a first range and a second range, the viscoelasticity is lower when there is applied a compressive stress in the second range than when there is applied a compressive stress in the first range.
In one example of the first aspect, the pad includes a top layer and an intermediate layer. In one example, when there is applied a compressive stress in the first range, the viscoelasticity of the pad is exhibited by the top layer, and when there is applied a compressive stress in the second range, the viscoelasticity of the pad is exhibited by the intermediate layer. In another example, the intermediate layer having a porous configuration. In still another example, the pad further including a bottom layer and having variable viscoelasticity such that, as a compressive stress is applied in a third range, the compressive stress in the third range being greater than that applied in the second range, the viscoelasticity exhibited by the pad is lower when there is applied a compressive stress in the second range than when there is applied a compressive stress in the third range. For example, the pad can have variable viscoelasticity such that, when there is applied a compressive stress in the third range, the viscoelasticity of the pad is exhibited primarily by the top and bottom layers. In another example, the pad includes a plurality of passages extending in the thickness directions, the top layer, the intermediate layer and the bottom layer including a first set of holes, a second set of holes and a third set of holes respectively, the plurality of passages defined by alignment of the first set of holes, the second set of holes and the third set of holes.
In another example of the first aspect, the pad is made of polyvinyl chloride and polyester material.
In still another example of the first aspect, the pad has a thickness of about 1.5-2.2 mm.
In yet another example of the first aspect, the Shore A hardness is of 5-35 for the pad.
In still another example of the first aspect, the pad is configured to undergo greater deformation when there is applied a compressive stress in the second range than when there is applied a compressive stress in the first range such that a first range of reactive force exerted by the pad when there is applied a compressive stress in the first range is greater than a second range of reactive force exerted by the pad when there is applied a compressive stress in the second range.
The first aspect can be provided alone or in combination with any one or more examples of the first aspect discussed above.
In a second aspect, a method of cutting a sheet of glass includes the steps of placing a pad between a working surface and the sheet of glass and securing the sheet of glass relative to the working surface. The method further includes the steps of scribing the sheet of glass secured relative to the working surface and separating a portion of the sheet of glass from the sheet of glass.
In one example of the second aspect, the step of scribing includes applying an operating pressure on a scribing tool. The pad is configured to deform and absorb pressure applied to the glass sheet during the step of scribing such that an operating pressure applied on the scribing tool is greater by at least a predetermined amount when the sheet of glass is supported with the pad than an operating pressure applied on the scribing tool when the sheet of glass is not supported with the pad. In one example, the pressure applied on the sheet of glass with the pad is in a range of 29 to 43 kPa. In another example, the step of scribing the sheet of glass is conducted with a cutting wheel. For example, the cutting wheel may be configured so that at its closest possible position relative to the working surface, the cutting wheel is located at a given distance from the working surface, wherein the sheet of glass has a thickness less than the amount of the given distance, and wherein the thickness of the pad together with the thickness of the sheet of glass is an amount greater than the given distance.
In another example of the second aspect, the step of securing the sheet of glass involves applying suction force on the sheet of glass, the suction force extending through the pad. In one example, the suction force is applied from the working surface.
The second aspect can be provided alone or in combination with any one or more examples of the second aspect discussed above.
In a third aspect, a method of forming a scribing mark on a sheet of glass includes the step of placing a compressible pad between a sheet of glass and a working surface. The method further includes the step of moving a scribing tool from a starting position toward the working surface so as to contact the sheet of glass. The method further includes the step of applying a scribing force of a predetermined value on the sheet of glass using the scribing tool. The method also includes the step of moving the scribing tool further toward the working surface and into a scribing position so as to deform the compressible pad and move the sheet of glass toward the working surface without increasing the scribing force, applied on the sheet of glass by the scribing tool, significantly beyond the predetermined value. The scribing position reached by the scribing tool is at least a predetermined distance offset from the starting position, the predetermined distance measured in a direction substantially perpendicular to the working surface.
In a fourth aspect, a method of forming a scribing mark on a sheet of glass includes the step of placing a compressible pad between a sheet of glass and a working surface. The method further includes the step of moving a scribing tool toward the working surface so as to contact an elevation at which a top surface the sheet of glass is located. The method further includes the steps of applying an operating pressure on the scribing tool and maintaining the operating pressure within a predetermined range at which a viscoelasticity of the compressible pad is substantially different compared to operating pressures outside the predetermined range. The method further includes the step of moving the scribing tool further toward the working surface and into a scribing position so as to deform the compressible pad and move the sheet of glass toward the working surface, the scribing position reached by the scribing tool is at least a predetermined distance offset from the elevation, the predetermined distance measured in a direction substantially perpendicular to the working surface.
In one example, the thickness of the sheet of glass is about 0.1 mm or less in any of the second aspect, one or any number of examples of the second aspect, the third aspect and/or the fourth aspect discussed above.
These and other aspects are better understood when the following detailed description is read with reference to the accompanying drawings, in which:
Examples will now be described more fully hereinafter with reference to the accompanying drawings in which example embodiments are shown. Whenever possible, the same reference numerals are used throughout the drawings to refer to the same or like parts. However, aspects may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.
In an example scribing process, as shown in
The scribing tool 6 is part of a cutting apparatus and may be lowered or set to a range of scribing positions, a given distance above the working surface 4. The inventors have found that for cutting apparatuses designed to cut thicker glasses, there is a lowest point at which the scribing tool can be set. At its lowest point, for some machines, the inventors have found that the distance from the scribing tool to the work surface is greater than the thickness of thin glass. Accordingly, such machines cannot adequately form a scribe line in thin glass. Additionally, for such machines designed to cut thicker glasses, the scribing tool can be set to various positions above the working surface 4 to form scribing marks with a range of depth values on the sheet of glass. The depth of the scribing mark is controlled by setting the scribing tool to a distance above the work surface, load force, scribing tool and glass conditions. In one example, the distance is half to two-thirds of the thickness of the sheet of glass. The depth of the scribing mark is measured from the top of the surface 3 to the bottom of the scribing mark within the body of the glass sheet. In another example manner of forming a scribe mark on a sheet of glass, the scribing tool 6 may be moved to an initial position at a distance from the working surface that is greater than the thickness of the sheet of glass to allow the sheet of glass to be put into position and held for scribing. Then, the cutting apparatus applies an operating pressure to the scribing tool 6 to lower it to the scribing position to form the scribe mark of a desired scribing depth. The scribing depth of the scribing tool 6 may be controlled on the cutting apparatus by the operator. In any event, the inventors have found that with thin glass sheets 2, because the scribing depth is very small the existing cutting apparatus (designed for thicker glass sheets) cannot always accurately adjust the position of the scribing tool 6 from its initial position to the lowest possible scribing position.
The graph of
Many cutting apparatus known in the art are designed for forming a scribing mark on sheets of glass with thicknesses ranging from 0.4 mm to 4 mm (thicker glasses). However, thin sheets of glass 2, for example with thickness of 0.2 mm or less (for example, 0.2, 0.19, 0.18, 0.17, 0.16, 0.15, 0.14, 0.13, 0.12, 0.11, 0.1, 0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, 0.02, 0.01 mm), also need to be cut into smaller portions after forming scribing marks thereon. In the case of thin glass sheets 2, the scribe depth is much smaller than 0.2 mm. In order to prevent the scribing tool 6 from cutting completely through the thickness of these thin sheets of glass 2, the operating pressure applied by the cutting apparatus on the scribing tool 6 should be maintained at a lower range compared to the thicker sheets of glass. However, at the same time, the operating pressure cannot be so low (as when a scribe depth of 0.2 mm or less is used) as to fall within the dead zone of operating pressures. Moreover, it is also necessary for the scribing depth of the scribing tool 6 to be sufficiently large such that proportionality between the loading force and the operating pressure occurs, and so that an adequate scribe line is formed in the surface of the thin glass sheet 2.
In order to allow cutting apparatuses (designed for thicker glass sheets) economically and simply to be retro-fit to adequately cut thin glass sheets, the inventors have found that a pad 10 may be used to support the thin glass sheet 2 on the working surface 4 of a cutting apparatus having a scribing tool 6.
When scribing thin sheets of glass 2 with a given thickness using the pad 10 with a given pad thickness and the scribing position (of the scribing tool) is at a given distance from the working surface 4, the sum of the given pad thickness and the given thickness of the sheet of glass 2 should be more than the given distance so that scribing will occur. As with scribing without the pad, the scribing depth would still be measured from the top surface of the sheet of glass 2.
The pad 10 may include two or more layers 12, 14, 16 each of which may have different properties and functions.
The top-most, or upper surface, layer 12 should be one that is sufficiently stiff so that the pad 10 provides initial support to the glass whereby as stress is applied the pad provides sufficient reaction force to allow the cutting wheel to apply a scribe force on the glass. The top-most layer 12 provides support to the thin glass 2 to prevent localized bending that would cause uncontrolled glass fracturing. The Shore A hardness of the top layer 12 of the pad 10 may be in the range of 5-35. This material should be one that does not contaminate the glass, allow a good vacuum to be applied between the glass and the material, and be non-abrasive with the glass.
Inner layer 14 should be very compressible, and provides the “fail safe” against over pressure being applied by the scribing tool (which over pressure would break the thin glass), i.e., the inner layer should deform with increased scribing-tool-movement distance in the z-direction (up and down direction as directions are shown in
The lower-most, or bottom, layer 16 is one that acts as a protective skin. This material should be stiff enough to prevent damage to the inner layer 14 by forces acting through the bottom of the pad, as well as during shipping/handling, installation, adjustment, etc. This material should be one that can hold the shape of a hole so that the pad can be aligned with the holes in the working surface of the cutting apparatus of which scribing tool 6 is a part. This material should also promote a good vacuum seal between the working surface 4 and the pad 10, thereby allowing the vacuum to extend through the pad and ultimately to the glass so as to hold the glass to the working surface. The material in this layer can be the same as, or different from, the material in the top layer. Additionally, this lower-most layer 16 may be present initially but then removed if the pad 10 is permanently attached to the working surface 4. This material should prevent loose particles from the inner layer contaminating the working surface 4 which may in turn contaminate the sheets of glass 2.
The pad 10 may further include a plurality of passages 18 that extend in thickness directions and are configured to be aligned with the vacuum holes 8 provided on the working surface 4, of the cutting apparatus, so that the suction force generated through the vacuum holes 8 may extend through the pad 10 and the suction force may be applied on the sheet of glass 2 to secure the sheet of glass 2 relative to the working surface 4. Thus, all of the layers 12, 14, 16 of the pad will have holes 20 that are configured to be aligned with the vacuum holes 8 and define the passages 18. Alternatively to having discrete holes, the material (or at least a portion thereof) of any particular layer may be of a porous nature (i.e., one having tortuous paths therethrough) so as to allow the vacuum developed at the working surface 4 to act on the thin glass sheets 2. In one example embodiment, the pad includes a top layer 12, an intermediate layer 14 and a bottom layer 16 which may include a first set of holes 20a, a second set of holes 20b and a third set of holes 20c respectively.
The material of which the pad 10 is made may provide properties, for example, compressibility or pliability and may include polyvinyl chloride and polyester materials, for example.
While all of the layers 12, 14, 16 may be made of the same material, each layer 12, 14, 16 may be structurally distinct in order to perform their respective functions. In one example, the intermediate layer 14 may have a porous configuration so as to be more compressible than the top layer 12 and the bottom layer 16, whereas the top layer 12 and the bottom layer 16 may be relatively thinner but denser and stiffer than the intermediate layer 14. The top layer 12 may be configured to provide the majority of reaction force in response to the force applied by the scribing tool 6. The intermediate layer 14 may be configured to undergo compressive deformation thereby: i) allowing the scribing tool 6 to reach a scribing position, or travel distance, that is sufficiently great enough, while maintaining the small scribe depth associated with thin glass sheets; ii) raising the operating pressure applied by the cutting apparatus on the scribing tool 6 to be sufficiently great enough so as to avoid the “dead zone” of operating pressures; and iii) limiting, by absorbing some of, the pressure/load force acting on the sheet of glass 2 to a range of values sufficient to form a consistent scribe line yet not so high as to cause the scribing tool 6 to cut through, or otherwise damage, the sheet of thin glass 2. The top layer 12 and intermediate layer 14 of pad 10 can be configured such that the majority of the deformation is from the intermediate layer 14 and wherein the top layer 12 will not undergo much local deformation relative to its immediate neighboring area. Acting together, the top layer 12 and the intermediate layer 14 will resist a force up to 4-5 N, and then the intermediate layer 14 will further deform to absorb additional furces, thereby limiting the force applied to the thin glass sheets 2.
The bottom layer 16 may be configured to reduce leakage around the vacuum holes 8. In one example, the pressure applied on the thin sheets of glass 2 for scribing, as opposed to an operating pressure applied on the scribing tool 6, may be in the range of 29 to 43 kPa. Such a pressure is equivalent to a force of 4-5 N and may be applied using a cylinder.
The combination of the layers 12, 14, 16 may cause the pad 10 to exhibit variable viscoelasticity as illustrated by the slope of the graph of compressive stress on the pad 10 versus the compressive strain of the pad 10, as shown in
The compressibility of the pad 10 allows for a more even surface on which to place a sheet of glass 2. When pressure is applied to the pad, the irregularities of the working surface 4 may be counterbalanced by the compressibility of the pad 10 such that a top surface of the pad 10 on which the sheet of glass 2 is placed has fewer irregularities. These irregularities of the working surface 4 may include surface variations, non-planarity, and non-parallelism with the motion of the scribing tool 6.
Cutting thin sheets of glass 2 is facilitated by the pad 10 and by maintaining the operating pressures applied on the scribing tool 6 within the process window 30. Specifically, in the process window 30 of operating pressures, the deformation of the pad 10 allows the scribing tool 6 to be lowered so as to reach a value of the preset depth that is sufficient for roughly linear proportionality between the operating pressure applied by the cutting apparatus on the scribing tool 6 and the load force as seen by the sheet of glass 2 to exist as shown in
For a given scribing pressure, consistent corresponding force is important for quality of scribing and separation in operation. This was exhibited in the low coefficient of variation of the scribe force corresponding to the window of operating pressures (in an example of 0.31-0.35 kgf/cm2 cutting pressure as applied by the cutting apparatus on the scribing tool, which corresponds to a net scribing force of 3-4 N as seen by the glass). Higher coefficient of variation of the scribing force in the pre-scribe region 22 was confirmed in an example
One example of the pad that was tested and found to work according to the principles described above was a pad having a total thickness of 1.8 mm. The pad included three layers, wherein: (i) an upper-most layer was made of a polyester material and had a thickness of 0.25 mm; (ii) an intermediate layer was made of porous polyvinyl chloride (PVC) and had a thickness of 1.4 mm; and (iii) a lower-most layer was made of a polyester material and had a thickness of 0.15 mm.
It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit and scope of the claimed invention.
For example, throughout the specification, the terms “scribe mark” and “scribe line” have been used interchangeably.
Further, although the pad is shown as including three layers, any desired number of layers may be used. For example, the inner layer 14 may include one or more different materials disposed in one or more sub-layers within the inner layer. Similarly, the upper-most 12 and lower-most layers 16 (shown) may include any number of sub-layers therein. In still other embodiments, the layer 16 may not be necessary, as when the layer 14 includes material that can form a sufficient vacuum seal with the working surface 4, or as when it is expected that the pad will be installed on the working surface 4 and not often moved.
This application claims the benefit of priority under 35 U.S.C. §119 of U.S. Provisional Application Ser. No. 61/730612 filed on Nov. 28, 2012 the content of which is relied upon and incorporated herein by reference in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2013/071190 | 11/21/2013 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 61730612 | Nov 2012 | US |
