DESCRIPTION

APPARATUS AND METHOD FOR EDGE PROCESSING OF A SHEET OF BRITTLE

MATERIAL

Technical Field

The present invention relates to an apparatus and method for processing an edge of a sheet of brittle material. More particularly, the present invention relates to an apparatus and method for rounding an edge of a sheet of brittle material, such as a glass sheet that can be used in a flat panel display.

Background Art

Liquid crystal displays (LCDs) are passive flat panel displays which depend upon external sources of light for illumination. They are manufactured as segmented displays or in one of two basic configurations, and in a basic sense consist of a liquid crystal material sandwiched between two substrates. The substrate needs

(other than being transparent and capable of withstanding the chemical conditions to which it is exposed during display processing) of the two types vary according to the addressing matrix. The first type is intrinsic matrix addressed, relying upon the threshold properties of the liquid crystal material. The second is extrinsic matrix or active matrix (AM) addressed, in which an array of diodes, metal-insulator-metal (MIM) devices, or thin film transistors (TFTs) supplies an electronic switch to each pixel. In both cases, two sheets of glass form the structure of the display, and requirements pertaining to surface quality are stringent. The separation between the two sheets is the critical gap dimension, of the order of 5-10 μm. The individual glass substrate sheets are typically less than about 0.7 mm in thickness.

Processing glass sheets that require a high quality surface finish like the ones used in flat panel displays, typically involves cutting the glass sheet into a desired shape and then grinding and/or polishing the edges of the cut glass sheet to

remove any sharp corners. Today the grinding and polishing steps are usually carried out on an apparatus known as a double edger or double edging machine with shaped grinding/polishing wheels which have shaped grooves about the circumference of the wheel . Such double edging machines are known and commercially available. Vendors include such companies as Bando Kiko Co., Ltd., Mitsubishi Heavy Industries, Fukuyama Co., and Glass Machinery Engineering.

During the grinding and polishing of the edges of a glass sheet using a double edging machine, the glass sheet must typically be constrained to keep the sheet rigid against the frictional forces applied by the grinding wheel. One commonly employed method is by pinching or sandwiching the sheet between two neoprene or rubber belts. The belts contact both surfaces of the glass sheet and cooperate to hold the glass sheet in place while the edges of the glass sheet are ground or polished by an abrasive wheel typically comprising a plurality of shaping grooves. The belts also transport the glass sheet through a feeding section of the machine, a grinding or polishing section of the machine, and an end section of the machine. This method of gripping, processing and conveying a glass sheet using a double edging machine has several disadvantages. First, the particles generated during edge processing (e.g. grinding) can be a major source of contamination on the surfaces of the glass sheet. Thus, the glass sheet requires extensive washing and drying at the end of the finishing process to remove the generated particles. Of course, the additional steps of washing and drying at the end of the finishing process impact the original cost for the finishing line and increases the cost of manufacturing. Secondly, the particles and chips caught between the belts and the glass sheet can severely damage the surfaces of the glass sheet. Sometimes this damage can be the source of a break during subsequent processing steps and results in poor process yields due to a reduced number of selects (good glass) that can be shipped to a customer.

In addition, grinding or polishing the edge using an abrasive wheel requires frequent maintenance if the process is to be stable. First, the abrasive wheel must be dressed frequently to maintain the appropriate ground edge shape and maintain grinding efficiency. Second, alignment of the sheet to another groove should be undertaken when an active groove is worn out. Finally, when all grooves have been used, the wheel must be replaced. As can be appreciated, in spite of these precautions, process variability resulting from grinding means the strength of the ground edge varies. Moreover, the down time associated with these maintenance activities increases production cost.

To address at least some of these concerns, the surfaces of the glass sheet can be protected by a plastic film to help prevent damage and contamination. But, if the source of contamination can be eliminated or at least minimized, then the plastic film is not needed and that would reduce the cost and complexity of the finishing process.

U.S. Patent Publication US2005/0090189 describes a process and apparatus for grinding and/or polishing the edge of a glass sheet wherein pressurized air is distributed through opposing porous plates to prevent particulate generated by the edge processing from contaminating the glass sheet, thereby eliminating the need for plastic coatings. In spite of this advance however, porous plates are subject to low air flow, limiting the effectiveness of the plates in preventing particulate contamination. Moreover, to obtain an effective seal at low air flow rates, the plates must be relatively wide, thus increasing the amount of glass overhanging the glass support and maintained between the plates. For thin glass sheets, such as are used in LCD display devices, vibration due to excess overhang can result in unacceptably rough processed edges .

Accordingly, there is a need for an apparatus and method which is relatively maintenance free, and that helps prevent particles and other contaminants that are generated during edge finishing from contaminating or damaging the two surfaces of

a sheet of brittle material, while providing for clean, chip- free processed edges. Moreover, minimizing the generated particle levels would reduce the load on the washing equipment downstream. These and other needs are satisfied by the apparatus and method of the present invention.

Disclosure of the Invention

The fusion downdraw method is capable of producing thin (on the order of less than about 0.7 mm in thickness), pristine sheets of glass ideal for the growing luminous, flat panel display industry. Manufacturing steps downstream of the glass sheet forming operations, such as finishing the edges of the glass sheet, may contaminate the sheet with glass particulate generated during the edge processing. One consideration therefore is the elimination of such contamination, either by reducing the production of contaminates, or by utilizing effective methods of removing contaminates. Accordingly, embodiments of the present invention provide a method and an apparatus for processing the edges of a sheet of brittle material, preferably a glass material, while renewing and maintaining the pristine nature of the sheet.

Advantages of embodiments of the current invention include: elimination of equipment down time, as would be necessary, for example, to redress conventional grinding wheels; a reduction in contamination through the use of a closed system; a reduction in force on the glass sheet which would otherwise be applied through a grinding wheel, particularly beneficial for very thin sheets of glass, and; with a reduction in force on the glass, a reduction in force needed to restrain the sheet.

Briefly described, embodiments of the method and apparatus, among others, can be implemented as described herein. Although the apparatus and methods described can be applied to a variety of materials, the various embodiments will be described hereinafter in the context of a sheet of glass.

In one embodiment according to the present invention, an apparatus for processing an edge of a sheet of brittle material is

disclosed comprising at least one nozzle for directing a stream of abrasive particles entrained in a fluid, in a direction toward the edge, and a wiping device positioned adjacent the edge, the wiping device emitting pressurized air from at least one slot to substantially prevent the abrasive particles from adhering to surfaces of the sheet of brittle material.

In another embodiment, a method for processing an edge of a sheet of brittle material is provided comprising forming an arcuate surface on the sheet of brittle material by directing at least one stream of abrasive particles from a nozzle against an edge of the sheet of brittle material to be processed, the at least one abrasive particle stream having an average grit size, directing a stream of pressurized air from at least one slot against the sheet of brittle material to substantially prevent the abrasive particles from adhering to the sheet of brittle material, and wherein a longitudinal axis of the at least one nozzle forms an angle between about 0 and 60 degrees with a plane containing a surface of the sheet of brittle material.

The invention will be understood more easily and other objects, characteristics, details and advantages thereof will become more clearly apparent in the course of the following explanatory description, which is given, without in any way implying a limitation, with reference to the attached Figures. It is intended that all such additional systems, methods features and advantages be included within this description, be within the scope of the present invention, and be protected by the accompanying claims .

Brief Description of the Drawings

FIG. 1 is a cross sectional side view of an embodiment of the present invention showing a slurry jet nozzle in relationship with the glass sheet being processed.

FIG. 2 is a close-up cross sectional side view of the glass sheet of FIG. 1 being processed.

FIG. 3 is a plot of radius of curvature of the abraded surface and glass removal as a function of nozzle angle.

FIG. 4 is a perspective view of a sample sheet of glass illustrating the method of measuring glass removal.

FIG. 5 is a plot of radius of curvature and glass removal as a function of air pressure used to accelerate the slurry. FIG. 6 is a plot showing glass removal as a function of air pressure for two different separations between the abraded surface and the nozzle exit orifice.

FIG. 7 is a plot of radius of curvature of the abraded surface as a function of air pressure for two different separations between the abraded surface and the nozzle exit orifice.

FIG. 8 is a plot of radius of curvature of the abraded surface as a function of air pressure for two different separations between the abraded surface and the nozzle exit orifice.

FIG. 9 is a plot of glass removal as a function of head (slurry jet nozzle) speed relative to the glass sheet for two different separations between the abraded surface and the nozzle exit orifice.

FIG. 10 is a plot of radius of curvature of the abraded surface as a function of head speed for three different angles between the slurry jet nozzle and the glass sheet.

FIG. 11 is a plot of radius of curvature of the abraded surface as a function of air pressure for two different grit sizes.

FIG. 12 is a plot of glass removal as a function of head speed for the two grit sizes of FIG. 11. FIG. 13 is a cross sectional side view of a glass sheet being processed by two slurry jet nozzles disposed opposite on opposite side surfaces of the sheet.

FIG. 14 is a cross sectional side view of a glass sheet being processed by two pair of slurry jet nozzles, a pair of slurry jet nozzles disposed left of the glass sheet and a pair of slurry jet nozzles disposed right of the glass sheet.

FIG. 15A is a perspective view of a plurality of slurry jet nozzles arranged sequentially along a single edge of a glass sheet, oriented with the same angles relative to the plane of the glass sheet.

FIG. 15B is a perspective view of a plurality of slurry jet nozzles arranged sequentially along a single edge of a glass sheet, oriented at different angles relative to the plane of the glass sheet. FIG. 16 is a cross sectional side view of an embodiment of the present invention including wiping devices for removing and preventing the adherence of particulate and other debris from the glass sheet, and a shroud for enclosing a space about an edge of the glass sheet.

Best Mode for Carrying Out the Invention

In the following detailed description, for purposes of explanation and not limitation, example embodiments disclosing specific details are set forth to provide a thorough understanding of the present invention. However, it will be apparent to one having ordinary skill in the art, having had the benefit of the present disclosure, that the present invention may be practiced in other embodiments that depart from the specific details disclosed herein. Moreover, descriptions of well-known devices, methods and materials may be omitted so as not to obscure the description of the present invention. Finally, wherever applicable, like reference numerals refer to like elements.

Referring to FIGS. 1-2, there is disclosed in accordance with an embodiment of the present invention an apparatus 10 for processing at least one edge 12 of a glass sheet 14. Although apparatus 10 is described herein as being used to remove material from an edge of a glass sheet, it should be understood that apparatus 10 can also be used to process other types of brittle materials such as glass-ceramic material, ceramic material or polymer materials such as polycarbonates. As used herein, a brittle material is a material that absorbs little energy prior to fracture, and shows little or no evidence of plastic deformation prior to fracture. Brittle materials typically fail in tension rather than shear. However, the present invention may also be used with ductile materials such as metal. Accordingly, apparatus 10 of

the present invention should not be construed in a limited manner. For the purposes of the following description, processing of a glass sheet will be described.

Glass sheet 14 comprises two flat, substantially parallel surfaces, hereinafter sides 16 and 18. Glass sheet 14 has a thickness "y" defined as the distance between the parallel sides. Although ordinarily one would consider the edge of a sheet of glass to be the outside perimeter of the sheet, as used herein, an edge is defined as a line or line segment that is the intersection of two surfaces, edge surface 20 and side 16 for example. Edge surface 20 represents a surface of the glass sheet between two edges, e.g. edges 12 and 22, and is generally, although not necessarily, orthogonal to each of sides 16, 18. Practically, edge surface 20 is disposed between two edges, 12 and 22, each of the two edges being themselves adjacent to a side of glass sheet 14. Glass sheet 14 may have one or more edge surfaces. For example, a sheet of glass having a circular shape has only a single edge surface. A pentagonal sheet of glass would have 5 edge surfaces. Glass sheets used in display applications are typically rectangular in shape, and therefore have four edge surfaces and consequently eight edges, two edges associated with each edge surface.

Apparatus 10 includes at least one hollow nozzle or slurry jet device 24 for directing a stream 26 of abrasive particles at an edge of glass sheet 14. The abrasive particles are preferably contained or suspended in a fluid, such as water, thereby forming slurry. The slurry may thereafter be accelerated by entraining the slurry in a stream of gas, such as air supplied to the slurry under pressure from a suitable supply (not shown) , and expelling the slurry from an exit orifice 28 of nozzle 24 in a high velocity stream or jet of abrasive particles 26. The abrasive particles impinging on the glass sheet abrade the glass and incrementally remove glass material from the sheet. Accordingly, apparatus 10 may be used to remove glass from glass sheet 14 at a particular edge, thereby replacing the sharp edge with an arcuate surface 30 which connects side 16 of glass sheet 14 with edge surface 20.

Glass sheet 14 may be translated relative to the stream of abrasive particles, or the glass sheet may be held stationary and the stream of abrasive particles translated relative to the glass sheet, in any event creating relative motion between glass sheet 14 and glass particle stream (e.g. slurry) 26. As the stream of abrasive particles is translated along edge 12, the stream removes glass from the edge, forming arcuate edge surface 30.

As shown in FIG. 1, nozzle 24 has a longitudinal axis 32, and is preferably aligned such that longitudinal axis 32 forms an angle α relative to plane 34 parallel to surface 16 of the glass sheet. In the illustration of FIG. 1, plane 34 is parallel to and substantially contains surface 16 of glass sheet 14. Note that nozzle 24 is directed at edge 12 of glass sheet 14 in a direction leading toward the body of the glass sheet rather than a direction away from the glass sheet. Nozzle 24 may have a circular exit orifice or nozzle 24 may have a more elliptical or flattened exit orifice. A flattened exit orifice (e.g. a large aspect ratio), provides greater coverage of edge 12, and thereby decreases processing time. The choice of nozzle angle α is dependent upon the desired operating conditions - e.g. the amount of glass removal, radius of curvature of the abraded edge, etc. For example, it has been found that maximum glass removal can be obtained at an angle a of approximately 30 degrees relative to plane 34, while a more arcuate abraded surface can be formed at an angle of about 60 degrees relative to plane 34. Shown in FIG. 3 is a plot representing the radius of curvature of abraded surface 30 relative to the angle α of nozzle 24 to plane 34 and the amount of material removed from edge 12. As used herein, the term "abraded surface" will refer to the arcuate surface that remains after the edge as previously defined has been abraded. The glass removal was determined by measuring the distance d from processed edge 35 to unprocessed reference surface 36, as illustrated in FIG. 4. In the exemplary illustration of FIG. 4, reference surface 36 may be synonymous with edge surface 20. The data was obtained by directing a #800 grit

size alumina slurry at an edge of a sheet of glass approximately 0.7 mm in thickness. The nozzle was translated along an edge of the glass sheet at a speed of about 100 mm/s, and the distance δ between exit orifice 28 of nozzle 24 and edge 12 of glass sheet 14 was about 10 mm. Two passes were made by the nozzle, one pass in each of two opposite directions along edge 12. Two air pressures were evaluated, 0.15 MPa represented by curves 38 (radius) and 40 (removal) in FIG. 3, and 0.2 MPa represented by curves 42 and 44, respectively. Angle α was varied from between about 0 degrees to about 120 degrees. As indicated, maximum material (glass) removal was obtained with an angle a of about 30 degrees, while the maximum radius of curvature of abraded surface 30 was obtained with an angle α of about 60 degrees . Other factors influencing material removal properties include the air pressure used to accelerate the slurry, distance δ between the nozzle and abraded surface 30, head speed (or the rate of movement of the nozzle relative to the glass edge being processed), and abrasive size (i.e. grit size) .

FIG. 5 shows the relationship between air pressure and glass removal. A slurry having an average grit size of #800 was accelerated from a nozzle moving along an edge of a sheet of glass approximately 0.7 mm thick at a speed of about 100 mm/s relative to the glass sheet. The distance between exit orifice 28 of the nozzle and glass sheet 14 was about 10 mm and the angle between the longitudinal axis of the nozzle and plane 34 was 0 degrees. Two passes were made by the nozzle, one pass in each pf two opposite directions along the edge. As indicated by fitted curve 45, as the air pressure propelling the slurry was increased from less than about 0.05 MPa to about 0.25 MPa, the removal rate increases dramatically. The data also show an increase in the radius of curvature of the abraded surface, indicated by curve 46, as would be expected with the increasing removal of material.

FIG. 6 shows a relationship between the rate of material removal and air pressure for two different distances between the nozzle exit orifice and the glass edge (2 mm and 10 mm) , and FIG. 7 depicts the radius of curvature of abraded surface 30 as a function

of air pressure for the same two distances between the nozzle exit orifice and the edge. The alumina slurry had an average grit size of #800, and was directed at the edge of the glass sheet at an angle of 0 degrees. The nozzle was translated along the edge at a speed of about 100 mm/s relative to the glass. Two passes were made by the nozzle, one pass in each of two opposite directions along the edge. As indicated, there was virtually no change in the amount of glass removal when varying the distance between the nozzle and the glass from 2 mm to 10 mm, as indicated by the two overlapping curves 37 and 39. However, as shown in FIG. 7, when the distance between the nozzle and the glass was about 2 mm, the radius of curvature of the abraded surface 30 increased nonlinearly with air pressure, as demonstrated by curve 48. When the distance between the nozzle and the glass was increased to 10 mm, the radius of curvature of the glass edge increased approximately linearly, as depicted by curve 50. Finally, FIG. 8 shows the variation in radius of curvature of abraded surface 30 as a function of air pressure for the same nozzle-to-glass distances described above 2 mm (curve 51a) and 10 mm (curve 51b) , but at a nozzle angle of 60 degrees. All other conditions are as reported above. In this case, there was only a small difference between the radii of curvature which were obtained.

FIG. 9 illustrates material removal as a function of nozzle (head) speed for two different distances, 2 mm (curve 55a) and 10 mm (curve 55b) between the nozzle and the glass edge. As before, the sheet of glass was approximately 0.7 mm in thickness. The nozzle was translated along the edge at speeds between about 50 mm/s and 200 mm/s for two different distances between the nozzle and the glass edge. The slurry had an average grit size of #800, and the air pressure used to accelerate the slurry was 0.15 MPa. The nozzle was oriented at an angle α of 0 degrees. As shown in the figure, the amount of material removed varies approximately linearly with the translation speed of the nozzle along the glass edge, with very little dependency on the distance between the nozzle and the edge. Qn the other hand, FIG. 10 depicts material

removal as a function of nozzle speed for three different angles α

(0 degrees, 60 degrees and 120 degrees) at a set nozzle distance of

10 mm. Two passes were made by the nozzle, one pass in each of two opposite directions along the edge. As indicated by FIG. 10, results varied widely. At a nozzle angle of 120 degrees, radius of curvature showed little or no dependence on nozzle speed. However, at a nozzle angle of 60 degrees, and 0 degrees, a dependency was observed which was similar, with a larger radius of curvature of abraded surface 30 obtained for a 60 degree angle than a 0 degree angle.

To evaluate the impact of abrasive size (grit size) , radius of curvature was examined as a function of air pressure for two different grit sizes, #800 and #2000. The nozzle was oriented at an angle α of 60 degrees, the distance between the nozzle exit orifice and the glass edge was 10 mm, and the nozzle was translated at a speed of about 10 mm/s along the edge. As shown in FIG. 11, the radius of curvature of abraded surface 30 obtained at a given air pressure for the #800 grit abrasive (curve 57a) is nearly three times the radius of curvature obtained using a #2000 grit abrasive (curve 57b) .

The impact of abrasive size on glass removal was also investigated and depicted in FIG. 12. Abrasive size was examined as a function of air pressure for two different grit sizes, #800 (curve 59a) and #2000 (curve 59b) . The nozzle was oriented at an angle α of 0 degrees, the distance between the nozzle exit orifice and the glass edge was 10 mm, the nozzle was translated at a speed of about 10 mm/s along the edge, and the air pressure was 0.15 MPa. Two passes were made by the nozzle, one pass in each of two opposite directions along the edge. As indicated, the larger particle size (i.e. #800 grit) resulted in more glass being removed than the #2000 grit for a given translational speed of the nozzle relative to the glass edge.

In another embodiment, multiple slurry jet nozzles 24 may be used to process two or more edges of a sheet of glass, preferably simultaneously. As shown in FIG. 13, one slurry jet nozzle 24 may

be used to process edge 12 between first side 16 of glass sheet 14 and edge surface 20, while a second slurry jet nozzle 24 is used to process edge 22 between second side 18 of glass sheet 14 and edge surface 20. Moreover, multiple slurry jet nozzles may be used to process multiple edges of the glass. For example, FIG. 14 shows a pair of slurry jets disposed on opposite sides of glass sheet 14 adjacent edges 16, 18 and a second pair of slurry jets disposed opposingly. In the arrangement illustrated in FIG. 14, glass sheet 14 may be translated relative to the slurry jets, or the slurry jets may be translated relative to the glass sheet. Simultaneous processing of multiple edges is contemplated. For example, moving glass sheet 14, e.g. into or out of the drawing as viewed, would simultaneously process both upper and lower edges on both the right hand and left hand sides of glass sheet 14. In still another embodiment depicted in FIG. 15A, a plurality of nozzles 24 are shown each nozzle 24 arranged to achieve a different result. For example, multiple nozzles 24 may be arranged adjacent each other, and supplied with a different grit size in sequence (e.g. with a monotonically decreasing grit size) so that an edge is sequentially processed. Thus, smaller amounts of material may be removed with increasingly finer grit slurries in sequence during a given translation between the sheet and the nozzles. Suitable grit sizes range between about #400 and #4000. Moreover, other process variables, as described above, may be varied between the different nozzles. For example, the slurry for each nozzle may be accelerated with a gas at a different pressure, or each nozzle may be a different distance from the glass edge than an adjacent nozzle. The exact arrangement and process conditions are determined by the desired characteristics of the edge, and may be readily determined by the skilled artisan without undue experimentation. Relative motion between the plurality of adjacent nozzles and edge 12, as represented by arrow 53, results in the edge being sequentially abraded along the length of the edge. The plurality of nozzles may be translated, or the glass sheet, or both the glass sheet and the nozzles may be translated to provide the

relative motion. Additionally, the nozzles of the plurality of nozzles may form different angles (angle a) relative to the edge being processed, as illustrated in FIG. 15B. Advantageously, varying angle α may result in improved consistency of edge shape (the shape of abraded surface 30) .

Apparatus 10 may further comprise at least one barrier or wiping device 54 illustrated in FIG. 16. The at least one wiping device 54 is capable of substantially preventing particles and other contaminants, which may be generated when processing an edge of glass sheet 14, from reaching or adhering one or both of surfaces 16 and 18 of glass sheet 14.

In a preferred embodiment, wiping device 54 may comprise an air knife arrangement such as that disclosed in U.S.

Patent Application No. 60/752858, filed on December 21, 2005, the contents of which are incorporated herein by reference. Wiping device 54 comprises at least one slot 56 through which a high velocity gas 58, such as air, is directed at the glass surface as a curtain of gas to remove particulate which may accumulate on the glass surface. This particulate may be abrasive particles from the slurry, glass chips removed from the glass sheet during processing of the sheet, dust, or any other foreign material which may be deposited on the surfaces of the glass sheet. The curtain of gas is typically directed at the surface of the glass opposite the slot such that the curtain of air impinges on the glass surface at an angle. That is, it is desirable to direct the curtain of air at the surface of the glass sheet at an angle other than 90 degrees (perpendicular to the surface of the glass sheet) . Washing jets may also be incorporated into the wiping device to aid in the removal of particulate from the glass surface. A cleaning fluid 61, such as water, is directed from cleaning jets 63 at the surface of the glass sheet. Again, it is preferred that the cleaning fluid be directed at the surface of the glass sheet at an angle other than 90 degrees.

As also shown in FIG. 16, shroud 60 may be employed to collect spent slurry and particulate generated by the glass removal process, as well as cleaning fluid which may be dispensed by the one or more wiping devices which may be used. The shroud effectively encloses at least a portion of the glass sheet edges as they are processed by the slurry jets, and may connect with the wiping device or devices, thereby creating a substantially enclosed space between the shroud and the wiping device. The shroud is designed to allow the edges of the glass sheet to be translated through the shroud. Thus, the shroud includes an opening through which the glass sheet may traverse. Preferably, the shroud is connected to a vacuum source (not shown), to assist in the removal of particulate (e.g. slurry and glass), and cleaning fluid, from the vicinity of the glass surfaces. The draw of air from the interior of the shroud is indicated by arrow 62. Provision may also be made for entry of the one or more slurry delivery nozzles through the shroud into the interior region 64 enclosed by the shroud. Drawing a vacuum within region 64 may advantageously result in a supplemental air flow across surfaces of the glass sheet, as indicated by arrows 66, thereby assisting the function of air curtains 58.

It should be emphasized that the above-described embodiments of the present invention, particularly any "preferred" embodiments, are merely possible examples of implementations, merely set forth for a clear understanding of the principles of the invention. Many variations and modifications may be made to the above-described embodiments of the invention without departing substantially from the spirit and principles of the invention. For example, although the example embodiments illustrated herein are shown in horizontal configurations, the present invention is equally effective in a vertical orientation. All such modifications and variations are intended to be included herein within the scope of this disclosure and the present invention and protected by the following claims .