Abstract:
A method of conveying a glass substrate utilizing an improved non-contact lifting device. The non-contact lifting device employs the Bernoulli effect to create a pressure differential across the glass substrate. The Bernoulli device of the present invention comprises an increased holding or lifting power, and reduces the opportunity for contact between the device and the glass substrate if the device is tilted with respect the plane of the glass substrate surface.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of priority under 35 U.S.C. § 119(e) of U.S. Provisional Application Ser. No. 60/931,779 filed on May 25, 2007. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates to an apparatus for holding and/or conveying a thin substrate sheet, and in particular a large glass sheet. 
         [0004]    2. Technical Background 
         [0005]    A variety of conveying methods are known for transporting and manipulating thin substrates, and in particular circular semiconductor substrates. However, semiconductor substrates are generally on the order of about 15 cm in diameter and not prone to significant flexure. In many of these semiconductor applications, pickup or “end effector” devices operate on the Bernoulli principal, and a single Bernoulli device (e.g. chuck) is sufficient to accommodate the substrate. 
         [0006]    Display devices, on the other hand, such as liquid crystal display devices for use in televisions, continue to grow in size, requiring ever larger glass substrate panels from which the devices are manufactured. Some substrate panels can have a one-side surface area in excess of 3 square meters, and in some cases at least about 10 square meters, yet have a thickness equal to or less than 0.7 mm. Handling such large panels of exceptionally thin glass is a challenge in and of itself. However, compounding the difficulty is that the surface of the glass must be maintained in as pristine a condition as possible. Thus, customer requirements directed to the surface condition of the substrate panels are exceptionally stringent. 
         [0007]    One glass making process in particular that is capable of producing extremely large sheets of very thin glass is the fusion downdraw process. Briefly, molten glass is flowed over converging forming surfaces, rejoining at the bottom of the converging surfaces and drawn to form a thin ribbon of glass. The ribbon solidifies as it descends, and is eventually separated into individual glass sheets at the bottom of the drawing area. As can be appreciated, the process is continuous, and the solid glass ribbon at the bottom of the draw area is intimately connected to the viscous ribbon of glass flowing from the bottom of the converging forming surfaces. Thus, motion of the ribbon at the bottom of the draw, e.g. during the cutting (separating) process may be translated upward to the viscous region of the ribbon. To wit, this motion can result in stresses that may become frozen into the solidifying ribbon, and ultimately manifest themselves as distortion in the separated glass sheet. Moreover, the glass ribbon at the bottom of the draw, while cooled to the point that the glass is solid, is nevertheless still quite hot (approximately 350° C.), further complicating handling. In other parts of the process, the surface condition of the glass sheet may vary, e.g. dry, wet or coated with a plastic film. Systems designed for transporting and manipulating semiconductor substrates are incapable of transporting such large, thin substrate sheets under such diverse conditions. 
         [0008]    It should also be noted that the ribbon of glass descending from the converging forming surfaces takes on a slight curve or bow across the width of the ribbon (transverse to the direction of flow). Thus, the method used to acquire the glass sheet on the draw should be capable of accommodating this curvature. 
         [0009]    Today when a glass sheet (e.g., liquid crystal display (LCD) glass sheet) is manufactured a robot is often used to move the glass sheet from one point to another point in a glass manufacturing facility. A robot, as used herein, refers generally to a machine (e.g. electrical, hydraulic, pneumatic or a combination thereof) that performs predetermined tasks automatically, usually under the control of a computer. Robots find extensive use in manufacturing environments to perform rote or precision tasks, and are heavily used, for example, in the automotive industry. Robots often include articulated arms or appendages with specialized ends to facilitate the intended function. For example, the arms may include devices for grasping, drilling, cutting and so forth. The robot used in moving glass sheets typically comprises an end effector that uses a plurality of suction cups to engage and hold the outside edges or non-quality area of the glass sheet. The outside edges are later removed and discarded, leaving only the interior “quality” area of the sheet. The suction cups need to engage the glass sheet on the outer edges only because if they contact the glass sheet in the center portion of the quality area then unacceptable defects or contamination may be created in the glass sheet. Because the glass sheet is hot, suction cups also deteriorate quickly, and must be constantly replaced, adding to manufacturing costs. Furthermore, engagement of the suction cups with the glass sheet causes undesirable vibration of the sheet. 
         [0010]    As customers require larger and larger glass sheets it becomes increasingly more difficult for the robot to engage and move the glass sheet without causing motion in the center portion of the glass sheet. The motion in the center portion of the glass sheet is caused because there is a long, unsupported span in the middle of the glass sheet. Of course, the glass sheet can possibly break or even fall off the suction cups if the robot causes too much motion in the glass sheet. One way to minimize the motion in the glass sheet is to limit the speed of the robot. A drawback of this approach is that a large cycle time is required by the robot to move the glass sheet from one point to another point in the glass manufacturing facility. 
         [0011]    While every effort is made to maintain conditions of cleanliness in the manufacturing operation, the danger of particulate contamination of the suction cups, however pliant the suction cups might be, is a constant danger, as such particulate can damage the substrate surface. To wit, anytime there is contact with the surface of the substrate, the potential for damaging the substrate is present. Thus, there has been considerable effort to develop non-contact methods of handing large glass substrates. 
         [0012]    US Patent Publication 2006/0042315, for example, discloses the use of Bernoulli chucks to support the quality area of the glass sheets, thereby augmenting the use of suction cups. However, the sheer size and weight of present day, and anticipated future, generations (e.g. sizes) of glass sheet, and the suction cup issues above, begs for an enhancement to this approach. 
       SUMMARY 
       [0013]    In accordance with an embodiment of the present invention an aero-mechanical device is disclosed comprising a body portion comprising an inlet for receiving a gas, a cavity defined by the body portion in fluid communication with the inlet for equalizing a velocity of the gas, an outlet orifice in fluid communication with the cavity for expelling the gas and a distribution disk for distributing the gas expelled through the outlet orifice and wherein a radius of the cavity is equal to or greater than a radius of the distribution disk. 
         [0014]    In another embodiment, a system for conveying a glass sheet is described including a robot comprising a plurality of aero-mechanical devices to support and hold the glass sheet without contacting the sheet, each of the plurality of aero-mechanical devices comprising a body portion defining a cavity disposed therein, an inlet orifice and an outlet orifice in fluid communication with the cavity for respectively receiving and expelling a gas, and a distribution disk for distributing the expelled gas, a temperature control system for regulating a temperature of the gas emitted from the plurality of aero-mechanical devices, and wherein a radius of the cavity is equal to or greater than a radius of the distribution disk. 
         [0015]    In still another embodiment, an apparatus for conveying a glass sheet is disclosed comprising a robot, a plurality of aero-mechanical devices connected to the robot, each of the plurality of aero-mechanical devices comprising a body portion defining a cavity disposed therein, an inlet orifice and an outlet orifice in fluid communication with the cavity for respectively receiving and expelling a gas, a distribution disk for distributing the expelled gas and a pickup surface, and wherein a diameter of the cavity is equal to or greater than a diameter of the distribution disk. 
         [0016]    In another embodiment, a method of acquiring a glass sheet is described comprising providing a glass sheet having opposing first and second sides and an edge substantially perpendicular to the sides, moving an aero-mechanical device such that a pickup surface of the aero-mechanical device is at an index position proximate the first side of the glass sheet, and moving the pickup surface from the index position in a direction toward the first side of the glass sheet while simultaneously increasing a pressure of a gas supplied to the aero-mechanical device to acquire and hold the glass sheet without contacting the sheet. 
         [0017]    It is to be understood that both the foregoing general description and the following detailed description present embodiments of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated into and constitute a part of this specification. The drawings illustrate an exemplary embodiment of the invention and, together with the description, serve to explain the principles and operations of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0018]      FIG. 1  is a diagrammatic view of an exemplary glass manufacturing system using a glass handling system in accordance with an embodiment of the present invention. 
           [0019]      FIG. 2A  is a side view of a portion of the glass manufacturing system of  FIG. 1  showing the traveling anvil machine (TAM). 
           [0020]      FIG. 2B  is a side view of a portion of the glass manufacturing system of  FIG. 1  showing the conveyor. 
           [0021]      FIG. 3A  is a side cross sectional view of an aero-mechanical device according to an embodiment of the present invention. 
           [0022]      FIG. 3B  is a cross sectional view of a portion of the aero-mechanical device of  FIG. 3A   
           [0023]      FIG. 4  is a cross sectional view of another aero-mechanical device according to an embodiment of the present invention. 
           [0024]      FIG. 5A  is a cross sectional view of still another aero-mechanical device according to an embodiment of the present invention. 
           [0025]      FIG. 5B  is a cross sectional view of a portion of the aero-mechanical device of  FIG. 5A . 
           [0026]      FIG. 6A  is a side view, in partial cross section, of a portion of the glass manufacturing system of  FIG. 1  using yet another aero-mechanical device according to an embodiment of the present invention. 
           [0027]      FIG. 6B  is a cross sectional view of a portion of the glass manufacturing system of  FIG. 1  showing a device for supporting at least a portion of the weight of the glass sheet by a contact method. 
           [0028]      FIG. 6C  is a cross sectional view of a portion of the glass manufacturing system of  FIG. 1  showing another device for supporting at least a portion of the weight of the glass sheet by a non-contact method. 
           [0029]      FIG. 7A  is a front view of a portion of the glass manufacturing system of  FIG. 1  showing the use of the aero-mechanical devices of  FIG. 6A  is a full-frame arrangement. 
           [0030]      FIG. 7B  is a front view of a portion of the glass manufacturing system of  FIG. 1  showing the use of the aero-mechanical devices of  FIG. 6A  in a partial frame arrangement. 
           [0031]      FIG. 8  is a diagrammatic view of a portion of the exemplary glass manufacturing system of  FIG. 1  including a gas temperature control system. 
           [0032]      FIG. 9  is a diagrammatic view of a portion of the exemplary glass manufacturing system of  FIG. 1  including a gas flow control system. 
           [0033]      FIG. 10  is a diagrammatic view of a portion of the exemplary glass manufacturing system of  FIG. 1  including a position control system. 
           [0034]      FIG. 11  is a plot comparing the vibration generated by a method wherein the desired final air pressure is applied to the aero-mechanical device before approaching the glass sheet, to the vibration generated by a method according to an embodiment of the present invention wherein the aero-mechanical device is brought to a pre-determined distance from the surface of the glass sheet, then pressure ramped up gradually as the aero-mechanical device is moved toward the surface of the glass sheet. 
           [0035]      FIG. 12  is a superimposed side view of a conventional aero-mechanical device and an aero-mechanical device according to an embodiment of the present invention illustrating the various reference surfaces relative to  FIGS. 13 and 14  below. 
           [0036]      FIG. 13  is a plot showing the modeled velocity of air from a conventional aero-mechanical device, without a rounded lower edge, relative to the reference surfaces depicted in  FIG. 12 . 
           [0037]      FIG. 14  is a plot showing the modeled velocity of air from an aero-mechanical device according to an embodiment of the present invention, with a rounded lower edge, relative to the reference surfaces depicted in  FIG. 12 . 
           [0038]      FIG. 15  is a plot showing air pressure, as a function of radial distance from the central longitudinal axis of a conventional aero-mechanical device and an aero-mechanical device according to an embodiment of the present invention, between a reference surface (relative to  FIG. 12 ) of the devices and an adjacent surface of a glass sheet. 
       
    
    
     DETAILED DESCRIPTION  
       [0039]    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. 
         [0040]    A fusion glass sheet forming process (e.g., downdraw process) forms high quality thin glass sheets that can be used in a variety of devices like flat panel displays. The fusion process is the preferred technique used today for producing glass sheets that are used in flat panel displays. Glass sheets formed by a fusion process have surfaces with superior flatness and smoothness when compared to glass sheets produced by other methods. A glass manufacturing system  100  that uses a fusion process to make a glass sheet is briefly described below, but for a more detailed description of the fusion process reference is made to U.S. Pat. Nos. 3,338,696 and 3,682,609. The contents of these two patents are incorporated herein by reference. 
         [0041]    Referring to  FIG. 1 , there is shown a diagram of an exemplary glass manufacturing system  100  that uses the fusion process and glass handling system  102  of the present invention to make finished glass sheet  106 . As shown, glass manufacturing system  100  includes melting vessel  110 , fining vessel  115 , mixing vessel  120  (e.g., stir chamber  120 ), delivery vessel  125  (e.g., bowl  125 ), fusion draw machine (FDM)  140   a , traveling anvil machine (TAM)  150 , conveyor  160  and glass handling system  102 . Melting vessel  110  is where the glass batch materials are introduced, as shown by arrow  112 , and melted to form molten glass  126 . Fining vessel  115  (e.g., finer tube  115 ) has a high temperature processing area that receives molten glass  126  (not shown at this point) from melting vessel  110  and in which bubbles are removed from molten glass  126 . Fining vessel  115  is connected to mixing vessel  120  (e.g., stir chamber  120 ) by finer to stir chamber connecting tube  122 . Mixing vessel  120  is connected to delivery vessel  125  by stir chamber to bowl connecting tube  127 . Delivery vessel  125  delivers molten glass  126  through downcorner  130  into FDM  140   a  which includes inlet  132 , forming vessel  135  (e.g., isopipe  135 ), and pulling roll assembly  140 . As shown, molten glass  126  from downcorner  130  flows into inlet  132  which leads to forming vessel  135 . Forming vessel  135  includes opening  136  that receives molten glass  126  which flows into trough  137  and then overflows and runs down two opposing sides  138   a  and  138   b  of forming vessel  135  before fusing together at root  139 . Root  139  is where the two opposing sides  138   a  and  138   b  of forming vessel  135  converge and where the two overflow walls of molten glass  126  rejoin (e.g., fuse) before being drawn downward by pulling roll assembly  140  to form glass sheet  105 . TAM  150  cuts drawn glass sheet  105  into distinct pieces of glass sheet  106 . At this point, the glass sheet  106  is hot—significantly above room temperature. Glass handling system  102 , and in particular enhanced robot  104 , then acquires cut glass sheet  106  and moves glass sheet  106  from TAM  150  to conveyor  160  which is located in a Bottom of the Draw (BOD) area. This area is referred to as the Hot BOD (HBOD), as glass sheet  106  is still hot. Conveyor  160  then conveys glass sheet  106 , which cools along the way, through a couple of process steps. At end  162  of conveyor  160 , which is referred to as the Cold End, glass sheet  106  is packaged along with other glass sheets  106  so they can be sent to customers. A detailed discussion of the operation and different components of the glass handling system  102  and enhanced robot  104  is provided below with respect to  FIGS. 2A-2B . 
         [0042]    Referring to  FIGS. 2A and 2B , there are shown side views of portions of glass manufacturing system  100  shown in  FIG. 1  which are used to help explain how enhanced robot  104  acquires and moves cut glass sheet  106  from TAM  150  to conveyor  160 . As shown, enhanced robot  104  includes a frame  202  and one or more aero-mechanical devices  204  connected to frame  202  to couple to and hold glass sheet  106  and then move glass sheet  106  from TAM  150  to conveyor  160 . In one embodiment, additional aero-mechanical devices  206  contact and support the outer edges or non-quality area of the glass sheet  106 . The one or more aero-mechanical devices  204  receive gas from a gas supply unit (not shown) and emit gas toward the center portion or quality area of glass sheet  106  in a manner that enables the one or more aero-mechanical devices  204  to support and hold the center portion of glass sheet  106  without contacting the center, quality area of glass sheet  106  while glass sheet  106  is moved from TAM  150  to conveyor  160 . In the embodiment illustrated in  FIGS. 1-2 , additional aero-mechanical devices  206  may be employed such that the additional devices  206  contact and support the outer edges or non-quality area of glass sheet  106 . A description as to how the one or more aero-mechanical devices  204  are able to acquire and hold the quality area of glass sheet  106  without contacting the quality area of glass sheet  106  is provided below. 
         [0043]    Aero-mechanical device  204  is configured such that gas from the gas supply unit flows through device  204  in a manner that creates a gas film on one side of glass sheet  106  such that if glass sheet  106  moves too far away from a face or pickup surface of aero-mechanical device  204  then a suction force (Bernoulli suction force) created by gas emitted from aero-mechanical device  204  pulls glass sheet  106  back to aero-mechanical device  206 . And, if glass sheet  106  moves too close to a pickup surface of aero-mechanical device  204  then a repulsive force caused by the gas emitted from aero-mechanical device  204  pushes glass sheet  106  away from aero-mechanical device  204 . It is the balance between the suction force and the repulsion force that enables aero-mechanical device  204  to hold glass sheet  106  from a single side at a given position without having to touch glass sheet  106 . 
         [0044]    Prior art aero-mechanical devices have not provided the holding force needed to acquire and securely hold very large sheets of glass, for example glass sheets that approach or exceed 10 square meters, particularly aero-mechanical devices which operate on the Bernoulli principal. Conventional Bernoulli aero-mechanical devices tend to have a squared-off edge on the pickup surface (the surface of the aero-mechanical device closest to the glass sheet, and incorporate narrow gas distribution passages within the device. In the first instance, a squared-off edge may damage glass sheets with inadvertent contact. This is particularly true when the fly height (the distance between the closest point of the pickup surface and the substrate being acquired) is very small (typically less than about 100 μm) and the pickup surface is not substantially parallel with a plane of the pickup surface, remembering that for the still-hot glass ribbon descending from the isopipe, the ribbon or sheet generally has a width-wise curvature. This may occur, for example, as the aero-mechanical device  204  is engaging or disengaging with the glass sheet  106 . It has been found that with conventional devices having as little as a 2° angular offset between the surface of the glass sheet and the proximal chuck surface, an edge of the conventional Bernoulli chuck can contact the sheet prior to the chuck stabilizing itself and forming the proper fly height. In the second instance, it has been found that the abrupt (e.g. sharp) edge at the outer circumference of the pickup surface results in a reduced holding force on the substrate. 
         [0045]    Shown in  FIGS. 3A-3B  is an exemplary aero-mechanical device  204  according to an embodiment of the present invention. Aero-mechanical device  204  comprises body portion  208  defining a cavity  210  interior to the body portion and at least one inlet port  212  for receiving a supply of pressurized gas from the gas supply unit through fitting  213 . Preferably, the pressurized gas is clean, dry air. That is, the pressurized gas should be filtered and free of moisture and/or oil. It will hereinafter be assumed, for purposes of description and not limitation, that the pressurized gas supplied to cavity  210  is air. Since the supplied gas continuously issues from aero-mechanical device  204  during use, air serves as an inexpensive, non-polluting working fluid. 
         [0046]    Body portion  208  is preferably cylindrical in character and comprises a longitudinal axis  216  and an outside surface  218  concentric with longitudinal axis  216 . Body portion  208  also includes a top surface  220  and a bottom or pickup surface  222 . Inlet port  212  is in fluid communication with cavity  210 . Fitting  213  may be any suitable conventional fitting for connecting to a gas supply line (not shown). In some embodiments, inlet port  212  is concentric with longitudinal axis  216  of the body portion. As best seen in  FIG. 3B  illustrating the circled detail in  FIG. 3A , at least one outlet port  228  is also in fluid communication with cavity  210 . Pickup surface  222  is preferably non-planar, and as illustrated in  FIG. 3A , comprises a central depression  230 . 
         [0047]    In accordance with the present embodiment, aero-mechanical device  204  further comprises a flow guide or distribution disk  232  centrally disposed within depression  230 . Distribution disk  232  is generally circular in shape with a central axis coincident with longitudinal axis  216 , and may be attached to body portion  208  by pressing a portion of the disk structure into an appropriate mating structure within the body portion. For example, distribution disk  232  may comprise a cylindrical pedestal  233  on a surface thereof which is pressed into a suitably shaped opening  235  in body portion  208 . The fit should be sufficiently tight to hold distribution disk  232  to body portion  208  during operation of the aero-mechanical device  204 . 
         [0048]    Distribution disk  232  further comprises a groove or distribution channel  236  for distributing pressurized air received from cavity  210  through the at least one outlet port  228 . Preferably distribution channel  236  is disposed in an “upper” surface of the disk, adjacent body portion  208  in the assembled aero-mechanical device  204 , as seen in  FIG. 3B . Thus, the at least one outlet port  228  connects cavity  210  with distribution channel  236 . Pressurized gas (e.g. air) from cavity  210  is fed by outlet port  228  into distribution channel  236 , where the air thereafter circulates through and out of distribution channel  236  from a narrow gap  238  between distribution disk  236  and pickup surface  222  into depression  230 . Output port  228  may be a single opening in body portion  208  concentric with longitudinal axis  216 . However, body portion  208  may comprise a plurality of discrete outlet ports  228  such that distribution channel  236  may be provided with pressurized gas from a number of locations around the circumference of the distribution channel. In some embodiments, outlet port  228  would be a single annular port concentric with axis  216 . If a plurality of outlet ports are used, the outlet ports may, for example, be distributed equally about longitudinal axis  216 . For example, the plurality of outlet ports  228  may be configured at equal angular spacing about longitudinal axis  216 , such as, for example, every 30 degrees, and be equidistant from longitudinal axis  216 . However, it is not required that the angular spacing be equal, or that a plurality of gas outlet ports be equidistant from axis  216 . 
         [0049]    As the supplied gas flows through a small gap  240  between glass sheet  106  and pickup surface  222  of aero-mechanical device  204 , it flows faster, increasing the dynamic pressure ρU 2  where ρ is the gas density and U is the gas velocity. The increase in the dynamic pressure ρU 2  means that the static pressure P is reduced in accordance with the Bernoulli equation which states P+ρU 2 =0. It is this reduction in static pressure P which generates a negative pressure or vacuum by which aero-mechanical device  204  can hold glass sheet  106 . 
         [0050]    To ensure a substantially uniform flow of air from distribution channel  236  into depression  230 , it is desirable for cavity  210  to have a large volume. That is, cavity  210  should serve as an accumulator to prevent surging of the air flow into distribution channel  236 . In accordance with some embodiments, cavity  210  is cylindrical in shape with a longitudinal axis coincident with longitudinal axis  216  such that cavity  230  and body portion  208  share common longitudinal axis  216 . Moreover, longitudinal axis  216  is coincident with the center of distribution disk  232 , such that body portion  208  and disk  232  share common longitudinal axis  216 . Longitudinal axis  216  will hereinafter be interpreted to be the central axis for each of body portion  208 , cavity  210  and distribution disk  232 . The maximum diameter D of cavity  210  should be at least as large as the maximum diameter D′ of distribution disk  232 , and the diameter of cavity  210  is preferably larger than the diameter of distribution disk  232 . 
         [0051]    It has been found that the larger the diameter of distribution disk  232 , the greater the holding force that can be obtained. Preferably, the diameter D′ of distribution disk  232  is at least about 13 mm, more preferably at least about 15 mm. 
         [0052]    It has also been found that an increase in holding force can be obtained if the lower portion of body  208  has a rounded edge. That is, a circumferential edge  242  of body  208  is preferably rounded so that outer surface  218  flows or blends smoothly into pickup surface  222  with no sharp edges. For example, in one embodiment edge  242  includes a radius of curvature of about 0.3 cm. It is believed that rounded edge  242  stabilizes the flow of air between the surface of glass sheet  106  captured by the aero-mechanical device and pickup surface  222 , thereby helping to make the flow substantially uniform in velocity and pressure. This in turn increases the holding ability of the aero-mechanical device. Additionally, rounded edge  242  also helps prevent contact with the target object if the aero-mechanical device is tilted or skewed as it approaches the object. For example, if the aero-mechanical device is brought into the proximity of the glass sheet such that pickup surface  222  is generally non-parallel or tilted relative to the glass sheet (or vice versa), there is a danger that an edge of the aero-mechanical device may contact and damage the glass sheet. Rounded edge  242  minimizes the risk of contact between the aero-mechanical device and the target object. 
         [0053]    Modeling results have shown that by incorporating a rounded edge, the velocity of air exiting the interfacial region  240  between the pickup surface and glass sheet  106  is reduced when compared to an identical aero-mechanical device with an abrupt edge, that is, wherein the intersection between surface  218  and pickup surface  222  is substantially at 90 degrees. It has been found that when air exits interfacial gap  240  at high velocity, the air becomes turbulent near an abrupt edge, contributing to vibration of the glass sheet. Additionally, there is greater resistance to the flow of air exiting interfacial gap  240  when an abrupt edge is present, which leads to a reduction in the holding (e.g. lifting) force of aero-mechanical device  204 . 
         [0054]    Aero-mechanical devices  206  may be similar in construction to aero-mechanical devices  204 , but may further comprise standoffs  246  ( FIG. 4 ) disposed in or on pickup surface  222  such that glass sheet  106  is held a pre-determined distance from pickup surface  222 . Standoffs  246  also provide a lateral friction force against the sheet to prevent lateral movement of the sheet is the sheet is non-horizontal. For example, standoffs  246  may be rubber “feet” that are inserted into suitable holes in pickup surface  222  such that the feet extend a pre-determined distance from pickup surface  222 . A cross sectional view of an aero-mechanical device  206  is shown in  FIG. 4 . It is preferable that standoffs  246  comprise a resilient material that is softer than the glass sheet so that the surface of the glass sheet  106  is not damaged by contact with the standoffs. It is also desirable that the distance each of the standoffs extends above pickup surface  222  is such that the force exerted on glass sheet  106  by the air issuing from aero-mechanical device  204  does not exceed the force exerted on the glass sheet by the ambient atmosphere so that the glass sheet is forced against the standoffs and held securely. Alternatively, an edge clamp that contacts the non-quality edges of the glass sheet may be used to prevent lateral movement of the sheet. 
         [0055]    In another embodiment illustrated in  FIGS. 5A-5B , the at least one aero-mechanical device  304  may be substituted for aero-mechanical device  204 . Aero-mechanical device  304  comprises body portion  308  defining cavity  310  interior to the body and at least one inlet port  312  for receiving a supply of pressurized gas from a source (not shown). Body portion  308  preferably comprises a longitudinal axis  316  and a bottom or pickup surface  322 . Inlet port  312  is in fluid communication with cavity  310 , and may be equipped with any suitable conventional fitting  313  for connecting to the pressurized fluid supply line. Preferably, inlet port  312  is concentric with longitudinal axis  316  of the body portion. 
         [0056]    At least one outlet port  328  is also in fluid communication with cavity  310 . Preferably, the pressurized gas is clean, dry air, and is received into cavity  310  through inlet port  312 . That is, the pressurized gas should be filtered and free of moisture and/or oil. Since the pressurized gas continuously issues from aero-mechanical device  304  during use, air serves as an inexpensive, non-polluting working fluid. 
         [0057]    In accordance with the present embodiment, pickup surface  322  is preferably non-planar, and as illustrated in  FIG. 5A , comprises a central depression  330 . Aero-mechanical device  304  further comprises a distribution disk  332  centrally disposed within depression  330 . Distribution disk  332  is generally circular in shape with a central axis coincident with longitudinal axis  316 , and may be attached to body portion  308  by pressing a portion of the disk structure into an appropriate mating structure within the body portion. For example, distribution disk  332  may comprise a cylindrical pedestal on an upper surface thereof which is pressed into a suitably shaped depression in body portion  334 . The fit should be sufficiently tight to hold distribution disk  332  to body portion  308 . 
         [0058]    Distribution disk  332  further comprises a groove or distribution channel  336  for distributing pressurized air from cavity  210 , as best seen in  FIG. 5B . Preferably the distribution channel is disposed in an “upper” surface of the disk, adjacent body portion  308  in the assembled aero-mechanical device  304 . Thus, the at least one outlet port  328  connects cavity  310  with distribution channel  336 . Pressurized air from cavity  310  is fed by outlet port  328  into distribution channel  336 , where the air thereafter circulates through and out of distribution channel  336  from between distribution disk  332  and pickup surface  322  and into depression  330 . In some embodiments, output port  328  may be a single annular opening in body portion  308  concentric with longitudinal axis  316 . However, body portion  308  may comprise a plurality of discrete outlet ports  328  such that distribution channel  336  may be provided with pressurized air from a number of locations around the circumference of the distribution channel. The outlet ports may, for example, be distributed equally about longitudinal axis  316 . For example, the plurality of outlet ports  328  may be configured at equal angular spacing about longitudinal axis  316 . 
         [0059]    To ensure a substantially uniform flow of air from distribution channel  336  into depression  330 , it is desirable for cavity  310  to have a large volume. That is, cavity  310  should serve as an accumulator to prevent surging of the air flow into distribution channel  336 . In accordance with some embodiments, cavity  310  is cylindrical in shape with a longitudinal axis coincident with longitudinal axis  316  such that cavity  310  and body portion  308  share a common longitudinal axis. Moreover, longitudinal axis  316  is coincident with the center of distribution disk  332 , such that body portion  308  and disk  332  share a common longitudinal axis. Longitudinal axis  316  will hereinafter be interpreted to be the central axis for each of body portion  308 , cavity  310  and distribution disk  332 . The maximum diameter d of cavity  210  should be at least as large as the maximum diameter d′ of distribution disk  332 , and the diameter d of cavity  310  is preferably larger than the diameter d′ of distribution disk  332 . 
         [0060]    In accordance with the present embodiment, aero-mechanical device  304  may further comprise an annular-shaped porous material  338  disposed about a circumference of body portion  308 , and enclosure  340  disposed about a portion of porous material  338 . Porous material  338  may comprise any suitable material capable of providing a distributed outflow of air about a circumference of body portion  308 , but particularly through a bottom surface  339  of porous material  338 . For example, porous material  338  may comprise graphite, or be a porous sintered metal such as sintered bronze. Alternatively, porous material  338  may instead comprise an annular disk defining a plurality of outlets for air to exit through. The number of outlets may number in the hundreds to ensure an even distribution of air. 
         [0061]    Enclosure  340  includes at least one opening or port  342  into which a fitting  344  is attached for receiving a supply of pressurized air, and is adapted such that bottom surface or face  339  of porous material  338  remains exposed (i.e. uncovered by enclosure  340 ). Thus, pressurized air introduced into enclosure  340  through fitting  344  may escape through exposed face  339  of porous material  338 . In a preferred embodiment, enclosure  340  includes several inlet ports, as shown in  FIG. 5A , to ensure a more uniform air supply to the porous material. 
         [0062]    Pressurized air issuing from exposed face  339  of porous material  338  provides a force against glass sheet  106  to help ensure that glass sheet  106  is not contacted by edges of the porous material. This may occur, for example, if the aero-mechanical device is tilted with respect to the plane of the glass sheet. Additionally, an outside edge  346  of porous material  338  may be rounded in a manner similar to the previous embodiment to further ensure that an edge of the aero-mechanical device does not contact the glass sheet. As in the previous embodiment,  FIG. 5B  illustrates the circled detail in  FIG. 5A , and in particular the structure around disk  332 . 
         [0063]    It should be appreciated that there are other configurations that the aero-mechanical device can have besides the configuration shown in  FIGS. 3A ,  3 B and  5 A,  5 B (i.e. devices  204 ,  304 ). For example, the one or more aero-mechanical devices can be of the flat panel type comprising both pressure ports and vacuum ports, such as flat panel aero-mechanical devices sold by New Way® Air Bearings. Indeed, if flat panel aero-mechanical devices are used, they may be used to flatten glass sheet  106  in the region proximate the device. For example, the flat panel aero-mechanical device may be employed to hold and flatten glass sheet  106  proximate the score line to improve the quality of the score, and the subsequent separation of the glass sheet. Flattening of the glass sheet during the scoring and separating operation through the use of such panel-sized aero-mechanical devices can be effective to improve these processes as the size of glass sheets become larger. 
         [0064]    Accordingly,  FIG. 6A  illustrates a plurality of flat panel aero-mechanical devices  360  of the New Wave type. Such aero-mechanical devices typically include a substantially planar pickup surface comprising both pressure ports  362  for receiving a pressurized gas from a gas supply source as indicated by arrow  364 , and vacuum ports  366  to which a vacuum is applied by a vacuum source as indicated by arrow  368 . The vacuum ports exert a holding force, while the pressure ports expel a gas toward a surface of the glass sheet, thus exerting a repelling force. By balancing the holding and repelling forces, the glass sheet may be held at a predetermined position away from the surface of the aero-mechanical device. As depicted in  FIG. 6A , frame  202  includes a plurality of aero-mechanical devices  360  attached thereto, a support member  370  for supporting at least a portion of the weight of glass sheet  106 , and tabs  372  for constraining lateral movement of glass sheet  106  and for providing a guiding function during acquisition of the glass sheet by the at least one aero-mechanical device  360 . Advantageously, the plurality of aero-mechanical devices  360  may be supplied with different gas pressures and/or different amounts of vacuum to vary the fly-height of glass sheet  106 . For example, glass sheets drawn from a fusion downdraw device typically include thickened edge portions, therefore, it would be desirable to be able to adjust the fly height of the glass sheet to accommodate these thickened areas. 
         [0065]    Tabs  372  are preferably deformable or flexible (e.g. resilient), and may be formed, for example, from a natural or synthetic rubber. Alternatively, tabs  372  may be rigid but movable, such as being hinged and spring loaded. 
         [0066]    Support member  370  may, for example, comprise a grooved or channeled member  374  supported by a resilient or flexible member  376  attached to frame  202  as depicted by  FIG. 6B . Member  376  may, for example, comprise a spring. At least a portion of the weight of glass sheet  106  is then supported by physical contact with channel member  374 . Alternatively, support member  370  may comprise a porous material  378  supplied with a pressurized gas for supporting glass sheet  106  via an edge of glass sheet  106 , as illustrated in  FIG. 6C . Pressurized gas issuing from porous material  378  (depicted by arrows  380 ) levitates glass sheet  106 , providing contactless weight support for glass sheet  106 . 
         [0067]    Aero-mechanical devices  360  may be “full frame” in the sense that the aero-mechanical devices span substantially the full surface area of a side of glass sheet  106 , as shown in  FIG. 7A , or aero-mechanical devices  360  may be arranged in a partial frame such that they support and stiffen an outer area of the glass sheet while leaving a central portion of glass sheet  106  unsupported, as depicted in  FIG. 7B . The arrangement of  FIG. 7B  shows a plurality of aero-mechanical devices  360  positioned in a frame-like arrangement with a central portion  382  of the arrangement free of aero-mechanical devices. The frame-like arrangement can reduce the weight of the apparatus that must be supported by robot  104 . 
         [0068]    To assist enhanced robot  104 , and in particular aero-mechanical device  204  (and/or  206 ,  304  or  360 ), in handling glass sheet  106 , the gas exiting the aero-mechanical devices can be heated to match the temperature of glass sheet  106 , which cools as it is moved from TAM  150  to conveyor  160 , to avoid the creation of a temporary warp in glass sheet  106 . This is particularly true for glass sheets  106  of non-uniform thickness such as those with beads along the vertical edges as typically produced by fusion draw machine  140   a . Experiments have indicated that a significant amount of warp in glass sheet  106  can be thermally induced when the temperature of the gas exiting the aero-mechanical devices does not match the temperature of glass sheet  106 . To simplify further discussion, the following description will be presented in terms of aero-mechanical device  204  and/or  206 , with the understanding that the disclosed features may be used with the other aero-mechanical devices described herein. 
         [0069]    Temporary warp can dramatically reduce the effectiveness of aero-mechanical device  204 . Thermally induced warp in glass sheet  106  may also alter the interaction between the additional aero-mechanical devices  206  and glass sheet  106 . In addition, thermally induced warp in glass sheet  106  may create stress which could cause a crack to propagate within cut glass sheet  106 . This crack could originate from a flaw along one of the edges of sheet  106  or from any flaws within the body of glass sheet  106 . In addition, thermally induced stress due to temperature gradients within glass sheet  106  may cause a crack to propagate through cut glass sheet  106 . 
         [0070]    To address this concern, glass handling system  102  may include a temperature control system  402  ( FIG. 8 ) that can regulate the temperature of the gas emitted from aero-mechanical device  206  towards glass sheet  106  such that the temperature of the gas emitted from aero-mechanical device  206  substantially matches the current temperature of glass sheet  106 . Again, it should be noted that glass sheet  106  constantly cools as it is moved by enhanced robot  104  from TAM  150  to conveyor  160 . As such, temperature control system  402  needs to constantly reduce the temperature of the gas that is emitted from aero-mechanical device  204  to match the temperature of moving glass sheet  106 . A detailed discussion as to how temperature control system  402  can regulate the temperature of the gas emitted from aero-mechanical device  204  is provided below with respect to  FIG. 8 . 
         [0071]    Referring to  FIG. 8 , there is a block diagram illustrating the basic components of an embodiment of glass handling system  102  which includes enhanced robot  104  and temperature control system  402 . As shown, temperature control system  402  includes a temperature controller  404 , gas heater  406  and two temperature measuring devices  408  and  410 . The first temperature measuring device  408  measures a temperature of glass sheet  106 . And, the second temperature measuring device  410  measures a temperature of glass sheet  106  at a location substantially identical to the area impinged upon by gas emitted from aero-mechanical device  204 . Alternatively, the second temperature measuring device  410  can measure a temperature of the gas emitted from aero-mechanical device  204 . Temperature controller  404  receives the measured temperatures from both of temperature measuring devices  408  and  410  and then controls a set-point on gas heater  406  to heat the gas received from gas supply unit  412  such that the temperature of the gas emitted from aero-mechanical device  204  is the same as or a little more or a little less than the current temperature of glass sheet  106 , e.g. substantially matches. In practice, the temperature of the gas emitted from aero-mechanical device  204  may be somewhat less than the current temperature of glass sheet  106  so as to equal the cooling provided by natural convection to the remainder of glass sheet  106 . Another purpose of temperature control system  402  can be to help constrain the motion of glass sheet  106  during the acquisition period with enhanced robot  104 . 
         [0072]    In one embodiment, first and second temperature measuring devices  408  and  410  are located on the same side of glass sheet  106  as the one or more aero-mechanical devices  204 . First temperature measuring device  408  should not contact glass sheet  106  and should be located in an area not affected by the gas emitted from aero-mechanical device  204 . And, the second temperature measuring device  410  should not contact glass sheet  106  and should be located in an area that is affected by the gas emitted from aero-mechanical device  204 . Of course, the temperature measurement of the thermal impact of aero-mechanical device  204  (gas temperature exiting air device or glass temperature) should be precise. Assuming, the gas exit temperature is used as the feedback metric, it will need to be “calibrated” to the temperature of the glass sheet  106  to properly program the temperature controller  104 . 
         [0073]    Gas heater  406  may be selected to be capable of altering the gas temperature exiting aero-mechanical device  204  to nearly instantaneously match the current temperature of glass sheet  106 . This means that gas heater  406  should have a low thermal inertia and relatively low response time as the temperature of the glass sheet  106  can drop very fast. Of course, gas heater  406  should not generate or transport particulates or other contaminants to the surface of glass sheet  106 . 
         [0074]    A central computer  414  (optional) is also shown in  FIG. 8  that can be used to help control temperature controller  404  and can also be used to help control the operation of an optional three-way valve  416 . Three-way valve  416  can be controlled to permit the gas emitted from gas heater  406  to enter or bypass aero-mechanical device  204 . Three-way valve  416  would be configured to bypass or prevent the gas from entering aero-mechanical device  204  when glass sheets  106  are not being produced so as to reduce the effect upon the environment near TAM  150 . Three-way valve  416  can also be configured to bypass or prevent the gas from entering aero-mechanical device  204  when device  204  approaches drawn glass sheet  105  below TAM  150  as well as when device  204  releases cut glass sheet  106  to the conveyor. Alternatively, three-way valve  416  can be manually operated. 
         [0075]    Referring to  FIG. 9  there is a block diagram illustrating the basic components of another embodiment of glass handling system  102  that includes a flow control system  502  in addition to enhanced robot  104  and temperature control system  402 . As shown, flow control system  502  includes a flow controller  504  and a flow sensor  506  that function together to control the flow rate of the gas emitted from aero-mechanical device  204 , and optionally  206 . Flow control system  502  is helpful in several ways. First, it can be utilized when enhanced robot  104  acquires glass sheet  106  and when it disengages from glass sheet  106 . During the acquisition process, flow controller  504  can gradually increase the flow of gas to aero-mechanical devices  204 ,  206  to move glass sheet  106  smoothly toward aero-mechanical devices  204 ,  206 . During disengagement, flow controller  504  can gradually decrease the flow of gas to aero-mechanical devices  204 ,  206  to move glass sheet  106  smoothly away from the aero-mechanical devices. This type of flow control may be preferable since if one merely cycles the gas to aero-mechanical devices  204 ,  206  on and off, then glass sheet  106  could move rapidly towards the aeromechanical devices  204 ,  206  and produce contact damage and/or excess vibration. Secondly, control of the gas flow could also be used to fine tune the position of glass sheet  106  relative to aero-mechanical devices  204 ,  206 . Central computer  414  can be used to control the operation of flow controller  504 . 
         [0076]    Referring to  FIG. 10 , there is a block diagram illustrating the basic components of a third embodiment of the glass handling system  102  that includes a position control system  602  in addition to enhanced robot  104 , temperature control system  402  and flow control system  502 . As shown, position control system  602  includes a position controller  604  and a position sensor  606  that function together to control the flow rate and/or temperature of the gas emitted from aero-mechanical devices  204 ,  206  so as to control the position of glass sheet  106  relative to aero-mechanical devices  204 ,  206 , or the position of the aero-mechanical devices to glass sheet  106  according to pre-determined instructions. In operation, position control sensor  604  receives a signal from position sensor  606  that indicates the position of glass sheet  106  and then sends one or more control signals to flow controller  502  and/or temperature controller  402  to control and change the position of glass sheet  106  relative to aero-mechanical devices  204 ,  206  or the position of the aero-mechanical devices, via robot  104 , to glass sheet  106  according to pre-determined instructions. In this way, position controller  604  can control the magnitude of the gap between glass sheet  106  and aero-mechanical devices  204 ,  206 . Central computer  414  can be used to control the operation of position controller  604 . 
         [0077]    This method of controlling the position of glass sheet  106  can be used to improve the ability of robot  104  to acquire and move glass sheet  106 . In particular, sheet position controller  604  can be used to control the force produced by aero-mechanical devices  204  and/or,  206  to hold glass sheet  106  in a fixed position with respect to face  222  of aero-mechanical device  204  and/or  206  while taking into account changes in the load in a direction normal to moving glass sheet  106 . This load includes the gravitational force that is applied when enhanced robot  104  moves and tilts glass sheet  106  through a variety of angles. This load also includes the aerodynamic drag that is created when enhanced robot  104  moves and tilts glass sheet  106  through ambient air at varying speeds. 
         [0078]    The basic steps of a preferred method for engaging and moving glass sheet  106  in accordance with embodiments of the present invention begin with enhanced robot  104  engaging and moving glass sheet  106  using at least one aero-mechanical device  204  (or  304  or  360 ) that supports and holds the glass sheet  106  without contacting the glass sheet  106 . 
         [0079]    Temperature control system  402  can be used to regulate a temperature of the gas emitted from aero-mechanical device  204  towards glass sheet  106  such that the temperature of the gas emitted from aero-mechanical device  204  substantially matches a temperature of glass sheet  106 . A detailed discussion about exemplary temperature control system  402  was described above with respect to  FIG. 8 . 
         [0080]    Flow control system  502  can be used to control the flow rate of the gas emitted from aero-mechanical device  204  so aero-mechanical device  204  can effectively acquire glass sheet  106  and disengage from glass sheet  106 . A detailed discussion about exemplary flow control system  502  was described above with respect to  FIG. 9 . 
         [0081]    Position control system  602  can be used to control a flow rate and/or temperature of the gas emitted from aero-mechanical device  204  so as to control a position of glass sheet  106  relative to aero-mechanical device  204  (e.g. robot  104 ), or alternatively, to control the position of aero-mechanical device  204  (e.g. robot  104 ) relative to a position of glass sheer  106 . A detailed discussion about position control system  602  was described above with respect to  FIG. 10 . For example, position control system  602  and flow control system  502  may work together so that the gas pressure delivered to aero-mechanical device  204  is ramped up (or down) as aero-mechanical device  204  moves toward (or away from) glass sheet  106 . Thus, aero-mechanical device  204  can smoothly acquire (or disengage) with glass sheet  106  and minimize vibration of the sheet. Minimizing vibration is a very desirable attribute of a conveyance system that is used during glass sheet separation at the bottom of the draw area. Vibration of the sheet during engagement of the robot  104  (and aero-mechanical device  204 ) and prior to separation of the sheet can propagate upward into the viscous region of the glass and negatively impact the shape of the sheet. Consequently, minimal vibration is a valuable advantage. In one embodiment, robot  104  positions aero-mechanical device  204  in a range from about 1 mm to about 5 mm from the surface of glass sheet  106 . Robot  104  then moves aero-mechanical device  204  toward glass sheet  204  while flow control system  502  and position control system  602  coordinate, such as through central computer  414 , to increase the gas pressure supplied to aero-mechanical device  204  until the supplied pressure is appropriate for the desired working distance (fly height), as determined by position control system  602 . 
       EXAMPLE 1 
       [0082]    In one experiment, illustrated in  FIG. 11 , aero-mechanical device  204  was brought into position by robot  104  at a distance in excess of 5 mm from the surface of glass sheet  106 . The pressure to aero-mechanical device  204  was increased to the desired working pressure, and aero-mechanical device  204  then brought to the appropriate fly height above the surface of glass sheet  106 . That is, the aero-mechanical device had reached an appropriate working pressure prior to arriving at the desired fly height. Curve  700  depicts a plot of displacement (vibration) as a function of time for this instance. The experiment was repeated, except that the pressure supplied to aero-mechanical device  204  was first brought to within about 3 mm of the surface of the glass sheet before beginning a ramp (increase) of the pressure to the desired working pressure. A similar plot of displacement vs. time is depicted by curve  702 . Curve  702  illustrates a marked reduction in vibration. 
         [0083]    From the foregoing, it can be readily appreciated by those skilled in the art that glass handling system  102  that utlizes enhanced robot  104  and aero-mechanical devices  204  and aero-mechanical devices  206  to acquire and move glass sheet  106  is a marked improvement over the traditional robot that simply used suction cups to acquire and move glass sheet  106 . This improvement is possible because enhanced robot  104  is able to acquire and hold the center portion of glass sheet  106  as well as the outer edges of glass sheet  106 , whereas the traditional robot can only acquire and hold the outer edges of glass sheet  106 . 
       EXAMPLE 2 
       [0084]    FLUENT software was used to model the velocity of air exiting between a pickup surface of a conventional aero-mechanical device using the Bernoulli principal and a modified aero-mechanical device to better understand the potential for velocity-induced turbulence that could lead to vibration of the glass sheet. The experiment can be better understood with the help of  FIG. 12 . The conventional aero-mechanical device  800  was a Rexroth NCT60 device. The modified device  802  was the same device, but with a rounded lower edge (pickup surface edge)  804  with a radius of curvature of approximately ⅛ inch (0.3175 cm). Both devices were assumed to be supplied with air at an inlet pressure of 6 bar. The velocity of the air exiting the gap  806  at reference surface  808  of each device is plotted in  FIGS. 13 and 14 , respectively, as a function of velocity in meters/second vs. distance Z from the surface  810  of glass sheet  106  (movement in a negative direction on the x-axis is in a direction away from the sheet). Curves  812 ,  814 ,  816  and  818  in  FIG. 13  represent velocity as a function of distance from glass surface  810  at four radial distances S from surface  808  of the conventional aero-mechanical device  800 : 10 cm, 20 cm, 30 cm and 35 cm, respectively. Curves  820 ,  822 ,  824  and  826  in  FIG. 14  represent velocity as a function of distance from glass surface  810  at four radial distances S from surface  808  of the modified aero-mechanical device  802  at 10 cm, 20 cm, 30 cm and 35 cm, respectively. As shown, the velocity curves  820 ,  822 ,  824  and  826  for the modified device show a reduced velocity for all four positions (from surface  808 ) when compared to the conventional device, indicating a potential for reduced turbulence and subsequently reduced vibration of the glass, and less interaction between spaced apart devices used against the same glass sheet (and thus the ability to use multiple modified devices with reduced spacing when compared to conventional devices). 
       EXAMPLE 3 
       [0085]    Using FLUENT software, pressure against glass surface  810  was modeled for the conventional and modified devices  800  and  802 , respectively, of the above Example 2, and again referring to  FIG. 12 . The data is plotted in  FIG. 15  is pressure in Pascal as a function of radial distance (in meters) from the center of the devices, where a zero value on the x-axis represents the center axis C of the devices. Gap  806  was assumed to be 0.0005 m. Curve  828  depicts pressure as a function of radial distance for the conventional device  800 , whereas curve  830  depicts pressure as a function of radial distance for the modified device  802 . Surface  808  corresponds to a position of 0.03 m on the x-axis. As can be seem from the data, the conventional device experiences a significant positive pressure “bump” at a radial position of about 0.024 m, whereas the modified device  802  shows only a very small positive pressure at the same position, thus leading to the conclusion that the modified device (and a rounded edge), can provide greater holding force. 
         [0086]    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. For example, although much of the above description involved handling the glass sheet at the bottom of the draw area, embodiments of the present invention may be used at other times that large thin glass sheets must be handled. 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. 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.