Abstract:
Methods and apparatus for grasping and moving workpieces are disclosed. A device in accordance an exemplary embodiment of the present invention comprises a disk including an outer edge. The disk has a generally planar resting shape in which the disk has a first diameter and a first edge length. A means for holding the disk in a folded shape in which the disk defines a cavity is also provided. In a preferred embodiment, the disk is in an unstretched state while the disk is assuming the folded shape so that the disk may assume the resting shape by unfolding without unstretching. Also in a preferred embodiment, the disk has a second diameter and a second edge length while the disk is assuming the folded shape, where the second diameter is smaller than the first diameter and the second edge length is substantially equal to the first edge length.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to methods and apparatus for grasping and moving workpieces. More particularly, the present invention relates to methods and apparatus for grasping and/or moving workpieces which are sensitive to contamination and/or fragile.  
         BACKGROUND OF THE INVENTION  
         [0002]    Today, many products are produced inexpensively and in high volume using highly mechanized and/or automated manufacturing techniques. Examples of workpieces which are sometimes handled using mechanized and/or automated equipment include transparent glass panes, glass mirrors, and semiconductors (e.g., wafers, chips, and dies). When practicing such manufacturing techniques, it is often necessary for a machine to grasp and move a workpiece. This may be accomplished using some sort of gripper.  
           [0003]    In some cases, the material of the gripper may leave residue on the workpiece. Additionally, relative movement between the gripper and the workpeice (e.g., rubbing) may cause damage to the workpiece in some cases. Thus, it is desirable to efficiently grasp and transfer workpieces while at the same time minimizing contamination of the workpiece and damage to the workpiece.  
         SUMMARY OF THE INVENTION  
         [0004]    The present invention relates generally to methods and apparatus for grasping and moving workpieces. More particularly, the present invention relates to methods and apparatus for grasping and/or moving workpieces which are sensitive to contamination and/or fragile. An assembly in accordance with an exemplary implementation of the present invention includes a disk and a cup shaped member having a mid portion fixed to a central portion of the disk. A skirt of the cup shaped member may be advantageously dimensioned to urge an outer portion of the disk out of plane with a central portion of the disk so that the disk defines a cavity when the skirt is disposed in a resting shape. The skirt may also advantageously have a level a resilience selected to allow the skirt to assume a stretched shape while the disk is assuming a generally planar condition.  
           [0005]    In one aspect of the present invention, the disk is interposed between the cup shaped member and a workpiece. Accordingly, in some implementations, the disk advantageously prevents the cup shaped member from contacting the workpiece. Additionally, the disk may advantageously prevent the skirt of the cup shaped member from rubbing on the workpiece, for example, when skirt stretches to assume a stretched shape.  
           [0006]    A method of moving a workpiece in accordance with an exemplary implementation of the present invention comprises the steps of providing a disk having a generally planar condition and urging an outer portion of the disk out of plane with a central portion of the disk so that the disk defines a cavity. A source of relatively low pressure is placed in fluid communication with the cavity defined by the disk and the disk is positioned against a workpiece. The workpiece may be moved, for example, by moving the disk while the disk is positioned against the workpiece.  
           [0007]    In some advantageous implementations of the present invention, the disk is adapted to move between a planar condition and a folded condition by folding and unfolding without significant stretching and unstretching. More particularly, the length of an edge of the disk preferably remains substantially unchanged as the disk moves between a planar condition and a folded condition. A disk which moves between a planar condition and a folded condition by folding and unfolding without significant stretching and unstretching may conform to the face of a generally planar workpiece with minimal rubbing between the disk and the workpiece.  
           [0008]    In some advantageous implementations of the present invention, the skirt of the cup shaped member comprises an elastomeric material and the disk comprises a non-elastomeric material. When this is the case, the elastomeric material forming the skirt may allow the skirt to assume a stretched shape. Also in these advantageous implementations, the nonelastomeric material forming the disk may allow the disk to move between a planar condition and a folded condition by folding and unfolding without significant stretching and unstretching of the material forming disk.  
           [0009]    A disk assembly in accordance with an exemplary implementation of the present invention may include a disk having a first surface and an annular ring of adhesive disposed on the first surface of the disk. An inner extent of the adhesive and an inner perimeter of the disk define a first adhesive free portion of the disk. In some advantageous implementations of the present invention, this first adhesive free portion is dimensioned to prevent the adhesive from extruding beyond the inner perimeter of the disk. In certain advantageous implementations, an outer extent of the adhesive and an outer perimeter of the disk define a second adhesive free portion of the disk. In certain particularly advantageous implementations of the present invention, this second adhesive free portion is dimensioned to prevent the adhesive from extruding beyond the outer perimeter of the disk. 
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is an exploded perspective view of an assembly in accordance with an exemplary embodiment of the present invention.  
         [0011]    [0011]FIG. 2 is a cross sectional perspective view of an assembly in accordance with an exemplary embodiment of the present invention.  
         [0012]    [0012]FIG. 3 is a cross sectional perspective view of a disk in accordance with an exemplary embodiment of the present invention.  
         [0013]    [0013]FIG. 4 is an additional cross sectional perspective view of disk shown in the previous figure.  
         [0014]    [0014]FIG. 5 is a cross sectional view of an assembly in accordance with an exemplary embodiment of the present invention.  
         [0015]    [0015]FIG. 6 is a cross sectional view of an assembly including cup shaped member and disk shown in the previous figure.  
         [0016]    [0016]FIG. 7 is a perspective view of a disk in accordance with an exemplary embodiment of the present invention.  
         [0017]    [0017]FIG. 8 is a cross sectional view of an assembly in accordance with an additional exemplary embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0018]    The following detailed description should be read with reference to the drawings, in which like elements in different drawings are numbered identically. The drawings, which are not necessarily to scale, depict selected embodiments and are not intended to limit the scope of the invention. Examples of constructions, materials, dimensions, and manufacturing processes are provided for selected elements. All other elements employ that which is known to those of skill in the field of the invention. Those skilled in the art will recognize that many of the examples provided have suitable alternatives that can be utilized.  
         [0019]    [0019]FIG. 1 is an exploded perspective view of an assembly in accordance with an exemplary embodiment of the present invention. The assembly of FIG. 1 includes a generally cup shaped member  102  and a disk  104 . In FIG. 1, disk  104  is shown having a generally planar shape. An adhesive  106  is disposed on an adhesive covered portion  108  of a first surface  120  of disk  104 . In some embodiments of the present invention, adhesive  106  is dimensioned for fixing a central portion  122  of disk  104  to a mid portion  124  of cup shaped member  102 . In the embodiment of FIG. 1, cup shaped member  102  includes a skirt  126  disposed about mid portion  124 . In some embodiments of the present invention, skirt  126  is dimensioned to urge disk  104  to assume a folded shape when central portion  122  of disk  104  is fixed to mid portion  124 .  
         [0020]    [0020]FIG. 2 is a cross sectional perspective view of an assembly in accordance with an exemplary embodiment of the present invention. The assembly of FIG. 2 includes a generally cup shaped member  202  and a disk  204 . In the embodiment of FIG. 2, a central portion  222  of disk  204  is fixed to a mid portion  224  of cup shaped member  202  by an adhesive  206 . In the embodiment of FIG. 2, an outer portion  228  of disk  204  is disposed in an out of plane relationship with central portion  222  of disk  204 .  
         [0021]    In the embodiment of FIG. 2 it may be appreciated that disk  204  defines a cavity  230 . A hub  232  of cup shaped member  202  defines a lumen  234  which communicates with cavity  230  via a hole  236  defined by disk  204 . In the embodiment of FIG. 2, a thread  238  is disposed within lumen  234 . Lumen  234  and thread  238  may be adapted to receive a suitable fitting so that a source of relatively low pressure (e.g., vacuum) can be selectively connected to cavity  230 .  
         [0022]    [0022]FIG. 3 is a cross sectional perspective view of a disk  304  in accordance with an exemplary embodiment of the present invention. In the embodiment of FIG. 3, disk  304  is disposed in a generally planar condition in which disk  304  has a first diameter D1. Disk  304  includes an edge  340  having a length. In the embodiment of FIG. 3, the length of edge  340  is preferably substantially equal to the circumference of disk  304 .  
         [0023]    [0023]FIG. 4 is an additional cross sectional perspective view of disk  304  shown in the previous figure. In the embodiment of FIG. 4, disk  304  is disposed in a folded condition in which disk  304  defines a cavity  330 . A second diameter D2 of disk  304  is illustrated in FIG. 4.  
         [0024]    In some embodiments of the present invention, disk  304  is adapted to move between a planar condition and a folded condition by folding and unfolding without significant stretching and unstretching. In some of these embodiments, the length of edge  340  of disk  304  preferably remains substantially unchanged as disk  304  moves between a planar condition and a folded condition. In certain embodiments of the present invention, disk  304  comprises a non-elastomeric material. A disk  304  which moves between a planar condition and a folded condition by folding and unfolding without significant stretching and unstretching may conform to the face of a generally planar workpiece with minimal rubbing between the disk and the workpiece.  
         [0025]    In FIG. 4 it may be appreciated that a plurality of undulations  342  are formed along a periphery  344  of disk  304  while disk  304  is in the illustrated folded condition. In the embodiment of FIG. 4, undulations  342  include a plurality of valleys  346  which define a first cone  348 . Also in the embodiment of FIG. 4, undulations  342  include a plurality of peaks  350  which define a second cone. In the embodiment of FIG. 4, the first cone defined by valleys  346  and the second cone defined by peaks  350  are generally coaxial with one another.  
         [0026]    [0026]FIG. 5 is a cross sectional view of an assembly in accordance with an exemplary embodiment of the present invention. The assembly of FIG. 5 includes a generally cup shaped member  502  and a disk  504 . In the embodiment of FIG. 5, a central portion  522  of disk  504  is fixed to a mid portion  524  of cup shaped member  502  by an adhesive  506 . In the embodiment of FIG. 5, central portion  522  of disk  504  defines a plane  552 , and an outer portion  528  of disk  504  is disposed out of plane relative to central portion  522  of disk  504 .  
         [0027]    In the embodiment of FIG. 5 it may be appreciated that disk  504  defines a cavity  530 . A hub  532  of cup shaped member  502  defines a lumen  534  which communicates with cavity  530  via a hole  536  defined by disk  504 . In the embodiment of FIG. 5, a thread  538  is disposed within lumen  534 . Lumen  534  and thread  538  may be adapted to receive a suitable fitting so that a source of relatively low pressure (e.g., vacuum) can be selectively connected to cavity  530 .  
         [0028]    One method of moving a workpiece in accordance with an exemplary embodiment of the present invention comprises the steps of providing a disk having a generally planar shape and urging an outer portion of the disk out of plane with a central portion of the disk so that the disk defines a cavity. A source of relatively low pressure is placed in fluid communication with the cavity defined by the disk and the disk is positioned against a workpiece. The workpiece may be moved, for example, by moving the disk while the disk is positioned against the workpiece.  
         [0029]    In some advantageous methods in accordance of the present invention, disk  504  changes between a planar shape and a folded shape by folding and unfolding without significant stretching and unstretching of the material forming disk  504 . In these advantageous methods, disk  504  may be unfolded onto the surface of a workpiece and rubbing contact between disk  504  and the workpiece may be minimized.  
         [0030]    [0030]FIG. 6 is a cross sectional view of an assembly including cup shaped member  502  and disk  504  shown in the previous figure. In the embodiment of FIG. 6, disk  504  is shown overlaying a generally planar surface  554  of a workpiece  500 . In FIG. 6, it may be appreciated that disk  504  has assumed a generally planar shape. In FIG. 6 it may also be appreciated that skirt  526  of cup shaped member  502  has assumed a stretched shape. In some embodiments of the present invention, skirt  526  has a level a resilience which allows skirt  526  to selectively assume a stretched shape while disk  504  is disposed in a generally planar condition.  
         [0031]    In some embodiments of the present invention, skirt  526  of cup shaped member  502  comprises an elastomeric material and disk  504  comprises a non-elastomeric material. When this is the case, the elastomeric material forming skirt  526  may allow skirt  526  to assume a stretched shape. Additionally, the non-elastomeric material forming disk  504  may allow disk  504  to move between a planar condition and a folded condition by folding and unfolding without significant stretching and unstretching of the material forming disk  504 . The term elastomeric generally refers to a rubber like material (e.g., a material which can experience about a 5% stretch and return to the undeformed configuration). Examples of elastomeric materials include rubber (e.g., natural rubber, silicone rubber, nitrile rubber, polysulfide rubber, etc.), thermoplastic elastomer (TPE), butyl, polyurethane, and neoprene. Vacuum cups which may be suitable for use with the present invention are commercially available from Vi-Cas Manufacturing Company of Cincinnati, Ohio, USA. These vacuum cups are available in a material which the company identifies as vinyl.  
         [0032]    It will be appreciated that disk  504  may comprise various materials without deviating from the spirit and scope of the present invention. Examples of materials which may be suitable in some applications include: polyethylene (e.g., low density polyethylene), polypropylene (PP), polytetrafluoroethylene (PTFE), polyester (e.g., PET), polyamide, and polyimide.  
         [0033]    In FIG. 6 disk  504  is shown interposed between cup shaped member  502  and workpiece  500 . Accordingly, it may be appreciated that disk  504  prevents cup shaped member  502  from contacting workpiece  500  in the embodiment of FIG. 6. In some embodiments of the present invention, as mentioned above, skirt  526  of cup shaped member  502  comprises an elastomeric material and disk  504  comprises a non-elastomeric material. Elastomeric materials are useful in these embodiments, because they provide cup shaped member  502  with the ability to assume a stretched shape. In some applications, however, elastomeric materials may leave residue on the workpiece when they are allowed to contact the workpiece (e.g., glass window panes and semiconductors). The residue left by the elastomeric material may comprise, for example, fine particles of elastomeric material which have been pressed into micro fissures in the workpiece and/or plastisizers which have leached out of the elastomeric material. When handling cosmetically critical workpieces (e.g., glass window panes and glass mirrors) any residue left on the workpiece will be particularly noticeable. Even when the residue is not noticeable under ordinary conditions, it may become readily apparent in other conditions. For example, when a bathroom mirror fogs up while a person takes a shower the droplets of water condensing on the glass can be seen to selectively condense on the areas of the mirror that do not contain any residue.  
         [0034]    In the embodiment of FIG. 6 disk  504  is interposed between skirt  526  of cup shaped member  502  and workpiece  500 . When this is the case, disk  504  will preferably prevent skirt  526  from rubbing on workpiece  500 , for example, when skirt stretches to assume a stretched shape. When handling semiconductors (e.g., wafers, chips, and dies) relative movement between the workpiece and another object may cause damage to active areas of the semiconductor. Examples of such active areas may include bonding pads, transistors, conductive paths, etc.  
         [0035]    [0035]FIG. 7 is a perspective view of a disk  704  in accordance with an exemplary embodiment of the present invention. In the embodiment of FIG. 7, disk  704  is disposed in a generally planar shape. An adhesive  706  is disposed on an adhesive covered portion  708  of a first surface  720  of disk  704 . An inner extent  758  of adhesive  706  and an inner perimeter  760  of disk  704  define a first adhesive free portion  762  of disk  704 . In some advantageous embodiments of the present invention, first adhesive free portion  762  of disk  704  is dimensioned to prevent adhesive  706  from extruding beyond inner perimeter  760  of disk  704 . An outer extent  764  of adhesive  706  and an outer perimeter  766  of disk  704  define a second adhesive free portion  782  of disk  704 . In some advantageous embodiments of the present invention, second adhesive free portion  782  of disk  704  is dimensioned to prevent adhesive  706  from extruding beyond outer perimeter  766  of disk  704 .  
         [0036]    [0036]FIG. 8 is a cross sectional view of an assembly in accordance with an additional exemplary embodiment of the present invention. The assembly of FIG. 8 includes a disk  904  having a central portion that is fixed to a body  968  by an adhesive  906 . In the embodiment of FIG. 8, disk  904  is shown overlaying a generally planar surface  954  of a workpiece  900 . In FIG. 8, it may be appreciated that disk  904  has assumed a generally planar shape.  
         [0037]    In FIG. 8, a collar  970  is shown disposed about body  968 . In a preferred embodiment of the present invention, collar  970  is biased to press against workpiece  900 . Various mechanisms may be used to urge collar  970  towards workpiece  900  including, for example, pneumatic mechanisms (e.g., piston and cylinder arrangements), spring mechanisms, and electrical mechanisms (e.g., solenoids). In the embodiment of FIG. 974 a resilient ring  976  is disposed between collar  970  and a shoulder  978  of body  968 . Resilient ring  976  may comprise various elements without deviating from the spirit and scope of the present invention. Examples of elements which may be suitable in some applications include an elastomeric annulus and a wave spring.  
         [0038]    [0038]FIG. 9 is a cross sectional view of an assembly including body  968  and disk  904  shown in the previous figure. In the embodiment of FIG. 9, a central portion  922  of disk  904  defines a plane  952 , and an outer portion  928  of disk  904  is disposed out of plane relative to central portion  922  of disk  904  so that disk  904  defines a cavity  930 .  
         [0039]    Several forms of invention have been shown and described, and other forms will now be apparent to those skilled in art. It will be understood, however, that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement of parts without exceeding the scope of the invention. The invention&#39;s scope is, of course, defined in the language in which the appended claims are expressed.