PATENT ABSTRACT
Pneumatic edge-clamp systems and methods are disclosed. In one embodiment, a clamping apparatus for applying a clamping force to a workpiece includes a beam member having a cavity disposed therein, and an inflatable member disposed within the cavity. The inflatable member is coupleable to a pressurization source. A clamping member is pivotably coupled to the beam member. The clamping member includes a first portion projecting at least partially over the cavity, and a second portion projecting laterally outwardly from the beam member over the workpiece. In operation, inflating the inflatable member applies a driving force to the first portion, rotating the clamping member, and applying a clamping force to the workpiece using the second portion.

PATENT DESCRIPTION
FIELD OF THE INVENTION  
       [0001]     This invention relates to systems and methods for securing a workpiece during a manufacturing operation, and more specifically, to pneumatic edge-clamp systems and methods that may be used, for example, in welding or other manufacturing operations.  
       BACKGROUND OF THE INVENTION  
       [0002]     During many different types of manufacturing operations, it is necessary to secure the workpiece in position. For example, in the process of friction stir welding, a sheet aluminum panel is clamped against an aluminum substructure, such as an I-beam, to allow a high speed rotating spindle to engage the panel, causing friction-induced elevated temperatures which fuse the panel and substructure together.  
         [0003]     One proven method of clamping the aluminum panel is to use commercially available pneumatic inflatable bladders which expand against the panel to restrain movement of the panel and press it firmly against the substructure. Such inflatable flexible bladders are typically contained in a low profile metal frame that is machined with an offset contour that matches the panel. The offset contour places the inflatable bladder slightly offset above the panel, allowing the flexible bladder to expand against and conform to the surface contour of the panel. A set of these metal frames can be placed nearby both sides of the friction stir welded joint to provide secure clamping on each side of the rotating spindle.  
         [0004]     A problem may arise when the friction stir welded joint is located near the edge of the panel since there is no space on the outside edge of the joint for the typical metal frames which house the pneumatic inflatable bladders. Since it is desirable to have clamping force applied on both sides of the joint during the welding process, there is a need for an improved edge-clamping system that provides the desired clamping force on both sides of the joint during the welding process even near the edges of the panel.  
       SUMMARY OF THE INVENTION  
       [0005]     The present invention provides pneumatic edge-clamp systems and methods for securing a workpiece during a manufacturing operation. Embodiments of the present invention may advantageously provide a low-profile edge-clamping system that operates with a short displacement, conforms to the surface contour of the panel, provides quick actuation, and that is readily reconfigurable as needed.  
         [0006]     In one embodiment, a clamping apparatus for applying a clamping force to a workpiece includes a beam member having a cavity disposed therein, and an inflatable member disposed within the cavity. The inflatable member is coupleable to a pressurization source. A clamping member is pivotably coupled to the beam member. The clamping member includes a first portion projecting at least partially over the cavity, and a second portion projecting laterally outwardly from the beam member over the workpiece. In operation, inflating the inflatable member applies a driving force to the first portion, rotating the clamping member, and applying a clamping force to the workpiece using the second portion. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]     Embodiments of the present invention are described in detail below with reference to the following drawings.  
         [0008]      FIG. 1  illustrates a perspective view of components of a welding system formed in accordance with an embodiment of the present invention;  
         [0009]      FIG. 2  illustrates a cross-sectional view of a portion of the welding system shown in  FIG. 1 ;  
         [0010]      FIG. 3  illustrates an exploded view of an edge-clamp frame and seal formed in accordance with an embodiment of the present invention;  
         [0011]      FIG. 4  illustrates a perspective view of an edge-clamping component in accordance with an embodiment of the present invention;  
         [0012]      FIG. 5  is an enlarged, partially exploded isometric view of a portion of the edge-clamping component of  FIG. 4 ;  
         [0013]      FIG. 6  is an enlarged, partially exploded isometric view of another portion of the edge-clamping component of  FIG. 4 ; and  
         [0014]      FIGS. 7 and 8  illustrate cross-sectional views of the clamping component of  FIG. 4  in non-clamping and clamping modes, respectively.  
     
    
     DETAILED DESCRIPTION  
       [0015]     The present invention relates to pneumatic edge-clamp systems and methods for securing a workpiece during a manufacturing operation. Many specific details of certain embodiments of the invention are set forth in the following description and in  FIGS. 1 through 8  to provide a thorough understanding of such embodiments. One skilled in the art, however, will understand that the present invention may have additional embodiments, or that the present invention may be practiced without several of the details described in the following description.  
         [0016]      FIG. 1  illustrates a manufacturing system  18  in accordance with an embodiment of the present invention. In this embodiment, the manufacturing system  18  includes a controller  20 , a pneumatic pump  19 , and a clamping device  21 . The controller  20  controls operation of the pneumatic pump  19  for supplying pressurized air to various components of the clamping device  21 . The controller  20  may also control other components of the manufacturing system  18 , including one or more tools  30  that perform manufacturing operations on one or more workpieces secured by the clamping device  21 . In one embodiment, the tools  30  are welding components, such as friction stir welding heads or the like.  
         [0017]     In one embodiment, the clamping device  21  includes one or more edge-clamp systems  26  and one or more pneumatic surface clamps  32  for securely positioning a first workpiece  24  with respect to a second workpiece  22  during the performance of the manufacturing operation (e.g. welding). The pneumatic surface clamps  32  and the edge-clamps systems  26  are attached to one or more fixture bases  28 . As described more fully below, in one embodiment, the tools  30  may perform welding (e.g. friction stir welding) along pre-defined paths to securely bond the first and second workpieces  24 ,  22  together. In alternate embodiments, any other desired manufacturing operations may be performed.  
         [0018]      FIG. 2  illustrates a cross-sectional view of a portion of the manufacturing system  18  of  FIG. 1 . As shown in  FIG. 2 , in this embodiment, the pneumatic surface clamp  32  includes an inflatable seal  52  that, when inflated by the pump  19 , applies pressure on the first workpiece  24 , securely engaging the first workpiece  24  against the second workpiece  22 . In one embodiment, the first workpiece  24  is a molded aluminum skin, such as that of a fuselage of an aircraft, and the second workpiece  22  is an aluminum stringer or beam suitable for use within an airframe. The structure and operation of the surface clamp  52  is described more fully, for example, in co-pending, commonly owned U.S. patent application Ser. No. 11/112,994 entitled “Inflatable Clamping Systems and Methods” filed on Apr. 22, 2005, incorporated herein by reference. Various alternate embodiments of clamping apparatus that may be substituted for the surface clamp  52  are described, for example, in co-pending, commonly owned U.S. patent application Ser. No. 10/648,535 entitled “Adaptable Spring Force Clamping Apparatus and Methods” filed on Aug. 25, 2003, incorporated herein by reference.  
         [0019]     With continued reference to  FIG. 2 , in this embodiment, the edge-clamp system  26  includes an edge-clamp device  56  operatively coupled to a beam  58 . The edge-clamp-device  56  includes a clamp bar  62  rotatably attached to a retainer block  64  by a pivot pin  68 . A securing bolt  66  attaches the retainer block  64  to the beam  58 . In this embodiment, the beam  58  includes an approximately U-shaped cavity  78  for receiving an inflatable bladder (or seal)  60 , and a plurality of threaded holes  80  ( FIG. 3 ) for receiving the securing bolt  66 .  
         [0020]     In operation, as the inflatable seal  60  is pressurized, the inflatable seal  60  applies pressure on a first portion of the clamp bar  62 , rotating the clamp bar  62  about the pivot pin  68  and forcing a second portion of the clamp bar  62  downwardly to apply a clamping force F c  on the first workpiece  24 . The edge-clamp system  26  thereby securely engages the first workpiece  24  against the second workpiece  22  during a manufacturing operation. In this embodiment, the tool  30  is placed between the edge-clamp system  26  and the surface clamp  34  in order to get the tool  30  as close as possible to a common edge of the first and second workpieces  22 ,  24 .  
         [0021]     Additional details of the edge-clamp system  26  are shown in  FIG. 3 . In this embodiment, the U-shaped cavity  78  extends from a first end  86   a  of the beam  58  to a second end  86   b  of the beam  58 . The inflatable seal  60  is received within the cavity  78  and includes a stem  76  that passes through an opening in the cavity  78 . The stem  76  is coupled to the pump  19 . The inflatable seal  60  may be attached to the base of the cavity  78  using, for example, a suitable adhesive. In one particular embodiment, the inflatable seal  60  is a Presray Pneuma-seal® commercially-available from the Pawling Corporation of Pawling, N.Y.  
         [0022]     In the embodiment shown in  FIG. 1 , each end  86   a  and  86   b  of the beam  58  includes through holes  87  for receiving the bolts  36  that secure the beam  58  onto the respective fixture bases  28 . Alternately, each end  86   a,    86   b  of the beam  58  includes a pair of threaded members  84  to secure the beam  58  to the bases  28  and to prevent movement of the beam  58  during a clamping process.  
         [0023]      FIG. 4  illustrates a perspective view of the edge-clamp system  26  of  FIG. 1 . In this embodiment, a plurality of edge-clamp devices  56  are coupled to the beam  58 , and a plurality of seal restriction members  90  are coupled to the beam  58  and interspersed between the edge-clamp devices  56 . More specifically, as shown in the partially exploded view of  FIG. 5 , the securing bolt  66  is threaded through the retainer block  64  and received by one of the threaded holes  80  in the beam  58 . In one embodiment, the edge-clamp devices  56  (and seal restriction members  90 ) are evenly distributed along the beam  58 , however, in alternate embodiments, the edge-clamp devices  56  (and seal restriction members  90 ) may be non-uniformly distributed along the beam at desired locations depending upon the requirements of the manufacturing operation. In further embodiments, a greater or lesser number of edge-clamp devices  56  (and seal restriction members  90 ) may be employed than are shown in  FIG. 4 .  
         [0024]      FIG. 6  is an enlarged partially-exploded view of a portion of the edge-clamp device  26  of  FIG. 4 . In this embodiment, the seal restriction member  90  is coupled to the beam  58  by a bolt  92  that passes through a hole in the seal restriction member  90  and is received by one of the threaded holes  80 . In alternate embodiments, the seal restriction members  90  may be coupled to the beam  58  using any suitable attachment device, or alternately, may be integrally-formed with the beam  58 . The seal restriction member  90 , when attached to the beam  58 , is configured to extend at least partially over the U-shaped cavity  78  of the beam  58 , thereby restricting expansion of the inflatable seal  60  between the edge-clamp devices  56 .  
         [0025]     As shown in  FIG. 6 , in one embodiment, the seal restriction member  90  includes a first portion  91  that contacts the beam  58 , and a second portion  93  that extends over the inflatable seal  60  disposed within the U-shaped cavity  78 . The first portion  91  may have a greater thickness than the second portion  93 . In this embodiment, the thicknesses of the first and second portions  91 ,  93  may be selected to allow the inflatable seal  60  to expand a pre-defined amount that would in turn allow the clamp bar  62  of the edge-clamp device  56  to rotate a pre-set amount, thereby putting proper pressure on the first workpiece  24 .  
         [0026]      FIG. 7  shows an enlarged cross-sectional view of a portion of the edge clamp system  26  of  FIG. 4 . In this embodiment, the clamp bar  62  includes a non-abrasive tip  90  that engages the first workpiece  24  during the clamping operation. In one embodiment, the non-abrasive tip  90  is a polymer tip that reduces marring or scratching of the first workpiece  24  and reduces thermal conduction from the first workpiece  24  into the clamp bar  62  during manufacturing operations (e.g. welding). In this embodiment, the tip  90  is attached to the clamp bar  62  by an attachment pin  92 . Alternately, the tip  90  may be adhesively attached, or attached by any other suitable means to the clamp bar  62 .  
         [0027]      FIG. 8  illustrates the rotational movement of the clamp bar  62  about the pivot pin  68  as the inflatable seal  60  is being pressurized. More specifically, as the inflatable seal  60  is pressurized, a driving force Fd is applied by the inflatable seal  60  against the first end  62   a  of the clamp bar  62 , thus forcing the clamp bar  62  to rotate (generally depicted as arrow R) about the pivot pin  68 . In turn, the second end  62   b  of the clamp bar  62  is forced downwardly, causing the tip  90  to apply the clamping force Fc onto the first workpiece  24 . The clamping force Fc is maintained on the first workpiece  24  until the seal  60  is deflated.  
         [0028]     Embodiments of the present invention may provide significant advantages over the prior art. For example, as depicted in  FIG. 2 , embodiments of edge-clamp systems  26  may allow an edge of a workpiece to be secured using less surface area of the workpiece than alternate clamping systems (e.g. pneumatic surface clamp  32 ), thereby allowing room for the tool  30  while properly securing the workpiece during the performance of manufacturing operations near the edge. Also, embodiments of the invention may provide a low-profile edge-clamping system that operates with a short displacement, thereby performing the desired clamping function without interfering with the performance of the manufacturing operations. Furthermore, as shown in  FIGS. 1 and 4 , embodiments of the invention may advantageously be configured to conform to a variety of surface contours, and may be readily reconfigurable by adjustment of the locations of the edge-clamp devices  56 , the retaining members  90 , and the shape of the beam  58 . Finally, embodiments of the invention may provide relatively quick actuation in comparison with alternative clamping systems.  
         [0029]     While preferred and alternate embodiments of the invention have been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of these preferred and alternate embodiments. Instead, the invention should be determined entirely by reference to the claims that follow.