Abstract:
A non-contact fusion welding apparatus has a pair of programmable clamps carried on universally movable positioners. The positioners are programmed to move the clamps sequentially along a laser weld path so that the clamps, engage and support opposite surfaces of the pair of workpieces at respective selected locations during the weld process to insure intimate and continuous contact between the workpieces along the entire length of the laser weld site.

Description:
TECHNICAL FIELD  
       [0001]     This invention relates to non-contact fusion welding and, more particularly, to a workpiece clamping apparatus and method for insuring intimate and continuous contact between the workpieces during non-contact fusion welding.  
       BACKGROUND OF THE INVENTION  
       [0002]     Non-contact fusion welding techniques such as laser welding, electron beam welding, plasma welding and arc welding are known in the art for joining metal and polymer workpieces. In order for a non-contact fusion weld to be properly formed, the workpieces to be joined must be in continuous contact along the entire length of the weld. Any gaps between the workpieces can result in malformed pieces or a weld having insufficient strength. Previously devised clamps for non-contact fusion welding are sometimes inadequate for insuring continuous contact, since these clamps may only engage a portion of the workpiece at a location separate or apart from the weld site. As a result, the workpieces may not be adequately forced together to insure continuous contact during the welding process.  
         [0003]     Thus, it is desirable to provide a clamping apparatus for non-contact fusion welding operations which insures intimate and continuous contact between the workpieces or parts along the entire length of the weld site. It is also desirable to provide a clamp for non-contact fusion welding which can be configured in a variety of shapes to conform to any desired weld pattern or part shape.  
       SUMMARY OF THE INVENTION  
       [0004]     The present invention provides non-contact fusion welding apparatus having a pair of programmable clamps carried by universally movable positioners. The positioners are programmed to move the clamps sequentially adjacent a weld path or sequentially adjacent selected weld locations so that the clamps, engage and support opposite surfaces of a stacked pair of workpieces during welding to insure intimate and continuous contact between the stacked workpieces along the entire length of the weld.  
         [0005]     In an exemplary embodiment, the non-contact fusion welding apparatus employs a welding laser. However, other such non-contact welding devices such as an arc welder, a plasma welder or an electron beam welder may be substituted for the welding laser.  
         [0006]     A first programmable positioner in the form of a programmable robot includes a base having a jointed arm carrying the welding laser and an upper clamping member (upper clamp). Alternatively, the robot may have a jointed arm carrying an upper clamping member and another jointed arm carrying a welding laser. The non-contact fusion welding apparatus further includes a suitable holding fixture or support adapted to carry a temporary structural assembly formed of stacked metal or polymer workpieces. The apparatus also includes a second programmable positioner located beneath the support.  
         [0007]     The second positioner includes a base that is linearly movable along a rail extending about the length of the support. The base carries a positionable lower clamping member (lower clamp) adjustably supported by a plurality of control arms. The control arms and the base are adjustable by programmable controls to adjust the position of the base along the rail and the attitude and position of the lower clamp relative to the base.  
         [0008]     A structural assembly comprising a pair of workpieces in temporary assembly with opposing surfaces in contact for laser welding at selected locations is carried by the support of the welding apparatus. The first and second positioners subsequently position the upper and lower clamps adjacent a first selected location so that the clamps engage opposite surfaces of the structural assembly to hold the workpieces together. The laser is then operated to form a laser weld at the first selected location adjacent the clamps.  
         [0009]     After welding the first selected location, the clamps are repositioned adjacent subsequent selected locations. As the clamps engage the assembly at the subsequent locations, the laser is re-aimed at the respective locations to sequentially form welds at each of the selected locations. Once all of the locations are welded, the structural assembly is completed and removed from the support.  
         [0010]     These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a schematic pictorial view of a non-contact fusion welding apparatus according to the invention; and  
         [0012]      FIG. 2  is a similar view of an alternative embodiment of the non-contact fusion welding apparatus of  FIG. 1 . 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0013]     Throughout the following description and drawings, like reference numerals refer to like components shown in the various figures of the drawing.  
         [0014]     Referring to  FIGS. 1 and 2  of the drawings, numeral  10  generally indicates a structural assembly in the form of a tunnel undershield and tunneled floor pan of a vehicle. The structural assembly includes first and second stacked metal or polymer workpieces  12 ,  14  and the assembly has upper and lower surfaces  16 ,  18 .  
         [0015]      FIG. 1  shows an exemplary embodiment of a non-contact fusion welding apparatus  22 . The apparatus  22  includes a first positioner  24  in the form of a robot  26 . If appropriate, any other suitable form of programmable positioner may be substituted for the robot  26  within the scope of the invention. The robot  26  includes a base  28  and a jointed arm  30  carrying a welding laser  32  and an upper clamping member (upper clamp)  34 .  
         [0016]     The non-contact fusion welding apparatus  22  further includes a suitable holding fixture or support  36  adapted to carry the structural assembly  10 . The apparatus  22  also includes a programmable positioner  38  located beneath the support. The positioner  38  includes a base  40  that is linearly movable along a rail  42  extending along the length of the support  36 . The base  40  carries a positionable lower clamping member (lower clamp)  44  adjustably supported by a plurality of control arms  46 . The control arms  46  and the base  40  are adjustable by programmable controls, not shown, to adjust the position of the base along the rail  40  and the attitude and position of the lower clamp  44  relative to the base.  
         [0017]     In operation, the spatial coordinates of the structural assembly  10  are programmed into the positioners  24 ,  38 . Structural assembly  10 , comprising workpieces  12 ,  14  in temporary assembly with opposing surfaces in contact for laser welding at selected-locations, is placed onto the support  36  of the welding apparatus  22 . The first and second positioners  24 ,  38  subsequently position the upper and lower clamps  34 ,  44  adjacent a first selected location  48  so that the clamps engage opposite surfaces  16 ,  18  of the structural assembly  10 . The laser  32  is then aimed toward the first selected location  48  and energized to form a laser weld at the first selected location. If desired, the laser may form a seam weld for a distance adjacent the clamps to form a seam weld at the selected location.  
         [0018]     After a weld is created at the first selected location, the laser  32  and the clamps  34 ,  44  may be sequentially repositioned at subsequent selected locations  52  to allow the laser  32  to form multiple spot or seam welds  50  at the subsequent locations. After all of the selected locations  52  are welded, the structural assembly is removed from the support.  
         [0019]      FIG. 2  shows an alternative welding apparatus  60  similar to welding apparatus  22  where the welding laser  32  is removed from the jointed arm  30  and alternatively carried by a third positioner, such as jointed positioning arm  64  extending from the base  28  of the robot  26 . In addition, the upper and lower clamps  34 ,  44  are replaced with upper and lower roller clamps (clamping members)  66 ,  68  adapted to be rolled along the surface of the structural assembly  10 .  
         [0020]     In operation, welding apparatus  60  operates similarly to welding apparatus  22  in that the upper and lower roller clamps  66 ,  68  are positioned oppositely at selected locations  52  of a structural assembly  10  to provide clamping force holding together the workpieces  12 ,  14  to insure a high quality weld. Positioning arm  64  aims the welding laser  32  at the selected location  52 , which is clamped by the roller clamps  66 ,  68 . The laser is then energized to form a weld  50  at the selected location.  
         [0021]     As the laser forms the weld  50 , the laser  32  and the roller clamps  66 ,  68  may be moved along their respective surfaces  16 ,  18 , from the selected location  52 , to form a seam weld  50  connecting the workpieces  12 ,  14 . As the clamps are moved along their respective surfaces they maintain clamping pressure to insure contact between the workpieces  12 ,  14 . As needed, the positioners  24 ,  38  reposition the roller clamps  66 ,  68  to maintain optimal clamping pressure and contact along the contours of the structural assembly  10 . As a result, a high quality laser seam weld  50  can be formed between the workpieces  12 ,  14 .  
         [0022]     While the invention has been described by reference to certain preferred embodiments, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the disclosed embodiments, but that it have the full scope permitted by the language of the following claims.