Abstract:
Weld seams that vary in height along the lengths of a pair of workpieces are produced using at least one laser weld head mounted for vertical and rotary movements to accommodate differences in the vertical heights and contours of seam lines along which the weld seams are to be formed.

Description:
FIELD OF THE INVENTION 
     This invention relates to a welding machine and method particularly for continuously welding elongate workpieces along a continuous seam extending lengthwise of the workpieces to be welded. 
     INCORPORATION BY REFERENCE 
     The entire disclosure of Published Patent Application No. US 2003/0230555 A1 of Kummle, published Dec. 18, 2003, is hereby incorporated by reference herein, and referred to herein as the “Kummle application.” The entire disclosure of U.S. Pat. No. 6,545,246 B2, issued Apr. 8, 2003, is hereby incorporated by reference herein, and referred to herein as the “Kummle patent.” 
     BACKGROUND OF THE INVENTION 
     The Kummle application discloses a welding machine used in conjunction with a production line that includes a roll forming machine. The Kummle application discloses a method wherein the heads of laser welders move vertically up and down for forming welded seams along vertically varying lines for workpieces which have heights which vary along their lengths. However, vertical movements of the laser welders may not be sufficient to produce satisfactory welds because the points of maximal engagement of two parts being welded are not always in the vertical plane along which the laser welders move. 
     The Kummle patent discloses a welding device in line with a roll forming machine. The welding device includes a single energy source connected with at least two welding heads for simultaneously producing two weld joints on a pair of roll-formed workpieces. 
     SUMMARY OF THE INVENTION 
     This invention improves upon the formation of a welded seam on a welded profile which varies in height and slope along the length of the workpieces from which the profile is made. To this end, a laser weld head is mounted for rotary movements as well as vertical movements to enhance the welded connections between the workpieces being welded. 
     As will be apparent, a pair of welded seams could be produced simultaneously on opposite sides of the workpieces. 
     Features and advantages of this invention will become apparent from the following description and claims and from the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front elevational view of a welding machine in accordance with this invention, a workpiece feed assembly, and a workpiece moving through the welding machine and the feed assembly. 
         FIG. 2  is an enlarged cross-sectional view taken on line  2 - 2  of  FIG. 1  showing two workpiece parts which are welded together in the weld machine to form a completed workpiece. 
         FIG. 3  is an enlarged cross-sectional view taken on lone  3 - 3  of  FIG. 1  showing the two parts of the workpiece after being welded together. 
         FIG. 4A  is a fragmentary isometric view, with parts broken away and parts in cross section, of a laser welder support assembly and a laser welder supported thereby and also showing parts of a hold-down roll and squeeze roll assembly.  FIG. 4  additionally shows a workpiece passing through the hold-down roll and squeeze roll assembly. 
         FIG. 4B  is a top plan view of the laser welder support assembly and a laser welder supported thereby with parts broken away and parts shown in cross section.  FIG. 4B  also includes a plan view of the seam tracking assembly of this invention. 
         FIG. 5  is an enlarged fragmentary cross sectional view of the workpiece and a hold-down roll subassembly taken on line  5 - 5  of  FIG. 1 . 
         FIG. 5A  is an enlarged cross-sectional view of a portion of the hold-down roll assembly within the circular section line  5 A of  FIG. 5 . 
         FIG. 6  is an enlarged fragmentary cross sectional view of the workpiece and a squeeze roll subassembly taken on line  6 - 6  of  FIG. 1 . 
         FIG. 7  is a simplified, exploded isometric view of the hold-down roll and squeeze roll assembly, a fragment of the welder and the welder support assembly, and the seam tracking assembly on both the front and back of the track along which the profile moves through the welding machine. 
         FIG. 8  is an enlarged, simplified, fragmentary view, with parts in cross section, taken on line  8 - 8  of  FIG. 6  of the workpiece and the hold-down roll and squeeze roll assembly.  FIG. 8  also shows an upstream hold-down roll subassembly to the right of the hold-down roll assembly and squeeze roll assembly and a downstream pre-tension roll subassembly to the left of the hold-down roll assembly and squeeze roll assembly as viewed in  FIG. 8 . The location of the weld point is diagrammatically indicated in  FIG. 8 . 
         FIG. 9  is a view similar to  FIG. 8  but showing a different portion of the workpiece engaged with the rolls. 
         FIG. 10  is a view similar to  FIGS. 8 and 9  but showing still different portions of the workpiece engaged with the rolls. 
         FIG. 11  is a further simplified, diagrammatic view showing yet another section of the workpiece engaged with the rolls and diagrammatically indicating the weld point and the contact point of the pinch roll with the workpiece. 
         FIG. 12  is a diagrammatic view similar to  FIG. 11  indicating a condition in which the weld point is slightly spaced from the optimum weld point. 
         FIG. 13  is a further simplified, diagrammatic view on a much larger scale than  FIG. 12  and indicating the same condition illustrated in  FIG. 12 . 
         FIG. 14  is a fragmentary isometric view, partly in cross section, on a scale smaller than  FIG. 3 , of the completed workpiece. 
     
    
    
     DETAILED DESCRIPTION 
     A welding machine  18  in accordance with this invention is illustrated in  FIG. 1  as located along a track  20  between an upstream workpiece feed station  22  and a downstream welded profile exit station  24 . With reference also to  FIGS. 2 ,  3  and  14 , the workpieces fed to the welding machine  18  comprise an elongate metal profile base member  26  and an elongate metal strip  28 . The profile base member  26  may be referred to as an inverted π-shaped member having a strip-like base plate  30  and a pair of upstanding support rails  32  which have top edges  34 . The illustrated profile base member  26  may be extruded from a metal blank (not shown) but this invention could be used with profile members (not shown) having various different shapes and manufactured by roll-forming or other methods of manufacture. The method of this invention could be used to manufacture elongate parts for use in aircraft. For example, the profile base member  26  could be as long as 40 feet or even longer. Typically, the metal strip  28  would be cut to the same length as the profile base member  26 . 
     The placement of the metal strip  28  on the profile base member  26  creates a pair of seams  36  between the bottom surface of the metal strip  28  and the top edges  34  of the support rails  32 . As diagrammatically illustrated in  FIG. 3 , the metal strip  28  and the profile base member  26  are welded together along the seams  36  to form a welded seam  36 A. ( FIG. 3  diagrammatically represents welds alongside the welded seams  36 A but in reality the welded seams  36 A are created by the melting and bonding together under heat and pressure of the metal material from which the metal strip  28  and the profile base member  26  are formed.) The completed welded profile is identified by reference number  38  herein. 
     It will be noted that the top edges  34  of the support rails  32  are not uniformly spaced from the bottom surface of the profile base plate  30 . Rather, the top edges  34  of the support rails  32  are sinuous along their lengths. Therefore, the seams  36  along which the metal strip  28  is welded to the support rails  32  progresses in a wavy pattern from one end of the profile base member  26  to the other as will be further described below. 
     Referring again to  FIG. 1 , the upstream workpiece feed station  22  can be of conventional construction and may comprise plural support rolls  40  and feed rolls  42  for the profile base member  26 , guide rolls  44  and feed roles  46  for the metal strip  28  and conventional guide systems  48  and  50  for both the profile base member  26  and the metal strip  28 . As the profile base member  26  and the metal strip  28  enter the welding machine  18 , the metal strip  28  is effectively clamped to the top edges  34  of the rails  32  of the profile base member  26 . 
     With reference to FIGS.  1  and  8 - 10 , the illustrated welding machine  18  includes an array of five side-by-side pressure rolls, namely a first upstream hold-down roll  52 , a second upstream hold-down roll  54 , a center pinch roll  56 , a first downstream hold-down roll  58  and a further downstream pre-tension roll  60 . These all apply a downward pressure exerted on top of the metal strip  28  while the profile base member  26  is supported from below by an array of support and drive rolls  62 . The rolls  52 ,  54 ,  56 ,  58  and  60  are rotatably mounted for rotation about their respective horizontal axes. 
     As is believed evident, the first and second upstream hold-down rolls  52  and  54  firmly clamp the metal strip  28  to the top of the profile bass member rails  32 . As will be described in greater detail below, the welding of the metal strip  28  to the profile base member  26  occurs close to the bottom of the center pinch roll  56 . The first and second downstream rolls  58  and  60  continue to apply pressure to the metal strip  28  to ensure that the welded seam  36 A remains secure as the completed welded profile  38  continues to move downstream from the center pinch roll  56 . The second downstream roll  60  is also provided to pre-tension the completed welded profile  38  to overcome the natural tendency of the metal strip  28  to curve upwardly due to the heating of the completed welded profile  38  caused by the welding process as the completed welded profile  38  moves downstream from the center pinch roll  56 . Progressing downstream from the welding station  18 , the completed welded profile  38  is guided by guide rolls  64  along the exit station  24  for further processing or removal from the exit station  24 . As those familiar with the art are aware, the completed welded profile  38  would usually undergo further processing to achieve its desired final configuration. 
     With reference again to  FIG. 1  and also to  FIGS. 5-7 , the welding machine  18  has a set of four, vertically extending, guide and support posts  66  mounted on the machine bed  68  that support a cylinder support plate  70  above the welding machine rolls  52 ,  54 ,  56 ,  59  and  60 . Mounted on the cylinder support plate  70  are three hydraulic pressure-applying cylinders, namely an upstream hold-down cylinder  72 , a middle, pinch roll pressure cylinder  74  and a downstream pre-tension cylinder  76 . 
     The guide and support posts  66  also guide a ram  78  for vertical movement beneath the cylinder support plate  70 . With reference to  FIGS. 6 and 7 , fixed in any suitable fashion to the bottom of the ram  78  is a pinch roll pressure plate  80  connected, as illustrated in  FIGS. 6 and 7 , by screws  82  to pinch roll bearing housings  84  at opposite ends of the pinch roll  56 . The top surfaces of the bearing housings  84  engage flush against shoulders  86  formed at both sides of the pinch roll pressure plate  80 . As apparent, pinch roll cylinder  74  acting through the ram  78 , pinch roll pressure plate  80  and the pinch roll bearing housings  84  can be energized to directly apply pressure to the pinch roll  56 . By virtue of this construction an appropriate pinch roll pressure can be maintained throughout the passage of the profile base member  26  and the metal strip  28  under the pinch roll  56  to ensure that the seam  36  is under uniform pressure during the welding operation. 
     Referring now to  FIGS. 5 and 7 , the hold-down roll  58  immediately downstream from the pinch roll  56  is supported at its ends by bearings  88  mounted in bearing housings  90  depending from and fixed to a roll support plate  92  by screws (not shown). A hydraulic, downstream hold-down roll actuator  94  threadedly mounted in bore  96  in the ram  78  applies a downward force against a force transmitting shaft  98  slidably received within a through bore  92 A in the pinch roll pressure plate  80  aligned with the piston rod  100  of the hydraulic downstream hold-down roll actuator  94 . Downward pressure is applied to the welded profile  38  by the piston  100  of the hydraulic actuator  94  which bears downwardly against the top end of the force-transmitting shaft  98  when the hydraulic actuator  94  is energized. The force-transmitting shaft  98  is threadedly connected at its lower end  102  to the downstream roll support plate  92 . There is no connection between the force-transmitting shaft  98  and the piston rod  100 , thereby to enable the force-transmitting shaft  98  to slide within the central bore  92 A as will be discussed below. 
     With continued reference to  FIGS. 5 and 7 , a constant downward force is exerted on the downstream hold-down roll  58  by the hydraulic actuator  94  as the completed welded profile  38  passes through the welding machine  18 . Thereafter, the hydraulic actuator  94  may be de-energized and the downstream hold-down roll  58  elevated by a pair of downstream hold-down roll lifting assemblies  104 , each of which includes a compression spring  106  trapped beneath a spring cap  108  slidably received within a compression spring-receiving bore  110  in the ram  78 . With reference also to  FIG. 5A , each lifting assembly  104  further includes a lifting post  112  connected by a screw  114  at its upper end to the associated spring cap  108 . Each lifting post  112  extends downwardly through a through bore  116  in the roll support plate  92 . Flanges  118  encircling the lower ends of the lifting posts  112  are received within counterbores  116 A at the bottom of the roll support plate  92 . The compression springs  106  assert a significantly lower upward force on the roll support plate  92  than the downward force created by the hydraulic actuator  94  when the actuator  94  is energized. Therefore, the lifting assemblies  104  are only effective when the hydraulic actuator  94  is not energized. 
     As shown in  FIG. 5 , a pair of cylindrical connectors  120  having enlarged heads  122  slidable within bores  124  in the pinch roll pressure plate  80  and having threaded lower ends  126  threadedly connected to the roll support plate  92  are provided to prevent the accidental falling of the roll support plate  92  and the downstream hold-down roll  54  should, for example, the screws  114  at the top of the lifting posts  112  be removed for purposes of disassembly. 
     The housing  12  may be manufactured in a generally flat form illustrated in  FIG. 6 . After removed from the mold (not shown), the housing components  14  and  16  can be rotated around the hinge  18  to bring their confronting faces together toward one another around the hinge  18 , whereupon the tongues  42  enter the grooves  36  and hold the two housing components  14  and  16  in their face-to-face relationship. 
     Here it may be noted that the upstream hold-down roll  54  is mounted in precisely the same manner as the downstream hold-down roll  58  just described and corresponding parts are identified by the same reference numbers. Therefore, the mounting of upstream hold-down roll  54  is not further described herein. 
     With reference to  FIGS. 1 ,  4 A,  4 B,  6  and  7 , the welded seams  36 A which affix the metal strip  28  to the profile base member  26  are created will now be described. Two laser welding assemblies, a front assembly  200  and a rear assembly  202  are mounted adjacent the track  20  along which profile members  26  and  28  move in line with the pinch roll  56 . The two laser welding assemblies  200  and  202  may be essentially identical and only the front laser welding assembly  200  is described in detail herein, with like parts of the two laser assemblies  200  and  202  illustrated in the drawings being identified by like reference numbers. 
     With reference to  FIGS. 4A ,  4 B,  6  and  7 , the laser welding assembly  200  includes a laser welding head  204  which includes laser optics  206  that produce a cone-shaped laser beam  208  focused at a focal point  210  on the seam  36  to be welded as it passes the outer margin of the pinch roll  56 . The focal point  210  is also referred to herein as the “weld point  210 ” herein because the focal point  210  is also the point at which the seam  36  is welded. As best illustrated in  FIG. 4A , fine adjustments of the location of the focal point  210  of the laser beam  208  may obtained by the use of adjusting mechanisms  212  and  214  with drive motors  216  and  218 , respectively. The adjusting mechanism  212  and  214  may be entirely conventional and, although critical to precisely locating the focal point  210 , are not part of the present invention and not further described herein. 
     A laser mounting plate  224  supports the laser welding assembly  200 . Mounting plate  224  in turn is supported by a pair of support blocks  226  provided with dovetail slots  228  that are slidably mounted on a pair of generally vertical mounting tracks  229  affixed to the front face  230  of a rotatable support member  232  forming part of a seam tracking assembly  234  in accordance with this invention. The rotatable support member  232  is mounted by bearings  236  for rotation about the shaft  238  on which the pinch roll  56  is rotatably mounted so that the rotatable support member  232  is rotatable about the axis of the pinch roll  56 . Due to the adjustably fixed connection between the rotatable support member  232  and the laser welding assembly  200 , the laser welding assembly  200  will rotate in unison with the rotation of the rotatable support member  232  about the horizontal, longitudinal axis of the pinch roll  56 . 
     The rotatable support member  232  is caused to rotate about the axis of the pinch roll shaft  238  vertical movements as best shown in  FIG. 7 , the seam tracking assembly  234  also includes a first, upstream bearing housing  240  rotatably mounted on the shaft of the upstream hold-down roll  54  immediately adjacent the pinch roll  56 ; a second, downstream bearing housing  242  rotatably mounted on the downstream hold-down roll  58  immediately adjacent the pinch roll  56 ; a motion transmitting plate  244  over the top of the rotatable support member  232  and guided for generally vertical movements relative to the rotatable support member  232  by a pair of guide posts  246  that extend through generally vertical, aligned through bores  248  and  250  in the rotatable support member  232  and the motion transmitting plate  244 , respectively; and a generally horizontal connecting rod  252  that extends through aligned bores  254 ,  256 , and  258  in first, upstream bearing housing  240 , the motion transmitting plate  244 , and the second, downstream bearing housing  242 , respectively. 
       FIGS. 8 ,  9  and  10  illustrate the upstream hold-down roll  54 , the pinch roll  56  and the downstream hold-down roll  58  engaged with different portions of the metal strip  28  as the metal strip passes beneath them. Due to the constructions described above, the three rolls  54 ,  56  and  58  are always engaged with the metal strip  28  while the metal strip  28  is being welded to the profile base member  26 . At the position shown in  FIG. 8 , all three rolls  54 ,  56  and  58  are at the same height. In  FIG. 9 , the hold-down rolls  54  and  58  are elevated above the level of the pinch roll  56  due to the illustrated concave contour of the metal strip  28 .  FIG. 9  also illustrates a condition in which the upstream hold-down roll  54  is higher than the downstream hold-down roll  58  so that the rotatable support member slants from upper right to the left due to the operation of the seam tracking assembly  234 . In  FIG. 10 , the hold-down rolls  54  and  58  are below the level of the pinch roll  56  due to the illustrated convex contour of the metal strip  28  at that point. 
     The importance of the seam tracking assembly  234  is illustrated by  FIGS. 11-13 .  FIG. 11  diagrammatically illustrates the three rolls  54 ,  56  and  58  engaged with a downwardly sloping portion of the metal strip. An imaginary circle  156  extends around the pinch roll  56  that has a radius which is greater than the radius of the pinch roll  56  by a length equal to the thickness of the metal strip  28 . The ideal weld point  210  is a point at which the imaginary circle  156  is intersected by a radial line  232  that extends from the center of the pinch roll  56  through the point of contact of the pinch roll  56  with the top surface of the metal strip  28  and through the seam line  36  where it is intersected by the imaginary circle  156 . Because of the slope of the portion of the metal strip  28  engaged by pinch roll  56 , the point of engagement, designated  128  in  FIG. 11 , of the pinch roll  56  with the metal strip  28  is not on a vertical line, designated  130  in  FIG. 11 , passing through the center of the pinch roll  56  but rather on line  132  passing through the center of the pinch roll  56 , which line  132  is counterclockwise from the vertical line  130  by a few degrees. Thus, the focal point  210  of the laser welding head  204 , would be located on the same line  132  that passes through the center of the pinch roll  56  and the point of engagement  128  of the pinch roll  56  with the metal strip  28 . 
     Whenever the rolls  54 ,  56  and  58  are on slope which is the same for all of them, such as when the three rolls  54 ,  56  and  58  are on a horizontal section of the metal strip  28 , the center of the pinch roll  56 , the engagement point  128  of the pinch roll  56  with the metal strip  28  and the weld point  210  will be on the same radial line. In all other cases, in the practice of this invention, it is not possible to locate the weld point  210  precisely along the line that extends between the center of the pinch roll  56  and the engagement point  128 . Rather, as in an example diagrammatically illustrated in  FIGS. 11-13 , the weld point will not be precisely ideally located but will be located sufficiently close to the seam  36  as to create a satisfactory weld. With the contours sloping as shown in  FIGS. 11 and 12  the focal or weld point  210  on the imaginary circle  156  is slightly clockwise from the engagement point  128  of the pinch roll  56  with the metal strip  28 .  FIG. 13  diagrammatically illustrates the condition existing in  FIG. 12 , but on a greatly enlarged scale. This shows that the weld point  210  is only a very short distance from directly engaging the imaginary circle  156  on which weld points are ideally located. In practice, as an example, if the pinch roll  56  has a diameter of 55 mm, and the metal strip  28  has a thickness of 2.5 mm, the condition illustrated in  FIGS. 11-13 , the actual weld point  210  would be spaced from the imaginary circle  156  by only approximately 0.050 mm as illustrated in  FIGS. 12 and 13 . Other weld points offset from ideal will occur at as parts of the workpieces having different contours pass through the welding machine. Other workpieces (not shown) having various different contours will typically also have locations at which the weld points may be satisfactory but less than ideal. Of course, there may be circumstances in which the contours of workpieces to be welded are such that welding by the method and machine of this invention may not be usable. 
     The pressure exerted on the pinch roll  56  may be advantageously regulated to be uniform throughout a welding operation as may the pressures exerted on the second upstream hold-down roll  54  and the first downstream hold-down roll  58 . The combined downstream pressures exerted on the latter hold-down rolls  54  and  58  should be less than the pressure exerted on the pinch roll  56  so that the pinch roll  56  will maintain the profile base member  26  and the metal strip  28  pinched against one another. Otherwise, the hold down rolls  54  and  58  may tend to lift the pinch roll  56 . 
     It will be understood that, within the purview of the invention, various changes may be made within the scope of the following claims.