Abstract:
A hemming machine is provided with a frame, a hemming tool support structure and a swinging drive structure. The hemming tool support structure is rotatably coupled to the frame to rotate about a center rotation axis. The hemming tool support structure includes a hemming tool disposed at a first location such that the hemming tool moves towards and away from an edge part of a workpiece that is supported on a die upon rotation of the hemming tool support structure. The swinging drive structure transmits a rotational driving force to the hemming tool support structure via a releasable connection located on a side of the center rotation axis that is opposite of the hemming tool. The releasable connection is configured to release the swinging drive structure to allow further rotational movement of the hemming tool away from the die.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to Japanese Patent Application No. 2006-041240, filed on Feb. 17, 2006. The entire disclosure of Japanese Patent Application No. 2006-041240 is hereby incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention generally relates to a hemming machine, which hems an edge part of a workpiece, and an inspecting method thereof. 
         [0004]    2. Background Information 
         [0005]    A hemming machine is often used to bend a peripheral edge of a first panel over a peripheral edge of a second panel. One example of a conventional hemming machine is disclosed in Japanese Published Unexamined Patent Application No. 2003-251417. In this conventional hemming machine, a pre-hemming process and a main hemming process are performed by oscillating and moving a frame supporting a pre-hemming tool and a main hemming tool in a straight line using a toggle link mechanism. Furthermore, when performing the main hemming process, the pre-hemming tool is retracted from the frame away from a space between a workpiece and the main hemming tool, which is positioned above the pre-hemming tool. 
         [0006]    The hemming operation involves first oscillating the frame in relation to a base so that the pre-hemming tool and the main hemming tool are located above an edge part of the workpiece, which is on a die. The frame is then moved downward in a straight line to bring the pre-hemming tool nearer to the workpiece and to perform a pre-hemming operation. Next, the pre-hemming tool is moved so that it is retracted from the frame. Now, the main hemming process is performed by drawing the main hemming tool, which is at a position that is higher than the pre-hemming tool, closer to the workpiece by moving the frame further in a straight line. The frame is guided at this time by a cam groove formed in the base, and is oscillated and moved in a straight line. 
       SUMMARY OF THE INVENTION 
       [0007]    However, since the conventional hemming machine described above has a configuration in which the entire frame with a pre-hemming tool and a final hemming tool is moved using a cam groove, numerous steps are required in order to allow for easy inspection operation to be preformed. In particular, this conventional hemming machine has to be partially disassembled in order to obtain an opening angle between the die and the pre-hemming tool and the main hemming tool that is sufficient to allow for easy inspection operation. Accordingly, a substantial amount of labor is required to disassemble the apparatus in order to perform an inspection operation. Consequently, it is difficult to perform the work of inspecting the hemming machine, such as to adjust the pre-hemming tool and the main hemming tool. 
         [0008]    One object of the present invention is to provide a hemming machine that is configured to simplify the work of inspecting a hemming machine. 
         [0009]    In accordance with one aspect of the present invention, a hemming machine is provided that basically comprises a frame, a hemming tool support structure and a swinging drive structure. The hemming tool support structure is rotatably coupled to the frame to rotate about a center rotation axis. The hemming tool support structure includes a hemming tool disposed at a first location such that the hemming tool moves towards and away from an edge part of a workpiece that is supported on a die upon rotation of the hemming tool support structure about the center rotation axis. The swinging drive structure is operatively arranged between the frame and the hemming tool support structure to transmit a rotational driving force to the hemming tool support structure via a releasable connection located on a side of the center rotation axis that is opposite of the hemming tool. The releasable connection is configured to release the swinging drive structure to allow further rotational movement of the hemming tool away from the die. 
         [0010]    These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    Referring now to the attached drawings which form a part of this original disclosure: 
           [0012]      FIG. 1  is a front elevational view of a hemming machine in accordance with one preferred embodiment of the present invention in which the hemming machine is positioned in a state to begin the pre-hemming process; 
           [0013]      FIG. 2  is a left side elevational view of the hemming machine illustrated in  FIG. 1  in accordance with the illustrated embodiment of the present invention; 
           [0014]      FIG. 3  is a partial rear elevational view of the hemming machine illustrated in  FIGS. 1 and 2  in accordance with the illustrated embodiment of the present invention; 
           [0015]      FIG. 4  is a partial front perspective view of the hemming machine illustrated in  FIGS. 1 to 3  in accordance with the illustrated embodiment of the present invention as viewed from the upper right in  FIG. 1 ; 
           [0016]      FIG. 5  is a partial rear perspective view of the hemming machine illustrated in  FIGS. 1 to 4  in accordance with the illustrated embodiment of the present invention as viewed from the upper right in  FIG. 3 ; 
           [0017]      FIG. 6  is a perspective view of a plurality of hemming machines illustrated in  FIGS. 1 to 5  in accordance with the illustrated embodiment of the present invention; 
           [0018]      FIG. 7  is a simplified diagrammatic view of a drive mechanism for sliding a pre-hemming tool mounting bracket with respect to a hemming tool mounting bracket in accordance with the illustrated embodiment of the present invention; 
           [0019]      FIG. 8  is a partial exploded perspective view of the hemming machine illustrated in  FIGS. 1 to 5 , with the hemming tool mounting bracket removed from the vertical slide frame; 
           [0020]      FIG. 9  is a partial exploded perspective view of the hemming machine illustrated in  FIGS. 1 to 5  in accordance with the illustrated embodiment of the present invention; 
           [0021]      FIG. 10  is a partial exploded perspective view of the hemming machine illustrated in  FIGS. 1 to 5  in accordance with the illustrated embodiment of the present invention, as viewed from the opposite side from  FIG. 9 ; 
           [0022]      FIG. 11  is a front elevational view of the hemming machine illustrated in  FIGS. 1 to 5  in accordance with the illustrated embodiment of the present invention, in which a workpiece loaded on the hemming machine to begin operation of the hemming machine; 
           [0023]      FIG. 12  is a front elevational view of the hemming machine illustrated in  FIGS. 1 to 5  in accordance with the illustrated embodiment of the present invention, in which the hemming machine is in a standby state to begin a pre-hemming process; 
           [0024]      FIG. 13  a front elevational view of the hemming machine illustrated in  FIGS. 1 to 5  in accordance with the illustrated embodiment of the present invention, in which the hemming machine is in a state to begin a main hemming process; 
           [0025]      FIG. 14  is a perspective view of the hemming machine illustrated in  FIGS. 1 to 5  in accordance with the illustrated embodiment of the present invention, in which the hemming machine is in a state in which the hemming tool mounting bracket is released from the swing driving structure and a clevis is divided in two parts; and 
           [0026]      FIG. 15  of the hemming machine illustrated in  FIGS. 1 to 5  in accordance with the illustrated embodiment of the present invention, as viewed from the opposite side from  FIG. 14 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0027]    Selected embodiments of the present invention will now be explained with reference to the drawings. It will be apparent to those skilled in the art from this disclosure that the following descriptions of the embodiments of the present invention are provided for illustration only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. 
         [0028]    Referring initially to  FIG. 1 , a hemming machine  1  is illustrated in accordance with a first embodiment of the present invention. A workpiece W is set on a die  3 , which forms a lower mold, of the hemming machine  1 , as shown in  FIG. 1 . The workpiece W is a door panel, which is, for example, a panel material of a vehicle body. The workpiece W has an inner panel Wi and an outer panel Wo. A hemming process is performed on the workpiece W so that an edge part Fo is folded at approximately 90° toward the outer panel Wo, overlaps an edge part Fi of the inner panel Wi. Furthermore,  FIG. 1  shows a state in which a pre-hemming process is performed so that the abovementioned edge part Fo is bent from approximately 90° to approximately 45°. After the pre-hemming process, a final or main hemming process is performed so that the edge part Fo of the outer panel Wo overlaps the edge part Fi of the inner panel Wi. 
         [0029]    As shown in  FIG. 6 , several of the abovementioned hemming machines  1  are installed so that they surround the die  3 , which is discussed later. The basic structures of these hemming machines  1  are completely identical to one another, and the hemming process is performed around the workpiece W by operating these hemming machines  1  simultaneously. Furthermore, the workpiece W is omitted from  FIG. 6 . 
         [0030]    The hemming machine  1  includes a main frame  5 , which serves as a base platform of the hemming machine  1 . As shown in  FIGS. 1 and 4 , the die  3  is installed to a side part of the main frame  5 . The main frame  5  basically includes an inner side plate  7 , an outer side plate  9  and a pair of connecting plates  11 . The inner side plate  7  extends vertically and is adjacent to the die  3 . The outer side plate  9  is installed parallel to and is shorter than the inner side plate  7 . In particular, the outer side plate  9  is at a position so that it is spaced further from the die  3  than the inner side plate  7 . The connecting plates  11  are coupled to both ends of the inner and outer side plates  7  and  9  in their width directions (the lateral direction in  FIG. 2 ). 
         [0031]    An upper part of the inner side plate  7  is provided with two frame guides  13 , which correspond to positions that are substantially above the connecting plates  11 . The two frame guides  13  face toward the outer side plate  9 . The two frame guides  13  are provided so that a vertical slide frame  15 , which serves as a frame, can be slid therebetween in a vertical direction. 
         [0032]    The vertical slide frame  15  includes a pair of side plates  17  and a frame coupling plate  19  as seen in  FIG. 9 . The side plates  17  are parallel to and positioned on the inner sides of the connecting plates  1   1 . The frame coupling plate  19  couples the side plates  17  together. The frame coupling plate  19  is provided in the vicinity of the inner side plate  7 . 
         [0033]    A hemming tool mounting bracket  21  is rotatably mounted to the upper parts of the side plates  17  by a pair of bracket coupling shafts  23  that defines a rotational center axis of the hemming tool mounting bracket  21 . The hemming tool mounting bracket  21  serves as a hemming tool support structure. As shown in  FIG. 5 , the hemming tool mounting bracket  21  includes a pair of bracket side plates  25 , a bracket upper coupling plate  27  and a bracket front coupling plate  29 . The two bracket side plates  25  are coupled to the upper part of a corresponding one of the side plate  17 . Each of the bracket side plates  25  includes an outer plate  25   a  and an inner plate  25   b.  The upper part of each side plate  17  is interposed between the lower parts of a corresponding pair of the outer and inner plates  25   a  and  25   b.  Thus, the outer and inner plates  25   a  and  25   b  sandwiches the side plates  17 . Each of the inner plates  25   b  extends upward from the corresponding one of the outer plate  25   a.  The bracket upper coupling plate  27  couples the upper ends of the bracket side plates  25  together. The bracket front coupling plate  29  couples the front ends, i.e., the right sides in  FIG. 1 , of the bracket side plates  25  together. 
         [0034]    Furthermore, a hemming tool  31  (also called hem blade) is provided to the end part of the bracket front coupling plate  29  on the die  3 . The hemming tool  31  is used when performing the final main hemming process. In addition, prior to performing the main hemming process using the hemming tool  31 , a pre-hemming tool  33  (also called pre-hem blade) is attached to a pre-hemming tool mounting bracket  35 . The pre-hemming tool  33  is used when performing the pre-hemming process as shown in  FIG. 1 . The pre-hemming tool mounting bracket  35  includes a pair of bracket outer side plates  37  and a bracket coupling plate  39 . The bracket outer side plates  37  are positioned on the outer sides of the bracket side plates  25 . The bracket coupling plate  39  couples the end parts (i.e., their right sides in  FIG. 1 ) of the bracket outer side plates  37  together. The pre-hemming tool  33  is attached to the front side (i.e., the right side in  FIG. 1 ) of this bracket coupling plate  39 . The abovementioned hemming tool  31  and pre-hemming tool  33  constitute the hemming tools. 
         [0035]    The pre-hemming tool mounting bracket  35  further includes a pair of guide members  41 . The guide members  41  are respectively provided above the bracket outer side plates  37  of the pre-hemming tool mounting bracket  35 . The guide members  41  move along a pair of guide rails  43  disposed on the lower part of the bracket upper coupling plate  27  of the hemming tool mounting bracket  21 . Thereby, the pre-hemming tool mounting bracket  35  can slide in the lateral direction of  FIG. 1  with respect to the hemming tool mounting bracket  21 .  FIG. 1  shows a state, in which the pre-hemming process is being performed, with the pre-hemming tool mounting bracket  35  moved forward and the pre-hemming tool  33  positioned directly above the die  3 . 
         [0036]      FIG. 7  shows a driving mechanism that slides the pre-hemming tool mounting bracket  35  with respect to the hemming tool mounting bracket  21  to the state shown in  FIG. 1 . The driving mechanism includes a pre-hemming tool slide cylinder  45  having a cylinder body  47 , a rotary support shaft  49 , a piston rod  51  and a rotary support shaft  53 . A rear end of the cylinder body  47  is rotatably coupled to the bracket front coupling plate  29  of the hemming tool mounting bracket  21  via the rotary support shaft  49 . The piston rod  51  extends from the front of the pre-hemming tool slide cylinder  45 . Meanwhile, one end of a bell crank  55  of the driving mechanism is rotatably coupled to a tip of the piston rod  51  via the rotary support shaft  53 . One end of the bell crank  55  is rotatably supported by the bracket side plates  25  of the hemming tool mounting bracket  21  via a rotary center shaft  57 . The other end of the bell crank  55  is rotatably coupled to one end of a linear link  61  via a rotary support shaft  59 . The other end of the linear link  61  is rotatably coupled to a fixture  65 , which is provided to the bracket coupling plate  39  via a rotary support shaft  63 . 
         [0037]      FIG. 7  corresponds to the state in  FIG. 1 , in which the piston rod  51  advances and the pre-hemming tool  33  is positioned above the die  3 . If the piston rod  51  retracts from this state, then the bell crank  55  rotates clockwise in  FIG. 7  about the rotary center shaft  57 , as shown by the chain double dashed line. The linear link  61  rotates counterclockwise in  FIG. 7  about the rotary support shaft  63  and simultaneously moves in the left direction of  FIG. 7 . Also with this movement of the linear link  61  in the left direction, the pre-hemming tool  33  also moves in the left direction of  FIG. 7  and transitions to a state where it is spaced from the die  3 . 
         [0038]    The hemming tool mounting bracket  21  is rotatable about the bracket coupling shaft  23 , as discussed earlier, with respect to the side plates  17  of the vertical slide frame  15 . This rotational operation causes the hemming tool  31  and the pre-hemming tool  33 , which is attached to the pre-hemming tool mounting bracket  35 , to move close to or away from the workpiece W that is set on the die  3 . 
         [0039]    The following explains the mechanism that carries out the rotational operation of the hemming tool mounting bracket  21  about the bracket coupling shaft  23 . As shown in  FIG. 1 , the side plates  17  of the vertical slide frame  15  and the bracket side plates  25  of the hemming tool mounting bracket  21  are coupled by a link mechanism  67  on the left side of the bracket coupling shaft  23 . 
         [0040]    The link mechanism  67  basically includes a pair of lower part links  71  and a pair of upper part links  75 . Each of the lower part links  71  serves as a first link that is rotatably coupled at its lower end to a respective one of the side plates  17  of the vertical slide frame  15  via a rotary support shaft  69 . Each of the upper part links  75  serves as a second link that is rotatably coupled one at its upper end to a respective one of the bracket side plates  25  of the hemming tool mounting bracket  21  via a rotary support shaft  73 . Each of the lower part links  71  is rotatably coupled at its upper end to a respective one of the upper part links  75  by a link support shaft  77 . 
         [0041]      FIG. 8  is an exploded perspective view that shows a state in which the hemming tool mounting bracket  21  in the perspective view of  FIG. 5  is removed from the vertical slide frame  15 . The lower part links  71  are provided along the axial direction of the link support shaft  77 , and the upper part links  75  are also provided along the axial direction of the link support shaft  77 . 
         [0042]    Meanwhile, a swing cylinder  79  is provided to rotate the hemming tool mounting bracket  21 . The swing cylinder  79  serves as a swing driving structure. In particular, the swing cylinder  79  has a cylinder main body  81  with a rear end being rotatably attached to the frame coupling plate  19  via a cylinder rotary support shaft  82  as seen in  FIG. 9 . Thus, the swing cylinder  79  has a cylinder main body  81  is rotatably attached to the side plates  17  of the vertical slide frame  15  by the frame coupling plate  19 . The swing cylinder  79  has a piston rod  83  that extends out of the cylinder main body  81  with a tip of the piston rod  83  being coupled to a clevis  85 . The piston rod  83  serves as a drive rod, while the clevis  85  serves as a coupling member. 
         [0043]    As seen in  FIG. 9 , an exploded perspective view, which excludes the die  3 , shows selected portions of the hemming machine  1 , in which the main frame  5  is detached from the vertical slide frame  15 , which moves vertically along the frame guides  13  with respect to the main frame  5 . Also, in  FIG. 9 , the hemming tool mounting bracket  21  is detached from the vertical slide frame  15  and the pre-hemming tool mounting bracket  35 . The hemming tool mounting bracket  21  is normally attached to the vertical slide frame  15  to rotate about the bracket coupling shaft  23  with respect to the vertical slide frame  15 . The pre-hemming tool mounting bracket  35  is normally attached to the hemming tool mounting bracket  21  such that the pre-hemming tool mounting bracket  35  slides via the guide members  41  with respect to the hemming tool mounting bracket  21 . 
         [0044]    Thereby, the swing cylinder  79  is disposed inside a notched recessed part  19   a,  which is provided to the upper part of the frame coupling plate  19  of the vertical slide frame  15 , and a notched recessed part  7   a,  which is provided to the inner side plate  7  of the main frame  5 . The swing cylinder  79  is rotatably supported on the cylinder rotary support shaft  82  at the rear end of the cylinder main body  81 . The cylinder rotary support shaft  82  rotatably supported on a cylinder mounting unit  87 , which is provided so that it protrudes from the frame coupling plate  19 . The cylinder rotary support shaft  82  is attached so that it is parallel to the bracket coupling shaft  23 . Consequently, when the hemming tool, mounting bracket  21  rotates about the bracket coupling shaft  23 , the cylinder main body  81  rotates about the cylinder rotary support shaft  82 , which makes it possible for the hemming tool mounting bracket  21  to operate smoothly. 
         [0045]    Furthermore,  FIG. 10  is an exploded perspective view, viewed from the far side of  FIG. 9 . The clevis  85  is divided into a segment member  88  and a segment member  89 . The segment member  88  is coupled to the piston rod  83 , while the segment member  89  is coupled to the link support shaft  77 . In addition, these segment members  88  and  89  are joined by two bolts  90 , which serve as a coupler. Two screw holes  88   a  are provided in the segment member  88  on the side of the piston rod  83 . Two bolt insertion holes  89   a  are provided in the segment member  89  on the side of the link support shaft  77 . These two segment members  88  and  89  are integrated by inserting the bolts  90  into the bolt insertion holes  89   a  and tightening them into the screw holes  88   a.  In so doing, the clevis  85  is moved in the left direction of  FIG. 1  by the forward drive of the piston rod  83  in the swing cylinder  79 . Furthermore, starting from the state in  FIG. 1 , the lower part links  71  rotate counterclockwise in  FIG. 1  about the rotary support shafts  69  and the upper part links  75  rotate clockwise in  FIG. 1  about the rotary support shafts  73 . Thus, as shown in  FIG. 11  (discussed later), the hemming tool mounting bracket  21  rotates counterclockwise about the bracket coupling shaft  23  and transitions to a state where it is open with respect to the die  3 . 
         [0046]    The following explains a mechanism in which the vertical slide frame  15  vertically moves the hemming tool mounting bracket  21  and the pre-hemming tool mounting bracket  35  with respect to the main frame  5 . 
         [0047]    As shown in  FIG. 1  and in  FIG. 4 , a servomotor  91  is installed at the lower part of the coupling region between the inner side plate  7  of the main frame  5  and the connecting plates  11 . The servomotor  91  serves as a hemming driving device. Meanwhile, a reduction gear  93  is installed on the inner side plate  7  on the side of the die  3 . The servomotor  91  and the reduction gear  93  are provided with pulleys  95  and  97 , respectively. These pulleys  95  and  97  are coupled by a timing belt  99 . Furthermore, a planetary gear mechanism is used for the reduction gear  93 . 
         [0048]    In addition, as shown in  FIG. 10 , a toggle link mechanism  101  is provided to the inner side plate  7  on the side opposite the reduction gear  93 . The toggle link mechanism  101  includes a pair of drive side linear links  103  and a follower side bent link  105 . One end of each of the drive side linear links  103  is fixedly coupled to an output shaft  107  of the reduction gear  93 . The other end of each of the drive side linear links  103  is rotatably coupled to one end of the follower side bent link  105  via a lower part coupling shaft  109 . The other end of the follower side bent link  105  is rotatably coupled to a coupling hole  19   b  of the frame coupling plate  19  of the vertical slide frame  15  via an upper part coupling shaft  111 . 
         [0049]    Specifically, the drive side linear links  103  of the toggle link mechanism  101  rotate about the output shaft  107  of the reduction gear  93  by the drive of the servomotor  91  via the timing belt  99  and the reduction gear  93 . This causes thee follower side bent link  105  to rotate about the upper part coupling shaft  111  and simultaneously move in the vertical direction. Also the vertical slide frame  15  moves vertically with respect to the main frame  5 . 
         [0050]    The vertical movement of the vertical slide frame  15  causes the hemming tool  31 , which is provided to the hemming tool mounting bracket  21 , and the pre-hemming tool  33 , which is provided to the pre-hemming tool mounting bracket  35 , to also move in the same direction, and thereby the main hemming process or the pre-hemming process is performed. 
         [0051]    As shown in  FIG. 6 , a support stand  113  is installed at each of four locations that are between the hemming machines  1  disposed around the die  3 . A work grasping hand  115  is fixed above the support stands  113 . The work grasping hand  115  clamps the workpiece W, which is not shown in  FIG. 6 , by a plurality of work clamps  117  (which are in an unclamped state in  FIG. 6 ). The work grasping hand  115  are coupled to an arm of a robot (not shown) via a hand changer, which is concealed by a hand changer cover  119  (located at the center upper part of the work grasping hand  115 ). 
         [0052]    In a state where the robot moves and conveys the work grasping hand  115  with the workpiece W clamped thereto, the robot positions the work grasping hand  115  on the support stands  113  and fixes it thereto. The arm of the robot detaches from the hand changer and covers it with the hand changer cover  119 . The hand changer cover  119  is attached to a tip of a rotary arm  121 . The hand changer cover  119  rotates about a support platform  123 , which is on the base end side of the rotary arm  121 . The hand changer cover  119  also moves between a state wherein it covers the hand changer, as shown in  FIG. 6 , and a state wherein it is spaced apart from the hand changer and does not cover it. 
         [0053]    The following explains the hemming operation using the abovementioned hemming machine  1 . First, the swing cylinder  79  is driven forward and the hemming tool mounting bracket  21  transitions to a workpiece receiving state, as shown in  FIG. 11 . In this workpiece receiving state, the hemming tool mounting bracket  21  is wide open with respect to the die  3 , whereupon the workpiece W is placed on the die  3 . At this time, the pre-hemming tool  33  is in the retracted position shown by the chain double dashed line in  FIG. 7 . In addition, the workpiece W transitions to a state in which the outer panel Wo is the lower part and the inner panel Wi is placed thereupon. The edge part Fo of the outer panel Wo is upwardly bent at substantially 90°. 
         [0054]    When setting the workpiece W on the die  3 , the robot (not shown) transports and positions the work grasping hand  115 , which grasps the workpiece W, on the support stands  113 . After that positioning, the robot (not shown) releases the clamping of the workpiece W by the work clamps  117 , as shown in  FIG. 6 . At this time, the workpiece W is easily loaded onto the die  3  because the hemming tool mounting bracket  21  opens at a large angle with respect to the die  3 . Also the hemming tool  31  and the pre-hemming tool  33 , which are at the retracted position, are wide open with respect to the die  3 . 
         [0055]    Next, starting from the state shown in  FIG. 11 , the rearward drive of the swing cylinder  79  moves the clevis  85  in the right direction in  FIG. 11 . This movement of the swing cylinder  79  rotates the lower part links  71  clockwise in  FIG. 11  about the rotary support shafts  69  and also rotates the upper part links  75  counterclockwise in  FIG. 11  about the rotary support shafts  73 . Thus, these links  71  and  75  form a straight line in the vertical direction, as shown in  FIG. 12 . 
         [0056]    Again, starting from the state shown in  FIG. 11 , the hemming tool mounting bracket  21  rotates clockwise about the bracket coupling shaft  23  by the rearward drive of the swing cylinder  79 . Also the hemming tool  31  transitions so that it is at a position above the die  3 . Additionally, the pre-hemming tool slide cylinder  45  is driven forward, and the pre-hemming tool  33  transitions to a state in which it is positioned forward, as shown by the solid line position in  FIG. 7 . The pre-hemming tool  33  is then positioned between the edge part Fo of the outer panel Wo on the die  3  and the hemming tool  31 , as shown in  FIG. 12 . 
         [0057]    From the state shown in  FIG. 12 , the servomotor  91  drives the toggle link mechanism  101 , which is shown in  FIG. 10 . At this time, the drive side linear links  103  of the toggle link mechanism  101  rotate counterclockwise in  FIG. 10  about the output shaft  107  of the reduction gear  93 . This causes the follower side bent link  105  to rotate about the upper part coupling shaft  111  and to descend. Thus, the vertical slide frame  15  descends along with the hemming tool mounting bracket  21 . 
         [0058]    The descent of the hemming tool mounting bracket  21  together with the descent of the vertical slide frame  15  causes the pre-hemming tool mounting bracket  35  to also descend. Since the pre-hemming tool mounting bracket  35  has the pre-hemming tool  33  mounted thereto, the descent of the hemming tool mounting bracket  21  and the vertical slide frame  15  causes the pre-hemming tool  33  to also descend. Thus, the pre-hemming process is thereby performed between the pre-hemming tool  33  and the die  3 , as shown in  FIG. 1 . In the pre-hemming process, the edge part Fo of the outer panel Wo transitions from the substantially 90° folded state shown in  FIG. 11  to the approximately 45° folded state. 
         [0059]    After the pre-hemming process, the servomotor  91  is rotated in a direction that is the reverse of that mentioned above, and thereby the vertical slide frame  15  is raised along with the hemming tool mounting bracket  21 . The pre-hemming tool  33  is also raised and spaced apart from the workpiece W to the position shown in  FIG. 12 . Furthermore, from this position, the pre-hemming tool  33  is moved in the left direction of  FIG. 12  so that it retracts. 
         [0060]    The movement by which the pre-hemming tool  33  retracts is performed by driving the pre-hemming tool slide cylinder  45  so that it retracts, which displaces members from the solid line position to the chain double dashed line position in  FIG. 7 . Thus, the pre-hemming tool  33  retracts from the position above the workpiece W and transitions to a state where it is spaced apart from the workpiece W. 
         [0061]    Starting from this state, the servomotor  91  drives the toggle link mechanism  101 , in the same manner as during the pre-hemming process discussed above, such that the vertical slide frame  15  descends along with the hemming tool mounting bracket  21  and the hemming tool  31 . Thus, the hemming tool  31  presses downward against the edge part Fo of the outer panel Wo, as shown in  FIG. 13 . In other words, the main hemming process is performed between the hemming tool  31  and the die  3 . As a result, the edge part Fo of the outer panel Wo and the edge part Fi of the inner panel Wi are overlapped, and the hemming process is therefore complete. 
         [0062]    After the main hemming process, the servomotor  91  generates a reverse drive, in which the hemming tool  31  is raised with respect to the main frame  5  along with the vertical slide frame  15  and the hemming tool mounting bracket  21 . Also the forward drive of the swing cylinder  79  then rotates the hemming tool  31  and the pre-hemming tool  33 , along with the hemming tool mounting bracket  21  and the pre-hemming tool mounting bracket  35 , about the bracket coupling shaft  23  with respect to the vertical slide frame  15 , thereby transitioning to the state that is the same as that shown in  FIG. 11 . 
         [0063]    Furthermore, after processing the workpiece W, it is clamped by the work clamps  117  of the work grasping hand  115 , which are shown in  FIG. 6 . After which the hand changer cover  119  is removed. Then, in a state in which the arm of the robot is coupled to the hand changer, the robot transports the work grasping hand  115 . Thus, the workpiece W is removed from the die  3 , which awaits the loading of the next workpiece W. 
         [0064]    After the hemming tool  31  and the pre-hemming tool  33  are drawn near to the workpiece W by the swing operation about the bracket coupling shaft  23  of the hemming tool mounting bracket  21 , the movement of the vertical slide frame  15  with respect to the workpiece W is limited to vertical linear motion during the pre-hemming process and the main hemming process. Accordingly, the stroke of that linear motion is short and it is therefore possible to prevent an increase in the overall size of the equipment in the vertical height direction, which facilitates the work of loading and unloading the workpiece W. 
         [0065]    Furthermore, in the hemming process described above, the entire perimeter of the workpiece W can be hemmed at once by simultaneously operating a plurality of hemming machines  1 , as shown in  FIG. 6 . 
         [0066]    The following explains the method of performing the inspection work with respect to the hemming machine  1 . As shown in  FIG. 8 , the inspection work is performed by dividing the clevis  85 , which couples the swing cylinder  79  and the link mechanism  67  (comprising the lower part links  71  and the upper part links  75 ), into the segment member  88  on the side of the piston rod  83  and the segment member  89  on the side of the link support shaft  77 . 
         [0067]    At this time, starting from the state shown in  FIG. 11 , by removing the bolts  90 , the lower part links  71  further rotates counterclockwise in  FIG. 11  about the rotary support shafts  69  so that the segment member  89  on the side of the link support shaft  77  is spaced apart from the segment member  88  on the side of the piston rod  83 . At this time, the hemming tool mounting bracket  21  is left coupled to the link support shaft  77 , as in the state shown in  FIGS. 14 and 15 . 
         [0068]    Accordingly, by dividing the clevis  85 , as mentioned above, into the segment member  88  on the side of the piston rod  83  and the segment member  89  on the side of the link support shaft  77 , the lower part links  71  rotates so that they open widely to the outer side. The hemming tool mounting bracket  21 , which is coupled to the link support shaft  77 , is greatly spaced apart from the die  3  and transitions to a wide opening angle with respect to the die  3 , as shown in  FIGS. 14 and 15 . 
         [0069]    As a result, when the hemming tool  31  or the pre-hemming tool  33  wears down and requires adjustment, the adjustment work can be performed with the hemming tool  31  and the pre-hemming tool  33  attached to the hemming machine  1 , i.e., without having to remove them. In addition, the work of replacing the swing cylinder  79  can also be performed easily. Thus, work efficiency of inspecting the hemming machines  1  is improved. 
       General Interpretation of Terms 
       [0070]    In understanding the scope of the present invention, the term “comprising” and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms, “including”, “having” and their derivatives. Also, the terms “part,” “section,” “portion,” “member” or “element” when used in the singular can have the dual meaning of a single part or a plurality of parts. Moreover, terms that are expressed as “means-plus function” in the claims should include any structure that can be utilized to carry out the function of that part of the present invention. The terms of degree such as “substantially”, “about” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. 
         [0071]    While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. For example, the size, shape, location or orientation of the various components can be changed as needed and/or desired. Components that are shown directly connected or contacting each other can have intermediate structures disposed between them. The functions of one element can be performed by two, and vice versa. The structures and functions of one embodiment can be adopted in another embodiment. It is not necessary for all advantages to be present in a particular embodiment at the same time. Every feature which is unique from the prior art, alone or in combination with other features, also should be considered a separate description of further inventions by the applicant, including the structural and/or functional concepts embodied by such feature(s). Thus, the foregoing descriptions of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.