Abstract:
Workpieces are unloaded from a workpiece support of a sheet metal workpiece processing apparatus by positioning a blank sheet metal workpiece over a processed workpiece supported on a workpiece support, with the blank workpiece releasably held by a workpiece loader, activating a workpiece fixing device to engage an edge of the processed workpiece, and performing a relative sweeping movement between the workpiece fixing device and the workpiece support whereby the engaged processed workpiece is prevented from remaining on the workpiece support and is thereby unloaded. The workpiece fixing device is moved relative to the processed workpiece while the blank sheet metal workpiece is positioned over the processed workpiece.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of and claims priority under 35 U.S.C. §120 to PCT Application No. PCT/EP2011/067779 filed Oct. 12, 2011, which claimed priority to European Application No. 10 188 498.9, filed Oct. 22, 2010. The contents of both of these priority applications are hereby incorporated by reference in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to unloading processed workpieces, in particular metal sheets, from a support after processing. 
       BACKGROUND 
       [0003]    US 2003/0147729A1 discloses a mechanical arrangement having a machine tool for processing metal sheets and having a mechanical loading and unloading device for the machine tool. The loading and unloading device has a machine frame on which a loading unit in the form of a suction member frame and a gripping member of an unloading unit are driven in a motorized manner and moved in a numerically controlled manner. Using the suction member frame, metal sheets to be processed are supplied to a workpiece support of the machine tool. The metal sheets to be processed are picked up by means of suction members of the suction member frame from a pallet which is arranged below the workpiece support and deposited on the workpiece support after a subsequent lifting movement of the suction member frame and the metal sheet which is held thereon. After the workpiece support has been loaded with a metal sheet to be processed, the suction member frame is again lowered to a level below the workpiece support. After completion of the metal sheet processing operation, the gripping member moves in a horizontal direction from a parking position into a sweeping position. In the sweeping position, the gripping member grips an edge of the processed metal sheet which itself rests on the workpiece support of the machine tool. With the gripping member remaining in the sweeping position, the workpiece support is pulled out below the processed metal sheet parallel with the support plane which is formed on the workpiece support. The processed metal sheet, which is fixed to the gripping member and which consequently cannot follow the movement of the workpiece support, is swept from the workpiece support and deposited on a pallet arranged below the workpiece support. The suction member frame and the gripping member are operated in a mutually co-ordinated manner, but are separated from each other in terms of driving. 
       SUMMARY 
       [0004]    One aspect of the invention features a mechanical arrangement or machine system for processing a workpiece such as a metal sheet. The arrangement or machine system includes a workpiece support, a loading device and an unloading device. The loading device has a workpiece holding member which is movable in a driven manner relative to the workpiece support and by means of which a workpiece can be supplied to the workpiece support by the workpiece holding member together with a workpiece secured thereto being able to be moved with a loading movement relative to the workpiece support. The unloading device is in the form of a sweeping device which has a workpiece fixing device and by means of which a workpiece can be swept from the workpiece support by the workpiece fixing device being able to be moved with a positioning movement into a sweeping position in which a workpiece to be swept off can be secured to the workpiece fixing device and by the workpiece secured to the workpiece fixing device on the one hand and the workpiece support on the other hand being able to be moved relative to each other with the workpiece being swept from the workpiece support with a sweeping movement. 
         [0005]    Another aspect of the invention features a method for unloading workpieces from a workpiece support of a mechanical arrangement for processing workpieces, in particular metal sheets, which has a loading device having a workpiece holding member which is movable in a driven manner relative to the workpiece support and an unloading device in the form of a sweeping device having a workpiece fixing device. A workpiece is supplied to the workpiece support by means of the loading device by the workpiece holding member of the loading device together with a workpiece secured thereto being moved with a loading movement relative to the workpiece support. The workpiece is swept from the workpiece support by means of the sweeping device by the workpiece fixing device of the sweeping device being moved with a positioning movement into a sweeping position in which a workpiece to be swept off is secured to the workpiece fixing device and by the workpiece secured to the workpiece fixing device on the one hand and the workpiece support on the other hand being moved relative to each other with a sweeping movement with the workpiece being swept from the workpiece support. 
         [0006]    The workpiece fixing device of the sweeping device, during the positioning movement thereof into the sweeping position, is at least partially connected to the workpiece holding member of the loading device. Owing to the coupling in terms of movement of the workpiece fixing device and the workpiece holding member, the drive of the workpiece holding member can at the same time be used for the positioning movement of the workpiece fixing device. The drive of the workpiece fixing device and the workpiece holding member can consequently be produced with little structural complexity. Owing to the dual use of one and the same drive, components can be saved in comparison with the use of two separate drives. The saving in terms of components again leads to a compact structure of the overall arrangement. 
         [0007]    In a preferred embodiment of the invention, the movement connection between the workpiece fixing device of the sweeping device and the workpiece holding member of the loading device is produced by means of a mechanical connection for the sake of simplicity. 
         [0008]    In some embodiments, to this end, the workpiece fixing device is fitted to a carrier structure of the workpiece holding member. The workpiece holding member has holding elements of conventional construction type by means of which workpieces to be processed are secured to the workpiece holding member during the loading operation. For example, suction members or retention magnets can be used as holding elements. 
         [0009]    In some embodiments, there is provision for the workpiece fixing device and/or the workpiece holding member to be able to be lowered below the workpiece support. The workpiece fixing device and/or the workpiece holding member can accordingly be moved into positions in which they do not impede the operations at the upper side of the workpiece support, in particular the workpiece processing operation which is carried out at that location, and in which they are at the same time protected from process-related influences, such as contamination. Furthermore, the workpiece fixing device and the workpiece holding member can be passed over by the workpiece support when it has corresponding movability. This results in a space-saving construction of the mechanical arrangement. 
         [0010]    The sweeping movement for unloading workpieces from the workpiece support can be produced in different manners. In some cases, the workpiece support is moved relative to the workpiece which is secured to the workpiece holding device of the unloading device, with the workpiece being swept off. In order to produce the sweeping movement, use is consequently made of the movability of the workpiece support which is already present in many cases. The workpiece fixing device can remain in the sweeping position during the sweeping operation. 
         [0011]    In some embodiments, the workpiece fixing device of the unloading device has a fixing member which is provided specifically for securing the workpiece to be swept off 
         [0012]    In some cases, the workpiece fixing device which is moved into the sweeping position can be activated or deactivated. In the activated state, the workpiece fixing device secures the workpiece to be swept off. The fact that the workpiece fixing device can be selectively activated or deactivated has been found to be advantageous in particular in view of the coupling in terms of movement of the workpiece fixing device to the workpiece holding member of the loading device. It is in particular possible to deactivate the workpiece fixing device during the positioning movement into the sweeping position carried out together with the workpiece holding member and to produce the activated state of the workpiece fixing device only when it has reached the sweeping position and consequently has to be in the position to secure workpieces which are to be swept from the workpiece support. Preferably, the spatial requirement of the unit comprising the workpiece fixing device and the workpiece holding member when the workpiece fixing device is deactivated is smaller than when the workpiece fixing device is activated. 
         [0013]    If the workpiece fixing device has a fixing member, it is recommended, in order to activate or deactivate the workpiece fixing device, to move the fixing member with an activation movement into an operational position or with a deactivation movement into a non-operational position. The non-operational position of the fixing member is in particular selected in such a manner that the fixing member does not impede the positioning movement of the workpiece fixing device into the sweeping position. 
         [0014]    In the interests of the simplest kinematic relationships possible, in another preferred embodiment for moving the fixing member of the workpiece fixing device into the operational position and/or into the non-operational position, an at least partially linear activation movement is preferred. 
         [0015]    In particular linear activation and/or deactivation movements may be produced by means of a piston/cylinder unit. In order to operate the piston/cylinder unit, it is possible to use media, in particular compressed air or pressurized fluids, which are in any case required in mechanical arrangements of this type. 
         [0016]    Some embodiments are characterized by a structurally particularly simple construction, wherein the fixing member of the workpiece fixing device is in the form of a stop. A component specifically intended for fixing workpieces to be swept off may be used as the stop. Alternatively, however, it is also possible to provide devices used in other manners as the stop for workpieces to be swept off. In particular components of the workpiece holding member are conceivable as the stop, such as, for example, base members of suction members, which otherwise serve to secure workpieces to the workpiece holding member. 
         [0017]    In the interests of functionally reliable operation of the mechanical arrangement and undisrupted implementation of the method, in some examples workpieces which are swept from the workpiece support are guided by means of the workpiece fixing device. The workpiece guiding ensures that the workpieces swept from the workpiece support move along a defined movement path. Workpieces can thereby in particular be prevented from damaging components or devices in their vicinity during sweeping from the workpiece support. 
         [0018]    The invention is explained in greater detail below with reference to exemplary schematic illustrations. 
     
    
     
       DESCRIPTION OF DRAWINGS 
         [0019]      FIG. 1  is a perspective view of a mechanical arrangement for processing metal sheets having a punching machine and an automation unit. 
           [0020]      FIGS. 2 and 3  are various views of a workpiece fixing device of the automation unit according to  FIG. 1 . 
           [0021]      FIGS. 4-11  sequentially illustrate a processing cycle in the mechanical arrangement according to  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    According to  FIG. 1 , a mechanical arrangement  1  for punching processing of workpieces in the form of (blank) metal sheets  2  comprises a punching machine  3  and an automation unit  4 . 
         [0023]    The punching machine  3  has a C-shaped machine frame  5  having an upper frame member  6  and a lower frame member  7 . At the free end of the upper frame member  6  is a punch drive  8  of a punching station  9  of the punching machine  3 . At the punching station  9 , a punching stamp which is guided on the upper frame member  6  is moved in conventional manner relative to a punching die which is provided on the lower frame member  7  in a stroke direction  10 . 
         [0024]    A workpiece support  11  is supported on the lower frame member  7  and comprises two movable support portions  12 ,  13  which are arranged on either side of a stationary support portion  14 . The movable support portions  12 ,  13  can be moved by means of a drive (not illustrated) in a movement direction (double-headed arrow)  15  along the lower frame member  7 . Both the movable support portions  12 ,  13  and the stationary support portion  14  of the workpiece support  11  are provided with conventional support brushes  16  at the upper side thereof. 
         [0025]    In the jaw space of the machine frame  5  of the punching machine  3 , a coordinate guide  17  of conventional structural form is accommodated. This conventionally comprises a transverse rail  18  and a transverse guide  19  which is provided therefor. The transverse rail  18  is movably guided on the transverse guide  19  in a movement direction (double-headed arrow)  20 . The movement direction  20  of the transverse rail  18  extends perpendicularly relative to the movement direction  15  of the movable support portions  12 ,  13  of the workpiece support  11 . In conventional manner, clamping claws for fixing the workpieces which are to be processed (not shown for reasons of simplicity) are fitted to the transverse rail  18 . Furthermore, the transverse rail  18  of the punching machine  3 , which is illustrated by way of example, is also used as a linear magazine for punching tools. Together with the transverse guide  19  and the movable support portions  12 ,  13  of the workpiece support  11  that are connected thereto, the transverse rail  18  can move in the movement direction  15  of the movable support portions  12 ,  13 . Owing to the movement possibilities of the transverse rail  18 , workpieces which are secured to the transverse rail  18  by means of the clamping claws can be moved with respect to the punching station  9  in a horizontal plane which is defined by means of the movement directions  15 ,  20 . In conventional manner, the movement possibilities of the transverse rail  18  are also used for tool changing at the punching station  9 . 
         [0026]    The automation unit  4  is located in the direct vicinity of the punching machine  3 . It forms a separate unit without any mechanical connection to the machine frame  5  of the punching machine  3 . 
         [0027]    The automation unit  4  has a guiding column  21  and a cantilever arm  22  which protrudes therefrom in a horizontal direction. The cantilever arm  22  is movably guided on the guiding column  21  in a vertical movement direction  23  (double-headed arrow). During movements in the movement direction  23 , the cantilever arm  22  is driven by a motorized drive  24 , which in turn is accommodated in a drive housing mounted on the guiding column  21 . 
         [0028]    A suction member frame  25  is suspended from the lower side of the cantilever arm  22 . It is provided with a plurality of holding elements which are constructed as suction members  26  in the example shown. The cantilever arm  22 , the suction member frame  25  and the suction members  26  form a workpiece holding member  27 . The cantilever arm  22  assumes the function of a carrier structure of the workpiece holding member  27 . 
         [0029]    The workpiece holding member  27  having the cantilever arm  22 , the suction member frame  25  and the suction members  26  can be raised in the movement direction  23  above the workpiece support  11  of the punching machine  3  and be lowered below the workpiece support  11 . This movement possibility of the workpiece holding member  27  is used to load the workpiece support  11  with (blank) metal sheets  2 . In this regard, the automation unit  4 , which is provided with the workpiece holding member  27 , forms a loading device of the mechanical arrangement  1 . 
         [0030]      FIG. 1  shows the workpiece holding member  27  in the upper end position on the guiding column  21 . Below the suction member frame  25  and the suction members  26 , in the remaining free space at that location, a blank metal sheet pallet  28  is arranged with blank metal sheets  2  to be processed. The blank metal sheet pallet  28  is supported on a pallet carriage  29 . This can be moved manually on guide rails  30 . 
         [0031]    Substantially concealed in  FIG. 1  is a completed part pallet  31 , which can move in the same direction as the pallet carriage  29 . To this end, the completed part pallet  31  is supported on guide rails  32  by means of an undercarriage  33 . The movement unit, which comprises the undercarriage  33  and the completed part pallet  31 , engages over the pallet carriage  29  with the blank metal sheet pallet  28 , which is supported thereon in the manner of a portal. Consequently, the completed part pallet  31  can move along the guide rails  32  over the blank metal sheet pallet  28 . The height of the undercarriage  33  is selected in such a manner that the completed part pallet  31  is located with the upper side thereof below the workpiece support  11  of the punching machine  3 . The completed part pallet  31  can therefore move below the workpiece support  11  in the direction of the guide rails  32 , which extend in the movement direction  15 , or can be passed over by the workpiece support  11  in the mentioned direction. 
         [0032]    Also concealed to a great extent in  FIG. 1  are workpiece fixing devices  34  which are secured to the rear side of the cantilever arm  22  remote from the observer of  FIG. 1 . In the example shown, a total of three workpiece fixing devices  34  are arranged along the cantilever arm  22 . Together, the workpiece fixing devices  34  serve to sweep processed workpieces from the workpiece support  11  of the punching machine  3  for unloading. In this regard, the automation unit  4 , which is provided with the workpiece fixing devices  34 , forms an unloading device of the mechanical arrangement  1  constructed as a sweeping device. 
         [0033]    One of the three structurally identical workpiece fixing devices  34  is illustrated in detail in  FIGS. 2 and 3 . 
         [0034]    On a transverse member  35  of a securing angled member  36 , the workpiece fixing devices  34  are screwed to the rear longitudinal side of the cantilever arm  22  in  FIG. 1  and consequently connected to the cantilever arm and the entire workpiece holding member  27  mechanically and also in terms of movement. A longitudinal member  37  of the securing angled member  36  carries a first drive unit  38 . Together with a second drive unit  39 , the first drive unit  38  forms an activation/deactivation drive  40  for a fixing member  41  of the workpiece fixing device  34 , constructed as a stop. Both the first drive unit  38  and the second drive unit  39  are pneumatic piston/cylinder units. 
         [0035]    A retention element  43  which is provided with a peripheral groove  42  is located on the piston rod of the first drive unit  38 . In the peripheral groove  42  of the retention element  43 , a plate  44  engages with a fork-like end. At the opposing end, the plate  44  is welded to a carrying and guiding plate  45  for the second drive unit  39 . 
         [0036]    By the first drive unit  38  being actuated, the second drive unit  39  can be moved back and forth via the plate  44  and the carrying and guiding plate  45  in the direction of a double-headed arrow  46 . This movement direction of the second drive unit  39  extends coaxially with the movement direction  15  of the movable support portions  12 ,  13  of the workpiece support  11 . During the movement in the direction of the double-headed arrow  46 , the second drive unit  39  is guided at the inner side of the securing angled member  36  remote from the first drive unit  38 . A guide rail  47  at the inner side of the longitudinal member  37  of the securing angle  36  can be seen in  FIG. 3 . 
         [0037]    A piston rod  48  of the second drive unit  39  engages via a yoke  49  on a guiding rod  50 . The guiding rod  50  is supported on the yoke  49  so as to be rotationally movable about the longitudinal axis thereof. It is a component of a vertical guide  51  for the fixing member  41 . 
         [0038]    The vertical guide  51  is a slotted guiding member having a guide pin  52  fitted to the guide rod  50  and having a guide slot  53  integrated in the axially parallel wall of a guide pipe  54  fitted to the carrying and guiding plate  45  for the guide rod  50 . The guide slot  53  comprises end portions  55 ,  56  which extend linearly in a vertical direction and which are offset relative to each other in the peripheral direction of the guide pipe  54  and a transition portion  57 , which connects the linear end portions  55 ,  56  to each other and which is inclined with respect to the vertical. 
         [0039]    At the end located in the direction towards the fixing member  41 , an arm  58  is fitted to the guide rod  50 . The arm  58  itself carries the fixing member  41 , which protrudes downwards. This member is arranged eccentrically relative to the longitudinal axis of the guide rod  50 . Overall, there is produced at the lower end of the guiding rod  50  a crank-like arrangement with the fixing member  41  as a crank pin. A guiding plate  59  projects beyond the arm  58  in the longitudinal direction thereof and is fitted to the lower side of the arm  58 . 
         [0040]    By the second drive unit  39  being actuated, the guide rod  50  can be raised and lowered together with the fixing member  41 , which is fitted thereto in a vertical direction (double-headed arrow)  60 . Associated with the vertical movement is a rotational movement of the guide rod  50 , which is brought about by the vertical guide  51  about the longitudinal axis of the guide rod  50 . A pivot movement of the fixing member  41  and the guiding plate  59  about the longitudinal axis of the guide rod  50  results from the rotation movement of the guide rod  50 . 
         [0041]    In  FIGS. 2 and 3 , the piston rod of the first drive unit  38  of the workpiece fixing device  34  is retracted in the associated piston. The second drive unit  39  is consequently moved in the direction of the double-headed arrow  46  into the end position thereof, which is located in the direction towards the cantilever arm  22  in the assembly position. At the same time, the guiding rod  50  of the second drive unit  39  assumes the upper end position thereof in the direction of the double-headed arrow  60 . Linked with this is an orientation of the arm  58  which is mounted on the guiding rod  50  in a rotationally secure manner and the guiding plate  59  parallel with the longitudinal direction of the cantilever arm  22 . On the whole, the workpiece fixing device  34  is deactivated in  FIGS. 2 and 3 . The fixing member  41  is located in the non-operational position. 
         [0042]    In order to activate the workpiece fixing device  34  or to move the fixing member  41  into the operational position, the first drive unit  38  and the second drive unit  39  are to be actuated starting from the state shown in  FIGS. 2 and 3 . Owing to the actuation of the first drive unit  38 , the second drive unit  39  moves in the direction of the double-headed arrow  46  into a position in which it has maximum spacing from the cantilever arm  22  in the direction of the double-headed arrow  46 . The actuation of the second drive unit  39  results in the guide rod  50  moving in the direction of the double-headed arrow  60  into the lower end position thereof. A rotation movement of the guide rod  50  brought about by the vertical guide  51  is associated with this linear movement of the guide rod  50 . Owing to the rotation movement of the guide rod  50 , the fixing member  41  pivots about the longitudinal axis of the guide rod  50  into a position in which the arm  58  extends perpendicularly to the longitudinal side of the cantilever arm  22  and in which the fixing member  41  is consequently moved as close as possible to the cantilever arm  22 . At the end of the partially linear, partially rotational activation movement, the fixing member  41  is in the operational position. The same applies to the guiding plate  59  which, owing to the movement of the guide rod  50 , also carries out a linear movement in the direction of the double-headed arrow  60  and a pivot movement about the longitudinal axis of the guide rod  50 . 
         [0043]    In the same manner as all the remaining significant components of the mechanical arrangement  1 , the workpiece fixing devices  34  are also controlled by a numerical machine control unit  61  shown in  FIG. 1 . 
         [0044]    An operating cycle in the mechanical arrangement  1  begins with the operating state illustrated in  FIG. 1 . The workpiece holding member  27  with the cantilever arm  22 , the suction member frame  25  and the suction members  26  is arranged over the blank metal sheet pallet  28 . In the movement direction  23 , the workpiece holding member  27  is in the upper end position, in which the suction members  26  protruding downwards on the suction member frame  25  are located higher than the upper side of the movable support portions  12 ,  13  of the workpiece support  11 . 
         [0045]    The workpiece fixing devices  34  at the rear side of the cantilever arm  22  are in the deactivated state of  FIGS. 2 and 3 . The second drive unit  39  of each of the workpiece fixing devices  34  is moved as close as possible to the cantilever arm  22  in the direction of the double-headed arrow  46 . The guiding rod  50  of the second drive units  39  is located in the upper end position thereof and the fixing members  41  of the workpiece fixing devices  34  accordingly assume their non-operational position. The arm  58  and the guiding plate  59  of the workpiece fixing devices  34  extend parallel with the longitudinal side of the cantilever arm  22  and consequently also parallel with the front longitudinal edge of the movable support portion  13  of the workpiece support  11  facing the cantilever arm  22 . Overall, the projection of the workpiece fixing devices  34  is minimized in the direction towards the movable support portion  13 . 
         [0046]    Below the movable support portion  13 , the completed part pallet  31  is moved into the rear end position thereof located in the direction towards the transverse rail  18  of the punching machine  3 . The movable support portion  13  of the workpiece support  11  also takes up the rear end position thereof in the movement direction  15  in  FIG. 1 . 
         [0047]    Starting from the relationships shown in  FIG. 1 , the workpiece holding member  27  is lowered by means of the motorized drive  24  in the movement direction  23  until the suction members  26  on the suction member frame  25  touch the (blank) metal sheet  2 , which is placed on the blank metal sheet pallet  28  in the uppermost position. The operating state shown in  FIG. 4  is consequently produced. 
         [0048]    The cantilever arm  22  and with it the entire workpiece holding member  27  is now arranged below the workpiece support  11 . During the lowering movement, inter alia the cantilever arm  22  with the workpiece fixing devices  34  fitted thereto must pass the workpiece support  11 , more specifically the movable support portion  13 , in the vertical direction. Regardless of this, the automation unit  4  can be constructed close to the front end of the movable support portion  13  that is arranged in the rear end position, which front end extends parallel with the longitudinal direction of the cantilever arm  22 , since the workpiece fixing devices  34  are in the deactivated state during the lowering movement of the cantilever arm  22 . Their protrusion with respect to the rear side of the cantilever arm  22  is consequently minimized. 
         [0049]    After being placed on the uppermost (blank) metal sheet  2  of the blank metal sheet pallet  28 , the suction members  26  are activated by applying a vacuum. Subsequently, the workpiece holding member  27  with the (blank) metal sheet  2  fixed to the suction members  26  is raised by the motorized drive  24  with a loading movement in the direction towards the upper end position thereof. In the reached position, the (blank) metal sheet  2  held by the workpiece holding member  27  (cantilever arm  22 , suction members frame  25 , suction members  26 ) is also located above the workpiece support  11 . Consequently, the movable support portion  13  of the workpiece support  11  may move in the movement direction  15  from the rear into the front end position thereof below the (blank) metal sheet  2  held on the suction members  26 . The resultant relationships are illustrated in  FIG. 5 . 
         [0050]    The suction members  26  are now deactivated and the (blank) metal sheet  2  previously held on the suction members  26  is transferred to the workpiece support  11  or the movable support portion  13  and taken up at that location by the clamping claws of the coordinate guide  17 . After the (blank) metal sheet  2  has been taken up, the workpiece support  11  first moves in the movement direction  15  from the front end position as shown in  FIG. 5  into the rear end position thereof. When the workpiece support  11  has reached the rear end position thereof, the workpiece holding member  27 , with the workpiece fixing devices  34  still deactivated, is lowered again below the level of the workpiece support  11  into the position shown in  FIG. 4 . 
         [0051]    The (blank) metal sheet  2  is then processed. The (blank) metal sheet  2  is moved, by means of the coordinate guide  17  and with the workpiece support  11  being moved, relative to the punching station  9  of the punching machine  3 . From the (blank) metal sheet  2 , completed parts are cut out until they are connected to the remaining metal sheet only by means of so-called micro-joints. Owing to the micro-joints, the completed parts remain in the composite metal sheet. During the metal sheet processing operation, the workpiece support  11  with the movable support portion  13  moves over the tool holding member  27  which has previously been lowered into the lower end position. 
         [0052]    As illustrated in  FIG. 6 , at the end of the processing operation, the (processed) metal sheet  2  is supported to a great extent on the movable support portion  12  of the workpiece support  11 . At this time, the movable support portions  12 ,  13  of the workpiece support  11  are located close to the front end position thereof. In  FIG. 6 , the movable support portion  13  consequently allows the completed part pallet  31  to be seen on which already (processed) metal sheets  2  are placed. 
         [0053]    After the processing operation has ended, the transverse rail  18  moves in the movement direction  20  into the end position thereof on the movable support portion  13 . The transverse rail  18  carries the (processed) metal sheet  2  which is held thereon by means of the clamping claws. At the same time, the workpiece support  11  with the movable support portion  13  moves into the rear end position in the movement direction  15 . The workpiece holding member  27  is lowered as before. The suction members  26  of the workpiece holding member  27 , during the previous sheet metal processing operation, have taken up another (blank) metal sheet  2  from the blank metal sheet pallet  28 . The workpiece fixing devices  34  at the rear side of the extension arm  22  of the workpiece retention member  27  are still in the deactivated state. The relevant operating state of the mechanical arrangement  1  is illustrated in  FIG. 7 . 
         [0054]    Starting therefrom, the workpiece holding member  27  with the metal sheet  2  fixed thereto is raised with a loading movement in the direction towards the upper end position. At the same time, the workpiece fixing devices  34  which are mounted on the cantilever arm  22  and which are further deactivated are thereby moved with a positioning movement in the movement direction  23  into the sweeping position. With the workpiece fixing devices  34  being deactivated as before, the workpiece support  11  now moves with the movable support portion  13  in the movement direction  15  from the rear into the front end position thereof. The (processed) metal sheet  2  on the workpiece support  11  consequently arrives below the (blank) metal sheet  2  which is held on the workpiece holding member  27  and which is still to be processed ( FIG. 8 ). 
         [0055]    At the rear side of the cantilever arm  22 , the fixing members  41  of the deactivated workpiece fixing devices  34  are located above the (blank) metal sheet  2  which is fixed to the workpiece holding member  27  and consequently also above the (processed) metal sheet  2  which rests on the workpiece support  11 . As seen in  FIG. 9 , the arms  58  and the guiding plates  59  of the workpiece fixing devices  34  that are raised into the sweeping position extend substantially parallel with the rear longitudinal edges of the two mentioned metal sheets  2 . The arms  58  and the guiding plates  59  and the fixing members  41  of the workpiece fixing devices  34  are located in the movement direction  15  or in the direction of the double-headed arrow  46  over the metal sheets  2 . 
         [0056]    Starting from these relationships, the first drive units  38  of the workpiece fixing devices  34  are actuated first ( FIGS. 2 ,  3 ). Consequently, the second drive units  39  of the workpiece fixing devices  34  move in the direction towards the transverse rail  18  of the coordinate guide  17 . The arms  58  and the guiding plates  59  of the workpiece fixing devices  34  remain in a state orientated parallel with the edges of the (blank) metal sheet  2  on the workpiece holding member  27  and the (processed) metal sheet  2  on the workpiece support  11  but are now offset with respect to the mentioned sheet metal edges in the direction towards the transverse rail  18 . 
         [0057]    The second drive units  39  of the workpiece fixing devices  34  are now activated. Consequently, the guiding rods  50  with the fixing members  41  move downwards from their upper end position. Referring also to  FIG. 3 , as long as the guiding pin  52  on the guiding rods  50  moves in the linear end portion  55  of the guiding slot  53  on the guiding pipe  54 , the guiding rod  50  and with it the arm  58 , the guiding plate  59  and the fixing member  41  of each workpiece fixing device  34  carries out only a downwardly directed translation movement. If, during this translation movement the arm  58  of the workpiece fixing devices  34  has passed the (blank) metal sheet  2  held on the workpiece holding member  27 , the guiding pin  52  of the guiding rods  50  reaches the transition portion  57  of the associated guiding slot  53  in each case. Consequently, the guiding rods  50  of the workpiece fixing devices  34  rotate about their longitudinal axis and thereby pivot the arms  58  with the fixing members  41  fitted thereto and the guiding plates  59  below the (blank) metal sheet  2  fixed to the workpiece holding member  27 . The arms  58  and the guiding plates  59  of the workpiece fixing devices  34  reach the intermediate space between the lower side of the (blank) metal sheet  2  on the workpiece holding member  27  and the upper side of the (processed) metal sheet  2  placed on the workpiece support  11 . The fixing members  41  of the workpiece fixing devices  34 , at the end of their activation movement, are adjacent the rear longitudinal edge of the (processed) metal sheet  2  resting on the workpiece support  11  ( FIG. 10 ). 
         [0058]    Below the workpiece support  11 , the completed part pallet  31  has moved from the rear end position into the front end position thereof, where it is located with the upper side thereof below the movable support portion  13  and extends over the blank metal sheet pallet  28  in the manner of a portal. 
         [0059]    The workpiece support  11  with the movable support portion  13  is now moved in the movement direction  15  from the front end position into the rear end position. The (processed) metal sheet  2  on the movable support portion  13  abuts the fixing members  41  of the workpiece fixing devices  34  with the rear longitudinal edge thereof. The fixing members  41  bear against the (processed) metal sheet  2  and thereby prevent a common movement with the movable support portion  13 , which is moving into the rear end position thereof. The movable support portion  13  is thereby pulled out from below the (processed) metal sheet  2 . The (processed) metal sheet  2  is swept off from the workpiece support  11  and reaches the completed part pallet  31  which is located in the front end position thereof ( FIG. 11 ). 
         [0060]    When moving into the rear end position, the workpiece support  11  is passed by the fixing members  41  of the stationary workpiece fixing devices  34  protruding beyond the lower side of the (processed) metal sheet  2  in the movement direction  15 . This is readily possible since the upper side of the workpiece support  11  is provided with support brushes  16  whose resilient bristles can deviate laterally with respect to the fixing members  41 . 
         [0061]    The guiding plates  59  act as a guide for the (processed) metal sheet  2 , which has been swept from the workpiece support  11  when it is transferred onto the completed part pallet  31 . In particular, the guiding plates  59  ensure that the workpiece swept from the workpiece support  11  does not pivot upwards with the rear longitudinal edge thereof in an uncontrolled manner and thereby damage the lower side of the (blank) metal sheet  2  held on the workpiece holding member  27  or the workpiece holding member  27  itself. 
         [0062]    When the (processed) metal sheet  2  is swept from the workpiece support  11  and transferred to the completed part pallet  31 , the workpiece fixing devices  34  are changed into the deactivated state and the workpiece support  11  moves with the movable support portion  13 , which is now unloaded, from the rear end position into the front end position below the (blank) metal sheet  2  fixed to the workpiece holding member  27 . In order to deactivate the workpiece fixing devices  34 , the second drive units  39  of the workpiece fixing devices  34  are actuated first. The arms  58  and the guiding plates  59  of the workpiece fixing devices  34  are thereby orientated parallel with the rear longitudinal edge of the (blank) metal sheet  2  and lifted above the (blank) metal sheet  2 . Subsequently, the second drive units  39  are pulled towards the cantilever arm  22  of the workpiece holding member  27  by the first drive units  38  being actuated. The deactivation movement of the fixing members  41  is thereby ended. 
         [0063]    As soon as the workpiece support  11  has been moved with the movable support portion  13  below the (blank) metal sheet  2  on the workpiece holding member  27 , the (blank) metal sheet  2  can be transferred to the workpiece support  11  and the coordinate guide  17  in order to carry out the punching workpiece processing operation. 
         [0064]    A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.