Abstract:
There is provided a machine for processing workpieces. In one embodiment, there is provided a workpiece processing machine including a processing tool movable to engage a workpiece with a force applied along a tool drive axis, a spindle member coupled to the processing tool and having two helical spindle drive threads spaced apart along the tool drive axis, through which drive threads tool forces are transmitted, and one or more drive motors operable to move the spindle member by applying force through the spindle drive threads to displace the spindle member and the tool along the tool drive axis, wherein the processing tool is coupled to the force transmission member to transmit force from the tool to the spindle member by a force transfer element coupled to the spindle member so as to distribute the force between both of the spindle drive threads.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a continuation of, and claims priority under 35 U.S.C. §120 to PCT/EP2005/005635, filed on May 25, 2005, and designating the U.S., and claims priority under 35 U.S.C. §119 from European application No. 04 012 522.1, filed May 27, 2004. These priority applications are hereby incorporated by reference in their entirety. 
     
    
     TECHNICAL FIELD  
       [0002]     This invention relates to industrial equipment, and more particularly to machines and methods for working with workpieces, such as metal sheets.  
       BACKGROUND  
       [0003]     As those of ordinary skill in the art will appreciate, punching machines may be employed to punch holes or other cut-outs from a workpiece (e.g., a metal sheet). Typically, punching machines include a tool bearing for a punching tool and a rotary/lifting drive, which moves the tool bearing back and forth along a lifting axis to a working area of the punching machine. Also, the tool bearing is rotatably adjustable about the lifting axis. The punching machine may also include a motor-driven spindle transmission provided with a drive control system. Typically, a rotary/lifting drive having two electric drive motors is provided for the tool bearing of a punching machine. Both drive motors may be arranged laterally next to a drive spindle, which in turn runs in the direction of a lifting axis of the tool bearing. One of the drive motors serves for workpiece punching and for that purpose is connected via a belt drive to a lifting spindle nut disposed on the drive spindle. By driving this spindle transmission in one direction of rotation, the tool bearing (and hence the attached punching tool) is moved with working strokes towards the workpiece to be processed and then by reversing the motor, the tool bearing is moved in the opposite direction. The second drive motor in a conventional punching machine is intended for rotary adjustment of the tool bearing and the punching tool. This drive motor is connected via another belt drive to enable rotation of the punching tool relative to the lifting axis.  
         [0004]     Moreover, with a non-uniform force distribution to the two drive units, as would happen, for example, with force introduction at one end of a common drive spindle of two drive units, the drive units would have to accommodate different loads. A uniform construction of the drive units would then be possible only if considerable disadvantages were accepted. For instance, with a uniform construction of the drive units but significantly nonuniform load distribution there would be, for example, a markedly different wear behavior of the two drive units. The service life of the more heavily loaded drive unit would fall considerably behind the service life of the less heavily loaded drive unit. The running properties of the two drive units would also be different from each other. For instance, greater component deformation would occur on the more heavily loaded drive unit than on the less heavily loaded drive unit, the result being that in turn the uniformity of the rotary movements at both drive units would become impaired.  
         [0005]     A more efficient punching tool would be desirable.  
       SUMMARY  
       [0006]     Accordingly, one embodiment provides a lifting drive with a spindle transmission, which has two coaxial drive units with spindle transmission elements associated with one another. The introduction of processing forces and recoil forces resulting therefrom into the spindle transmission is effected, viewed in the direction of the common spindle transmission axis, between the thread engagements of the spindle transmission elements of the two drive units close to the workpiece and remote from the workpiece. The forces to be absorbed by the spindle transmission during workpiece processing are consequently distributed uniformly to the two drive units.  
         [0007]     In one case, the common force introduction element serves for distribution of forces effective in the direction of the spindle transmission axis and/or in the transverse direction with respect to the spindle transmission axis to the drive units of the inventive machine. In another case, in the interests of a structural simplification of the lifting drive, the common force introduction element of the two drive units of the spindle transmission is constructed in modular form (e.g., one piece) with a force transmission element, which for its part transfers to the common force introduction element the force to be introduced by the common force introduction element into the drive units.  
         [0008]     Another configuration is distinguished by a compact method of construction. In another case, “central” force introduction is of particular advantage for machines. For example, the mutual preloading of the spindle drive elements of the drive units provided on such machines is on the one hand of great importance for the functional capability of the relevant drive units. Thus, the zero play of the thread engagement between the spindle transmission elements resulting from the mutual preloading of the spindle transmission elements allows, for example, stroke control of the drive units and a direction of rotation reversal of the spindle transmission elements rotated relative to one another without associated vibrations. At the same time, however, on account of the zero play of their spindle transmission elements such drive units respond especially sensitively to the introduction of massive loads, since there is no possibility of accommodating deformations, occurring at the spindle transmission elements, through play between these components.  
         [0009]     For similar reasons, in other cases, the relative rotary movements of the spindle transmission elements of the two drive units are oppositely directed. With a uniform construction of the drive elements but non-uniform load distribution, non-uniform load situations would occur at the two drive units, which in turn could result in distortion of the drive units relative to one another. The uniform “central” introduction of force at lifting drives counteracts such negative phenomena To generate the oppositely directed rotary movements of the mutual spindle transmission elements, each of the drive units may have its own drive motor. If an appropriate gear mechanism is used, operation of the drive units is alternatively possible with a single drive motor.  
         [0010]     Another configuration employs punching machines in which high processing forces often have to be applied and corresponding recoil forces have to be led off. In another example, an axial preloading arrangement effective in the direction of the spindle transmission axis is provided on punching machines for the spindle transmission elements close to the workpiece. Such preloading arrangements may increase the service life and the operational reliability of the lifting drive of punching machines.  
         [0011]     In particular, when the punching tool strikes the workpiece, when the punching tool penetrates the workpiece and generally during reversal of the stroke movement, load alternation occurs at the lifting drive. The preloading arrangement according to the invention counteracts such a sudden load alternation at the lifting drive. With an appropriate selection of preloading, a swelling loading of the spindle transmission, causing less wear, occurs instead of an alternating loading.  
         [0012]     In the punching operation, as the workpiece to be processed is being subjected to the action of the punching tool a force directed oppositely to the direction of the working stroke builds up inside the lifting drive. As soon as the workpiece is penetrated by the punching tool, the punching tool and the components of the lifting drive connected to it tend to perform a sudden movement in the direction of the working stroke. The sudden load alternation accompanying this would be associated at the lifting drive with an operating state that could be controlled and regulated only with comparatively great effort.  
         [0013]     In another embodiment, there is provided a workpiece processing machine including a processing tool movable to engage a workpiece with a force applied along a tool drive axis, a spindle member coupled to the processing tool and having two helical spindle drive threads spaced apart along the tool drive axis, through which drive threads tool forces are transmitted, and one or more drive motors operable to move the spindle member by applying force through the spindle drive threads to displace spindle member and the tool along the tool drive axis, wherein the processing tool is coupled to the f spindle member to transmit force from the tool to the spindle member by a force transfer element coupled to the force transmission member so as to distribute the force between both of the spindle drive threads.  
         [0014]     In yet another configuration, there is provided a workpiece processing machine including a processing tool movable to engage a workpiece with a force applied along a tool drive axis, a spindle member coupled to the processing tool and having two helical spindle drive threads spaced apart along the tool drive axis, through which drive threads tool forces are transmitted, and one or more drive motors operable to move the spindle member by applying force through the spindle drive threads to displace the spindle member and the tool along the tool drive axis, wherein the spindle member is coupled to the two helical spindle drives so as to distribute the tool force between the two drive motors, with each spindle drive bearing only a portion of the tool force.  
         [0015]     In still another example, there is provided a machine for processing workpieces, the machine including a spindle drive having a first spindle drive unit and a second spindle drive unit, a force introduction element coupled to the first spindle drive unit and the second spindle drive unit, and a force transmission element configured to transmit a force associated with a processing tool to the force introduction element, wherein the force introduction element is configured to distribute the force between the first spindle drive unit and the second spindle drive unit. 
     
    
     DESCRIPTION OF DRAWINGS  
       [0016]     The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.  
         [0017]      FIG. 1  shows a punching machine having a first construction of an electric lifting drive for a punch upper die in partially sectional side view;  
         [0018]      FIG. 2  shows the lifting drive in  FIG. 1  in longitudinal section;  
         [0019]      FIG. 3  shows a second construction of an electric lifting drive for a punch upper die of a punching machine in longitudinal section;  
         [0020]      FIG. 4  shows a third construction of an electric lifting drive for a punch upper die of a punching machine in longitudinal section;  
         [0021]      FIG. 5  shows a fourth construction of an electric lifting drive for a punch upper die of a punching machine in longitudinal section; and  
         [0022]      FIG. 6  shows a fifth construction of an electric lifting drive for a punch upper die of a punching machine in longitudinal section. 
     
    
       [0023]     Like reference symbols in the various drawings indicate like elements.  
       DETAILED DESCRIPTION  
       [0024]     As shown in  FIG. 1 , a punching machine  1  has a C-shaped machine frame  2  with an upper frame member  3  and a lower frame member  4 . An electric lifting drive  5  for a processing tool in the form of a punch  6  is provided at the fire end of the upper frame member  3 . The punch  6  is mounted in a tool bearing  7 . By means of the lifting drive  5  the tool bearing  7  is movable in a straight line jointly with the punch  6  in the direction of a lifting axis  8 . In a modified mode of operation, the lifting drive  5  can also be used as rotary drive and then serves for rotary adjustment of the punch  6  about the lifting axis  8  in the direction of a double arrow  9 . Movements in the direction of the lifting axis  8  are performed by the punch  6  during working strokes for machining workpieces and during return strokes following the working strokes. Rotary adjustment is performed to change the rotated position of the punch  6  relative to the lifting axis  8 .  
         [0025]     When machining a workpiece, in the example case when punching sheets (not shown), the punch  6  co-operates with a punch lower tool (not shown) in the form of a die. This is integrated in the customary manner in a workpiece table  10 , which in its turn is mounted on the lower frame member  4  of the punching machine  1 . The relative movements of the relevant sheet that are required during machining of the workpiece relative to the punch  6  and the die are performed by a coordinate guide  12  housed in a gap area  11  of the machine frame  2 .  
         [0026]     As can be inferred in detail from  FIG. 2 , the lifting drive  5  of the punching machine  1  includes a spindle transmission  13  with drive units  14 ,  15 . The drive unit  14  includes a drive spindle  16  and a spindle nut  17  located thereon, and the drive unit  15  includes a drive spindle  18  and a spindle nut  19  located thereon. In one configuration, the drive spindles  16  and  18  may be helical drive spindles (as illustrated). The drive spindle  16  and the spindle nut  17  are connected with one another by way of a thread engagement  20 , and drive spindle  18  and the spindle nut  19  are connected with one another by way of a thread engagement  21 . The two drive units  14 ,  15  are designed to work in opposite directions, but are otherwise of identical construction. In one configuration, the two drive units  14 ,  15  are ball screw transmissions.  
         [0027]     Electric drive motors  22 ,  23 , in the example shown torque motors, are provided for the powered drive of the spindle transmission  13 . A stator  24  of the drive motor  22  and a stator  25  of the drive motor  23  are mounted on a drive housing  26 . A rotor  27  of the drive motor  22  may be gearlessly connected to the spindle nut  17  of the drive unit  14 . Correspondingly, the spindle nut  19  of the drive unit  15  may be fixed to a rotor  28  of the drive motor  23 . By virtue of the mutual axial overlap of the spindle nuts  17 ,  19  on the one hand and of the components of the drive motors  22 ,  23  on the other hand, a comparatively small overall installed size for the general arrangement can be achieved.  
         [0028]     In one configuration, the drive spindles  16 ,  18  of the drive units  14 ,  15  are in the form of hollow spindles that are connected with one another by way of a common force introduction element  29  to form a one-piece modular unit. Inside, the drive spindle  16  receives a ram  30 , which serves as force transmission element. At one axial end the ram  30  is provided with the tool bearing  7  and via this with the punch  6 . In this region, the ram  30  is supported at the drive housing  26  in the radial direction by way of a bearing bush  39 .  
         [0029]     With its opposite axial end, the ram  30  lies against a force transfer element, such as force introduction element  29 . Over the remaining axial length of the drive spindle  16 , there is no connection between his and the ram  30 . On the contrary, a gap  40  of annular cross-section, visible in outline in  FIG. 2 , remains in this region between the inner wall of the drive spindle  16  and the outer wall of the ram  30 .  
         [0030]     In one configuration, for punching workpieces, the spindle nuts  17 ,  19  of the drive units  14 ,  15  are driven by the drive motors  22 ,  23  with opposite directions of rotation and at corresponding speeds about the spindle transmission axis  31  coincident with the lifting axis  8 . Owing to the opposite directions of rotation and the corresponding speeds of the spindle nuts  17 ,  19 , the drive spindles  16 ,  18  connected to one another in one piece are not entrained by either of the spindle nuts  17 ,  19  in the direction of rotation. The drive spindles  16 ,  18  and with them the tool bearing  7  and the punch  6  do not change their rotated position relative to the lifting axis  8 , (i.e., the spindle transmission axis  31 ). On the contrary, owing to the oppositely directed but same-speed rotary movements of the spindle nuts  17 ,  19 , the drive spindles  16 ,  18  and the tool bearing  7  and the punch  6  are displaced in the direction of the lifting axis  8 . In the process, the punch  6  is lowered onto the workpiece to be processed.  
         [0031]     As the punch  6  runs onto the workpiece to be processed, and during the following punching operation, a force that acts at any rate in the direction of the lifting axis  8  and the spindle transmission axis  31  builds up at the punch  6 . Over and above that, a force action in the transverse direction with respect to the spindle transmission axis  31  may also occur. Via the ram  30 , both of these forces that have build up at the punch  6  in the direction of the lifting axis  8  and spindle transmission axis  31  as well as any effective transverse forces are removed into the force introduction element  29 , which is arranged between the thread engagements  20 ,  21  of drive spindle  16  and spindle nut  17  on the one hand and drive spindle  18  and spindle nut  19  on the other hand. These forces may be hereafter referred to as the “tool force” or “tool forces.” As the tool forces that have built up at the punch  6  transversely to the lifting axis  8  and the spindle transmission axis  31  are transmitted, the ram  30  may act like a two-arm lever. The “center of rotation” of this two-arm lever is defined by the bearing bush  39 . On the tool side, the ram  30  has a comparatively short lever arm and towards the force introduction element  29  a comparatively long lever arm. Accordingly, even large transverse forces at the punch  6  result in comparatively small transverse forces at the force introduction element  29 .  
         [0032]     From the force introduction element  29 , all forces introduced therein are distributed uniformly to the two drive units  14 ,  15 . Each of the drive units  14 ,  15  and each of the thread engagements  20 ,  21  consequently has to accommodate approximately half of the forces that have built up at the punch  6 . In the direction of the flow of force, the drive spindles  16 ,  18  are provided as the spindle transmission elements close to the workpiece and the spindle nuts  17 ,  19  as the spindle transmission elements remote from the workpiece.  
         [0033]     Following each one of the punch strokes, the punch  6  has to perform a reverse stroke. For that purpose, the direction of rotation of the spindle nuts  17 ,  19  is reversed by means of a drive control  32 . The spindle nuts  17 ,  19  now rotating opposite to their direction of rotation during the preceding punch stroke but still in opposite directions. The drive spindles  16 ,  18  and the punch  6  connected thereto via the ram  30  are then retracted with respect to the workpiece. For rotary adjustment of the punch  6  about the lifting axis  8 , the spindle nuts  17 ,  19  can be operated in a corresponding direction of rotation. In the process, the spindle nuts  17 ,  19  entrain the drive spindles  16 ,  18  in the direction of rotation and with them the punch  6  without axial displacement of the punch  6 .  
         [0034]     In one set up, the rotary adjustment of the punch  6  is also controlled by the drive control  32 . Sensor arrangements  33 ,  34 ,  35  and an evaluation and control unit  36  are parts of the drive control  32 . The sensor arrangement  33  serves to monitor the angle of rotation and direction of rotation of the punch  6 , the sensor arrangement  34  serves to monitor the angle of rotation and speed and direction of rotation of the spindle nut  17 , and the sensor device  35  serves to monitor the angle of rotation and speed and direction of rotation of the spindle nut  19 . On the basis of the information obtained by means of the sensor arrangements  33 ,  34 ,  35 , the evaluation and control unit  36  controls the drive motors  22 ,  23 .  
         [0035]     In still other embodiments, the superimposition of an axial and a rotary movement of the drive spindles  16 ,  18  and of the punch  6  is also possible. For that purpose, the spindle nuts  17 ,  19  are to be driven in opposite directions of rotation and at different speeds.  
         [0036]     A lifting drive  45  as shown in  FIG. 3  has a spindle transmission  53  with drive units  54 ,  55 . The drive unit  54  includes a drive spindle  56  and a spindle nut  57  and the drive unit  55  includes a drive spindle  58  and a spindle nut  59 . In one configuration, the drive spindles  56  and  58  may be helical drive spindles (as illustrated). The drive spindles  56 ,  58  are also in the form of hollow spindles. Between the drive spindle  56  and the spindle nut  57 , there is a thread engagement  60 , between the drive spindle  58  and the spindle nut  59  there is a thread engagement  61 . A force transmission element in the form of a ram  70  is arranged inside the drive spindle  56 . At its workpiece-side axial end, the ram  70  is provided with the tool bearing  7  and the punch  6 . At its opposite axial end, the ram  70  is provided in one piece with a force transfer element, such as the force introduction element  69  widened radially to form an external collar. An axial extension  77  adjoins the force introduction element  69  in the direction of the spindle transmission axis  31 .  
         [0037]     The drive spindle  56  rests on the ram  70  without a connection to the ram  70  in the direction of the spindle transmission axis  31 . Correspondingly, the drive spindle  58  is arranged on the axial extension  77  of the ram  70 . The drive spindles  56 ,  58  are connected effectively in the axial direction exclusively with the force introduction element  69 . Fixing screws  78  that fix the drive spindles  56 ,  58  all-round to the force introduction element  69  are used for that purpose. In the transverse direction with respect to the spindle transmission axis  31 , the drive spindles  56 ,  58  rest with zero play against the ram  70  and the axial extension  77  respectively.  
         [0038]     In one configuration, the drive spindles  56 ,  58  constitute tool-side spindle transmission elements of the drive units  54 ,  55 , and the spindle nuts  57 ,  59  constitute spindle transmission elements of the drive units  54 ,  55  remote from the workpiece. Apart from the described variations, the lifting drive  45  according to  FIG. 3  is of identical construction with the lifting drive  5  shown in  FIG. 2 . The same reference numerals are used in  FIGS. 2 and 3  for corresponding components. However, unlike the situation according to  FIG. 2 , the force introduction element  69  of the lifting drive  45  according to  FIG. 3  effects only a uniform distribution of forces that have built up at the punch  6  in the direction of the lifting axis  8  and spindle transmission axis  31  to the drive units  54 ,  55  (e.g., the tooling forces). By virtue of the zero-play transverse support of the ram  70  and the axial extension  77 , transverse forces effective at the punch  6  are removed via the ram  70  into the drive spindle  56  and via the axial extension  77  into the drive spindle  58 .  
         [0039]      FIG. 4  shows another configuration of a lifting drive  85 , where drive spindles  96 ,  98  of drive units  94 ,  95  of a spindle transmission  93  are connected gearlessly to rotors  27 ,  28  of drive motors  22 ,  23 . In one configuration, the drive spindles  96  and  98  may be helical drive spindles (as illustrated). The drive spindles  96 ,  98  form spindle transmission elements of the drive units  94 ,  95  remote from the workpiece. Spindle nuts  97 ,  99  are provided as spindle transmission elements of the drive units  94 ,  95  close to the workpiece. These spindle nuts are mounted on a force transfer element, such as force introduction element  109  by fixing screws  118  and are therefore connected to the force introduction element  109  so as to transmit force. The force introduction element  109  is constructed in one piece with a ram  110  provided as force transmission element. The drive spindle  96  rests loosely on the ram  110 , i.e. without creating a force-fit connection or interlocking connection in the direction of the lifting axis  8  and spindle axis  31  and with clearance, indicated in  FIG. 4 , in the transverse direction of the lifting axis  8  and the spindle transmission axis  31 . A gap between the ram  110  and the drive spindle  96  is assigned the reference numeral  120 .  
         [0040]     The tool bearing  7  with the punch  6  is provided at the workpiece-side axial end of the ram  110 . Thread engagements between the drive spindles  96 ,  98  and the respective associated spindle nuts  97 ,  99  have been assigned the reference numerals  100 ,  101 . Otherwise, the same reference numerals as in the preceding Figures are also used in  FIG. 4 . Tool forces in the axial direction and in the transverse direction that have built up at the punch  6  are distributed via the force introduction element  109  to the drive units  94 ,  95 . As the transverse forces are removed, a bearing bush  119  acts as “center of rotation” for the ram  110  forming a two-arm lever.  
         [0041]     In another embodiment, there is provided a lifting drive  125  that includes a spindle transmission  133  with drive units  134 ,  135 . The lifting drive  125  shown in  FIG. 5  corresponds in its construction largely to the lifting drive  5  according to  FIG. 2 . Drive spindles  136 ,  138  in the form of hollow spindles support spindle nuts  137 ,  139  via thread engagements  140 ,  141 . In one configuration, the drive spindles  136  and  138  may be helical drive spindles (as illustrated). The drive spindles  136 ,  138  form spindle transmission elements of the drive units  134 ,  135  close to the workpiece and the spindle nuts  137 ,  139  form spindle transmission elements remote from the workpiece. The same reference numerals as in the preceding diagrams have also, as far as possible, been used in  FIG. 5 .  
         [0042]     However, unlike the conditions according to  FIG. 2 , in the case of the lifting drive  125  according to  FIG. 5 a  force transmission element in the form of a ram  150  is supported in the direction of the lifting axis  8  and spindle transmission axis  31  exclusively at the drive spindle  137 . Support of the ram  150  is affected by an external collar  151  mounted thereon, which engages radially in the drive spindle  136 . Otherwise, between the outer wall of the ram  150  and the inner wall of the drive spindle  136  there is a gap  160 , indicated in outline in  FIG. 5 .  
         [0043]     At its end remote from the punch  6  the ram  150  changes into a force transfer element, such as force introduction element  149 , which is widened radially relative to the ram  150  and lies with zero play against the inner wall of the transition region between the drive spindles  136 ,  138  transversely to the stroke direction  8  and the spindle transmission axis  31 . There is no connection effective in the axial direction between the force introduction element  149  and the drive spindles  136 ,  138 .  
         [0044]     By virtue of the described support of ram  150  and force introduction element  149 , the force introduction element  149  affects a uniform distribution to the drive units  134 ,  135  of tooling forces that have built up at the punch  6  transversely to the lifting axis  8 , but not of forces acting at the punch  6  in the direction of the lifting axis  8 . During removal of the transverse forces, a bearing bush  159  of the ram  150  acts as “center of rotation”.  
         [0045]     In a next construction, a lifting drive  165 , as shown in  FIG. 6 , corresponds in its construction largely to the lifting drive  5  according to  FIG. 2 . In addition to the components of the lifting drive  5 , the lifting drive  165  is equipped with an axial preloading arrangement  166 . The axial preloading arrangement  166  includes a plunger  167 , which at one end is connected at the common force introduction element  29  to the structural unit formed by the drive spindles  16 ,  18 . With its opposite axial end the plunger  167  passes through a piston  168 . The plunger  167  rests with a radial projection  169  on the piston  168 .  
         [0046]     The piston  168  is movably guided in the direction of the spindle transmission axis  31  in a cylindrical ring  170  provided on the drive housing  26 . The plunger  167  is rotatable about its longitudinal axis relative to the piston  168 . A pressure space  171  formed between the piston  168  and the drive housing  26  and the cylindrical ring  170  respectively is filled with air and is sealed with respect to its surroundings by sealing elements  172 .  
         [0047]     During punching of workpieces, the structural unit including drive spindle  16  and drive spindle  18  moves downwards in the direction of the lifting axis  8  and spindle transmission axis  31 . The plunger  167  connected to the drive spindles  16 ,  18  performs a movement in the same direction and entrains the piston  168  with it. The air in the pressure space  171  is consequently compressed. Via the piston  168  and the plunger  167 , the compressed air in the pressure space  171  exerts a force directed upwardly in the direction of the lifting axis  8  and the spindle transmission axis  31  on the drive spindles  16 ,  18  and via these on the tool bearing  7  and the punch  6 .  
         [0048]     When the workpiece to be processed is subjected to the action of the punch  6 , a force likewise directed upwardly in the direction of the lifting axis  8  and the spindle transmission axis  31  builds up in the components of the lifting drive  165  connected to the punch  6 . When the punch  6  penetrates the workpiece, then the punch  6  and the components of the lifting drive  165  connected to it attempt to perform a sudden movement directed downwardly in the direction of the lifting axis  8  and the spindle transmission axis  31 . Such a sudden movement is prevented by the preload force exerted by the axial preloading arrangement  166 , specifically by the pressure space  171 . The command of control and regulation of the operating state of the lifting drive  165 , that operating state being characterized by an extreme load alternation when the workpiece being processed is penetrated by the punch  6 , is thereby simplified. In another configuration, instead of the sealed pressure space  171 , a different pressure space is possible, which is connected to a pressure control arrangement. Furthermore, an alternative to air used in the example case shown, other pressure media, preferably of a gaseous nature, are possible.  
         [0049]     Additional description of one or more of the features described above may be provided in commonly assigned U.S. patent application Ser. No. ______, entitled PUNCH TOOL LIFT SPINDLE, filed Nov. 27, 2006 (Our Ref.: 15540-099001), and/or commonly assigned U.S. patent application Ser. No. ______, entitled COUNTER-ROTATING SPINDLE TRANSMISSION, filed Nov. 27, 2006 (Our Ref.: 15540-101001). Both of these applications are hereby incorporated by reference.  
         [0050]     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. For example, in some other embodiments, other suitable motors or transmissions may be employed. Accordingly, other embodiments are within the scope of the following claims.