Abstract:
The present invention relates to a device on a press and to a method for incrementally conveying workpieces in a longitudinal direction from a receiving station through at least one tooling station of the press with the aid of conveying means for the workpieces, which conveying means are moved back and forth in cycles and in synchrony with the movement of the press in the longitudinal direction, as well as in a transverse direction substantially perpendicular thereto in order to grip or release the workpieces. The conveying means are here moved in the longitudinal direction by means of an external drive unit which is merely synchronized with the movement of the press. The motor-powered external drive unit is mechanically coupled to the conveying means in such a way that the conveying means can be moved back and forth without reversing the rotation of the external drive unit.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a device on a press and to a method for incrementally conveying workpieces in a longitudinal direction from a receiving station through at least one tooling station of the press with the aid of conveying means for the workpieces, which conveying means are moved back and forth in cycles and in synchrony with the movement of the press in the longitudinal direction, as well as in a transverse direction substantially perpendicular thereto in order to grip or release the workpieces. The conveying means are moved in the longitudinal direction by means of an external drive unit, which is merely synchronized with the movement of the press. Transfer devices are characterized, relative to so-called follow-on composite tools, in that the part to be formed in the press, in the region of the receiving station, is firstly separated, for example from a continuous strip, for example by cutting-off or punching, and is then conveyed, independently of the movement of the continuous strip and generally also perpendicularly to the latter, through the at least one tooling station of the press. Usually, the press is provided with a plurality of tooling stations and forming stages connected in series. In the case of the follow-on composite tools, on the other hand, the part to be formed is conveyed from forming stage to forming stage by the specific continuous strip from which it stems.  
         [0002]     Basically, for the longitudinal drive of transfer systems, two drive systems enter into the reckoning.  
         [0003]     Firstly, the purely mechanical drive can be cited. The transfer is here mechanically driven by means of a gear comprising a worm gear and a lever, the gear being driven directly from the eccentric shaft of the press via a toothed belt, a chain or a shaft. Typical cycle angles in respect of these mechanical gears are: 120° for the feed angle; 60° for the dwell angle after the feed; 120° for the return stroke angle; and 60° for the dwell angle after the return stroke.  
         [0004]     Alternatively, the drive via a controlled external system (e.g. servo motor or linear motor) can be cited. The longitudinal movement is here driven by means of a rotor of a servo motor, which drives a system which generates the longitudinal movement (toothed belt with longitudinal guides or threaded roller spindle with longitudinal guides). The longitudinal movement can alternatively also be generated directly by a linear motor.  
         [0005]     If a comparison is made between these two basic approaches, then the following advantages and disadvantages can be listed.  
         [0006]     Advantages of mechanical drive include: motional sequence proceeds in accordance with the predefined mathematical formula which is portrayed in the form of the worm gear; high accelerations can be realized (up to 25 g); no lag errors occur; the motional sequence proceeds at all times synchronously to the press movement; and there is no danger of collision with the tool, since the moved subassemblies are mechanically coupled. Disadvantages of mechanical drive include: the motional sequence (feed cycle) cannot be altered; a complex design is required for the drive from the press to the gear; the positioning of the gear is predetermined by the downforce of the press; and the feed path is fixed. Advantages of servo drive include: the feed cycle can be flexibly chosen (using software); attachment to the press is flexible; various cycles can be run on the press; and the feed path can be altered. Disadvantages of servo drive include: the acceleration is limited; lag errors and overshoots can occur during the motional sequence; the number of cycles is limited; the mass to be moved limited in relation to the stroke rate and feed; the drive can break down; and in order for the servo motor to be able to move its own mass, it already requires a relatively large amount of energy.  
         [0007]     A mechanical transfer device similar to the said type and having a pair of transfer bars as conveying means for the workpieces is known, for example, from EP 0 490 821 A1. There, the transfer bars are driven by mechanical coupling with moved parts of the press, to be precise in the longitudinal direction by tapping off the movement of the eccentric shaft of the press via a gear and in the transverse direction by tapping off the movement of the ram of the press by means of control rails, whereby high stroke rates in the region of 300 cycles per minute can be realized. For specific applications in the cans field, up to 700 cycles per minute can even be reached. As a result of the mechanical coupling, collisions of the press tool with the conveying means can also very largely be prevented.  
         [0008]     Fundamentally similar devices are known from EP 0 504 098 A1 and EP 0 694 350 A1, though here a further vertical movement is superimposed upon the transfer bars and the workpieces.  
         [0009]     In addition thereto, transfer devices are known in which the conveying means are driven by means of one or more external drive units using servo motors, hydraulics, pneumatics, linear motors, etc., and which in a wide variety of ways are synchronized with the movement of the press ram by signaling means. Such external drive units are generally cheaper and also more flexible to use than the aforementioned mechanical couplings, though they do not allow such high stroke rates to be reached. Here the limit currently lies at around 50-150 cycles per minute. Should a drive break down, there is also the danger of a collision between the press tool and the conveying means, with generally destructive consequences.  
         [0010]     A further possible approach is described by WO-A-00/20305. Here there is described a device for incrementally conveying workpieces in a longitudinal direction from a receiving station through at least one tooling station of a press with the aid of conveying means for the workpieces, which conveying means are moved back and forth in cycles and in synchrony with the movement of the ram of the press in the longitudinal direction, as well as in a transverse direction substantially perpendicular thereto in order to grip or release the workpieces. The conveying means are in this case driven in the longitudinal direction by means of an external drive unit, which is synchronized with the eccentric shaft of the press purely by signaling means. By contrast, the movement of the conveying means in the transverse direction for the release of the workpieces is derived from the movement of the press ram by direct mechanical coupling. As a result of this drive type, the advantages of the purely mechanical drives in terms of safety and high cycle rates are achieved in combination with the cost effectiveness and greater flexibility of external drive units. The drawback with this is however that, in comparison to a purely mechanical longitudinal movement, because of the use of the servo motor, only relatively low cycle rates substantially below 300, or even just 250 strokes/minute are possible.  
       SUMMARY OF THE INVENTION  
       [0011]     One object of the invention is consequently to propose an improved device on a press for incrementally conveying of workpieces, which in particular allows high cycle rates within the realm of those of purely mechanical longitudinal movements and which nevertheless, on the other hand, has the flexibility of devices using external drive units. In particular, it is here a question of a device on a press for incrementally conveying workpieces in a longitudinal direction from a receiving station through at least one tooling station of the press with the aid of conveying means for the workpieces, which conveying means are moved back and forth in cycles and in synchrony with the movement of the press in the longitudinal direction, as well as in a transverse direction substantially perpendicular thereto in order to grip or release the workpieces, the conveying means being moved in the longitudinal direction by means of an external drive unit, which is merely synchronized with the movement of the press.  
         [0012]     This object is achieved in that the motor-powered external drive unit is mechanically coupled to the conveying means in such a way that the conveying means can be moved back and forth without reversing the rotation of the external drive unit.  
         [0013]     Typically, if external drive units are used, especially in the case of servo motors, a fundamental problem consists in the fact that the achievable accelerations and stroke rates, respectively, are limited due to the forward and return movement which has to be induced. Indeed, this back and forth movement calls for a rapid deceleration and acceleration, respectively, of the servo motor (stop and go), and since typically, in a device of this type, large moved masses are present, then the possible accelerations are thus limited in comparison to purely mechanical solutions. One heart of the invention thus consists in providing a mechanical coupling of the motor-powered external drive unit to the conveying means, which coupling allows the external drive unit to be operated without reversing the rotation and thus allows the otherwise necessary accelerations to be avoided, reduced or placed into sections where few masses are accelerated. The actual reversing rotation is here produced by an appropriate mechanical gear, which converts the back and forth movement, while the external drive unit, typically a servo motor, can be operated, for example, at a rotation speed which is constant in the feed operation and with constant direction of rotation. This design yields a large number of unexpected advantages, the advantages of a purely mechanical drive essentially being able to be combined with those of a pure external drive unit.  
         [0014]     A first preferred embodiment is accordingly characterized in that the mechanical coupling between external drive unit and conveying means is configured as a mechanical gear, especially, preferably, as a mechanical cam gear. The use of a worm gear is possible, for example.  
         [0015]     A further preferred embodiment is characterized in that the movement of the motor-powered external drive unit is synchronized by means of an incremental angle transducer with the movement of the press, especially with the movement of an eccentric shaft of the press. Through such a synchronization of external drive unit and press, stroke speeds can actually be achieved which are comparable with those of purely mechanical transfer devices.  
         [0016]     A particularly preferred embodiment of the present invention boasts means which allow the motor-powered external drive unit to be operated at different speeds in dependence on the feed cycle. This inherent flexibility of the external drive unit allows, inter alia, the feed angle to be changed, and hence taller structural parts to be formed in the press, without the need for mechanical conversions. In particular, the speed of the longitudinal movement of the conveying means thus becomes variable within certain limits, without mechanical alterations, purely by controlling the speed of the external drive unit; this specifically without reversing the direction of rotation of the servo motor as is necessary in the prior art, i.e. in the case of high cycle rates.  
         [0017]     A further preferred embodiment of the device according to the invention is characterized in that the movement of the conveying means in the transverse direction for the release of the workpieces is derived, by direct mechanical coupling, from the movement of the press. The movement of the conveying means for the grabbing of the workpieces in the transverse direction can likewise be effected by an external drive unit, where appropriate, analogously to the longitudinal drive, a combination of a motor-powered external drive unit with a mechanical gear also being possible, i.e. without reversing the direction of rotation of the external drive unit. This is, per se, a realization of the transverse drive which is intrinsically possible, i.e. where appropriate, also regardless of the design of the longitudinal drive, and which is new and inventive.  
         [0018]     A further preferred embodiment of the device is characterized in that the drive of the conveying means in the transverse direction for the release of the workpieces is derived, via a mechanical cam system, from the movement of the press ram. In addition, the conveying means preferably comprise transfer bars which extend in the longitudinal direction on both sides of the receiving station and of the at least one tooling station and which are preferably armed with grabs for the workpieces.  
         [0019]     Further preferred embodiments of the device according to the invention are described in the dependent claims.  
         [0020]     In addition, the present invention relates to a method for incrementally conveying workpieces on a press, particularly preferably using a device as has been described above. Here, the conveyance in a longitudinal direction from a receiving station through at least one tooling station of the press is ensured with conveying means for the workpieces, which conveying means are moved back and forth in cycles and in synchrony with the movement of the press in the longitudinal direction, as well as in a transverse direction substantially perpendicular thereto in order to grip or release the workpieces. Moreover, the conveying means are moved in the longitudinal direction by means of an external drive unit, which is merely synchronized with the movement of the press. According to the invention, the back and forth movement of the conveying means is here driven by the motor-powered external drive unit without reversing the rotation of the external drive unit; this, in particular, using a mechanical gear which generates a back and forth movement from the rotational movement of the external drive unit.  
         [0021]     A first preferred mode of operation is here characterized in that the motor-powered external drive unit is run at constant rotation speed and with constant direction of rotation. Typically, the cam characteristic of the gear is optimized for a constant operation of this type. Alternatively and particularly preferably, it is now possible, however, to operate a device as has been described above such that the motor-powered external drive unit is operated in dependence on the feed cycle at varying rotation speed yet with preferably constant direction of rotation. Thus, the flexibility of an external drive unit in the longitudinal direction is able to be combined with the high stroke rates of a purely mechanical transport in the longitudinal direction. Particularly preferably, the rotation speed of the external drive unit proceeds to be varied in those sections of the feed cycle in which the conveying means perform no longitudinal movement (so-called dwell sections). In the other sections, i.e. in the feed operation and in the return stroke, the rotation speed of the external drive unit is preferably kept constant, an increased, constant rotation speed preferably being operated, for example, in the feed operation. In those sections of the feed cycle in which the conveying means perform no longitudinal movement, the rotation speed is preferably initially slowed and then accelerated to the value which is relevant to the next section of the cycle. Thus, if optimal use is made of the cam characteristic of the gear (for example designed for constant speed of the external drive unit) with respect to running behavior at constant rotation speed of the external drive unit, the feed angle is able to be reduced. The variation of the rotation speed of the external drive unit in the dwell sections has the advantage, in particular, that practically no moved masses (apart from the shaft of the servo motor and of the worm gear and, where appropriate, a reduction gear) are present there and energy losses (deceleration) and high energy consumption (acceleration), respectively, can consequently be prevented. In this way, stroke rates of more than 200 strokes/min or more than 270 strokes/min, for example, can be achieved. Stroke rates in the region of or more than 300 strokes/min, or even in excess of 350 strokes/min, are typically possible. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]     The invention will be explained in greater detail below with reference to illustrative embodiments in connection with the drawings, in which:  
         [0023]      FIG. 1  shows a top view of the table of a press with a transfer device;  
         [0024]      FIG. 2  shows a front view of the press with parts of the transfer device;  
         [0025]      FIG. 3  shows a part-section along the line III-III in  FIG. 1  on larger scale;  
         [0026]      FIG. 4  shows a part of the longitudinal drive of the transfer device;  
         [0027]      FIG. 5  shows a diagrammatic representation of the feed cycle of a mechanical transfer gear;  
         [0028]      FIG. 6  shows a diagrammatic representation of the transfer system with variable feed time and with variable angles, respectively; and  
         [0029]      FIG. 7  shows a diagrammatic representation of the feed cycle of a transfer operation with variable angles. 
     
    
     DETAILED DESCRIPTION  
       [0030]      FIGS. 1 and 2  show more or less diagrammatically a press table  1 , guide pillars  2  and a press ram  3 . Usually, to the table  1  there is attached the bottom part and to the ram  3  the top part of a so-called transfer tool having a plurality of tooling and forming stations connected in series. For simplification purposes, this tool is not represented in the drawing. As conveying means for transporting the workpieces to be formed in the longitudinal direction through the individual forming stations, there is respectively located on either side of the tool a transfer bar  4  having grabs  5  (shown in purely diagrammatic representation) for the workpieces. The ends of the transfer bars are mounted by means of angle brackets  6  on longitudinal slides  7 . The longitudinal slides  7  ( FIG. 3 ) are guided rigidly along two parallel guide bars  8 , which, for their part, are fastened in a transverse slide  9  which is guided along two parallel transverse guide bars  10 .  
         [0031]     The transverse movement of the transfer bars  4  outward in the direction of opening is controlled by control rails  11 , which are fitted on the press ram  3  and act with their outer control cams  12  upon control rollers  13  of continuations  14  of the slides  9 . The continuations  14 , on the other hand, are acted upon by the piston rods  15  of pneumatic cylinders  16  in the reverse direction inward. A reliable contact pressure thus acts continuously in the direction of closing inward upon the continuations  14 , with the result that the control rollers  13  bear continuously also securely against the control cams  12  of the control rails  11 . From  FIGS. 2 and 3  it can be seen that, upon the downward movement of the control rails  11  with the press ram  3 , the control rollers  13  and the parts connected thereto, i.e. also the transfer bars  4 , are spread outward, so that a workpiece  17  clamped between two mutually opposing holders  5  is freed. The holders  5  are hereupon laterally removed from the region of the upper and lower tool parts of the press, with the result that the tool can close in order to work workpieces in all the stations.  
         [0032]     In  FIG. 1  it is indicated that, in a punching and receiving station, workpieces such as, for example, blanks  18  are punched out of a cross-traveling strip  19  and are taken up by the outermost grabs of the transfer bars  4 . In successive work cycles, the workpieces  18  are displaced incrementally to the left and are thus fed one after the other to the individual forming stations of the transfer tool. After a certain lead time, all the forming stations are occupied by a respective workpiece  18 . For each work cycle, the transfer bars  4  perform a closed right-angled movement in that they, in a first cycle, feed a number of gripped blanks to the next forming station of the transfer tool, in a second cycle are removed laterally outward from the workpieces and out of the region of overlap with the tool, in a third cycle are guided back in the longitudinal direction and in a fourth cycle are moved back inward toward the tool in order to grip the workpieces (cf. also  FIG. 5  in this regard, comments further below).  
         [0033]     The longitudinal drive of the transfer bars  4  comprises two leaf springs  20 , which are fastened by their right-hand ends to the inner side of the longitudinal slides  7  and which, as indicated in  FIG. 4 , can follow the transverse movements of the transfer bars  4 . At their left-hand end, the two leaf springs  20  are connected to a guide slide  21  which is movable back and forth in the longitudinal direction and is driven by an electric servo motor  23  via a toothed belt  22 . The servo motor  23  is subjected to a control signal  24 , which, with a rotary angle transducer (not represented), is derived from the movement of the eccentric shaft of the press and.  
         [0034]     According to the invention, the advantages of a mechanical gear now proceed to be combined with the advantages of a servo drive, in that an external drive unit, i.e. a servo motor, via a mechanical gear, is used to generate the longitudinal drive. To a certain extent, the mechanical gear here takes on the task of generating a thrust reversal from the rotation of the motor, without the direction of rotation having to be changed.  
         [0035]     In the case of a mechanical gear, 4 sectors normally exist (cf  FIG. 5  in this regard) including:  
         [0036]     a feed sector  25  for conveying the forming part from one tool stage to the next; a dwell sector  26  for delivering the forming part from the transfer system to the forming tool; a return stroke sector  27  for returning the grab rails into the starting position; and a dwell sector  28  for delivering the forming part from the tool to the grab rails.  
         [0037]     Typically, the angles of the 4 sectors can be assumed to be as follows: 120° for the feed sector  25 , 60° for the dwell sector  26 , 120° for the return stroke sector  27 , and 60° for the dwell sector  28 .  
         [0038]     In the arrangement of these angles, the feed angle  25 , above all, is critical. In this sector, the forming part has to be conveyed and it must neither fall out of the grabs during the movement, nor be displaced therein.  
         [0039]     Moreover, the size of the angle is crucial to determining the available effective height at which forming parts can still be formed. In  FIG. 5 , this height, the theoretical usable height, is represented with the reference symbol  30 , and the total height, the press stroke, with the reference symbol  29 . The press stroke is fixed for a given arrangement.  
         [0040]     The greater is the angle, the smaller must be the parts which are formed. In the case of a purely mechanical coupling of press stroke and longitudinal, as well as lateral movement, both the press stroke  29  and the theoretically usable height  30  are non-adjustable.  
         [0041]     A further relationship consists in the number of cycles of the press in connection to the feed angle. The smaller is the angle, the lower are the numbers of cycles which must be operated, since otherwise the acceleration in the feed sector becomes excessive (mechanically, accelerations up to 25 g are possible). In the case of a transfer system with traditional servo drive, the motor must in the movement sectors repeatedly be accelerated from zero to max. speed and be slowed from max. speed to zero upon braking.  
         [0042]     If the 2 types of drive for transfer systems are now combined in the manner according to the invention, then the following approach is formulated (cf.  FIG. 6  in this regard):  
         [0043]     A servo motor  35  with variable rev speed and incremental angle transducer drives a mechanical cam gear  38 , in which the sectors are designed according to optimal viewpoints for a maximum number of cycles of the press. This optimization is generally designed for constant speed of the motor. Between servo motor  35  and cam gear  38 , there can also here be disposed a reduction gear  36 . The servo motor  35  is an electric motor which can be switched, i.e. the output of which is controllable. For example, a servo motor  35  with 3000 rpm can be used, and a reduction gear  36  with a factor 1:10; so that a rotation of 300 rpm is found at the transfer gear  38 .  
         [0044]     The servo motor  35  is synchronized via a control system from an incremental angle transducer  32 , which is driven by the eccentric shaft of the press  31 . In order that the synchronization is ensured, the servo motor  35  likewise possesses an incremental angle transducer.  
         [0045]     The incremental angle transducer is an electronic subassembly which is capable of dividing a 360° rotation of a shaft (for example eccentric shaft of the press) into increments of, for example, 0.0440 and of precisely calculating the respective angular position of the eccentric shaft.  
         [0046]     The transfer gear  38  comprises a worm gear  37 , which, from the rotary movement of the servo motor  35 , generates a longitudinal movement. This longitudinal movement is transmitted via a feed lever  34  to the transfer bars  4 .  
         [0047]     If it is now operated at maximum number of cycles, according to the interpretation of the curve law of the transfer gear  38 , then the servo motor  35  runs with constant rotation precisely corresponding to the rotation of the eccentric shaft of the press  31 .  
         [0048]     In this operating mode, the system runs exactly the same as if the gear  38  were driven directly by the eccentric shaft of the press  31 .  
         [0049]     If it is now wished to exploit the advantages of the servo motor  35 , then the rev speed of the motor  35  in the individual cam sectors can be altered. Given a fixed feed path  33 , therefore, a variable feed time can be allowed. This is represented diagrammatically, analogously to  FIG. 5 , in  FIG. 7 . If the gear runs at the same rev speed as the press, then the feed time corresponds to the arranged feed angle (situation of  FIG. 5 ). If the gear in the feed angle range  25  and  40 , respectively, runs faster than the press, then the time shortens and the feed angle becomes smaller in virtual terms. The usable height for the forming of the parts (arrow  30  in  FIG. 5 ) is thereby increased. It should be borne in mind that the usable height for the forming of the parts constitutes at least twice the height of the part to be formed, and that typically at least one-third must be allowed for the conveyance. In the region of the dwell zones  26 ,  28 , the rev speed of the servo motor  35  can be altered.  
         [0050]     Should the feed angle  40  be reduced, then the motor  35 , within the dwell section  43  of the worm gear  37  (no longitudinal movement of the transfer), can be upped in speed. The feed angle  40  will in this case run through in a shorter time and the angle becomes smaller in virtual terms. In the case of the next sector (delivery of the forming part to the tool), the motor  35  can be retarded again in such a way that, at latest upon entry into the return stroke, it again runs synchronously to the press  31 .  
         [0051]     Accordingly, the result is, for example, the motional sequence with different time intervals which is represented in  FIG. 7 . In the starting position the press runs, for example, with a nominal speed of 300 strokes/min. The mechanical stepping gear  38  is designed for the standard angles 120°/60°/120°/60°. The feed cycle (time) is reduced relative to the standard time by, for example, 50% (virtual feed angle=60°).  
         [0052]     In the motional sequence, the following sections and points, respectively, pass through: 1) the press is started in the upper dead center  39  of the press and after a short time reaches its nominal speed. The transfer feed here still covers half the feed path  33 ; 2) in pos. A, the feed is idle, while the press continues running at constant speed. In this position, the grabs are closed. Upon passing into the region, the grabs detach themselves as soon as the tool of the press has sufficiently clamped the part to be processed; 3) in region B, the servo motor  35  reduces its speed (to below the speed of the press); 4) in region C, the servo motor  35  increases its speed to the nominal speed of the press; 5) in pos. D, the transfer feed begins its return stroke  42  and returns into its end position Pos. E at the same speed as the press. In the region  42 , the actual work of the tool takes place. Accordingly, the grabs close back around the ready-worked part only once position E is reached; 6) in region F, the servo motor  35  reduces its speed (to below the speed of the press) (N.B. the speed of the servo motor can be reduced, in the extreme case, to zero);  
         [0053]     7) in region G, the servo motor  35  increases its speed (to above the speed of the press); and 8) in pos. H, the transfer feed  40  starts. In this case, the region between pos. H and A is passed through, in relation to the press speed, with increased speed of the transfer gear (e.g. double speed in the present example).  
         [0054]     As a result of the change in speed of the servo motor  35  relative to the press speed, the cycle times of the transfer system are able to be individually adjusted.  
         [0055]     Theoretically, it is also possible to rotate the entire motional cycle of the transfer gear. (e.g. return stroke is in the dead center point  39 , feed is displaced 180°).  
         [0056]     It should be noted that, at each of the points A, D, E and H, both the angle and the speed must assume a certain value. In the dwell phases  41  and  43 , therefore, both deceleration and acceleration take place.  
         [0057]     In summary it can be stated that, through the combination of a mechanical gear with a servo motor drive, the curve law of the gear can be changed to a certain extent. Thus, on the one hand, for example, taller parts can be worked, this somewhat less rapidly than in normal operation, yet without the need to convert the machine. In the case of shorter parts, correspondingly larger stroke rates can be realized, resulting in shorter spring travels of the tool.  
         [0058]     The system thus acquires the following advantages: all the advantages of the mechanical gear; all the advantages of the servo drive, except for the variable feed path; servo motor does not have to run in stop and go operation and hence requires less energy (typically, in comparison to a longitudinal drive with servo motor without worm gear, a servo motor with half the output can be used); the change in speed can be executed in the dwell sector of the worm gear; the output of the transfer system corresponds to that of a fully mechanical system; on a press with fixed stroke height, taller parts are able to be formed; the field of application of the press can be extended and yields a greater customer benefit; if the servo motor changes speed, it needs only to accelerate or retard its own mass (rotor) and the mass of the worm gear, since the mass of the transfer system which has linearly to be moved is located in the dwell sector; and the output of the transfer system can be raised by about 20 to 30% relative to a pure servo transfer.  
       REFERENCE SYMBOL LIST  
       [0059]    
       
         
               
               
             
           
               
                   
               
               
                   
               
             
             
               
                 1 
                 press table 
               
               
                 2 
                 guide pillars 
               
               
                 3 
                 press ram 
               
               
                 4 
                 transfer bar 
               
               
                 5 
                 grab for the workpieces 
               
               
                 6 
                 angle bracket 
               
               
                 7 
                 longitudinal slides 
               
               
                 8 
                 guide bars 
               
               
                 9 
                 transverse slides 
               
               
                 10 
                 transverse guide bars 
               
               
                 11 
                 control rails 
               
               
                 12 
                 control cams 
               
               
                 13 
                 control rollers 
               
               
                 14 
                 continuations 
               
               
                 15 
                 piston rods 
               
               
                 16 
                 pneumatic cylinders 
               
               
                 17 
                 clamped workpiece 
               
               
                 18 
                 blank 
               
               
                 19 
                 cross-traveling strip 
               
               
                 20 
                 leaf spring 
               
               
                 21 
                 guide slide 
               
               
                 22 
                 toothed belt 
               
               
                 23 
                 servo motor 
               
               
                 24 
                 control signal 
               
               
                 25 
                 feed (standard angle = 120°) 
               
               
                 26 
                 dwell (standard angle = 60°) 
               
               
                 27 
                 return stroke (standard angle = 120°) 
               
               
                 28 
                 dwell (standard angle = 60°) 
               
               
                 29 
                 press stroke, fixed 
               
               
                 30 
                 theoretically usable height for parts-forming 
               
               
                 31 
                 press 
               
               
                 32 
                 incremental angle transducer 
               
               
                 33 
                 feed path 
               
               
                 34 
                 feed lever 
               
               
                 35 
                 servo motor 
               
               
                 36 
                 reduction gear 
               
               
                 37 
                 worm gear 
               
               
                 38 
                 transfer gear 
               
               
                 39 
                 upper dead center of the press 
               
               
                 40 
                 feed 
               
               
                 41 
                 dwell 
               
               
                 42 
                 return stroke 
               
               
                 43 
                 dwell 
               
               
                 44 
                 rotation axis of feed lever