Patent Publication Number: US-2018029104-A1

Title: Stamping press arrangement

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a National Stage application of International Patent Application No. PCT/CH2015/000018, filed on Feb. 11, 2015, which is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to a stamping press arrangement as well as to a use of the stamping press arrangement according to the preambles of the independent claims. 
     BACKGROUND 
     A variety of components are manufactured by stamping presses in a particularly economic way and in large numbers. 
     A special field is the manufacturing of container lids with a push-in or a pull-off tab which can be opened without tools, also called EOE (Easy Open Can Ends) by the industry, for which manufacturing pre-fabricated metal sheet lids are provided in the stamping press, with different profiles, with a carving for the opening position as well as with a separately supplied push-in or a pull-off tab. 
     U.S. Pat. No. 4,166,424 discloses a stamping press for manufacturing EOEs, for which the prefabricated sheet metal lids are guided in two parallel rows through a bottom press part where they are stepwise reshaped, provided with a carving and provided subsequently with a pull-off tab. A top press part is located directly above the bottom press part, through which a metal strip is guided and during this time reformed stepwise asstrip carrying serially one after the other the pull-off tabs to be attached to the lids in the bottom press part. This strip is inserted into the bottom press part in a 180° arc in its transport direction in a reverse way and then perpendicular to the transport direction of the lids, where the pull-off tabs carried by it are separated from the strip and riveted with the lids. In case of the bottom press part, the bottom tool half is moved and works against the fixed top tool half while in case of the top press part the top tool half is moved and works against the fixed bottom tool part. The moved tool halves of the bottom and top press part are connected to one another via pull rods and are moved together up and down via a crank drive, such that the bottom press part acts during the upward movement and the top press part acts during the downward movement. This stamping press has the disadvantage that it is structurally weak and therefore only provides low precision as well as allows only comparatively slow stroke speeds. Additionally, the top press part, which produces the pull-off tabs, has mandatorily the same stroke like the bottom press part, which processes the lids, such that the influencing possibilities for optimizing the entire process are considerably restricted. 
     DE 36 27 179 A1 discloses a stamping press for manufacturing EOEs, in case of which the prefabricated sheet metal lids are guided in two parallel rows in longitudinal direction of the press through a first press half, where they are stepwise reshaped, provided with a carving and provided subsequently with a pull-off tab. The pull-off tabs are produced in the second press half and are attached to the lids in in the first press half. The lids are processed in the first press half with two press rams penetrating one another, which work downward against a press table which is solidary with the second press half. The second press half has an own press ram for manufacturing the pull-off tabs, which also works downward against the press table. All three press rams are driven by a common crank drive. This stamping press has the disadvantage that it has a complicated construction with three different press rams and that it is also structurally weak, such that also in this case it allows only a low precision as well as only comparatively slow stroke speeds. A particular disadvantage of this construction is additionally that deformations of the one press half due to stamping force and/or temperature have a strong influence on the respective other press half. 
     EP 0 281 777 A1 discloses a stamping press for manufacturing EOEs, in case of which the prefabricated sheet metal lids are guided in three parallel rows in longitudinal direction of the press through a first press, where they are stepwise reshaped, provided with a carving and provided subsequently with a pull-off tab. The pull-off tabs are produced in a second press which is synchronized with the first press and has a transport direction which is perpendicular to the transport direction of the first press, wherein the pull-off tabs are subsequently supplied directly to the first press and are attached to the lids there. This stamping press avoids some of the disadvantages of the stamping presses mentioned above, it has however still the disadvantage that the press ram of the first press is relatively big and accordingly massive, which leads to enormous component stress and a high energy consumption in case of high stroke speeds or significantly limits the potential for increasing the stroke speeds and consequently for increasing the productivity of the press, respectively. Additionally, due to the use of a common tool for three shell rows the problem results that the first press has to be operated with an enormous press load in order to ensure a precise carving depth for all three shell rows, thus requiring much energy and being prone to wear. 
     The publications WO 2014/144119 A1 and WO 2014/144284 A1 disclose a stamping press for manufacturing EOEs, in case of which the prefabricated sheet metal lids are stepwise reshaped in three parallel stamping press units with one row each, are provided with a carving and provided subsequently with a push-in or pull-off tab, respectively. In a further stamping press unit with a transport direction which runs perpendicularly to the transport direction of the three other press units, the push-in or pull-off tab, respectively, are manufactured of a sheet metal strip and subsequently supplied directly to the three mentioned press units, where they are attached to the lids. The press ram of the stamping press units work each downward against a machine table under which crank shafts, each running through the press units in transport direction of the lids, and connecting rods for transforming the rotational movement of the crank shaft in the up and down movement of the press ram, are arranged. The crank shafts of the four stamping press units are coupled to the main press drive via four angular gears and frictions arranged in between. This stamping press partially avoids the disadvantages of the above mentioned stamping press, however it has the disadvantage that it is constructed in a very complex way and has many wear-prone and energy consuming components, therefore having a negative influence on its energy efficiency, its life, its maintenance intensity and last but not least also on the attainable stroke speeds. 
     SUMMARY OF THE INVENTION 
     It is therefore the objective to provide a technical solution which doesn&#39;t have the above mentioned disadvantages of the prior art or at least partially avoids them. 
     This objective is reached by the stamping press arrangement according to the independent claims. 
     According to them, a first aspect of the invention relates to a stamping press arrangement with a plurality of stamping press units, preferably for manufacturing container lids with push-in or pull-off tabs which can be opened without tools. 
     The arrangement comprises at least two adjacent first stamping press units according to the claims, preferably with identical construction and size, each of which has a press ram for receiving and moving a first tool part which works against a receiving plate for receiving a corresponding second tool part. These first stamping press units are oriented with respect to one another in such a way that they have working directions extending parallel to each other and preferably have work planes located in a common plane. 
     Furthermore, the arrangement comprises at least a second stamping press unit according to the claims, having a press ram for receiving and moving a first tool part which works against a receiving plate for receiving a corresponding second tool part. 
     The working direction of this second stamping press unit extends perpendicularly to the working directions of the first stamping press units, in such a way that material pieces or material strips processed in a working space of the second stamping press unit can be guided in direct extension of the working direction of the second stamping press unit into working regions of the first stamping press units for further processing in the first stamping press units with material pieces or material strips supplied in working direction of the first stamping press units to the first stamping press units. For this, the work plane of the second stamping press unit is preferably located in a same plane with the work planes of the first stamping press units. 
     The first stamping press units have each a crankshaft portion or eccentric shaft portion, which is rotatable about a first rotation axis according to the claims, and which serves in interaction with at least an attributed connecting rod to generate a travel movement of the press ram of the respective stamping press unit for processing the material pieces and/or the material strips in the first stamping press units. The crankshaft portion or eccentric shaft portion of the first stamping press units are driven via a common driving unit, wherein their rotation axes are identical. They are connected or coupled to one another in such a way that they are rotated forcibly together with the same number of rotations. 
     The second stamping press unit also has a crankshaft portion or eccentric shaft portion which is rotatable with a driving unit about a second rotation axis according to the claims and which serves in interaction with at least an attributed connecting rod to generate a travel movement of the press ram of the second stamping press unit for processing the material pieces and/or the material strips in the second stamping press unit. The crankshaft portion or eccentric shaft portion of the second stamping press unit is coupled to the crankshaft portion or eccentric shaft portion of the first stamping press units in such a way, particularly by a rotational positive fit in both rotation directions, that its crankshaft portion or eccentric shaft portion is rotatable forcibly synchronously with the crankshaft portion or eccentric shaft portion of the first stamping press units, preferably with the same number of rotations. 
     In other words, the invention relates to a stamping press arrangement with multiple stamping press units arranged in an adjacent way, which have work directions running mutually parallel in a common plane, and with a second stamping press unit, the work direction of which is perpendicular to the work directions of the first stamping press units, such that material processed in this stamping press unit can be guided in direct extension of its work direction into work areas of the first stamping press units. The stamping press units have each a crankshaft portion or eccentric shaft portion, by means of which the stroke movement of the respective press ram is effected via a connecting rod. The crankshaft portions or eccentric shaft portions of the first stamping press units are driven forcibly together with the same number of rotations by a common driving unit and they have a common rotation axis. The crankshaft portion or eccentric shaft portion of the second stamping press unit is coupled to the crankshaft portions or eccentric shaft portions of the first stamping press units in such a way that it rotates forcibly synchronously with the latter. 
     The invention makes it possible to provide in an inexpensive way highly precise and fast stamping press arrangements for the economic large series production of low-tolerance multiple-part stamping and punching products, e.g. container lids with push-in or pull-off tabs (EOEs), which can be opened without tools. 
     Preferably, the rotation axis of the crankshaft portion or eccentric shaft portion of the second stamping press unit is parallel to the rotation axis of the crankshaft portions or eccentric shaft portions of the second stamping press units. It is particularly preferred that these rotation axes are identical. In this way, a simple and loss-free or low-loss, respectively, rotational coupling of the crankshaft portions or eccentric shaft portions is possible, e.g. by their rigid mutual connection or by their coupling via a positive fit coupling. 
     It is further advantageous that the first stamping press units have each a separate crankshaft portion or eccentric shaft portion and the crankshaft portions or eccentric shaft portions of the first stamping press units are coupled to one another by a rotational positive fit in both rotation directions, preferably such that they are radially and axially shiftable with respect to one another, wherein this is advantageously done by means of one or more Oldham-couplings. 
     It is also advantageous that the second stamping press unit has a separate crankshaft portion or eccentric shaft portion which is coupled to the crankshaft portion or eccentric shaft portion of one of the first stamping press units in the way described above. 
     Such an embodiment of the stamping press units make it possible to rule out a transfer of temperature-dependent and stamping-force-dependent deformation forces between the stamping press units via their crankshaft portion or eccentric shaft portion. 
     In a further preferred embodiment of the stamping press arrangement, each one of the first stamping press units has an own receiving plate which is separate from the other stamping press units. In this way it is possible to mechanically decouple from one another to a large extent the structures of the stamping press units in order to avoid a transfer of temperature-dependent and stamping-force-dependent deformation forces between its structures. 
     In another preferred embodiment, the receiving plates of the first stamping press unit are formed together, which allows a considerable cost advantage in case certain compromises in terms of precision have to be accepted. 
     Advantageously, the press rams of the stamping press units work each from the top against a receiving plate arranged below. Such concepts have the advantage that the material pieces or material strips to be processed lie on the bottom, fixed tool half due to the gravitational force, thereby simplifying material handling for many applications in contrast to other concepts. 
     If the crankshaft portions or eccentric shaft portions are each arranged above the press ram, which is preferred, the advantage results that particularly precise stamping press units are possible, because a minimization of the stamping-force-dependent bending of the press ram can be reached by a central force introduction into the press ram, and the actual press ram drive can be formed by very short and rigid components, thereby additionally leading to advantages with respect to the inert masses and thereby with respect to the feasible stamping frequencies. 
     In yet a further preferred embodiment of the stamping press arrangement according to the invention, it has multiple, preferably three or four first stamping press units according to the claims, arranged in an adjacent way, which are coupled to one another in a common self-carrying structure, preferably each one in sections of the stamping press units which are not charged by stamping forces. “Sections of the stamping press units which are not charged by stamping forces” are provided by components or component portions which do not experience dimension changes or deformation, respectively, due to the stamping force, in operation as intended. In this way, the individual stamping press units can be positioned in a precise way with respect to one another and they can be coupled to one another as a fixed unit. For the preferred case that the stamping press units are coupled to one another in an area which is substantially not charged by the stamping forces, the further advantage results that practically no deformations due to the stamping forces are transferred between the stamping press units. 
     In this context it is preferred that the two outer ones of the first stamping press units, which are coupled to one another in a common structure, are each coupled to a supporting structure via which the structure formed by the first stamping press units is supported on the floor. The connection with the supporting structure is preferably implemented in an area of the stamping press units, which is not charged by the stamping forces. 
     In this way it is possible to fix the height of the working planes of the stamping press units via the supporting structure and to use stamping press units in case of which the receiving plate is supported by a hanging supporting structure. 
     Advantageously, in case of this preferred embodiment of the stamping press arrangement, at least one of the supporting structures carries a second stamping press unit according to the claims on its side facing away from the mutually coupled first stamping press units. In this way, the at least one second stamping press unit can be positioned precisely with respect to the first stamping press units and it can be connected to them, thus forming a fixed unit. This also makes it possible to set the height of the working plane of the second stamping press unit via the supporting structure or to adjust it to the height of the working planes of the first stamping press units, respectively. Furthermore, in this way it is possible to use a second stamping press unit according to the claims, in case of which the receiving plate is carried by a hanging supporting structure. 
     A preferred configuration of this embodiment of the stamping press arrangement according to the invention has two groups of first stamping press units, preferably two groups of each three first stamping press units. These groups of first stamping press units are coupled to one another to a first common self-supporting structure (first group of first stamping press units), preferably each in an area of the respective stamping press units, which is substantially not charged by the stamping forces, and to a second common self-supporting structure (second group of first stamping press units). The first structure and the second structure are coupled to one another at their ends facing one another via a first supporting structure arranged between them, via which these two structures are each supported on the floor with this first end. At its other second end, the structures are each coupled to a further supporting structure, with the first stamping press unit arranged at this second end, via which the respective structure is supported on the floor at its second end. At least one of these further supporting structures carries a second stamping press unit according to the claims on its side which is opposed to the respective first or second structure, respectively, of mutually connected first stamping press units. Very large volumes can be produced with such “tandem arrangement”, wherein this configuration allows a simple supplying and discharging of material and products. 
     In order to keep wear and energy losses of the stamping press arrangement according to the invention as low as possible, it is further preferred that the driving unit for the first stamping press units according to the claims or the common driving unit for the first and second stamping press units, respectively, has no gears between its flywheel and the crankshaft portions or eccentric shaft portions. 
     It is further preferred that each one of the first stamping press units according to the claims has an own supply device for supplying individual material pieces into a working area of the respective stamping press unit, preferably a conveyor belt with holes for supplying metal blanks, e.g. metal can shell blanks. Such stamping press arrangements are particularly suitable for manufacturing container lids with press-in or pull tabs (EOEs) which can be opened without tools. 
     Advantageously, these supply devices are driven via the driving unit for the stamping press units, resulting in the simple implementation of a synchronous drive and in that additional drives are obsolete. 
     Preferably, no separable clutches are present between the supply devices and the driving unit, such that a forcibly synchronous coupling of the supply devices is present. 
     If the supply devices are integrated into the receiving plates of the first stamping press units according to the claims, which is preferred, they can be provided in a particularly space saving way. 
     In order to design the system concept of the stamping press arrangement according to the invention as robust and failsafe as possible and to reduce the effort with respect to technical implementation to a minimum, it is further advantageous that the stamping press arrangement only has precisely one flywheel, precisely one friction and precisely one brake in the drive train for the stamping press units. 
     In a further preferred embodiment of the stamping press arrangement, the first stamping press units and/or the at least one second stamping press unit have each precisely one connecting rod, by means of which the stamping force is introduced centrally into the respective press ram. This way of construction is advantageous particularly in case of short press rams, seen in transport direction, or in case of substantially central press ram load, respectively, because it has a simple and inexpensive drive mechanism with few moving parts. 
     In a further preferred embodiment of the stamping press arrangement, the first stamping press units and/or the at least one second stamping press unit have each two connecting rods, by means of which the stamping force is introduced symmetrically into the respective press ram. This way of construction is advantageous particularly in case of relatively long press rams, seen in transport direction, or in case of relatively asymmetric press ram load, respectively, because it increases the tilt resistance of the press ram. 
     It is further advantageous that each one of the stamping press units of the stamping press arrangement has an own mass compensation device. In this way, the dynamic forces acting towards the outside can be diminished or eliminated, respectively. 
     It is also advantageous that each one of the stamping press units of the stamping press arrangement is adjustable independently from the other stamping press units with respect to press ram stroke and/or closing height. In this way, the stamping press arrangement according to the invention provides a maximum of production flexibility and production precision. 
     A second aspect of the invention relates to the use of the stamping press arrangement according to the first aspect of the invention for manufacturing metal can lids with a push-in or a pull-off tab. The advantages of the invention are particularly evident in case of such use of the stamping press arrangement. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following the prior art and embodiments of the invention will be further explained by means of the figures. Thereby it is shown in: 
         FIG. 1  shows a front view of a first stamping press arrangement according to the invention; 
         FIG. 2  shows a side view of the first stamping press arrangement from the direction S of  FIG. 1 ; 
         FIG. 3  shows a horizontal section through the first stamping press arrangement along the line X-X of  FIG. 1 ; 
         FIG. 4  shows a partial vertical section through the first stamping press arrangement along the line X-Y of  FIG. 2 ; 
         FIG. 5  shows a vertical section through the first stamping press arrangement along the line Z-Z of  FIG. 4 ; 
         FIG. 6  shows a view like in  FIG. 5  of a variant of the first stamping press arrangement; and 
         FIG. 7  shows a front view of a second stamping press arrangement according to the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 and 2  show a first stamping press arrangement for manufacturing metal container lids with a push-in or a pull-off tab and which can be opened without tools, once in a front view ( FIG. 1 ) and once in a side view with viewing direction S from the left ( FIG. 2 ). 
     As can be seen by viewing together with  FIGS. 3 and 4 , which show a horizontal section along the line X-X of  FIG. 1  ( FIG. 3 ) and a partial vertical section along the line Y-Y of  FIG. 2  ( FIG. 4 ) through the press arrangement, the latter comprises three adjacent stamping presses  4   a ,  4   b ,  4   c  (three first stamping press units according to the invention), in the following called “conversion-presses”, by means of which prefabricated metal sheet lids are provides with different profiles, with a carving for the opening location as well as with an additionally supplied push-in or pull-off tab, respectively. The three conversion presses  4   a ,  4   b ,  4   c  are coupled to one another as common self-supporting structure  4   a - 4   c . The two outer conversion presses  4   a ,  4   c  of this structure  4   a - 4   c  are each coupled to a supporting structure  9 ,  11 ;  10 ,  11 , via which the structure  4   a - 4   c  formed by the three conversion presses  4   a ,  4   b ,  4   c  is supported on the floor. 
     The left supporting structure  9 ,  11  consists of a drive housing  9  and a supporting pillar  11 , and the right supporting structure  10 ,  11  consists of a supporting section  10  and a supporting pillar  11 . Said supporting structure  10 ,  11  carries a further stamping press  8  (second stamping press unit according to the claims) on its side which is opposed to the conversion presses  4   a ,  4   b ,  4   c , by means of which the push-in or the pull-off tabs, respectively, are manufactured from a strip material  22 . In the following, this press  8  is called “tab press”. 
     The three conversion presses  4   a ,  4   b ,  4   c  are oriented with respect to one another in such a way that they have mutually parallel working directions B and their working planes are in a same plane. 
     The tab press  8  is oriented with respect to the conversion press  4   a ,  4   b ,  4   c  in such a way that its working direction A runs perpendicular to the working directions B of the conversion presses  4   a ,  4   b ,  4   c  and its working plane lies in the same plane, where also the working planes of the conversion presses  4   a ,  4   b ,  4   c  are located. The working direction A of the tab press  8  intersects with the working directions B of the conversion presses  4   a ,  4   b ,  4   c  in the working direction of the conversion presses  4   a ,  4   b ,  4   c . The push-in or the pull-off tabs, respectively, formed in the working area of the tab press  8  by stamping and reshaping on a material strip  22 , are guided with the material strip  22  in direct extension of the working direction A of the tab press  8  in the working areas of the conversion presses  4   a ,  4   b ,  4   c , where each of them is detached from the material strip with the respective conversion press  4   a ,  4   b ,  4   c  and are riveted with the metal lids passing through the respective conversion press  4   a ,  4   b ,  4   c  in its working direction B. The transport of the material strip  22  in the working direction A of the tab press  8  through the presses  4   a ,  4   b ,  4   c  is done by means of an advancing device  23   a  at the input of the tab press  8  and a pulling device  23   b  at the output of the last conversion press, as seen in this direction A. 
     As it results particularly from  FIGS. 3 and 4  as seen together with  FIG. 5 , which shows a vertical section through the stamping press arrangement along the line Z-Z of  FIG. 4 , the conversion presses  4   a ,  4   b ,  4   c  comprise each a press ram  1   a ,  1   b ,  1   c  for receiving the moved top conversion tool half (not shown), which work from above against a receiving plate  2   a ,  3   a ;  2   b    3   b ;  2   c ,  3   c , which is separate from the other presses, for receiving the attributed fixed bottom conversion tool half (not shown). The press rams  1   a ,  1   b ,  1   c  are each guided as vertical shifting via four press ram guides  12 . 
     In the same way, the tab press  8  comprises a press ram  5  for receiving the moved top tab tool half (not shown), which works from above against a receiving plate  6 ,  7  for receiving the attributed fixed bottom tab tool half (not shown). The press ram  5  is also guided as vertical shifting via four press ram guides  21 . 
     The conversion presses  4   a ,  4   b ,  4   c  have each separately formed crank shafts  28   a ,  28   b ,  28   c  (crankshaft portions or eccentric shaft portions according to the claims), each of them being arranged above the respective press ram  1   a ,  1   b ,  1   c  and being coupled to the press ram  1   a ,  1   b ,  1   c  of the respective conversion press  4   a ,  4   b ,  4   c  via a single attributed connecting rod  29   a ,  29   b ,  29   c , for generating the stroke of the press ram  1   a ,  1   b ,  1   c  of this press. The stamping force is introduced into the press ram  1   a ,  1   b ,  1   c  with the connecting rod  29   a ,  29   b ,  29   c , in each case centrally via a height-adjustable thrust bearing  39 . 
     The tab press  8  also has a crank shaft  30  (crankshaft portion or eccentric shaft portion according to the claims), which is arranged above its press ram  5  and coupled to the press ram  5  via two connecting rods  31   a ,  31   b , for generating the stroke of the press ram  5  of this press  8 . The stamping force is introduced into the press ram  5  with the two connecting rods  31   a ,  31   b , symmetrically via two height-adjustable thrust bearings  39 . 
     The rotation axis R 2  of the crank shaft  30  of the tab press  8  and the rotation axis R 1  of the crank shafts  28   a ,  28   b ,  28   c  of the conversion presses  4   a ,  4   b ,  4   c  are identical. The cranks shafts  28   a ,  28   b ,  28   c ,  30  have a rotational positive fit in both rotation directions and are coupled to one another radially and mutually shiftable by means of Oldham-couplings  32 . They are driven via a common driving unit comprising an outer main drive motor  24 , a friction arrangement and a brake arrangement  34 ,  35  with a flywheel  33 , arranged inside the drive housing  9 , as well as a belt drive  25 ,  26  arranged at the drive housing  9  below a protecting cover  27 . No gears are arranged between the flywheel  33  and the crank shafts  28   a ,  28   b ,  28   c ,  30  of the presses  4   a ,  4   b ,  4   c ,  8 . 
     As particularly visible in  FIG. 3 , each conversion press  4   a ,  4   b ,  4   c  has an own supplying device  13 ,  14 ,  15 , integrated in its receiving plate, for supplying the metal shell blanks to their working area, each comprising a transfer system  13  and a transport band  15  with holes  16  for receiving the shell blanks. The transport band  15  extends between two deflection pulleys  14  through the respective conversion press  4   a ,  4   b ,  4   c . The deflections pulleys  14  at the output of the conversion presses  4   a ,  4   b ,  4   c  are each carried by an axle  17 , which is fixedly, with respect to rotation, connected to the respective deflection pulley  14  and which is supported via two bearing blocks  18  in a rotatable way on the structure of the respective conversion press  4   a ,  4   b ,  4   c . These axles  17  of the three conversion presses  4   a ,  4   b ,  4   c  are coupled to one another via two intermediary axles  19  in a rotational positive fitting way in both rotation directions and they are driven by a stepping gear  20  which is coupled to the crank shafts  28   a ,  28   b ,  28   c ,  30  of the presses  4   a ,  4   b ,  4   c ,  8  in a synchronous way with respect to rotation by means of two angle gears  20   a ,  20   c  and a joint shaft  20   b . No separable clutchess are present between the supplying devices  13 ,  14 ,  15 ,  16  and the driving unit  24 ,  25 ,  26 ,  33 ,  34 . 
     As it is further evident, each of the presses  4   a ,  4   b ,  4   c ,  8  has a compensation mass  36   a ,  36   b ,  36   c ,  37  which is moved up and down by means of further connecting rods arranged on the respective crank shaft  28   a ,  28   b ,  28   c ,  30  in an opposite direction to the respective press ram  1   a ,  1   b ,  1   c ,  5 , in order to reduce or eliminate, respectively, dynamic forces acting to the outside. 
       FIG. 6  shows a variant of the stamping press arrangement in a vertical section along the line Z-Z of  FIG. 4 . As can be seen, in case of the conversion presses  4   a ,  4   b ,  4   c  of this variant, the respective connecting rod  29   a ,  29   b ,  29   c  is coupled to the press ram  1   a ,  1   b ,  1   c  of the respective conversion press  4   a ,  4   b ,  4   c  via a lever mechanism, wherein the force introduction is done symmetrically via two pressure tongues  38 . 
       FIG. 7  shows a front view of a second stamping press arrangement according to the invention. It differs from the above mentioned first stamping press arrangement according to the invention only in that it comprises six adjacent conversion presses  4   d ,  4   e ,  4   f ;  4   g ,  4   h ,  4   i  (six first stamping press units according to the claims), by means of which prefabricated sheet metal shells are provided with different profiles, with a carving for the opening location as well as with a supplied push-in or pull-off tab, respectively. 
     These six conversion presses  4   d ,  4   e ,  4   f ,  4   g ,  4   h ,  4   i  form two groups of each three conversion presses  4   d ,  4   e ,  4   f ;  4   g ,  4   h ,  4   i , of which the first group  4   d ,  4   e ,  4  forms a first common self-supporting structure  4   d - 4   f  and the second group  4   g ,  4   h ,  4   i  forms a second common self-supporting structure  4   g - 4   i . The first structure  4   d - 4   f  and the second structure  4   g - 4   i  are connected to one another via a middle supporting structure  10   a ,  11   a  (first supporting structure according to the claims) arranged between them, which consists of a supporting portion  10  and a supporting pillar  11 , and they are supported on the floor by means of this supporting structure  10 ,  11 . 
     The first structure  4   d - 4   f  is connected at its left end with its outer conversion press  4   d  to a further supporting structure consisting of a drive housing  9  and a supporting pillar  11  and it is supported on the floor via this supporting structure  9 ,  11 . 
     The second structure  4   g - 4   i  is connected at its right end with its outer conversion press  4   i  to a further supporting structure consisting of a supporting portion  10  and a supporting pillar  11  and it is supported on the floor via this supporting structure  10 ,  11 . This supporting structure  10 ,  11  supports on its side which faces away from the conversion presses  4   g ,  4   h ,  4   i  a tab press  8  (second stamping press unit according to the claims), by means of which the push-in or pull-off tabs, respectively, are produced of a material strip. 
     The rest of the construction of this second stamping press arrangement according to the invention is identical to the one of the first stamping press arrangement. 
     While the present disclosure has been illustrated and described with respect to particular embodiments thereof, it should be appreciated by those of ordinary skill in the art that various modifications to this disclosure may be made without departing from the spirit and scope of the present disclosure.