Patent Publication Number: US-6662988-B2

Title: Apparatus for a stepwise feeding of a strip-shaped article

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority from the European Patent Application No. 01 124 281.5, filed on Oct. 18, 2001, of which the entire disclosure shall be considered to be included in the present application by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an apparatus for a stepwise feeding of a strip-shaped article. It also relates to twin feeding apparatuses for a stepwise feeding of at least one strip-shaped article and including two feeding apparatuses of the kind set forth above. 
     2. Description of the Prior Art 
     Such apparatuses are used for instance for a stepwise feeding of a metal strip to and through a press, specifically a punch press, in which punch press tools for processing such a metal strip for instance by punching, embossing, bending, riveting, and so on are installed. 
     The stepwise feeding of the strip-shaped article can proceed as is conventional by linearly oscillating gripper members or by oscillatingly rotating or intermittently rotating, resp. feeding rollers. 
     Depending from the product which is proceed in such punch presses, metal strips of various widths such as for instance in the range between about 20 Millimeters and 450 Millimeters are processed, and also simultaneously two such strips which are arranged side by side. 
     Accordingly, apparatuses for feeding such strips to and through a punch press must be of differing designs, depending from a respective strip or from respective strips which is or are, resp. to be processed so to be able to cope with the prevailing strip or strips, respectively. This results obviously in considerable production costs for a manufacturer because due a multitude of differently designed feeding apparatuses are needed. 
     SUMMARY OF THE INVENTION 
     Hence, it is a general object of the invention to provide an apparatus for a stepwise feeding of a strip-shaped article, which apparatus enables a feeding of strip-shaped articles, possibly in a twin design, of various widths, and also simultaneous feeding of two strip-shaped articles. 
     A further object of the invention is to provide an apparatus for a stepwise feeding of a strip-shaped article which apparatus has a frame, a first and a second feeding roller, which feeding rollers are adapted to receive between themselves the strip-shaped article to be fed, has a means for driving the two feeding rollers, which means are drivingly connected to the two feeding rollers and are adapted to drive the feeding rollers to oscillate and to contrarotate relative to each other, further having a rocker which has a first end and a second end located opposite of the first end, which first feeding roller is supported for rotation in the frame in a non displaceable state and which second feeding roller is supported for rotation in the rocker, which second feeding roller includes an axis, further has means for moving the rocker, which means are connected to the rocker and are adapted to move the rocker including the feeding roller supported therein towards to first feeding roller into a feeding position and away from the first feeding roller into a return position, which rocker moving means include a control means which communicates with the feeding roller driving means and includes a translatory moveable rod member guided for an upwards and downwards movement, which rod member is mounted to the first end of the rocker and is adapted to move the rocker together with the second feeding roller supported in same, which rocker moving means is adapted to move the second feeding roller at a point of time of a reversal of a first sense of rotation of the oscillating feeding rollers into the feeding position, and at a point of time of a reversal of a second sense of rotation of the feeding rollers into the return position, which second feeding roller includes an axis, has, furthermore, a first pressure spring having a first end and a second end, which pressure spring rests at its first end on the rocker at a point between the axis of the second feeding roller and the second end of the rocker, and rests at its second end opposite of the first end on the frame, which pressure spring is adapted to act onto the rocker from the same side as the rod member and in a direction substantially parallel to a direction of movement of the rod member, has, furthermore, a clamping bar mounted to the rocker and a stationary clamping bar counter member mounted to the frame, which clamping bar is biased by the first pressure spring against the stationary counter members in order to arrest a respective strip-shaped article when the second feeding roller is in its return movement position, and is lifted off the stationary counter member when the second feeding roller is in its feeding movement position, which rocker is supported one-sided for rotation in a cantilever structure which in turn is supported for rotation in a non displaceable state. 
     Still a further object of the invention is to provide a twin feeding apparatus which includes two feeding apparatuses having feeding rollers, which apparatuses face each other of the side of their feeding members. 
     The advantages of the invention are seen mainly in that the apparatus can be applied alone as single apparatus for a feeding of strip-shaped articles of various widths, but can also be applied in a twin arrangement having two such apparatuses facing each other for a parallel feeding of two adjacently located strip-shaped article, and allows also a twin apparatus arrangement in which the two single apparatuses are positioned at a considerable distance from each other, so that extremely broad strip-shaped articles may be fed and processes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be better understood and objects other than those set forth above, will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings, wherein: 
     FIG. 1 illustrates a section through an apparatus for a stepwise feeding of a strip-shaped article structured in accordance with the present invention; 
     FIG. 2 illustrates a section along line II—II of FIG. 1; 
     FIG. 3 illustrates a section along line III—III of FIG. 2; 
     FIG. 4 is a illustration similar to FIG. 3, but for sake of clarity on a enlarged scale; 
     FIG. 5 is a side view of the rocker illustrated in FIG. 4; 
     FIG. 6 illustrates a section through a twin design embodiment for a feeding of two strip-shaped articles; 
     FIG. 7 illustrates a section through a twin design embodiment for a feeding of an extremely broad strip-shaped article; and 
     FIGS. 8 and 9 illustrate schematically the portion of the apparatus which includes the structural members for an oscillating driving of the feeding rollers. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The feeding apparatus illustrated in FIGS. 1 and 2 includes a frame  1 . A first, lower feeding roller  2  and a second, upper feeding roller  3  are arranged in or at, respectively the frame  1 . The first feeding roller  2  is supported for rotation in the frame  1  in a non displaceable state. The second feeding roller  3  is displaceable in a manner which will be described in detail further below. 
     These two feeding rollers are driven to oscillate. 
     The operation of the drive for these two feeding rollers will now be described with reference to FIG.  1  and to FIGS. 8 and 9. FIG. 1 illustrates a section through the feeding apparatus. FIG. 8 illustrates schematically the portion of the apparatus which encompasses the structural members for an oscillating driving of the feeding rollers  2 ,  3 . FIG. 8 is, thereby, to be compared with the left side of FIG. 1, whereby the illustration in FIG. 8 is simplified and schematically for an easy understanding of the disclosure. FIG. 9 is also a simplified side view of the structural elements illustrated in FIG.  8 . 
     The driving of the feeding apparatus takes place by a drive member illustrated in FIG. 1 in form of a bevel gear  4 . This bevel gear  4  is mounted to a shaft  5  which is adapted to be connected to a not particularly illustrated drive of a conventional design. 
     The bevel gear  4  meshes with a further bevel gear  6 . A disk  7  is supported for rotation in this further bevel gear  6 , which disk  7  is arranged eccentrically inside the further bevel gear  6 . The disk  7  supports at one of its sides an eccentrically arranged pivot pin  8  and at the other side a spur gear wheel  9  which is arranged coaxial relative to the disk  7 . This spur gear wheel  9  meshes with a ring  24  with an internal toothing. 
     The pivot pin  8  shown in FIG. 1 is now to be compared with the pivot pin  8  illustrated in FIGS. 8 and 9. 
     It is now obvious, that due to the eccentric arrangement of the disk  7  and of the gear wheel  9 , the eccentrically arranged pivot pin  8  will perform in operation an oscillating movement (illustrated in FIG. 9 somewhat simplified). This oscillating movement is depicted in FIG. 9 by the double arrow  10 . For reasons of this explanation it shall be assumed that the illustrated rod  11  is moved back and forth and in the direction of its longitudinal extent, that is in the direction of the double arrow  10 , by a drive with an eccentric member or by a crank drive. The rod  11  which is moveable in the direction of its longitudinal extent drives an arm  12  which is pivotally mounted to the rod  11  by pivot pin  8 . 
     This arm  12  is also illustrated in FIG.  1 . The arm  12  is pivotally supported on the pivot pin  8 . A threaded spindle  14  extends through a guiding block  13  with an internal thread and meshes with same. The guiding block  13  includes a pin  17 , and the arm  12  is pivotally supported on this pin  17  through a slider  17   a . The position of the pin  17  determines the respective pivotal point for a respective extent of the feeding movement. The guiding block  13  is, further more, secured at the frame  1  against a rotation. 
     If the threaded spindle  14  is rotated by a not illustrated drive through the shaft  32  and the bevel gears  15 ,  16 , the guiding block,  13  is displaced along the spindle  14 . Thus, quite obviously, the pivotal point of the arm  12  supported on the pin  17  is now displaced, too. 
     A pivot pin  18  is supported at the free end of the arm  12 . This pivot pin  18  supports a slider  19  which is guided between the legs of a U-shaped arm  20 . This arm  20  is mounted to a shaft  21  which is to be driven to oscillate. This shaft  21  is illustrated in FIGS. 8 and 9 and can also be seen in FIG.  1 . 
     If the rod  11  is moved back and forth in the direction of the double arrow  10 , the arm  12  will pivot reciprocally around the axis of the pivot pin  17  of the guiding block  13  which axis thus forms the pivot axis. The pivotal movement of the lower end of the arm  12  caused by mentioned movement is transmitted through the pivot pin  18  and the slider  19  which slides between the legs of the arm  20  onto this arm  20 , wherewith the shaft  21  is driven to oscillate. 
     Such as already mentioned above, the pivotal point of the arm  12  can be adjusted by a rotating of the threaded spindle  14 , so that the length of the lever arm  8 - 17  and of the lever arm  17 - 18  are changed, wherewith the magnitude of the amplitude of the end of the arm  12  which supports the slider  19  and accordingly the amplitude of the pivotal movement of the shaft  21  can be adjusted. 
     It is, thereby, important that the translatory movement of the rod  11  and the movement of the pivot pin  8  remain always the same independent from mentioned amplitude of the arm  12 , so that accordingly the amplitude of the pivotal motion of the shaft  21  can be adjusted. 
     Due to mentioned arrangement of the slider  19  of the arm  12  it is achieved that the force exerted by the slider  19  onto the arm  12  acts always perpendicularly onto the arm  12 . Accordingly, the arm  12  can sweep over a range of 180°. 
     Returning to FIGS. 1 and 2 it now will be described how the driving principle as explained above is applied to the drive of the two feeding rollers  2  and  3 . 
     The earlier described further bevel gear  6  which meshes with the driving member, that is the bevel gear  4  which is mounted to the shaft  5 , is mounted to a drive shaft  22 . 
     It already has been mentioned that disk  7  is arranged eccentrically inside the further bevel gear  6  and is rotatable inside the further bevel gear  6 . At one of its sides this disk  7  carries the eccentrically arranged pin  8  which is also illustrated in the FIGS. 8 and 9. 
     At its opposite side the disk  7  is mounted to coaxially arranged spur gear wheel  9 . This gear wheel  9  meshes with ring  24  with internal toothing which ring  24  is fixed and set in the frame  1 . When the drive shaft  22  rotates, the gear wheel  9  rolls along the internal toothing of the ring  24 . The relation ship between the diameters of the rolling circle of the coaxial gear wheel  9  and of the ring  24  amounts to 1:2. 
     The arm  12  is supported on the pivot pin  8 , see also FIGS. 8 and 9, which arm  12  is pivotally supported on the pivot pin  17  of the guiding block  13 . It already has been mentioned that the guiding block  13  may be displaced by a rotating of the threaded spindle  14  as described earlier. 
     Still referring to FIG. 1, the arm  12  carries at its lower end the pivot pin  18  with the slider  19  which cooperates as described above with the arm  20 . The arm  20  is mounted to the shaft  21 . This shaft  21  is in turn mounted to a gear wheel  25 . This gear wheel  25  is connected through a suitable coupling  26  to a shaft  81  which carries the second feeding roller  3 . 
     The gear wheel  25  meshes with a further gear wheel  28  which is mounted to a shaft  29  which in turn carries the first feeding roller  2 . 
     When the drive shaft  22  is driven through the bevel gear wheels  4  and  6  the spur gear wheel  9  which is guided by the disk  7  in the gear wheel  6  rolls along the inner toothing of the ring  24 . Due to the already mentioned relation of the diameters of the rolling circles of gear wheel  9  and ring  24  of 1:2, the pivot pin  8 , see also FIGS. 8 and 9, is rectilinearly moved back and forth between two end points, whereby this movement, such as explained with reference to FIGS. 8 and 9, remains always the same, independent from the position of the pivotal axis of the arm  12 . 
     The oscillating rotary movement of the shaft  21  is accordingly transmitted to the two feeding rollers  2 ,  3  which accordingly are driven to oscillate in a counter-rotating manner, whereby upon one single revolution of the drive shaft  22  the feeding rollers perform one complete reciprocating back and forth movement. 
     Thus, in this described embodiment the above explained structural members identified by the reference numerals  7 ,  8 ,  9 ,  12 ,  13 ,  17 ,  18 ,  19 ,  20  form a means for driving the two feeding rollers  2 ,  3 . 
     The first feeding roller  2  is supported through the shaft  29  in an overhung position in a supporting portion  31  of the frame  1 . It is supported to rotate in the supporting portion  31  in a non displaceable state. The supporting portion  31  includes a recess  87  for the receipt of an edge portion of a strip-shaped workpiece to be fed or advanced, respectively by the feeding apparatus. The second feeding roller  3  is supported in a rocker  30 . This rocker  30  has a first end  33  and a second end  34 . 
     A translatoric moveable rod member  35  which can move up and down is pivotally mounted to the first end  33  of the rocker  30 . 
     A first pressure spring  36  rests, furthermore, at one of its ends on the rocker  30  at a point between the shaft  81  of the second feeding roller  3  and the second end  34  of the rocker  30 , and rests at its opposite end via an adjusting screw  23  on the frame  1 . This first pressure spring  36  acts from the same side as the rod  35  onto the rocker  30  and substantially in a direction parallel to the direction of movement of the rod  35 . 
     The rod  35  has a circumferentially extending collar  38 . A second pressure spring  39  is arranged between this collar  38  and the frame  1 . Because the rod  35  is pivotally mounted to the rocker  30 , the rocker  30  rests accordingly at its first end  33  via this second pressure spring  39  against the frame  1 . 
     This pressure spring  39  ensures at all condition of the apparatus the necessary pressing-on force of a roller  41  onto a cam  64  such as will be described later. 
     The rocker  30  is pivotally mounted at its first end  33  to the rod  35 . This rod is in turn pivotally mounted to a lever pair  40 ,  40   a  which carries at its free and a roller  41  supported for rotation thereon. Thus, the rocker  30  communicates at its first end  33  with mentioned lever pair  40 ,  40   a.    
     The lever pair  40 ,  40   a  is pivotally mounted to a piston rod  43  at a point between its point of connection to the rod  35  and the point of connection to the roller  41 . This piston rod  43  is mounted to a piston  42 . A bolt  44  is, furthermore, mounted to the piston  42 , which bolt  44  coacts with an adjusting nut  45  having a height scale and which is screwed into the frame  1 . The roller  41  cooperates with cam  64  located on the drive shaft  22 . 
     As will be shown, the structural members identified in this embodiment by the reference numerals  35 ,  36 ,  38 ,  39 ,  40 ,  41 ,  64  form a means for lifting the rocker  30 . 
     It already has been mentioned that the drive for the drive shaft  22  is coupled to the drive of the feeding rollers  2  and  3 . 
     A clamping bar  46  is arranged in the rocker  30 . The clamping bar  46  is mounted to a shaft  72  such as will be described further below. To this end, a wedge  37  of a corresponding wedge and keyway connection is illustrated in FIGS. 4 and 5. 
     As has been described the rocker  30  rests at its second end  34  on spring  36 . A recess  47  with a collar  48  which forms an abutment surface is arranged at the second end of the rocker  30 . An abutment head  49  of a control rod  50  is located in this recess  47 . This control rod  50  is pivotally mounted to a bell crank lever  51  which is supported at the frame  1  by the agency of a shaft  52 . The bell crank lever  51  is mounted at its other end to a piston rod  53  which includes a thread  54  by means of which it engages a flange  55  of the bell crank lever  51 . 
     The piston rod  53  is mounted to a first piston  56 . This piston  56  is located in a chamber  58  of a cylinder  88 . A second piston  57  is arranged on the piston rod  53 , which second piston  57  can slide along the piston rod  53  and is located in a further chamber  59  of the cylinder  88 , which second piston  57  has a larger diameter than the first piston  56 . The transition from chamber  58  in which the first piston  56  moves to the chamber  59  with the second piston  57  is designed on an abutment for the second piston  57 . Both chambers  58 ,  59  are connected to the infeed lines  60  of a pneumatic system. Piston  42  communicates also with this pneumatic system. Suitable control devices  61 ,  62  are built in the infeed lines  60 . 
     Now, the stepwise feeding of a strip-shaped article, for instance a sheet metal web  63  will be described, which sheet metal web  63  is arranged between the two feeding rollers  2  and  3 , thus at the area of the so-called bite of the feeding rollers  2  and  3 . For ease of understanding the cam  64  is illustrated as being divided into two portions  64   a  and  64   b . This division is identified by two diametrically opposite located points A and B. It is assumed furthermore, that the drive shaft  22  rotates counter-clockwise. 
     When the roller  41  rolls at the point A onto the portion  64   a  of the cam  64 , the roller  41  will be lifted by the cam portion  64   a . The rod  35  is accordingly moved downwards and presses the rocker  30  against the force of the spring  39  downwards. Due to the force which is exerted by the rod  35  onto the first end  33  of the rocker  30 , the rocker  30  is pivoted downwards at the point of the connection between the rod  35  and the rocker  30 . The upper, thus second feeding roller  3  is pressed against the lower, thus first feeding roller  2  which is supported in a non-displaceable state, i.e. which is stationary. The upper feeding roller  3  lies now on the sheet metal strip  63 . Because the point of contact between the upper feeding roller  3  and the sheet metal strip  63  acts at this point of time as pivotal point of the rocker  30 , the clamping bar  46  is lifted off the sheet metal strip  63 . The two feeding rollers  2  and  3  which rotate at this time in the direction of the feeding movement engage the sheet metal strip  63  and feed it forwards. After a revolution of the drive shaft  22  by 180°, during which time span the cam portion  64   a  acts onto the roller  41 , the cam portion  64   b  begins to act onto the roller  41  at point B. The springs  36  and  30  cause now the rocker  30  to pivot around the axis of the upper, second feeding roller  3  and a lifting of the rod  35  which causes the lever pair  40 ,  40   a  to pivot and causes a downwards movement of the roller  41 . This downwards movement of the roller  41  is possible because the distance between the control surface portion of the cam portion  64   b  and the axis of the drive shaft  22  is smaller than the distance between the control surface portion of the cam portion  64   a  and the axis of the drive shaft  22 . 
     The mentioned pivoting of the rocker  30  causes a lowering of the clamping bar  46 , which presses the sheet metal strip  63  against the stationary abutment  65 . Thus, the sheet metal strip  63  is firmly clamped. The stationary abutment  65  is a portion of the frame  1  of the feeding apparatus. After the sheet metal strip  63  has been clamped as described above, the upper, second feeding roller  3  is lifted. The point of contact clamping bar  46  sheet metal strip  63  becomes now the pivotal point of the rocker  30  connected via the shaft  72  to the clamping bar  46 . The two feeding rollers  2  and  3  do not act any longer onto the sheet metal strip  63  and during the continued rotating of the drive shaft  22  the feeding rollers  2  and  3  perform by a further 180° their return movement which is opposite to this feeding movement. When after a complete revolution of the drive shaft  22  the composition  64   a  begins again to act onto the roller  41  at the point A, the feeding cycle is again initiated in that the feeding rollers  2  and  3  are again pressed against each other and clamping bar  46  is lifted off. 
     The cam  64  must be of such a design that the feeding rollers  2  and  3  are pressed towards each other and moved away from each other, respectively precisely at the point of time of the change of their oscillating movement, and specifically in synchronism with the lifting and pressing, resp. movement of the clamping bar  46 . 
     In order to ensure a correct performance of the feeding apparatus at various thicknesses of the articles to be fed, the height position of the pivotal point of the lever pair  40 ,  40   a  can be adjusted by a adjusting of the position of the adjusting nut  45 . 
     The length of feed is adjusted by adjusting the amplitude of the oscillating movement of the feeding rollers, that is as mentioned by a displacing of the guiding block  13  along the spindle  14 . 
     The positions of the rocker for various states of operation which now will be described are controlled by a pneumatic control. A pressurized medium, here pressurized air, is fed from a source of pressurized air through the feed line  66 . This feed line  66  is branched into two branch lines  67 ,  68 . The control devices  61 ,  62  are arranged at these branch lines  67 ,  68 . 
     A connecting line  69  is branched off the branch line  68  at a point downstream of the control device  62 , which connecting line  69  extend to the cylinder chamber above the piston  42 . 
     With regard to the pneumatic controlling of the feeding apparatus one generally can differentiate between two setting up states and two operating states. During the setting up states during which the operating members are in their setting up positions, the feeding apparatus and obviously the punch press which operates together with the feeding apparatus are at rest, as a rule in the range of the upper dead point. The roller  41  is situated at this state of the highest point of the cam  64  between the points A and B. 
     During the operating states, during which the various operating members act into the sheet metal strip to be fed and during which obviously the punch press with which the feeding apparatus cooperates is in operation, the drive shaft rotates in the direction identified by the arrow illustrated in FIG.  2 . 
     In the first setting up position the upper feeding roller  3  and the clamping bar  46  are in a lifted position. This means that the upper feeding roller  3  is lifted off the lower feeding roller  2  and that the clamping bar  46  is lifted off the abutment  65 . 
     When mentioned members are in the indicated setting up positions, a new strip  63  can be slid into the feeding apparatus. 
     In order to move mentioned members into mentioned positions the chambers  59  of the cylinder  88  and the chamber above the piston  42  are pressureless. Accordingly, the first end  33  of the rocker  30  which first end  33  is pivotally mounted to the spring loaded rod member  35  is lifted up by the action of the pressure spring  39 . 
     At the same time the chambers  58  of the cylinder  88  is pressurized. Conclusively, the pistons  56  and  57  and the piston rod  53  are moved towards the right. The bell crank lever  51  is thus rotated and lifts the control rod  50  with its abutment head  49 . Accordingly, the second end  34  of the rocker  30  is also lifted in that the abutment head  49  comes to contact the collar  48 . 
     Therefore, the upper feeding roller  3  and the clamping bar  46 , as well, are lifted. 
     In the second setting up position the upper feeding roller  3  is lifted off and the clamping bar  46  is pressed onto the slid in strip  63 , that is towards the abutment  65 . 
     In this setting up position the strip  63  which has been slid in is arrested by the clamping bar  63 , for instance for further setting up procedures. 
     In order to arrive at these positions of mentioned members the chamber  59 , the chamber above the piston  42  and the chamber  58 , as well, are pressureless. Accordingly, the second end  34  of the rocker  30 , at which end the control rod  50  engages the rocker  30  is lowered by the action of the spring  36 . The rod  50  is, thus, pulled down and the bell crank lever  51  is rotated accordingly and conclusively the piston rod  53  with the piston  56  are moved towards the left because the chamber  58  is pressureless. So, the upper feeding roller  3  is lifted and the clamping bar  46  is pressed down. 
     The first operating state is applied when the tool which is mounted in the punch press to which the metal strip is fed by the feeding apparatus has no positioning pins for a precise positioning of the strip  63  during the processing of the strip  63 , for instance during a punching operation. The use of positioning pins is well known in the art and thus must not be explained in detail. In this operating state the strip  63  is continuously positioned and arrested, that is in any operating position of the strip processing members of the punch press with which the feeding apparatus cooperates, either by the feeding rollers  2  and  3  or by the clamping bar  46  and the abutment  65 . 
     Thus, the strip  63  is never loose. 
     Hereto, the chamber  59  and the cylinder chamber above the piston  42  are pressurized and the chamber  58  is pressureless. 
     Since the chamber  58  is pressureless, the second end  34  of the rocker  30  can not rest on the control rod  50 , because the control rod  50  can move the piston  56  by the bell crank lever  51  and the piston rod  53  towards the left. Conclusively, in the lower dead point position of the feeding apparatus that is when the roller  41  is located at the lowermost surface area of the cam  64 , the clamping bar  46  is held pressed against the strip  63  and arrests the strip  63 . 
     The second operating state is applied when the tool mounted in the punch press includes positioning pins for a precise positioning of the strip  63  during its processing, for instance during a punching operation. In this state the strip  63  is exclusively positioned and arrested by the positioning pins during the acting of the tools on the strip  63 . By means of such a procedure also a summarizing of feeding distance errors is avoided. 
     To this end, the strip  63  must lie loose after the conical positioning pins have penetrated the strip. 
     Hereto, the chamber  59 , the cylinder chamber above the piston  52  and the chamber  58  are pressurized. 
     Before the roller  41  comes to rest on the lowermost point of the cam  64 , the rocker  30  will come to rest at its second end  34 , specifically the shoulder  48  on the abutment head  49  of the now stationary control rod  50 , which is stationary locked because the above mentioned chambers are pressurized. 
     The roller  41  moves now towards the lowermost point of the cam  64  and before the roller  41  comes to rest on precisely the lowermost point of the cam  64 , the rocker  30 , as mentioned, comes to lie at it second end  34  via the shoulder  48  on the resting head  49  of the stationary control rod  50 . 
     Therefore, this location will now be the pivotal point for the now following pivotal movement of the rocker  30 . 
     Thus, during the moving of the roller  41  towards the lowermost point of the cam  64 , the first end  33  of the rocker  30  is lifted further by the rod  35 , and accordingly the upper feeding roller  3  and the clamping bar  46  will be lifted further during the pivoting movement of the rocker  30  until the roller  41  had reached the lowermost point of the cam  64 . 
     And conclusively, the strip  63  is now completely loose. 
     The precise point of time of this described lifting is set at the thread  54  by the nut  55  so that the bell crank lever  51  is rotated and accordingly the position of the rod  50  is adjusted. 
     Reference is now made specifically to FIGS. 3,  4  and  5 . The rocker  30  is supported to rotate in an overhung state on a cantilever. 
     This cantilever includes a sleeve  70  which is supported for free rotation in a bearing  75  set into the frame  1 . The sleeve  70  is firmly mounted to a arm  71  by means of a press fit so to rotate with the arm  71 . The arm  71  projects laterally from the sleeve  70 . A shaft  72  which extends parallel to the sleeve  70  is releasably clamped in the arm  71 . To this end the arm  71  is slit at its end remote from the sleeve  70 . Clamping screws  73  and  74  extend through the slit end portion of the arm  71 . 
     The rocker  30  is in turn mounted for rotation on the shaft  72  through bearings  77  and  78 . 
     The upper, second feeding roller  3  is supported through bearings  79  and  80  in the rocker  30 . The feeding roller  3  sits on a shaft  81  which extends coaxially through the sleeve  70 . The reference numeral  90  denotes the wedge of a corresponding wedge and keyway connection. The shaft  81  ends at the coupling part  26 . 
     As clearly can be seen, the outer diameter of the shaft  81  is smaller than the inner diameter of the sleeve  70 . This means that when the rocker  30  moves, the shaft  81  can move freely in a radial direction inside of the sleeve  70 . 
     The clamping bar  46  is firmly mounted to the shaft  72 . 
     The changing instant of the resting or pressing, resp. states between the roller  3  and the clamping bar  46  proceeds at the position of the cam as illustrated in FIG.  2 . In this position the timing of the lifting (basic setting) can be set precisely by a rotating of the shaft  72  in the arm  71 . During this setting both the roller  3  and the clamping bar  46  rest on the strip  63 . The adjusting according to the thickness of the strip, depending from a respective strip to be processed in the punch press, proceeds exclusively at the adjusting nut  45  such as described earlier. 
     Because the rocker  30  is supported in an overhung state on a cantilever, it is possible to produce with two of the described feeding apparatuses a twin feeding apparatus in that two such feeding apparatuses are arranged so that they face each other. 
     A first embodiment of a twin feeding apparatus is illustrated in FIG.  6 . 
     The design of the two individual single feeding apparatuses is the same as the design of the feeding apparatus described with reference to FIGS. 1 and 2, so that in the following only those structural members must be described which are specific to the twin feeding apparatus. 
     The feeding apparatus located in FIG. 6 at the left includes the shaft  5  which is coupled to a drive, which shaft  5  is mounted to the bevel gear wheel  4  acting as driving member. 
     A further bevel gear wheel  82  is located on the shaft  5 . This bevel gear wheel  82  meshes with a bevel gear wheel  83 . The bevel gear wheel  83  which is coupled to a first universal joint  84  which is followed by a telescope-like length adjustable drive transmission shaft  85  which is coupled to a second universal joint  84   a , which in turn is coupled to a bevel gear wheel  83   a  of the feeding apparatus located at the right side. This bevel gear wheel  83   a  meshes with a bevel gear wheel  82   a  which sits on the drive shaft  5   a  and meshes with the bevel gear wheel  4   a.    
     Accordingly, the two individual feeding devices of the twin feeding apparatus are simultaneously driven in synchronism from a drive common to both through the shaft  5 . 
     By means of this twin feeding apparatus it is now possible to feed or advance, resp. at the same time two sheet metal strips  63 A and  63 B. Thus, the two sheet metal strips  63 A and  63 B can be fed independently but in synchronism regarding the angular movement of the feeding rollers of the twin feeding apparatus. However, with regard to their thickness, their width, the length of the feeding steps and also regarding the material these strips  63 A and  63 B can be completely different from each other. It is, obviously, also possible to operate with one single strip only, which strip is engaged at both its side edge areas by the feeding rollers of the two individual feeding apparatuses. 
     FIG. 7 illustrates a embodiment of a twin feeding apparatus which finds application for extremely large strip widths. Again, only those structural members are described which are specific to this twin feeding apparatus. 
     The feeding apparatus located in FIG. 7 at the left side includes the shaft  5  which is adapted to be coupled to a drive and which is mounted to the bevel gear wheel  4 . This bevel gear which  4  meshes as described earlier with the further bevel gear wheel  6 . This further bevel gear wheel  6  sits on the drive shaft  22 . 
     The drive shaft  22  is coupled to a first universal joint  84  which is followed by a telescope-like length adjustable drive transmission shaft  85  which is followed by a second universal joint  84   a . This second universal joint  84   a  is directly connected to the feeding apparatus located in FIG. 7 at the right side. 
     This twin feeding apparatus can handle strips having a extremely large width. 
     The first lower feeding roller is supported in a overhung state at the corresponding supporting portion  31  of the frame  1 . It now is to be noted that this supporting portion  31  has a recess  87  into which the edge area of the strip to be fed projects. This recess  87  is important for the feeding of individual single strips, see FIGS. 1 and 6. It determines the maximal strip width. The dimension A in FIG. 6 determines the minimal distance between two strips. This dimension A is among others of a large importance regarding the space requirements of a punch press and only possible due to the “overhung” rocker. 
     While there are shown and described presently preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.