Abstract:
The invention relates to devices for aligning sheets ( 1 ), which are overlapped with an offset and supplied to the device by a stream feeder and which can be transferred to a device ( 63 ) that is located downstream, after alignment of the front edge and one lateral edge of the sheets. At least pant of a sheet can be brought to rest on the periphery of an alignment cylinder ( 62 ), which is used to align the front edge of the sheet by means of front lay marks located on the periphery of said cylinder. At least one recess is provided on the periphery of the alignment cylinder, which, by the application of a negative pressure to said recess allows at least part of the sheet to be fixed by friction on the periphery of the alignment cylinder, in such a way that in the contact zone, drive forces from said cylinder can be transferred by friction to the sheet. A measuring device ( 64 ) determines the offset of a lateral edge of the sheet in relation to a predetermined set alignment. A transversal displacement device is used to align a lateral edge of the sheet in accordance with the measurement result of the measuring device. The acceleration and/or speed and/or angle of rotation of the drive motor for driving the rotation of the alignment cylinder can be controlled or adjusted according to predetermined laws of motion, in particular in accordance with the angle of rotation of the alignment cylinder.

Description:
FIELD OF THE INVENTION 
     The present invention is directed to devices for aligning sheets. An alignment cylinder is shiftable axially. A feed table, that guides the sheets to the alignment cylinder, is also shiftable in the axial direction of the alignment cylinder. 
     BACKGROUND OF THE INVENTION 
     A device and a method for aligning sheets is known from EP 0 120 348 A2. There, the alignment of the front edges of the sheets takes place in a way wherein the sheets, arranged in the manner of fish scales, are fed to the device and are fed to an alignment cylinder of the device at a conveying speed which is greater than the circumferential speed of the alignment cylinder. Front lays are arranged on the circumference of the alignment cylinder, and against which the front edges of the sheets can be placed. Because of the relative speeds of the sheets and the front lays, the front edge of the sheet is braked at least slightly, and the front edge of the sheet is aligned because of this. Following the alignment of the front edge of the sheet, the area of the front edge of the sheet is fixed on a suction strip carried by the alignment cylinder by the application of a vacuum to the suction strip. The sheet is looped around the circumference of the alignment cylinder because of the continued rotatory driving of the alignment cylinder. Following the alignment of the front edge of the sheet and prior to transferring the sheet to a downstream-located device, a lateral offset of a lateral edge of the sheet is measured by a measuring device. The suction strip, on which the front edge of the sheet is fixed, is linearly displaced axially in the direction of the axis of rotation of the alignment cylinder as a function of the result of the measurement in order to align the lateral edge of the sheet in accordance with the desired alignment. The result of this is that the sheet can be transferred, placed in the correct position in regard to its front edge, as well as to a lateral edge, to a subsequent device, for example a sheet-printing press. 
     A device for sheet guidance of a sheet-fed rotary printing press is known from DE 23 13 150 C3. The sheets are conducted on a feed table in scaled layers to the device and then away from the device. The use of suction rollers, on whose circumferences recesses are provided, for conveying the sheets, which are lying flat on the feed table, is described. The sheet can be fixed on the circumference of the suction roller by the application of a vacuum. In this device, the suction roller is arranged in a recess of the feed table in such a way that the sheets, which lie flat on the feed table and are placed tangentially against the circumference of the suction roller, can be driven. It is achieved by this that the respective sheets come into contact with the suction roller only in a line-shaped contact area. The driving forces are frictionally transmitted, by the suction roller, to the sheet in the line-shaped contact area. Thus no looping of the sheets around the suction rollers is required. 
     A device with a suction drum is known from WO 97/35795 A1, and to whose circumference the sheets to be conveyed can be frictionally fixed by the application of a vacuum. In this case, the drive mechanism of the suction drum is structured in such a way that the number of revolutions and/or the angle of rotation of the suction drum can be controlled by an independent electrical motor in accordance with pre-selected movement laws. 
     A sheet-feeding device for printing presses is known from DE-AS 20 46 602. The lateral offset of a lateral edge of a sheet, in relation to a desired orientation, can be detected by a measuring device. For aligning the lateral edge of the sheet, it is possible to displace an alignment cylinder, on whose circumference the sheet is fixed, axially, in the direction of the cylinder&#39;s axis of rotation, as a function of the measurement result. 
     A device for measuring the position of the lateral edge of a sheet is known from EP 0 120 348 A2. This measuring device essentially consists of two measuring heads which, for measuring the position of the lateral edges, work together with interrogation gaps that are arranged at the circumference of a conveying roller. In order to be able to set the measuring heads to accommodate different sheet widths, the measuring heads are manually displaceable on a supporting cross-beam which is arranged above the sheet conveying level. 
     A contactless operating device for measuring the position of sheets is known from EP 0 716 287 A2. The lateral edges of the sheets can be measured by an optical system. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is directed to providing devices for the alignment of sheets. 
     In accordance with the present invention, this object is attained by the use of a sheet alignment device that has an alignment cylinder which can be shifted in its axial direction. A feed table, which guides sheets to the alignment cylinder, can also be shifted in the axial direction of the alignment cylinder. The alignment cylinder has at least one front register lay. The circumferential speed of the alignment cylinder is selected to be 0.7, to 0.9 times the sheet conveying speed when the sheet front edge contacts the front register lays. A sheet hold-down roller, which can work in cooperation with the alignment cylinder, has a helical cross-sectional shape. 
     The advantages to be obtained by the invention consist, in particular, in that, in the course of being conveyed by the alignment cylinder, the sheets can be simultaneously aligned in respect to their front edge, as well as in respect of their lateral edge. The alignment of the sheets, in respect to their lateral edge, can be advantageously achieved in that, following the alignment of the sheet front edge at the front lays, the alignment cylinder is axially displaced in the direction of its axis of rotation. 
     It is furthermore advantageous if the drive motor for the rotational driving of the alignment cylinder can be controlled or regulated as a function of predetermined movement laws, in particular as a function of the alignment cylinder angle of rotation. By this, it becomes possible to also take over sheets of different lengths in the correct position at the front lay by varying the circumferential speed of the alignment cylinder during its rotation, and to transfer the sheets, now exactly aligned, to downstream-located sheet conveying devices. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred embodiments of the present invention are represented in the drawings and will be described in greater detail in what follows. 
       Shown are in: 
         FIG. 1 , a cross-sectional view of a first embodiment of a device for the continuous alignment of sheets in accordance with the present invention, 
         FIG. 2 , the device in accordance with  FIG. 1 , showing an enlarged portion during a first phase for aligning the front edge of a sheet, 
         FIG. 3 , the device in accordance with  FIG. 2  in a second phase for aligning the front edge of a sheet, 
         FIG. 4 , the device in accordance with  FIG. 1  in longitudinal section taken along the section line I—I of  FIG. 1 , 
         FIG. 5 , a longitudinal view of a second embodiment of a device in accordance with the present invention, 
         FIG. 6 , the device in accordance with  FIG. 5  in cross section, 
         FIG. 7 , a perspective view of a sheet feeder in accordance with a third embodiment of the present device, 
         FIG. 8 , the sheet feeder in accordance with  FIG. 7  in a second perspective plan view, 
         FIG. 9 , the sheet feeder in accordance with  FIG. 7  in section in a perspective plan view, 
         FIG. 10 , the seating of the alignment cylinder for the sheet feeder in accordance with  FIG. 7  in a perspective plan view, 
         FIG. 11 , the sheet feeder in accordance with  FIG. 10  with a feed table and with schematically represented sheets, in a perspective plan view, 
         FIG. 12 , a perspective view of an embodiment of a sheet conveying device for a sheet feeder in accordance with  FIG. 7 , 
         FIG. 13 , a perspective view of a sheet guidance device for a sheet feeder in accordance with  FIG. 7 , 
         FIG. 14 , a first phase, during the alignment of a moving sheet, in a sheet feeder in accordance with  FIG. 7  in a perspective plan view, 
         FIG. 15 , a second phase, during the alignment of the sheet, in accordance with  FIG. 14  in a perspective plan view, 
         FIG. 16 , a phase during the alignment of the sheet in accordance with  FIG. 14  in a perspective plan view, 
         FIG. 17 , diagrams showing path, speed and acceleration of the rotational movement of an alignment cylinder applied over the angle of rotation of the alignment cylinder during one revolution, 
         FIG. 18 , diagrams showing path, speed and acceleration of the linear movement of an alignment cylinder axially in the direction of its axis of rotation applied over the angle of rotation of the alignment cylinder during one revolution, 
         FIG. 19 , a top perspective view of a device for measuring the position of the lateral edges of a sheet in a sheet feeder in accordance with  FIG. 7 , 
         FIG. 20 , the device in accordance with  FIG. 19 , in a perspective view from below, 
         FIG. 21 , the device in accordance with  FIG. 19 , in a lateral plan view from the rear, 
         FIG. 22 , the device in accordance with  FIG. 19 , in a lateral plan view from a transverse side, 
         FIG. 23 , the device in accordance with  FIG. 19 , in a partially sectional representation in a perspective plan view, 
         FIG. 24 , the drive mechanism of the device in accordance with  FIG. 19 , in a perspective plan view, 
         FIG. 25 , a gear stage of a device in accordance with  FIG. 19 , in a perspective plan view from below, 
         FIG. 26 , the drive motor of a device in accordance with  FIG. 19 , in a perspective plan view from below, 
         FIG. 27 , a cover element for a device in accordance with  FIG. 19 , with an associated guide device, in a perspective plan view from below, 
         FIG. 28 , a partial element of a coupling element in accordance with the present invention, in a perspective plan view, 
         FIG. 29 , a perspective view of a further partial element of a coupling element, 
         FIG. 30 , a coupling element in a perspective plan view, 
         FIG. 31 , a coupling for transmitting a driving torque to an axially displaceable shaft, in a lateral view, 
         FIG. 32 , a coupling in accordance with  FIG. 31  during a first phase for the rotational drive of an axially displaceable shaft, and in 
         FIG. 33 , a coupling in accordance with  FIG. 32  during a second phase for the rotational drive of an axially displaceable shaft. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A device  02  for aligning sheets  01 , in accordance with a first preferred embodiment of the present invention, is represented, partly in cross section, in  FIG. 1 . Devices of this type are used for aligning sheets, which are conveyed to the device in an overlapping or shingled manner from a device for overlapping, which is not represented, in their correct positions so that the sheets, now correctly aligned, can be transferred to a downstream-located web-fed printing press, for example. As depicted in  FIG. 1 , the sheets  01 , which are lying one behind the other, are fed to the device  02  in such a way that each front edge  07  of the respectively rear or trailing sheet  01  rests underneath the sheet  01  respectively leading, or lying in front of it. The device  02  is used, in particular, to align the sheets  01 , conveyed in an overlapping manner during their conveyance through the device  02 , in their correct position in respect to the sheet front edge  07  and in respect to the sheet lateral edge so that, after leaving the device  02 , the sheets  01  can be conveyed, in their correct position, to a downstream-located device  03 , such as, for example, a transfer cylinder  03  of a web-fed printing press. An alignment cylinder  04 , which is substantially constructed of a drive shaft  05  and suction rollers  06 , which suction rollers  06  are arranged spaced apart on drive shaft  05 , is used for aligning the sheet  01  in the device  02 , as seen in  FIG. 4 . The alignment cylinder  04  has a diameter of between 140 mm and 150 mm, and in particular has a diameter of approximately 144 mm. The function of the device  02 , in the course of aligning the front edge  07  of the sheets  01 , can be seen in  FIGS. 2 and 3  in particular. 
     The upper portion, which is embodied in the manner of a suction roller  06 , of the alignment cylinder  04  is represented in  FIG. 2 . A front lay  08 , against whose front the front edge  07  of the sheets  01  can come to rest for aligning the front edge  07  of the sheets  01 , is fastened on the circumference of the alignment cylinder  04  along a line extending parallel with the axis of rotation of the alignment cylinder  04 . The alignment cylinder  04  is driven at a circumferential speed which is at least slightly less than the conveying speed of the sheets  01  on a feed table  09 . The sheets  01  are conveyed to the device  02  synchronously with the movement of the front lay  08 , so that each front edge  07  can reach the contact area of the front lay  08 . Because of the relative speed differential between the front lay  08  and the sheet front edge  07 , the sheet front edge  07  runs up to, and against the front lay  08  and because of this it can be continuously aligned during the contact phase between the sheet front edge  07  and the front lay  08 . It has been shown to be particularly advantageous if, during the contact between the front lay  08  and the front edge  07  of the sheet  01 , that the circumferential speed of the alignment cylinder  04  corresponds, at least at times, to approximately 0.7 to 0.9 times, and in particular to 0.8 times, the conveying speed of the layered sheets  01  immediately prior to contact between the front lay  08  and the front edge  07  of the sheet. “Immediately prior to contact . . . ” means “during first contact”. The alignment cylinder  04  performs one revolution for each conveyed sheet  01 . 
     The front lay  08  has a height of 2 mm to 4 mm, and in particular, has a height of 3 mm, above the circumference of the alignment cylinder  04 . 
     In order to be able to align the sheet  01  exactly on the front lays  08 , a sheet hold-down roller  11  is arranged opposite the alignment cylinder  04 . A recess  12  is provided on the circumference of the sheet hold-down roller  11  in such a way that, as can be seen in  FIG. 3 , the front lay  08  on the alignment cylinder  04  can be received in a contact-free manner when passing through the gap between the alignment cylinder  04  and the sheet hold-down roller  11 . The sheet hold-down roller  11  is driven by the alignment cylinder  04  through an appropriate gear arrangement, not specifically shown, and at a gear ratio 1:1, so that the alignment cylinder  04  and the sheet hold-down roller  11  move synchronously. The outer diameter of the sheet hold-down roller  11  is helically configured, wherein the largest radius of the sheet hold-down roller  11  is arranged approximately in the area of the recess  12  for the front lay  08 . It is achieved by this configuration of the sheet hold-down roller that the gap between the sheet hold-down roller  11  and the alignment cylinder  04  is minimized during each alignment phase of the front edge  07 . Thereafter the gap is increased again in the course of the further rotation of the sheet hold-down roller  11  so as not to hamper the conveyance of the sheets  01 . 
     A hold-down plate  13 , which is arranged in an inlet area  14 , as seen in  FIGS. 2 and 3 , is also used for stabilizing the sheets  01  during their alignment at the front lay  08 . In order to be able to configure the sheet alignment device  02  optimally as a function of the various method parameters, in particular as a function of the paper quality used, it is possible to support the feed table  09  and/or the hold-down roller  11  and/or the hold-down plate  13  so that they can be adjusted in height in respect to the alignment cylinder  04 . Based on the method parameters to be taken into consideration, the distance between a hold-down roller tangential plane  16 , measured when the maximum radius of the sheet hold-down roller  11  passes the alignment cylinder  04 , should be a distance of approximately 0.8 mm from the surface  17  of the feed table  09 . The alignment cylinder  04  is arranged below the feed table  09  in such a way that the sheets  01  come into contact substantially tangentially with the circumference of the alignment cylinder  04 . However, departing from an ideal tangential arrangement, the alignment cylinder  04  may be slightly upwardly displaced, so that an alignment cylinder tangential plane  19  extends along the alignment cylinder  04  at a slight distance, for example 0.5 mm, above the surface  17  of the feed table  09 . It is achieved by this, as can be seen in particular in  FIG. 3 , that a sheet  01  is slightly lifted in the contact area with the alignment cylinder  04 , so that an optimal placement of the sheet  01  on the circumference of the alignment cylinder  04  is possible, and the driving forces can be frictionally transferred to the sheet  01  from the alignment cylinder  04  over a contact surface of sufficient size. 
     As depicted in  FIG. 3 , a suction element  21  is arranged on the inside of the suction roller  06 , which is a part of the alignment cylinder  04 . A suction chamber  22  is provided in the suction element  21 , and from which air is permanently generated and aspirated by the use of a vacuum source, which is not specifically represented, so that an underpressure or suction of 0.2 to 0.6 bar prevails in the suction chamber  22 . In the phase that is represented in  FIG. 3 , the front edge  07  of the sheet  01  is already aligned in the correct position and rests against the front lay  08 . As soon as a recess  23  in the circumference of the suction roller  06  has reached the area above the suction chamber  22 , the underpressure or vacuum prevailing in the suction chamber  22  is transmitted into the recess  23 , so that the sheet  01  is frictionally fixed in place on the circumference of the suction roller  06 . The result of this is that, when the sheet is entering the contact area with the suction roller  06 , the sheet  01  is initially aligned by the front lays  08  in the correct position in respect to its front edge  07 , and subsequently is fixed in place on the suction roller  06  by the suction chamber  22  and by the recess  23  working together. 
     As can be seen in  FIG. 1 , the sheets  01  essentially lie flat on the sheet level defined by the surface  17  of the feed table  09  during the entire time of their conveyance through the device  02  for the alignment of sheets in accordance with the present invention. Following the alignment of the front edge  07  of sheet  01  in the correct position, the sheet  01  is fixed in place in the device  02  by at least one of the vacuum receiving recesses  23 , which are provided, starting at the front lay  08 , one behind the other on the circumference of the suction roller  06 , so that the suction roller  06  is frictionally connected with the sheet  01  in rectangular contact areas and can drive the sheet  01  in the sheet conveying direction. 
     Following the alignment of the sheet front edge  07 , an offset of a lateral edge of the sheet  01 , in respect to a predetermined desired alignment, is measured by the use of a measuring device, which is not specifically represented. As a function of the result of the sheet lateral offset measurement, the sheet  01  is displaced transversely, in respect to the sheet conveying direction, until the sheet lateral edge extends along the desired alignment. For aligning the lateral edges of the sheets  01 , the alignment cylinder  04  can be axially displaced in the direction of its axis of rotation. In accordance with the representation in  FIG. 1 , the alignment cylinder can be axially displaced out of, or into the drawing plane. To make this adjustment movement possible, the alignment cylinder, together with the drive shaft  05 , is fastened in a first frame element  24 , as seen in  FIG. 1 , which, in turn, is axially seated in the direction of the axis of rotation of the alignment cylinder  04  on a second frame element  26 , which can be mounted fixed to a rack, as seen in  FIG. 4 . For this purpose, the first frame element  24  can be embodied as a linear unit, which is seated in a rolling bearing, for example, and which can come into engagement with a prismatically configured linear guide  27  at the second frame element  26 . 
     The alignment cylinder  04  can be, and in particular together with the first displaceably seated frame element  24 , accelerated or braked linearly in the direction of the axis of rotation of the alignment cylinder  04  at a rate of up to +/−15 m/s 2 . 
     A transverse displacement device  32  for effecting the axial shifting of the alignment cylinder  04  is embodied in such a way that the alignment cylinder  04  can be linearly displaced, in particular together with the first displaceably seated frame element  24 , from a zero position through a distance of up to +/−8 mm, and in particular through a distance of up to +/−5 mm, in the direction of the axis of rotation of the alignment cylinder  04 . 
     The device  02  for the alignment of sheets is represented in  FIG. 4  along the section line I—I of  FIG. 1 . A total of six suction rollers  06  are arranged, fixed against relative rotation, on the drive shaft  05  for conveying the sheet  01 , which is located between the sheet hold-down roller  11  and the feed table  09 , in the conveying direction. The drive shaft  05  of the alignment cylinder  04  is rotatably seated on the first frame element  24  in bearing points  28  by schematically represented rolling bearings and can be rotatably driven by the operation of a drive shaft drive motor  29 . The drive motor  29  is also fastened on the first frame element  24  and also drives the sheet hold-down roller  11  via a gear  31  synchronously with the drive shaft  05 . The sheet hold-down roller  11  is also fastened on the first frame element  24  so that, as a result, the drive shaft  05 , together with the suction rollers  06 , the drive motor  29 , the gear  31  and the sheet hold-down roller  11 , can be linearly displaced by the linear movement of the first frame element  24  in the direction of the movement arrow  232 , i.e. in the direction of the axis of rotation of the drive shaft  05 , from a zero position in both directions. A motor, for example a linear motor  33 , whose linearly driveable power take-off shaft acts on the left end of the first frame element  24 , is fastened on the second frame element  26  and is usable for driving the first frame element  24  in the direction of the movement arrow  232 . Driven by the drive motor  33 , the first frame element  24  can be moved transversely in respect to the conveying direction of the sheets  01 , so that the lateral edge of the sheet  01  to be aligned can be aligned in the desired alignment as a function of the previously determined measurement result. 
     The drive motor  29  for the rotational driving of the drive shaft  05  can be controlled and regulated as a function of predetermined movement laws, and in particular as a function of the angle of rotation of the suction rollers  06 . It is thus possible to preset the acceleration, speed or the angle of rotation of the drive motor  29  for achieving desired movement kinematics, so that sheets of different lengths, in particular, can be conveyed by the use of identical suction rollers  06  and can be taken over, or passed on with the right alignment. 
     The front lays  08  on the circumference of the alignment cylinder  04  can preferably be accelerated or braked at a rate of up to +/−0.35 m/s 2 . 
     A second preferred embodiment of a device  40  for the alignment of sheets is represented in  FIG. 5 . A total of four suction rollers  42  are fastened, spaced apart from each other, on a drive shaft  41  which is driven by a drive motor that is, not specifically represented. Two front lays  43 , which extend slightly above the surface  44  of the feed table  46  when the drive shaft  41  is in a corresponding position, are arranged on the circumference of each of the suction rollers  42 . To be able to frictionally fix the sheets  01 , by use of an underpressure or a vacuum, in the course of the sheets being conveyed in the device  40 , suction elements  47  are provided on the interior of each of the suction rollers  42 , and the suction rollers  42  are stationarily fastened on a first frame element  48 . The first frame element  48  is seated, in a manner corresponding to the first device  02 , linearly displaceable, on a second frame element  49  and can be driven transversely in respect to the conveying direction of the sheets  01  by operation of a drive motor  51 , as seen in  FIG. 6 , but which is not represented in  FIG. 5 . The power transmission from the drive motor  51  to the first frame element  48  takes place by use of a cam disk gear  52  shown in  FIG. 5 , so that the first frame element  48 , together with the drive shaft  41 , the suction rollers  42 , the feed table  46  and a not specifically represented drive motor for the rotational driving of the drive shaft  51 , can be linearly driven transversely to the conveying direction of the sheets  01  out of a zero position in the direction shown by the movement arrow  53 . 
     The second embodiment of a device  40  for aligning sheets, in accordance with the present invention, is represented in cross section in  FIG. 6 . A sheet hold-down roller  54  is arranged above the suction rollers  42 , and whose outer circumference is embodied to be helical, so that the gap between the sheet hold-down roller  54  and the suction rollers  42  is reduced or increased as a function of the angle of rotation of the front lays  43 . After fixing the sheets  01  in place on the suction rollers  43 , and during or after the alignment of the lateral edges of the sheets  01 , the sheets  01  are accelerated or braked, by an appropriate driving of the suction rollers  42 , in such a way that the sheets  01  can be transferred in correct alignment, to a downstream-located device  56 , for example a transfer roller  56 . 
     A sheet feeder  59  for use in conveying and aligning sheets  01  and having a device  02 ,  40  for aligning sheets, in accordance with the present invention, is perspectively represented in  FIG. 7 . An alignment cylinder  62  and a transfer cylinder  63  are arranged one behind the other in the conveying direction of the sheets  01  in a rack or frame  61 . The alignment cylinder  62  can be rotatably driven by a drive motor  65 , which can be regulated as a function of its angle. The alignment of the lateral edges of the sheets  01  can be measured by operation of a measuring device  64 , for example measuring heads  64 , which are arranged on an inlet side of the sheet feeder  59 . As a result, the sheet feeder  59  is used for aligning the sheets  01  in respect to their front edge  07  and lateral edge, and for accelerating the sheets  01  in order to be capable of transferring them, depending on their length, in correct alignment to the downstream-located transfer roller  63 . 
     The sheet feeder  59  is perspectively represented from the opposite side in  FIG. 8 . 
     A section through the sheet feeder  59  depicted in  FIGS. 7 and 8  is perspectively represented in  FIG. 9 . The feed table  66 , on which the sheets  01  lie flat and are fed to the sheet feeder  59  in an overlapping manner, can be seen. The alignment cylinder  62  is again essentially composed of a drive shaft  67  and two suction rollers  68  fastened on the drive shaft. A plurality of recesses  76 , as seen in  FIG. 10 , are arranged behind each other and next to each other, so that a sheet  01  can be aspirated by use of an underpressure or vacuum for being conveyed on the suction rollers  68 . It can be seen in  FIGS. 9 and 10  that the recesses  76  start directly behind the front lays  69  and extend in the circumferential direction of the suction rollers  68  and are distributed over an angle of rotation area of approximately 200°. The result of this is that the sheets  01  can be frictionally fastened on the circumference of the suction rollers  68 , starting at 0°, which corresponds to the border of the front lay  69 , over an angle of rotation of the suction roller  68  of between 130° and 200°. Therefore, no special valve control, for turning the underpressure or vacuum on or off, is required. Instead, an underpressure or vacuum can be permanently applied to the suction chamber, because the sheets  01  are no longer automatically fixed in place on the suction rollers  68  at the time at which the angle of rotation area, which is embodied to be closed, of the suction rollers  68  is located above the suction chamber. The selection of the size of the angle of rotation area with the recesses  76  should be determined as a function of the sheet size to be processed. Holding elements  71  for use in fixing the sheets  01  in place after they have been transferred, are provided on the transfer roller  63 , which holding elements  71  fix the front edge of the sheets in place on the transfer roller  63 . 
     The alignment cylinder  62  is represented, removed from the sheet feeder  59 , in  FIG. 10 . The drive shaft  67  is seated, at three bearing points  72 , on a first frame element  73  and can be driven rotatingly by a drive motor, which is not specifically represented, arranged at the end  74  of drive shaft  67 . The front lays  69  on the suction rollers  68  divide the circumference of the suction rollers  68  into a first area with recesses  76 , and a second area without recesses. The first frame element  73  is seated on the rack or frame  61  in sliding sleeves  77  and is linearly displaceable in the direction of the axis of rotation of the drive shaft  67 , and can be displaced transversely to the conveying direction of the sheets  01  by the use of a drive motor  78 . 
     The assignment of a sheet  01  to the alignment cylinder  62 , when a sheet feeder  59  is operated, is represented in  FIG. 11 . First, the front edge  07  of the sheet  01  is aligned at the front lays  69  by the selection of appropriate relative speeds between the front edge  07  and the front lays  69 . Thereafter, the sheet  01  is fixed in place in the contact area between the suction rollers  68  and the underside of the sheet in that the recesses  76  reach the area above the suction chamber, which is charged with underpressure or vacuum. After the sheet  01  has been fixed in place, a relative movement transversely to the conveying direction between the sheet  01  and the alignment cylinder  62  is not possible. The entire first frame element  73  can be linearly displaced transversely to the sheet conveying direction  81 , in the direction indicated by the movement arrow  82 , for aligning one of the lateral edges  79  of the sheet  01 . 
       FIG. 12  shows the transfer roller  63  with holding elements  71 , a drive shaft  83  and a toothed drive wheel  84 . The transfer roller  63  is fastened to the rack  61  on both sides in bearings  86 . 
     A sheet guidance device  87  for use in the device  59  shown in  FIGS. 7–9 , is represented by itself in  FIG. 13 . The maximum distance between the sheets  01  and the surface of the feed table  66  is limited by hold-down plates  88 . In this case, the hold-down plates  88  can be oscillatingly lifted or lowered. 
     The alignment of a sheet  01 , in respect to its front edge  07  and in respect to its right lateral edge  79  and during the various phases of its conveyance on the alignment cylinder  62 , is represented in  FIGS. 14 to 16 . 
     In the phase represented in  FIG. 14 , the sheet  01  is conveyed in the conveying direction  81  at a conveying speed which is approximately 20% greater than the circumferential speed of the front lays  69  at the circumference of the suction rollers  68 . 
     Thereafter, and as represented in  FIG. 15 , the front edge  07  of the sheet  01  comes to rest against the front lays  69  and in the process is braked to the circumferential speed of the suction rollers  68 . The front edge  07  is aligned at the front lays  69  within a short time by being braked, without the sheet  01  coming to a stop. 
     The sheet  01  has now been correctly aligned in respect to its front edge  07 . At this time, the recesses  76  at the suction rollers  68 , which cannot be seen underneath the sheet  01 , reach the area of underpressure or vacuum above the suction elements  47 . The sheet is aspirated onto the circumference of the alignment roller  68  and fixed in place by operation of this suction. 
     Following the alignment of the front edge  07 , the sheet  01  is conveyed on in the conveying direction  81  by the continued rotational drive of the suction rollers  68 . In the course of their conveyance by the suction rollers  68 , the sheets  01  also continue to remain flat on the feed table  66 , which is formed by a three-part plate  89  in the area above the suction rollers  68 , as seen in  FIG. 16 . At about this time, the position of the sheet&#39;s right lateral edge  79  is measured by the non-represented measuring head  64 . At the same time, the motor  78  for driving the drive shaft  67  starts to accelerate in order to bring the sheets  01  up to the desired conveying speed in the conveying direction  81 . 
     Referring again to  FIG. 16 , the location of the sheet  01 , in the course of a next phase of the conveyance, can be seen. It can be seen in  FIG. 16  that the sheet front edge  07  has almost reached the rear edge of the plate  89 . In order to align the sheet lateral edge  79  in accordance with a desired position, the feed table  66 , together with the first frame element  73  located under it, the drive shaft  67  and the suction rollers  66 , has been displaced in the direction of the movement arrow  82  transversely in respect to the conveying direction  81  of the sheets  01 . The regulating distance  91  by which the sheet  01 , together with moved components, was displaced transversely to the conveying direction  81  in the direction of the axis of rotation of the drive shaft  67 , can be seen by the edge offset between the feed table  66  and the support surface  92  in the area of the transfer roller  63 . 
     In three diagrams,  FIG. 17  depicts the path, speed and acceleration of the suction roller circumference in respect to an angle of rotation. In a first phase P 1 , the circumferential speed is maintained constant. During this phase P 1 , the front edges  07  of the sheets  01  come to rest against the front lays  69  and are aligned by means of this. At the end of phase P 1 , the sheet  01  is correctly aligned in respect to its front edge  07  and is fixed in place on the suction roller  68  by the application of an underpressure or vacuum. 
     In the following phase P 2 , the suction rollers  68 , and therefore the sheet  01  respectively adhering to them, are accelerated in such a way that, at the time of the sheet transfer to the downstream-located transfer cylinder  63 , the sheets  01  have a speed corresponding to the circumferential speed of the transfer cylinder  63 . This speed is again maintained constant in phase P 3  in order to allow a clean transfer of the sheets  01  to the transfer cylinder  63 . As soon as the sheets  01  are fixed in place on the transfer cylinder  63 , the sheets  01  are released from the suction roller  68  because no more recesses are provided on the circumference of the suction roller  63  at the corresponding angle of rotation. At approximately the same time of being driven in the conveying direction  81 , the sheets  01  are being moved transversely in respect to the conveying direction  81  during phases P 2  and P 3  for aligning a lateral edge  79  in respect to a desired direction. At the end of phase P 3 , the sheet  01  has been completely released from the suction rollers  68  and is now driven by the downstream-located transfer cylinder  63 . During the subsequent phase P 4 , the drive shaft  67  must be driven in such a way that the circumferential speed of the suction rollers  68  after a complete revolution, i.e. after 360°, again just corresponds to the feed speed of the sheets  01  out of the device for overlapping, such as the sheet feeder  59 . As can be seen from the acceleration, or speed diagram, it may be necessary, to accomplish this, to brake the suction rollers  68  down to the speed zero and to drive them opposite the direction of rotation required for conveying the sheets  01 . Departing from the greatest negative acceleration, the suction rollers  68  are then accelerated just enough, so that after a full revolution, the circumferential speed corresponds to the desired circumferential speed for a clean transfer of the sheets  01  from the device for overlapping, such as the sheet feeder  59 . 
       FIG. 18  shows the regulating distance, the speed and the acceleration of the suction roller  68  transversely in respect to the conveying direction  81  during one revolution. In this case, the diagrams are based on a maximum regulating distance of 5 mm, starting at the zero position. No transverse regulating movements are performed during a first phase Q 1 . In this first phase Q 1 , the position of the sheet lateral edge  79  to be aligned is measured by the measuring device  64 . In the subsequent phase Q 2 , the suction rollers  68  are accelerated transversely to the conveying direction  81  and are braked again thereafter, until the suction rollers  68  have traveled over a regulating distance of 5 mm, measured transversely to the conveying direction  81  of the sheets  01 . At the end of phase Q 2 , the actual position of the lateral edge  79  to be aligned corresponds to the desired alignment. In phase Q 3  which then follows, no further regulating movement of the sheet  01  transversely to the conveying direction of the sheets  01  takes place. In this third phase Q 3 , the sheets  01  can be transferred without problems to the downstream-arranged transfer cylinder  63 . In the following phase Q 4 , the suction rollers  68 , together with the drive shaft  67 , are driven in such a way that the zero position has again been achieved no later than after one revolution. 
       FIG. 19  depicts a device  101  which is usable for measuring the position of the lateral edge  79  of a sheet  01 , such as can be used, for example, in a sheet feeder  59  as represented in  FIG. 7 . Two measuring heads  64  are provided in the device  101 , by use of which, the respective position of a lateral edge  79  of a sheet  01  can be determined. A correcting measurement signal, which can be evaluated in an installation control device, is issued by the measuring heads  64  as a function of the position of the lateral edge  79 . The lateral edge  79  of the sheet  01  to be measured must be arranged in such a way that the measuring heads  64  are positioned above and below the lateral edge  79 . The measurement itself is based on an optical system with the aid of light beams, such as described in EP 0 716 287 A2, for example. Of course any other measuring method or system, and in particular any contactless measuring method or system, can be used. In order to properly arrange the measuring heads  64  when processing sheets  01  of different widths, the measuring heads  64  are seated so that they are linearly displaceable along the position measuring device  101  in the direction indicated by the movement arrows  102  or  103  transversely to the conveying direction  81  of the sheets  01 . For this purpose, each of the measuring heads  64  is mounted on a carriage  104 , each of which can be displaced in a linear guide, not represented, between the plates  106 ,  107 . In this case, the carriages  104  are driven via a drive arrangement, which is not specifically represented in  FIG. 19 , by a drive motor  108  that is arranged underneath the plates  106 ,  107 . To make possible a conveyance of the sheets  01  on the surface of the plates  106 ,  107  which is as interference-free as possible, the gap between the plates  106 ,  107 , which gap is required for the passage of the carriages  104 , is closed by a cover element  109 . In this case, the surface of the cover elements  109  extends on a level, namely the sheet level, as defined by the resting of the sheets  01  on the plates  106 ,  107  in a flat, planar fashion. 
       FIG. 20  shows the lateral sheet edge position measured device  101  of  FIG. 19  in a perspective view, taken from below. In this case, the drive motor  108  can be seen in particular, which drive motor  108  transfers regulating movements to two drive wheels  112  by use of a toothed belt  111 . A tensioning roller  113  is provided for tensioning the toothed belt  111 . Two toothed racks  114  are driven by the drive wheels  112  by use of two drive pinions  121 , as seen in  FIG. 22 , which are connected, fixed against relative rotation, with the drive wheels  112 , but which drive pinions  121  are not represented in  FIG. 20 , wherein both toothed racks  114  are each connected with a carriage  104  of a measuring head  64 . The drive wheels  112  and the drive pinions  121  connected with them are each fixed in place by a bracket  115  on the frames of the plates  106  or  107 . 
       FIG. 21  shows the sheet lateral edge position measuring device  101  in a side view from behind. The toothed racks  114  are fastened to the carriages  104  in such a way that the teeth mesh on respectively opposite sides of the drive pinions  121 , which are not represented in  FIG. 21 . A linear regulating movement of the toothed belt  111 , for example in the directions indicated by the movement arrow  116 , causes oppositely directed regulating movements of the measuring heads  64  in accordance with the movement arrows  117 ,  118 . Of course the same applies for an opposite regulating movement of the toothed belt  111 , because of which, the measuring heads  64  can be moved apart. 
       FIG. 22  shows the sheet lateral edge position measuring device  101  in a lateral plan view from one side. The carriage  104  is seated on the plates  106 ,  107  and can be linearly displaced in linear guides  119 , which are formed by two grooves. The measuring head  64 , which is used as an electronic side marker, is fastened to the surface of the carriage  104 . The carriage  104  is driven by the toothed rack  114 , whose teeth mesh with a drive pinion  121 . The drive pinion  121  is, in turn connected, in a manner so that it is fixed against relative rotation, with the drive wheel  112 , which is driven by the drive motor  108  through the toothed belt  111 . 
       FIG. 23  represents a longitudinal section through the sheet lateral edge position measuring device  101 . The drive mechanism for the measuring heads  64  with the drive motor  108 , the toothed belt  111 , the drive wheels  112 , the drive pinion  121  and the laterally spaced, oppositely arranged, toothed racks  114 , can be seen once more. Moreover, in  FIG. 23  a cover element  109  is represented, one of which cover elements  109  is associated with each of the respective measuring heads  64 . The cover elements  109  are embodied as links and are therefore elastically deformable in the direction of their longitudinal axis. An outer end of each of the cover elements  109  is fastened on a carriage  104 , so that these cover elements  109  can therefore be moved, together with the measuring head  64 , by operating the drive motor  108 . If the measuring heads  64  are moved out of their maximally distant position toward each other, it is necessary to deflect the cover elements  109  in a downward direction in sections out of the sheet level in which the flat-lying sheets  01  are conveyed. For this purpose, two holding plates  122 ,  123  are provided for each of the two cover elements  109  in the device  101 , which two holding plates  122 ,  123  are arranged opposite each other and are used as guide devices for each one of the cover elements  109 . Grooves  124  of complementary shape are cut into the inside surfaces of each of the holding plates  122 ,  123  and extend in the shape of an arc of a circle downward, starting at the straight linear guide  119 . In the course of moving the oppositely-located carriages  104  toward each other, the cover elements  109  are downwardly deflected, so that because of this deflector, the cover elements  109  are either shortened or extended, depending on the position of the carriages  104  in the sheet level. 
     The arrangement for driving the measuring heads  64  by operation of the drive motor  108  is represented without the cover element and without the plates  106  or  107  in  FIG. 24 . 
       FIGS. 25 to 27  show enlarged portions of the drive mechanism for the carriages  104 , or for the measuring heads  64 . 
     A coupling, consisting of coupling elements  130 ,  131 ,  144 , and which is usable for transmitting a driving torque to an axially adjustable shaft, such as drive shaft  67  shown in  FIG. 9 , or its essential parts, is represented in  FIGS. 28 to 31 . Such a coupling  130 ,  131 ,  144  can be used, in particular, for transmitting the driving torque from a drive motor to an axially adjustable alignment cylinder of a device for aligning sheet  02 , as seen in  FIG. 1 , a device for aligning sheets  40 , as seen in  FIG. 4 , or a sheet lateral edge position measuring device  101 . By employing such a coupling  130 ,  131 ,  144  it becomes possible to mount the drive motor for the rotational driving of the alignment cylinder stationarily, so that the mass which must be accelerated in the course of the regulating movement for aligning the sheet lateral edges  79  is reduced. 
     Essentially, the coupling  130 ,  131 ,  144  is composed of three coupling elements, which are individually represented in  FIGS. 28 to 30 , respectively. The first coupling component is composed of two coupling elements  130 , as seen in  FIGS. 28 and 131 , as seen in  FIG. 29 . Each one of the two coupling elements  130 ,  131  has recesses or apertures  132 ,  133 ,  134 , which are each slightly larger than the diameter of the associated shaft  67 , for example the drive shaft  67  of the alignment cylinder  62 . Feather key grooves  136 ,  137  and  138  are provided on the inside of each of the recesses or apertures  132 ,  133 ,  134 , which key grooves  136 ,  137  and  138  can be brought into engagement with a feather key element, which is not specifically represented, and which is arranged on the drive shaft  67  for transmitting a torque. The first coupling element  130  has a slit  139  for its stationary fixation, so that by tightening a straining screw which is, not specifically represented, in a threaded bore  141 , the first coupling element  130  can be frictionally fixed in place on the associated drive shaft  67 . As represented in  FIG. 29 , the end of the second coupling element  131 , which is arranged on the associated drive shaft  67 , is embodied with two arms  142  and  143 , wherein the recesses or apertures  133 ,  134  are applied aligned with each other on the arms  142  and  143 . The distance between the arms  142  and  143  has here been selected to be such that the plate-shaped first coupling element  130  can be arranged, free of axial play, with its end arranged on the drive shaft  67  between the arms  142 ,  143 . 
     A second coupling component  144  is represented in  FIG. 30 , and which can work together with the first coupling component  130 ,  131 , that is composed of the coupling elements  130  and  131 , during the transmission of a torque. The third coupling element  144  has a bend, so that a radially outer end  146  of the third coupling element  144  projects past an end  147  of an associated shaft  148 . The third coupling element  144  is embodied to be fork-shaped on the side of the radially outer end  146  facing the first coupling component  130 ,  131 , and extends with two arms  149  and  151  in the direction of the first coupling component  130 ,  131 . Axial bearings  153 , in which the pivots of rolling bodies  154 , as seen in  FIG. 31 , can be fastened, are attached to each of the arms  149  and  151  and also to an oppositely located counter-bearing  152 . In this case, the axial bearings  153  are arranged in such a way that pivots  156  extend parallel with outside portions  157 ,  158  of the coupling elements  130 ,  131 , which come into engagement with the rolling bodies  154 . 
     Functioning of the coupling  130 ,  131 ,  144 , comprised of the second coupling component  144  and the first coupling component  130 ,  131 , put together from the coupling elements  130  and  131 , is explained by reference to  FIG. 31 . After installation of the coupling elements  130  and  131  at the one shaft end, and of the third coupling element  144  at the oppositely located shaft end, the outsides  157 ,  158  of the coupling elements  130 ,  131  rest against the inside of the rolling bodies  154 . By tightening the straining screw at the coupling element  130 , the coupling element  130  is fixed in place and fixes the coupling element  131  axially on the shaft end because of its arrangement between the arms  142  and  143 . The feather key grooves  137 ,  138  of the second coupling element  131  are made slightly wider than the feather key element of the drive shaft  67 , so that the second coupling element  131  can be slightly turned on the drive shaft  67 . A spring element  159 , which elastically braces the coupling element  131  against the coupling element  130  and which spreads the two coupling elements  130  or  131  open, is arranged between the radially outer ends  146  of the coupling elements  130 ,  131 . A resilient, free-of-play seating of the outsides  157  or  158  at the rolling bodies  154  is assured at any time by this arrangement. 
     If now a torque is applied to the drive shaft  67 , or to one of the oppositely located drive shafts  67 , the torque is transmitted by a positive connection between the rolling bodies  154  and the outer ends of the coupling elements  130  and  131 . A deflection of the coupling  130 ,  131 ,  144 , in particular in the course of frequent changes of the direction of rotation, is prevented to a large extent because of the elastic bracing of the two coupling elements  130  and  131 . 
     If the drive shaft  67 , or one of the drive shafts  67 , is axially displaced in the direction of its axis of rotation in respect to the opposite shaft, the outsides  157 ,  158  roll off on the rolling bodies  154 , so that an axial displacement, even under a load, is possible essentially free of resistance. 
     The employment of a coupling  130 ,  131 ,  144  with the coupling elements  130  and  131 , as well as the third coupling element  144 , in a sheet feeder  59  is represented in a view from above in  FIGS. 32 and 33 . 
     In the phase represented in  FIG. 32 , a sheet  01  has just arrived at the front lays  69  on the suction rollers  68 , so that the front edge  07  of the sheet  01  is aligned. In this phase, the feed table  66  which, together with the suction roller  68  and the drive shaft  67 , can be axially displaced in the direction of the axis of rotation of the drive shaft  67 , is in its zero position and can be displaced toward the right or the left in accordance with the movement arrow  161  by use of a linear drive, not represented in these drawings, but depicted and discussed in a prior section of the application. 
     The drive torque required for driving the drive shaft  67 , and therefore for conveying the sheets  01 , is generated by a drive motor  162  and is transmitted to the drive shaft  67  via the third coupling element  144  and the first and second coupling elements  130  or  131 . 
     The sheet position during a later process phase is represented in  FIG. 33 , into which the sheet  01  has now been moved transversely to the conveying direction  81  for aligning one of its lateral edges  79 . In the representation of  FIG. 33 , the required alignment movement is directed toward the right, which can be seen in particular from the edge offset  163  between the outer edge of the feed table  66  and the outer edge of the downstream-located device. The drive shaft  67  with the coupling elements  130  and  131  fastened thereon has also been axially displaced, together with the feed table  66 , in the direction of the axis of rotation of the drive shaft  67 . 
     In the course of the axially directed regulating movement for aligning the lateral edge  79  of the sheet  01 , the drive motor  162  was moved on by an angular amount of approximately 90° for conveying the sheet  01  in the conveying direction  81 . The compensation of the axial offset of the drive shaft  67  in relation to the drive motor  162  is made possible by the roll-off of the coupling elements  130  or  131  on the rolling bodies  154 . 
     While preferred embodiments of devices for aligning sheets, in accordance with the present invention, have been set forth fully and completely hereinabove, it will be apparent to one of skill in the art that various changes in, for example the type of press used to print the sheets, the specific nature of the downstream sheet handling or processing devices and the like could be made without departing from the true spirit and scope of the present invention which is accordingly to be limited only by the following claims.