Abstract:
A sheet processing machine receives sheets from a sheet feeder. The sheets are inspected and their trailing ends are trimmed. Subsequently, the sheets are turned and are split into a plurality of partial sheets or sheet pieces. The now trailing ends of the sheet pieces are trimmed. The sheet pieces are separated axially and are delivered to a sheet receiving device where the individual sheet pieces are deposited in various stacks.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a method for cutting sheets and to a sheet processing machine. A trailing end of a sheet is cut perpendicularly to a sheet transport direction by a first transverse cutting device. This sheet is then rotated or turned and the now trailing end is cut by a second transverse cutting device. 
     DESCRIPTION OF THE PRIOR ART 
     DE-AS 10 44 589 describes a transverse cutting device for paper webs. A belt system for transporting the sheets cut from the web is connected downstream of the transverse cutting device. 
     DE 43 13 452 A1 describes a device for cutting sheets from a web. Two transverse cutting mechanisms are provided with this device, by means of which first a leading end of the web is exactly cut to measure and the sheet is then cut off the web. 
     DE 42 38 387 A1 discloses a cut registration regulating device on transverse cutters of rotary printing presses. Here, a rotating cylinder is provided, which works together with a stationary opposed cutter. 
     SUMMARY OF THE INVENTION 
     The present object of the invention is based on creating a method for cutting sheets, and on a sheet processing machine with a cutting device. 
     In accordance with the invention, this object is attained providing a sheet processing machine which initially trims a trailing end of a sheet perpendicularly to a sheet transport direction by use of a first transverse cutting device. The sheet is then turned so that the trimmed trailing end now leads. The now trailing end of the sheet is trimmed perpendicularly to the sheet transport direction by a second transverse cutting device. 
     Present invention lie, in particular, in that transverse cutting from the start to the end of a sheet takes place without manual intervention in a sheet processing machine. It is possible by means of integrated inspection devices, to control the print quality itself, as well as the cut registrations in the sheet processing machine. In this way, it is possible to simultaneously control the fronts and backs of the sheet, which were printed, for example, on the obverse and reverse sides of the sheet. 
     A simple cut registration adjustment is possible because of the working together of the transverse cutting devices with a chain conveyor. This adjustment is advantageously performed by means of a position-controlled electric motor driving a cutting cylinder. 
     A longitudinal cutting device is assigned to a processing cylinder of the sheet processing machine, so that the sheet is cut “in-line” into two or more partial sheets. These sheets can be deposited on stacks, which can be selected by means of the inspection device. In this manner, sorted stacks with “good” and with waste sheets are formed. This has the advantage that, in case of a defective partial sheet, the entire sheet is not wasted. 
     By means of this sheet processing machine all sides of a sheet are cut and the latter is cut into partial sheets. All cuts made, as well as the obverse and reverse printing, are controlled by means of inspection devices, all of the cut sheets are deposited on selectable stacks. 
     This sheet processing machine performs a plurality of processing steps “in-line”, which leads to an increase in production and also to a reduction of manual labor. Moreover, the quality of the products made in this way is increased. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The sheet processing machine in accordance with the present invention is represented in the drawings and will be described in greater detail in what follows. 
     Shown are in: 
     FIG. 1, a schematic lateral view of a sheet processing machine; 
     FIG. 2, a schematic representation of the processing steps in the sheet processing machine; 
     FIG. 3, a schematic view from above on a stack of a delivery device of the sheet processing machine; 
     FIG. 4, an enlarged schematic lateral view of a processing cylinder of the sheet processing machine in accordance with FIG. 1; and 
     FIG. 5, an enlarged schematic view from above on the processing cylinder of the sheet processing machine in accordance with FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A sheet processing machine  1  for the transverse and longitudinal cutting of sheets  2  in accordance with the present invention is shown in FIG. 1, and has integrated inspection devices  3 ,  4 ,  6 . The sheets preferably are printed paper sheets, for example securities. For instance, this sheet processing machine  1  is constructed as will be described in what follows: 
     A feeder  7  essentially has a first stack  8 , a sheet separating device  9  and a delivery table  11 . This feeder  7  is followed by an installation  12  which is designed as a swing feeder. A first chain conveyor  13  works together with this swing installation  12 . This chain conveyor  13  has a pair of revolving chains  14 , to which axially extending chain gripper systems  16  have been attached. The chains  14  are reversed by a first, chain wheel carried on a first chain wheel shaft  17 , and by a second chain wheel carried on a second chain while shaft  18 . The chains  18  extend at least partially along a straight line between the first,  17 , and second chain wheel shaft  18 . Viewed in the transport direction T, the first inspection device  3  is arranged downstream of or often the first chain wheel shaft  17 . This first inspection device  3  has a suction box  19 , whose work surface facing the chain gripper system  16  is made at least partially transparent. Illumination installations, not specifically represented, are arranged under this transparent work surface. 
     A first transverse cutting device  21  is connected downstream of this suction box  19  of the first inspection device  3 . The first transverse cutting device  21  has a rotating cutting cylinder  22  and a stationary opposed cutter  24  fastened on a cross bar  23 . The cutting cylinder  22  is provided with at least one axially extending groove, into which a passing chain gripper system  16  can descend. A width of the groove in the circumferential direction of the cutting cylinder  22  is made larger than a width is required to receive the chain conveyor  16 . The cooperation chain gripper systems  16  the cutting cylinder  22  can be phase-shifted in respect to each other for adjusting the cut registration. In the sheet processing machine in accordance with the present example, rotating arms are provided on both sides of the cutting cylinder  22 , between which an axially extending cross bar is arranged to receive a cutter  26 . 
     The cutting cylinder  22  has a drive, whose phase can be changed in respect to the chain conveyor  13 . In the present invention this drive, is advantageously embodied as a separate, position-controlled electric motor. 
     The stationary opposed cutter  24  is arranged in a slightly oblique direction in respect to the axis of rotation of the cutting cylinder  22 , i.e. the opposed cutter forms an opening angle, with the transport direction T, which is not equal to 90° but is, for example 89°. From this, an angle of inclination of the opposed cutter  24  of, for example, 1° in respect to the axis of rotation of the cutting cylinder  22  results. The opposed cutter  24  is also slightly rotated around its longitudinal axis, i.e. the opposed cutter  24  has a slight twist. This insures that the first transverse cutting device  221  will make a cut in the moving sheet which is perpendicular to the longitudinal direction of the sheet. 
     The electric drive mechanism of the cutting cylinder  22  follows the speed of the chain conveyor  13  at an identical circumferential speed. Because of the twist of the cutter  24  and the superimposed conveying speed, an exactly right-angled cut of the sheet  2  is created in the end of the sheet  2  as the sheet  2  passes through the first transverse cutting device  21 . 
     The axially extending cutter  26  which is carried by the cutting cylinder  22 , is also slightly inclined or angled respect to the axis of rotation of the cutting cylinder  22  and also has a twist in longitudinal direction. The cutter  26  of the cutting cylinder  22  and the opposed cutter  24  are matched to each other. 
     A rotating opposed cylinder which, for example, has an opposed cutter  24  for performing a scissors cut, or an opposed strip, is also possible in place of the stationary opposed cutter  24 . It is also possible to design the cutter  26  and the opposed cutter  24  parallel in relation to the axis of rotation of the cutting cylinder  22  and without a twist. The cutting cylinder  22 , or respectively the opposed cylinder, can also have several cutters  26 . 
     A second inspection device  4  is installed downstream of this first transverse cutting device  21  in the area of the chain conveyor  13 . This second inspection device  4  essentially consists of a sensor  27 , illumination devices  30  and a suction box  35 . 
     A sheet turning device  28  follows the chain conveyor  13 . In the present invention, this sheet turning device  28  essentially consists of a storage drum  29  and a turning drum  31 . The storage drum  29  has a “double” circumference and is therefore equipped with two controllable gripper systems  32 , which are arranged offset by 180° in respect to each other, and two oppositely located suction systems  33 . A distance in the circumferential direction of the sheet storage drum between each of the gripper systems  32  and the suction systems  33  can be adjusted to the length of the sheets to be conveyed. The suction systems  33  are movable both in the circumferential direction and also in the axial direction of the sheet storage drum  29 . 
     The turning drum  31  has two controllable gripper systems  34 ,  36 , which are placed side-by-side and which are pivotably arranged around their longitudinal axis. 
     The turning drum  31  and the storage drum  29  can be phaseshifted in respect to each other. 
     A cylinder  37 , for example a processing cylinder  37 , and a cooperating longitudinal cutting device  38 , are situated downstream of the turning device  28 . This processing cylinder  37  has, for example, at least twice the circumference of the turning drum  51 , and carries four holding systems  39 ,  41 ,  42 ,  43 , which are designed as gripper systems  39 ,  41 ,  42 ,  43  and which are each controllable independently of each other. These holding systems  39 ,  41 ,  42 ,  43  can also be embodied as suction devices. Two of these gripper systems  39 ,  41 , or respectively  42 ,  43  are respectively located in a cylinder groove approximately axis-symmetrical next to each other in the axial direction in relation to a center of the processing cylinder  37 , and are displaceable in relation to each other in the axial direction. In the present invention, one of the gripper systems  39 , or respectively  42 , located axially next to each other, is arranged fixed in the axial direction, and the second gripper system  41 , or respectively  43  of each pair of gripper systems  39 ,  41  or  42 ,  43 , is displaceable in relation to the first gripper system  39 , or respectively  42 , for example by means of a cam  40  and cam rollers  45 . However, both gripper systems  39 ,  41 , or respectively  42 ,  43 , can be displaceable. The second pair of these gripper systems  42 ,  43  is located opposite the first pair of two gripper systems  39 ,  41  designed in this way and is offset by 180°. 
     The longitudinal cutting device  38  which is also seen most clearly in FIG.  4  and which has a plurality of cutter wheels  44  and, which is assigned to the processing cylinder  37 , is placed downstream, in the sheet transport direction T, shortly after the turning drum  31 . In the present invention, the longitudinal cutting device  38  has an axially extending cross bar  46 , on which three cutter wheels are arranged each of, which can be independently actuated and axially displaced. 
     A second chain conveyor  47  with two rotating chains  48  is arranged after the processing cylinder  37 . A plurality of chain gripper systems  49  are arranged on these chains  48 . These chain gripper systems  49  each consist of two chain gripper assemblies, which are placed next to each other in the axial direction, are approximately symmetrically arranged in relation to the machine center and can be operated independently of each other. In place of the processing cylinder  37 , the second chain conveyor  47  can also have chain gripper systems which can be moved in relation to each other in the axial direction. 
     It is also possible that more than two gripper systems  39 ,  41 , or respectively  42 ,  43 , i.e. any arbitrary number, are displaceable on the processing cylinder  37 . In case of three gripper system set in, which the gripper systems are arranged axially next to each other, the gripper system arranged in the center of each of the three, for example, could be fixed in place in the axial direction, and the two outer gripper systems could be designed so that they can be shifted away from the center system. 
     The chains  48  are reversed by a first chain wheel shaft  51  and second chain wheel shaft  52 . A median line, constituted by the chain wheel shaft  51  and the processing cylinder  37 , forms an opening angle B of less than 180°, for example 155°, with a median line constituted by the processing cylinder  36  and the longitudinal cutter wheels  44 . 
     Downstream of the first chain wheel shaft  51  of the second chain conveyor  47 , a suction box  56  is arranged in the second chain conveyor  47  underneath the chain  48 . A second transverse cutting device  57  follows this suction box  56 , which is constructed in a manner identical with the first transverse cutting device  21 . The first and second transverse cutting devices  21 ,  57  respectively are used for trimming the ends  71 ,  72  of the sheets  2 ,  82 ,  83 . The third inspection device  6  with a sensor  58 , illumination devices  59  and a suction box  61 , is connected downstream of this second transverse cutting device  57 . 
     A cut sheet feeder  62  in the area of the chain conveyor  47  follows the third inspection device  6 . This cut sheet feeder  62  has six stacks  63 ,  64 ,  66  to  69 , respectively two of which are arranged in pairs next to each other, as shown in FIG.  3 . The resulting three pairs of stacks  63 ,  64 , or respectively  66 ,  67 , or respectively  68 ,  69 , are arranged behind each other. The stacks  63 ,  64 , or respectively  66 ,  67 , of the first two pairs of stacks respectively have common lifting devices, so that respectively one pair of stacks can be raised and lowered together. Separate lifting devices have been provided for the two stacks,  68 ,  69  located next to each other, so that the two stacks,  68 ,  69  can be raised and lowered independently. 
     Gripper systems, or respectively chain gripper systems are understood to be a plurality of grippers, which are arranged on a shaft which can be pivoted around a longitudinal axis. 
     The functioning of the sheet processing machine  1  in accordance with the present invention is as follows: 
     A sheet  2 , in particular a sheet of paper printed on the obverse and reverse sides, is fed from a first stack  8  to the delivery table  11  by the sheet separating device  9 . The sheet  2  is grasped from this delivery table  11  by the swing feeder installation  12  and is passed over to a chain gripper system  16  in the area of the first chain wheel shaft  17  of the first chain conveyor  13 . The chain gripper system  16  conveys the sheet  2  along the “straight” portion of the chain conveyor  13  to the first inspection device  3 . The sheet  2  is checked, in segments, for damage such as, for example tears and holes, by means of the first inspection device  3 . The water mark of the sheet  2  is also inspected by the use of back lighting. In the course of this conveyance the sheet  2  is guided by the suction box  19 , to which a vacuum has been applied, of the first inspection device  3 . 
     The chain gripper system  16  conveys the sheet  2  through the transverse cutting device  21  to the second inspection device  4 . There, the sheet  2  is aspirated by the suction box  35  of the second inspection device  4  in the area of the front of the sheet  2 . A trailing end  72  of the sheet  2  is still in the transverse cutting device  21 , where a narrow strip  73 , which extends in the axial direction, is cut off its end  73 . In this case the conveying speed of the chain conveyor  13  and the circumferential speed of the cutter  26  are matched to each other, so that the trailing end  72  of the sheet  2  is trimmed at right angles in respect to the transport direction T all as depicted in FIG.  2 . 
     This sheet  2  having a first cut  74  is now inspected in the second inspection device  4 . In the inspection process, a front side or obverse side or of the sheet  2  and a fresh edge of the sheet  2  (cut registration resulting from the trimmed end  72  are inspected. 
     Thereafter, the chain gripper system  16  passes the front end  71  of this sheet  2  on to a gripper system of the storage drum  29 . This storage drum  29  conveys the sheet  2  in the direction toward the turning drum  31 . When front the end  72  of this sheet now reaches the area of the suction systems  33  of the storage drum, the latter aspirates the now trimmed trailing end  72 . Subsequently the suction systems  33  of the storage drum  24  move in an approximate arrow shape away from the center of the storage drum  29  and in this way tense the sheet  2  in the circumferential direction as well as in the direction toward lateral edges of the sheet  2 . 
     The phase shift between the turning drum  31  and the storage drum  29  is set to the length of the sheets  2  to be processed. The storage drum  29  conveys the front end  71  of the sheet  2  through the gap between the turning,  31  drum and storage drum  29  until the suction systems  33  reach this gap. The trimmed end  72  of the sheet  2  is grasped by the first gripper system  34  of the turning drum  31  and is released from the suction system  33  by turning off the vacuum. Thereafter both gripper systems  34 ,  36  of the turning drum  31  are pivoted against each other, and the trimmed end  72  of sheet  2  is passed from the first gripper system  34  to the second gripper system  36 . In their continued course the gripper systems  34 ,  36  pivot back into their initial position. 
     The trimmed end  72  is now grasped by the gripper system  36  so that it leads, and the untrimmed front end  71  trails. 
     The sheet  2  is passed on by the turning drum  31  to a pair of gripper systems  39 ,  41 , or respectively  42 ,  43  of the processing cylinder  37 . On the processing cylinder  37 , the sheet  2  is provided with three cuts  76 ,  77 ,  78  in the longitudinal direction—i.e. in the transport direction T—. Narrow strips  79 ,  81  are cut off the two longitudinal sides of the sheet  2  by the second and third cut  76 ,  77 . These cuts  76 ,  77 ,  78  and strips  79 ,  81  can be seen in FIG.  2 . 
     The gripper division or size of the gripper systems  39 ,  41 ,  42 ,  43  of the processing cylinder  37 , and the width, as well as the position, of the sheet  2 , are matched to each other in such a way that the two cut-off strips  79 ,  81  are not grasped by the grippers. 
     The fourth cut  78  separates the sheet  2  in the center into two partial sheets  82 ,  83 . Here, too, there is no gripper in the area of the cut  78 . 
     When these three longitudinal cuts  76 ,  77 ,  78  are completely performed, also at the maximum length of the sheet  2 , the two partial sheets  82 ,  83  are moved apart in the axial direction. To this end, in the present invention a gripper system  41 , or respectively  43 , or  39 , or respectively  42 , performs a lifting motion in the axial direction by means of a cam roller  45  working together with a cam disk  40 . Only after these two partial sheets  82 ,  83  have been moved away from each other are these two partial sheets  82 ,  83  passed on to a chain gripper system  49  of the second chain conveyor  47  in the area of the first chain wheel shaft  51 . The gripper system  41 , or respectively  43 , of the processing cylinder  37  is moved back into its initial position before the next sheet  2  is taken over. 
     The spaced-apart partial sheets  82 ,  83  are conveyed on in a common conveying direction, or respectively plane. 
     The two partial sheets  82 ,  83  are conducted to the second transverse cutting device  57  by this chain gripper system  49 . To steady the sheet  2 , it is aspirated along the suction box  56  which is connected upstream of the second transverse cutting device  57 , and the previously trimmed end  72  of the partial sheets  82 ,  83  in the chain gripper system  49  is already passed over the suction box  61  of the third inspection device  6 . From the untrimmed initial front  71  of the sheet  2 , i.e. of the two pulled-apart partial sheets  82 ,  83 , which now trails, a strip  86  is axially cut off at right angles in respect to the transport direction T by means of a fifth cut  84 . The sheet  2  has now been trimmed on all sides and has been separated into two partial sheets  82 ,  83 . 
     A back or reverse side of the sheet  2 , i.e. the backs of the two partial sheets  82 ,  83 , together with the edges trimmed in the longitudinal direction, and the now trailing front  71  of the sheets  2 , i.e. the trailing ends of the partial sheets  82 ,  83  trimmed in the axial direction, are checked by the third inspection device  6 . 
     The inspection devices  4 ,  6  check the cut registration of the sheets  2 ,  82 ,  83 , i.e. the position of at least one trimmed edge, preferably of all trimmed edges of the sheets  2 ,  82 ,  83  in relation to a reference marker, for example within a printed image. Preferably the entire sheets, including the entire printed image, are checked. 
     The chain conveyor  47  conveys the partial sheets  82 ,  83 , which have been trimmed on all sides and checked on front and back from the third inspection device  6 , to selected ones of the six stacks  63 ,  64 ,  66  to  69  of the feeder  62 . There, the partial sheets  82 ,  83  can be selectively deposited on one of the six stacks  63 ,  64 ,  66  to  69 . In this connection, the first four stacks  63 ,  64 ,  66 ,  67  preferably receive so-called “good” sheets, and the two last stacks  67 ,  68 , which are arranged next to each other, receive waste sheets. 
     In place of sheets  2 ,  82 ,  83 , it is also possible, for example, to trim or cut printed webs, i.e. printed materials, and to subsequently check them by means of one or several inspection devices  3 ,  4 ,  6 . In this case, the cutting devices  1 ,  38 ,  57  can be arranged, for example, in the area of a folding mechanisms of a web-fed rotary printing press. 
     There, a web is cut, for example in the longitudinal direction, into several partial webs, and is subsequently cut into signatures in the transverse direction. In this case, the cut registration can be checked after each step, or after the web has been cut completely into signatures. 
     The inspection devices  3 ,  4 ,  6  preferably contain one or several CCD area cameras, which check the sheet as a whole. 
     While a preferred embodiment of a sheet processing machine in accordance with the present invention has been set forth fully and completely hereinabove, it will be apparent to one of skill in the art that a number of changes in, for example, the type of printing press used with the sheet processing machine, the apparatus used to deliver and remove the sheet stacks 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 bey the following claims.