Patent Publication Number: US-6708612-B1

Title: Modular printing machine system for printing on sheets

Description:
BACKGROUND OF THE INVENTION 
     Field of the invention 
     The invention relates to a modular printing machine system for printing on sheets, comprising a first printing machine of satellite construction type, with a central first impression cylinder and at least four printing devices assigned thereto, a second printing machine, and a coupling device for coupling the printing machines with one another for in-line operation thereof. 
     In the published German Patent Document DE 197 43 770 A1, there is described such a system, which includes a satellite printing-unit group as the first printing machine, an imprinting-unit group as the second printing machine, and a connecting element as a coupling device. The imprinting-unit group includes a first and a second printing form, with which various imprints can be added to the four-color images printed in the satellite printing-unit group. The printing forms are one-time imageable printing forms, i.e., whereon printing images may be applied only once, assignable to the master system, the printing image being storable but not eraseable, the production of the printing image requiring an expenditure of a given length of time of, for example, twelve minutes. Therefore, with the system described in this German patent document it is not possible for each sheet to be printed by the system in a print job to be given a different, individual imprint, for example for the purpose of addressing, personalization or numbering. 
     The prior state of the art is described further in U.S. Pat. No. 5,660,108, and in the published German Patent Documents DE 43 03 797 A1 and DE 195 03 619 A1. 
     Advertising matter, for the production of which, printing machine systems of the foregoing general type are particularly well suited, often require such individual imprints, however, for example in order to address the addressee in the advertising matter personally. 
     In the published German Patent Document DE 197 04 003 A1 representing an even further state of the prior art, a description is given of a method for imprinting one of a multiplicity of individualizing identifications by a laser printer or ink jet printer in a sheet-fed printing machine. 
     The sheet-fed printing machine does not belong to a printing machine system with printing machines that are couplable together, and therefore cannot be used very variably. 
     SUMMARY OF THE INVENTION 
     In light of these inadequacies of the prior art, it is accordingly an object of the invention to provide a modular printing machine system for printing on sheets with which the sheets can be given individual imprints. 
     With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a modular printing machine system for printing on sheets, including a first printing machine of satellite construction type having a central first impression cylinder and at least four printing devices assigned thereto, a second printing machine, and a coupling device for coupling the printing machines to one another for in-line operation thereof, comprising a transport device of the printing machine system, for transporting the sheets, and a non-impact printer assigned to the transport device. 
     In accordance with another feature of the invention, the transport device is constructed for transporting the sheets along a linear transport path. 
     In accordance with a further feature of the invention, the transport device has at least one tongs-type gripper lying on a side of a sheet held in the tongs-type gripper for printing thereon by the non-impact printer, the tongs-type gripper having an ultra-flat construction so that, when the sheet is being transported past the non-impact printer, the tongs-type gripper is guidable collision-free through a narrow gap formed 
     In accordance with an added feature of the invention, the tongs-type gripper is less than 1.0 mm thick, more particularly, less than 0.5 mm thick. 
     In accordance with an additional feature of the invention, the transport device is a transport belt. 
     In accordance with yet another feature of the invention, the transport belt is a suction belt selected from the group consisting of suction belts formed of air-permeable material and of a material formed with air passages, respectively, the suction belt, in order to hold the sheet thereon, having a suction device assigned thereto for sucking the sheet against the suction belt. 
     In accordance with yet a further feature of the invention, the transport device is selected from the group consisting of electromagnetic linear drives and linear motors, respectively, and includes stators and at least one rotor, the rotor being constructed so as to carry the sheets, and the stators being disposed along a transport path of the sheets and being constructed to produce a traveling electromagnetic field for forwardly driving the rotor. 
     In accordance with yet an added feature of the invention, the transport device is constructed as a chain gripper formed of a chain and at least one gripper bar secured thereto. 
     In accordance with yet an additional feature of the invention, the non-impact printer is a printer selected from the group consisting of ink jet printers and laser printers, respectively. 
     In accordance with another aspect of the invention, there is provided a modular printing machine system for printing on sheets, including a first printing machine having a sheet feeder and being of satellite construction type with a central first impression cylinder and at least four printing devices assigned thereto, a second printing machine including a sheet delivery and a second impression cylinder, and a coupling device for coupling the printing machines to one another for in-line operation thereof, the second printing machine comprising a second impression cylinder, the first and the second impression cylinders being of different sizes. 
     In accordance with another feature of the invention, the modular printing machine system according to the other aspect of the invention comprises a transport device for transporting the sheets, and a non-impact printer assigned to the transport device. 
     In accordance with a concomitant aspect of the invention, there is provided a modular printing machine system for printing on sheets, comprising a first printing machine having a first impression cylinder, a second printing machine having a second impression cylinder, and a coupling device for coupling the first and the second printing machines to one another for in-line operation thereof, the first and the second impression cylinders being of different sizes. 
     Thus, the printing machine system according to the invention includes a transport device and a non-impact printer, which is arranged adjacent to the transport device. While the transport device transports the sheets past the non-impact printer, the latter can provide the sheets with individual imprinted motifs. For example, using the non-impact printer, each sheet of a print job, which includes many sheets successively passing through the printing machine system, can be provided with a different imprinted motif. 
     Other features which are considered as characteristic for the invention are set forth in the appended claims. 
     Although the invention is illustrated and described herein as embodied in a modular printing machine system for printing on sheets, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
     The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic and schematic side elevational view of a first embodiment of a modular printing machine system according to the invention; 
     FIG. 2 is a view like that of FIG. 1 of a second embodiment of the modular printing machine system according to the invention, which differs from the first embodiment; 
     FIG. 3 is a view like those of FIGS. 1 and 2 of a third embodiment of the modular printing machine system according to the invention, which differs from the first and the second embodiments; and 
     FIG. 4 is a view like those of FIGS. 1,  2  and  3  of a fourth embodiment of the modular printing machine system according to the invention, which differs from the first, second and third embodiments. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to FIGS. 1 to  4  of the drawings, there is shown therein a first printing machine  1  which, in order to form a modular printing machine system  2  to  5 , respectively, can selectively be coupled to a second printing machine  6  (note FIG.  1 ), to a second printing machine  7  (note FIG.  2 ), to a second printing machine  8  (note FIG. 3) or to a second printing machine  9  (note FIG.  4 ), and which includes a sheet feeder  10  and a sheet delivery  11  and all the further subassemblies needed for a separate operation from the respective second printing machine  6 ,  7 ,  8  or  9 . 
     In addition, the first printing machine  1  includes a common impression cylinder  12 , around which four printing devices  13  to  16  are arranged, by which a sheet  17  lying on the impression cylinder  12  is printed successively with the colors black, cyan, magenta and yellow in the offset process, preferably using dry offset, i.e., without dampening solution. Each of the printing devices  13  to  16  includes a form cylinder  18  and an applicator cylinder  19 , whereon a rubber blanket is mounted and serves for transferring the respective ink from the form cylinder  18  to the sheet  17 . The circumference of the impression cylinder  12 , which is equipped with four rows of grippers, is four times as large as the circumference of the form cylinder  18 , and also four times as large as the circumference of the applicator cylinder  19 . Each form cylinder  18  has a laser source assigned thereto as an imaging device  20  for forming an image thereon, an operation which is performed within the printing machine  1  by laser radiation, and an inking unit  21  for inking during the printing. The first printing machine  1  may be a machine of the “Quickmaster DI 46-4” type produced by Heidelberger Druckmaschinen AG. 
     Each of the second printing machines  6  to  9  includes a sheet delivery  21  to  24  with a chain gripper, is also equipped with a chassis or undercarriage  25  to  28  which is withdrawable if necessary, and has two side walls with a thickness and distance from one another corresponding to those of the first printing machine  1 , so that the second printing machine  6  to  9  can be docked without difficulty with and onto the first printing machine  1 . 
     The second printing machines  6  and  7  are constructed as varnishing machines and, respectively, include an impression cylinder  29 ,  30  with grippers and, respectively, an applicator cylinder  31 ,  32 . In order to feed varnish, a roller engages the applicator cylinder  31  and, serving as a metering roller  33 , together with a dip roller  35  that scoops the varnish out of a trough  34 , forms a metering device  36  for producing a uniform film of varnish over the printing width. The second printing machine  7  also has such a zoneless metering device  37 , which, in an anilox construction type, includes a screen roller  38  rolling on the applicator cylinder  32  and a doctor blade  39  formed as a chamber-type doctor blade and engaging the screen roller  38 . The circumferential length of each cylinder  29  to  32  and of the screen roller  38  corresponds to that of the form cylinder  18 . On each of the applicator cylinders  31  and  32 , a rubber blanket  40  for varnishing the entire area of the sheet  17 , or a flexographic printing form  41  for spot varnishing can selectively be spread. In the latter case, the applicator cylinder  31 ,  32  is a form  20  cylinder. Of course, a special ink can be printed with each second printing machine  6  and  7  instead of the varnish. 
     The second printing machine  8  is a slightly modified single-color printing machine of the “Printmaster QM 46-1” type, and the second printing machine  9  is a slightly modified two-color printing machine of the “Printmaster QM 46-2” type, which are produced by Heidelberger Druckmaschinen AG. The aforementioned machine types can also form the basis for the second printing machines  6  and  7 ; the modifications which would have to be performed for this purpose would then be somewhat more extensive. 
     Each of the second printing machines  8  and  9  includes an applicator cylinder  42 ,  43  which, as a blanket cylinder, transfers the ink from at least one printing form cylinder  44 ,  45 ,  46  to the sheet  17  lying on an impression cylinder  47 ,  48  in the offset process. The applicator cylinder  43  operates as a collecting cylinder together with the two printing form cylinders  45  and  46 , in that the rotating applicator cylinder  43 , respectively, successively picks up a special ink from the printing form cylinders  45  and  46  rolling thereon and then applies the two special inks at the same time to the sheet  17 . Each printing form cylinder  44  to  46  has a dampening unit  49  to  51  assigned thereto for dampening purposes, and an inking unit  42  to  54 , constructed as a vibrator-type inking unit, for inking it. The respective dampening unit  49  to  51  can be dispensed with in the case of a second printing machine  8 ,  9  that operates in the dry offset process. Each printing form cylinder  44  to  46  can have a laser source assigned thereto as an imaging device  55  to  57  for the purpose of forming an image thereon within the second printing machine  8  and  9  by laser radiation. The printing form cylinder  46 , the inking unit  54 , if appropriate the dampening unit  51  and if appropriate the imaging device  57  are mounted between side plates which are separate from the side walls of the printing machine  9  but correspond to the latter in terms of distance and thickness and, together, constitute a structural unit in the form of a printing module  58 , which may be placed on the side walls. 
     Except for the printing module  58 , the second printing machines  8  and  9  are identical to one another. By omitting the printing module  58 , the second printing machine  9  can be converted to a single-color printing machine, which corresponds to that shown in FIG.  3 . By adding the printing module  58 , the second printing machine  8  can be converted to a two-color printing machine, which corresponds to that shown in FIG.  4 . As a result of this building-block system, the manufacturer&#39;s production costs can be kept low. 
     In order to provide the sheets  17  with imprints that can be varied from sheet to sheet during continuous operation of the machine, for example continuous numbering or codes, an imprinting unit  59  with a stamping shaft  60  can be integrated into both the second printing machine  8  and the second printing machine  9 , as is illustrated by using the second printing machine  8  as an example. 
     In order to dry the sheet  17  before it is delivered by the sheet delivery  21  or  23 , a dryer  61  can also be integrated, instead of the single printing unit  59 , into each of the aforementioned second printing machines  8  and  9 , as is illustrated by the use of the second printing machine  9  as an example. 
     A dryer  62  to  65  can likewise be integrated into the sheet delivery  21  to  24  of the second printing machine  6  to  9 , the dryer  62  to  65  being arranged between the two runs or strands of the chain gripper of the respective sheet delivery  21  to  24 . The dryer  62  to  65  is assigned to the lower run or strand, which conveys the sheets  17  and from which the sheets  17  are allowed to fall onto a sheet pile belonging to the respective sheet delivery  21  to  24 . The dryer  62  to  65  acts upon the front side of the sheet  17  freshly printed in the second printing machine  6  to  9  while the sheet is being transported past the dryer  62  to  65  by the chain gripper. 
     For the purpose of transporting sheets from the first printing machine  1  into the respective second printing machine  6  to  9 , a feeding device  66  to  69  and a modular transport device  70  to  73  are installed between the sheet delivery  11  of the first printing machine  1  and the second impression cylinder  29 ,  30 ,  47  or  48  of the second printing machine  6  to  9 . Each of the transport devices  70  to  73 , which are described in greater detail hereinbelow, can be installed instead of each of the other transport devices  70  to  73 . For example, the transport device  70  can also be integrated, instead of the transport device  71 , into the printing machine system  3 . The feeding devices  66  to  69  are identical with one another. 
     Each transport device  70  to  73  is arranged between the first impression cylinder  12  and the respective second impression cylinder  29 ,  30 ,  47  or  48  to transport the sheets from the impression cylinder  12  to the second impression cylinder  29 ,  30 ,  47  or  48 , and is constructed to transport the sheets  17  along a linear transport path  74  to  77 . 
     An electric motor drive  118  which drives the first printing machine  1  and, in particular, the rotating system of the first impression cylinder  12  and the revolving system of the sheet delivery  11 , a drive  119  which drives the second printing machine  6  to  9  and, in particular, the rotating system of the second impression cylinder  29 ,  30 ,  47  or  48 , and an electric motor drive  120  which drives the transport device  70  to  73  and, in particular, the revolving system thereof, are linked to an electronic control device  121  and, via the latter, are linked to one another, in terms of control technology, for the synchronization of the drives  118  to  120 , as is shown by way of example in the printing machine system  3  in FIG.  2 . In order to prevent the gripper bars  89  and  90  of the transport device  71  from colliding with the delivery gripper bars, even in the case of accidents and, for example, in the event of failure of the control device  121 , formlocking or positive forcible control is provided in the form of a gear mechanism  122  linking the transport device  71  with the sheet delivery  11 , the gear mechanism  122  having one gearwheel assigned to the sheet delivery  11  and, for example, arranged coaxially with the chain sprocket  116 , and having another gearwheel assigned to the transport device  71  and arranged, for example, coaxially with the chain sprocket  87 , the two gearwheels having an increased tooth clearance with respect to one another and coming into tooth-flank contact with one another only in the event of an accident. 
     The transport device  70  to  73  has a non-impact printer  78  to  81  assigned thereto and, following the latter in the sheet transport direction, a dryer  123  to  126 . The non-impact printer  78  to  81  prints the sheet  17 , and the dryer  123  to  126  dries the sheet  17 , while the latter is transported by the transport device  70  to  73  along the transport path  74  to  77  and past the non-impact printer  78  to  81  and past the dryer  123  to  126 . The non-impact printer  78  to  81  is preferably an ink jet printer, having nozzles from which droplets of ink are expelled by piezoelectric pumps. 
     Each of the dryers  61  to  65  and  123  to  126  may be an IR (infrared radiation) dryer, a UV (ultraviolet radiation) dryer and, in particular, a so-called UV excimer dryer, which operates without forming any ozone and, with the monochromatic UV radiator thereof at  308  and  222  nanometers light wavelength, respectively, does not emit any heat radiation. Such a UV excimer dryer has become known heretofore, for example, from the publication “Druckwelt” (Printing World), March 1999 Issue, and was developed, for example, by the Sächsisches Institut der Druckindustrie [Saxon Institute for the Printing Industry] (SID), Leipzig, Germany, based upon blue-light modules with mercury-free UV radiators from the firm Heraeus Noblelight GmbH, Kleinostheim, Germany. 
     The dryers  123  to  126  are provided for drying the ink-jet ink printed by the non-impact printer  78  to  81 , which can also be a UV-curable ink, the drying being rapid and essentially completed before the sheet  17  is printed or varnished in the second printing machine  6  to  9 . The dryers  61  to  65  are provided for drying the entire sheet  17  before it is delivered into the sheet delivery  21  to  24 . 
     Instead of the ink jet printer, a laser printer can often also be provided as the non-impact printer  81  to  84 , in which cases the dryer  123  to  126  may be dispensed with. 
     The advantage of the non-impact printer  81  to  84  over an imprinting unit which is mechanically connectable, such as the imprinting unit  59 , is that, by using the non-impact printer  81  to  84 , addresses, personalizations and virtually all conceivable motifs can also be printed onto the sheet  17 , it being possible for the type and sequence of the motifs to be updated during the uninterrupted running of the printing machine system  2  to  5 . In the imprinting unit  59 , the type, the number and the sequence of the motifs, which can be continuous numbering, codes and the like, for example, here, are predetermined by the form and indexing of the stamps or punches, or numbering wheels used in the imprinting unit  59 , which can be replaced only when the machine is at a standstill. 
     The transport device  70  is constructed as an electromagnetic linear drive and linear motor, respectively, which comprises stators  82  and  83  and at least one rotor  84  and  85 , the rotor  84  and  85  being equipped with at least one otherwise non-illustrated sheet holding element for carrying the sheets  17 , and the stators  82  and  83  being arranged along the transport path  74  of the sheets  17  and being constructed so as to produce a traveling electromagnetic field for driving the rotor  84  and  85  forward. 
     The transport device  71  is constructed as a chain gripper, which is formed of a linked chain  88  revolving about two shafts provided with chain sprockets  86  and  87 , at least one gripper bar  89 ,  90  carrying the sheet  17  is fastened to the chain  88 . 
     The transport device  72  is a suction belt that revolves around two shafts  91  and  92 , is formed of an air-permeable material or is provided with air passages and, in order to hold the sheet  17  on the suction belt, the latter has a pneumatic suction device  93  assigned thereto which attracts the sheet  17  by suction through the suction belt. 
     The transport device  73  is a transport belt, which revolves around two shafts  94  and  95 , and has at least one tongs-type gripper  96 ,  97  for holding the sheet  17 , the tongs-type gripper  96 ,  97  lying on that side of the thereby held sheet  17  which is to be printed by the non-impact printer  84  and, because of the ultra-flat construction thereof, as the sheet  17  is being transported past the non-impact printer  84 , the tongs-type gripper  96 ,  97  is guidable without collision through a narrow gap  98  formed between the non-impact printer  84  and the sheet  17 . Each tongs-type gripper  96 ,  97  moving relative to a gripper pad in order to clamp the sheet and clamping the sheet between itself and the gripper pad, is less than 1.0 mm thick, in particular less than 0.5 mm thick, and thus projects barely in the direction of the non-impact printer  84 . 
     In addition, each gripper bar  89 ,  90  of the transport device  71 , and each rotor  85  and  85 ′ of the transport device  70 , can be equipped with such an ultra-flat tongs-type gripper  99  to  102  as a sheet-holding element. 
     The feeding device  66  to  69  accepts the sheet  17  from the respective transport device  71  to  73 , which in turn accepts the sheet  17  from the sheet delivery, which is constructed as a chain gripper revolving around chain sprockets  116  and  117  and provided with otherwise non-illustrated delivery gripper bars. The feeding device, which serves to transfer the sheet to the second impression cylinder  29 ,  30 ,  47  or  48  and is constructed as a feed drum, has at least one adjusting or actuating device  103  to  105  assigned thereto. 
     In order to simplify the following explanations, like reference characters are used in FIGS. 1 to  4  for sensors, electronic control devices and the adjusting or actuating devices which are constructionally and functionally identical in all the printing machine systems  2  to  5 . 
     The first impression cylinder  12  has at least one sensor  106  to  108  assigned thereto for monitoring the position of a sheet  17  transported by the impression cylinder  12 , and the feeding device  66  to  69  has at least one further sensor  109  to  110  assigned thereto for monitoring the position of the sheet  17  to be transferred from the feeding device  66  to  69  to the second impression cylinder  29 ,  30 ,  47  or  48 . The at least one sensor  107  and  108  and the at least one further sensor  109  and  110  are arranged to monitor the position of a leading edge of the sheet and, via an electronic control device  112 , are linked to the adjusting or actuating device  103  that is used to adjust the circumferential register of the feeding device  66  to  69 . If only a single sensor  107  and  109  is assigned to the first impression cylinder  12  and the feeding device  66  to  69 , respectively, for monitoring the circumferential register, then the sensor, respectively, is situated in the vicinity of the center of the format width of the leading edge of the sheet  17  passing by the sensor  107  and  109 . 
     The sensors  107  and  108  are preferably arranged offset from one another in the axial direction of the first impression cylinder  12 , and form a first pair of sensors, and the sensors  109  and  110  are likewise preferably arranged offset from one another in the axial direction of the feeding device  66  to  69 , and form a second pair of sensors. In terms of their pairwise arrangement, the sensors  107  to  110  are not arranged in the vicinity of the center of the sheet but, as a function of the format, adjustably close to the side edges of the sheet, so that the sensors  107  and  109  register the leading edge close to one side edge of the sheet, and the sensors  108  and  110  register the leading edge close to the other side edge of the sheet. The sensor pairs can be used not only to monitor the circumferential register but, alternatively or additionally, also to monitor the diagonal or skew register. In this case, each of the four sensors  107  to  110  is linked via the electronic control device  112  to the adjusting or actuating device  104  serving to adjust the diagonal register of the feeding device  66  to  69  and, with simultaneous monitoring of the circumferential register, also linked to the adjusting or actuating device  103 . 
     In addition, an incremental encoder  113  for registering the machine angle of the first printing machine  1 , i.e., the rotary angle position of the rotating first impression cylinder  12 , is linked to the electronic control device  112  and, via the latter, to the sensors  107  to  110 . 
     If the control device  112  establishes that there are deviations between the register values from the pair of sensors  107  and  108  or from the single sensor  107  in relation to the pair of sensors  109  and  110  or the single sensor  109 , the control device  112  controls the adjusting or actuating device  103  in a manner that the circumferential register of the feeding device  66  to  69  is displaced in the circumferential direction of the feeding device  66  to  69 , corresponding to a register-maintaining setting. If the control device  112  establishes that the monitored values from the pair of sensors  109  and  110  deviate from the monitored values of the pair of sensors  107  and  108 , the control device  112  controls the adjusting or actuating device  104  in a manner that the diagonal register of the feeding device  66  to  69  is set in a register-maintaining manner by changing the skew setting or parallel setting thereof. 
     The sensors  106  and  111  are arranged so as to monitor the position of one side edge of the sheet  17 , and are linked via the electronic control device  112  to the adjusting or actuating device  105  serving to adjust the lateral register of the feeding device. The sensor  106  measures the position of the sheet  17  on the first impression cylinder  12  in the axial direction of the latter, and signals the measured position to the control device  112 . The sensor  111  likewise measures the lateral position of the sheet  17  on the feeding device  66  to  69  and, in turn, signals the measured position to the control device  112 , which, in the event of a deviation of the value measured by the sensor  111  from the value measured by the sensor  106 , controls the adjusting or actuating device  105  that serves to adjust the lateral register of the feeding device  66  to  69  in a manner that, by displacing the feeding device  66  to  69  axially, the lateral register thereof is adjusted. 
     The adjustment of the feeding device for correcting the circumferential, diagonal or lateral register is performed only after the trailing edge of the sheet transported by the feeding device  66  to  69  during the displacement thereof has passed by the non-impact printer  81  to  84 , and this sheet is no longer being printed by the non-impact printer  81  to  84 . 
     This reliably avoids any distortion of the image printed on the sheet by the non-impact printer  81  to  84  due to the premature displacement of the sheet relative to the yet-printing non-impact printer  81  to  84  by the feeding device  66 . 
     Each of the sensors  106  to  111  is constructed as an optical sensor in the form of a so-called CCD (charge coupled device) line. 
     Instead of directly monitoring the position of the sheet leading edge or the sheet lateral edge by the respective sensor  106  to  111 , register marks, for example register crosses, can be printed in the first printing machine  1  with the applicator cylinder  19  onto the printed image-free sheet margins located at the edge of the sheet, the position of which is registered by the respective sensor  106  to  111 , by which the position of the edge of the sheet is monitored indirectly. 
     After the register corrections described hereinabove have been performed, the feeding device  66  to  69  transfers the sheet  17 , which has been printed in-register on the first impression cylinder  12 , the register-maintenance of the sheet  17  having from time to time been lost due to the sheet transfer from the sheet delivery  11  to the transport device  70  to  73  at a separating location  115 , to the second impression cylinder  29 ,  30 ,  47  or  48 , again while maintaining register. 
     Due to possible wear and necessary play in a coupling device  114 , one cannot rule out that the respective second printing machine  6  to  9 , each time it is coupled to the first printing machine  1 , will be offset slightly relative to the latter, by a different amount. This offset manifests itself at the separating location  115 , at which the respective transport device  70  to  73  accepts the sheets  17  from the sheet delivery  11 , and at which the second printing machine  6  to  9  can be separated from the first printing machine  1 . In other words, the sheet delivery  11  transfers the sheets  17  more-or-less in-register to the respective transport device  70  to  73 , depending upon the magnitude of the offset. 
     The possibly inaccurate transfer register between the first printing machine  1  and the second printing machine  6  to  9  is advantageously compensated for by appropriate displacement of the feeding device  66  to  69 , so that the sheet  17  is in turn transferred with accurate register from the feeding device  66  to  69  to the respective second impression cylinder  29 ,  39 ,  47  or  48 .