Patent Publication Number: US-2007101880-A1

Title: Printing line with a web storage unit and post-processing system

Description:
BACKGROUND  
      The preferred embodiment concerns a printing line with a first printer that prints print images on a continuous first web, at least one second printer that prints print images on a continuous second web, and with at least one post-processing system which post-processes the printed webs. The preferred embodiment also concerns a method for operation of a printing line.  
      In addition to a printing system, conventional printing lines comprise a complex post-processing system that cuts, folds and sorts the printed paper (in the form of a continuous web), binds it into books or brochures and/or franks it. For economic reasons, the apparatuses and mechanisms belonging to the post-processing system are connected in series and operation in the same time as the upstream printing system. A cycle shortening and a simplified operation of the post-processing system is thus achieved. In practice, different process speeds result for the mechanisms of the post-processing system and for the printer or printers, such that a mismatch results given the serial passage of the printing material. Downtimes of individual components of the overall system can also lead to a material jam occurring in the pass operation.  
      Given the coupling of mechanisms of post-processing systems with modern digital printers, it is frequently determined that the capacities are not attuned to one another. Mechanisms or apparatuses of a post-processing system are typically designed for process speeds greater than 4 to 5 m/sec, while the digital printers with high print quality typically have a process speed of 1 to 2 m/sec. Due to this mismatching in terms of the process speeds, the cycle speed that can be achieved with conventional post-processing systems cannot be fully utilized. Higher process speeds with digital printers can be achieved in principle; however, an over-proportionally high technical effort is required for this, for example in the associated preparation of the digital data. On the other hand, due to the necessary stable mechanical design and the high degree of automation of the components, the achievement of the cited high process speed with relatively little technical effort is possible in the apparatuses of the post-processing system. A reduction of the capacity of these apparatuses would thus hardly be economically advantageous.  
      A printing system with at least three printing devices as well as a method for operation of such a printing system is known from U.S. Pat. No. 6,381,440 by the same applicant (parallel European patent application EP-A-1 202 134). A first printer prints the front side of a paper web. The back side of this paper web is printed in a second printer and this back side is printed with a further color overcoat in a third printer. It is possible to arrange this printing line comprised of three printers twice, such that the entire printing system then comprises six printers, whereby a high capacity is achieved. Nevertheless, given connection to a post-processing system a significant mismatching can occur in terms of the process speed.  
      A printing system and printing method for generation of a color mixed sheet sequence is described from U.S. Pat. No. 6,363,231 by the same applicant (parallel PCT patent application WO 99/09459). The entire system for printing of single sheets comprises a digital printer operating with a high speed, which digital printing generates monochrome print images or print images with two colors. A digital color printer is also provided that is coupled with the aforementioned printer via a paper path coupling module. A superordinate control unit allocates the single sheets to be printed to the printing groups, which single sheets are collected in a common sheet collection direction in order to then be transported further to a post-processing system. A high-capacity printing with more than 70 pages per minute can be achieved with the aid of this printing system with a plurality of printers.  
      A device for buffering of web-shaped material is known from WO 97/35797. The device comprises a rotatably borne, hollow outer coil body processing system accesses the at least one printed web stored in the web storage unit. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  shows a printing line with two printing systems and a loop storage as a web storage unit;  
       FIG. 2  shows a printing line in which the web storage unit comprises two cage storages;  
       FIG. 3  shows a printing line in which the web storage unit comprises three roller units;  
       FIG. 4  shows a printing line with five identical roller units; and  
       FIG. 5  shows a printing line in which the web storage unit comprises three roller units that have a common bearing shaft. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
      For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the preferred embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and/or method, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur now or in the future to one skilled in the art to which the invention relates.  
      According to the preferred embodiment, the printer (which prints a continuous web) is not directly coupled with the post-processing system; rather, the continuous web is initially conveyed into a web storage unit and buffered there. In this manner it is possible to arrange a plurality of printers that feed the webs printed by them to the web storage unit. The volume of printed material then present in the web storage unit is relatively high and can be output to the post-processing system with an increased speed relative to the printing speed of an individual printer. This increased output speed is Due to the decoupling of the digitally-operating printer from the components of the post-processing system, the one or the other component of the printing line can be exchanged during the overall service life without reducing the efficiency of the overall printing line. For example, further-developed individual components can thus be incorporated into the overall printing line in a simple manner.  
      A further advantage arises due to the fact that printers and apparatuses of the post-processing are differently prone to interference. Due to a decoupled production in the printing line, the availability of individual components does not necessarily limit the capacity of the entire printing line. For example, the repair times or other downtimes can also be bypassed without performance loss or loss of efficiency.  
      A further advantage results in that, given a failure of a printer, a printing reserve is still present due to the decoupling of the printer from the post-processing system. The overall printing line can thus then produce further with reduced capacity given failure of a printer.  
      Another advantage results in that a reserve can be produced due to a longer operating duration of a printer or of a plurality of printers. This reserve can be buffered in the web storage unit and be further processed by the post-processing system at a later point in time. Given digitally-operating printers, it cannot always be guaranteed that the available data can be printed without further measures. For example, the fonts required in the print job can not be available or a specific color is required in the print job that is not immediately available in the current printer. An operating personnel must then in fact take corresponding measures, for example select a different font or download the correct font via software; furthermore, he can exchange the color station or select another color. These measures are typically always connected with production interruptions. When a plurality of printers are now present or a corresponding reserve of printed paper has been produced in reserve, this time in which this reserve is further-processed by the post-processing system can thus be used to execute such measures without the overall productivity of the printing line suffering from them.  
       FIG. 1  shows a printing line that contains two printing systems  10 ,  12 . The first printing system  10  is executed as a tandem system and comprises two printers  14 ,  16  that either print two color separations on the same side of the continuous web  18  in the operating mode “spot color printing” or print the front side and back side of the continuous web  18  in the operating mode “duplex printing”. The continuous web  18  is unrolled from a roll  20  that is borne in a roller unit  22 .  
      The other printing system  12  is designed as a digital duplex printing system and prints on both sides a continuous web  24  that is unrolled from a roll  26  and is supplied to the printing system  12  via the roller unit  28 . The printed continuous webs  18 ,  24  are supplied to a unit generally designated as a web storage unit  30 . This web storage unit  30  comprises a first loop storage  32  and a second loop storage  34 . Each of the loop storages  32 ,  34  (which are known in the field of paper processing) comprises a plurality of rollers between which the continuous web material input is stored in a meandering manner. The loop storages  32 ,  34  operate as FIFO storages (first-in first-out) and supply the respective continuous web  18 ,  24  to a cross table  36  from which the selected web  18  or  24  is specifically transported further to a post-processing system  40 . This post-processing system  40  can comprise components such as a cutting system, a folding system, a sorting system, a bookbinding system and/or a franking system.  
      In the arrangement shown in  FIG. 1 , the printed matter in the form of the continuous web  18  or the continuous web  24  can selectively be supplied from one of the loop storages  32  or  34  to the post-processing system via the cross table  36  while printed web material can furthermore be conveyed into the respective other loop storage.  
       FIG. 2  shows a further example of an arrangement of a printing line, whereby identical parts are designated identically. Here the web storage unit  30  comprises two cage storages  42 ,  44  that operate as FIFO storages. Each cage storage  42 ,  44  stores the continuous web  18  or  24  supplied to it and outputs the respective continuous web  18 ,  24  via a cross table  36 . The design of the cage storages  42 ,  44  is described in the aforementioned WO 97/35797 by the same applicant. This document is incorporated by reference into the disclosure of the present patent application.  
      An adhesion unit  46  with whose help the end of a printed continuous web  18 ,  24  connected with the beginning of the subsequently printed continuous web  18 ,  24  is downstream from the cross table  36 .  
      The printed matter can be conveyed from one of the two cage storages  42 ,  44  to the post-processing system  40  via the cross table  36 , during which printed material is buffered in the respective other storage.  
       FIG. 3  shows a further arrangement in which the web storage unit  30  comprises one roller unit  50 ,  52  per printer  10 ,  12 . The continuous web  18  or  24  is wound into rolls on these roller units  50 ,  52 . Furthermore, an additional roller unit  54  is provided that is arranged in the reverse direction and serves to unroll an already-printed continuous web from the roll. The roller units  50 ,  52 ,  54  are similarly designed and equipped with a sub-surface drive that comprises cylinders arranged below on which the rolls rest, which rolls are driven by these cylinders given winding and unwinding. The roller units  50 ,  52 ,  54  align with regard to the roller axis, such that a simple change of the roll from the roller units  50  and  52  to the roller unit  54  is possible. For this the corresponding roll is axially shifted from the roller unit  50  or  52  into the roller unit  54  while one of the printers  10 , 12  further prints the other continuous web, and is wound by one of the roller units  50  or  52 . The roll change can thus occur both manually and automatically. An interruption-free printing operation of the post-processing operation is possible with the aid of the illustrated arrangement.  
       FIG. 4  shows a further variant of a printing line in which the web storage unit  30  likewise comprises three roller units  60 ,  62  and  64 . The middle roller unit  64  operates in the unwinding direction while the roller units  60 ,  62  operate in the winding direction. The roller units  60 ,  62 ,  64  are similar to the roller units  66 ,  68  that feed the continuous webs  18 ,  24  to the printing systems  10 ,  12 , whereby an increased efficiency is provided. The roller units  60  through  68  are equipped with a surface drive, whereby a simple roll change from the roller units  60 ,  62  to the roller unit  64  for unwinding is possible. The respective roll is only axially shifted into the roller unit  64  for the post-processing while the non-participating roller unit  60 ,  62  furthermore winds printed material that is printed by the active printing system  10  or  12 . The respective other printing system is briefly stopped given the roll change.  
       FIG. 5  shows a further exemplary embodiment of the printing line. Per printing system  10 ,  12  the web storage unit  30  comprises one roller unit  70 ,  72  for winding up the continuous webs  18 ,  24 . An additional roller unit  74  serves for unwinding of full rolls. The roller units  70 ,  72 ,  74  have a common base frame  76  and a common bearing shaft  80  on which the respective rolls can be wound and unwound. The rolls are borne such that they can be shifted in the axial direction on the bearing shaft  80 , whereby a shifting from the winding position to the unwinding position can be easily realized. This roll change can occur both manually and automatically. The outer roller units  70 ,  72  possess a central drive, a sub-surface drive or a surface drive for winding the rolls. The middle roller unit  74  advantageously possesses a surface drive or a sub-surface drive.  
      An electrical control unit (not shown) is provided to control the printing line according to the exemplary embodiments of  FIGS. 1 through 5 . During the printing with the printing systems  10 ,  12 , the print pages are counted so that the print pages are known before the adhesive joining and after the adhesive joining into bound webs. This information is forwarded to the post-processing system  40  in order to insert the required blank pages there. Print products such as books, catalogs can be produced nearly without spoilage in this manner with the shown printing lines.  
      The shown exemplary embodiments can be modified in many cases. Instead of the shown printing systems  10 ,  12 , the printers cited in the aforementioned documents U.S. Pat. No. 6,381,440 or U.S. Pat. No. 6,363,231 can also be used. More than two printing systems can also be provided, whereby the storage elements in the web storage unit  30  are to be correspondingly adapted.  
      A further web storage in which a section of a printed continuous web is buffered can be provided before the post-processing system  40  in the processing direction. The post-processing system  40  can be supplied with web material from this web storage while a gluing process occurs, for example in a gluing station  46 .  
      While a preferred embodiment has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention both now or in the future are desired to be protected.