Abstract:
A printer or copier includes a high speed monochrome or two color printer portion and a slower full color printer portion. Print job signals are divided into monochrome and color printed pages and sent to the corresponding printer portion. The printers, or a paper handling path between the printers, is controlled to assemble the printed pages into a predetermined sequence order.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is directed to a printer or copier device system for performance-adapted production of a predetermined sheet sequence of monochromatically and/or chromatically printed single sheets, and is also directed to a printing method for producing a monochrome and chromatic sheet sequence. 
     2. Description of the Related Art 
     There is the problem in electrophotographic color printers having high print quality as known, for example, from European Patent Document EP-A1-0 629 931 that the same time is always required for producing a printed sheet both in monochrome printing mode as well as in chromatic printing mode. This means that what is referred to as the performance, i.e. the speed efficiency of the printer, is based on the full-color printing. When such a printer is utilized in mixed mode, then it is too slow for the usually occurring monochrome printing. 
     In electrophotographic high-performance printing with 70 pages per minute or more, the print jobs to be processed contain a majority of monochrome printouts. Only a small part of the print job is chromatic. For example, it can thus occur that a multitude of black-and-white successive sheets are printed within a print job and that one full-color image must be printed out then, for example when producing a brochure. When the usual color printing devices are utilized when producing such a brochure, these are relatively slow since, as already stated, the printing performance is based on the color printing performance. Such color printer devices are also complicated and cost-intensive and inefficiently utilized for mixed mode. 
     Color printer devices with which single-color or two-color printing can be carried out at high speed are disclosed, for example, by U.S. Pat. No. 5,526,107. In the known color printing means, continuous form paper is supplied to a transfer printing location of a photoconductor cylinder that respectively comprises electrophotographic units on two surfaces for producing multi-colored toner images. The continuous form paper is printed on the front side with a first color at the transfer printing location; the continuous form paper is subsequently redirected and supplied to a printing location at the same photoconductor cylinder that lies opposite the transfer printing location and the backside is printed thereat. 
     U.S. Pat. No. 5,596,416 discloses a printer device wherein a plurality of identical color printer means are arranged. Each of the color printer means is suited for monochromatic and color printing, whereby a parallel processing of images to be printed is possible. 
     What all of the known color printer devices have in common is that their performance is based on the color printing and, therefore, that the printer devices are uneconomically utilized for the mixed mode. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to offer a multi-color printer or copier device system having high printing performance that is especially suited for the mixed mode and whose performance is based on the maximum printing performance in the monochromatic mode. 
     This and other objects are achieved by the inventive method of producing a predetermined sheet sequence of single sheets printed monochromatically and/or multi-colored in a printer or copier system, including 
     a) printing a first sequence of recording media at a first speed on one side or both sides monochromatically or in two colors in a monochromatic or highlight printer unit with appertaining paper transport channel that can be individually driven and is fashioned as an independent structural unit; 
     b) printing a second sequence of recording media on one side or both sides in full color in a color printer unit with appertaining paper transport channel that is individually drivable and fashioned as an independent structural unit, being printed with a second, lower speed compared to the first speed; 
     c) the first and/or the second sequence of recording media being accepted by a paper path coupling module connectible to the paper transport channels of the monochromatic or highlight printer unit and of the color printer unit; 
     d) producing the sheet sequence of the recording media from the first and from the second sequence of recording media and supplying the sheets to a shared sheet collector and/or post-processor in a predetermined sequence; and 
     e) separating incoming print data into monochromatic and color printjob data with a synchronous control and communicating the respective print job data to the corresponding printer units. The objects are the invention are provided as well as by the printer or copier system for producing a predetermined sheet sequence of single sheets printed monochromatically and/or in full color, the system including: 
     a) an individually drivable monochromatic or highlight color printer unit with an appertaining paper transport channel fashioned as an independent structural unit for single-sided or both-sided printing of a first recording medium as a monochrome or as highlight color print with a first speed; 
     b) an individually drivable color printer unit with an appertaining paper transport channel fashioned as an independent structural unit for single-sided or both-sided, full-color printing of a second recording medium with a second, lower speed compared to the first speed; 
     c) a paper path coupling module connectible to the paper transport channels of the monochromatic or highlight color printer unit and to the color printer unit that accepts the printed first and/or second recording media and supplies them to a shared sheet collecting means and/or post-processing means for the sheet sequence; and 
     d) a synchronous control means connected to the monochromatic or highlight color printer unit and to the color printer unit, with which incoming print data can be separated into monochromatic and color print job data and the respective print job data can be communicated to the corresponding printer units. Advantageous embodiments of the invention are provided by the method above, whereby the sequence of the recording media in the sheet sequence is predetermined by a print data stream that contains monochromatic data and/or highlight data on the one hand and, on the other hand, color data, whereby the monochrome data or the highlight color data are supplied to the monochromatic or highlight printer unit and the color data are supplied to the color printer unit, and the sheet sequence is produced by an electronic controller according to the print data stream. The printer units and the paper path coupling module are driven time-organized by a synchronous control means, taking the printing speeds of the printer units and the sequence of the sheet sequence into consideration, such that the production of the sheet sequence ensues speed-optimized given largely parallel operation of the printer units. The recording media are printed in advance in the color printer unit, are then stored in a buffer store and are supplied time-exactly into the sequence of the recording media of the monochromatic or highlight color printer unit. 
     In the printer or copier system above, the monochromatic or highlight color printer unit may be a single sheet printer unit, and whereby the sequence of recording media from the color printer unit can be supplied into the output region of the monochromatic or highlight printer unit. The sheet sequence from the output region can be optionally supplied to a device output or to an internal stacking means of the device. The synchronous control controls the printer units and/or the paper path coupling module taking the printing speeds of the printer units and the sheet sequence into consideration, such that the production of the sheet sequence ensues speed-optimized given far-reaching utilization of a parallel operation of the printer units. In a preferred embodiment, the synchronous control is connected to the paper path coupling module and/or to a print data source. The sequence of the recording media from the color printer unit can be supplied into the input region of the monochromatic or highlight color printer unit. 
     At least one transfer printing station, an appertaining transfer printing transport path and a special paper path is provided in the monochromatic or highlight color printer unit via which sheets can be transported directly from the input region to an output region bypassing the transfer printing stations and/or the transfer printing transport path of the monochromatic or highlight color printer unit. The synchronous control comprises a device controller of the monochromatic or highlight color printer unit and a device controller of the color printer unit that may be coupled to one another according to the master-slave principle for controlling the sheet sequence. In one embodiment, the device controller of the monochromatic or highlight color printer unit is the master. 
     A controllable buffer storage is functionally allocated to the paper transport channel of the monochromatic or highlight color printer unit and/or to the color printer unit for the corresponding recording media. The buffer storage is arranged in the paper transport channel of the paper path coupling module. 
     The printer or copier device system above may include a synchronous control having the following features: 
     both printer units comprise a data controller, whereby the printer units are in communication with one another in the sense of a master-slave coupling; 
     a job separator is provided that, on the one hand, separates the incoming print data of an external data source into monochromatic and chromatic print job data, whereby, for sequence administration, each printed page comprises a specific address or feature and the respective print job data are then communicated to the corresponding printer units, and that, on the other hand, forms sequence data allocated to the sequence of the single sheets and communicates these to the printer unit having the master function, whereby the printer unit having the master function controls the other printer unit and/or the paper path coupling module for producing the sheet sequence. 
     Alternately, the printer or copier device system has a synchronous control means having the following features: 
     one of the two printer units comprises a data controller shared by both printer units; 
     the data controller has a job separator allocated to it that, on the one hand, separates the incoming print data of an external data source into monochromatic and chromatic print job data wherein, for sequence administration, each printed page comprises a specific address or feature, and that, on the other hand, forms sequence data allocated to the sequence of the single sheets, whereby the printer unit with the data controller controls the other printer unit and/or the paper path coupling module for producing the sheet sequence. 
     One of the two printer units may be fashioned as an insert means for acceptance and output of pre-printed single sheets. The paper path coupling module supplies the printed recording media to the paper transport channel of the respectively other printer unit such that it can be additionally printed by the accepting printer unit. The printer units are preferably fashioned as independently operable electrographic printer devices. 
     As a result of the provided coupling of a digital monochromatic printer working at high printing speed, for example a black-and-white printer or a maximum of a printer printing in two colors (highlight color printer), with a digital full-color printer, mixed printjobs wherein the sheet sequences contain individual color pages can be produced at high speed and especially economically. 
     A higher-ranking control unit designationally sends the pages to be printed to the respective printing unit and assures that the correct, alternate page sequence is produced in a common paper output stream. 
     It was inventively recognized that the electronic and mechanical coupling of the monochromatic or highlight color printing units on the one hand and of the full-color printing unit on the other hand makes it possible to produce mixed printing jobs that comprise monochrome or highlight color data on the one hand and, on the other hand, comprise full-color data, producing these print jobs with high performance and with a high degree of utilization of the two printing units. 
     The control unit controls the printer units in the production of the mixed printing job dependent on the incoming data stream such that both printing units—insofar as the sequence of the individual sheets in the print job allows it—work in parallel mode. The desired control and drive objective of the control is the parallel mode. 
     To this end, the monochrome (black-and-white) and the chromatic information from an original data stream are allocated to the respective printing unit and organized in terms of time. The shared paper path then conducts the printed single sheets—correctly sorted—into a shared deposit (for example, externally, in the output compartment of the fast monochromatic printer, in the output compartment of the color printer) or into a post-processing system in the form of a sheet/steam/or packet stream. One of the digital printer or digital copier machines having printing function can thereby also assume the collecting function on the basis of its internal paper path and/or can generate additional printed information on the delivered sheet (for example, color on the front side, black-and-white on the backside or some other arbitrary combination). The interfaces are fashioned such that the printers or copiers can be utilized according to the respective performance demands of the operator. In order to smooth different performance peaks (for example, a high sequence of monochromatic or chromatic pages), the shared paper path can contain a buffer function. The buffer function can be realized, for example, by a collecting compartment from which the printed sheets are in turn output as needed individually or in packet form. The paper path itself can be utilized as a buffer on the basis of its distance. Buffers in the form of paper loops are known for printers that process continuous form paper. The productivity of the system is enhanced by the buffer function. 
     Both single sheet printers (cut sheet printers) as well as printers that work with continuous form paper (fan-fold printer) can be utilized as printing units. The use of cutting devices is required given fan-fold printers. 
     The sheet stream produced by the color printer in a preferred exemplary embodiment is introduced into the output region of the monochromatic or highlight color printer via a suitable interface, for example via a paper path coupling module. Therein, the chromatically printed sheets are inserted in proper sequence into the sheet stream printed by the monochromatic or highlight color printer. The monochromatic or highlight color printer in this embodiment serves as a mixing means (or merging means). It is advantageous given this embodiment that the high-speed printing mode in the monochromatic or highlight color printing unit is not deteriorated by the delivery of the sheets printed in full color. 
     In another, advantageous exemplary embodiment, the sheets printed in full color are kept on hand in an intermediate storage. The intermediate storing makes it possible to print the full color pages in advance and to then designationally feed them into the sheet stream of the monochromatic or highlight color printing unit. Despite a slower printing speed of the full color printing unit compared to the monochromatic or highlight color printing unit, the printing speed of the overall system remains high given mixed printing jobs. The intermediate storage can ensue in the full-color printing unit or in the monochromatic or highlight color printing unit but preferably ensues in a paper path coupling module connected between the printer units. It can ensue via a stacked intermediate deposit of the sheets or via a corresponding buffer transport path that accepts a specific number of single sheets. 
     In another preferred exemplary embodiment, the sheet stream produced by the color printer is introduced into the input region of the monochromatic or highlight color printer via a suitable interface, for example, via a paper path coupling module having an intermediate storage. Within the monochromatic or highlight color printer, the sheets printed in full color are then optionally conducted past the transfer printing station and/or the fixing station, potentially a plurality of such stations, or are again printed therein monochromatically or in two colors at high speed. The sheets printed fullcolor are thereby inserted into the sheet stream printed by the monochromatic or highlight color printer. 
     The invention is especially advantageous in conjunction with a highlight color printer; applications, namely, having a high proportion of two-color prints are becoming more and more frequent in the field of electrographic high-performance printing. The page costs as well as the printing performance are then especially beneficial in an inventive printing system, namely high performance at low cost. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further embodiments of the invention are shown in the drawings and are described in greater detail below by way of example. 
     FIG. 1 is a schematic sectional view of an electrographic printer device system composed of a monochromatic single sheet high-performance printer and a single sheet color printer that are coupled to one another via a paper path coupling module, whereby the sheet collecting means is arranged integrated in the monochromatic single sheet high-performance printer; 
     FIG. 2 is a schematic sectional view of a printer device system corresponding to FIG. 1, whereby the paper path coupling module supplies the single sheet printed chromatically to the single sheet color printer such that it can be printed anew; 
     FIG. 3 is a schematic sectional view of a printer device system corresponding to FIG. 1 comprising a paper path coupling module containing a sheet buffer store and a paper shunt; 
     FIG. 4 is a schematic sectional view of a printer device system corresponding to FIG. 1, comprising a paper path coupling module containing a sheet buffer storage and a shared output path for the sheet sequence; 
     FIG. 5 is a schematic sectional view of a printer device system corresponding to FIG. 1, whereby the sheet collecting mean is arranged integrated in the chromatic single sheet high-performance printer; 
     FIG. 6 is a schematic sectional view of an electrographic printer device system composed of a monochromatic continuous form high-performance printer with appertaining cutting device and a single sheet color printer that are coupled to one another via a paper path coupling module, the latter comprising a shared output path to the sheet collecting means; 
     FIG. 7 is a schematic sectional view of a printer device system corresponding to FIG. 6, whereby the paper path coupling module comprises a sheet buffer store for the chromatic single sheets; 
     FIG. 8 is a schematic sectional view of an electrographic printer device system composed of a monochromatic continuous form high-performance printer and a continuous form color printer with appertaining cutting devices that are coupled to one another via a paper path coupling module that comprises a shared output path and a sheet buffer store for the chromatic single sheets; 
     FIG. 9 is a schematic sectional view of an embodiment of a printer device system corresponding to FIG. 8, whereby the paper path coupling module comprises a shared output path to a sheet collecting means; 
     FIG. 10 is a schematic block circuit diagram of a control for the electrographic printer device system composed of two printer devices respectively comprising a controller; 
     FIG. 11 is a schematic block circuit diagram of a controller for the electrographic printer device system composed of two printer devices having a shared data controller; 
     FIG. 12 is a schematic sectional view of an electrographic printer device system composed of a highlight single sheet high-performance printer and of a single sheet full-color printer whose paper transport paths are connected to one another at the output side of the highlight color printer system; 
     FIG. 13 is a schematic sectional view of an electrographic printer device system composed of a highlight color single sheet high-performance printer and of a single sheet full-color printer whose paper transport paths are connected to one another at the input side of the highlight color printer system; 
     FIG. 14 is an exemplary embodiment according to FIG. 13 that additionally contains a special transport path for recording media past two printing paths; and 
     FIG. 15 is an exemplary embodiment simplified compared to FIG. 14 wherein a monochromatic printer system having only one recording color is provided instead of the highlight color printer system. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Within the meaning of the present specification, the term “monochromatic printer unit” can usually be understood as a printer unit that can print only a single color. By comparison thereto, a printer unit that can print two colors is referred to as a highlight printer unit. Within the meaning of the invention, however, a monochromatic printer unit can often be provided in the following exemplary embodiments instead of a highlight printer unit and vice versa. What is understood, in contrast, by a color printer unit is a full-color printer unit with which all primary colors can be produced. Such color printer units can be constructed as YMCK printer units and, for example, can comprise an electrographic transfer printing station that prints yellow (Y), a magenta color (M), a cyan color (C) and black (K). Corresponding full-color ink printer units or, potentially, an offset printer device can also be provided for this purpose. 
     The printer or copier device systems shown in FIGS. 1 through 9 for performance-adapted production of a prescribed sheet sequence of monochromatic and/or chromatically printed single sheets fundamentally contain a digital, monochromatic printer unit  10  working at high printing speed of approximately 50, 100, 200, 400 pages per minute or more and a slow, digital color printer unit  11  having a standard printing speed of approximately 30, 50, or 100 pages per minute. Both printer units are fashioned as independent, individually drivable structural units, namely either as modules or as independent printers. They respective comprise a paper transport channel  12  or, respectively,  13  with paper transport elements, whereby the units such as exposure means, developer station, fixing station, etc., required for printing the recording media  14  or, respectively,  15  are arranged along these paper transport channels  12  or, respectively,  13 . The digitally operating electrographic printers  10  and  11  are constructed in a standard way. They can be fashioned as single sheet printers or as continuous form printers with appertaining cutter device or can be fashioned as digital copier devices having a print data input. A controllable paper path coupling module  16  is arranged between the printers  10  and  11 . It likewise contains one or more paper transport channels  17  with appertaining paper transport elements (rollers, etc.) that can be mechanically or, respectively, functionally coupled to the paper transport channels  12  and  13  of the printer units  10  and  11 . The paper path coupling module  16  can be fashioned as an independent structural unit in the form of a module or can be fashioned as a part integrated in one of the printer units  10  and  11 . Basically, the paper path coupling module  16  connects the paper transport channels  12  and  13  of the printer units  10  and  11 . Depending on the embodiment, it takes the printed single sheets from the paper channel of the one printer unit (for example, the color printer  11 ) and conducts them to the paper channel of the other printer unit (for example, the monochromatic printer  10 ), where they are deposited as a monochromatically and chromatically mixed job in a common sheet collecting means  18  (stacker) (FIGS. 1,  2 ,  3 ,  5 ) or, on the other hand, it takes the printed single sheets from both printer units  10 ,  11  (FIGS. 4,  6 - 9 ) and conducts them with the predetermined sheet sequence to a shared output path  19  (FIGS. 4,  6  through  9 ). A post-processing means, for example, a binder means or a sheet collecting means  18  in the form of a stacker, can be coupled to the output path  19 . 
     A higher-ranking control unit shown in FIGS. 10 and 11 and to be explained in greater detail later allocates the single sheet to be printed to the printer units  10 ,  11 , these then being collected as job in the shared sheet collecting means  18  or the post-processing means. In order to enable a speed-optimized production of the print job, the monochromatic and the chromatic information are separated from an original data stream of an external data source, are allocated to the respective printer unit and are organized in terms of time. In this way, a performance-adapted, time-saving and economical operation of the system can be achieved. What is thereby desired is a largely parallel operation of the printer units  10 ,  11 . 
     Regarding the embodiments of FIGS. 1 through 9 in detail: 
     Given the exemplary embodiment shown in FIG. 1, the electrographic printer device system is composed of the monochromatic single sheet high-performance printer  10  and the single sheet color printer  11 , these being coupled to one another via the paper path coupling module  16 . The paper path coupling module  16  takes the chromatically printed single sheets  15  from the color printer unit  11  and conducts them so that they are organized in time to the paper channel  12  of the monochromatic printer unit  10 . The sheet collecting means  18  is arranged integrated in the monochromatic single sheet high-performance printer and is composed of two deposit compartments present thereat that can be respectively individually used for constructing the mixed job. One deposit compartment can thereby be utilized as a temporary storage while the other is being filled. 
     In the exemplary embodiment of FIG. 2, the paper path coupling module  16  conducts the chromatically printing single sheet to the paper transport channel  12  of the monochromatic printer unit  10  preceding the actual electrophotographic unit, so that it can be additionally printed as needed. The sheet collecting means  18  is fashioned in conformity with FIG.  1 . In this exemplary embodiment, it is advantageous when the monochromatic printing unit  10  comprises a contact-free fixing process such as, for example, a photoflash fixing, irradiation fixing or a fixing with solvent (what is referred to as cold fixing) because the pre-printed colored side is then not injuriously influenced by the fixing process of the monochromatic printer unit. 
     In the printer device system according to FIG. 3, the paper path coupling module  16  contains a sheet buffer storage  20  and a switchable paper shunt  21  in the paper transport channel  17 . The sheet buffer storage  20  is constructed so as to be driven is and is composed of a controllable single sheet reservoir with appertaining transport elements for intermediate storage of the printed, chromatic single sheets. As a result of the buffer function, different performance peaks of the printer units  10  and  11  can be smoothed out. During the monochromatic printing of the single sheets in the fast, monochromatic printer unit  10 , the chromatic single sheets are already produced with the slow color printer unit  11  and are stored intermediately in the sheet buffer store  20  until they are delivered in proper sequence to the paper transport channel  12  of the monochromatic printer unit  10 . The buffer function, for example, can also be realized by a collecting compartment from which the printed sheets are in turn output as needed individually or in packet form. Depending on the switch position, the electromagnetically switchable paper shunt  21  enables the delivery of the chromatic single sheets via the paper transport channel  12  either directly to the sheet collecting means  18  or into a region preceding the electrographic printer unit  22  for renewed printing. 
     In the exemplary embodiment of the printer device system according to FIG. 4, the paper path coupling module  16  contains a sheet buffer storage  20  in a shared output path  19 . The chromatic and monochromatic single sheets are merged in the paper path coupling module  16  and are output in proper sequence via the output path  19 . A post-processing means, for example in the form of a binder means, can be coupled to the output path  19 . 
     The printer device system of FIG. 5 fundamentally corresponds to that of FIG.  1 . Differing therefrom, the sheet collecting means  18  is arranged integrated in the chromatic single sheet printer  11 . 
     As the monochromatic printer units  10 , the electrographic printer device systems of FIGS. 6 and 7 contain a monochromatic continuous form high-performance printer with an appertaining cutter means  23  for a sheet-by-sheet separation of the web-shaped recording medium  14   a . The paper path coupling modules  16  comprise a shared output path  19 . In FIG. 6, this is connected to an external sheet collecting means  29  in the form of a stacker. In the exemplary embodiment of FIG. 7, the paper path coupling module  16  additionally contains a sheet buffer store  20 . Otherwise, the function of the printer device systems corresponds to the exemplary embodiment of FIG.  4 . Sheets can be intermediately stored in the paper path coupling module  16 , these having been previously pre-printed at relatively slow speed by the color printer unit  11 . These sheets then can be supplied into the sheet stream of the monochromatic printer  10  with time and position precision. In the post-processing stacker  29 , the chromatic sheets and the monochromatically printed sheets are then deposited in the sequence order of the print job. 
     As shown in the exemplary embodiments of FIGS. 8 and 9, the monochromatic printer unit  10  and the chromatic printer unit  11  can be fashioned as continuous form printer units with appertaining cutter means  23 . In the example of FIG. 8, the paper path coupling module  16  contains a sheet buffer storage  20  for the color pages and a shared output path  19 ; in the example of FIG. 9, it is a shared output path  19  that is coupled to a sheet collecting means  29 . The functions correspond to those of FIGS. 6 and 7. Of course, a sheet collecting means  29  can be provided or a buffer storage  20  according to FIGS. 7 and 9 in one of the exemplary embodiments according to FIGS. 6 and 8 as well. 
     In order to be able to directly supply additional, pre-printed single sheets to the print job to be produced, it is also possible analogous to the exemplary embodiments of FIGS. 1 through 7, for example, to replace the color printer unit  11  by an insert means in which the masters are stacked and from which the masters are supplied to the shared sheet collecting means  18  in the described way via the paper path coupling module  16 . The insert means can also be provided as an auxiliary means in addition to the color printer unit  11  and can be in communication with the paper path coupling module  16  via a separate papertransport channel. Respective sheets of the differently printed type are then stored in the insert means, taken individually and inserted in exact position into the sheet stream of the connected printer. 
     It can be alternatively provided in the exemplary embodiments of FIGS. 6 and 11 to fashion the color printer  11  as a continuous form printer and to fashion the monochromatic printer  10  as a single sheet printer. 
     SYSTEM CONTROLLER 
     Synchronous controller devices as shown as block circuit diagrams in FIGS. 10 and 11 serve for the control of the printer system. 
     In the exemplary embodiment of FIG. 10, both the monochromatic printer unit  10  as well as the chromatic printer unit  11  has a separate data controller  24 / 1  and  24 / 2 . The control of the electrographic units  22 / 1  and  22 / 2  respectively ensues via a standard device controller  25 / 1  or, respectively,  25 / 2 . The fundamental structure of data controller and device controller is known, for example, from European Patent Document EP-B1-0239845 (86P1149). Since both printer units  10  and  11  respectively comprise a data controller respectively, or comprise a device controller, they can also be operated as separate devices independently of one another. 
     In the system, the two printer units  10  and  11  are coupled to one another according to the master-slave principle via a communication module  26  on an apparatus control level. The faster, monochromatic printer unit  10  with its data controller  24 / 1  thereby preferably assumes the master function. This principle has likewise been described in general in European Patent Document EP-B1-0239845. 
     A print server  27  that comprises an integrated job separator  28  is functionally connected to the two data controllers  24 / 1  and  24 / 2  and to the communication module  26  via data lines (data buses). The print server  27  in turn communicates with an external data source, for example a PC, a data network or a host. The paper path coupling module  16  is likewise coupled to the printer units  10  and  11  via control lines. 
     The function of the synchronous control means is thereby as follows: the print data coming from the external source are separated into monochromatic and chromatic print job data in the job separator  28  of the print server  27  and are thereby assigned a specific address or a characterizing feature for sequence administration of each printed page. These data are then transmitted to the data controllers  24 / 1  and  24 / 2  of the respective printer units  10 , 11 . At the same time, the master printer unit, the monochromatic printer unit  10  in this case, is informed of the sequence of the printed pages as sequence data from the print server  27 . The master printer  10  then controls the color printer  11  with the paper path coupling module  16  such via the communication module  26  that this delivers the printed color pages to the monochromatic printed pages at the proper point in time via the paper path coupling module  16 , namely in the way set forth in conjunction with FIGS. 1 through 9. It can thereby be necessary that the color pages are intermediately stored in the paper path coupling module  16  in the sheet buffer store  20  or in the paper transport channel. This correct point in time is calculated—taking the different printing speeds of the printer units  10  and  11  and the sheet sequence of the job to be produced into consideration, with a corresponding, microprocessor-controlled computer means that can be a component part of the device controller  25  or of the data controller  24 / 1  or of the job separator  28  as well. The synchronous controller thereby aims at a parallel operation of the printer units. When, for example, the job initially contains ten monochromatic pages and then one colored page, the printer units  10  and  11  are operated in parallel, and the colored page is intermediately stored until the tenth monochromatic page has been produced. The color page is then supplied to the sheet collecting means via the corresponding paper transport channel and the common job is thus formed. 
     In the exemplary embodiment of the synchronous control means according to FIG. 11, the monochromatic printer unit  10  comprises a shared data controller  24 / 3  for both printer units  10  and  11 . The job separator can also be integrated in it. In this case, the print server  27  sends all print data to this data controller  24 / 3 , which separates the job and in turn drives the color printer unit  11 , analogous to the exemplary embodiment of FIG. 10. A communication module  26  is also required given this constellation in order to assure the chronologically correct merging of the printed pages in the correct sequence. A shared data controller  2413  for both printer units  10  and  11  can be advantageous due to the lower controller outlay when very little chromatic printing is carried out compared to the monochromatic printing. However, it can also be integrated in the chromatic printer unit  12  instead of in the monochromatic printer unit  11 . 
     FIG. 12 shows a printer system that corresponds to the exemplary embodiment of FIG. 1 in terms of fundamental structure. The color printer unit  11  is thereby connected to the output region of the printer unit  10  via the paper path coupling module  16 . It can be a single sheet color printer unit or a continuous form color printer unit with a following cutter means. The printer unit  10  is essentially composed of an input station  30 , of a printing station  38  and of an output station  49 . Two transfer printing stations D 1  and D 2  that respectively print monochromatically are located in the printer station  38 . A majority of the print data supplied to it can be printed in a first color, for example black, and selected data can be printed with a second color, for example, with this highlight printer station in order to emphasize these regions on the printed matter that is produced. Such a printer station, on the one hand, is not capable of producing full-color printing but, on the other hand, can achieve an essentially equally high page performance as a corresponding monochromatic printer unit. In order to drive a highlight color printer station in an inventive printer system, the print server or, respectively, the job separator is also in the position to recognize highlight color printed data from the original print data stream of the network or host computer and supply to the highlight color printer unit  10 . The controller  25 / 1  of the highlight color printer unit  10  then conducts the respectively appertaining data to the two transfer printing stations D 1  and D 2 , for example data of the color black to the first transfer printing station D 1  and data of the color red to the second transfer printing station D 2 . 
     The printer unit  10  shown in FIG. 12 corresponds to the known printer of the assignee having two printer units that is disclosed in Published PCT Application WO 98-18052 A1. The content of this WO publication is thus incorporated into the present specification by reference. 
     The printer station  38  of the printer unit  10  is kept variable insofar as the two transfer printing stations D 1  and D 2  are respectively interchangeable. Without further ado, thus, the printer station  38  can be re-equipped from a highlight color printer station to a monochromatic printer station that prints only in a single color overall, in that, for example, both the transfer printing station D 1  as well as the transfer printing station D 2  print in the same color, for example, black. As a result of this refitting possibility, a multitude of possible print applications derive, so that a very flexible printer system arises overall. A multitude of operating modes can be implemented with the printer station  38 . 
     The first transfer printing path  35 , a connecting channel  37  and a delivery channel  39  form a first ring R 1  that is allocated to the first transfer printing station D 1 . Correspondingly, a second transfer printing path  41 , the discharge channel  40  and the connecting channel  37  form a second ring R 2  that is allocated to the second transfer printing station D 2 . The two rings R 1  and R 2  thus comprise a shared path section, the connecting channel  37 , and form a structure in the shape of an  8 . 
     A plurality of supply compartments  36  for stacks of single sheets are arranged in a known way in the input station  30 . They are respectively emptied via a shared output path  33 , and the sheets are handed over from this output path to the input path  31  of the printer station  38 . The input station can thereby be fashioned as a module that can be mechanically coupled to the printer station  38 . Sheets can also be supplied from the outside via an input channel  32 . This delivery can enable either a delivery of additional input stations or, as already shown in FIG. 2, a delivery from the sheet buffer store  16  or, respectively, directly from the color printer unit  11 . 
     In a first operating mode, sheets are printed on one side, i.e. in simplex operating mode, in that recording medium sheets are supplied from an input path  31  of the printer via a shunt W 1  to the transfer printing path  35  of the first transfer printing station D 1  for printing. Subsequently, the sheets are fixed in a fixing station F 1  and are supplied via shunt W 2  to a discharge channel  40 , from the latter to the shunt W 4  via the discharge channel  40  and then into the output channel  43 . The printed sheets are then supplied directly to the deposit compartments  18  via the shunt  44  or are previously turned over at the turnover station  45 . Optionally, the printed sheets can be supplied via an output shunt  46  to an output channel  48  through which the printed sheets are supplied to further devices for post-processing, for example to a binder means  51  or to an external stacker. 
     Given this simplex operating mode with only one transfer printing station, the second transfer printing station D 2  is not in operation. This operating mode can be particularly utilized when a malfunction is present at the transfer printing station D 2  or when minor surface interventions are to be carried out. In exactly the same way, a second simplex operating mode can be implemented wherein the first transfer printing station D 1  is out of operation and sheets are supplied from the working path  31  of the printer via shunt W 1 , a delivery channel  39 , a shunt W 3  to the transfer printing path  41  of the second transfer printing station D 2  for printing. The printed pages are subsequently fixed in the second fixing station F 2  and are in turn supplied via the shunt W 4  to the output channel  43 . 
     In a third simplex operating mode with enhanced printing speed, nearly twice as many sheets can be printed as in the two first simplex operating modes. In this third simplex operating mode, sheets are shot from the input station  30  into the input path  31  at approximately twice the speed and are supplied from the shunt W 1  directly to the first transfer printing path or the delivery channel  39  in alternation. Subsequently, the sheets following one another in the input path  31  are nearly simultaneously printed in the two transfer printing stations D 1  or, respectively, D 2  and are supplied to the output channel  43  in alternation at the shunt W 4  in the original sequence. 
     In a simplex highlight color operating mode, sheets are supplied for the input path  31  via the first transfer printing path  35 , the first transfer printing station D 1  for printing in a first color, for example black. From here, the sheets are supplied via shunt W 2  to a connecting channel  37  and are forwarded via shunt W 3  to the second transfer printing path  41 . Here, a sheet is respectively printed by the transfer printing station D 2  in a second color, for example red, on the same side as in the transfer printing station D 1  and is subsequently output. 
     In a first duplex operating mode, sheets are supplied from the input path  31  to the transfer printing station D 1  for printing the front side, are then supplied via the shunt W 2  to a connecting channel  37  and are supplied via shunt W 3  to the second transfer printing path  41 . The sheet can thereby be turned over at the shunt W 2  or shunt W 3 , so that it is printed on the backside in the transfer printing path  41  of the second transfer printing station D 2 . This duplex operating mode is particularly suited for monochromatic, i.e. same-colored printing of a sheet on the front and back side. 
     In a highlight color duplex operating mode, sheets are supplied from the input path  31  via the first transfer printing path  35  to the first transfer printing station D 1  for printing the front side with the color black. From here, the sheets are supplied via the shunt W 2 , the connecting channel  37  and the shunt W 3  to the second transfer printing path  41 . Here, the sheets are printed with the second transfer printing station D 2 , likewise on the front side but with the second color, red. The sheets are then supplied via the shunt W 4  to the output channel  43 , are turned over at the shunt  4  and are transported into the discharge channel  40  via the shunt W 4 . From here, the sheet is resupplied via the shunt W 2  to the connecting channel  37  and to the delivery channel  39  via the shunt W 3 . From here, the sheet is resupplied via the shunt W 1  to the first transfer printing path  35  and is printed on the back side with the first transfer printing station D 1 . Subsequently, the sheet, in the same way as set forth above, can be supplied to the second transfer printing station D 2  for printing the back side with the second color and can then be output via the output channel  43 . 
     In the operating mode that has just been described, the sheet is turned over in the region of the shunt W 4 . Alternatively thereto, the sheet, of course, can also be turned over in the shunt W 2  or the shunt W 3 . 
     In an alternative highlight color duplex printer operating mode, the sheet printed in duplex by the transfer printing station D 1  could be supplied via the connecting channel  37  to the second transfer printing station D 1  for duplex printing in the second color. To this end, the sheet, following the initial printing with the second color, would have to be supplied via the shunt W 4  to the discharge channel  40  and would have to be resupplied to the first transfer printing path  41  while being turned over. 
     In order to be able to implement all of the operating modes of the highlight printing station  38  set forth up to now, the sheet transports (for example stepping motors) in the delivery channel  39  and in the discharge channel  40  are drivable in two opposite directions. A reversible drive can also be provided in the connecting channel  37  for an operating mode—to be described later with reference to FIGS.  13  and  14 —wherein sheets are conducted through the printing station  38  without traversing the two transfer printing transport paths  35  and  41 . 
     In a monochrome duplex operating mode wherein printing is only carried out with the printing station D 1 , sheets are again supplied from the input path  31  to the printing station D 1  via the first transfer printing path  35 . The sheets are subsequently supplied via the shunt W 2  to the connecting channel  37  and via the shunt W 3  to the delivery channel  39 . The sheet is thereby turned over at the shunt W 2  or the shunt W 3 , so that it is printed on the back side when it passes through the first transfer printing path  35  again. The delivery channel  31  thus acts not only as a delivery channel in the above-described, fast simplex mode but also acts as a duplex return channel, whereby the sheets are transported back from the end of the first transfer printing path  35 , i.e. from the shunt W 2 , to the start of the transfer printing path  35 , i.e. to the shunt W 1 . The reversible drives in the delivery channel  39  are also needed for this functionality. After the double-sided printing of a sheet in the transfer printing station D 1 , the sheet is output to the output channel  43  via the discharge channel  40 . 
     The second transfer printing station D 2  is also in the position to implement a duplex operating mode by itself without a sheet being printed by the transfer printing station D 1 . To this end, the sheet is directly supplied to the second transfer printing station D 2  via the delivery channel  39 . The discharge channel  40  acts—in a way analogous to the delivery channel  39 —not only as a discharge channel for the transfer printing station D 1  but also as a duplex return channel for the transfer printing station D 2 , whereby the sheet is conducted from the end of the second transfer printing path  41 , i.e. from the shunt W 4 , back to the input thereof, i.e. to the shunt W 3 . Delivery channel  39  and discharge channel  40  thereby also have a function of bypassing the transfer printing station D 1  or, respectively, D 2  (what is referred to as a bypass function). 
     In the exemplary embodiment of FIG. 12, the sheet stream output by the color printer unit  11  is introduced via the buffer store  16  into an introduction channel  47  provided in the output station  49  of the monochromatic or, respectively, highlight color printer unit  10 . Although the buffer store is referred to here as a separate device, it can also be integrated within the output station  49  of the printer unit  10  or can be integrated at the output side in the color printer unit  11 . 
     The device controller of the printer  10  controls the removal of the individual color sheets in the correct sequence, dependent on the sheet sequence that is output from the monochromatic or, respectively, highlight color printer station  38  into the output station  43  of the printer unit  10 . The monochromatic printer  10  thereby serves as a mixing means (or merger apparatus). The time-exact merging of the sheet sequences from the color printer  11  and from the printing station  38  of the monochromatic printer thereby ensues in the region of the turnover station  45  of the printer  10 . The mixed job that is compiled in this way is then optionally supplied via the output shunt  46  to the output channel  48  to a post-processing device, for example a binder means, or is deposited in one of the deposit compartments  18  of the monochromatic printer  10 . 
     Inputs at the operator side about the desired operating mode (monochromatic, highlight color, simplex, duplex, etc.) of the monochromatic printer unit  10  are possible via the control panel  34 . Whether the jobs are collected in the monochromatic printer  10  or are to be supplied via the output interface  48  to further post-processing devices can also be input via this control panel  34 . 
     FIG. 13 shows the coupling of the color printer  11  to the input station  30  of the monochromatic highlight color printer unit  10  via the coupling module  16 . Sheets that have been printed by the color printer unit  11  are thereby transferred into the printer  10  via the input channel  32  and are then 
     a) supplied via the delivery channel  39 , the connecting channel  37  and the discharge channel  40  directly to the output station  49  without being printed in the printing unit  10  or 
     b) supplied to one of the two transfer printing paths  35  and  41  for printing with the transfer printing stations D 1  or, respectively, D 2  at the shunt W 1 , in selective fashion. All operating modes described with reference to FIG. 12 can thereby also be implemented with the sheets transferred in from the color printer unit  11 . 
     Given the exemplary embodiment shown in FIG. 14, a special path  42  into which sheets can be transferred via an input shunt  50  is provided in addition to the exemplary embodiment shown in FIG.  13 . Sheets that have been printed by the color printer unit  11  can be optionally moved past the two transfer printing stations D 1  and D 2  directly to the output station  49  or—via the shunt W 1 —to the transfer printing station  38  for printing one color (monochromatic) or in two colors as a highlight color print. The transport channels  35 ,  39  and  41  allocated to the two rings R 1  and R 2  thereby need not be traversed, these paths being thus available uninterrupted for the printing procedures in the printing station  10 . Sheets from the supply compartments  36  can also be transported in the special path  42  via the three-way shunt  50  directly to the output station  49  without using the transport channels of the rings R 1  and R 2 . 
     In an exemplary embodiment, which is somewhat simplified compared to FIG. 14, the transfer printing station D 2  as well as the transfer printing transport path  41  thereof are omitted. The printing system  10  is then only capable of printing monochromatically in exactly one color with the transfer printing station D 1 , but has the duplex functionality wherein sheets at the output side are resupplied to the transfer printing station D 1 . In this exemplary embodiment, too, the special path  42  can be advantageously utilized because sheets that come from the color printing unit  11  need not be transferred into the ring system R 1  of the transfer printing station D 1 . The other elements of the exemplary embodiments of FIGS. 12 through 14 can thereby be incorporated. 
     Many exemplary embodiments have been described. It is thereby clear that individual elements of the corresponding parts of the description and/or Figures can be transferred without further ado to other parts of the description and/or Figures and/or can be combined with one another. 
     Although other modifications and changes may be suggested by those skilled in the art, it is the intention of the inventors to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of their contribution to the art.