Electrophotography – Image formation
Reexamination Certificate
2001-04-16
2002-12-31
Lee, Susan S. Y. (Department: 2852)
Electrophotography
Image formation
C358S001150, C399S009000
Reexamination Certificate
active
06501929
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a printing system, whereby a recording medium is printed first by a first printer and then by a second printer, and is also directed to a method for printing with such a printing system.
2. Description of the Related Art
In printing systems of this type, the recording medium is printed by a first printer and is then supplied to a second printer that is of the essentially same type as the first printer. The recording medium can thereby be present in the form of individual sheets or as a web-shaped recording medium. As needed, it can be composed of paper, plastic film material or of other materials as well. Dependent on the embodiment of the printer devices, fanfold material, roll material with margin perforation or roll material without margin perforation can be printed.
European Patent Document EP 154 695 B1 discloses a tandem printing system. For the drive of such a printing system, European Patent Document EP 0 239 845 B1 provides that the main control devices of the two printers be connected, on the one hand, via a host computer on a data control level and, on the other hand, via a second connection on a device control level.
Margin-perforated, web-shaped paper is often employed as a recording medium in electrographic high-performance printers having printer performances of more than 40 pages per minute. This paper has lateral holes at its longitudinal edge sides for the margin transport and for monitoring the position of the paper. It is thereby transported with caterpullars that engage into the lateral transport holes of the paper. The margin perforation is used for the drive control, particularly when processing pre-printed paper. Given such applications, the information applied in the electrographic printer should be fitted into the pre-print as exactly as possible. For such positionally exact printing, the position of the paper in transport direction must exactly adjusted to or, respectively, synchronized with the drive thereof or, respectively, the movement of the photoconductor drum employed for the recording.
Pre-printed paper is also present in the second printer of a tandem printing system when the paper is printed by the first printer and subsequently supplied to the second printer. This, for example, can be the case when the first printer prints in a first color and the second printer prints on the same page in a second color.
German Patent Document DE-A-195 00 169 A discloses a method for the control of the printing process in a tandem printing system, whereby continuous stock for the double-sided printing is first supplied to the first printer and printed thereat on one side, and, finally, the paper web is supplied to the second printer for printing the back side. Even-numbered pages are thereby printed by the first printer and odd-numbered pages by the second printer.
U.S. Pat. No. 5,526,107 discloses a color printer device wherein the various color separations are printed in different printer units that follow one another in the paper transport path. The printing events of the respectively following printer units are thereby controlled with marks in order to achieve an exactly registered printing.
U.S. Pat. No. 5,208,640 discloses a system wherein print data for a plurality of laser printers are synchronized. Print data are deposited in a FIFO memory and in turn fetched therefrom. However, no teaching can be found in this document that one of the printers provides the other with control data.
SUMMARY OF THE INVENTION
In a tandem printing system, an object of the invention is to assure the correct allocation of the printed pages printed on the recording medium by the two printers with optimally high dependability.
This object is achieved by the method for printing in a printing system, whereby a recording medium is printed first by a first printer and then by a second printer, including: a synchronization procedure is implemented at the beginning of the printing event, whereby both printers are matched to one another upon employment of a synchronization mark applied on the recording medium; the print data are supplied page-by-page from a print data source to the first and to the second printer; information about the page numbers are communicated to the printers together with the respective print data; the first printer deposits at least an information about the page number of a page printed by it into a buffer memory during the course of its printing event; and a checking step is carried out page-by-page to see whether the information communicated to the second printer from the print data source and the information stored in the buffer memory conform to a rule predetermined dependent on the printing mode; and whereby, given a positive check result, the second printer implements the printing event and, given a negative check result, an error is reported.
The object of the invention is also met by a printing system, whereby a recording medium is printed first by a first printer and then by a second printer, including: a synchronization procedure is implemented at the beginning of the printing event, whereby both printers are matched to one another upon employment of a synchronization mark applied on the recording medium; print data are supplied page-by-page from a print data source to the first and to the second printer; information about the page numbers are communicated to the printers together with the respective print data; whereby the first printer deposits at least an information about the page number of a page printed by it into a buffer memory during the course of its printing event; and a comparison unit is provided that checks page-by-page to see whether the information communicated to the second printer from the print data source and the information stored in the buffer memory conform to a rule predetermined dependent on the printing mode; and whereby given a positive check result, the second printer implements the printing event and, given a negative check result, an error is reported. Advantageous embodiments of the invention are further provided by the method wherein the step of checking of the two information ensues at a point in time that is defined such by the feed of the recording medium that the print data are reproduced page-exactly on the recording medium. In a preferred embodiment, the method provides for utilizing a FIFO memory as a buffer memory. The length of the FIFO memory corresponds to the number of pages of the recording medium present between the printers, and the readout of the FIFO memory is controlled by the feed of the recording medium carrier. The check is implemented in the second printer. As a further aspect, the page information together with a communication protocol is communicated from the device controller of the first printer to the device controller of the second printer. In the method, a synchronization mark is generated on the recording medium by the first printer for the positionally exact registration of the print image, the synchronization mark being read by a sensor arrangement in the second printer, whereby the sensor signal is employed for the positionally exact printing in the second printer. The synchronization mark is, for example, printed onto the recording medium as an optical mark.
In the preferred printing system, the recording medium is web-shaped. The buffer memory may be a FIFO memory. The comparison unit may be connected at least to a drive control of the second printer so that the point in time of the check for the two page information can be controlled dependent on the feed of the recording medium. The synchronization mark is generated on the recording medium by the first printer for the positionally exact registration of the print image, and a sensor arrangement that reads the synchronization mark is provided in the second printer, and the sensor signal thereby generated is supplied to the device controller of the second printer for the control of the printing event in the second printer. Preferably, exact
Bäumler Ulrich
Böck Heinz
Gibisch Herbert
Hausmann Bernd
Hofmann Holger
Lee Susan S. Y.
Oce Printing Systems GmbH
Schiff & Hardin & Waite
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