Electrophotography – Document handling
Reexamination Certificate
2001-06-08
2003-11-11
Hirshfeld, Andrew H. (Department: 2854)
Electrophotography
Document handling
C399S016000, C399S364000, C399S381000, C101S211000
Reexamination Certificate
active
06647239
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a method for printing individual sheets in a printer or a copier, in which two-sided printing on individual sheets can be performed.
2. Description of the Related Art
High-performance printers can be operated in what is referred to as a duplex mode, which is also called duplex color spot mode. In this operating mode, individual sheets are printed on both sides. When only one print operation ensues on one side and two print operations with different colors ensue on the other side, then this is called the duplex printing mode with three-fold printing. When two print operations ensue on both sides of the individual sheet, then this is called duplex printing mode with four-fold printing.
Various duplex printing systems with at least two printing units are disclosed by U.S. Pat. No. 4,591,884. Another high-performance printer device with two printing units is disclosed by Published PCT Application WO 91/13386 A1. It comprises two printing units and turnover channels for turning the individual sheets over. A transfer printing transport path is allocated to each printing unit.
When individual sheets are supplied such in such a high-performance printer device with two printing units such that the spacing between two individual sheets is greater than the length of an individual sheet viewed in transport direction, then a safety margin is created between two individual sheets that allows a further individual sheet to be transferred in upon transport of the individual sheets in gaps between two successive individual sheets at intersections of the sheet transport paths. Given this procedure, however, the sheet throughput is relatively low due to the relatively large sheet spacings.
U.S. Pat. No. 5,159,395 discloses a printer device having only a single printing unit wherein spaces are likewise created between two successive sheets of a sheet stream in order to subsequently transfer further individual sheets into the sheet stream.
U.S. Pat. No. 5,337,135 discloses a further printer device with only a single printing unit wherein a first printing operating condition with a first, relatively close printing spacing is provided and a second operating condition with a second, larger sheet spacing [is provided], whereby following sheets are again transferred into an existing sheet stream in the second operating condition.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method for printing individual sheets in a printer or in a copier in the duplex printing operating mode, whereby a high throughput of individual sheets given low wear and reduced risk of jams are achieved
This and other objects and advantages are achieved by a method for printing individual sheets in a printer or in a copier, whereby a predetermined number of individual sheets is combined into a group, whereby the individual sheets have a predetermined spacing from one another at a transfer printing speed that is less than the length of an individual sheet as viewed in the transport direction, the individual sheets of this group are successively supplied to a first printing unit for printing with a first color on the first side, the individual sheets of the group are subsequently successively supplied to a second printing unit for printing with a second color on the first side, and whereby the individual sheets of the group, given turnover of the individual sheets, are successively re-supplied to the first printing unit for printing with the first color on the second side.
Advantageous developments are provided by a method as set forth above, characterized in that the individual sheets of the group are supplied to the second printing unit for printing with the second color on the second side and are then output. In the method, the distance between the individual sheets at the printing units may be essentially retained during the transport of the group of individual sheets. In one embodiment, the group of individual sheets are supplied to the first printing unit from an input section via a first transfer printing transport path to which a connecting channel connects and via which the individual sheets are supplied to a second transfer printing transport path for the second printing unit; the second transfer printing transport path discharges into an output section; a discharge channel for the transport of the single sheets is provided between output section and the one end of the connecting channel; and a delivery channel is arranged between the input section and the other end of the connecting channel. The method further provides that the group of individual sheets first traverse the first transfer printing transport path, then the connecting channel, the second transfer printing transport path, the discharge channel, again traverse the connecting channel, the delivery channel, the first transfer printing transport path, the connecting channel and the second transfer printing transport path and are then output at the output section.
According to another embodiment, the method for printing individual sheets in a printer or in a copier provides that a predetermined number of individual sheets is combined into a group, whereby the individual sheets have a predetermined spacing from one another at the transfer printing speed that is less than the length of an individual sheet as viewed in transport direction, the individual sheets of this group are successively supplied to a first printing unit for printing with a first color on the first side, the individual sheets of the group, given turnover of the individual sheets, are successively re-supplied to the first printing unit for printing with the first color on the second side, and whereby the individual sheets of the group are subsequently supplied to the second printing unit for printing with the second color on the second side and are then output. Further, the group of individual sheets are supplied to the first printing unit from an input section via a first transfer printing transport path to which a connecting channel connects and via which the individual sheets are supplied to a second transfer printing transport path for the second printing unit; the second transfer printing transport path discharges into an output section; a discharge channel for the transport of the single sheets is provided between output section and the one end of the connecting channel; and a delivery channel is arranged between the input section and the other end of the connecting channel. In addition, the group of individual sheets first traverse the first transfer printing transport path, then the connecting channel, the delivery channel, traverse the first transfer printing transport path again, the connecting channel and then the second transfer printing transport path and are then output at the output section.
As an improvement, the method may provide that the input section contains a first shunt that supplies the individual sheets either from the input section or from the delivery channel to the first transfer printing transport path. In a preferred embodiment, a second or, respectively, third shunt is arranged at the junction between the first transfer printing transport path and connecting channel as well as at the junction of the second transfer printing transport path and connecting channel. A fourth shunt may be arranged between the second transfer printing transport path and discharge channel. An embodiment is characterized in that the second, the third and/or the fourth shunt carries out a turnover function wherein the individual sheet is turned over. In particular, for turning the individual sheet over, this is first transported past the respective shunt on a first transport path in a first transport direction into a turnover section; subsequently, the transport direction is reversed; and the shunt conveys the individual sheet to a second transport path in the other transport direction.
An embodiment provides that, after the group of individual sheets has been su
Culler Jill E.
Hirshfeld Andrew H.
Oce Printing Systems GmbH
Schiff & Hardin & Waite
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