Electrophotography – Document handling – Copy
Reexamination Certificate
2001-01-25
2001-11-13
Braun, Fred L. (Department: 2852)
Electrophotography
Document handling
Copy
Reexamination Certificate
active
06317581
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device or, respectively, a system, in particular a printer or copier, with two electrographic printing units of substantially the same type, wherein each of the printing units prints an image pattern on a sheet-type material. The device includes having an input section via which the sheet-type material can be supplied individually in successive fashion and an output section via which the printed sheet-type material is ejected individually in successive fashion.
2. Description of the Prior Art
Electrophotographic printers of this type are known, for example, from DE 34 16 252 A1, EP 0 104 022 A2, DE-PS 1,280,605, DE 34 07 847 A1 or WO 91/13386. With printers of this type, high printing performance can be achieved, even in duplex operation, as long as both printing units are working as they should. However, the devices specified in the cited publications have the disadvantage that, in the case of failure of one of the printing units, a drastic reduction in the performance of the duplex operation results. This is because a sheet that is to be printed on both sides in duplex operation must then be accelerated repeatedly in the opposite direction in order to enable it to be printed on both sides by the one remaining printing unit.
From U.S. Pat. No. 5,150,167, a printing unit is known that contains two printing units. One of the printing units has a priority status. As such, sheets that have been printed in the lower-order printing unit additionally can be printed in the priority printing unit. However, if the priority printing unit fails, double printing and, in particular, duplex printing is not possible.
From U.S. Pat. No. 5,208,640 A, a further print apparatus is known that contains several printing units. The printing units are connected with one another via a ring system wherein a common turning apparatus with a shunt for all printing units is used. If the turning apparatus fails, e.g. due to a switching error in the shunt, duplex operation is no longer possible.
An object of the present invention, is to therefore, provide a device, in particular a printer or a copier, that has a high print performance or, respectively, copier performance, in particular in duplex operation.
SUMMARY OF THE INVENTION
This object is solved for the device, or system, named above in that a first printing unit and a substantially identical second printing unit are provided in the device, to which sheet-type material can be supplied via the common input section. The sheet-type material printed by the second printing unit is ejected via a common output section. The two transfer printing transport paths of the two printing units are respectively connected via connecting paths to form two ring systems. A shunt is respectively provided at each of the two rings by means of which the sheet-type material can be turned independent of the respective other shunt in the allocated ring.
In the device of the present invention, two printing units of substantially similar construction are used. The components for these printing units, e.g. the electronic control unit, the developer units, the toner supply and carry-off means, etc., can be retained almost unchanged. Each printing unit, therfore, has in itself a very high operational reliability. Both printing units use a common input section via which the sheet-type material is supplied. Likewise, both printing units use in common an output section for carrying away the printed sheet-type material. The new device is thereby constructed very compactly and can be manufactured at a low expense. The print performance is increased significantly due to the two printing units. Also by means of the inventive ring system, a sheet-type material printed by one of the two printing units can again be supplied to the same printing unit in the same direction as in the first print process.
According to an embodiment of the present invention, a first transfer printing transport path is provided for the first printing unit and a separate second transfer printing transport path is provided for the second printing unit. The transfer printing for both printing units takes place with the same speed. Since each printing unit has a separate transfer printing transport path, sheet-type material can be printed with one printing unit even upon failure of the other.
In addition, it is particularly advantageous if the two rings are connected via two three-way shunts. A multiplicity of transport paths arises by this arrangement.
An embodiment of the present invention provides that the input section contains a shunt that supplies sheet-type material either to the first transfer transport path or to the second transfer printing transport path. In this embodiment, the simplex printing operating mode is performed with one color; i.e., supplied sheet-type material (e.g., individual sheets of paper) are printed on one side by the first printing unit or by the second printing unit. In a further development, the shunt supplies sheet-type material alternately to the first transfer printing transport path and to the second transfer printing transport path. Since each printing unit prints the sheet-type material with the same transfer printing speed, and two printing units are arranged in parallel, the print performance in the device is doubled. Accordingly, individual sheets can be supplied and carried away with twice the print speed.
Another embodiment provides that the first transfer printing transport path and the second transfer printing transport path are connected by a connecting channel through which sheet-type material can be conveyed in one or in both transport directions. By means of these measures, printed material can be supplied from the first printing unit to the second printing unit, and from the second printing unit to the first printing unit, in order to be printed. The connecting channel also creates a feedback that connects the two printing units with one another, thus enabling many print processes.
Another embodiment provides that the sheet-type material is turned during its transport from the first transfer printing transport path to the second transfer printing transport path.
In this way, each printing unit can print both the front side and the back side of an individual sheet. If developer stations with different colors are used for the two printing units, then two image patterns with two different colors can be printed on each side of the individual sheet; i.e., what is known as two-color duplex operation, or duplex color spot operation, can be performed.
According to another embodiment of the present invention, a printer system is specify in which two devices of the same type are connected by an interchange apparatus that supplies the sheet-type material printed by the first device to the second device of the same type. If each of these two devices contains differently colored printing, units, then individual sheets can be printed on both sides with four colors. Of course, other variants are conceivable as well; e.g., one device prints two colors on one side and the other device prints two colors on the other side.
Additional features and advantages of the present invention are described in, and will be apparent from, the Detailed Description of the Preferred Embodiments and the Drawing.
REFERENCES:
patent: 4591884 (1986-05-01), Miyamoto et al.
patent: 4783681 (1988-11-01), Tanaka et al.
patent: 4972236 (1990-11-01), Hasegawa
patent: 5150167 (1992-09-01), Gonda et al.
patent: 5208640 (1993-05-01), Horie et al.
patent: 5598257 (1997-01-01), Keller et al.
patent: 6101364 (2000-08-01), Boehmer et al.
Boehmer Georg
Dietl Joseph
Hahn Hans
Heller Bernward
Mugrauer Hubert
Braun Fred L.
Oce Printing Systems GmbH
Schiff & Hardin & Waite
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