Photocopying – Projection printing and copying cameras – Identifying – composing – or selecting
Reexamination Certificate
1999-04-19
2001-03-13
Adams, Russell (Department: 2851)
Photocopying
Projection printing and copying cameras
Identifying, composing, or selecting
C355S026000, C399S232000, C399S298000
Reexamination Certificate
active
06201595
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to an electrophotographic printer for printing a final image carrier, having a transport for transporting the final image carrier, a first printer unit for generating a first toner image on the basis of a first arrangement of color particles on a first photoconductor, at least one further printer unit for generating a further toner image on the basis of a further arrangement of color particles on a further printer, and a transfer apparatus for direct or indirect transfer of the first toner image from the first photoconductor and of the further toner image from the further photoconductor onto a surface section of the front side of the final image carrier.
2. Description of the Related Art
The term a color separation generally refers to a toner image that was applied by a single developer station. A multi-colored print image consequently arises by superimposition of a plurality of color separations.
A printer which uses color separation is disclosed, for example by European published application EP 0 659 569 A1. Given the printer described therein, the first single-color toner image (or color separation) is fixed by the first printer unit before the second toner image, which is likewise of a single-color, is applied onto the already fixed, first toner image. An exactly registered multi-color printing is not possible with the known printer since it cannot be assured that the two toner images are printed exactly on the same surface section of the carrier material. As a result thereof, the picture elements of the first toner image and of the second toner image may also not be aligned exactly relative to one another. The result is that undesired superimpositions or empty spaces between picture elements of different toner images arise (this also being known as registration error). High quality color printing is ultimately not possible. Given graduated, planar color printing, color errors and color seams arise. Further, unsharp and/or color-falsified image details arise in the region of the lines and written characters when printing lines and written characters.
The printer according to the above-cited published application is also inflexible with respect to an being adopted to different printing jobs. When, for example, printing is to be carried out with only one color, then the second printer according to said published application is superfluous. Moreover, a color pallet of four predetermined colors can only be selected when printing with the printer according to the European patent document EP 0 658 569 A1.
Published German application DE 44 34 081 A1 discloses a printer for multi-color printing that contains four printer units, each having a respective photoconductor. The apparatus disclosed therein for avoiding registration errors requires a complicated adjustment procedure wherein what are referred as eccentricity phases must be taken into consideration.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a printer that enables a high-quality multi-color printing with a relatively simple structure and that can be adapted to different printing jobs with respect to the registration precision between specific color separations.
This object is achieved by a printer comprising a conveyor for conveying the final image carrier, a first printer unit for generating a first toner image on a basis of a first arrangement of color particles on a first photoconductor, at least one further printer unit for generating a further toner image on a basis of a further arrangement of color particles on a further photoconductor, a transfer station for the direct or indirect transfer of the first toner image from the first photoconductor and of the further toner image from the further photoconductor onto a surface section on the front side of the final image carrier, and an assembly for acceptance of the first printer unit in a first receptacle and for acceptance of a further printer unit in a further receptacle, a first developer station for application of color particles of a first color with a first polarity onto at least one first surface element of the first photoconductor, a second developer station contained in the first printer unit for applying color particles of a second color different from the first color with a second polarity opposite the first polarity onto at least one second surface element of the first photoconductor. A printer of the present invention has an assembly for accepting the first printer unit in a first receptacle and for accepting the further printer unit in a further receptacle. Since the receptacles are arranged in an assembly, the spatial distance between the receptacles is slight. The receptacles are preferably arranged immediately next to one another. The printer of the invention thus requires little installation space. A multitude of printing possibilities derive as a result of two printer units arranged following one another. Thus, for example, toner images can be printed on top of one another, as a result whereof subtractive color mixing can be achieved.
The invention is based on the perception that the picture elements when applying a toner image do not deviate from their predetermined positions (to result in exact-registration printing). The color particles of two colors are therefore applied in the invention when applying one of the toner images with two developer stations that are arranged in the same printer unit and at the same photoconductor. An additive color mixing is thus already possible within a toner image. For example, a printer unit can realize the method disclosed by U.S. Pat. No. 4,078,929 that is also known under the name “Tri-Level Method”. A registration error is unavoidable given toner images produced by different printer units.
The first receptacle and the further receptacle in an exemplary embodiment of the invention have essentially the same structure in the invention and the printer units are detachably introduced into the receptacles. As a result of the identical structure of the receptacles and the detachability of the printer units, it is assured that printer units can be replaced with one another and that an expedient number of printer units can be introduced into the receptacles dependent on the print quality required. An adaptation of the improved or, respectively, newly developed printer units is possible when care is exercised in the design of these printer units to see that they can be introduced into the receptacles.
In the invention, at least one of the printer units is detachable introduced into one of the receptacles, i.e. this printer unit can be introduced into the respective receptacle in a simple fashion or, respectively, can be removed from this receptacle. Included within the space of this invention are all measures known to a person skilled in the art such as, for example, latching or interlocking the respective printer unit in the receptacle. What this measure achieves is that the printer of the invention can be adapted to different printing jobs fast, i.e. with few manipulations, in that the detachable printer unit is removed or introduced or, respectively, is replaced by a different printer unit. Moreover, a replacement of developer stations in the printer unit, a replenishing of toner and the implementation of maintenance work are facilitated in that a printer unit is removed from the assembly for the respective activity and is reintroduced after the end of the activity.
The printer of the invention can print the final image carrier, for example sheet-shaped material that is preferably paper, directly or indirectly. Given indirect printing, an intermediate carrier is employed onto which the toner images are transferred before they are ultimately transferred onto the final image the carrier. Wherein an intermediate carrier is employed as carrier material in an exemplary embodiment of the invention, then—among other things—the superimposition of the toner images of different printer units can ensue more exac
Maess Volkhard
Schleusener Martin
Adams Russell
Nguyen Hung Henry
Oce Printing Systems GmbH
Schiff & Hardin & Waite
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