Electrophotography – Control of electrophotography process – Of plural processes
Reexamination Certificate
2001-09-24
2002-12-24
Chen, Sophia S. (Department: 2852)
Electrophotography
Control of electrophotography process
Of plural processes
C399S066000, C399S297000, C399S384000
Reexamination Certificate
active
06498909
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention is directed to a method and to an apparatus for controlling an electrographic printing or copying process. The invention is particularly directed to a method and to a system for controlling the toner concentration in a toner/developer mixture.
EP 403 523 B1 discloses an electrographic process wherein a number of process parameters are monitored and regulated, including the toner concentration in a development station. It is provided for this purpose that a toner mark be generated on a photoconductor drum, that the mark be sensed on the photoconductor drum with a reflex light sensor, and the measured value be employed for the control of the toner resupply in the development station. The solid toner mark is thereby generated at the lateral edge of the photoconductor drum, so that it lies only in the region of the margin perforations with respect to the web-shaped, margin-perforated recording medium and thus does not lie in the actual writing region of the recording medium or of the photoconductor drum. A number of disadvantages result therefrom.
First, the toner mark can thus be only designed relatively small, as a result of which the sensing area and, thus, the measuring precision as well are limited, particularly transversely relative to the transport direction of the photoconductor drum or of the recording medium. Second, it is definitely meaningful for regulating various parameters of the electrographic process to also apply and sense a toner mark in the actual writing region of the photoconductor drum. Particularly when employing web-shaped recording media, for example what is referred to as continuous stock, however, spoilage then arises because the recording medium printed in this way is no longer available for being printed with other information. Conditioned by the process, third, edge effects, for example of the electrical field, arise at the edges of a photoconductor, as a result of which the expressiveness of a measurement in this region is diminished. Such edge effects superimpose all the more greatly the narrower a toner mark is.
WO 97/17635 A discloses an electrophotographic printer device that contains compensation elements, particularly rockers, springs and other prestressing elements, that are intended to avoid fluctuations in the position of the recording medium in the region of the transfer printing zone. This is particularly necessary in a duplex mode wherein the web-shaped recording medium is conducted twice through the same transfer printing station. However, nothing noteworthy can be derived from this publication with respect to the regulation of the electrographic process.
DE 198 01 521.6 (applicant's reference 980101DE) discloses a control method for the toner/developer mixture, what is referred to as a two-component development system, in an electrographic printer or copier device. in this method, a toner mark is sensed at least two places with respect to the transport direction of the photoconductor drum. In order to achieve an adequate sensing precision with this method, it is necessary that the toner mark be adequately broad. It would thereby be especially advantageous if the toner mark could also extend into the actual writing region of the photoconductor drum.
DE 197 49 651.2 (applicant's reference 971104DE) discloses an electrophotographic printer that can process both recording media with margin perforation as well as recording media without margin perforation. A unit with a friction drive is provided for this purpose and can be pivoted against and away from a photoconductor drum so precisely that the recording medium again comes to lie exactly at the original position with respect to the photoconductor drum after being pivoted away and back in. The components disclosed therein are designed therefor that the pivoting in and away occurs, for example, during the course of a service call. Such a printer, on the other hand, is suited for printing a recording medium without a margin perforation wider than a recording medium with a margin perforation. A recording medium free of margin perforations can then also be printed by the photoconductor drum in the region of the drum wherein the margin perforations are located given a margin-perforated recording medium. This advantage, however, is accompanied by the disadvantage that the toner mark must be transfer-printed onto the unperforated, web-shaped recording medium in its writing region and, thus, spoilage again arises.
U.S. Pat. No. 5,387,965 A and U.S. Pat. No. 4,468,112 A disclose electrographic processes wherein the toner concentration in a development station is identified and compared to a rated value. The rated value is dependent on a second measurement event in which a toner mark is interpreted.
SUMMARY OF THE INVENTION
An object of the invention is to specify a method and an electrographic system wherein a monitoring of toner density can occur and wherein an optimally high printing width on the recording medium can be achieved at the same time.
This object is achieved by a method and system of the invention for regulating an electrographic printing or copying process wherein information to be printed are generated as an intermediate toner image on an intermediate image carrier and are later transferred from a transfer printing surface onto a recording medium in a transfer printing zone. A toner mark is generated on an intermediate image carrier such as an electrographic intermediate image carrier. The toner mark on the intermediate image carrier is sensed at least in regions and the toner mark is subsequently in turn removed from the intermediate image carrier. The toner concentration in a development station is regulated with a measured value such as a density value. The transfer of the intermediate toner image from the transfer printing surface onto the recording medium is at least temporarily prevented in the time span between the generation and the removal of the toner mark.
According to a first aspect of the invention, the information to be printed are generated as an intermediate toner image on an intermediate image carrier with a photoconductor drum and, in a transfer printing zone, are transferred later from a transfer printing surface, for example from the surface of the photoconductor drum or from a transfer printing tape, onto a recording medium. For regulating the toner density, a toner mark is generated on the electrographic intermediate image carrier, the toner mark on the intermediate image carrier is sensed at least in regions, and the toner mark is in turn removed from the intermediate image carrier later. In particular, the density is sensed at the toner mark. The toner concentration is then regulated with the measured value, particularly density value, in a development station such that the inking can be kept constant. A transfer of the intermediate toner image from the transfer printing surface onto the recording medium is at least temporarily prevented in the time span between the generation of the toner mark on the intermediate image carrier and the removal of the toner mark from the intermediate image carrier. This impeding transfer of the transfer printing is particularly prevented during a time span wherein the toner mark passes the transfer printing zone. The prevention of the transfer printing can, in particular, occur by separation/lift-off of the recording medium from the transfer printing surface.
In particular, the invention provides two operating states for the operation of an electrographic printer or copier device. In the first operating state, what is referred to as the measurement cycle, a toner mark is generated on the intermediate image carrier, the density of the toner mark is sensed, and the toner mark is then in turn removed from the intermediate image carrier. The sensed toner density value is employed for the regulation of the toner concentration in the development station and, in particular, has influence on a toner concentration rated value and/or on a control threshold. In the second operating sta
Chen Sophia S.
Oce Printing Systems GmbH
Schiff & Hardin & Waite
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