Photocopying – Contact printing – Light boxes
Patent
1989-03-22
1991-06-11
Moses, R. L.
Photocopying
Contact printing
Light boxes
355266, 355296, 118652, G03G 2100
Patent
active
050236644
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is directed to a non-mechanical printer or copier means having a developing region for developing a charge region generated on a charge image carrier with the assistance of an exposure means using a developer mix of toner particles and carrier particles.
In copier equipment technology and in non-mechanical fast data printers that operate based on the principle of electrophotography, charge images are generated on a charge image carrier, for example on a photoconductive drum, and are subsequently inked with a colored powder, toner in a developer station. The toner images are subsequently transferred onto normal paper given employment of a photoconductive drum and are fixed there.
As a rule, a two-component developer is employed for developing, this being composed of ferromagnetic carrier particles and of colored toner particles. The developer mix, for example, is conducted past the charge image on the charge image carrier with a magnetic brush arrangement, the toner particles adhering to the charge image as a result of electrostatic forces. The magnetic brush arrangement is thereby composed of a rotatable hollow cylinder in whose interior a plurality of rows of stationary permanent magnets are arranged.
A plurality of magnetic brush arrangements can be provided in one developer station. For example, one magnetic brush arrangement can serve the purpose of transporting the developer mix past the charge image carrier. This magnetic brush arrangement shall be referred to below as a developer drum. A further magnetic brush arrangement can be employed in order to transport the developer mix out of the inside of the developer station to the developer drum. Such a magnetic brush arrangement or any other arrangement that effects such a transport of developer mix is thereby referred to below as a transport drum.
Adjoining the development region, it is also standard to remove the carrier particles of the developer mix sporadically adhering to the charge image carrier from the charge image carrier with the assistance of a carrier stripper roller likewise fashioned as magnetic brush drum and to return these carrier particles to the developer mix.
Developer stations wherein developer mix for inking the charge images on the charge image carrier with the assistance of the magnetic brush principle are employed are disclosed by German Patent 31 19 010 and corresponding U.S. Pat. No. 4,461,238.
As already set forth, a significant problem in non-mechanical printer or copier devices operating according to the principle of electrophotography is achieving the complete removal of the carrier particles from the inked charge image following the development region. In standard non-mechanical printer or copier devices that work according to the reversal development method and wherein the regions of the charge image carrier discharged via a character generator are inked, there is the risk that the carrier particles will agglomerate to those regions that are still charged and that are not to be inked. The complete removal of these carrier particles with the assistance of a carrier stripper drum is difficult.
When these carrier particles are not completely removed or, respectively, when these carrier particles are entrained by the photoconductive layer of the photoconductive drum up to the actual transfer station, then the transfer event is deteriorated. In particular, this leads to light spots and other disturbances in the printed format.
GB-A- 15 24 543 and corresponding U.S. Pat. No. 3,920,329; discloses an electrophotographic copier means that comprises an isorunning development station. The development station is followed by a carrier stripper drum that serves the purpose of removing excess developer mix from the charge image carrier. A corona discharge station is arranged between the carrier stripper drum and the development station. Corona discharge stations, however, have the disadvantage that they act both on the inked regions as well as on the non-inked regions of the charge image.
In
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Baier Erich
Koefferlein Rainer
Schlageter Bernhard
Moses R. L.
Siemens Aktiengesellschaft
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