Photocopying – Contact printing – Light boxes
Patent
1990-02-13
1993-03-09
Pendegrass, Joan H.
Photocopying
Contact printing
Light boxes
3461531, G03G 2100, G03G 1504
Patent
active
051929732
DESCRIPTION:
BRIEF SUMMARY
The invention is directed to a character generator for a printing device operating according to the principle of electrophotography.
Printing devices operating according to the principle of electrophotography contain optical character generators. These optical character generators have the job of converting the printing information present in the form of electronic data into an optical image with which a photoconductive layer, for example a photoconductive drum, is then exposed. The exposed image is subsequently developed in a known fashion and is transferred, for example onto paper.
The light exit region of such optical character generators is situated in the immediate proximity of the photoconductive drum or, respectively, of the recording medium.
In electrophotographic printing devices, the charge image generated on the recording medium (photoconductive drum) via the optical character generator is inked with the assistance of a developing means, whereby one-component or two-component developers (toner) are employed.
Given employment of optical character generators in electrophotographic printing devices, there is the risk that the light exit region of the character generators will be contaminated by toner or dust. This disturbs the character generation in lasting fashion, because it significantly reduces the incident light power.
Such optical character generators that are composed of a LED ledge with allocated focusing means are disclosed by WO-Al-87/02162.
This known character generator for a printing device operating according to the principle of electrophotography comprises the following features: the surface of the character generator are arranged on a carrier part, represents a type of covering means for the light exit region of the light-emitting elements from the character generator, region in a covering condition and releases the light exit region in an operating condition.
The covering means FE, however, does not thereby serve to prevent the adhesion of dirt and certainly does not serve as a cleaning means. It serves only as carrier element for the photo element FE.
U.S. Pat. No. 4,515,491 discloses a movable covering means having operating and idle position in a printer in order to prevent the penetration of dirt into the paper slot.
This, however, does thereby not involve an electrophotographic printer and the covering means does not cover the light exit region of light-emitting elements.
GB-A-1 008 965 and U.S. Pat. No. 3,710,099 disclose air-operated cleaning mechanisms for the light exit region in an optical sorting system.
These thereby do not involve a character generator, let alone a multi-purpose means for covering and cleaning.
Patent Abstracts of Japan, Volume 10, No. 318(M-503) (2274), Jul. 30, 1986 and JP-A-6 157 368 are concerned with a filter means for preventing the penetration of dirt into a mechanical printer, but are not concerned with a multi-purpose means for a character generator conforming to patent claim 1.
It is therefore an object of the invention to offer a device for a character generator of an electrophotographic printing device that enables the light exit region to be protected against deposits of dirt or, respectively, to offer a device that prevents dirt from adhering to the light exit region.
In a character generator of the type initially cited, this object is achieved according to patent claim 1.
Advantageous embodiments of the invention are characterized in the subclaims.
The covering and cleaning device covers the light exit region of the character generator when the printer is at a standstill as well as during service work and releases it in the operating condition.
An adequate protection against damage and against the deposit of dust is thus guaranteed.
It is also advantageously possible to clean the light exit region with the covering and cleaning device. Cleaning can occur either mechanically. For example, a lip or some other stripper element is arranged at a pivotable diaphragm element, this lip or other stripper element brushing the light exit region of
REFERENCES:
patent: 3710099 (1973-01-01), Chapman
patent: 4515491 (1985-05-01), Chevrel et al.
Pendegrass Joan H.
Siemens Aktiengesellschaft
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