Charge density control for an electrostatic copier

Details Charge density control for an electrostatic copier Charge density control for an electrostatic copier

1979-11-19

1982-01-26

Braun, Fred L.

Photocopying

Projection printing and copying cameras

Combined with or convertible to a contact printer

355 3CH, 355 77, 430 30, G03G 1500

Patent

active

043125891

ABSTRACT:
An electrophotographic copier having a toner concentration control apparatus which periodically effects a toner-patch test cycle during which the optical density of toner deposited on a photoconductor test area is measured, as by light reflectance. A time period of copier non-use, exceeding a preset time period, or a copier on/off operation, referred to as critical events, results in a transient mode of copier operation which includes reduction of photoconductor charge magnitude during the next subsequent use, independent of the extent of the prior copier use history. During such subsequent use, the toner-patch test cycle is operable to effect closed-loop control of changing the photoconductor's charge magnitude back to its nominal working value. More specifically, so long as the results of a toner-patch test cycle indicate an acceptable toner density, the photoconductor charge magnitude is maintained at a lower than working level. As the results of the toner-patch test cycle periodically indicate lower than acceptable toner density, as by a high light reflectance off the test patch, the photconductor's charge magnitude is periodically increased until finally the working charge magnitude is reached. The results of the toner-patch test cycle are operable to add toner to the copier's developer only when the photoconductor's charge magnitude has been increased to at or near the working magnitude.

REFERENCES:
patent: 2956487 (1960-10-01), Giaimo
patent: 3976374 (1976-08-01), Hickman
patent: 4032227 (1977-06-01), Hubbard et al.
patent: 4105324 (1978-08-01), Seil

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