Electrostatographic apparatus comprising developing bias means
US4266870A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 6, 1979 |
| Grant date | May 12, 1981 |
| Priority date | — |
| Expiry date | Mar 6, 1999 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03G15/065
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
An electrode (17) is provided adjacent to a photoconductive drum (12) to sense the background area potential at a leading edge of an electrostatic image on the drum (12). An electrically conductive shield (26) surrounds all surfaces of the electrode (17) except a surface which faces the drum (12). A voltage follower (18) has an input connected to the electrode (17) and an output connected to the shield (26). This makes the capacitance between the electrode (17) and the drum (12) much greater than the capacitance between the electrode (17) and ground. The surface of the electrode (17) facing the drum (12) is formed with a pattern of projections and depressions to increase the surface area thereof and thereby the capacitance between the electrode (17) and the drum (12). The output of the voltage follower (18) is connected through a sample and hold circuit (53), (54), (56), (57), (62) to a developing bias voltage generator (58), (69), (71) which applies a bias voltage to a developing unit (23) in accordance with the output of the voltage follower (18) and thereby the potential of the electrostatic image on the drum (12).
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.