Electrophotography – Having particular structure – Modular or displaceable
Reexamination Certificate
1997-05-12
2001-10-23
Moses, R. L. (Department: 2105)
Electrophotography
Having particular structure
Modular or displaceable
Reexamination Certificate
active
06308028
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process cartridge, a method for assembling a process cartridge and an image forming apparatus having the cartridge. The image forming apparatus may be, for example, a laser beam printer, an electrophotographic copying machine, a facsimile machine,, a word processor or the like.
2. Related Background Art
In the past, a so-called process cartridge wherein a photosensitive drum, a charger, a developing device, a cleaning device and the like are integrally contained in a cartridge housing, which can be removably mounted to an image forming apparatus, has been put into practical use (for example, as disclosed in U.S. Pat. Nos. 3,985,436, 4,500,195, 4,540,268 and 4,627,701).
Generally, a photosensitive drum is electrically earthed to keep the charging charge on a surface of the drum to a predetermined constant value. Further, a charger means is supplied with a voltage to uniformly charge the photosensitive drum and a developing device is also supplied with a voltage to form a toner image on the photosensitive drum. Accordingly, when an image forming station is constituted by a process cartridge, the cartridge must have electric contacts for electrical connection to an image forming apparatus.
However, for example, when an electric contact for electrically earthing the photosensitive drum is positioned near an electric contact for applying an AC voltage, and particularly, an electric contact for applying a charging voltage, the following disadvantages are apt to occur. That is to say, when the process cartridge is mounted to the image forming apparatus, the electric contact of the cartridge for applying the AC voltage is electrically connected to the electric contact of the apparatus for applying the AC voltage.
On the other hand, the electric contact of the cartridge for applying the AC voltage is connected to a power source via wiring. Accordingly, if the electric contact for electrically earthing the photosensitive drum is positioned near the electric contact for applying the charging voltage, the earthing contact will be disposed near the AC wiring of the apparatus, thus generating the stray capacity between the earthing contact and the AC wiring. The stray capacity causes the escape of the current to be applied to the charger, from the AC wiring to the earthing contact, thereby worsening the ability of the charger.
Further, in an apparatus wherein AC voltages are applied to both a developing device and a charger, if the AC voltage applying contacts are arranged near each other, interference will occur between the contacts. That is to say, generally, since the charging voltage has a frequency lower than that of the developing voltage, the value of the charging voltage is changed by such interference, thus causing the charging discrepancy.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a process cartridge, a method for assembling a process cartridge and an image forming apparatus, which can obtain a high quality image.
Another object of the present invention is to provide a process cartridge, a method for assembling a process cartridge and an image forming apparatus, wherein the electrical connection between the process cartridge and the image forming apparatus can be achieved surely and effectively.
A further object of the present invention is to provide a process cartridge, a method for assembling a process cartridge and an image forming apparatus, which can prevent the occurrence of the charging discrepancy.
A still further object of the present invention is to provide a process cartridge, a method for assembling a process cartridge and an image forming apparatus, wherein a conductive member for earthing an image bearing member and a charging conductive member are spaced apart from each other on both sides of an axis of the image bearing member so that there is no interference between the conductive members, thereby preventing the occurrence of stray capacity.
The other object of the present invention is to provide a process cartridge, a method for assembling a process cartridge and an image forming apparatus, wherein the electrical connection between the process cartridge and the image forming apparatus can be effected reasonably.
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Yuji Murata, “Surface Polymer, and Electrostatics”, Surface Film Molecule Design Series, vol. 5, Japan Surface Science Associates, ©1988, pp. 13-16, Section 4.1 (Japanese document with English translation of cited section).
Karakama Toshiyuki
Numagami Atsushi
Yashiro Masahiko
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