Electrophotography – Control of electrophotography process
Reexamination Certificate
1999-12-23
2001-01-30
Chen, Sophia S. (Department: 2852)
Electrophotography
Control of electrophotography process
C347S116000, C399S162000, C399S298000, C399S301000
Reexamination Certificate
active
06181887
ABSTRACT:
This invention relates generally to a control system for an electrophotographic printing machine and, more particularly, concerns a system which utilizes a variable pitch virtual belt hole scheme to control the formation of latent images on a photoconductive belt member.
In a typical electrophotographic printing process, a photoconductive member is charged to a substantially uniform potential so as to sensitize the surface thereof. The charged portion of the photoconductive member is exposed to a light image of an original document being reproduced. Exposure of the charged photoconductive member selectively dissipates the charges thereon in the irradiated areas. This records an electrostatic latent image on the photoconductive member corresponding to the informational areas contained within the original document. After the electrostatic latent image is recorded on the photoconductive member, the latent image is developed by bringing a developer material into contact therewith. Generally, the developer material comprises toner particles adhering triboelectrically to carrier granules. The toner particles are attracted from the carrier granules to the latent image forming a toner powder image on the photoconductive member. The toner powder image is then transferred from the photoconductive member to a copy sheet. The toner particles are heated to permanently affix the powder image to the copy sheet.
The foregoing generally describes a typical black and white electrophotographic printing machine. With the advent of multicolor electrophotography, it is desirable to use an architecture which comprises a plurality of image forming stations. One example of the plural image forming station architecture utilizes an image-on-image (IOI) system in which the photoreceptive member is recharged, reimaged and developed for each color separation. This charging, imaging, developing and recharging, reimaging and developing, all followed by transfer to paper, is done in a single revolution of the photoreceptor in so-called single pass machines, while multipass architectures form each color separation with a single charge, image and develop, with separate transfer operations for each color.
In single pass color machines and other high speed printers it is desirable to utilize as much of the surface area of the photoreceptor as possible to improve the efficiency and print speed of the printer. The photoreceptor typically has a seam therein which is an area of the photoreceptor that is unuseable for developing images thereon. A standard way of marking the seam is to have a hole located at a known distance therefrom and to trigger image formation from that hole. Many print jobs, however vary in the size of media used and it is therefore desirable to utilize the photoreceptor in what is known as a variable pitch mode. It is further desirable to utilize this variable pitch mode without having to change the belt to vary the pitch number for the particular print job.
In accordance with one aspect of the present invention, there is provided a system for controlling the imaging device in a single pass multi color electrophotographic printing machine, comprising a photoconductive member defining a timing aperture, the member moving along a path in a printing machine and a plurality of imaging devices, each one of the plurality of imaging devices writing a latent image on the photoconductive member. The system further includes a sensor, located adjacent the photoconductive member, to sense the aperture in the photoconductive member as it passes the sensor and generate a signal indicative thereof and a control device, which generates a timing signal for each of the plurality of imaging devices as a function of the signal generated by the sensor and a plurality of predetermined parameters.
In accordance with yet another aspect of the invention there is provided a method of controlling the formation of images on a photoconductive member in a multi color single pass electrophotographic printing machine comprising sensing a timing aperture in the photoconductive member as the member moves along a path in a printing machine and generating a timing signal for each of a plurality of imaging devices as a function of the signal sensed and a plurality of predetermined parameters.
REFERENCES:
patent: 5291245 (1994-03-01), Charnitski et al.
patent: 5784676 (1998-07-01), Iseki et al.
Hughes David A.
Lacayo Orlando J.
Monahan Michael B.
Chen Sophia S.
Eipert William F.
Kepner Kevin R.
Xerox Corporation
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