Electrophotography – Image formation – Transfer
Reexamination Certificate
2002-06-07
2004-07-20
Royer, William J. (Department: 2852)
Electrophotography
Image formation
Transfer
C399S317000
Reexamination Certificate
active
06766138
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a reprographic printing machine. More specifically, the present invention pertains to an apparatus for assisting the transfer of a developed image from an imaging surface, such as a photoconductive surface or intermediate image transfer surface, to a print sheet, such as paper, by optimizing the contact between the print sheet and the imaging surface. The present invention also pertains to such a transfer assist apparatus including a variable length transfer assist blade that may be adjusted for a plurality of different size print sheets.
BACKGROUND OF THE INVENTION
FIG. 1
is a schematic illustration of a typical electrophotographic printing machine
10
that may employ a transfer assist blade according to the present invention (not shown in FIG.
1
). The illustrated printing machine
10
includes a conventional photoconductive layer or light sensitive surface
12
on a conductive backing in the form of a photoconductive belt
14
. The photoconductive belt
14
is mounted on a plurality of rollers journaled in a machine frame (not shown), in order to rotate the photoconductive belt
14
and cause the photoconductive layer
12
to pass sequentially through a plurality of reprographic process stations A through E.
The several generally conventional processing stations A through E in the path of movement of the photoconductive layer
12
may be as follows. A charging station A, where the photoconductive layer
12
of the photoconductive belt
14
is uniformly charged. An exposure station B, where a light or radiation pattern of a document to be printed is projected onto the photoconductive layer
12
to expose and discharge select areas of the photoconductive layer
12
to form a latent image thereon. A developing station C, where developer material is applied to the photoconductive layer
12
of the photoconductive belt
14
to generate a toner image on the photoconductive layer
12
. A transfer station D, where the toner image is electrostatically transferred from the photoconductive surface to a print sheet
30
. Finally, a cleaning station E, where the photoconductive surface is brushed or otherwise cleared of residual toner particles remaining thereon after image transfer.
In order to generate multi-color prints, there may be a group of processing stations A through E for each of a plurality of colors. For example, there may be a group of stations A through E for each of yellow, cyan, magenta and black. One method of generating multicolor prints is to arrange all of the color stations around a single photoreceptor and generate a toner image on the photoreceptor for each color, one color at a time. After each individual color toner image is formed on the photoreceptor, it is transferred to an intermediate transfer surface before the next color toner image is generated. This is repeated for each color, thereby building up a full color toner image on the intermediate transfer surface. The full color toner image is then transferred from the intermediate transfer surface to the print sheet. The intermediate transfer surface may be formed on an intermediate transfer belt, roll, drum or other suitable structure. Alternatively, a separate photoreceptor may be provided for each color. In which case, each color toner image is formed on the corresponding photoreceptor and transferred to the intermediate transfer surface, thereby creating a multi-color toner image on the intermediate transfer surface. The multi-color toner image is then transferred from the intermediate transfer surface to the print sheet.
Another method of generating full color prints is to arrange all of the color processing stations around a single photoreceptor and form all of the color toner images, one on top of each other, during a single rotation of the photoreceptor. The full color toner image may then be transferred from the photoreceptor to the print sheet, eliminating the need for an intermediate transfer surface.
Print sheets
30
, such as paper or other print substrate, supplied from a sheet feeding tray or sheet feeding module
16
, are fed by a series of sheet feeding rollers and guide rails to the transfer station D. At the transfer station D, the developed toner image is transferred from the photoconductive belt
14
(or intermediate transfer surface) to the print sheet
30
. The print sheet
30
is then stripped from the photoconductive belt
14
by a sheet stripper and transported to a fusing station F, where a fuser
20
fuses the toner image onto the print sheet
30
in a known manner. The print sheet
30
, which now has an image fused to a first face thereof, is then transported by a plurality of rollers to an output tray or stacking module
26
for one-sided or simplex copying. It will be appreciated that the print sheet may pass directly into the stacking module
26
. It will also be appreciated that the print sheet may be inverted prior to entering the stacking module
26
or may be inverted and returned to the developing station C for duplex printing.
The various machine operations are regulated by a controller which is preferably a programmable microprocessor capable of managing all of the machine functions and subsystems. Programming conventional or general purpose microprocessors to execute imaging, printing, document, and sheet handling control functions with software instructions and logic is well known and commonplace in the art. Such programming or software will, of course, vary, depending on the particular machine configuration, functions, software type, and microprocessor or other computer system utilized. Those of skill in the software and/or computer arts can readily program the microprocessor and/or otherwise generate the necessary programming from functional descriptions, such as those provided herein, or from general knowledge of conventional functions together with general knowledge in the software and computer arts without undue experimentation. The operation of the exemplary systems described herein may be accomplished by conventional user interface control inputs selected by the operator from the printing machine consoles. Conventional sheet path sensors or switches may be utilized to keep track of the position of documents and print sheets in the machine
10
.
The electrophotographic printing process and machine
10
described above, and variations thereof, are well known and are commonly used for light lens copying and digital printing and photocopying. In digital printing and photocopying processes, a latent image is produced by modulating a laser beam or by selectively energizing light emitting diodes in an array of diodes. A digital original may be created digitally in any known manner, or may be a digital image of a hard copy that was previously scanned, digitized and stored in memory. In ionographic printing and reproduction, a charge is selectively deposited on a charge retentive surface in response to an electronically generated or stored image. It should be understood that a drum photoreceptor, or flash exposure may be alternatively employed.
The process of transferring charged toner particles from an image bearing member, such as the photoconductive belt or an intermediate transfer member to a print sheet is accomplished in a reprographic machine by overcoming the adhesive and electrostatic forces holding the toner particles to the image bearing member. This has been accomplished, for example, via electrostatic induction using a corona generating device. The print sheet is placed in direct contact with the developed toner image on the image bearing member, while the reverse side of the print sheet is exposed to a corona discharge. The corona discharge generates ions having a polarity opposite that of the toner particles on the image bearing member. The ions electrostatically attract the toner particles from the image bearing member and into contact with the print sheet, thereby transferring the toner particles from the image bearing member to the print sheet. Other forces, such as mechanical press
Atwood Mark A.
Bonacci Andrew J.
Obrien Brendan P.
Royer William J.
Xerox Corporation
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