Incremental printing of symbolic information – Electric marking apparatus or processes – Electrostatic
Reexamination Certificate
2002-01-30
2003-12-09
Pendegrass, Joan (Department: 2852)
Incremental printing of symbolic information
Electric marking apparatus or processes
Electrostatic
C347S137000, C347S256000, C359S737000
Reexamination Certificate
active
06661441
ABSTRACT:
BACKGROUND AND SUMMARY
Xerographic printing and reproduction machines, such as that shown schematically in
FIG. 1
, typically include raster scanners: raster output scanners (ROSs) for printing and raster input scanners (RISs) for image acquisition in reproduction. In raster scanning systems, an imaging light beam scans across a rotating polygon to a movable photoconductive member, recording or writing electrostatic latent images on the member. Generally, a ROS has a laser for generating a collimated beam of monochromatic radiation. The laser beam is modulated in conformance with the image information. The modulated beam is reflected through a lens onto a scanning element, typically a rotating polygon having mirrored facets. Many machines use one ROS for each color being printed, the ROS exposing the photoreceptor to light in a pattern representing an image to be printed, as is known in the art. In multipass machines, a single ROS can write the image for each color. The pattern on the exposed photoreceptor is then used to deposit toner on a substrate, which toner is then fused onto the substrate to produce the final printed image.
As an example of the environment in which embodiments can be employed,
FIG. 1
schematically illustrates an electrophotographic printing machine
1
that uses raster scanners (RIS
128
and ROS
130
) and generally employs a photoconductive belt
12
. Preferably, the photoconductive belt
12
is made from a photoconductive material coated on a ground layer, which, in turn, is coated on an anti-curl backing layer. Belt
12
moves in the direction of arrow
18
to advance successive portions sequentially through the various processing stations disposed about the path of movement thereof. Belt
12
is entrained about stripping roller
14
, tensioning roller
15
and drive roller
16
. As roller
16
rotates, it advances belt
12
in the direction of arrow
13
.
Initially, a portion of the photoconductive surface passes through charging station A. At charging station A, a corona generating device indicated generally by the reference numeral
122
charges the photoconductive belt
12
to a relatively high, substantially uniform potential.
At an exposure station, B, a controller or electronic subsystem (ESS), indicated generally by reference numeral
129
, receives the image signals representing the desired output image and processes these signals to convert them to a continuous tone or greyscale rendition of the image which is transmitted to a modulated output generator, for example the raster output scanner (ROS), indicated generally by reference numeral
130
. Preferably, ESS
129
is a self-contained, dedicated minicomputer. The image signals transmitted to ESS
129
may originate from a RIS as described above or from a computer, thereby enabling the electrophotographic printing machine to serve as a remotely located printer for one or more computers. Alternatively, the printer may serve as a dedicated printer for a high-speed computer. The signals from ESS
129
, corresponding to the continuous tone image desired to be reproduced by the printing machine, are transmitted to ROS
130
. ROS
130
includes a laser with rotating polygon mirror blocks. The ROS will expose the photoconductive belt to record an electrostatic latent image thereon corresponding to the continuous tone image received from ESS
129
. As an alternative, ROS
130
may employ a linear array of light emitting diodes (LEDs) arranged to illuminate the charged portion of photoconductive belt
12
on a raster-by-raster basis.
After the electrostatic latent image has been recorded on photoconductive surface, belt
12
advances the latent image to a development station, C, where toner, in the form of liquid or dry particles, is electrostatically attracted to the latent image using commonly known techniques. The latent image attracts toner particles from the carrier granules forming a toner powder image thereon. As successive electrostatic latent images are developed, toner particles are depleted from the developer material. A toner particle dispenser, indicated generally by the reference numeral
144
, dispenses toner particles into developer housing
146
of developer unit
138
.
With continued reference to
FIG. 1
, after the electrostatic latent image is developed, the toner powder image present on belt
12
advances to transfer station D. A print sheet
148
is advanced to the transfer station, D, by a sheet feeding apparatus,
150
. Preferably, sheet feeding apparatus
150
includes a nudger roll
151
which feeds the uppermost sheet of stack
154
to nip
155
formed by feed roll
152
and retard roll
153
. Feed roll
152
rotates to advance the sheet from stack
154
into vertical transport
156
. Vertical transport
156
directs the advancing sheet
148
of support material into the registration transport
120
of the invention herein, described in detail below, past image transfer station D to receive an image from photoreceptor belt
12
in a timed sequence so that the toner powder image formed thereon contacts the advancing sheet
148
at transfer station D. Transfer station D includes a corona generating device
158
which sprays ions onto the back side of sheet
148
. This attracts the toner powder image from photoconductive surface to sheet
148
. The sheet is then detacked from the photoreceptor by corona generating device
159
which sprays oppositely charged ions onto the back side of sheet
148
to assist in removing the sheet from the photoreceptor. After transfer, sheet
148
continues to move in the direction of arrow
60
by way of belt transport
162
which advances sheet
148
to fusing station F.
Fusing station F includes a fuser assembly indicated generally by the reference numeral
170
which permanently affixes the transferred toner powder image to the copy sheet. Preferably, fuser assembly
170
includes a heated fuser roller
172
and a pressure roller
174
with the powder image on the copy sheet contacting fuser roller
172
. The pressure roller is cammed against the fuser roller to provide the necessary pressure to fix the toner powder image to the copy sheet. The fuser roll is internally heated by a quartz lamp (not shown). Release agent, stored in a reservoir (not shown), is pumped to a metering roll (not shown). A trim blade (not shown) trims off the excess release agent. The release agent transfers to a donor roll (not shown) and then to the fuser roll
172
.
The sheet then passes through fuser
170
where the image is permanently fixed or fused to the sheet. After passing through fuser
170
, a gate
180
either allows the sheet to move directly via output
184
to a finisher or stacker, or deflects the sheet into the duplex path
100
, specifically, first into single sheet inverter
182
here. That is, if the sheet is either a simplex sheet, or a completed duplex sheet having both side one and side two images formed thereon, the sheet will be conveyed via gate
180
directly to output
184
. However, if the sheet is being duplexed and is then only printed with a side one image, the gate
180
will be positioned to deflect that sheet into the inverter
182
and into the duplex loop path
100
, where that sheet will be inverted and then fed to acceleration nip
102
and belt transports
110
, for recirculation back through transfer station D and fuser
170
for receiving and permanently fixing the side two image to the backside of that duplex sheet, before it exits via exit path
184
.
After the print sheet is separated from photoconductive surface of belt
12
, the residual toner/developer and paper fiber particles adhering to photoconductive surface are removed therefrom at cleaning station E. Cleaning station E includes a rotatably mounted fibrous brush in contact with photoconductive surface to disturb and remove paper fibers and a cleaning blade to remove the non-transferred toner particles. The blade may be configured in either a wiper or doctor position depending on the application. Subsequent to cleaning, a discharge lamp (not shown) floods p
Henn David E.
Pendegrass Joan
Xerox Corporation
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