Lexmark MX310 Service Manual page 482

ADF paper path
The duplex ADF enables the user to create duplex scans automatically, eliminating the need to stop the
scanning process to flip the media being duplicated over. The ADF uses DC motors with encoder wheels, and
a series of sensors to determine the media's position in the paper path during the scan process. The following
steps are performed in creating a duplex scan on the duplex ADF:
Note: The simplex ADF uses only one motor for all paper transport functions, and does not have deskew
capabilities. The scanner control unit, on the controller board receives a command to create a scan, fax, or
copy.
1
The scanner control unit, on the controller board receives a command to create a scan, fax, or copy.
2
A signal is sent to the ADF to poll the document sensor (1) to check if the media to be scanned is in the
correct position. The media must be placed in the ADF input tray so it actuates the document sensor. If the
ADF document sensor isn't actuated, a flatbed scan is run by default.
3
If the media has actuated the document sensor, then an ADF scan is executed. At this point the pickup roller
(2) on the pick arm assembly drops and advances the paper into the ADF. To minimize the possibility of
multiple sheets being fed, a counter rotating separator roll (3) is used. After passing through pick assembly,
the media actuates the stage and interval sensors (4). Actuating these sensors determines that this will be
the first side of the document to be scanned.
4
In addition the stage sensors are used to determine and correct document skew if it is present. If the stage
sensors are actuated at different times, then the paper is slowly fed to the paper feed 1 roller. The feed motor
encoder wheel count tracks the paper location in the paper path.
5
When the paper reaches the paper feed 1 roller (5), the stationary state of the paper feed 1 roller acts as a
registration roll, causing the paper to deskew.
6
When the encoder count reaches a certain count, the paper feed 1 roller advances the now deskewed paper
to the paper feed 2 roller (6) and the feed sensor (7). If the paper does not actuate the feed sensor before
a certain encoder count is attained, a paper jam error is generated.
7
When the feed sensor is actuated the paper advances to the scan area (8). While the paper is advancing to
the scan area, the DC motor encoder generates a count which is stored in an on-board counter. These
counts along with the feed sensor ensure that the media is traveling at the correct speed through the scan
area. The speed the document travels through the ADF scan area is dependent on the image DPI specified
by the user.
# Part
3 Separator roller
4 Stage and interval sensors
5 Paper feed 1 roller
6 Paper feed 2 roller
7 Feed sensor
8 Scan area
9 Duplex sensor
10 Eject 2 roll
11 Exit roller
Theory of operation
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