Xerox Phaser 8860 Service Manual page 296

Document Feeder Functions
The Duplex Automatic Document Feeder (DADF) is capable of automatically feeding original
documents from the input tray and scanning either side document or both sides of a double-
sided document.
DADF Components
Input Tray The tray feeds document originals into the DADF for simplex (single-
sided) or duplex (double-sided) scanning. Tray capacity is 50 originals.
Output Tray Original documents fed through the DADF exit to the Output Tray.
Media In Sensor The Media In Sensor detects the presence of documents in the input tray.
After a delay to allow for adjusting the feed guides, the media is drawn to
the Media Staged Sensor.
Media Staged This sensor, located within the DADF scanhead, detects whether media
Sensor has been fed into the DADF to a predetermined (staged) point. When the
scanner detects this point, it starts collecting data from the Charge Cou-
pled Device (CCD).
DADF Cover This optical sensor detects the status of the DADF access cover. When
Open Sensor the cover is open, DADF operation is inhibited; given sufficient time, an
error message appears on the Control Panel display instructing the user
to close the access cover.
Pick Roller and The pick roller is the first of several feed rollers. It is designed to work with
Separator Pad the separator pad to ensure that only one sheet of media is fed at a time.
Feed and Idler Three additional feed rollers in the DADF are responsible for media trans-
Rollers port through the media path. They include associated idler rollers to
maintain proper media tension. This ensures proper imaging while pro-
viding the minimal chance for damage to the original document(s).
Drive Motor A stepper motor is housed in the DADF to drive the pick and feed rollers,
and moves the calibration shutter into position. The connection is through
a toothed belt and gear drive.
DADF Scanhead The DADF utilizes a stationary scanhead containing the imaging CCD.
and Lamp This scanhead is only for scanning the second side of a duplex original.
The lamp is a Cold Cathode Fluorescent Lamp (CCFL). The CCFL is
powered through a chopper board. It is supplied with a variable DC input
(Up to +24 VDC) and generates +600 VDC to +900 VDC depending on
the supply voltage.
DADF Connector An electrical connector on the rear of the DADF connects to the rear of
the flatbed portion of the IIT. The DADF communicates with the Scanner
and the IOT. The image information is also passed to the Scanner and
then sent to the IOT. There is no direct communication between the
DADF and IOT.
DADF Hinges Mechanical connection between the DADF and the Scanner consists of
a set of hinges. These hinges allow for the DADF to lift from the platen
glass to facilitate copying. The hinges are designed to lock when the IIT is
opened for adding consumables or removing media jams. In order to
unlock the hinges, the IIT must be closed.
Theory of Operation
Image Input Terminal
Document Feeder Paper Path and Imaging
The pick roller feeds paper from the input tray to the document feeder. The paper then passes
between the DADF scanhead and the flatbed scanhead. Mylar strips guide the original docu-
ment back out the document feeder and into the output tray.
The imaging path of the DADF is referred to as a Constant Velocity Transport (CVT) design.
This design compensates for differences in the operating speed of any of the drive rollers,
thereby reducing the chance of damage to the original or of varying the distance between the
imaging device and the target document.
Copy/Scan Imaging
When using the document feeder for a copy or a scan, the DADF scanhead scans the second
side of the original at the same time the flatbed scanhead scans the first side of the original.
The scanhead in the document feeder is stationary.
Data is transferred from the IIT to the IOT through the electrical connections to an image pro-
cessing board in the Electronics Module. This processing board receives the RGB channel
data and translates it into a data stream that the print engine controller can understand. This
data is either transferred to the engine driver (for copy service) or to the hard drive controller
(for scan service).
Scanner Assembly Functions
Scanner Assembly Components
Document Glass The scanner platen is used for copying or scanning original documents
or Platen and images. The platen functions well for media outside the operating
range of the DADF (16 lb.-32 lb.), fragile or damaged originals, photo-
graphs, or large (or bound) items such as books or periodicals.
Scanhead and The Flatbed portion of the IIT contains a moveable scanhead that
Lamp includes the CCD imaging board, main control board, drive motor, and
lamp assembly. The lamps are Cold Cathode Fluorescent Lamps (same
as the lamps in the DADF).
CVT Window This portion of the platen is a part of the DADF media path. The principal
function of this window is to allow the lower scanhead to image the first
side of an original being fed through the DADF.
IIT Connector An electrical connection on the rear of the Flatbed portion of the IIT con-
nects to a receptacle on the IOT completing the signal path for image
data from the IIT, power to the IIT, and system communications between
the three components.
Control Panel The Control Panel is the user interface with the system.
Scanner and Document Feeder Calibration
Automatic Calibration
The automatic calibration performed by the system is a "white balance" calibration performed
during startup and at pre-programmed intervals of operation. This calibration ensures that the
system detects the response to a given calibration spot and determines the effects of lamp
temperature and age on the image quality of the system.
09/2007
8-4
Initial Issue
Phaser 8860/8860MFP Service Manual