Duplex Theory Of Operation - Lexmark C720 Service Manual

5024-001

Duplex Theory of Operation

The duplex unit allows the printer to print on both sides of a sheet of
paper. The duplex unit uses two motors to move the paper from the
paper exit of the printer through the duplex unit. The paper is fed
back into the printer through the attached lower feed unit.
The duplex sequence of paper movement is as follows:
1. Paper exits the printer through the top instead of the paper exit
bin.
This is accomplished by an upper solenoid (DSOL-U) in the
duplex unit moving the upper shutter assembly directing paper
into the duplex unit.
2. The upper duplex transport motor 2 (DPM2) and rollers feed the
paper into the duplex unit.
3. The paper is stopped, by the duplex registration roller, for
staging.
The paper passes over a paper sensor (PT5) which indicates a
paper present signal.
4. The lower duplex motor 1 (DPM1) is energized and the paper is
directed from the duplex registration roller through the lower
shutter switching the direction of the paper to the paper reverse
and transport unit.
5. The lower shutter direction is changed by the lower duplex
solenoid (DSOL) allowing the paper to be driven by the duplex
motor 1 (DPM1) into the lower feed unit transport rollers.
6. The paper passes over another paper sensor (PT4) for a paper
present signal.
7. The lower feed unit transport rollers are driven by the lower feed
transport clutch (DPKCL) and delivers the paper to the printers
registration roller.
8. The paper is then printed on and passed out of the printer
through the top output bin.
General Information
1-49