Duplex Print Mechanism - Brother DCP6690CW Service Manual

3.2.2.5 Duplex print mechanism

The major components of the duplex print mechanism are a duplex print unit (duplex unit), link
gear holder DX ASSY (black), and link gear holder LT DX ASSY (white).
As described in
mechanisms eject the recording paper printed on its top face. In duplex printing, however, the
trailing edge of the paper is lightly held by the DX flapper (in the slightly backward-tilted
position) in the duplex unit.
To print on the bottom face, the machine further tilts the DX flapper backward and rotates the
SB roller in the backward direction to switch back the paper through the switchback paper path
(between the SB paper guides shown in the illustration below) toward the DX paper tray #1.
Next, the machine feeds the switchbacked paper (SB paper) and prints on its bottom face. After
completion of printing on the bottom face, the machine ejects the duplex-printed paper.
The duplex print mechanism consists of the DX flapper drive mechanism and the SB roller
drive mechanism.
The DX flapper drive mechanism is driven by the ASF motor. The rotational torque is
transmitted via the gear trains (in the link gear holder DX ASSY and link gear holder LT DX
ASSY) to the DX cam whose inner profile drives the DX flapper (horizontal
positions) via the DX flapper drive lever. (For details, refer to the next page.)
The SB roller drive mechanism is driven by the paper feed motor whose rotational torque is
transmitted via the gear trains (including the paper ejection roller gear and paper ejection roller
SB gear) to the SB roller. The torque transmission route can be engaged/disengaged by the SB
clutch lever that is driven by the outer profile of the DX cam (which is also used in the DX
flapper drive mechanism). (For details, refer to
The duplex unit has the switchback paper detection sensor, DX cover sensor, and DX cam
switch. For details about the sensors and switches, refer to
Paper feed roller
Registration sensor
actuator
Link gear holder
DX ASSY
(Rear)
Outer back
cover
Bank
Section 3.2.2.4, the paper pulling-in, registration, feeding and ejecting
Head/carriage unit
Platen
Paper ejection roller
SB paper guides
Paper pull-in rollers
Link gear holder LT DX ASSY
Flap of DX paper tray #1
page 3-48.)
Section
Star wheels on the DX flapper
SB roller
Duplex unit
DX cam switch
3-46
backward-tilted
3.2.3.
Paper path for switchback paper
(Front)
DX flapper
Switchback paper detection
sensor actuator
(3_Duplex_1)
Confidential