Brother DCP-6690CW, Service Manual, Page: 103 / 506

3-49 Confidential
Recording paper feeding/ejecting control in duplex printing
In duplex printing, the machine feeds and ejects the recording paper by driving the paper pull-in
rollers, paper feed roller, and SB roller. In the descriptions below, the rotational directions of
those rollers are as viewed from the left side of the machine.
„
Top-face printing
The paper pull-in rollers and the paper feed roller are concurrently driven to feed the recording
paper. After completion of top-face printing, the machine ejects the recording paper
temporarily. As shown below, during ejection, the DX flapper is in the horizontal position.
After ejection, the DX flapper slightly tilts backwards to hold the trailing edge of the paper.
„
Bottom-face printing
As shown below, the machine further tilts the DX flapper backwards and rotates the SB roller in
the
backward direction (counterclockwise) to switch back the paper through the switchback
paper path toward the DX paper tray #1.
Then, the machine feeds the switchbacked paper (SB paper) by driving not only the paper pull-
in rollers (clockwise) but also the SB roller (counterclockwise) concurrently. The concurrent
drive surely brings the SB paper to the paper pull-in rollers, preventing the paper pull-in rollers
from feeding a new sheet of the recording paper loaded in the paper tray instead of the SB
paper.
(Sequence_1)
Paper width sensor
(Media sensor)
Paper feed roller
Registration sensor
Head/carriage unit
SB roller
Recording
paper path
Paper pull-in rollers
DX paper tray #1
DX flapper Switchback paper
detection sensor
DX cam switch
DX cover sensor
Link gear holder
DX ASSY
(Sequence_2)
Paper width sensor
(Media sensor)
Paper feed roller
Registration sensor
Head/carriage unit
SB roller
Recording
paper path
Paper pull-in rollers
DX paper tray #1
DX flapper Switchback paper
detection sensor
DX cam switch
DX cover sensor
Link gear holder
DX ASSY