Recording Paper Feeding/Ejecting Control In Duplex Printing; Top-Face Printing; Bottom-Face Printing - Brother DCP6690CW Service Manual

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.
Paper width sensor
(Media sensor)
Paper feed roller
Registration sensor
Link gear holder
DX ASSY
Paper pull-in rollers

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.
Paper width sensor
(Media sensor)
Paper feed roller
Registration sensor
Link gear holder
DX ASSY
Paper pull-in rollers
Head/carriage unit
Switchback paper
detection sensor
DX cam switch
DX cover sensor
Head/carriage unit
Switchback paper
detection sensor
DX cam switch
DX cover sensor
3-49
DX flapper
SB roller
Recording
paper path
DX paper tray #1
(Sequence_1)
DX flapper
SB roller
Recording
paper path
DX paper tray #1
(Sequence_2)
Confidential