Brother MFC990CW Service Manual page 104

(4) Air removing mechanism
Other two positions of the purge cam shift two slide cams--one for black ink, the other for color
inks, producing vertical motion of a single air vent rod for black ink and three air vent rods for
color ink, respectively.
Pushing up the air vent rods opens the shut-off valves inside the air vent unit of the head/
carriage unit. Simultaneously adding negative pressure from the tube pump removes air trapped
in the damper assemblies.
Purge gear
(Cap lift cam gear)
(ASF changeover gear)
Slide cam for black ink
Slide cam for color ink
Damper ASSY (Magenta)
Air bubbles
Left chamber
Damper ASSY (Cyan)
Air bubbles
Left chamber
Damper ASSY (Yellow)
Air bubbles
Left chamber
Damper ASSY (Black)
Air bubbles
Left chamber
Maintenance unit
Purge cam
Right
chamber
Right chamber
Right
chamber
(Air vent rods)
Right
chamber
3-27
Air vent rod for black ink
Air vent rods for color ink
Air vent cap
Shut-off valves
Air vent unit
(Air vent cap)
(A part of maintenance unit)
(3_16)
(BackEnd_E)
Confidential