Brother MFC620CN Service Manual page 118

Switching arm assembly inside maintenance unit
When the paper feed motor is driving the maintenance unit, counterclockwise (when viewed from
the output gear side) rotation drives the purge cam; clockwise rotation, the tube pump.
Purge bevel gear
Tube pump
Switching arm assembly
Purge cam mechanism
The purge cam is so designed that:
- the carriage lock pops out to lock the head/carriage unit before purging and pops in before
cleaning with the head wiper (this lock also secures the head/carriage unit during transportation),
- the pump switching unit switches application of the negative pressure from the pump between
the black head nozzles, the color head nozzles, and the air vent rod unit. When the purge cam is
in the head capping position, the pump switching unit opens their interiors to normal atmospheric
pressure.
- the head wiper comes out to clean the nozzle surface, and
- the air vent rods are pushed up via the slide cams to expel air trapped.
The purge cam switch detects the cam drive positions. (See
Main drain tube
Air vent tube
Color drain tube
Opening tube to the atmospheric air
Section
3-30
Purge cam
Pump switching unit
Purge HP switch
Black drain tube
3.2.3.)
Confidential