Brother MFC620CN Service Manual page 120

(3) Head wiper
After the purge operation, the purge cam pushes up the head wiper, wiping off any ink remaining
on the head nozzle surface as the head/carriage unit moves from right to left.
Maintenance unit
Head wiper
Purge cam
(4) Switching pump
The pump switching unit switches the negative pressure from the pump between the black head
nozzles, the color head nozzles, and the air vent rod unit. Another position returns all these
components to normal atmospheric pressure.
When the purge cam is in head capping position, the carriage lock fits the head caps tightly over
the print head, and the pump switching unit is opened to the atmosphere.
The tube pump consists of a pump gear and tube roller. As the pump gear rotates, the tube roller on
its circumference squeezes the ink drain tubes looped around the pump gear, forcing their contents
toward the ink absorber box and creating negative pressure.
Waste ink tube
Pump gear
Tube pump
Tube roller
3-32 Confidential