Brother DCP-6690CW, Service Manual, Page: 75 / 506

3-21 Confidential
Ink cartridge components and their main roles
- Disc valve S
A plastic needle in the refill base opens this valve to supply air to the ink cartridge. Removing
the ink cartridge closes this valve to prevent leakage due to ink backflow.
- Disc valve D
A plastic needle in the refill base opens this valve to allow ink to flow out of the ink cartridge.
Removing the ink cartridge closes this valve to prevent leakage.
- Sensor actuator
This actuator indicates the amount of ink remaining. Certain positions cut the light beam to
the ink empty sensor on the ink empty sensor PCB inside the ink refill assembly.
Ink backflow prevention in unsealing a new ink cartridge
An ink cartridge is vacuum-processed and vacuum-packed in a plastic bag at the factory. Even
if unpacked, the cartridge is kept in vacuum. Opening the disc valve S (air intake port) causes
the pressure in the cartridge to become equal to the atmospheric pressure.
Inserting a conventional cartridge swiftly may open not only the disc valve S but also the disc
valve D (ink supply port) at almost the same timing, causing backflow of ink from the ink
supply port. The backflow of ink could temporarily affect the performance of the ink jet
mechanism, so conventional machines automatically perform a purge operation after
replacement of an ink cartridge.
To prevent the backflow of ink, a new ink cartridge has a protective cap as shown below.
Turning the knob of the protective cap clockwise opens the air intake port, making the pressure
in the ink cartridge equal to the atmospheric pressure before insertion of the cartridge into the
machine and preventing backflow of ink. This backflow prevention eliminates purge operations
required.
Note: This machine does not perform a purge operation automatically. If the user forcedly
removes the protective cap without turning its knob, backflow of ink could occur, affecting the
print quality after the replacement of an ink cartridge.
Ink near-empty/Ink empty
Sensor actuator
Ink empty sensor
Filled with ink
(InkEmptySensor_E)
Turn the knob of the protective cap
clockwise to unseal the air intake port.
Ink cartridge
Protective cap
(ProtectiveCap)