Oki IP-6620 Maintenance Manual page 532

(5) Capping unit
- Structure
The capping unit is located on the right side of the printer. It comprises suction pump motors,
a capping unit up/down motor, three air release solenoids, and a capping unit sensor. The
suction pump motors drive the suction pumps. The capping unit up/down motor moves the
capping unit up and down.
- Function
When the carriage is at its home position, the capping unit interlocks with the pump motor to
perform capping and suck the ink. The capping unit also protects the print head surface by
capping in the carriage home position. A porous sheet is attached inside the cap rubber and
prevents ink from bubbling inside the cap when ink is sucked so that the ink inside the cap is
sucked completely during suction.
- Ink pump
The ink pump employs a rotary tube pump mechanism in which the tube is squeezed by
rotation. The ink pump squeezes the tube and sucks the ink by rotating the cam roller via the
pump motor that also operates the pump.
The pump tube is continuously squeezed by the cam roller and there is no back run of the ink.
Through the activation or deactivation of the air release solenoids (see below), from one to
six or seven colors can be sucked at the same time. The waste ink that was sucked in the
pump block is ejected into the waste ink bottle.
- Air release solenoid
This DC type air release solenoid is activated or deactivated to open or close the opening of
the tube with a rubber cap equipped at its extremity. A spring near the rubber cap apply a
strong pressure to close hermetically the tube opening. Three DC solenoids are equipped
and controlled independently. When ink is sucked and the pressure is controlled, the cap
rubber is filled with ink. When the ink removed (sucked) a meniscus is formed inside the
head nozzles. Conversely, if this operation is not performed, the meniscus is destroyed when
the cap filled with ink is opened. The air release solenoid is activated to suck together the ink
and air inside the cap in order to remove the ink inside cap and form the meniscus.
OKI Data Infotech Corporation CONFIDENTIAL
Chapter 8 Operation Mechanism
8-11