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REV.-A
2.4.3.4 Pump Construction
Two check valves are installed in the pump. As the piston moves up and down, the bellows pressure
changes, causing one or the other of the valves to open, so that ink is either sucked in or blown out.
Specifically, when the piston is moving downwards, the bellows pressure is negative, which causes
the inlet check valve to open (and the outlet check valve to close); ink is thereby drawn into the pump.
When the piston moves upwards, these conditions are reversed, and ink is discharged from the pump.
From the Head Cap
==::::::
Inlet
Check Valve ----
Bellows------
-//====
To the Ink Cartridge
Outlet
___-Check Valve
Piston Axis
Figure 2-78. Pump Construction
2.4.3.5 Capping Mechanism
The capping mechanism protects the head from drying and from bubbles. Negative pressure is
generated inside the cap as the pump is driven while the valve is closed. Ink can therefore flow, through
the cap, from the head to the pump. The clutch cam, which is driven by the pump motor by means of
the pump drive gear, is in direct contact with the cap support; therefore, cam movement generates a
reciprocating movement of the cap.
The travel of the cam is limited by the clutch spring; should the pump motor continue to rotate in a
single direction, the transmission of rotation will cease when the limit imposed by the spring is reached.
Therefore, cap opening and closing is determined only on the basis of the rotational direction.
•
:>
Clutch Cam
\
Clutch Spring \
/
I
,
I
I
I
I
I
I
,
/I~
' __ ... '
J
,_/
~ ~ ~ /
Pump Drive Gear
Head Cap
Cap Support
" Fulcrum
Figure 2-79. Cap Movement
2-65
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