Epson STYLUS 4001968 Service Manual page 34

Operating Principles
PF Motor Rotational Direction
CW (forward rotation)
(backward rotation)
The pump draws ink from the printhead nozzles and drains it into the waste ink drain tank. The
printer performs this operation to eliminate dust or bubbles within the nozzles. Figure 2-9
illustrates the pump operation. When the paper feed drive motor rotates CW (forward), the pulley
pumps in the wheel pump unit rotate in the direction of the arrow while squeezing the ink tube to
push the ink inside the tube out to the waste ink drain tank. On the other hand, when the motor
rotates CCW, the pulley pumps move inward along the grooves of the wheel pump so that pressure
applied to the ink tube is released.
Wheel Pump
Pumping (CW)
Table 2-4. Pump Mechanism Operation
Pumping (Pump motor:
No pumping (Pump motor: CCW)
/
Pulley Pump
Figure 2-9. Pump Operation
STYLUS 800 Service Manual
Operation
Pumping
Pseudo-pumping (False absorbing)
Gear backrush com~ensation
Pump pulley reset
Gear backrush compensation
No pumping (CCW)
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