Epson Stylus COLOR 440 Service Manual page 55

EPSON Stylus COLOR 440, 640, and 740
Although economy of design results from the pump mechanism and the
paper feed mechanism sharing the same motor, it is not desirable for
the pump to be running every time the printer feeds paper. To
overcome this problem, the operations of paper feeding and pumping
are kept separate by the PF motor's direction of rotation. Since the
printer feeds paper in one direction only, the other direction is reserved
for running the pump.
Here's how that works: Slots in the pump's drive wheel permit two
rollers to move radially inward or outward, depending on the wheel's
direction of rotation. As shown in Figure 2-13, when the pump turns
counterclockwise (as viewed from the left side of the printer), the rollers
are forced outward to compress against the ink drain tube. This is
caused by the angle of the slots and friction between the rollers and the
drain tube. In this position, pumping takes place. When the pump
turns clockwise (the direction of paper feeding), the rollers relax and
move inward, and no pumping occurs.
Figure 2-13. Pump Rotation
The table below summarizes the relationship between the PF motor's
direction of rotation and the pump mechanism's operation.
Table 2-7.
PF Motor and Pump Mechanism Functions
PF Motor Rotation
Clockwise (CW)
Counterclockwise (CCW)
For the pump to drain ink away from the cartridge, not only must the
pump be running, but the printhead must be firmly seated on the
printhead capping mechanism with the air bleed valve closed. The
following section explains the operation of the capping mechanism.
Chapter 2 Operating Principles
Pump Mechanism Functions
Pump operates
Head cleaner extends
Carriage lock extends
Pump does not operate
Head cleaner retracts
Carriage lock retracts
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