Pitney Bowes DM300c Service Manual page 57

3.5 Ink System
DM300c/DM400c/DM475 Service Manual (SV61801 Rev. D)
Purge Unit (cont'd)
Wiper. The wiper removes excess ink and debris from the print head
as the carriage assembly moves to the print position. A wiper cleaner
attached to the back of the print head carriage is designed to keep the
wiper free of excess ink and contaminants.
Print Head Lock. The print head lock is cam driven up to the locking
position as the print head carriage reaches the home. The lock keeps
the carriage in the home position, assuring the print head is capped and
preventing movement during shipping.
Carriage Home Sensor. The sensor is activated by a tab (sensor flag)
mounted on the bottom of the carriage assembly. It tells the system logic
when the carriage is (and is not) in the home position. The home posi-
tion is defined as that point when the home position sensor is blocked,
the print head is capped and the print head lock is up, engaging the
print carriage and preventing its movement.
After printing is complete and no more envelopes are inserted, the system
logic tells the carriage motor to move the print head back to the capped
position, to prevent the ink nozzles from drying out. This also occurs if PS1
has not detected a lead edge for a period of 15 seconds. As the carriage
moves to the home position, the purge motor turns counterclockwise and
drives the cap up against the print head. Almost simultaneously, the print
head lock rises to lock the carriage in the home position. These actions are
triggered by the carriage home sensor located on the purge unit.
When printing is called for, the purge motor turns counterclockwise and
drives both the print head cap and lock down and the wiper up and the car-
riage is driven to the print position. When purging is called for, the purge
motor turns clockwise and drives only the cam that powers the purge suc-
tion pump.
Purging. This process consists of one or more of the following actions:
pump suction (aspiration); wiping; and spits (firing of nozzles). Purges
are performed:
• At power up;
• When the ink cartridge is replaced;
• When the print head is replaced;
• Following a jam or shut down;
• Before, during and after printing.
The purge cycles are listed on the next page.
The purge unit is connected to the main logic board at J120 (yellow) and
J116 (purple).
3 • Theory Of Operation
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