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Phaser 8400/8500/8550/8560 Color Printer Service Manual 2-11
Theory of Operation
In the print position (0 degrees), the Printhead is forward and rests against the
right and left head-to-drum buttons. The head-to-drum buttons define the
space between the jet stack and the drum. When the Process Drive is
activated, it drives the Drum Maintenance Camshaft to engage the tilt gear
train. The tilt cam tilts the Printhead into the print position. The cam is
combined with a missing tooth gear that allows the cam to be inactive in the
print position, freeing the Process Drive to perform other printer operations.
The cam has a latching mechanism to unlatch and latch the missing tooth
gear to engage the Printhead tilt drive train. The cam’s latching mechanism
also holds the tilt gear in place. A leaf spring applies constant pressure to
engage the gear when the latching mechanism is released. The arm of the
latching mechanism is inside the frame; the rest is visible, outside the frame.
Arrows located on the latching mechanism and on the frame indicate when
the Printhead is in print position. When the arrows on the latching mechanism
and frame align, the Printhead is in the print position and the tilt gear
disengages from the Process Drive. Phaser 8500/8550/8560 printers have a
solenoid (Head Tilt Solenoid) that is actuated and deactuated when the tilt
cam gear rotates to the respective engaged and disengaged positions.
The latching mechanism is actuated by a small movement of the wiper
coupled with the Head Tilt Solenoid. The action of the solenoid ensures that
the Head Tilt Gear engages the tilt drive gear. Through a follower gear, the
compound gear drives the tilt cam gear clockwise. A cam follower, mounted
on the lower end of the tilt arm, follows the rotating tilt cam gear and tilts the
Printhead. After one revolution of the tilt gear, the latching mechanism is
pulled back into position by the return spring in the 8400, and by the Head Tilt
Solenoid in the 8500/8550/8560.
Drum
Printhead
Tilt Gear
Tilt Gear (Engaged)
Printhead Restraint
s8500-015
DM Cam Gear