2.2.03 Head Gap Mechanism
The head gap is automatically set for the thickness of the medium loaded in the printer. In the
case of envelopes, where the medium thickness varies as the printhead moves along the platen,
the strike force of the pins changes to compensate for the differences in thickness.
Head Gap Setting Operation
Once printing starts, the space motor rotates the ribbon gear, causing idle gear C to turn
the change gear.
When the MPU requests a change in the head gap setting, the GAP-P signal causes the
armature (which is holding the change gear) to be attracted to the pranger magnet. The
gap reset spring can now push the change gear so it contacts the gap change gear.
The rotation of the gap change gear causes idle gear D to turn the adjust gear. The adjust
gear turns the adjusting screw, resulting in a new head gap setting.
NOTE:
As the adjusting screw turns counter-clockwise, the gap narrows.
As the adjusting screw turns clockwise, the gap widens.
2-2-03a.tif
Principles of Operation 2 - 26 Microline 520/521 Service Handbook
P/N 59257803
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