Mechanical Operation - Printhead Mechanism - OKIDATA Pacemark 3410 Service Manual

2.2 MECHANICAL OPERATION
2.2.01 Printhead Mechanism
The printer uses a highly efficient stored energy type printhead. Power is not consumed until the printwires
are activated, thereby extending the printhead life to approximately 200 million characters.
The printhead uses 9 printwires in two columns. Each wire is welded to an armature. Behind this armature
is a spacer ring.
Each of the 9 printwire armatures has a permanent magnet behind it. The magnets attract the armatures,
pulling the printwires into the wire guide, thus keeping the wires inside the printhead. A coil is wrapped
around each of the permanent magnets.
When a dot is to be printed, current is passed through the appropriate coil. This creates an
electromagnetic field which counters the magnetic field of the permanent magnet. The armature can then
spring forward and the print wire (which is attached to the armature) strikes the ribbon and imprints a dot
on the paper.
When current is removed from the coil, the magnetic field of the permanent magnet attracts the armature,
causing the printwire to retract into the wire guide once again.
The printhead consists of the parts listed below.
Wire Guide
Print Wires
Armature Assembly
Spacer
Permanent Magnet Assembly
Thermistor: used to monitor the printhead temperature
Printed Circuit board with Coils
Head Gap Adjusting
The head gap adjusting mechanism modifies the gap between the platen and printhead. This is
accomplished by moving the adjusting lever on the right side of the printer mechanism. When the lever is
moved, the carriage shaft rotates. Since the carriage shaft is attached to the printer mechanism through
eccentric collars, turning the carriage shaft, changes the distance between the platen and the printhead.
Service Guide PM3410
Chapter 2 Principles of Operation
Page: 24