General Printer Mechanism Operation; Printhead Mechamism - Epson DFX-8000 Service Manual

2.1 General Printer Mechanism Operation

This chapter will describe the functions and operating principles of printer mechanism ModeJ-3C65.
2.1.1 Printhead Mechanism
The printhead mechanism is composed of a printhead, ink ribbon, and ribbon mask. The printhead is
a spring-charge impact dot printhead.
a. Portion A of the dot wire is attached to the actuating spring plate, and is pulled back (RIGHT in the
figure) by magnetic force (M) when the printer power is off and when the printer is in the standby
state. Therefore, the actuating spring plate is bent backward by the M force.
When the magnetic coil is energized, a countermagnetic force (C) is induced in the core, the total
magnetic force on the actuating spring plate becomes zero, and the actuating plate returns to its
original shape. At this time, the dot wire is pushed forward and strikes the platen via the ink ribbon
and paper, which prints a dot on the paper.
c. When the coil is deenergized, the dot wire returns to the state described in "a".
The above described operation is performed for each dot wire. Each dot wire has its own drive circuit
which independently controls energizing of the coil.
The 18 dot wires are arranged as two vertical rows of 9 pins. Therefore, twice the speed of a normal
9-pin printer can be obtained by driving the two 9-pin rows. (Both 9-pin rows may be driven at the same
time depending on the character construction or printing mode).
In the copy mode, the characters printed by the first row are printed again by the second row
Figure 2-1 shows the operating principle of the printhead.
Paper
/
I
Platen
Figure 2-1. Printhead Operating Principle
Ribbon
2-1
(c) + -/-