Printronix P9212 - Hammer Bank and Character Generation

2–5
Principles of Operation
The Hammer Bank
The P9212 uses a hammer bank to print dots. The hammer bank consists of
88 hammer springs mounted on a shuttle that moves horizontally a short
distance back and forth. The hammer bank prints one horizontal line of dots
during each horizontal sweep of the shuttle.
A hammer spring is a stiff leaf spring with a hardened steel tip at the upper
end, and is attached to the hammer bank at the lower end. (See Figure 2–4.)
A permanent magnet keeps the hammer springs retracted and under tension.
Behind every hammer is a pair of magnetic coils which, when energized,
neutralize the field of the permanent magnet. This releases the hammer,
which springs forward and strikes the ribbon and paper, leaving a dot. The
hammer is recaptured by the permanent magnet as it rebounds. (See
Figure 2–5.)
Magnet
Paper Ironer
Platen
Paper
Ribbon Mask
Hammer Bank Cover
Hammer Tip
Hammer Spring
Ribbon
Coil
Coil
Shuttle Shaft
Hammer Spring Mounting Screw
Figure 2–4. Hammer Spring and Shuttle Arrangement