Hammer And Shuttle Arrangement - Printronix p300 Maintenance Manual

2–5. Print State
–continued
j. Print Mechanism (Figure 2–18 through Figure 2–22)
The print mechanism prints a full line of characters by using a shuttle that moves horizontally back and
forth. Printing is accomplished using individual print hammers. These hammers may print during both
directions of the shuttle sweep. Print hammers are grouped into pairs. Each pair consists of an odd num-
bered hammer and an adjacent even numbered hammer. All hammers are fixed to the shuttle.
Each hammer consists of a stiff leaf spring attached at one end to the hammer bank with a screw. Its other
end has a rod shaped tip. A single permanent magnet, running the full length of the hammer bank, keeps the
hammer springs retracted, that is, under tension.
Each print hammer is associated with a normally de–energized coil mounted on a magnetized pole pin.
The end of the pole pin directly contacts the free end of the hammer spring. Printing is done by releasing
hammers as the shuttle moves across a row. The initial row of print is always left to right. When the stroke
is completed, the direction of motion reverses, as defined by the cam profile. To accommodate this direc-
tion change, the data associated with that row is scanned normally but presented to the hammer drivers in
reversed order of occurrence. When hammer driver logic determines that the hammer is to print a dot, a
current pulse energizes the coil. The polarity of the resulting electromagnetic field opposes the field of the
permanent magnet, releasing the hammer. The hammer tip strikes the ribbon and paper, leaving a dot of
ink.
–A– –B–
P300 P600
Figure 2–18. Hammer and Shuttle Arrangement
P300/P600 Principles of Operation 2–29