TallyGenicom 6600 Series, Maintenance Manual

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Chapter 7
Shuttle Frame Assembly
Shuttle Drive Motor
The shuttle drive motor is built into the shuttle assembly casting and spins a
crankshaft, to which are attached the big ends of two connecting rods.
(Figure 56.) The small end of one connecting rod attaches to the hammer
bank; the small end of the other connecting rod attaches to a counterweight
frame surrounding the hammer bank. (The hammer bank and the
counterweight constitute the shuttle assembly.) The shuttle drive motor,
acting through the crankshaft and connecting rods, converts rotary motion to
linear and opposing motion of the hammer bank and counterweight, in an
arrangement similar to that of a horizontally-opposed gasoline engine.
Mechanically, this design achieves the same benefits as that type of engine:
perfect primary balance, low vibration, and durability.
Each hammer spring is a stiff leaf spring with a cylindrical tungsten carbide tip
attached to the free end. (Figure 57.) A powerful permanent magnet is
imbedded along the length of the hammer bank and acts on the hammer
springs through individual pole pieces. The pole pieces magnetically attract
and hold the free end of the hammer spring under tension. This is called the
retracted state.
Figure 57. Hammer Springs and Hammer Bank (Detail)
Two electromagnetic coils are mounted behind each hammer and wound
around each pole piece. The coils are normally de-energized. When hammer
driver logic determines that a hammer must print a dot, a current pulse
energizes the coils behind the hammer. The polarity of the resulting magnetic
field opposes the field of the permanent magnet, canceling the magnetic
attraction and releasing the hammer, which springs forward, striking the
ribbon and paper and leaving an impression of its tip (a “dot”) on the paper.
184106a
NOTE : 6615 hammer bank shown.
Hammer Bank Assembly:
Coils, Magnet, Pole Pieces,
Hammer Spring
Assemblies
Alignment Pin
Hammer Spring
Assembly
Tungsten
Carbide
Hammer Tip