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This technique is useful for operating a voice coil hammer of the type used in bar and helix printers where high repetition rates are desired.
English (United States)
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Technique For Operating a Moving Coil Print Hammer
This technique is useful for operating a voice coil hammer of the type used in
bar and helix printers where high repetition rates are desired.
The initial stroke (at the beginning of printing, for example) of the print
hammer is initiated by a current pulse 10 of longer duration followed by several
pulses 11 of shorter duration where impact is to occur repeatedly. The current
pulse 10 would be applied in advance to compensate for the increased stroke
and flight due to the hammer being at rest position. The pulses 11 are applied
when the hammer is hovering between rest and impact position and can
therefore respond quickly.
When a given number of dots are skipped, the hammer might return to rest
position or various positions between. To avoid the consequential variations in
flight time which are a result of the different hammer strokes, pulses 12 of the
shortest duration are applied, thereby preventing the hammer from returning to
stop. Pulses 12 are long enough to cancel return velocity and small enough to
This technique allows a relatively wide separation, e.g., 0.016 inch, between
paper and hammer to permit an unrestricted paper advance while the hammer is
at rest position, while providing high hammer repetition rate for increased print
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