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Print Hammer Flight Time Compensation for Supply Voltage Variation

IP.com Disclosure Number: IPCOM000122595D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 5 page(s) / 189K

Publishing Venue

IBM

Related People

Ross, CO: AUTHOR

Abstract

Techniques have been devised to minimize mis-registration of the characters in a high-speed line printer, thus improving print quality. The task is made more difficult when the printer has a wide range of impact energy requirements due to forms thickness and ribbon life expectancy. The large, variable pulse loading on the print magnet power supply and its nominal value within a tolerance range cause static and dynamic errors in the location of characters on the printer page. These are even larger when a wide range of hammer energies is used as the control over print density for forms thickness and ribbon ink level. Additionally, the sensitivity of registration to these factors is around 2.

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Print Hammer Flight Time Compensation for Supply Voltage Variation

      Techniques have been devised to minimize mis-registration
of the characters in a high-speed line printer, thus improving print
quality.  The task is made more difficult when the printer has a wide
range of impact energy requirements due to forms thickness and ribbon
life expectancy.  The large, variable pulse loading on the print
magnet power supply and its nominal value within a tolerance range
cause static and dynamic errors in the location of characters on the
printer page.  These are even larger when a wide range of hammer
energies is used as the control over print density for forms
thickness and ribbon ink level. Additionally, the sensitivity of
registration to these factors is around 2.5 times greater at very
high energies than at the very low ones so the control system gain
must be programmable as well as have a known and non-linear gain over
the entire range of supply voltages in the machines.

      The circuit described here accepts and remembers print density
information sent from the controlling microprocessor.  The problem is
two-dimensional because the value of time compensation required is
the result of two independent variables.  They are the print density
setting now in effect and the value of the power supply at the moment
a particular hammer fires.  Compared to prior art, this circuit has
the advantages of higher accuracy, lower cost and greater reliability
with a general approach that will function over a wider range of
today's sophisticated high-speed impact printer control system.

      It is given that, when the forms and density are chosen by the
operator, the microprocessor offsets the nominal values of flight
time for print density and the circuit's insertion delay for that
density at the power supply voltage in a particular machine.  This
data was saved when the flight timing feature of the machine was last
used.

      The circuit design is based on a two-dimensional array of
engineering data that contains absolute hammer flight times for the
range of supply voltages and print densities for all machines.
Mathematical manipulation is used to remove the large static values
of flight time; this is done because that portion is covered by the
above-mentioned flight time system in the machines.  In essence,
differentiation is done so the resulting data set shows both (+) and
(-) values of time delay are needed for compensation.  Since only
positive domain values can be produced, the origin is simply shifted
left so the most negative data yields the minimum insertion delay
produced by the circuit.

      This differentiated data is plotted in Fig. 2 which shows the
functional requirements of the described circuit. PD refers to the
Print Density level chosen by the operator. The voltage varies
dynamically over no more than 25% of its total design range during
each worst-case print and linefeed cycle, regardless of the no...