Browse Prior Art Database

Energy Control for a Resistive Ribbon Printer

IP.com Disclosure Number: IPCOM000062539D
Original Publication Date: 1986-Dec-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 3 page(s) / 27K

Publishing Venue

IBM

Related People

Shipp, RA: AUTHOR [+2]

Abstract

Excessive heating of a printhead of a resistive ribbon printer due to printing graphics is prevented by reducing power to the printhead through sampling the electrode power at selected intervals. A plurality of consecutive samples is taken to determine how much, if any, the electrode power should be reduced. Excessive heating of a printhead of a resistive ribbon printer occurs when printing dense characters (at least 50% of each character box) for an extended period of time (at least 20 character boxes). With this excessive printhead heating, continued printing will result in increased printhead wear and damage, and ribbon damage, as well as degradation to subsequent printed characters.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 53% of the total text.

Page 1 of 3

Energy Control for a Resistive Ribbon Printer

Excessive heating of a printhead of a resistive ribbon printer due to printing graphics is prevented by reducing power to the printhead through sampling the electrode power at selected intervals.

A plurality of consecutive samples is taken to determine how much, if any, the electrode power should be reduced. Excessive heating of a printhead of a resistive ribbon printer occurs when printing dense characters (at least 50% of each character box) for an extended period of time (at least 20 character boxes). With this excessive printhead heating, continued printing will result in increased printhead wear and damage, and ribbon damage, as well as degradation to subsequent printed characters. Power to the electrodes of the printhead is reduced by convolving samples of electrode power estimates with a transfer function designed to model heating of the printhead. An analog circuit monitors electrode current over time.

The circuit includes a 270-milliohm resistor 1 placed in series with the ground return path of the electrodes of the printhead. The resistor 1 necessarily carries current from all electrodes driven.

Thus, the voltage across the resistor 1 increases linearly in accordance with the number of printhead electrodes energized, as each electrode carries approximately the same current. The voltage drop across the resistor 1 is amplified in an amplifier 2. A low-pass filter 3 passes only low frequencies of the amplified voltage from the amplifier 2. The output of the low-pass filter 3 is a voltage (VLP) that is supplied to a comparator 4. The other input to the comparator 4 is a reference voltage (VREF). VREF is selected to form a threshold level for typical alphanumeric printing (not graphics); this averages about five electrodes per column in which there are forty electrodes in the column. The analog circuit is utilized to produce an output in accordance with the following: OP(t) = Compare(VREF, h1p * (i(E) x R x A )) where * is a convolution operator

h1p is low-pass filter transmission function

i(E) is electrode current sum

R is resistance of resistor 1

A is amplification factor of amplifier 2

OP(t) is microprocessor input, e {0, 1}. Thus, when VLP exceeds...