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Power-Limiting Electrode Drive Circuit

IP.com Disclosure Number: IPCOM000042658D
Original Publication Date: 1984-Jun-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 2 page(s) / 23K

Publishing Venue

IBM

Related People

Horlander, FJ: AUTHOR

Abstract

In resistive ribbon printing such as described in U.S. Patents 4,350,449 and 4,345,845, a threshold level of voltage at the printhead electrodes is desirable to initiate printing current. The drawing shows resistor 1 connected between the power source 3 and each electrode 5, which is effective to reduce the potential at the electrode 5 after current is initiated. Undesirable power excursions at the electrode 5 to ribbon 7 interface are eliminated. Typically, power source 3 is a constant-current source, as shown in the drawing, and the printhead contains forty electrodes 5 in a vertical column.

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Power-Limiting Electrode Drive Circuit

In resistive ribbon printing such as described in U.S. Patents 4,350,449 and 4,345,845, a threshold level of voltage at the printhead electrodes is desirable to initiate printing current. The drawing shows resistor 1 connected between the power source 3 and each electrode 5, which is effective to reduce the potential at the electrode 5 after current is initiated. Undesirable power excursions at the electrode 5 to ribbon 7 interface are eliminated. Typically, power source 3 is a constant-current source, as shown in the drawing, and the printhead contains forty electrodes 5 in a vertical column. The resistive ribbon 7 in basic form has a resistive lamination which contacts electrodes 5; an internal, highly conductive layer to serve as a current return path; and an ink lamination on the outside which is rendered flowable by heat generated by current flow from electrodes 5. Generation of heat within the ribbon 7 is desirable, while generation of heat at the electrode-ribbon interface is less effective for printing and tends to damage or deform the ribbon 7. Prior to current flow, voltage Vd at the output of current source 3 appears entirely across the electrode 5 to ribbon 7 interface. During current flow, this voltage is reduced by the voltage drop defined by the current multiplied by the resistance of resistor 1. The higher voltage at turn-on produces a transient which is desirable for effective and reliable current initiation...