End-of-ribbon sensor circuitry

Details End-of-ribbon sensor circuitry End-of-ribbon sensor circuitry

1977-03-30

1979-03-27

Wright, Jr., Ernest T.

Typewriting machines

Including interposed inking device for record-medium

Means auxiliary to ribbon mechanism

400208, B41J 3536

Patent

active

041463382

ABSTRACT:
End-of-ribbon sensor circuitry for use with an end-of-ribbon sensor of an electronic typing system comprises an input voltage divider for receiving the output signal of the end-of-ribbon sensor. The two signals from the voltage divider are applied to a differentiating circuit providing different time constants to the two signals. The differentiating circuit compensates for varying conditions of ambient light within the ribbon cartridge and provides a delay which eliminates false signals due to rapid fluctuations of the ribbon. After differentiation, the two signals are compared utilizing delayed switching time to determine the presence of an end-of-ribbon signal. The output, if any, of the comparator is applied to a sampling circuit where the signal is sampled for a predetermined period of time after the print hammer is fired. If an end-of-ribbon signal is present, said signal is clocked into a latching circuit from which it is sent to the printer control system which stops the printer when the present line of print is completed.

REFERENCES:
patent: 3730449 (1973-05-01), Satas et al.
patent: 4000804 (1977-01-01), Zaltieri

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