Jerry Wayne Hedstrom

US Patent:

41463382, Mar 27, 1979

Filed:

Mar 30, 1977

Appl. No.:

5/782793

Inventors:

Jerry W. Hedstrom - Plano TX

Assignee:

Xerox Corporation - Stamford CT

International Classification:

B41J 3536

US Classification:

400249

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.

US Patent:

41150139, Sep 19, 1978

Filed:

Mar 30, 1977

Appl. No.:

5/782794

Inventors:

Jerry W. Hedstrom - Plano TX

Assignee:

Xerox Corporation - Stamford CT

International Classification:

B41J 3536

US Classification:

400249

Abstract:

An end-of-ribbon sensor for use with an electronic typing system comprises a housing which protrudes from a mounting block and plate attached to the ribbon cartridge mounting plate. The housing protrudes through an aperture in the ribbon cartridge and within the interior volume thereof and contains a light source for directing a beam of light at a predetermined angle at the ribbon and a light detector directed at a predetermined angle for receiving the reflected light. Upon sensing a reflective marker attached to the ribbon, the output of the sensor provides an appropriate signal indicating the end-of-ribbon. The housing also comprises a portion of the mounting means for the ribbon cartridge.