Christopher A Shultz

US Patent:

56821832, Oct 28, 1997

Filed:

Oct 31, 1994

Appl. No.:

8/332544

Inventors:

John M. Wade - Poway CA
Christopher J. Shultz - San Diego CA
Betsy C. Huntingdon - West Lafayette IN

Assignee:

Hewlett-Packard Company - Palo Alto CA

International Classification:

B41J 2195
B41J 29373

US Classification:

347 7

Abstract:

Disclosed is a method of determining imminent ink exhaustion in a thermal inkjet print cartridge based on the discovery that ink drop volume falls at a faster rate at high frequency firing rates than at low frequency firing rates as ink supply diminishes. The method includes warming the print cartridge printhead and ink to a predetermined temperature; then operating the print cartridge printhead at a first firing frequency to eject a volume of ink, said operating step including heating the ink and printhead, carrying away heat in the ejected volume of ink, and conveying a volume of cooler ink to the printhead to replace the ejected volume; and monitoring a first temperature change from the predetermined temperature. Then warming the same print cartridge printhead and ink to a predetermined temperature; operating the print cartridge printhead at a second firing frequency which is different than the first firing frequency to eject a volume of ink, said operating step including heating the ink and printhead, carrying away heat in the ejected volume of ink, and conveying a volume of cooler ink to the printhead to replace the ejected volume; and monitoring a second temperature change from the predetermined temperature. The first and second temperature changes are compared to indicate a low ink supply.

US Patent:

57482160, May 5, 1998

Filed:

Mar 14, 1996

Appl. No.:

8/616829

Inventors:

Joseph E. Scheffelin - San Diego CA
David S. Hunt - San Diego CA
Mark E. Young - Escondido CA
Elizabeth Zapata - San Diego CA
Alfred Zepeda - San Marcos CA
Christopher J. Shultz - San Diego CA
Jon Fong - Manhattan Beach CA

Assignee:

Hewlett-Packard Company - Palo Alto CA

International Classification:

B41J 2175

US Classification:

347 87

Abstract:

A print cartridge is described which has an ink recharge port and valve structure to enable the print cartridge reservoir to be recharged with ink. A slideable, generally cylindrical ink valve extends through the print cartridge body and into the ink bag. The valve has a male connector portion at its end external to the print cartridge body. The valve is open when pushed into the print cartridge body and closed when pulled away from the print cartridge body. An ink refill system containing a supply of ink has a slideable valve with a female connector portion which is engageable with the male connector portion of the print cartridge valve. To recharge the print cartridge ink reservoir, the end of the print cartridge valve is inserted into the end of the ink refill system valve to create both a mechanical coupling and a fluid tight coupling between the two valves. A further force pushing the print cartridge against the ink refill system causes both valves to be pushed inside their respective ink reservoirs. This further insertion causes both valves to become open, thus creating an airtight fluid path between the ink refill system reservoir and the depleted print cartridge reservoir.