Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1998-10-30
2001-06-19
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
Reexamination Certificate
active
06247775
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is related to inkjet printing devices. More particularly, the present invention is related to inkjet printing devices that make use of an optical technique for determining ink level in an ink container.
Inkjet printers frequently make use of an inkjet printhead mounted within a carriage that is moved back and forth across print media, such as paper. As the printhead is moved across the print media, a control system activates the printhead to deposit or eject ink droplets onto the print media to form images and text. Ink is provided to the printhead by a supply of ink that is either carried by the carriage or mounted to the printing system not to move with the carriage. For the case where the ink supply is not carried with the carriage, the ink supply can be in fluid communication with the printhead to replenish the printhead or the printhead can be intermittently connected with the ink supply by positioning the printhead proximate to the filling station whereupon the printhead is replenished with ink from the refilling station.
For the case where the ink supply is carried with the carriage, the ink supply may be integral with the printhead where upon the entire printhead and ink supply is replaced when ink is exhausted. Alternatively, the ink supply can be carried with the carriage and be separately replaceable from the printhead or drop ejection portion.
Regardless of where the supply of ink is located within the printing system it is critical that the printhead be prevented from operating when the supply of ink is exhausted. Operation of the printhead once the supply of ink is exhausted results in poor print quality, printhead reliability problems, and if operated for sufficiently long time without a supply of ink can cause catastrophic failure of the printhead. This catastrophic failure results in permanent damage to the printhead. Therefore, it is important that the printing system be capable of reliably identifying a condition where the ink supply is nearly exhausted or exhausted. This technique should be accurate, reliable, and relatively low cost thereby tending to reduce the cost of the printing system.
SUMMARY OF THE INVENTION
The present invention is an inkjet printing system for depositing ink on media. The inkjet printing system includes an ink containment vessel formed of a material having optical characteristics selected to block light in the visible light spectrum. Also included is an energy source for providing, energy having characteristics that are selected to allow energy passage through the ink containment vessel. Finally, an energy detector is included for detecting energy provided by the energy source that passes through the ink containment vessel. Energy from the energy source impinging upon ink is altered so that an energy detector output signal is indicative of ink within the ink containment vessel.
Another aspect of the present invention is an inkjet printing system that includes an ink containment vessel for containing ink. The ink containment vessel has characteristic properties that vary with ink level within the ink containment vessel. An energy source is included for providing energy having an energy characteristic related to the energy source. Energy provided by the energy source impinges on the ink containment vessel. Also provided is an energy detector for detecting energy provided by the energy source. The energy detector is configured to discriminate against ambient energy not having the energy characteristic. The energy detector provides an energy detector output signal indicative of ink level within the ink containment vessel.
In one preferred embodiment, the energy source is an optical light source and a modulator for providing temporal modulation of light energy provided by the optical light source. In this preferred embodiment the energy detector is a bandpass filter that is tuned to a frequency associated with the energy characteristic. Also included in the energy detector is an optical detector for detecting light energy passed by the bandpass filter.
REFERENCES:
patent: 5073720 (1991-12-01), Brown
patent: 5508521 (1996-04-01), Kraft et al.
patent: 5616929 (1997-04-01), Hara
patent: 5635961 (1997-06-01), Sato
patent: 5689290 (1997-11-01), Saito et al.
patent: 5997121 (1999-12-01), Altfather et al.
patent: 6012795 (2000-01-01), Saito et al.
Barlow John
Hallacher Craig A.
Hewlett--Packard Company
Sullivan Kevin B.
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