Incremental printing of symbolic information – Ink jet – Medium and processing means
Reexamination Certificate
1999-08-25
2001-01-23
Hilten, John S. (Department: 2854)
Incremental printing of symbolic information
Ink jet
Medium and processing means
C347S084000, C347S088000, C347S005000
Reexamination Certificate
active
06176575
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to phase change ink inkjet printers, and more particularly to the extension of the life of a drum maintenance unit used to deliver a release agent to a phase change ink inkjet printer transfer drum.
In solid phase change ink inkjet printers, where the ink is solid at room temperatures but is heated for ejection as a liquid onto an intermediate transfer surface, a drum maintenance unit is used as described in U.S. Pat. No. 5,805,191, incorporated herein by reference, to deliver a release agent, such as a silicone oil and/or functionalized oils, onto the intermediate transfer surface in order to allow an acceptable release of an image upon transfer from the intermediate transfer surface to media, such as paper or transparency. A certain amount of release agent is consumed for each simplex print so that the drum maintenance unit has to be replaced periodically when the release agent is fully consumed.
Currently the lifetime of the drum maintenance unit is specified according to a predetermined average release agent usage per print based upon a maximum customer usage profile, i.e., a usage profile that fits most customers. For example if the number of simplex prints specified for a particular drum maintenance unit is 30,000, then for each print the number is decremented in a memory or counter located in the drum maintenance unit until the number of copies reaches a low limit. At the low limit a message is provided on a display of the printer indicating to a user that the drum maintenance unit is in imminent need for replacement and a new unit should be ordered. When a very low limit is reached, the message produces an output indicating the remaining number of prints before the drum maintenance unit is depleted and needs to be replaced.
When the drum maintenance unit is replaced based upon the predetermined number of copies, there usually is still some release agent remaining in the drum maintenance unit reservoir that could be used to extend the life of the unit and produce more prints. Therefore what is desired is a scheme for extending the life of the drum maintenance unit by predicting more accurately the release agent usage without changing the hardware configuration of the drum maintenance unit.
BRIEF SUMMARY OF THE INVENTION
Accordingly the present invention provides a scheme for extending the life of a drum maintenance unit without changing the unit configuration by more accurately predicting release agent usage. Since the amount of release agent consumed for each print is proportional to the amount of ink used for each print, an ink coverage percentage is determined for each print based upon the image information contained in an image data file. The ink coverage percentage reflects the percentage of available print area that is covered by ink, which varies from full coverage to no coverage. From the ink coverage percentage a release agent usage ratio is determined based upon a release agent usage versus ink coverage percentage function. The release agent usage ratios for each print are accumulated in a virtual counter, and when the sum exceeds one, a counter in the drum maintenance unit is decremented and the fractional part is maintained in the virtual counter. When the number in the drum maintenance unit counter reaches a specified low value, the virtual counter may be disabled so that every print decrements the drum maintenance unit counter to assure that the release agent isn't depleted prematurely, allowing for variations in usage between drum maintenance units. In this way a nominal 30,000 print drum maintenance unit may be extended by over forty percent depending upon the average ink coverage for the particular customer usage profile.
The objects, advantages and other novel features of the present invention are apparent from the following detailed description when read in conjunction with the appended claims and attached drawing.
REFERENCES:
patent: 5099256 (1992-03-01), Anderson
patent: 5389958 (1995-02-01), Bui et al.
patent: 5805191 (1998-09-01), Jones et al.
patent: 6068372 (2000-05-01), Rousseau et al.
Crawford Timothy L.
Johnson David W.
Rousseau Gerard H.
Chau Minh H.
Gray Francis I.
Hilten John S.
Xerox Corporation
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