Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1998-07-21
2001-08-21
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S019000, C347S023000, C347S049000
Reexamination Certificate
active
06276777
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention generally relates to ink jet and other types of printers and, in particular, to a variable maximum operating temperature for a printhead.
BACKGROUND OF THE INVENTION
Many modern printing devices incorporate thermal ink jet technology. Typically, this technology utilizes a printhead (also known as a pen) having a silicon die supporting one or more vaporization chambers. During operation, resistors or other ink ejection elements on the silicon die are heated in order to vaporize and eject ink through nozzles overlying the vaporization chambers, thereby causing dots of ink to be printed on a recording medium, such as paper.
In general, the temperature of a printhead will change or fluctuate while printing. When a printer is printing “light” areas or in a slow mode, the printhead temperature will drop; when a printer is printing “dense” areas or in a fast mode, the printhead temperature will rise. As the printhead temperature changes, it is important to ensure that the silicon die does not overheat. Overheating results primarily when the printhead has run out of ink (OOI) or because the printhead is experiencing a global de-prime (i.e., a disruption of the continuous flow of ink into a vaporization chamber due to a large air bubble caused by out-gassing or air-gulping). In such cases, the problem of overheating must be detected quickly and efficiently in order to avoid permanent damage to the printhead. Furthermore, if the printhead has run out of ink or is experiencing a global de-prime, printing must be interrupted to avoid the waste of paper.
Previous techniques set a fixed maximum operating temperature for the printhead; when the temperature of the printhead exceeded this fixed maximum operating temperature, a thermal shutdown was initiated for the printer. To avoid improper thermal shutdown when the printhead was simply getting warmer (for example, because the printer was printing a high density area or a in fast print mode), the fixed maximum operating temperature was required to be set conservatively high. Although such previous techniques were easy to implement, their effectiveness was limited only to cases where out-of-ink or global de-prime conditions occurred while printing dense areas of ink in fast mode. In fact, if either of the two failure conditions occurred while printing a low density area or while printing a high density area under a slow print mode, the printhead temperature would not increase sufficiently to trigger thermal shutdown. Accordingly, previous techniques did not adequately address the problems associated with overheating in a printhead.
SUMMARY OF THE INVENTION
The disadvantages and problems associated with shutting down a printer to prevent overheating of a printhead have been substantially reduced or eliminated using the present invention.
In accordance with one embodiment of the present invention, a system includes an operating condition sensor for detecting an operating condition within a printer and a printhead temperature sensor for detecting a temperature of a printhead. A controller is coupled to the operating condition sensor and the printhead temperature sensor. The controller compares the detected temperature of the printhead against a variable maximum operating temperature which varies according to the detected operating condition.
In accordance with another embodiment of the present invention, a method is provided which comprises the following steps: creating a thermal model which relates an operating condition of a printer to a temperature for a printhead incorporated into the printer, and establishing a variable maximum operating temperature for the printhead based upon the thermal model, the variable maximum operating temperature varying according to the operating condition.
In accordance with yet another embodiment of the present invention, a printer comprises a print cartridge having a printhead and a system for varying the maximum operating temperature of the printhead.
Important technical advantages of the present invention include varying the maximum operating temperature for a printhead depending upon the actual operating conditions or characteristics of a printer, wherein a printer condition is something which can be detected and a printer characteristic is something which can be calculated or predicted from one or more printer conditions. Specifically, the maximum operating temperature may be characterized as a function of any one, or a combination, of various printer conditions or characteristics, such as duty cycle, print density, print speed, and the like, which can be empirically detected, calculated, or predicted. Thus, different maximum operating temperatures will be applied to different operating conditions and/or characteristics. For any set of conditions/characteristics under which a printer may operate, if a detected temperature for the printhead exceeds the maximum operating temperature applicable to those conditions/characteristics, the printer will be shut down. In this way, the present invention reduces the likelihood that a printhead will overheat. Accordingly, this technique extends the useful life of a printhead and reduces waste associated with paper that otherwise might be fed through the printer. Other important technical advantages are readily apparent to one skilled in the art from the following figures, descriptions, and claims.
REFERENCES:
patent: 4791435 (1988-12-01), Smith et al.
patent: 4860034 (1989-08-01), Watanabe et al.
patent: 4910528 (1990-03-01), Firl et al.
patent: 5075690 (1991-12-01), Kneezel
patent: 5107276 (1992-04-01), Kneezel et al.
patent: 5235346 (1993-08-01), Yeung
patent: 5363134 (1994-11-01), Barbehenn et al.
patent: 5576745 (1996-11-01), Matsubara
patent: 5648806 (1997-07-01), Steinfield et al.
patent: 5675367 (1997-10-01), Scheffelin et al.
patent: 5736995 (1998-04-01), Bohorquez et al.
patent: 403 140 248 (1991-06-01), None
Castelltort Sebastia
Donovan David H.
Schiaffino Stefano
Barlow John
Hewlett--Packard Company
Hsia David C.
Skjerven Morrill & MacPherson LLP
Stewart Jr. Charles W.
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