Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2002-04-10
2003-09-16
Hsieh, Shih-Wen (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06619780
ABSTRACT:
BACKGROUND
This invention relates generally to inkjet printing mechanisms, and in particular to techniques for servicing a printhead of an inkjet printing mechanism.
Inkjet printing mechanisms such as thermal inkjet printers and piezoelectric printers use pens which shoot drops of liquid colorant, referred to generally herein as “ink,” onto a page. Each pen has a printhead formed with very small nozzles through which the ink drops are fired during printing operations. The printhead can easily dry out if the printer is not used for a period of time. The drying out occurs because the solvent part of the liquid ink stored in the printhead evaporates. Solids left behind after the evaporation tend to clog the passages and orifice plate of the printhead and may consequently cause the performance of the printhead to be reduced. One way to prevent or at least slow down the evaporation of the ink is to cap the printhead during the period when the printer is not active. Such a capping usually happens when a print job has been executed. However, capping of the printhead and the necessary removing of the capping prior to executing the print job may reduce the quality of the first printout after removing the capping. To improve the quality of the printout, printer designers generally introduce a servicing routine for cleaning the printhead after removing the capping and before executing a print job. Such a servicing routine is called out-of-cap servicing and is done to make sure that the printer, specifically, the printhead is in a satisfactory functional state.
Regarding when to perform the out-of-cap servicing, one practice is that the printer performs the servicing only when a print job comes in. Normally, such a servicing takes quite an amount of extra time to meet the quality requirement of the printout. Since the extra time is taken after the print job is sent but before the print job is executed, the time between a user clicking a “PRINT” button on the user's printer driver and the first sheet of the print job being printed out can be unsatisfactorily long. In other words, the throughput of the printer may not be satisfactory.
Alternatively, the printer can perform the out-of-cap servicing immediately upon being switched-on along with an additional servicing right before a print job is executed. However, such a proactive servicing may not satisfy both requirements for printout quality and printer throughput at the same time in that the printer still needs to select the kind of additional servicing, which is performed prior to the print job. In the conventional practice, the selection is normally fixed and may not achieve the optimal balance between the throughput and the quality of printout for different users with different behaviors. In addition, the proactive servicing upon the printers being switched on may be unnecessary or redundant in such a situation that the printer is switched off before it has received any print jobs.
Therefore, there is a need for an improved servicing method that is more user-adaptive and may better meet both requirements for printout quality and throughput.
SUMMARY
According to an aspect of the present invention, in a method for servicing a printhead of an inkjet printing mechanism, a plurality of time difference information is collected by the printing mechanism. Each time difference information represents a period of time passed between end of a last print job and receipt of a succeeding print job. The print jobs are sent from a computer connected to the printing mechanism. Subsequently, the printing mechanism uses the plurality of time difference information to determine a nominal time information representing an amount of time. After the determination of the nominal time information, the printing mechanism periodically performs a first level servicing dependent upon the nominal time information.
In another aspect of the invention, in a method for servicing a printhead of an inkjet printing mechanism, a nominal time information representing an amount of time is firstly determined. If a print job arrives at the printing mechanism before the amount of time has passed since a start point set by the printing mechanism, a first level servicing is performed by the printing mechanism when the print job arrives. If the print job arrives at the printing mechanism after the amount of time has passed since the start point, the first level servicing is performed when the amount of time has just passed.
In a third aspect of the invention, a medium having a program recorded thereon is provided. The program makes an inkjet printing mechanism execute a procedure for servicing a printhead of the inkjet printing mechanism. The procedure includes the following steps
collecting a plurality of time difference information by the printing mechanism, each time difference information representing time passed between end of a last print job and receipt of a succeeding print job, the print jobs being sent from a computer connected to the printing mechanism;
using the plurality of time difference information by the printing mechanism to determine a nominal time information representing an amount of time; and
after the determination of the nominal time information, periodically performing a first level servicing by the printing mechanism dependent upon the nominal time information.
In a fourth aspect of the invention, a computer program element is provided and makes an inkjet printing mechanism execute a procedure for servicing a printhead of the inkjet printing mechanism. The procedure includes
collecting a plurality of time difference information by the printing mechanism, each time difference information representing time passed between end of a last print job and receipt of a succeeding print job, the print jobs being sent from a computer connected to the printing mechanism;
using the plurality of time difference information by the printing mechanism to determine a nominal time information representing an amount of time; and
after the determination of the nominal time information, periodically performing a first level servicing by the printing mechanism dependent upon the nominal time information.
Other aspects and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings, which illustrates by way of example the principles of the invention.
REFERENCES:
patent: 5847726 (1998-12-01), Hori
patent: 6132026 (2000-10-01), Taylor
Agarwal Manish
Nordlund Michael
Hewlett--Packard Development Company, L.P.
Hsieh Shih-Wen
Main Richard
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