Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-01-19
2002-03-05
Yockey, David F. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S035000
Reexamination Certificate
active
06352333
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an ink-jet printing apparatus, for example, a full-line-type ink jet printer, a serial-type ink jet printer, and other types of printers, and a method of printing an image on a sheet by ejecting ink drops, and more particularly, the present invention relates to an ink jet printing apparatus and method for preventing an ink clog in one or more nozzles of an ink-jet printing apparatus.
2. Description of Background Art
Ink-jet printing apparatuses for use in a printer, a facsimile, a copier, and other such devices can be generally classified into two types of ink jet printers. The first type is referred to as a serial-type-ink-jet printing apparatus and includes an ink jet head having a nozzle, which head is mounted on a carriage and is capable of printing an image on a sheet by ejecting ink drops during both scanning or movement of the carriage and the attached print head in a main scanning direction and during a sheet movement in a sub scanning direction.
The second type of ink jet printing apparatus is referred to as a line-type-ink-jet printing apparatus and includes an ink jet head having a plurality of nozzles each ejecting ink drops on demand, which head is arranged to extend in a widthwise direction of the sheet to cover almost an entire width of a sheet and which is capable of printing an image on a sheet by ejecting ink drops during transportation of the sheet in a lengthwise direction.
However, when the ink jet head has not been used for a long time (an ink drop has not been ejected from the ink jet head for a long time), and, accordingly, the viscosity of the ink stored in the nozzle is increased due to evaporation of the ink or other conditions, an ejecting operation of ink drops through the nozzle may be deleteriously affected or even prevented due to the occurrence of clogging of the ink in the nozzle. To avoid such a problem, ink jet printing apparatuses generally execute a cleaning procedure in order to prevent nozzle clogging. During the clog-preventing procedure, ink is ejected from the nozzle or nozzles for cleaning or nozzle-clearing purposes and not for the purpose of printing an image on a sheet. Such a nozzle-clog-preventing ink ejecting operation may be performed such that only nozzles which have not ejected ink drops within a predetermined time period have ink ejected therefrom. Alternatively, all of the nozzles regardless whether any of nozzles have ejected ink drops within the predetermined time period, are made to periodically eject ink drops to prevent clogging of the nozzles.
For example, in a serial-type ink jet printer described in Japanese Laid Open Patent Publication Numbers 7-47679/1995 and 7-81085/1995, a nozzle-clog-preventing ink receiving device is provided at a position adjacent to a sheet transportation path so as to receive ink drops in the ink receiving device which ink drops are ejected from nozzles of the ink jet head during a nozzle-clog preventing ink ejection. The carriage having the ink jet head periodically moves to a position above the nozzle-clog-preventing ink receiving device and executes a nozzle-clog-preventing ink ejection. Thereby, a condition of the nozzles for readily and completely ejecting ink drops is obtained without ink being clogged in the nozzles.
Further, in a full-line type ink jet printing apparatus, a nozzle clog preventing ink ejection device is located beside a printing station at which an image is printed, in order to receive ink drops ejected during the nozzle-clog-preventing ink ejection. An ink jet head unit is swung or slid from the printing station so as to be moved to a position above the nozzle-clog-preventing ink ejection device to execute the nozzle-clog-preventing ink ejection into the nozzle-clog-preventing ink ejection device. The head unit then returns to the printing station.
Further, as described in Japanese Laid Open Patent Application Number 6-15815/1994, nozzle-clog-preventing ink ejection is executed such that nozzle-clog-preventing ink is ejected onto a sheet to avoid using an unnecessary nozzle-clog-preventing ink ejection container to minimize an ink jet printer size and to increase a printing speed.
However, in such a full-line type ink jet printer, since the head unit is moved to a position at which nozzle-clog-preventing ink ejection is executed from the printing station, a predetermined time period is required for such a movement of the head unit. Thus, if the nozzle-clog-preventing ink ejection is executed during a printing operation, printing productivity remarkably decreases and the full-line type ink jet printer cannot function as desired as a high speed printer.
Further, a full-line type ink jet printer frequently requires nozzle-clog-preventing ink ejection, since ink drops used therein tend to increase in viscosity due to evaporation thereof. This is because such a full-line-type-ink-jet printer is generally designed to have a printing productivity of from about 30 PPM (prints per minutes) to about 60 PPM, and, accordingly, such a printer generally uses a heater that applies heat to the sheet to improve an adherence of the ink drops to the sheet.
Thus, the above-described problems are more serious in such a full-line type ink jet printer. Further, in a full-color-ink-jet printer including a plurality of heads each ejecting different mono color ink therefrom, which has been recently introduced due to the ease of producing a full color image by mixing a plurality of different single color inks on a sheet, a mechanism used for such a back and forth movement of the head units becomes complex.
To avoid such complexity of the mechanism, nozzle clog preventing ink ejection can be executed directly on a sheet as explained in the above-described serial type ink jet printing apparatus.
However, it is not practical for an ink jet printing apparatus that is generally expected to produce a high quality image, since the sheet receives unnecessary ink drops thereon, and, accordingly, a quality of the image produced on the sheet is greatly lowered.
Further, if nozzle-clog-preventing ink ejection is executed onto a sheet every time after an image is printed on a previous sheet, a plurality of sheets are required to be fed and to receive ink drops ejected during a nozzle-clog-preventing ink ejection, in order to produce an image. As a result, a printing speed is substantially decreased and sheets are wasted.
SUMMARY OF THE INVENTION
To overcome the problems described above, preferred embodiments of the present invention provide an ink-jet printing apparatus that prevents any clogging of ink-jet nozzles while also ensuring rapid printing speed, high quality printed images and avoiding wasted paper and any increase in printer size. Preferred embodiments of the present invention also eliminate the need for moving an ink jet print head to an area outside of a sheet periphery for ejecting ink to prevent nozzle clogging and also avoids the need to use waste sheets of paper for receiving the nozzle-clog-prevention clog-prevention ink ejection drops.
Preferred embodiments of the present invention provide an ink jet printing apparatus including a head unit having at least nozzle arranged to eject ink drops on demand, a sheet-transporting path disposed below the head unit and adapted to transport a sheet through the head unit, and an ink deposit disposed below the sheet transporting path, which is arranged to receive ink drops ejected from the nozzle during a nozzle-clog-preventing ink ejection operation.
It is noted that the ink deposit is disposed in a fixed position below the sheet transporting path and is not moved in order to receive ink drops which are discharged during a nozzle-clog-preventing ink ejection operation. Furthermore, it is noted that the head unit and the ink deposit are arranged such that the ink deposit is open and exposed to the at least one nozzle of the head unit except when paper is fed between the at least one nozzle and the ink deposit during a printing operation.
The ink deposit may preferably
Fujii Mitsumi
Matsumoto Shuzo
Murai Takeo
Greenberg & Traurig, LLP
Ricoh & Company, Ltd.
Yockey David F.
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