Researchers submit patent application 'Inkjet Printer'; invention features filter arranged in its ink flow passage, can efficiently execute storage, discharge of air bubbles inside of ink flow

WASHINGTON , May 29, 2013 () – From Washington, D.C., VerticalNews journalists report that a patent application by the inventors Nabeshima, Naozumi (Tokyo, JP), filed on January 4, 2013, was made available online on May 23, 2013.

The patent's assignee for patent application serial number 734331 is Canon Kabushiki Kaisha.

News editors obtained the following quote from the background information supplied by the inventors: "The present invention relates to an inkjet printer in which a filter is arranged in an ink flow passage, and in more detail, to an inkjet printer which can efficiently execute storage and discharge of air bubbles flowing in an ink flow passage in which a filter is arranged.

"An inkjet printer (hereinafter, called 'printer' simply) is provided with a filter disposed in an ink flow passage for removing foreign objects and air bubbles in the ink flow passage in such a manner as to accurately eject liquids (ink) from inkjet nozzles. The air bubbles removed by the filter are stored in the ink flow passage, pass through the filter in a recovery operation for each constant interval, and are discharged from the inkjet nozzles.

"The filter removes the foreign object or the air bubbles to create excellent printing, and on the other hand, attachment of the air bubbles to the filter increases pressure losses of the filter depending on ink properties or an ink flow amount and raises a problem of causing a print failure.

"At the time of discharging the air bubbles removed with the filter in the recovery operation, since the ink is also discharged simultaneously, it is necessary to restrict an ink amount to be discharged by extending the recovery interval (that is, reducing the number of times of the recovery operations), for example.

"The following measures are proposed for solving these problems.

"The first measure is to dispose an evacuation space in the upward direction of gravity (upward in the perpendicular direction) upstream of the filter. In consequence, it is possible to remove the air bubbles flowing together with the ink by the filter and to let out the air bubbles into the evacuation space.

"The second measure is to reduce pressures in a filter portion at recovery operation for pressing a deformable member of the filter portion against the filter. Inconsequence, there is proposed an inkjet printer which increases a discharge efficiency of the air bubble, extends the recovery interval, and restricts an ink amount to be discharged.

"Japanese Patent Laid-Open No. 2006-168224 discloses the construction corresponding to the first measure as described above, in which the ink is separated from the air bubble by the filter and the air bubble is let out to the evacuation space. However, an ink introducing port and an ink feeding port are arranged substantially on a straight line and there is almost no ink stream for guiding the air bubble to the evacuation space. Therefore, in a case where the ink stream is sequential, the air bubble is attached to the filter depending on ink properties or a size of the air bubble and an ink flow amount, which reduces an effective area of the filter. Thereby the pressure loss is increased, thus creating a possibility of causing a printing failure. In addition, since the evacuation space is right above the filter, when the ink flow amount is increased, the pressure in the filter portion is decreased and the separated air bubble is expanded, there is a possibility that the air bubble is again involved in the ink stream.

"Japanese Patent Laid-Open No. 2006-051832 discloses the construction corresponding to the second measure as described above, in which the deformable member is pressed against the filter for improving the discharge efficiency of the air bubble. According to this construction, the deformable member requires flexibility, and further, since the flexibility is difficult to be compatible with a percolation performance of water vapors or gases of the deformable member itself, there is a possibility that the air bubbles grow due to gas percolation from the deformable member to inhibit extension of the recovery interval."

As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "An object of the present invention is to provide an inkjet printer which can securely separate air bubbles from an ink stream for storage to restrict filter clogging due to the air bubbles, and can extend a recovery interval by efficient air bubble discharge.

"In order to achieve the above object, the present invention is provided with an inkjet printer comprising at least an ink tank for retaining ink, inkjet nozzles for ejecting the ink to perform a print, an ink flow passage for connecting the ink tank and the inkjet nozzles, a filter disposed in the middle of the ink flow passage, and suction means for sucking the ink through the inkjet nozzles in recovery, further comprising opening and closing means for opening and closing the ink flow passage, and a filter chamber in which the filter is arranged horizontally, wherein the opening and closing means is disposed upstream of the filter chamber, a first room is disposed downstream of the filter and a second room is disposed upstream of the filter in the filter chamber, an ink discharge opening is disposed in the first room for supplying the ink to the inkjet nozzles, an ink supply opening to which the ink is supplied from the ink tank and an air bubble storage unit for storing the air bubble flowing in with the ink are disposed in the second room, the ink supply opening and the ink discharge opening arranged to sandwich the filter are displaced with each other in a horizontal direction for arrangement, the air bubble storage unit is arranged upward of the ink supply opening in a perpendicular direction and is arranged to oppose the ink discharge opening in such a manner as to sandwich the filter therebetween, and the suction means expands the air bubble stored in the air bubble storage unit to a size equal to or more than that of the second room.

"Since the present invention is constructed as described above, to the air bubble having flowed in from the ink supply opening, a buoyant force is generated in a direction directly opposite to a force in the gravity downward direction (downward in the perpendicular direction) caused by the ink stream. In consequence, it is restricted that the air bubble is pressed against the filter by the ink stream to stay in close contact with the filter. Further, since the air bubble is subjected to a force acting toward the air bubble storage unit from the ink stream, the air bubble can be easily stored in the air bubble storage unit. In addition, since the air bubble storage unit is disposed upward of the ink supply opening in the perpendicular direction, the air bubble stored in the air bubble storage unit is prevented from being involved in the ink stream to be attached to the filter.

"As a result, since it is possible to furthermore restrict the attachment of the air bubble to the filter, the ink can be supplied to the inkjet nozzles without damaging the effective area of the filter to perform a preferable print.

"Further, since the stored air bubble is reduced in pressure more than in the second room and expanded to be discharged, the flexibility is not required as a material of the second room and a material low in the percolation performance of water vapors and gases can be selected. Therefore, evaporation of the ink from the second room or percolation of the gases into the second room can be restricted to restrict growth of the air bubble, extending the recovery period.

"According to the present invention, a volume of the air bubble storage unit is set to be larger than a total volume of a volume of remaining air bubbles at recovery completion and a volume of inflow air bubbles flowing in by the time of the next recovery.

"According to this construction, since the remaining air bubbles and the inflow air bubbles stored in the air bubble storage unit are positioned above the ink supply opening in the gravity upward direction (upward in the perpendicular direction), the air bubbles are difficult to be involved in the ink stream and more difficult to be attached to the filter. Therefore, since the attachment of the air bubble to the filter is restricted between the current recovery and the next recovery, the ink can be supplied to the inkjet nozzles without damaging the effective area of the filter to perform the preferable print.

"The present invention is further constructed such that an angle between a straight line connecting the ink supply opening with the ink discharge opening and the filter arranged horizontally is equal to or less than 45.degree.

"According to this construction, the force directing the inflow air bubble flowing in from the ink supply opening toward the air bubble storage unit is larger than the force pressing it against the filter. As a result, also in the higher-speed ink stream, the ink can be supplied to the inkjet nozzles without damaging the effective area of the filter to perform the preferable print.

"According to these constructions, the clogging due to the attachment of the air bubbles to the filter can be restricted, and since reduction of the effective area of the filter can be restricted by them, it is possible to expand the corresponding range of the ink properties or the ink flow amount. In addition, since the growth of the air bubble in the air bubble storage unit can be restricted, it is possible to extend the recovery interval to reduce the waste ink amount.

"Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings).

BRIEF DESCRIPTION OF THE DRAWINGS

"FIG. 1 is a schematic diagram explaining the construction of an inkjet printer in a first embodiment according to the present invention;

"FIG. 2 is a schematic diagram explaining behaviors of air bubbles in a filter chamber of the printer in FIG. 1;

"FIG. 3 is a schematic diagram explaining discharge of air bubbles in the filter chamber of the printer in FIG. 1;

"FIG. 4 is a schematic diagram explaining an inkjet printer in a second embodiment according to the present invention and similar to FIG. 2;

"FIG. 5 is a perspective view of an inkjet printer head to which the present invention is applied; and

"FIG. 6 is a cross section taken along line VI-VI in FIG. 5."

For additional information on this patent application, see: Nabeshima, Naozumi. Inkjet Printer. U.S. Patent Application Serial Number 734331, filed January 4, 2013, and posted May 23, 2013. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=4772&p=96&f=G&l=50&d=PG01&S1=20130516.PD.&OS=PD/20130516&RS=PD/20130516

Keywords for this news article include: Asia, Japan, Canon Kabushiki Kaisha.

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