Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
2003-02-21
2004-08-31
Vo, Anh T. N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
C141S359000, C222S633000
Reexamination Certificate
active
06783215
ABSTRACT:
This application claims priority from Japanese Patent Application No. 2002-048641 filed Feb. 25, 2002, which is incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink container, an inkjet printing apparatus utilizing the ink container, and an ink supplying method and, more particularly, the invention is preferably applied to an inkjet printing apparatus in which ink is intermittently supplied to a printing head for ejecting ink.
2. Description of the Related Art
Inkjet printing apparatuses which form an image on a printing medium by depositing ink to the printing medium using an inkjet printing head include that which form an image by ejecting ink while moving a printing head relative to a printing medium and that which form an image by ejecting ink while moving a printing medium relative to a fixed printing head conversely.
There are two general types of methods of supplying ink to a printing head used in such an inkjet printing apparatus. One is a type in which a supply system is configured such that an amount of ink is always or continuously supplied to a printing head according to the amount of ink ejected (hereinafter referred to as a continuous supply type), and the other is a type in which a printing head is provided with a reservoir (sub-tank or second ink tank) for reserving a predetermined amount of ink and in which a supply system is configured such that ink is supplied to the reservoir from an ink supply source (main tank or first ink tank) at appropriate timing or intermittently (hereinafter referred to as an intermittent supply type).
The continuous supply type is further categorized into two types, for example, when it is used in an inkjet printing apparatus of a type referred to as a serial type in which a printing head is scanned back and forth in predetermined directions relative to a printing medium and in which the printing medium is transported in a direction substantially orthogonal thereto to form an image. One is a type referred to as an on-carriage type in which ink is supplied by integrally or detachably attaching an ink tank to a printing head that is carried and moved back and forth (main scanning) by a carriage. The other is a tube supply type in which an ink tank that is separate from a printing head carried on a carriage is fixedly installed in a part of a printing apparatus other than the printing head and in which the ink tank is connected to the printing head through a flexible tube to supply ink. In some of the latter type, a second ink tank that serves as an intermediate tank between an ink tank and a printing head is mounted on the printing head or the carriage.
When an on-carriage type structure is adopted, there are limits on the project area in a direction perpendicular to the main scanning direction and volume of members that move with a carriage (a printing head and an ink tank undetachably or detachably integrated with the same). Therefore, only an ink tank having a very limited capacity can be used when a small-sized printing apparatus, especially, a portable printing apparatus is to be formed. This results in very frequent replacement of the printing head integral with the ink tank or the ink tank alone, which has been problematic from the viewpoint of operability and running cost. Further, the recent spread of so-called mobile apparatus is remarkable and, for example, ultra-compact inkjet printers have been proposed which can be integrated with notebook type personal computers and digital cameras. It is considered impractical to design such printers in adaptation to the on-carriage method.
When a tube supply type structure is adopted, although members that move with a carriage during main scanning can be made compact to some degree, it is difficult to make the apparatus as a whole compact because a space is required for a tube member to move to follow up the carriage, the tube member coupling a printing head on the carriage and an ink tank located outside the carriage to supply ink. Further, the recent trend is that a carriage is scanned at a high speed to accommodate increases in the speed of printing operations, and resultant severe rocking of a tube that follows the carriage results in changes in the pressure of ink in an ink supply system for the printing head. It is therefore required to provide various complicated pressure buffering mechanisms in order to suppress pressure changes, it has been difficult to achieve a size reduction in this respect too.
On the contrary, in the case of the intermittent supply method that is used for serial type inkjet printing apparatus for example, a relatively small second ink tank and printing head are provided on a carriage; a relatively large first ink tank is provided in a part other than the carriage of the printing apparatus; and a supply system is configured such that ink is supplied from the first ink tank to the second ink tank at appropriate timing. A structure is also employed in which the ink supply system between the first and second ink tanks is spatially separated or the ink channel is blocked with a valve during main scanning to achieve fluid isolation between the first and second ink tanks. Basically, this makes it possible to solve various problems attributable to the size of moving members as described above such as an ink tank and the rocking of a tube that have limited efforts to achieve a small size in the case of the continuous supply type.
When an intermittent supply type structure is adopted, however, it is important to adjust the pressure inside a second ink tank properly, because a negative pressure relative to the atmosphere must be generated in order to maintain ink meniscuses formed at ejection openings. While the second ink tank may be located in a position lower than the position of ejection openings of the printing head to generate a negative pressure in the second ink tank naturally, this puts a limit on even the position and attitude or orientation of the ink tank and has resulted in problems including leakage of ink from the ejection openings especially in case that a portable printing apparatus is to be provided which is unstable in attitude or orientation during transportation.
Under such circumstances, proposals have been made including a proposal in which a porous member such as a sponge for holding ink is contained a second ink tank to generate an adequate negative pressure. Such a structure is advantageous even for a portable printing apparatus whose attitude is unstable during transportation. However, the ink containing efficiency of the second ink tank is limited by the negative pressure generating mechanism such as a porous member provided in the second ink tank. Further, designing may be limited with respect to the endurance of the porous member against deposition and deterioration of a dye or pigment in ink, which also reduces freedom in selecting ink.
Further, in such a structure, since the porous member is always over-charged with ink when ink charging is completed, the over-charged ink in the porous member must be discharged as waste ink without fail by performing an operation of sucking the printing head through the ejection openings after the charging is completed in order to apply a required negative pressure to the printing head. That is, a problem arises in that a charging operation is accompanied by the generation of waste ink.
SUMMARY OF THE INVENTION
The invention was conceived taking the above-described problems into consideration, and it employs an intermittent supply system as an ink supplying method and provides a structure which does not fundamentally result in waste of ink such as generation of waste ink associated with a charging operation to apply a predetermined negative pressure to a printing head, which achieves high charging efficiency and a short charging time, and which can be easily kept resistant to ink, i.e., a structure with which freedom in selecting ink can be increased.
The invention thus contributes to the structure of a compact and portabl
Hirai Yasuyuki
Inamura Shusuke
Inoue Hiroyuki
Iwasaki Takeshi
Nojima Takashi
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Vo Anh T. N.
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