Patent Publication Number: US-8118069-B2

Title: Method for loading liquid, liquid container and head cartridge

Description:
TECHNICAL FIELD 
     This invention relates to a liquid loading method for housing liquid such as ink in a liquid container, a liquid container for containing liquid such as ink, and a head cartridge comprising the liquid container. 
     BACKGROUND ART 
     A printing apparatus, for example, a so-called serial-type ink jet printing apparatus, comprises a carriage movable in the main scan direction which is mounted with a printing head capable of ejecting ink and an ink tank (liquid container) for containing the ink fed into the printing head. For printing an image, the printing apparatus repeats an operation of ejecting ink from an ejection port of the printing head toward a printing medium while moving the carriage in the main scan direction, and an operation of conveying the printing medium in a sub scan direction crossing to the main scan direction. The ink drops ejected from the printing head impact the printing medium to print the required image. 
     A mainstream ink used in such ink jet printing apparatus includes a dye as the colorant. In general, however, a dye ink somewhat lacks light fastness and gas fastness, and in some cases a print with the dye ink exhibits little image stability with durability in a special application such as for an outdoor notice. 
     In recent days, a printing apparatus using ink including a pigment as the colorant has been made available. A pigment ink has excellent light fastness and gas fastness, resulting in the print showing sufficient image stability. However, unlike the dye ink, the pigment ink needs to be handled with consideration for its dispersion properties. 
     The pigment molecules in the pigment ink do not dissolve in the ink solution as the dye molecules in the dye ink do, and are suspended and dispersed. If an ink tank containing the pigment ink is left still for a while, in some cases gravity makes the pigment particles gradually settle in the ink tank, giving rise to a concentration gradient of the pigment particles in the height direction of the ink tank. Specifically, a layer of a high colorant concentration is located in the bottom portion of the ink tank and a layer of a low colorant concentration is located in the upper portion thereof. When the ink is fed from the ink tank to the printing head in this situation to start and continue an operation of printing an image, a difference in concentration may possibly occur on the image between an initial stage and a later stage of the printing operation. 
     To give a concrete illustration, an ink jet printing apparatus structured to supply ink from the bottom of an ink tank to a printing head is considered. When the printing apparatus is installed with the aforementioned ink tank having a concentration gradient of the pigment particles and then starts the printing operation, the ink contained in the lower portion of the ink tank with a high colorant concentration is supplied in at an early stage in the printing, thus printing an image with a density higher than necessary. Thereafter, as the printing operation continues to be performed, the density of the printed image is gradually reduced along with the consumption of ink in the ink tank. Then, when the amount of the ink in the ink tank becomes low, the ink remaining in the ink tank has a lower colorant concentration than the original one. For this reason, even when the image is printed based on the same image data as that at the beginning of the printing operation, the printing density becomes lighter. Specifically, since a large diameter or a high specific gravity of the pigment particle makes the pigment particle significantly apt to settle, even when a non-use state of the ink tank lasts just for a few days, a concentration gradient as much as to affect the image may possibly occur. 
     The colorant concentration of the ink ejected from the printing head changes with the use of the ink tank as described above. This not only causes a difference in density of the printed image between the initial service stage and the later service stage of the ink tank. For example, in a color ink jet printing system using a plurality of color inks to express hues in predetermined color balance, the color balance may be lost. This event is to be recognized as a more remarkable problem of the difference between the image densities. 
     In order to maintain the colorant concentration of the ink drops ejected from the printing head within a constant concentration range regardless of the amount of ink remaining in the ink tank, the pigment molecules are desired to be uniformly dispersed in the ink tank, at least during the printing operation. 
     One proposal made for achieving such uniform dispersion of the pigment molecules is a structure for providing a stirring member in the ink tank for stirring the pigment molecules. 
     Japanese Patent Laid-Open No. 2005-066520 discloses an ink pack provided with a manually operable stirring member. The stirring member is shaped so as to be inserted into the ink pack from outside. An outwardly projecting part of the stirring member serves as a manipulating portion for operating a stirring section of the stirring member extending into the ink pack. Specifically, a user swings the stirring portion at regular intervals or as needed in order to stir the ink in the ink pack for dispersion of the pigment molecules. 
     Also, Japanese Patent Laid-Open No. 2005-066520 discloses an ink cartridge provided with a swinging member for stirring the ink in the tank through the use of an inertial force arising from the movement of the carriage during the printing operation, of which an example described is a stirring member formed integrally with the ink cartridge case. In this example, the stirring member extends in such a manner to hang down from the ceiling of the ink cartridge case toward the bottom, and has a cylindrically shaped weight formed at the lower end. An inertial force arising from an accelerating, stopping or reversal operation of the carriage makes the stirring member swing around the fulcrum, which is the pivoted end joined to the ceiling, in the moving direction of the carriage to stir the ink in the ink cartridge. 
     In addition, Japanese Patent Laid-Open No. 2005-066520 discloses another example of a stirring member which is not secured to the ink cartridge case and is movable freely over the bottom inner face of the ink cartridge. This stirring member is operative to move over the bottom inner face of the ink cartridge to stir the ink by the inertial force arising from the accelerating, stopping or reversal operation of the carriage. 
     Japanese Patent Laid-Open No. 2004-216761 discloses a stirring mechanism which comprises a shaft-shaped weight swinging in the right and left directions of the swinging central axis by the inertial force arising from the movement of the carriage, and a plurality of fins singing in the right and left directions in combination with the shaft-shaped weight. In this structure, since the plurality of the fins are arranged in parallel in the height direction of the ink cartridge, the ink is stirred equally from the upper portion to the lower portion of the ink cartridge. 
     However, neither of the foregoing Japanese Patent Laid-Open Nos. 2005-066520 and 2004-216761 have particular reference to a method for loading ink (liquid) into an ink cartridge (liquid container) provided with a stirring member. 
     DISCLOSURE OF THE INVENTION 
     The present invention provides a liquid loading method, a liquid container and a head cartridge which allow the liquid container to be appropriately loaded with liquid such that a stirring member provided in the liquid container fully fulfills its function. 
     According to an aspect of the present invention, a loading method for loading liquid into a liquid container comprising a liquid reservoir capable of housing liquid, and a stirring member provided in the liquid reservoir and having a hollow portion formed therein for guiding the liquid in the liquid reservoir, comprises the steps of: inserting a liquid loading member for loading liquid into the liquid reservoir, from the outside of the liquid container into the liquid reservoir; and loading the liquid into the liquid reservoir through the liquid loading member to reach or exceed a level for submerging at least a part of the hollow portion of the stirring member in the liquid. 
     According to another aspect of the present invention, a liquid container comprises: a liquid reservoir capable of housing liquid; a stirring member provided in the liquid reservoir and having a hollow portion formed therein for guiding the liquid in the liquid reservoir; and a portion allowing a liquid loading member for loading liquid into the liquid reservoir to be inserted from the outside of the liquid container into the liquid reservoir, wherein the portion is located in a site allowing the liquid to be loaded into the liquid reservoir through the liquid loading member to reach or exceed a level for submerging at least a part of the hollow portion of the stirring member in the liquid. 
     According to yet another aspect of the present invention, a head cartridge comprises: the liquid container in the case of another aspect; and a liquid discharge head capable of discharging the liquid introduced from the liquid delivery port of the liquid container. 
     According to still another aspect of the present invention, a liquid loading method for loading liquid into a liquid container comprising a liquid reservoir capable of housing liquid, and a stirring member having a hollow portion formed therein for guiding the liquid in the liquid reservoir, comprises the step of: inserting a liquid loading member for loading liquid into the liquid reservoir, from the outside of the liquid container into the stirring member provided in the liquid container; and loading the liquid into the liquid reservoir through the liquid loading member. 
     According to the present invention, the loading of liquid into the liquid container through the liquid-loading member inserted into the liquid container from outside makes it possible to load liquid without its bubbling or to load liquid in such a manner as to remove the bubbles produced. As a result, it is possible to reduce the amount of bubbles occurring and/or remaining in the liquid container and a hollow portion of the stirring member to minimize the adverse effects of bubbles which may possibly interrupt the flow of the liquid. 
     For example, the liquid-stirring function of the stirring member can be fully fulfilled by reducing the amount of bubbles occurring and/or remaining in the liquid container, and in particular, in the hollow portion of the stirring member. Also, the full loading of the liquid is made possible without its being inhibited by the bubbles in the liquid container, thus making it possible to reliably load ink to the extent that the stirring member can adequately fulfill its stirring function. In other words, the liquid can be fully loaded in an amount to reach or exceed a level for submerging at least a part of the hollow portion of the stirring member in the liquid when the liquid container is in the operating position (positioned to orient the liquid delivery port downward in the gravity direction). 
     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 an outside perspective view of a printing apparatus in a first embodiment of the present invention; 
         FIG. 2  is a perspective view illustrating an internal mechanism of the printing apparatus in  FIG. 1 ; 
         FIG. 3  is a perspective view of a printing head cartridge and an ink cartridge which are mountable on a carriage in  FIG. 2 ; 
         FIG. 4  is a perspective view of the ink cartridge in  FIG. 3 ; 
         FIG. 5  is an exploded perspective view of the ink cartridge in  FIG. 3 ; 
         FIG. 6  is a perspective view of the principal part for illustrating the mounting of a swinging member in  FIG. 5 ; 
         FIG. 7  is an enlarged perspective view of the swinging member in  FIG. 5 ; 
         FIG. 8  is a perspective view of the principal part for illustrating an exemplary modification of the swinging member in the first embodiment of the present invention; 
         FIG. 9A ,  FIG. 9B  and  FIG. 9C  are sectional views each showing an ink cartridge for illustrating a method for loading ink into the ink cartridge shown in  FIG. 6 ; 
         FIG. 10A ,  FIG. 10B  and  FIG. 10C  are sectional views each showing an ink cartridge for illustrating another example of a method for loading ink into the ink cartridge shown in  FIG. 6 ; 
         FIG. 11A ,  FIG. 11B  and  FIG. 11C  are sectional views each showing an ink cartridge for illustrating still another example of a method for loading ink into the ink cartridge shown in  FIG. 6 ; 
         FIG. 12A ,  FIG. 12B ,  FIG. 12C  and  FIG. 12D  are schematic structural diagrams each showing the principal part of the printing apparatus for illustrating the operation of the carriage in  FIG. 2 ; 
         FIG. 13A  to  FIG. 13H  are sectional views each showing an ink cartridge for illustrating the operation of the swinging member in  FIG. 6 ; 
         FIG. 14  is an exploded perspective view of an ink cartridge in a second embodiment of the present invention; 
         FIG. 15  is a perspective view of the principal part for illustrating the mounting of a swinging member in  FIG. 14 ; 
         FIG. 16  is an enlarged perspective view of the swinging member in  FIG. 14 ; 
         FIG. 17A  and  FIG. 17B  are sectional views each showing an ink cartridge for illustrating a method for loading ink into the ink cartridge shown in  FIG. 14 ; 
         FIG. 18A ,  FIG. 18B  and  FIG. 18C  are sectional views each showing an ink cartridge for illustrating the operation of the swinging member in  FIG. 14 ; 
         FIG. 19  is a perspective view of the principal part for illustrating the mounting of a swinging member in a third embodiment of the present invention; 
         FIG. 20A  and  FIG. 20B  are sectional views each showing an ink cartridge for illustrating a method for loading ink into the ink cartridge shown in  FIG. 19 ; 
         FIG. 21  is a perspective view of the principal part for illustrating the mounting of a swinging member in a fourth embodiment of the present invention; and 
         FIG. 22A  and  FIG. 22B  are sectional views each showing an ink cartridge for illustrating a method for loading ink into the ink cartridge shown in  FIG. 21 . 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     This invention has been made with attention focused on the fact that, when a stirring member provided for stirring liquid in a liquid container has a hollow portion formed therein for guiding the liquid, bubbles existing in the liquid container, in particular in the hollow portion of the stirring member affect the function of stirring the ink. That is, if bubbles exist in the liquid container, in particular in the hollow portion of the stirring member, the flow of the ink is inhibited, which may possibly make the performance of the function of stirring the ink insufficient. The present invention achieves the loading of ink which can reduce occurrence and remaining of bubbles for the purpose of allowing a stirring member to fully perform its stirring function. 
     Embodiments of the present invention will be described below with reference to the drawings. 
     First Embodiment 
     A liquid container in this embodiment is an example of the case when it is applied as a cartridge-type ink tank (ink cartridge) which is mountable on a so-called serial scan type ink jet printing apparatus. 
     (Operating Position of Ink Tank (Liquid Container)) 
     Inkjet printing apparatuses have been expanded to business printers, consumer printers and the like. In general, these printing apparatuses are of a stationary type and are placed in a specified position at the time of printing. One of the reasons why a position of the printing apparatus when being operated is specified is the stabilization of the operational environment of the printing apparatus in order to achieve optimum printing. The operating position of the printing apparatus is specified, for example, with regard to the supplying condition of the ink from the ink tank to the printing head in the printing apparatus, the ejecting condition of the ink drops from the printing head, the flight condition of the ink, and the like. Accordingly, in general, the operating position of the ink jet printing apparatus is uniquely specified. 
     An ink tank (including an inkjet cartridge united with a printing head) which is used in such an ink jet printing apparatus of which the operating position is specified as described above is mounted in a specified position on an ink-tank mounting section of the ink jet printing apparatus. For example, in a serial scan ink jet printing apparatus, a mounted position (the position under operation condition) of the ink tank, which is of the type of being mounted on the carriage together with the printing head, is uniquely specified as a position of the ink tank at the time of being mounted on the carriage. Also, when the ink tank is of a stationary type that is placed in a mounting section located away from the printing head and is connected to the printing head via a tube or the like, a mounted position (the position under operation condition) of the ink tank is uniquely specified as a position of the ink tank at the time of being installed on the mounting portion. 
     In this manner, the mounted position (the position under operation condition) of an ink tank used in a typical ink jet printing apparatus is substantially uniquely specified. 
     For example, in a dominating ink jet printing apparatus comprising an ink tank mounted on a carriage, the ink tank is mounted with an ink supply port of the ink tank facing downward in the gravity direction, so that the ink is supplied from the ink supply port in the gravity direction. The mounted position of the ink tank in such an ink jet printing apparatus is defined as a position in which the ink supply port faces downward in the gravity direction. The mounted position is specified in a similar manner in another ink tank differing in an internal structure. An example of the ink tank differing in the internal structure includes a type of ink tank housing an ink absorber nearly with its entirety, and a type of ink tank having two divided spaces in which one space housing an ink absorber and the other space directly housing the ink. Also, in another type of ink tank, ink is housed directly in the entire interior of the ink tank. 
     In addition, there is a type of ink tank having an ink supply port placed on its side face. The mounted position of the ink tank of this type on the carriage is a position in which at least the ink can be supplied in the horizontal direction from the ink supply port. 
     Further, in a stationary type ink tank placed in a mounting section located away from the printing head, the ink tank is mounted in a position with the ink supply port facing downward in the gravity direction so that at least the ink can be supplied from the ink supply port in the gravity direction. In another stationary type ink tank, the ink tank is mounted in a position with the ink supply port facing in a direction at right angles to the gravity direction so that at least the ink can be supplied from the ink supply port in the horizontal direction. 
     In any type of ink tank, since, for example, the method for mounting the ink tank to a printing apparatus or the like is explained on the packaging, in an enclosed instruction manual or the like, the operating position of the ink tank can be specified. 
     Some of the ink jet printing apparatuses such as those called mobile printers utilize the convenience owing to being mobile and are in variously differing positions such as in a horizontal position or in a vertical position, for example. In the case of such a printing apparatus, the operating position of the ink tank also varies in accordance with the position of the printing apparatus. In the case of such a printing apparatus, the position specified under the main operation condition is defined as a basic operating position, and the position of the ink tank used when the printing apparatus is used in the basic operation position can be considered as the operating position of the ink tank. The ink tank may form part of an ink jet cartridge united with a printing head. 
     (Structure of Ink Jet Printing Apparatus) 
       FIG. 1  is an outside perspective view of a serial scan type ink jet printing apparatus in the example. The printing apparatus essentially comprises a printing apparatus body M 1000  for making printing on a printing medium, a sheet feeder M 3022  for feeding a printing medium into the printing apparatus, and an output tray  4  receiving the printed printing medium. 
       FIG. 2  is a perspective view illustrating the internal mechanism of the printing apparatus body M 1000 . The main internal mechanism of the printing apparatus body M 1000  is provided on and protected by a chassis M 3019 . M 4001  denotes a carriage which is movable to and from in a main scan direction indicated by the arrows X when mounted with a printing head cartridge (not shown). When a printing command is entered, one of the printing media loaded in the sheet feeder M 3022  is fed and conveyed to a site in which the printing head cartridge on the carriage M 4001  can print an image. Then, the printing apparatus repeats the print scanning operation of ejecting ink from the printing head of the printing head cartridge on the basis of the image data while the carriage M 4001  moves in the main scan direction, and the operation of using a convey unit to convey the printing medium in a sub scan direction indicated by the arrow Y. Thus, the image is sequentially formed on the printing medium. 
       FIG. 3  is a perspective view of a printing head cartridge H 1001  and ink cartridges  1  (liquid container) in the example. The ink cartridges  1  are cartridge-type ink tanks. The printing head cartridge H 1001  comprises a printing head H 1000  provided on one side which ejects ink drops from an ejection port, and the ink cartridges  1  are detachably mounted on the other side of the printing head cartridge H 1001  for supplying ink to the printing head (liquid ejecting head) H 1000 . The printing head cartridge H 1000  of the example is designed to allow the six color ink cartridges  1  to be independently mounted. The ink cartridges  1  may integrally comprise a printing head H 1000  to form a head cartridge. 
     The printing head H 1000  comprises an array of a plurality of fine printing elements each of which comprises a mechanism for ejecting ink. For example, in the structure including an electrothermal transducing element having a heating resistor (heater), in response to an ink-eject signal a voltage pulse is impressed to each electrothermal transducing element. As a result, the ink in the vicinity of the heating resistor is sharply heated to produce film boiling, the influence of which then causes the ink drops to be ejected from the ejection port. 
     (Structure of Entire Ink Cartridge) 
       FIG. 4  is an outside perspective view of the ink cartridge  1 . The ink cartridge  1  of the example is a container having an ink storage chamber formed therein, which comprises a container body  101 , a lid member  102  and a negative-pressure generating member. The ink cartridge  1  has an ink supply port  103  in the bottom for supplying ink to the printing head H 1000 . 
       FIG. 5  is an exploded perspective view of the ink cartridge  1 . The container body  101  of the ink cartridge  1  is formed of, for example, polypropylene, and a swinging member  200  is accommodated in the container body  101  for stirring the ink as shown in  FIG. 6 . An aperture in the top of the container body  101  is covered with the lid member  102 . The inside of the ink cartridge is divided into two spaces partitioned by a partition  113  and communicating with each other through a linking portion  114  which is formed beneath the partition  113 . One of the spaces is substantially sealed except for the linking portion  114  beneath the partition  113 , to form an ink storage chamber  111  capable of directly containing the ink. The other space houses a first and a second negative-pressure generating member  115 ,  116  for holding the ink to form a negative-pressure generating chamber  112  for applying a negative pressure to the ink. The negative-pressure generating chamber  112  has an atmospheric communication port  117  and the supply port  103  formed therein. The atmospheric communication port  117  is formed in the lid member  102  to introduce air into the ink cartridge  1  according to consumption of the ink. The supply port  103  is formed in the container body  101  and is capable of guiding the ink to the outside in order to supply the ink contained in the ink cartridge  1  to the printing head. The supply port  103  is provided with a meniscus producing member  104  for holding the ink. The meniscus of the ink occurring in the meniscus producing member  104  prevents bubbles from entering the ink cartridge  1  from the outside. 
     The first and the second negative-pressure generating member  115 ,  116  each are made of, for example, a polypropylene textile material and generates a capillary force. These negative-pressure generating members  115  and  116  are pressed into contact with each other. When the capillary force of the first negative-pressure generating member  115  is defined as P 1 , that of the second negative-pressure generating member  116  as P 2 , and that of the meniscus producing member  104  as P 3 , these capillary forces have the relationship of P 1 &lt;P 2 &lt;P 3 . 
     In the ink cartridge  1  thus structured, when the ink in the negative-pressure generating chamber  112  is consumed by the printing head, air is introduced from the atmospheric communication port  117  into the negative-pressure generating chamber  112 , then enters the ink storage chamber  111  through the linking portion  114  beneath the partition  113 . With the entry of air into the ink storage chamber  111 , the ink in the ink storage chamber  111  flows into the negative-pressure generating chamber  112  through the linking portion  114  beneath the partition  113 , and then is absorbed into the negative-pressure generating members  115  and  116 . Thus, a gas-liquid exchange is performed by the air and the ink via the linking portion  114 . 
     (Structure of Stirring Mechanism) 
       FIG. 6  is a perspective view for illustrating the mounting of the swinging member  200 , and  FIG. 7  is an enlarged perspective view of the swinging member  200 . 
     The swinging member  200  has a lower aperture  202  in a lower portion of the ink cartridge  1  in the gravity direction, and an upper aperture  203  formed in an upper portion of the ink cartridge  1 . An elliptical cross-section hollow portion  204  is formed between the apertures  202  and  203 . Accordingly, the swinging member  200  of the example is formed three-dimensionally in an elliptical cylindrical shape. Two recessed supports  201  are located on the long axis of the elliptical close to the lower aperture  202 . 
     The swinging member  200  in the example is formed of a stainless material and the inner face of the hollow portion  204  is subjected to hydrophilic treatment through, for example, sandblasting or the like in order to prevent bubbles from accumulating on the inner face. However, the material used to form the swinging member  200  is not limited to the stainless material but needs to have a larger specific gravity than that of the ink accommodated in the ink cartridge  1 . 
     As shown in  FIG. 6 , securing members  108  having projections  109  are provided on the inner wall of the ink storage chamber  111 . The projections  109  are fitted into the recessed supports  201  of the swinging member, whereby the supports  201  serve as fulcrums when the swinging member  200  swings. The swinging member  200  can swing about the supports  201  as the fulcrums. Since a portion close to the lower aperture  202  of the swinging member  200  in the example is swingably supported, the amount of displacement of the upper aperture  203  becomes larger than that of the lower aperture  202  when the swinging member  200  swings. 
     (Composition of Loaded Ink) 
     The ink used in the example is, for example, an ink including a pigment component (pigment ink). The pigment in the pigment ink may be, for example, a resin-dispersant-type pigment using a dispersant or an activator (resin dispersion pigment), or an activator-dispersion-type pigment. The pigment may be a microcapsule pigment allowed to disperse without a dispersant or the like by means of an increase in the dispersion properties of a water-insoluble colorant itself, or a self-dispersion-type pigment in which a hydrophilic group is introduced onto the surface of the pigment particles (self-dispersion pigment). Also, a pigment modified by chemically bonding an organic group including polymer molecules to the surfaces of the pigment particles (polymer-bonded self-dispersion pigment) may be used. It goes without saying that pigments differing in dispersion method may be used in combination. The pigments usable in the present invention are not specially limited. 
     Table 1 below shows two exemplary kinds (pigment inks  1 ,  2 ) of compositions of pigment ink used in the example. However, the present invention is not limited to these compositions. 
     The pigment ink used in the example has a mixing ratio shown in the following table 1, in which a self-dispersion pigment is used for a pigment dispersion  1  and a resin dispersion pigment is used for a pigment dispersion  2 . For each of the pigment dispersions  1  and  2 , a fluid dispersion is prepared by adding water to a pigment so as to disperse the pigment such that the pigment concentration reaches 10 mass %. The preparation of each solvent is shown in the following table 1. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Ink composition in the example 
               
            
           
           
               
               
               
            
               
                   
                 Ink Preparation (mass %) 
                   
               
            
           
           
               
               
               
            
               
                   
                 1 
                 2 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Pigment dispersion 1 
                 50 
                   
               
               
                   
                 Pigment dispersion 2 
                   
                 50 
               
               
                   
                 Glycerin 
                 5 
                 5 
               
               
                   
                 Polyethyleneglycol 600 
                 15 
                 15 
               
               
                   
                 2-pyrrolidone 
                 5 
                 5 
               
               
                   
                 Acetylene glycol EO adduct 
                 0.1 
                 0.1 
               
               
                   
                 Pure water 
                 24.9 
                 24.9 
               
               
                   
                   
               
            
           
         
       
     
     The pigment ink filled into the ink cartridge has desirably a smaller specific gravity than that of the swinging member. The swinging member in the example, which is formed of a stainless material, has a specific gravity of 8.0 g/cm 3 , and the specific gravity of the pigment ink ranges from 1.0 g/cm 3  to 1.1 g/cm 3 , which is thus smaller than that of the swinging member. 
     (Modified Example of Stirring Mechanism) 
     The stirring mechanism is not limited to the foregoing, and the cross-section of the hollow portion  204  is not limited to an elliptical shape and may be a circular shape, a rectangular shape or the like. The support  201  may be shaped so as to extend through the swinging member  200  rather than the recessed shape described above. In addition, the location of the support  201  is not necessarily determined to be on the long axis of the hollow portion  204  as described above. 
       FIG. 8  is a view illustrating a modified example of the stirring mechanism. 
     A stirring member  150  in the example is shaped three-dimensionally such that the shape of each of apertures  152  and  153  and the cross-section of a hollow portion  154  are rectangular. A support  151  is provided in the lower portion of the stirring member  150 , and has two sides engaged with projections  170  provided on the inner wall of an ink storage chamber  161 . Thus, the swinging member  150  is supported by the projections  170  in such a manner as to swing about the projections  170  as fulcrums. The head of each projection  170  has a greater diameter so as to prevent the support  151  of the swinging member  150  from coming away. The projections  170  serve as the swinging fulcrums of the swinging member  150  and also permit the swinging member  150  to slide in the axis direction of the projection  170 . 
     The inside of the ink cartridge  1  is divided into an ink storage chamber  161  and a negative-pressure generating chamber  162  by a partition  163  having a linking portion  164  at the lower end. The negative-pressure generating chamber  162  houses a negative-pressure generating member  166  that is made of a polypropylene textile material and generates a capillary force. When the ink is consumed through a supply port  131  by the printing head, the air introduced through an atmospheric communication port  137  into the negative-pressure chamber  162  and the ink in the ink storage chamber  161  are exchanged through the linking portion  164 . 
     (Method for Loading Ink) 
       FIG. 9A ,  FIG. 9B  and  FIG. 9C  are sectional elevation views each showing the aforementioned ink cartridge for illustrating a method for loading ink into the ink cartridge, which are taken along the IX-IX line in  FIG. 4 . 
     After the ink in the ink cartridge has been consumed or when the ink cartridge is initially loaded with ink, an infusion needle  180  is inserted into the ink cartridge  1  as shown in  FIG. 9A . The infusion needle  180  is a needle-shaped hollow member having an ink passageway formed therein, and having a base end (the upper end in  FIG. 9A ) connected to an ink supply source which is not shown, and a leading open end (the lower end in  FIG. 9A ). In order to insert the infusion needle  180  into the ink cartridge  1 , a hole  102 A is drilled in the lid member  102 , then the infusion needle  180  is inserted into the hole  102  from above in the gravity direction. Since the infusion needle  180  of the example has a sharply-pointed leading end, the leading end can also be plunged into the ink cartridge  1  so as to form the hole  102 A. The method for forming the hole  102 A is not limited to the method of using the infusion needle  180  or another means to form a hole when the ink is loaded as described above. For example, a hole may be drilled in advance in the ink cartridge  1  before the ink is loaded through the infusion needle  180 . In this case, the pre-formed hole is unsealed at the time of loading the ink, and then the infusion needle  180  can be inserted through the hole. An important point is that a site enabling the insertion of the infusion needle  180  exists on the ink cartridge  1 , and the location of the site is a location in which the ink can be loaded into the ink cartridge  1  as described later. 
     In the case of this example, the infusion needle  180  is inserted into the ink cartridge  1  so as to be located inside the hollow portion  204  of the swinging member  200 , such that the leading end of the infusion needle  180  is located close to the bottom of the hollow portion  204 . 
     After the infusion needle  180  has been inserted in this manner, the ink  120  is loaded through the infusion needle  180  into the ink cartridge  1 .  FIG. 9B  shows a middle stage in the ink loading process. Then, when as shown in  FIG. 9C , the hollow portion  204  of the swinging member  200  is filled with the ink  120  and the entire swinging member  200  is submerged in the ink  120 , the ink loading process is complete. Then, the infusion needle  180  is removed and the hole  102 A is sealed. 
     In the ink loading process, the ink  120  is loaded relatively quickly and smoothly so as to prevent the occurrence of bubbles. If the ink  120  includes a material causing the occurrence of bubbles such as a surface-active agent, bubbles easily occur. To avoid this, the ink  120  is loaded smoothly not to produce a vortex. 
     If bubbles occur in the ink  120  and adhere to the wall face of the ink storage chamber  161  and/or the swinging member  200 , this may possibly result in the blocking of the ink flow to impair the full efficacy of the stirring when the ink is stirred through the stirring operation which will be described later. In particular, when bubbles adhere to the inner face of the swinging member  200  forming the hollow portion  204  (hereinafter referred to as “the inner face of the swinging member”), the bubbles may block the flow of the ink in the hollow portion  204  in the stirring operation which will be described later. Depending upon the relationship between the inner diameter of the hollow portion  204  and the size of the bubbles adhering to the inner face of the swinging member  200 , the movement of the ink in the hollow portion  204 , which will be described later, may possibly not occur. Accordingly, it is important to load the ink  120  in such a manner as to prevent bubbles from occurring, and in particular it is important to prevent the adhesion of bubbles to the inner face of the swinging member  200 . Smoothly loading the ink so as to restrain bubbles from occurring or remaining is made possible by introducing ink through the infusion needle  180  from a site close to the bottom of the ink storage chamber  161  and from the inside of the hollow portion  204  as described in the example. 
     The ink loaded from the infusion needle  180  produces a flow traveling upward in the hollow portion  204  and a flow traveling toward the inside of the ink storage chamber  161  from the hollow portion  204  through the lower aperture  202 . In the example, because the infusion needle  180  is located inside the hollow portion  204 , the gap between the inner face of the swinging member  200  and the infusion needle  180  becomes narrow, which increases the velocity of the ink moving in the hollow portion  204 . For this reason, when bubbles occur in the hollow portion  204 , they can be removed from the hollow portion  204 . 
     In the ink loading process, the gap between the infusion needle  180  and the hole  102 A serves as an air vent to let the air in the ink storage chamber  161  escape to the outside. If bubbles occur in the ink loading process, the bubbles can be removed from the hole  201 A to the outside by loading the ink  120  in such a manner as to overflow from the hole  201 A. 
     In order to prevent the bubbles from remaining on the inner face of the swinging member  200 , the inner face is desirably subjected to hydrophilic treatment. If the swinging member  200  is formed of stainless steel (SUS material), the inner face is desirably ground by a sandblasting technique or the like to restrain the adhesion of bubbles. If the swinging member  200  is formed of a resin material, the inner face is desirably subjected to hydrophilic treatment. The method for performing the hydrophilic treatment on the resin material may be chosen at will, and for example, a method as described in Japanese Patent Laid-Open No. 2001-220457 may be used. 
     The ink cartridge  1  is loaded with the ink  120  until the swinging member  200  is submerged in the ink, that is, until the liquid level of the ink extends above the upper aperture  203  in the gravity direction. Loading the ink  120  up to above the upper aperture  203  in the gravity direction means that the ink  120  is loaded into the ink cartridge  1  placed in a predetermined position up to a higher level than the upper aperture  203  in the gravity direction. The predetermined position refers to the mounted position (operating position) when the ink cartridge  1  is installed on the printing apparatus body M 1000  which is placed on a plane forming approximately a right angles with the gravity direction (an approximately horizontal plane). The ink  120  is loaded in an amount to reach or exceed a level for submerging the upper aperture  203  of the swinging member  200  in the ink when the ink cartridge  1  is in such a mounted position. It is essential that the ink  120  can be loaded to at least a level which allows the swinging member  200  to exercise its later-described stirring function when the ink cartridge is operated. 
     In the embodiment, in addition to the swinging movement of the swinging member  200  as described later, the ink flow traveling through the hollow portion  204  of the swinging member  200  is effectively used to stir the ink. For this end, the amount of loading the ink  120  is set to a level at least allowing it to be stirred by the swinging movement of the swinging member  200 , preferably, a level inducing an ink flow traveling through the hollow portion  204  of the swinging member  200 . For inducing such an ink flow, a desirable loading amount is equal to or greater than a level for submerging the upper aperture  203  in the ink  120  (a level for completely submerging the hollow portion  204  in the ink  120 ). However, if a loading amount of ink less than the above level can induce the occurrence of an ink flow in the hollow portion  204  or the swinging movement of the swinging member involving the stirring of the ink, the loading amount may be a level such as to submerge at least a part of the hollowing portion  204  in the ink  120 . 
     In the example, the position of the ink cartridge  1  when the ink is loaded (ink-loaded position) is the same as the mounted position of the ink cartridge  1  in operation. However, the ink-loaded position is not necessarily the same as the mounted position. For the ink-loaded position of the ink cartridge  1 , one effective for reducing the amount of bubbles occurring and/or remaining can be selected in accordance with the size and/or shape of the ink cartridge  1  and/or the swinging member  200 . In addition, the ink-loaded position is not necessarily limited to the one, and may be continuously or gradually changed in step with the process of loading the ink. For example, at the time of starting loading the ink, the ink-loaded position may be set to be a position inclined with respect to the mounted position (inclined position). Then, the ink-loaded position may be changed in step with the process of loading the ink, such that the ink cartridge  1  comes into an inverted position at the end of loading the ink. The importance is that the ink-loaded position can allow the ink to be loaded so as to reduce the amount of bubbles occurring and/or remaining. The positional relationship between the ink cartridge  1  and the infusion needle  180  can be maintained by changing the position of the infusion needle  180  in synchronization with the position of the ink cartridge  1 . 
     (Other Examples of Method of Loading Ink) 
     In the case of the method of loading ink illustrated in  FIGS. 9A ,  9 B and  9 C, while fixing the infusion needle  180  located in the ink cartridge  1 , the ink is loaded through the infusion needle  180 . However, as illustrated in  FIG. 10A ,  FIG. 10B  and  FIG. 10C , the ink may be loaded through the infusion needle  180  while moving the infusion needle  180  gradually upward in step with the rise in the liquid level of the ink  120 . In this manner, by moving the infusion needle  180  upward while the ink  120  is being loaded into the hollow portion  204 , a reduction in the amount of bubbles remaining in the hollow portion  204  is made possible. 
     As illustrated in  FIG. 11A ,  FIG. 11B  and  FIG. 11C , the infusion needle  180  may be inserted into a location outside the hollow portion  204  of the swinging member  200 . In this case, the hollow portion  204  is loaded with ink from the outside of the swinging member  200 . It is important again in this case to disallow bubble existing in the hollow portion  204 . For this end, the inside of the swinging member  200  is desirably subjected to hydrophilic treatment. Also, in this example, the ink may be loaded through the infusion needle  180  while moving the infusion needle  180  gradually upward in step with the rise in the liquid level of the ink  120 , as in the case of  FIGS. 10A ,  10 B and  10 C. 
     (Operation and Effect of Stirring Mechanism) 
       FIG. 12A  to  FIG. 12D  are schematic structural diagrams each showing the principal part of the printing apparatus for illustrating the operation of the carriage in  FIG. 2 .  FIG. 13A  to  FIG. 13H  are illustrative views each showing the operation of the swinging member  200  and an ink flow occurring in the hollow portion  204  of the swinging member  200  in the example, which represent the condition of stirring a high-pigment-concentration portion of the ink settling on the bottom of the ink cartridge  1 .  FIG. 13A  to  FIG. 13H  respectively correspond to a sectional view taken along the IX-IX line in  FIG. 4 . 
     The operation of the carriage M 4001  mounted with the ink cartridge  1  which is the liquid container will be described first with reference to  FIG. 12A  to  FIG. 12D . 
     The carriage M 4001  moves from its home position shown in  FIG. 12A  along a carriage shaft M 3020  provided on the chassis of the printing apparatus M 1000  in the direction indicated by the arrow X 2  (see  FIG. 12B ). Then, the carriage M 4001  is moved by a distance corresponding to the printing width of the printing medium or by a distance required for operating the swinging member  200 , to reach a point shown in  FIG. 12C . Then, the moving direction of the carriage M 4001  is reversed at the point, so that the carriage M 4001  is then moved from there in the direction indicated with the arrow X 1  (see  FIG. 12D ). The moving direction of the carriage M 4001  is reversed again at the point shown in  FIG. 12A , and then the carriage M 4001  repeats the reciprocating movement in the directions indicated with the arrows X times as required for printing. When the moving direction is reversed, the carriage M 4001  is decelerated, stopped and accelerated in the reversed direction. As described above, prior to the reciprocating movement of the carriage M 4001  for printing, as illustrated in  FIG. 12B  to  FIG. 12D , the carriage M 4001  makes at least one return trip in the example. As a result, it is possible to stir the ink prior to the printing operation as described later. 
     Next, the operation of the swinging member  200  of the ink cartridge  1  along with the reciprocating movement of the carriage M 4001  will be described with reference to  FIG. 13A  to  FIG. 13H . The ink storage chamber  111  shown in these figures is in the condition of being loaded with the ink. 
       FIG. 13A  shows the state of the carriage M 4001  which is at rest in its home position as shown in  FIG. 12A , in which the swinging member  200  in the ink storage chamber  111  is at rest while the outer side of the upper aperture  203  is in contact with the inner wall of the ink storage chamber  111 . This state is held from the time when the carriage M 4001  starts moving from the point shown in  FIG. 12A  until when it moves at the constant speed in the direction X 2  as shown in  FIG. 12B . 
       FIG. 13B  to  FIG. 13E  illustrate the state either when the carriage M 4001  reaches the point shown in  FIG. 12C  and then its moving direction is reversed from the direction X 2  to the direction X 1  or when the carriage M 4001  is moving in the direction X 1  after the reverse of the moving direction as shown in  FIG. 12D . When the moving direction of the carriage M 4001  is reversed, an inertial force acts on the ink cartridge  1 . When the inertial force acts in the direction indicated by the arrow X 2 , that is, when the moving direction of the carriage M 4001  is reversed from the direction X 2  to the direction X 1 , the swinging member  200  swings about the support  201  as a fulcrum in the direction indicated with the arrow S 2  in the order illustrated in  FIG. 13B  to  FIG. 13E . Then, as shown in  FIG. 13E , the outer side of upper aperture  203  of the swinging member  200  comes into contact with the opposite inner wall of the ink storage chamber  111  (the inner wall opposite to the inner wall which is in contact with the outer side of the upper aperture  203  in  FIG. 13A ), thereby stopping the swinging motion of the swinging member  200  in the direction S 2 . The swinging member  200  is kept in the state shown in  FIG. 13E  from the time when the carriage M 4001  starts moving from the point of  FIG. 12C  to the time when it moves at a constant speed in the direction X 2  as shown in  FIG. 12D . 
       FIG. 13F  and  FIG. 13G  illustrate the sate either when the carriage M 4001  moves in the direction X 1  to reach the point of  FIG. 12A  and then reverses the moving direction to the direction X 2  or when the carriage M 4001  is moving in the direction X 2  after the reverse of the moving direction as shown in  FIG. 12B . When an inertial force associated with the reverse of the moving direction of the carriage M 4001  acts in the direction indicated by the arrow X 1 , the swinging member  200  swings about the support  201  as the fulcrum in the direction indicated by the arrow S 1 , in the order shown in  FIG. 13F  and  FIG. 13G . Then, the carriage M 4001  moves again in the direction X 1 , whereby the swinging member  200  swings in the direction S 2  as shown in  FIG. 13H . 
     The swinging member  200  repeats the reciprocating movement as described above while the carriage M 4001  repeats the reciprocating movement. 
     Next, a description with reference to  FIG. 13A  to  FIG. 13H  will given of the conditions of an ink flow occurring in the hollow portion  204  of the swinging member  200  in association with the reciprocating movement of the swinging member  200  and of the ink stirred. 
     The swinging member  200  starts swinging in the direction S 2 , and then a centrifugal force generated by the swinging movement of the swinging member  200  produces a flow T 2  of the ink existing in the hollow portion  204  to go out from the upper aperture  203  as shown in  FIG. 13B . At the same time, a flow T 1  going into the hollow portion  204  occurs in the ink existing on the bottom of the ink tank around the lower aperture  202 . With the continuation of the swinging movement of the swinging member  200 , the centrifugal force acting on the ink in the hollow portion  204  causes the ink to flow through the hollow portion  204  to outflow from the upper aperture  203 , as shown in from  FIG. 13B  to  FIG. 13D . 
     As shown in  FIG. 13E , the swinging movement of the swinging member  200  in the direction S 2  is stopped, whereupon an inertial force generated by the stop of the swinging movement of the swinging member  200  acts on the ink in the hollow portion  204  so as to further accelerate the ink flow in the hollow portion  204 . The portion of the ink, which has passed through the hollow portion  204  outflows from the upper aperture  203 , becomes a flow T 3  which then diffuses into a low-pigment-concentration portion of the ink, as shown in  FIG. 13F  and  FIG. 13G . The ink in the ink storage chamber  111  is further stirred by a flow T 4  of the ink bouncing off the inner face of the ink storage chamber  111 . 
     The high-pigment-concentration portion of the ink, which has gone out from the upper aperture  203 , moves down, due to the flows T 2 , T 3 , T 4  and the gravity, to a level where the swinging member  200  is provided. Then, as shown in  FIG. 13H , as the swinging member  200  swings, the relative distance between the outer wall of the swinging member  200  and the inner wall of the ink storage chamber  111  variously increases and decreases, thereby producing a mechanical flow T 5  between these outer and inner walls. The flow T 5  further stirs the ink in the ink storage chamber  111 . 
     The operation as described above is carried out once or a plurality of times, whereby the ink in the ink storage chamber  111  is stirred by being moved upward from a lower portion to a higher portion by the flows T 1  to T 5 . This results in even stir of the ink in the entire ink storage chamber  111  including the portion of the ink existing in the upper portion of the ink storage chamber  111 . In short, it is possible to effectively stir the ink in the ink cartridge  1 . 
     The swinging movement of the swinging member  200  is desirably carried out continuously. The continuous swinging movement can enhance a propulsive force required for stirring the ink in the ink storage chamber  111  toward the upper portion from the lower portion. In other words, it is possible to enhance the pumping effect producing a flow T 2  of the ink in the hollow portion  204  of the swinging member  200 . 
     In the example, the ink is stirred while the swinging member  200  is reversed in the swinging direction. However, the swinging direction is not necessarily reversed. What is required is that the inertial force can apply a propulsive force to the ink so that the pigment particles located on the bottom of the ink storage chamber travel through the hollow portion of the swinging member so as to rise up toward the upper portion of the ink cartridge. Accordingly, the swinging member may be stopped after moving in one direction. Also, even when the ink in the ink storage chamber  111  is decreased to lower the liquid level, as long as the hollow portion  204  of the swinging member  200  is submerged in the ink, it is possible to offer the ink stirring effects described above. 
     (Experimental Results) 
     For verifying the ink stirring effects, the inventors poured pigment ink into an ink cartridge until the hollow portion of the swinging member was submerged in the ink. Then, the ink cartridge was heated and maintained for the purpose of verifying the phenomenon of the pigment ink settling out in a short time. The ink cartridge was maintained at a temperature of 60° C. for 90 days. The ink cartridge after thus heated and maintained was placed in environment at ordinary temperatures to reduce the temperature. Then, without swinging the swinging member, a sample was obtained from the portion of the pigment ink located in a lower portion of the ink cartridge in the gravity direction. In another ink cartridge which has been heated and maintained as in the above case, the swinging member was first swung, and then a sample was obtained from the portion of the pigment ink located in the lower portion of the ink cartridge in the gravity direction. Then, the pigment concentrations of the pigment ink samples taken from the two ink cartridges were compared. 
     The following table 2 shows the pigment concentration of the pigment ink sample obtained from the heated and maintained ink cartridge without stirring the ink, and the pigment concentration of the pigment ink sample obtained from the heated and maintained ink cartridge after the ink had been stirred as described above. Table 2 shows the pigment concentrations indicated by absolute values when the pigment concentrations before the heating and maintaining process are defined as 100. As shown in Table 2, the pigment concentration when the ink has not been stirred is 170, and the pigment concentration when the ink has been stirred was less than 120. From this fact, it can be confirmed that performing the foregoing stirring method makes the pigment concentration of the ink closer to the pigment concentration measured before the heating and maintaining process. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Results of verification of the stirring by the 
               
               
                 swinging member 
               
            
           
           
               
               
            
               
                   
                 Pigment Concentration 
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                   
                 Non-stir 
                 170 
               
               
                   
                 Stirred 
                 less than 120 
               
               
                   
                   
               
               
                   
                 Heating and maintaining 60° C., 90 days 
               
               
                   
                 Pigment Concentration before the heating and maintaining process is defined as 100 
               
            
           
         
       
     
     In the embodiment, the swinging member is designed to, upon swinging, make the moving velocity of the aperture forming in the lower portion slower than that of the aperture forming in the upper portion. Because of this, a flow of the ink from the lower layer in the ink cartridge toward the upper layer is produced. This ink flow induces convective mixing of the thick ink and the thin ink together in the ink cartridge to effectively stir the ink. This makes it possible to prevent the occurrence of a difference in density on the printed image between an initial stage and a later stage of the printing operation of the ink cartridge, and to prevent color balance from being lost when a plurality of color inks are used. 
     In any of the structures, a swinging member having a hollow portion is provided in a liquid container and is swung to guide the liquid in the hollow portion such that the liquid flows into the hollow portion from one end of the hollow portion and then flows out from the other end of the hollow portion. As a result, it is possible to produce a liquid flow effective for stirring the liquid in the liquid container. 
     As described in the embodiment, when a swinging fulcrum is provided in the vicinity of the aperture in the lower portion of the swinging member in the vertical direction, pigment particles apt to settle to the lower portion of the ink storage chamber can easily and reliably rise up to the upper portion. Specifically, by setting the swinging fulcrum in a location below the central portion of the swinging member in the vertical direction, the ink introduced from the aperture located in a lower portion in the gravity direction can be guided to the outside from the aperture located in an upper portion in the gravity direction. That is, it is possible to stir the ink by guiding the ink through the hollow portion from the bottom toward the above in the gravity direction. As a result, it is possible to effectively stir the entire liquid such as ink contained in the liquid container to reduce the concentration gradient of the liquid. 
     Second Embodiment 
     Next, a second embodiment of the present invention will be described. A liquid container in this embodiment is an example of the case when it is applied as an ink cartridge which is mountable on the printing apparatus illustrated in  FIG. 1  to  FIG. 3 . In the ink cartridge of the embodiment, the volume of the ink storage chamber does not decrease even when the ink is consumed. In other words, the amount of ink in the ink storage chamber alone is decreased without a reduction in the volume of the ink storage chamber. 
     (Structure of Entire Ink Tank) 
       FIG. 14  is an exploded perspective view of an ink cartridge  3  of the example. The ink cartridge  3  is a container having an ink storage chamber  320  formed therein, which mainly comprises a container body  351  and a lid member  352 . The ink cartridge  3  has an ink supply port  355  formed in the bottom for supplying the ink to the printing head. 
     The container body  351  is formed of, for example, polypropylene, and a swinging member  300  is accommodated in the container body  351  as a stirring member for stirring the ink. An opening of the container body  351  is covered with the lid member  352 . Projections  309  are provided in the container body  351  for supporting the swinging member  300 , and a meniscus producing member  354  is provided in the ink supply port  355 . The meniscus producing member  354  and the inside of the container body  351  communicate with each other through an ink flow path, so that ink can be applied from the ink storage chamber  320  in the container body  351  to the printing head. An ink meniscus is produced in the meniscus producing member  354 , to prevent bubbles from entering the container body  351  from the outside. The meniscus producing member  354  is secured by being pressed from the outside by a pressing member  353 . 
     The container body  351  has an atmospheric communication port  360  for introducing air into the ink storage chamber  320 . The ink storage chamber  320  is sealed not to allow air to enter and exit from the ink storage chamber  320  except for through the atmospheric communication port  360 . A small tube  361 , which is hollow, has one end connected to the atmospheric communication port  360  and the other end open to a lower portion of the ink storage chamber  320  near the bottom in the gravity direction. This structure allows air to enter the ink storage chamber  320  from the other end of the small tube  361  as the ink in the ink storage chamber  360  is consumed. A negative pressure is developed in the ink storage chamber  320  by a pressure reduction in the ink storage chamber  320  in association with the ink consumption and the ink meniscus in the small tube  361 . 
     (Structure of Stirring Mechanism) 
       FIG. 15  is a perspective view for illustrating the mounting of the swinging member  300 , and  FIG. 16  is an enlarged perspective view of the swinging member  300 . 
     A support  301  of the swinging member  300  has two sides engaged with projections  309  provided on the inner wall of the container body  351  in order to support the swinging member  300 . The projections  309  serve fulcrums when the swinging member  300  swings. In the swinging member  300  a lower aperture  302  is formed in a lower portion in the gravity direction and an upper aperture  303  is formed in an upper portion, and a hollow portion  304  is formed between the apertures  302  and  303 . The upper aperture  303  is vertically inclined with respect to the hollow portion  304  extending in the up-down direction. Such a swinging member  300  is shape three-dimensionally to form the hollow portion  304  in its interior. 
     The swinging member  300  in the example is supported on the projections  309  by the support  301  provided near the lower aperture  302 . For this reason, when the swinging member  300  swings as shown in  FIG. 18C , the amount of displacement at the upper aperture  303  is larger than that at the lower aperture  302 . The swinging member  300  is formed of a stainless material. Note that the material used to form the swinging member  300  is not limited to the stainless material but needs to have a larger specific gravity than that of the ink contained in the ink storage chamber  320 . 
     (Method for Loading Ink) 
       FIG. 17A  and  FIG. 17B  are side-sectional elevation views each showing the aforementioned ink cartridge  3  for illustrating a method for loading ink into the ink cartridge  3  of the example, which correspond to the sectional views taken along the XVII-XVII line in  FIG. 14 . 
     As in the case of the foregoing first embodiment, after the ink in the ink cartridge has been consumed or when the ink cartridge is initially loaded with ink, the infusion needle  180  is inserted into the ink cartridge  3  as shown in  FIG. 17A . 
     In the case of the example, the infusion needle  180  is inserted into the ink cartridge  3  in such a manner as to be located outside the hollow portion  304  of the swinging member  300 , such that the leading end of the infusion needle  180  is located close to the bottom of the ink storage chamber  320 . 
     After the infusion needle  180  has been thus inserted as in the case of the aforementioned illustration in  FIGS. 11A ,  11 B and  11 C, the ink  120  is loaded through the infusion needle  180  into the ink cartridge  3 . Then, as shown in  FIG. 17B , the ink  120  is loaded until at least a part of the upper aperture  303  of the swinging member  300  is submerged in the ink. Then, the infusion needle  180  is removed and a hole  351 A is sealed. 
     In the ink loading process, the ink  120  is loaded relatively quickly and smoothly so as to prevent the occurrence of bubbles, as in the case of the aforementioned embodiment. If the ink  120  includes a material causing the occurrence of bubbles such as a surface-active agent, bubbles easily occur. To avoid this, the ink  120  is loaded smoothly not to produce a vortex. 
     The ink cartridge  3  is loaded with the ink  120  until at least a part of the upper aperture  303  of the swinging member  300  is submerged in the ink. Loading the ink  120  until at leas a part of the upper aperture  303  is submerged in the ink means that the ink  120  is loaded into the ink cartridge  3  in a predetermined position until at leas a part of the upper aperture  303  is submerged in the ink. The predetermined position refers to the mounted position (operating position) when the ink cartridge  3  is installed on the printing apparatus body M 1000  which is placed on a plane forming approximately a right angles with the gravity direction (an approximately horizontal plane). The ink  120  is loaded in an amount to reach or exceed a level for submerging at leas a part of the upper aperture  303  of the swinging member  300  in the ink when the ink cartridge  3  is in such a mounted position. It is essential that the ink  120  can be loaded to at least a level which allows the swinging member  300  to exercise its later-described stirring function when the ink cartridge  3  is operated. 
     As in the case of the foregoing embodiment, what is required is that the ink cartridge is loaded with the ink  120  to a level allowing, at least, the swinging member  300  to exercise its stirring function. Also, the ink cartridge when the ink is loaded is required to be in a position allowing the ink to be loaded in such a manner as to reduce the amount of bubbles occurring and/or remaining. 
     As in the case of the illustration of  FIGS. 10A ,  10 B and  10 C, in the example, the ink may be loaded through the infusion needle  180  while moving the infusion needle  180  gradually upward in step with the rise in the liquid level of the ink  120 . As in the case of the illustration of  FIGS. 9A ,  9 B and  9 C, if the infusion needle  180  is inserted into the hollow portion  304  of the swinging member  300 , the occurrence of bubbles can be more effectively prevented. 
     (Operation and Effect of Stirring Mechanism) 
       FIG. 18A  to  FIG. 18C  are side-sectional views each showing the ink cartridge  3  for illustrating the operation of the swinging member  300  in the embodiment. 
       FIG. 18A  illustrates a first mode of the swinging member  300 . The carriage M 4001  reciprocates in the main scan direction (the direction indicated by the arrow X) in a range corresponding to the printing width of the printing medium. Accordingly, when the moving direction is reversed, the carriage M 4001  is decelerated, stopped and accelerated in the reversed direction. At this point, an inertial force acts on the ink cartridge  3 . When the inertial force acts in the direction indicated by the arrow X 1 , that is, when the moving direction of the carriage M 4001  is reversed from the direction of the arrow X 1  to the direction of the arrow X 2 , the swinging member  300  pivots about the support  301  in the direction indicated by the arrow E 1 , as shown in  FIG. 18A . At this point, the outer side of the upper aperture  303  produces displacement in the direction coming into contact with the inner wall of the container body  351  on which the projections  309  are provided. When the inertial force acts in the direction X 1  as described above, this state is referred to as a first mode. After the moving direction of the carriage M 4001  has been reversed from the direction X 1  to the direction X 2 , when the carriage M 4001  moves at the constant speed in the direction X 2 , the inertial force becomes inoperative. As a result, the swinging member  300  is left in the first mode. 
       FIG. 18B  illustrates a second mode of the swinging member  300 . Contrary to the first mode, in the second mode, when the inertial force acts in the direction X 2 , that is, when the moving direction of the carriage M 4001  is reversed from the direction X 2  to the direction X 1 , the swinging member  300  pivots about the support  301  in the direction indicated by the arrow E 2 , as shown in  FIG. 18B . At this point, the outer side of the upper aperture  303  produces displacement in the direction coming into contact with the lid member  352 . When the inertial force acts in the direction X 2  as described above, this state is referred to as the second mode. After the moving direction of the carriage M 4001  has been reversed from the direction X 2  to the direction X 1 , when the carriage M 4001  moves at the constant speed in the direction X 1 , the inertial force becomes inoperative. As a result, the swinging member  300  is left in the second mode. 
     Because the carriage M 4001  repeats the reciprocating movement in step with the printing operation or the operation of stirring the ink, the swinging member  300  is repeatedly put into the first mode and the second mode shown in  FIGS. 18A and 18B  to stir the ink in the ink storage chamber  320 . 
       FIG. 18C  illustrates the direction of displacement and the amount of displacement of the apertures  302  and  303  when the swinging member  300  swings, and the flow of the ink. 
     As described above, the amount of displacement X ( 303 ) of the upper aperture  303  produced when the swinging member  300  swings is larger than the amount of displacement X ( 302 ) of the lower aperture  302 . If at least a part of the upper aperture  303 , the lower aperture  302  and the hollow portion  304  are submerged in the ink, ink flows F 1  and F 2  are produced from the lower aperture  302  through the hollow portion  304  toward the upper aperture  303 , and also an ink flow F 3  associated with the flows F 1  and F 2  is produced. These ink flows can be utilized to stir the ink in the ink storage chamber  320 . 
     Third Embodiment 
     Next, a third embodiment of the present invention will be described. A liquid container in this embodiment is an example of the case when it is applied as an ink cartridge which is mountable on the printing apparatus illustrated in  FIG. 1  to  FIG. 3 . In the ink cartridge of the embodiment, the volume of an ink storage chamber does not decrease even when the ink is consumed. In other words, the amount of ink in the ink storage chamber alone is decreased without a reduction in the volume of the ink storage chamber. 
     (Structure of Entire Ink Cartridge) 
       FIG. 19  is an exploded perspective view of an ink cartridge of the example. The ink cartridge of the example differs in the structure of a swinging member provided therein from the ink cartridge described in  FIG. 14 , and has the same structure of other components as that of the ink cartridge of  FIG. 14 . 
     (Structure of Stirring Mechanism) 
     A support  401  of a swinging member  400  provided in the ink cartridge of the example has two sides engaged with projections  309  provided on the inner wall of the container body  351  in order to support the swinging member  400 . The projections  309  serve fulcrums when the swinging member  400  swings. In the swinging member  400  a lower aperture  402  is formed in a lower portion in the gravity direction and an upper aperture  403  is formed in an upper portion, and a hollow portion  404  formed between the apertures  402  and  403 . An intermediate aperture  410  is provided between the lower aperture  402  and the upper aperture  403  and communicates with the hollow portion  404 . Such a swinging member  400  is shape three-dimensionally to form the hollow portion  404  in its interior. 
     (Method for Loading Ink) 
       FIG. 20A  and  FIG. 20B  are side-sectional elevation views each showing the ink cartridge for illustrating a method for loading ink into the ink cartridge of the example, which correspond to the sectional views taken along the XX-XX line in  FIG. 19 . 
     As in the case of the foregoing embodiments, after the ink in the ink cartridge has been consumed or when the ink cartridge is initially loaded with ink, the infusion needle  180  is inserted into the ink cartridge as shown in  FIG. 20A . For the insertion of the infusion needle  180  into the ink cartridge, the hole  351 A is drilled in the container body  351 , and then the infusion needle  180  is inserted into the hole  351 A from above in the gravity direction. The method of inserting the infusion needle  180  is not limited to the method of drilling the hole  351 A in the ink cartridge and then inserting the infusion needle  180  as described above. For example, a hole provided in an ink cartridge in advance may be unsealed and then the infusion needle  180  may be inserted through the hole into the ink cartridge. 
     In the case of the example, the infusion needle  180  is inserted into the ink cartridge in such a manner as to be located outside the hollow portion  404  of the swinging member  400 , such that the leading end of the infusion needle  180  is located close to the bottom of the ink storage chamber  320 . 
     After the infusion needle  180  has been thus inserted as in the case of the aforementioned illustration in  FIGS. 17A and 17B , the ink  120  is loaded through the infusion needle  180  into the ink cartridge. Then, as shown in  FIG. 20B , the ink  120  is loaded until at least a part of the intermediate aperture  410  is submerged in the ink. Then, the infusion needle  180  is removed and the hole  351 A is sealed. 
     In the ink loading process, the ink  120  is loaded relatively quickly and smoothly so as to prevent the occurrence of bubbles, as in the case of the aforementioned embodiment. If the ink  120  includes a material causing the occurrence of bubbles such as a surface-active agent, bubbles easily occur. To avoid this, the ink  120  is loaded smoothly not to produce a vortex. 
     As in the case of the foregoing embodiment, what is required is that the ink cartridge is loaded with the ink  120  to a level allowing, at least, the swinging member  300  to exercise its stirring function. Also, the ink cartridge when the ink is loaded is required to be in a position allowing the ink to be loaded in such a manner as to reduce the amount of bubbles occurring and/or remaining. 
     As in the case of the illustration of  FIGS. 10A ,  10 B and  10 C, in the example, the ink may be loaded through the infusion needle  180  while moving the infusion needle  180  gradually upward in step with the rise in the liquid level of the ink  120 . As in the case of the illustration of  FIGS. 9A ,  9 B and  9 C, if the infusion needle  180  is inserted into the hollow portion  404  of the swinging member  400 , the occurrence of bubbles can be more effectively prevented. 
     (Operation and Effect of Stirring Mechanism) 
     The swinging member  400  of the example swings about the support  401  provided at the lower end, whereby, as in the case of the foregoing embodiments, an ink flow is produced from the lower aperture  402  through the hollow portion  404  toward the upper aperture  403 , to stir the ink  120 . At this point, the intermediate aperture  410  can be operative to function similarly to the upper aperture  403 . The intermediate aperture  410  is capable of functioning as a substitute for the upper aperture  403  when the amount of ink remaining in the ink storage chamber  320  is reduced. It should be noted that the formation number, the shape, and the formation location of the intermediate aperture  410  may be selected as appropriate as long as they communicate with the hollow portion  404 . 
     Fourth Embodiment 
     Next, a fourth embodiment of the present invention will be described. A liquid container in this embodiment is an example of the case when it is applied as an ink cartridge which is mountable on the printing apparatus illustrated in  FIG. 1  to  FIG. 3 . In the ink cartridge of the embodiment, the volume of an ink storage chamber does not decrease even when the ink is consumed. In other words, the amount of ink in the ink storage chamber alone is decreased without a reduction in the volume of the ink storage chamber. 
     (Structure of Entire Ink Cartridge) 
       FIG. 21  is an exploded perspective view of an ink cartridge of the example. The ink cartridge of the example differs in the structure of a swinging member provided therein from the ink cartridge described in  FIG. 14 , and has the same structure of other components as that of the ink cartridge of  FIG. 14 . 
     (Structure of Stirring Mechanism) 
     A support  501  of a swinging member  500  provided in the ink cartridge of the example has two sides engaged with projections  309  provided on the inner wall of the container body  351  in order to support the swinging member  500 . The projections  309  serve fulcrums when the swinging member  500  swings. In the swinging member  500  a lower aperture  502  is formed in a lower portion in the gravity direction and an upper aperture  503  is formed in an upper portion, and a hollow portion  504  is formed between the apertures  502  and  503 . First and second intermediate apertures  510  and  511  are provided between the lower aperture  502  and the upper aperture  503  and communicate with the hollow portion  504 . The first intermediate aperture  510  is located in the lower side in the gravity direction and the second intermediate aperture  511  is located in the upper side in the gravity direction. 
     (Method for Loading Ink) 
       FIG. 22A  and  FIG. 22B  are side-sectional elevation views each showing the ink cartridge for illustrating a method for loading ink into the ink cartridge of the example, which correspond to the sectional views taken along the XXII-XXII line in  FIG. 21 . 
     As in the case of the foregoing embodiments, after the ink in the ink cartridge has been consumed or when the ink cartridge is initially loaded with ink, the infusion needle  180  is inserted into the ink cartridge as shown in  FIG. 22A . For the insertion of the infusion needle  180  into the ink cartridge, the hole  351 A is drilled in the container body  351 , and then the infusion needle  180  is inserted into the hole  351 A from above in the gravity direction. The method of inserting the infusion needle  180  is not limited to the method of drilling the hole  351 A in the ink cartridge and then inserting the infusion needle  180  as described above. For example, a hole provided in an ink cartridge in advance may be unsealed and then the infusion needle  180  may be inserted through the hole into the ink cartridge. 
     In the case of the example, the infusion needle  180  is inserted into the ink cartridge in such a manner as to be located outside the hollow portion  504  of the swinging member  500 , such that the leading end of the infusion needle  180  is located close to the bottom of the ink storage chamber  320 . 
     After the infusion needle  180  has been thus inserted as in the case of the aforementioned illustration in  FIGS. 17A and 17B , the ink  120  is loaded through the infusion needle  180  into the ink cartridge. Then, as shown in  FIG. 22B , the ink  120  is loaded until at least a part of the first intermediate aperture  510  is submerged in the ink. Then, the infusion needle  180  is removed and the hole  351 A is sealed. 
     In the ink loading process, the ink  120  is loaded relatively quickly and smoothly so as to prevent the occurrence of bubbles, as in the case of the aforementioned embodiments. If the ink  120  includes a material causing the occurrence of bubbles such as a surface-active agent, bubbles easily occur. To avoid this, the ink  120  is loaded smoothly not to produce a vortex. 
     As in the case of the foregoing embodiments, what is required is that the ink cartridge is loaded with the ink  120  to a level allowing, at least, the swinging member  500  to exercise its stirring function. Also, the ink cartridge when the ink is loaded is required to be in a position allowing the ink to be loaded in such a manner as to reduce the amount of bubbles occurring and/or remaining. 
     As in the case of the illustration of  FIGS. 10A ,  10 B and  10 C, in the example, the ink may be loaded through the infusion needle  180  while moving the infusion needle  180  gradually upward in step with the rise in the liquid level of the ink  120 . As in the case of the illustration of  FIGS. 9A ,  9 B and  9 C, when the infusion needle  180  is inserted into the hollow portion  504  of the swinging member  500 , the occurrence of bubbles can be more effectively prevented. 
     (Operation and Effect of Stirring Mechanism) 
     The swinging member  500  of the example swings about the support  501  provided at the lower end, whereby, as in the case of the foregoing embodiments, an ink flow is produced from the lower aperture  502  through the hollow portion  504  toward the upper aperture  503 , to stir the ink  120 . At this point, the intermediate apertures  510  and  511  can be operative to function similarly to the upper aperture  503 . For example, when the amount of ink remaining is reduced as shown in  FIG. 22B , the first intermediate aperture  510  is capable of functioning as substitutes for the upper and second intermediate apertures  503  and  511 . It should be noted that the formation number, the shape and the formation location of the first and second intermediate apertures  510  ad  511  may be selected as appropriate as long as they communicate with the hollow portion  504 . 
     Other Embodiments 
     In the foregoing embodiments, the swinging member as the stirring member swings about a swinging fulcrum set at a point closer to the bottom in the gravity direction (point closer to the lower aperture), in order to produce a flow of liquid from the bottom to the above through the hollow portion of the swinging member. However, the swinging fulcrum may be set at a point closer to the top of the swinging member (point closer to the upper aperture). In this case, a difference between the moving velocities of the upper aperture and the lower aperture produces a flow of liquid from the above toward the bottom in the hollow portion of the swinging member, thus making it possible to stir the liquid as in the case of the foregoing embodiments. In other words, the swinging operation of the swinging member about a fulcrum set at a support located closer to either the upper aperture or the lower aperture makes it possible to positively produce an ink flow either from the bottom to the above or from the above to the bottom in the hollow portion of the swinging member. In this case, either the upper aperture or the lower aperture functions as a first aperture located close to one end of the swinging member for introducing liquid and the other functions as a second aperture located close to the other end of the swinging member for making the liquid flow out. The direction of the flow of the liquid can be determined suitably in accordance with a shape of a liquid storage space, a kind of liquid, and the like. What is required is for the liquid flow to occur through, at least, two apertures and a hollow portion created between the apertures. Accordingly, the number, location, shape and the like are selectively determined for the hollow portion and apertures of the swinging member. Also, liquid is fed into a liquid container comprising such a swinging member by use of an infusion needle as in the case of the foregoing embodiments. As a result, it is possible to reduce the amount of bubbles occurring and/or remaining. 
     The structure of flowing means for producing a flow of the liquid passing through the hollow portion of the swinging member can be selectively determined. As this structure, structure involving the swinging movement of the swinging member as described alone is not specified. For example, the swinging member may be fixed. In this case, instead of moving the swinging member, a flow of the liquid may be induced from the outside of the liquid container, and the flow may be used to produce a difference in pressure, at least between portions of the liquid close to two apertures in the swinging member. 
     The swinging member is only one of various forms of the stirring member and accordingly the shape and the moving form of the stirring member are not particularly limited. Specifically, other than the stirring member swingable (turnable) about a certain fulcrum, the stirring member may be capable of reciprocating along a predetermined track or of moving freely along a certain face of the liquid container. It is important that a liquid flow is produced in the hollow portion of the stirring member in step with the movement of the stirring member. The liquid is fed into the liquid container comprising such a stirring member by use of the infusion needle as in the case of the foregoing embodiments. As a result, it is possible to reduce the amount of bubbles occurring and/or remaining. 
     As means for producing a liquid flow in a hollow portion of the stirring member, a centrifugal force and/or an inertial force of the liquid and the like can be used as well as a negative pressure of the liquid generated around an aperture on the basis of Bernoulli theorem when the aperture of the stirring member and the liquid are relatively moved. In other words, it is possible to, for example, utilize a centrifugal force of the liquid in the hollow portion caused by the swinging movement of the stirring member or to utilize an inertial force of the liquid caused inside and outside the hollow portion by moving and stopping of the stirring member. Mechanical kinetic energy, magnetic energy or the like can be externally introduced and used as a drive force to move the stirring member. The liquid is fed into the liquid container comprising such a stirring member by use of the infusion needle as in the case of the foregoing embodiments. As a result, it is possible to reduce the amount of bubbles occurring and/or remaining. 
     In the foregoing embodiments, the needle-shaped member (infusion needle) in which a liquid flow path is formed is used as the liquid loading member for loading liquid (ink) into the liquid reservoir (ink reservoir). However, what is required is for the liquid loading member to allow liquid to flow through the liquid loading member into the liquid reservoir. The liquid loading member is not necessarily required to be in a needle-shaped form. It is important that a loading flow path is provided for loading liquid into the liquid reservoir. The number of the liquid loading member equipped, and the direction of liquid flowing out from the liquid reservoir and the hollow portion of the stirring member can be determined suitably in accordance with the size, form and the like of the liquid container. The liquid loading member may have an air vent passage formed therein for making the air escape from the liquid reservoir and the hollow portion of the stirring member to the outside when the liquid is loaded, as well as a flow path formed therein for loading the liquid. A liquid loading member for forming a flow path for loading the liquid and a liquid loading member for forming an air vent passage may be employed. 
     In the foregoing embodiments, as an example of the liquid container in the present invention, the case when it is applied as a cartridge-type ink tank (ink cartridge) which is mountable on a so-called serial scan type ink jet printing apparatus has been described. However, the present invention is not limited to the allocation only to the ink cartridge, and is widely applicable as the liquid container for storing various liquids. The liquid container needs to comprise a swinging member having a hollow portion formed therein for guiding liquid. For the purpose of stirring the liquid in the liquid container, for example, the liquid container can be mounted on a carrier and the carrier can be reciprocated in order to swing the swinging member. The movement of the liquid container is not limited to reciprocating movement. For example, if the liquid container is moved in a certain direction, then stopped once, and then moved again in the same direction to move the swinging member, the liquid can be stirred. 
     The printing apparatus according to the present invention is applicable to, as well as general printing apparatus, apparatus such as a copier, a facsimile having a communications system and a word processor having a printing unit, and also an industrial printing apparatus compositely combined with various processors. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2007-119913, filed Apr. 27, 2007, which is hereby incorporated by reference herein its entirety.