Patent Publication Number: US-7914134-B2

Title: Ink cartridges and inkjet printers

Description:
The present application claims priority from Japanese Patent Application No. JP-2006-095662, which was filed on Mar. 30, 2006, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to ink cartridges and inkjet printers. In particular, the present invention is directed towards ink cartridges and inkjet printers, in which when ink drips from an ink supply portion of the ink cartridge, a protrusion receives the ink and retains the ink because of a capillary force created by grooves or holes formed in the protrusion. 
     2. Description of Related Art 
     A known inkjet recording system, such as the inkjet recording system described in JP2005-238815, includes an inkjet recording apparatus and a plurality of ink cartridges mounted side by side to a mounting portion of the inkjet recording apparatus. An ink supply opening is formed at one surface of the ink cartridge. An ink supply needle provided in the inkjet recording apparatus, is inserted through the ink supply opening when the ink cartridge is mounted to the inkjet recording apparatus, and ink within the ink cartridge is supplied to the inkjet recording apparatus. The ink cartridge includes a case, and a bag positioned within the case. The bag has a port for supplying ink within the bag to the outside of the ink cartridge, and the port is aligned with the ink supply opening. Within the port, a lid, a valve, and a spring are provided. The spring urges the valve, such that the valve contacts the lid. When the valve contacts the lid, the inside of the bag and the outside of the ink cartridge are not in fluid communication with each other. Nevertheless, when the ink supply needle pushes the valve against the urging force of the spring and the valve separates from the lid, the inside of the bag is in fluid communication with the outside of the ink cartridge. 
     Ink adheres to the ink supply needle after the ink supply needle is inserted into the ink cartridge through the ink supply opening. The ink adhering to the ink supply needle adheres to an area adjacent to the ink supply opening when the ink cartridge is removed from the mounting portion. The ink may drip from the ink supply opening on to the mounting portion. If the ink drips from the ink supply opening on to the mounting portion, the mounting portion becomes dirtied. In addition, ink may drip from the ink supply needle on to the mounting portion. After the mounting portion becomes dirtied, when a new ink cartridge is mounted to the mounting portion, the new ink cartridge also becomes dirtied. When a user of the inkjet recording system removes the new ink cartridge from the mounting portion, a hand of the user also may become dirtied. This is problematic, especially when the communication between the inside of the ink cartridge and the outside of the ink cartridge is prohibited by the valve urged by the spring. When the ink supply needle is removed from the ink supply opening, the spring pushes the valve back toward the ink supply opening. Therefore, ink is pushed by the valve toward the ink supply opening. A large amount of ink may be pushed out of the ink supply opening. 
     Another known ink cartridge includes an ink supply portion extending from one surface of the ink cartridge. An ink supply opening is formed at the end of the ink supply portion. Ink also may drip from the ink supply opening of this type of ink cartridge on to a mounting portion of an inkjet recording apparatus. 
     SUMMARY OF THE INVENTION 
     Therefore, a need has arisen for ink cartridges and inkjet printers which overcome these and other shortcomings of the related art. A technical advantage of the present invention is that when ink drips from an ink supply portion of the ink cartridge, a protrusion receives the ink and retains the ink because of a capillary force created by grooves or holes formed in the protrusion. Consequently, in operation, no ink or substantially no ink is transferred from the ink cartridge to a mounting portion of the inkjet printer. 
     According to an embodiment of the present invention, an ink cartridge comprises an ink chamber configured to store an ink, and a wall comprising a first end and a second end opposite the first end. The ink cartridge also comprises an ink supply portion configured to supply the ink from an interior of the ink chamber to an exterior of the ink chamber, and the ink supply portion is positioned at the wall adjacent to the second end of the wall. Moreover, the ink cartridge comprises a protrusion extending from the wall, and the protrusion is positioned between the ink supply portion and the second end of the wall. In an embodiment of the present invention, the protrusion comprises means for generating a capillary force which acts upon the ink when the ink is positioned on the protrusion. For example, in an embodiment of the present invention, the protrusion has a plurality of grooves formed therein. In another embodiment of the present invention, the protrusion has a plurality of openings formed therethrough or therein. 
     According to another embodiment of the present invention, an inkjet printer comprises a mounting portion and an ink cartridge mounted to the mounting portion. The ink cartridge comprises an ink chamber configured to store an ink, and a wall comprising a first end and a second end opposite the first end. The ink cartridge also comprises an ink supply portion configured to supply the ink from an interior of the ink chamber to an exterior of the ink chamber, and the ink supply portion is positioned at the wall adjacent to the second end of the wall. Moreover, the ink cartridge comprises a protrusion extending from the wall, and the protrusion is positioned between the ink supply portion and the second end of the wall. In an embodiment of the present invention, the protrusion comprises means for generating a capillary force which acts upon the ink when the ink is positioned on the protrusion. For example, in an embodiment of the present invention, the protrusion has a plurality of grooves formed therein. In another embodiment of the present invention, the protrusion has a plurality of openings formed therethrough or therein. Moreover, the mounting portion has a recess formed therein, the recess is configured to receive the protrusion, and the mounting portion comprises a detector configured to detect a presence of the protrusion. 
     Other objects, features, and advantages will be apparent to persons of ordinary skill in the art from the following detailed description of the invention and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present invention, needs satisfied thereby, and the objects, features, and advantages thereof, reference now is made to the following description taken in connection with the accompanying drawing. 
         FIG. 1  is a schematic diagram of an inkjet printer and an ink cartridge, according to an embodiment of the present invention. 
         FIG. 2  is a perspective view of the ink cartridge of  FIG. 1 . 
         FIG. 3(   a ) is a partial, cross-sectional view of the ink cartridge and the inkjet printer of  FIG. 1 , just before a mounting of the ink cartridge to the inkjet printer is completed. 
         FIG. 3(   b ) is a partial, cross-sectional view of the ink cartridge and the inkjet printer of  FIG. 1 , after the mounting of the ink cartridge to the inkjet printer is completed. 
         FIG. 4(   a ) is a schematic diagram of the ink cartridge of  FIG. 1 , when ink adheres to an ink supply portion. 
         FIG. 4(   b ) is a schematic diagram of the ink cartridge of  FIG. 1 , when ink is dripping. 
         FIG. 4(   c ) is a schematic diagram of the ink cartridge of  FIG. 1 , when ink has dripped on to a protrusion. 
         FIG. 5  is a perspective view of an ink cartridge, according to another embodiment of the present invention. 
         FIG. 6  is a perspective view of an ink cartridge, according to yet another embodiment of the present invention. 
         FIG. 7  is a perspective view of an ink cartridge, according to still another embodiment of the present invention. 
         FIG. 8  is a perspective view of an ink cartridge, according to still yet another embodiment of the present invention. 
         FIG. 9  is a perspective view of an ink cartridge, according to a further embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION 
     Embodiments of the present invention, and their features and advantages, may be understood by referring to  FIGS. 1-9 , like numerals being used for like corresponding parts in the various drawings. 
       FIG. 1  is a schematic diagram of an inkjet printer  1  and an ink cartridge  20 , according to an embodiment of the present invention. Inkjet printer  1  comprises an inkjet head  2 , a mounting portion  16 , a flexible tube  15 , a carriage  5 , a feeding mechanism  6 , and a purge device  7 . Inkjet head  2  comprises a plurality of nozzles  2   a  configured to eject ink toward a recording paper P. Mounting portion  16  is configured to mount ink cartridge  20 . When ink cartridge  20  is mounted to mounting portion  16 , ink cartridge  20  and inkjet head  2  communicate with each other via tube  15 . Carriage  5  is configured to reciprocate with inkjet head  2 , and feeding mechanism  6  is configured to feed recording paper P. Purge device  7  is configured to draw air or thickened ink from the inside of inkjet head  2 . 
     During a printing operation, inkjet head  2  reciprocates with carriage  5  in a direction which is perpendicular to a plane of  FIG. 1 , and recording paper P is fed by feeding mechanism  6  in a horizontal direction in  FIG. 1 . Inkjet head  2  faces recording paper P. The reciprocation of inkjet head  2  and the feeding of recording paper P are synchronized by a control means. Each time that inkjet head  2  crosses recording paper P, inkjet head  2  ejects ink from nozzles  2   a . Ink is supplied from ink cartridge  20  mounted to mounting portion  16  to inkjet head  2  via tube  15 . Nozzles  2   a  are positioned above mounting portion  16  and ink cartridge  20  to prevent ink from leaking from nozzles  2   a  when the printing operation is not performed. 
     Purge device  7  comprises a cap  10  and a pump  11 , and cap  10  is configured to selectively move toward and away from an ink-eject surface of inkjet head  2 . Nozzles  2   a  are positioned at the ink-eject surface, and cap  10  is configured to cover the ink-eject surface. Pump  11  is configured to draw ink from nozzles  2   a . When inkjet head  2  is positioned outside of a printable area, cap  10  may cover the ink-eject surface, and pump  11  may draw air or thickened ink from nozzles  2   a . The printable area is an area where inkjet head  2  may eject ink toward recording paper P. Evaporation of water from the ink may result in the thickening of the ink in nozzles  2 . This purge operation may recover ink-eject performance of inkjet head  2 . 
     Mounting portion  16  opens to the right in  FIG. 1 . Ink cartridge  20  may be inserted and mounted horizontally into an inside  16   a  of mounting portion  16  from the opening. Ink cartridge  20  may be removed from mounting portion  16  by pulling on a right edge of ink cartridge  20  to the right in  FIG. 1 . 
       FIG. 2  is a perspective view of ink cartridge  20 .  FIG. 3(   a ) is a partial, cross-sectional view of ink cartridge  20  and inkjet printer  1 , just before the mounting of ink cartridge  20  in mounting portion  16  is completed.  FIG. 3(   b ) is a partial cross-sectional view of ink cartridge  20  and inkjet printer  1 , after the mounting of ink cartridge  20  in mounting portion  16  is completed. 
     Ink cartridge  20  may have a rectangular parallelepiped shape. An ink chamber  21  is provided within ink cartridge  20 . Ink cartridge  20  comprises a side wall  20   a  and a cylindrical ink supply portion  22  extending from side wall  20   a . Side wall  20   a  faces an end wall  16   b  of mounting portion  16 , and ink supply portion  22  extends toward end wall  16   b  when ink cartridge  20  is mounted to mounting portion  16 . The direction that ink supply portion  22  extends is parallel with a direction that ink cartridge  20  is mounted to mounting portion  16 . Ink supply portion  22  has an ink supply path  23  formed therethrough. Ink supply path  23  communicates with ink chamber  21  and an outside of ink cartridge  20 . Ink may be supplied from an interior of ink chamber  21  to an exterior of the ink chamber  21  via ink supply path  23 . Ink supply path  23  extends in a direction which is parallel to the direction ink cartridge  20  is mounted to mounting portion  16 . Ink supply portion  22  has an end surface  22   a , which is most distant from side wall  20   a . End surface  22   a  has an ink supply opening  24  formed therein. Ink supply path  23  opens to the outside of ink cartridge  20  at ink supply opening  24 . Ink is supplied from ink chamber  21  to the outside of ink cartridge  20  via ink supply path  23  in a direction which is both parallel to the direction that ink cartridge  20  is mounted to mounting portion  16 , and is perpendicular to end surface  22   a . Accordingly, ink supply opening  24  is formed in a plane that is perpendicular to the direction that ink is supplied from ink chamber  21  to the outside of ink cartridge  20  via ink supply path  23 . 
     A cylindrical-tube shaped seal  25  is provided in ink supply path  23 . Ink supply path  23  has a center between ink chamber  21  and ink supply opening  24 . Seal  25  is positioned between ink supply opening  24  and a center of ink supply path  23 . Seal  25  comprises an elastic material, such as rubber. An ink supply tube  17  provided in mounting portion  16  moves into seal  25  when ink cartridge  20  is mounted to mounting portion  16 . Seal  25  is elastically pressed against an outside surface of ink supply tube  17 , which prevents ink from leaking between the outside surface of ink supply tube  17  and seal  25 . Ink supply path  23  comprises a wider portion  26 , and wider portion  26  has a radius which is greater than a radius of ink supply opening  24 . Wider portion  26  extends from ink chamber  21  to about the center of ink supply path  23 . A coil spring  27  and a valve  28  are provided within wider portion  26 . Coil spring  27  is positioned between valve  28  and ink chamber  21 , and urges valve  28  toward the outside of ink cartridge  20  in the direction which ink cartridge  20  is mounted to mounting portion  16 . Wider portion  26  connects with the rest of ink supply path  23  at a connecting surface  29 . Valve  28  has a radius, which is greater than a radius of the rest of ink supply path, but is less than the radius of wider portion  26 . Valve  28  is urged against connecting surface  29 , which prevents ink from leaking from ink chamber  21  to the outside of ink cartridge  20 . When ink supply tube  17  pushes valve  28  against the force of coil spring  27  and valve  28  separates from connecting surface  29 , ink flows into ink supply tube  17 . 
     Ink cartridge  20  comprises a protrusion  30  which extends from side wall  20   a  in the direction which ink cartridge  20  is mounted to mounting portion  16 . The direction which protrusion  30  extends is perpendicular to end surface  22   a . Cross-sectional shapes of protrusion  30  taken along a plane which is perpendicular to the direction that ink cartridge  20  is mounted to mounting portion  16  may be the same at any position of protrusion  30 . Side wall  20   a  has a first end and a second end opposite the first end. Ink supply portion  22  is positioned adjacent to the second end of side wall  20   a , and protrusion  30  is positioned between ink supply portion  22  and the second end of side wall  20   a . When ink cartridge  20  is mounted to mounting portion  16 , protrusion  30  is positioned below ink supply portion  22 . Protrusion  30  extends from side wall  20   a  further than ink supply portion  22  extends from side wall  20   a . Protrusion  30  has an end surface  30   a , which is most distant from side wall  20   a , and surface  30   a  is positioned further from side wall  20   a  than end surface  22   a  is positioned from side wall  20   a . Side wall  20   a  has a third end and fourth end opposite the third end. Side wall  20   a  has a height between the first end of the side wall  20   a  and the second end of the side wall  20   a , and side wall  20  has a width between the third end of the side wall  20   a  and the fourth end of the side wall  20   a . The direction of the height of side wall  20   a  is perpendicular to the direction of the width of side wall  20   a . The height of ink cartridge  20  corresponds to the height of the side wall  20   a , and the width of the ink cartridge  20  corresponds to the width of side wall  20   a . Protrusion  30  may have substantially the same width as that of side wall  20   a . When viewed from the height direction, ink supply portion  20  overlaps protrusion  30 . When ink cartridge  20  is mounted to mounting portion  16 , ink supply portion  20  overlaps protrusion  30  in a plane view. 
     Protrusion  30  has a first surface facing ink supply portion  20  and a second surface facing toward the second end of side wall  20   a . Each of the first surface and the second surface of protrusion  30  may have a plurality of inclined planes  31  and a plurality of inclined planes  32 . The plurality of inclined planes  31  and the plurality of inclined planes  32  are arranged alternately in the width direction, and each pair of inclined plane  31  and inclined plane  32  cross at an acute angle, forming a valley  33  or a peak  34  therebetween. In other words, each of the first surface and the second surface of protrusion  30  may have a plurality of grooves  38  formed therein. Each valley  33  extends from side wall  20   a  to end surface  22   a . In other words, each valley  33  extends in the direction which protrusion  30  extends. Accordingly, each of the first surface and the second surface of protrusion  30  may have a zigzagged shape. A width of grooves  38  corresponding to a distance t between immediate neighboring peaks  34  may be less than or equal to 5 mm, e.g., about 2 mm, and a distance t between a peak  35  positioned at an end of protrusion  30  and an immediate neighboring peak  34  also may be less than or equal to 5 mm, e.g., about 2 mm. Because the width of groove  38  maybe less than or equal to 5 mm, a capillary force may be generated in valley  33 . In operation, ink may drip from ink supply portion  22  or ink supply tube  17 . Valley  33  is configured to receive and to retain the ink therein via the capillary force. The width of groove  38  may become narrower while approaching the bottom of valley  33 . The bottom of valley is the point where inclined plane  31  and inclined plane  32  connect. The capillary force is strongest where groove  38  approaches the bottom of valley  33 . Therefore ink is securely retained in valley  33 . 
     Referring to  FIGS. 3(   a ) and  3 ( b ), ink supply tube  17  is provided in mounting portion  16 . Ink supply tube  17  is inserted into ink supply path  23  through ink supply opening  24  when ink cartridge  20  is mounted to mounting portion  16 . End surface  17   a  of ink supply tube  17  is positioned closer to ink cartridge  20  than end wall  16   b  is positioned to ink cartridge  20 . A cylindrical joint portion  14  is positioned at an outside surface  16   c  of end wall  16   b . One end of tube  15  is connected to joint portion  14 . A communication hole  16   d  is formed through end wall  16   b . A communication hole  17   b  formed through ink supply tube  17  and a communication hole  14   a  formed through joint portion  14  communicates through communication hole  16   d . Ink may be supplied from ink chamber  21  to inkjet head  2  through communication hole  17   b , communication hole  16   d , communication hole  14   a  and tube  15 . 
     A round recess  18  is formed in end wall  16   b , and ink supply tube  17  extends from the bottom of round recess  18 . Round recess  18  is configured to receive ink supply portion  22  when ink cartridge  20  is mounted to mounting portion  16 . The depth of round recess  18  is greater than or equal to the distance which ink supply portion  22  extends from side wall  20   a , and a portion of end surface  17   a  is cut out. 
     A recess  19  is formed in end wall  16   b , and recess  19  is configured to receive protrusion  30  when ink cartridge  20  is mounted to mounting portion  16 . Cross-sectional shapes of recess  19  taken along a plane perpendicular to the direction which ink cartridge  20  is mounted to mounting portion  16  are the same at any position of recess  19 . The cross-sectional shape of recess  19  is similar to the cross-sectional shape of protrusion  30  and the size of recess  19  may be greater than or equal to the size of protrusion  30 . Recess  19  receives protrusion  30  and positions ink cartridge  20  accurately in mounting portion  16 . In an embodiment, a plurality of ink cartridges  20  may be used. For example, four ink cartridges  20  may be used, and each ink cartridge  20  may contain a different-color ink, such as cyan, magenta, yellow and black respectively, and four mounting portions  16  may be used, which receive the four ink cartridges  20  respectively. Protrusions  30  of the four ink cartridges may have different cross-sectional shapes, respectively, and recesses  19  may have different cross-sectional shapes corresponding to the cross-sectional shapes of protrusions  30 , respectively. This may prevent an insertion of ink cartridge  20  into a wrong mounting portion  16 . For example, an insertion of ink cartridge  20  containing yellow ink into the mounting portion  16  which is configured to receive ink cartridge  20  containing black ink may be prevented. 
     A switch  13  is provided at the bottom of recess  19 , and switch  13  comprises a moveable member and a spring. The moveable member is urged by the spring to extend from the bottom of recess  19 . When the ink cartridge  20  is inserted into mounting portion  16 , end surface  30   a  of protrusion  30  pushes the moveable member against the urging force of the spring. When the moveable member is pushed, a signal is transmitted to a control means, and the control means determines whether the mounting of ink cartridge  20  is complete based on the signal. Therefore, a printing operation with ink cartridge  20  not mounted completely may be prevented. If the printing operation occurs with ink cartridge  20  not mounted completely, air may be drawn inside the inkjet head, resulting in a misprinting. Protrusion  30  functions not only as a means for retaining ink, but also as a means for determining whether the mounting of ink cartridge  20  is complete. This dual function provided by protrusion  30  reduces the number of parts of ink cartridge  20 . 
     When ink cartridge  20  is mounted from the state shown in  FIG. 3(   a ) to the state shown in  FIG. 3(   b ), end surface  17   a  of ink supply tube  17  pushes valve  28  against the urging force of coil spring  27 . Because the outside surface of ink supply tube  17  contacts seal  25  during the mounting operation, ink in ink chamber  21  and wider portion  26  does not leak through seal  25 , and instead flows in to communication hole  17   b  through the cut-out formed in end surface  17   a . Accordingly, when ink cartridge  20  is mounted to mounting portion  16 , ink may not leak. 
     Nevertheless, when ink cartridge  20  is removed from mounting portion  16 , ink may leak. When ink supply tube  17  is removed from ink supply path  23 , valve  28  is pushed back to contact connecting surface  29 , and valve  28  may push ink from wider portion  26  toward ink supply opening  24 , and this ink may drip from ink supply opening  24 . In addition, when ink supply tube  17  is removed from ink supply path  23 , ink adhering to outside surface of ink supply tube  17  may adhere to an area adjacent to ink supply opening  24 , and this ink may drip from ink supply opening  24 . Referring to  FIG. 4(   a ), ink adhering to end surface  22   a  may be retained on end surface  22   a  by surface tension. Nevertheless, referring to  FIG. 4(   b ), when the amount of ink is too large, ink drips off. In addition, ink adhering to the outside surface of ink supply tube  17  may drip off when ink supply tube  17  removed from ink supply opening  24 . 
     Referring to  FIG. 4(   c ), ink which has dripped from end surface  22  and/or the outside surface of ink supply tube  17  may land on about a center of protrusion  30  and may spread into valleys  33  along inclined planes  31  and inclined planes  32 . Ink may be retained within each valley  33 . Because the first surface and the second surface of protrusion  30  include valleys which create capillary forces, protrusion  30  as a whole can retain ink. Ink may be retained in protrusion  30  regardless of the orientation of ink cartridge  20  after ink cartridge  20  is removed from mounting portion  16 . For example, even when ink cartridge  20  is oriented, such that protrusion  30  is positioned above ink supply portion  22 , ink may be retained in protrusion  30 . 
     As discussed above, when ink cartridge  20  is removed from mounting portion  16 , protrusion  30  may receive ink which has dripped from ink supply opening  24 /end surface  22   a  and/or from the outside surface of ink supply tube  17 , and ink may be retained in protrusion  30  by capillary forces generated within grooves  38  or valleys  33 . Accordingly, mounting portion  16  may not become dirtied by ink. 
     Because protrusion  30  extends from side wall  20   a , protrusion  30  may securely receive ink, and the structure of ink cartridge  20  may be simplified, and because protrusion  30  is positioned below ink supply portion  22 , protrusion  30  may securely receive ink. Moreover, because the width of distance t or grooves  38  is less than or equal to 5 mm, received ink may be securely retained in protrusion  30 , and because grooves  38  or valleys  33  are provided at the first surface of protrusion  30  facing ink supply portion  22 , ink may be securely received and retained by protrusion  30 , and it may be difficult for the ink to move once the ink is positioned on protrusion  30 . 
       FIG. 5  is a perspective view of an ink cartridge  220 , according to another embodiment of the present invention. Ink cartridge  220  may be similar to ink cartridge  20 . Therefore, only those differences between ink cartridge  220  and ink cartridge  20  are discussed with respect to ink cartridge  220 . 
     Referring to  FIG. 5 , ink cartridge  220  comprises a protrusion  230  extending from side wall  20   a . Protrusion  230  has an end surface  230   a  which is most distant from side wall  20   a . End surface  230   a  is more distant from side wall  20   a  than end surface  22   a  is from sidewall  20   a . Protrusion  230  has a first surface facing ink supply portion  20  and a second surface facing toward the second end of side wall  20   a . Each of the first surface and the second surface of protrusion  230  has a plurality of inclined planes  231  and a plurality of inclined planes  232 . The plurality of inclined planes  231  and the plurality of inclined planes  232  are arranged alternately in the direction that protrusion  230  extends from side wall  20   a , and each pair of inclined plane  231  and inclined plane  232  cross at an acute angle, forming a valley  233  or a peak  234  therebetween. Each valley  233  extends in the width direction which is perpendicular to the direction that protrusion  230  extends from side wall  20   a . Accordingly, each of the first surface and the second surface of protrusion  230  is formed into a zigzagged shape. In other words, each of the first surface and the second surface of protrusion  230  has a plurality of grooves  238  formed therein. A width of grooves  238  corresponding to a distance t 1  between immediate neighboring peaks  234  may be less than or equal to 5 mm, and a distance t 1  between a peak  235 , which is positioned at an end of protrusion  230  in the direction that protrusion  230  extends from side wall  20   a , and an immediate neighboring peak  234  also may be less than or equal to 5 mm. Protrusion  230  may receive and retain ink which has dripped from ink supply opening  24 /end surface  22   a  and/or the outside surface of ink supply tube  17 . 
       FIG. 6  is a perspective view of an ink cartridge  320 , according to yet another embodiment of the present invention. Ink cartridge  320  may be similar to ink cartridge  20 . Therefore, only those differences between ink cartridge  320  and ink cartridge  20  are discussed with respect to ink cartridge  320 . Referring to  FIG. 6 , ink cartridge  320  comprises a protrusion  330  extending from side wall  20   a . The second surface of protrusion  330  facing toward the second end of side wall  20   a  is flat. Therefore, the second surface may not retain ink thereon. Nevertheless, the shape of protrusion  330  is simplified with respect to ink cartridge  20 , and the surface of protrusion  330  facing ink supply portion  22  provides a similar effect as the first surface of protrusion  30 . 
       FIG. 7  is a perspective view of an ink cartridge  420 , according to still another embodiment of the present invention. Ink cartridge  420  may be similar to ink cartridge  20 . Therefore, only those differences between ink cartridge  420  and ink cartridge  20  are discussed with respect to ink cartridge  420 . Referring to  FIG. 7 , ink cartridge  420  comprises a protrusion  430  extending from side wall  20   a . Protrusion  430  has an end surface  430   a  which is most distant from side wall  20   a . End surface  430   a  is more distant from side wall  20   a  than end surface  22   a  is from side wall  20   a . Protrusion  430  has a first surface facing ink supply portion  20 , and a second surface facing toward the second end of side wall  20   a . The first surface has a plurality of protruding portions  433  which extend toward ink supply portion  22  and are arranged in the width direction, such that grooves  438  are formed between adjacent protruding portions  433 . Each of grooves  438  extends in the direction which protrusion  430  extends from side wall  20   a  to end surface  430   a . Groove  438  is defined by a bottom surface, a side surface of one of protruding portions  433  extending from the bottom surface, and a side surface of an adjacent protruding portion  433 . The two side surfaces are parallel to each other. A width of groove  438  corresponds to a distance t 2  between the two side surfaces, which is less than or equal to 5 mm. The first surface of protrusion  430  facing ink supply portion  22  provides a similar effect as the first surface of protrusion  30 . 
       FIG. 8  is a perspective view of ink cartridge  520 , according to still yet another embodiment of the present invention. Ink cartridge  520  may be similar to ink cartridge  20 . Therefore, only those differences between ink cartridge  520  and ink cartridge  20  are discussed with respect to ink cartridge  520 . Referring to  FIG. 8 , ink cartridge  520  comprises protrusion  530  extending from side wall  20   a . Protrusion  530  has an end surface  530   a , which is most distant from side wall  20   a . End surface  530   a  is more distant from side wall  20   a  than end surface  22   a  is from sidewall  20   a . Protrusion  530  has a rectangular parallelepiped shape, and has a plurality of holes  533  ( 538 ) formed therethrough or therein in the height direction. The diameter of each hole  533  is less than or equal to 5 mm, which creates a capillary force within holes  533 . Protrusion  530  may receive ink which has dripped from ink supply opening  24 /end surface  22   a  and/or from the outside surface of ink supply tube  17 , and the ink may be retained in protrusion  530  by the capillary forces generated within holes  533 . Because holes  533  are formed, a relatively large amount of ink may be retained in protrusion  530 . When an ink droplet drips on to a first surface of protrusion  530  facing ink supply portion  22 , ink which already is retained within holes  533  tends to be united with the ink droplet. Therefore, ink within holes  533  holds the ink on the first surface, and it may be difficult for the ink on the first surface to move. 
       FIG. 9  is a perspective view of ink cartridge  620 , according to a further embodiment of the present invention. Ink cartridge  620  may be similar to ink cartridge  20 . Therefore, only those differences between ink cartridge  620  and ink cartridge  20  are discussed with respect to ink cartridge  620 . Referring to  FIG. 9 , ink cartridge  620  comprises a protrusion  630  extending from side wall  20   a . Protrusion  630  has an end surface  630   a , which is most distant from side wall  20   a . End surface  630   a  is more distant from side wall  20   a  than end surface  22   a  is from side wall  20   a . Protrusion  630  has a rectangular parallelepiped shape, and has a plurality of holes  633  ( 638 ) formed therethrough or therein in the width direction. The diameter of each hole  633  is less than 5 mm, which creates a capillary force within hole  633 . Protrusion  630  may receive ink which has dripped from ink supply opening  24 /end surface  22   a  and/or from the outside surface of ink supply tube  17 , on a first surface facing ink supply portion  22 . The ink may flow along the first surface and surfaces extending from the first surface, and then may flow into holes  633  and may be retained in protrusion  630  by the capillary forces generated within holes  633 . 
     The present invention is not limited to the above-described embodiments. Various modifications may be applied. For example, a direction which protrusion  30 ,  230 ,  330 ,  430 ,  530 ,  630  extends may not be parallel with the direction that the ink cartridge  20 ,  220 ,  320 ,  420 ,  520 ,  620  is mounted to mounting portion  16 . In this case, recess  19  may extend to correspond to the direction which protrusion  30 ,  230 ,  330 ,  430 ,  530 ,  630  extends. Switch  13  is not limited to a physical switch. Switch  13  may detect protrusion  30 ,  230 ,  330 ,  430 ,  530 ,  630  optically. For example, switch  13  may emit visible light or infra red light. Ink supply portion  22  may not extend from side wall  20   a . In this case, ink may leak from ink supply opening  24  and may flow on to protrusion  30 ,  230 ,  330 ,  430 ,  530 ,  630  along side wail  20   a  and may be retained in protrusion  30 ,  230 ,  330 ,  430 ,  530 ,  630 . Moreover, grooves  38 ,  238 ,  338 ,  438 , and holes  538  and  638  may be greater than 5 mm. For example, ink may be retained in the grooves or holes depending on the viscosity of ink or the surface tension of the ink with respect to material of protrusion  30 ,  230 ,  330 ,  430 ,  530 ,  630 . 
     While the invention has been described in connection with embodiments of the invention, it will be understood by those skilled in the art that variations and modifications of the embodiments described above may be made without departing from the scope of the invention. Other embodiments will be apparent to those skilled in the art from a consideration of the specification or from a practice of the invention disclosed herein. It is intended that the specification and the described examples are consider exemplary only, with the true scope of the invention indicated by the following claims.