Patent Publication Number: US-8113640-B2

Title: Liquid droplet discharging apparatuses and liquid cartridges

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority from Japanese Patent Application No. JP-2008-82999, which was filed on Mar. 27, 2008, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to liquid droplet discharging apparatuses, e.g., ink-jet printers, and liquid cartridges, e.g., ink cartridges, to be used with liquid droplet discharging apparatuses. 
     2. Description of Related Art 
     In a known ink-jet printer, ink is supplied from an ink cartridge to a discharging head and then discharged from a plurality of nozzles formed in the discharging head, such that an image is printed on a sheet of paper. When gas is dissolved in ink in the ink cartridge, the gas may form gas bubbles, and the gas bubbles may be supplied to the discharging head together with ink. As a consequence, the gas bubbles may cause a discharge failure in the nozzles, thereby lowering the printing quality. In order to prevent gas bubbles from forming, when the ink cartridge is manufactured, gas dissolved in the ink is discharged to an exterior of the ink cartridge by depressurizing an ink chamber of the ink cartridge, such that the pressure of the ink chamber is less than the atmospheric pressure. The ink cartridge is packed and shipped in this depressurized state. A similar method is described in JP-A-2007-144804, for example. 
     When an ink cartridge is mounted to an ink-jet printer, if the ink chamber is brought into communication with the discharging head while the ink chamber is still in a depressurized state, a reverse flow of ink from the discharging head toward the ink cartridge may occur, and air may enter the discharging head through the nozzles. As a result, menisci of ink formed in the nozzles of the discharging head are destroyed, and ink no longer may be discharged stably. To prevent this, the ink cartridge has an air communication valve, in addition to an ink supply valve. When opened, the air communication valve permits the pressure of the interior of the ink chamber to equalize with the atmospheric pressure. During a mounting operation, when the ink cartridge is mounted to the printer, the air communication valve is opened before the ink supply valve is opened, in order to equalize the pressure and prevent a reverse flow of ink from the discharging head toward the ink cartridge. 
     Nevertheless, when a user mounts the ink cartridge to the printer quickly, the period of time between opening the air communication valve and opening the ink supply valve may be short, and the pressure of the ink chamber may not have sufficient time to equalize with the atmospheric pressure. Hence, the ink chamber may be brought into communication with the discharging head before the pressure in the ink chamber reaches the atmospheric pressure. Accordingly, the menisci of ink formed in the nozzles of the discharging head may be destroyed, and ink no longer may be discharged stably. 
     SUMMARY OF THE INVENTION 
     Therefore, a need has arisen for liquid droplet discharging apparatuses and liquid cartridges that overcome these and other shortcomings of the related art. A technical advantage of the invention is that pressure in a liquid chamber of a liquid cartridge may reach the atmospheric pressure, or a pressure close to the atmospheric pressure, before the liquid chamber is brought into communication with a discharging head of a liquid droplet discharging apparatus, even when a user mounts the liquid cartridge to the liquid droplet discharging apparatus quickly. 
     According to an embodiment of the invention, a liquid cartridge has a liquid chamber configured to store liquid, and a liquid supply opening configured to supply liquid from an interior of the liquid chamber to an exterior of the liquid chamber. A first closing mechanism is configured to selectively cover and uncover the liquid supply opening. An air communication opening formed in the liquid cartridge is configured to place the interior of the liquid chamber in communication with an exterior of the chamber, in order to equalize a pressure in the liquid chamber with an atmospheric pressure. A second closing mechanism is configured to selectively cover and uncover the air communication opening. When the liquid cartridge is mounted to a cartridge mounting portion of a liquid discharging apparatus, a damper located in one of the liquid cartridge and the cartridge mounting portion is configured to oppose at least a portion of a mounting force applied to the liquid cartridge. During the mounting of the liquid cartridge to the cartridge mounting portion, the first closing mechanism and the second closing mechanism are configured, such that the air communication opening is uncovered before the liquid supply opening is uncovered. 
     According to another embodiment of the invention, a liquid cartridge has a liquid chamber configured to store liquid, and a liquid supply opening configured to supply liquid from an interior of the liquid chamber to an exterior of the liquid chamber. A first closing mechanism is configured to selectively cover and uncover the liquid supply opening. An air communication opening formed in the liquid cartridge is configured to place the interior of the liquid chamber in communication with an exterior of the chamber, in order to equalize a pressure in the liquid chamber with an atmospheric pressure. A second closing mechanism is configured to selectively cover and uncover the air communication opening. The liquid cartridge comprises a damper configured to oppose at least a portion of a force applied to the liquid cartridge during a mounting operation by creating a resistance. 
     Other objects, features, and advantages of embodiments of the invention will be apparent to persons of ordinary skill in the art from the following description of embodiments with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       For a more complete understanding of the invention, the needs satisfied thereby, and the objects, features, and advantages thereof, reference now is made to the following description taken in connection with the accompanying drawings. 
         FIG. 1  is a perspective view of a multifunction device comprising an ink-jet printer according to an embodiment of the invention. 
         FIG. 2  is a schematic plan view of the ink-jet printer of  FIG. 1 . 
         FIG. 3  is a schematic, partial, cross-sectional view of the ink-jet printer of  FIG. 1 . 
         FIG. 4  is a cross-sectional view of a cartridge mounting portion and an ink cartridge of the ink-jet printer of  FIG. 1 . 
         FIG. 5  is a top view of the ink cartridge seen in a direction of an arrow X in  FIG. 4 . 
         FIG. 6  is a cross-sectional view of the cartridge mounting portion and the ink cartridge of  FIG. 4  during a mounting of the ink cartridge to the cartridge mounting portion. 
         FIG. 7  is an enlarged cross-sectional view of a protrusion and a recess when the protrusion is inserted into the recess according to an embodiment of the invention. 
         FIG. 8  is a cross-sectional view of the cartridge mounting portion and the ink cartridge of  FIG. 4  when the mounting of the ink cartridge to the cartridge mounting portion is completed. 
         FIG. 9  is a cross-sectional view of a cartridge mounting portion and an ink cartridge according to another embodiment of the invention. 
         FIG. 10  is a cross-sectional view of the cartridge mounting portion and the ink cartridge of  FIG. 9  during a mounting of the ink cartridge to the cartridge mounting portion. 
         FIG. 11  is a cross-sectional view of the cartridge mounting portion and the ink cartridge of  FIG. 9  when the mounting of the ink cartridge to the cartridge mounting portion is completed 
         FIG. 12  is a cross-sectional view of a cartridge mounting portion and an ink cartridge according to yet another embodiment of the invention. 
         FIG. 13  is a cross-sectional view of the cartridge mounting portion and the ink cartridge of  FIG. 12  during a mounting of the ink cartridge to the cartridge mounting portion. 
         FIG. 14  is a cross-sectional view of the cartridge mounting portion and the ink cartridge of  FIG. 12  when the mounting of the ink cartridge to the cartridge mounting portion is completed. 
         FIG. 15  is a cross-sectional view of a cartridge mounting portion and an ink cartridge according to still another embodiment of the invention. 
         FIG. 16  is a cross-sectional view of the cartridge mounting portion and the ink cartridge of  FIG. 15  during a mounting of the ink cartridge to the cartridge mounting portion. 
         FIG. 17  is a cross-sectional view of the cartridge mounting portion and the ink cartridge of  FIG. 15  when the mounting of the ink cartridge to the cartridge mounting portion is completed. 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     Embodiments of the invention and their features and technical advantages may be understood by referring to  FIGS. 1-17 , like numerals being used for like corresponding portions in the various drawings. 
     Referring to  FIG. 1 , a multifunction device  1  according to an embodiment of the invention may have a printer function, a scanner function, a copying function, and a facsimile function, and may comprise an ink-jet printer  3  in the lower portion of a body  2  of multifunction device  1 , and a scanner  4  at the top portion of body  2 . An opening  5  may be formed through the front of body  2 . Ink-jet printer  3  may comprise a paper feed tray  6  and a paper discharge tray  7  positioned above paper feed tray. Paper feed tray  6  and paper discharge tray  7  may be removed via opening  5 . Multifunction device  1  may comprise a cover  8  at the front lower right portion of body  2 , and ink-jet printer  3  may comprise a cartridge mounting portion  19  in the front lower right portion of body  2 . When cover  8  is opened, cartridge mounting portion  19  may be exposed to an exterior of body  2 . Multifunction device  1  may comprise an operation panel  10  having buttons for inputting instruction for operating ink-jet printer  3 , scanner  4  and the like, and a display device  9 , on the upper front portion of body  2 . Multifunction device  1  may be operable by instruction from an external personal computer (not shown). 
     Referring to  FIG. 2 , ink-jet printer  3  may comprise a pair of guide rails  11 ,  12  extending substantially parallel to each other, and an image printing unit  13  is supported by guide rails  11  and  12 , such that image printing unit  13  is slidable in a scanning direction. Image printing unit  13  may be joined to a timing belt  16  which is wound around a pair of pulleys  14  and  15 , and timing belt  16  may extend in a direction substantially parallel to a direction in which guide rail  12  extends. Pulley  15  may be coupled to a motor (not shown) which may be driven to rotate in a forward direction and a reverse direction. When pulley  15  is driven to rotate in the forward and reverse directions, timing belt  16  moves, such that image printing unit  13  reciprocates in the scanning direction along guide rails  11  and  12 . 
     Image printing unit  13  may comprise a carriage  17 , which may serve as a casing, and buffer tanks  18  may be mounted to carriage  17 . Cartridge mounting portion  19  may be positioned in front of the right end of guide rail  12 . Four ink cartridges  20 A to  20 D, having ink in four colors (black, cyan, magenta, and yellow) respectively stored therein, may be removably mounted to cartridge mounting portion  19 . Ink cartridges  20 A to  20 D mounted to cartridge mounting portion  19  may be connected to respective buffer tanks  18  via ink supply tubes  21 . 
     Referring to  FIG. 3 , paper feed tray  6  may be positioned at the bottom of multifunction device  1 . A paper feed roller  25  may be positioned above paper feed tray  6  and may be configured to feed an uppermost sheet of paper  23  from paper feed tray  6  to a paper feed path  24 . Paper feed path  24  may extend upward from the rear side of paper feed tray  6 , make a U-turn toward the front of the multifunction device, and then extend through a printing area  26  to paper discharge tray  7 . 
     Image printing unit  13  may be positioned in printing area  26 . A platen  27  may be positioned below image printing unit  13 , and the size of platen  27  may be greater than the size of the sheet of paper  23 . A transporting roller  28  and a pinch roller  29  may be positioned at an upstream side of image printing unit  13  with respect to paper feed path  24 . Transporting roller  28  and pinch roller  29  may pinch the sheet of paper  23  fed along paper feed path  24  and transport the sheet of paper  23  to above platen  27 . A paper discharge roller  30  and a pinch roller  31  may be positioned at a downstream side of image printing unit  13  with respect to paper feed path  24 . Paper discharge roller  30  and pinch roller  31  may pinch the sheet of paper  23  passing above platen  27  and transport the sheet of paper  23  to paper discharge tray  7 . 
     Image printing unit  13  may comprise an ink-jet head  35  configured to discharge ink from a plurality of nozzles formed therein toward platen  27 , buffer tanks  18  configured to temporarily store ink to be supplied to ink-jet head  35 , a head control board  34  configured to control driving of ink-jet head  35 , and a carriage  17  on which ink-jet head  35 , buffer tanks  18 , and head control board  34  may be mounted. Ink-jet head  35  may comprise a flow channel unit  32  configured to guide ink supplied from buffer tanks  18  to the nozzles, and a piezoelectric actuator  33  positioned above flow channel unit  32 , and configured to selectively provides ink in flow channel unit  32  with discharge pressure directed to nozzles. 
     Ink cartridges  20 A to  20 D may be connected to respective buffer tanks  18  via the cartridge mounting portion  19  and ink supply tubes  36 . 
     Cartridge mounting portion  19  may comprise four sensors  37  for optically detecting the remaining amounts of ink stored in mounted ink cartridges  20 A to  20 D, respectively. A control device  40  may be electrically connected to sensors  37 , display device  9 , and head control board  34 . Control device  40  may determine the remaining amounts of ink in ink cartridges  20 A to  20 D from data output from sensors  37  and head control board  34 , and may cause display device  9  to display the remaining amounts of ink. 
     Ink cartridge  20 A is described in reference to  FIG. 4 . Because the four ink cartridges  20 A to  20 D may have substantially the same structure, the same description applies to ink cartridges  20 B to  20 D. 
     Referring to  FIG. 4 , ink cartridge  20 A may comprise a case  50  comprising an ink chamber  51  formed therein, and ink chamber  51  may be configured to store ink  100  therein. When ink cartridge  20 A is manufactured, the interior of ink chamber  51  may be depressurized to a level less than the atmospheric pressure to remove gas dissolved in ink stored in ink chamber  51 , and ink cartridge  20 A may be packed and shipped in a depressurized state. An air communication opening  52  may be formed through a front wall of case  50 . The front wall of case  50  may be positioned at the front of case  50  during the mounting of ink cartridge  20 A to cartridge mounting portion  19 . Air communication opening  52  may be positioned adjacent to a top wall of case  50 . The top wall of case  50  may be positioned at the top of case  50  during the mounting of ink cartridge  20 A to cartridge mounting portion  19 . Ink cartridge  20 A may comprise an air communication closing mechanism  70  positioned at air communication opening  52 , and air communication closing mechanism  70  may be configured to cover air communication opening  52 . Air communication closing mechanism  70  may comprise a valve storage chamber  53  which is continuous with air communication opening  52 . Air communication closing mechanism  70  may comprise an annular sealing member  54  positioned in valve storage chamber adjacent to air communication opening  52 . 
     Valve storage chamber  53  may extend from air communication opening  52  toward ink chamber  51 . Air communication closing mechanism  70  may comprise an air communication valve element  55  stored in valve storage chamber  53 , a rod member  55   a  extending through air communication opening  52  to the exterior of case  50 , and a flange portion  55   b  which may extend radially outward from an end portion of rod member  55   a  in valve storage chamber  53 . Air communication valve element  55  may comprise a spring  56 , and air communication valve element  55  may be urged by spring  56 , such that flange portion  55   b  contacts sealing member  54  to cover air communication opening  52 . Valve storage chamber  53  may have a communication opening  53   a  which communicates with an air layer formed in an upper portion of ink chamber  51 . 
     Case  50  may have a protrusion  58  extending outward from the front face of case  50 . When ink cartridge  20 A is mounted to cartridge mounting portion  19 , protrusion  58  may be positioned adjacent to sensor  37 . Protrusion  58  may comprise side walls extending vertically, and each of the side walls of protrusion  58  may comprise a translucent portion made of a transparent or semi-transparent material. Ink cartridge  20 A may comprise a sensor arm  59  positioned in ink chamber  51 , and case  50  may comprise a supporting member  60  supporting sensor arm  59  pivotably. Sensor arm  59  may comprise a support potion  59   c  supported by a shaft of supporting member  60 , a float portion  59   b  extending from support portion  59   c  in one direction, e.g., to the left in  FIG. 4 , and an arm portion  59   a  extending from support portion  59   c  in another direction, e.g., to the right in  FIG. 4 . Float portion  59   b  may have a hollow portion therein, such that the average specific gravity of float portion  59   b  is less than the specific gravity of ink. A distal end of the arm portion  59   a  is positioned in an inner space of protrusion  58 . 
     An ink supply opening  64  may be formed through the front wall of case  50  adjacent to a bottom wall of case  50 . The bottom wall of case  50  may be positioned at the bottom of case  50  during the mounting of ink cartridge  20 A to cartridge mounting portion  19 . Ink cartridge  20 A may comprise ink supply closing mechanism  71  positioned at ink supply opening  64 , and ink supply closing mechanism  71  may be configured to cover ink supply opening  64 . Ink supply closing mechanism  71  may comprise a valve storage chamber  66  which is continuous with ink supply opening  64 . Valve storage chamber  66  may be bounded by a bounding wall  65 , having a L-shape in cross-section. A gap may be formed between the bottom wall of case  50  and an end of bounding wall  65 , and valve storage chamber  66  may communicate with ink chamber  51  through the gap. 
     Ink supply closing mechanism  71  may comprise an ink supply valve element  68  and an annular sealing member  67  stored in valve storage chamber  66 . Annular sealing member  67  may be positioned adjacent to ink supply opening  64 , such that a center opening  67   a  is aligned with ink supply opening  64 . Ink supply closing mechanism  71  may comprise a spring  69  stored in valve storage chamber  66 . Ink supply valve element  68  may be urged toward annular sealing member  60  by spring  69 , such that ink supply valve element  68  contacts an annular seal lip  67   b  of annular sealing member  67  and covers ink supply opening  64 . 
     Case  50  may comprise a recess  62  formed in the front wall of case  50  between protrusion  58  and ink supply opening  64 . Referring to  FIG. 7 , recess  62  may comprise a bottomed cylindrical portion  62   a  having a substantially constant diameter and a tapered portion  62   b  whose diameter increases extending from bottomed cylindrical portion  62   a  toward the exterior of case  50 . Referring to  FIG. 4 , the bottom and top surfaces of case  50  may comprise guide grooves  50   a  and  50   b  formed therein, respectively. The diameter of each of guide grooves  50   a  and  50   b  may be greater at a first portion of guide grooves  50   a  and  50   b , which may be positioned closer to the front wall of case  50 , than at a second portion of guide grooves  50   a  and  50   b , which may be positioned further away from the front wall of case  50  than the first portion. As a result, guide ribs  44  and  45  of cartridge mounting portion  19  readily may enter guide grooves  50   a  and  50   b , respectively, when ink cartridge  20 A is mounted to cartridge mounting portion  19 . 
     Referring to  FIG. 4 , cartridge mounting portion  19  may comprise an end wall  19   a  extending in the vertical direction, a lower wall  19   b  extending from the lower end of end wall  19   a , and an upper wall  19   c  extending from the upper end of end wall  19   a  in the same direction in which lower wall  19   b  extends. Lower wall  19   b  and upper wall portion  19   c  may comprise guide ribs  44  and  45 , respectively, and guide ribs  44  and  45  may fit into guide grooves  50   a  and  50   b  of ink cartridge  20 A, when ink cartridge  20 A is mounted to cartridge mounting portion  19 . 
     End wall  19   a  may comprise a recess  19   d  recessed in an opposite direction from the direction in which lower wall  19   b  and upper wall  19   c  extend. Recess  19   d  may be recessed away from ink cartridge  20 A, when ink cartridge  20 A is mounted to cartridge mounting portion  19 . Sensor  37  (e.g., a transmissive photo interrupter) may be provided in recess  19   d . Sensor  37  may be configured to detect the movement of sensor arm  59 , and control device  40  may determine whether the amount of ink  100  in ink chamber  51  reaches a predetermined amount. 
     A tube  42  may extend from end wall  19   a  in the same direction as lower wall  19   b  and upper wall  19   c  extend. Tube  42  may have an ink flow path  42   a  formed therein. Ink entry openings  42   b  may be formed through tube  42  extending from ink flow path  42   a  to the outer peripheral surface of tube  42  at a portion adjacent to the distal end of tube  42 . Ink supply tube  21  may be connected to tube  42  outside cartridge mounting portion  19 . A protrusion  43  may extend from end wall  19   a  in the same direction as lower wall  19   b  and upper wall  19   c  extend, and may be positioned between recess  19   d  and tube  42 . 
     Referring to  FIGS. 6 to 8 , a mounting operation of ink cartridge  20 A to cartridge mounting portion  19  is described. Referring to  FIG. 6 , when ink cartridge  20 A is inserted into cartridge mounting portion  19  by a user, while ink cartridge  20 A is guided by guide grooves  50   a  and  50   b  of ink cartridge  20 A and guide ribs  44  and  45  of cartridge mounting portion  19 , protrusion  43  of cartridge mounting portion  19  may enter recess  62  of ink cartridge  20 A. 
     Subsequently, the distal end of rod member  55   a  of air communication valve element  55  of ink cartridge  20 A may contact end wall  19   a  of cartridge mounting portion  19  and be pushed away from annular sealing member  54 , such that ink chamber  51  of ink cartridge  20 A may be brought into communication with the atmosphere (i.e., air communication opening  52  may be uncovered). When this occurs, referring to  FIG. 7 , pressurized air A in a space between the distal end of protrusion  43  and the bottom of recess  62  may demonstrate a damping effect. More specifically, recess  62  may have a bottomed cylindrical shape, and the cross-sectional area of a gap between the inner peripheral surface of bottomed cylindrical portion  62   a  of recess  62  and the outer peripheral surface of protrusion  43  may be 1/300 to 1/400 of the cross-sectional area of recess  62 , when viewed in a direction in which protrusion  43  enters recess  62 . Therefore, air A between the distal end of protrusion  43  and the bottom of recess  62  may be compressed and pressurized when the mounting speed is sufficiently high, which creates a damping effect. 
     When protrusion  43  enters recess  62  quickly, it may be difficult for air A to escape via the gap between protrusion  43  and recess  62 . As a result, air A may be compressed and pressurized between the distal end of protrusion  43  and the bottom recess  62 , and pressurized air A may cause an increasing resistance. Consequently, a mounting force applied to ink cartridge  20 A by the user when the user mounts ink cartridge  20 A to cartridge mounting portion  19  may be opposed by damper  75 , which comprises recess  62 , protrusion  43 , and pressurized air A. In addition, the greater the mounting speed of ink cartridge  20 A to cartridge mounting portion  19  is, the more difficult it becomes for air to escape through the gap, and the greater the mounting resistance by the pressurized air A may become. Therefore, the amount of the reduction of the mounting speed of ink cartridge  20 A may increase in proportion with an increase of the mounting speed. 
     When protrusion  43  enters recess  62  slowly, however, air A may leak smoothly via the gap between protrusion  43  and recess  62 . As a result, air A between the distal end of protrusion  43  and the bottom of recess  62  may not be very compressed, and the mounting resistance may be small. The mounting resistance of damper  75  may not depend on the position of ink cartridge  20 A with respect to cartridge mounting portion  19 , but may depend only on the mounting speed. Therefore, when the user inserts ink cartridge  20 A into cartridge mounting portion  19  slowly, the user may feel little resistance. 
     Subsequently, referring to  FIGS. 7 and 8 , when ink cartridge  20 A is further pressed toward end wall  19   a , tube  42  may enter ink supply opening  64  and then enter center opening  67   a  of annular sealing member  67  in a liquid-tight manner. Tube  42  also may push ink supply valve element  68  away from annular sealing member  67 , such that ink chamber  51  of ink cartridge  20 A may be brought into communication with ink entry openings  42   b  of tube  42  (i.e., ink supply opening  64  may be uncovered). Air communication valve element  55  and ink supply valve element  68  may be positioned, such that ink supply opening  64  is uncovered after air communication opening  52  is uncovered, when ink cartridge  20 A is mounted to cartridge mounting portion  19 . Even if the mounting operation of ink cartridge  20 A by the user is quick, because the mounting speed is reduced by damper  75 , there may be a sufficient amount of time between the uncovering of air communication opening  52  and the uncovering of ink supply opening  64  for the pressure in the ink chamber to equalize with the atmospheric pressure. Therefore, ink chamber  51  may be brought into communication with ink-jet head  35  after the pressure in ink chamber  51  reaches the atmospheric pressure or reaches a pressure close to the atmospheric pressure, thereby preventing entry of air from the nozzles into ink-jet head  35  due to, for example, a reverse flow of ink from ink-jet head  35  toward ink cartridge  20 A. 
     Referring to  FIG. 9 , an ink cartridge  120 A and a cartridge mounting portion  119  according to another embodiment of the invention is described. In this embodiment, ink cartridge  120 A may not comprise recess  62  formed therein, and cartridge mounting portion  119  may not comprise protrusion  43 . 
     Ink cartridge  120 A may comprise case  150 , which is similar to case  50  of ink cartridge  20 A. An ink supply opening  80  may be formed through a front wall of case  150 . The front wall of case  150  may be positioned at the front of case  150  during the mounting of ink cartridge  120 A to cartridge mounting portion  119 . Ink supply opening  80  may be positioned adjacent to a bottom wall of case  150 . The bottom wall of case  150  may be positioned at the bottom of case  150  during the mounting of ink cartridge  120 A to cartridge mounting portion  119 . Ink supply opening  80 , which is similar to ink supply opening  64  of ink cartridge  20 A, may be tapered at the front end. A recess  81  may encircle ink supply opening  80  and center opening  67   a . Recess  81  may comprise a cylindrical-shaped inner surface of annular sealing member  67 , and a bottom defined by an external surface of ink supply valve element  68 . 
     A tube  142  may extend from an end wall  119   a  of cartridge mounting portion  119  in a manner similar to tube  42 . Tube  142  may have an ink flow path  142   a  formed therein. Ink entry openings  142   b  may be formed through tube  142  extending from ink flow path  142   a  to the outer peripheral surface of tube  142  at a portion adjacent to the distal end of tube  142 . The distal end of tube  142  may be closed by a distal end wall  142   c  of tube  42 . Ink supply tube  21  may be connected to tube  142  outside cartridge mounting portion  119  (not shown in  FIG. 9 ). 
     Referring to  FIGS. 10 and 11 , a mounting operation for mounting the ink cartridge  120 A to cartridge mounting portion  119  is described. Referring to  FIG. 10 , when ink cartridge  120 A is inserted into cartridge mounting portion  119  by a user, the distal end of rod member  55   a  of air communication valve element  55  of ink cartridge  120 A may contact end wall  119   a  of cartridge mounting portion  119  and may be pushed away from annular sealing member  54 , such that ink chamber  51  of ink cartridge  120 A may be brought into communication with the atmosphere (i.e., air communication opening  52  may be uncovered). When air communication opening  52  is uncovered in this manner, distal end wall  142   c  of tube  42  may enter ink supply opening  80  of ink cartridge  120 A, and a damping effect may be caused by contact with pressurized air B in a space formed between distal end wall  142   c  of tube  142  and the bottom of recess  81  (i.e., ink supply valve element  68  may demonstrate a damping effect). More specifically, recess  81  may have a bottomed cylindrical shape, and the cross-sectional area of a gap between ink supply opening  80  and the outer peripheral surface of tube  142  may be 1/300 to 1/400 of the cross-sectional area of ink supply opening  80 , when viewed in a direction in which tube  42  enters ink supply opening  80 . Therefore, air B between distal end wall  142   c  of tube  142  and the bottom of recess  81  may be compressed and pressurized, when tube  142  enters supply opening  80 . Accordingly, recess  81  may function in a manner similar to recess  62 , and tube  142  may function in a manner similar to protrusion  43 . In this manner, the mounting force applied to ink cartridge  120 A by the user when the user mounts ink cartridge  120 A to cartridge mounting portion  119  may be opposed by a damper  175 , which comprises recess  81 , tube  142 , and pressurized air B. As described in reference to previous embodiments, the amount of the reduction of the mounting speed of ink cartridge  120 A may increase in proportion with an increase of the mounting speed. 
     When tube  142  enters ink supply opening  80  slowly, however, air B may leak smoothly via the gap between tube  142  and ink supply opening  80 . As a result, air B between distal end wall  142   c  of tube  142  and the bottom of recess  81  only may be slightly compressed, such that the mounting resistance may be small. Therefore, when the user insert ink cartridge  120 A into cartridge mounting portion  119  slowly, the user may feel little resistance. 
     Subsequently, referring to  FIG. 11 , tube  142  may enter center opening  67   a  of annular sealing member  67  in a liquid-tight manner, and tube  142  may push ink supply valve element  68  away from annular sealing member  67 , such that ink chamber  51  of ink cartridge  120 A may be brought into communication with ink entry openings  142   b  of tube  142  (i.e., ink supply opening  80  may be uncovered). As described above, even if the user tries to insert ink cartridge  120 A into cartridge mounting portion  119  quickly, the mounting speed may be reduced by damper  175  immediately before tube  142  pushes the ink supply valve element  68 . Accordingly, there may be a sufficient amount of time between uncovering air communication opening  52  and uncovering ink supply opening  80  for the pressure in the ink chamber to equalize with the atmospheric pressure. Therefore, ink chamber  51  may be brought into communication with ink-jet head  35  after the pressure in ink chamber  51  reaches the atmospheric pressure or reaches a pressure close to the atmospheric pressure, thereby preventing entry of air from the nozzles into ink-jet head  35  due to, for example, generation of a reverse flow of ink from ink-jet head  35  toward ink cartridge  20 A. Moreover, in this embodiment, the necessity to provide a damper, e.g., damper  75 , in an area other than ink supply opening  80  may be eliminated, thereby making it possible to reduce the size and/or complexity of ink cartridge  120 A and cartridge mounting portion  119 . 
     Referring to  FIG. 12 , a cartridge mounting portion  219  and an ink cartridge  220 A according to yet another embodiment of the invention is described. Ink cartridge  220 A may comprise a liquid damper  94  between ink supply closing mechanism  71  and protrusion  58  at a front wall of case  250  of ink cartridge  220 A. Liquid damper  94  may comprise a cylinder  90  formed integrally with case  250 , a piston  91  positioned in cylinder  90 , liquid  93  (e.g., water or oil stored in cylinder  90 ), and a spring  93 , which urges piston  91  to the front of case  250 . A slight gap may be formed between the outer peripheral surface of piston  91  and the inner peripheral surface of cylinder  90 . Piston  91  may comprise a piston rod  91  a extending from case  250  to the exterior of case  250 . Cartridge mounting portion  119  may comprise a pressing portion  96  extending from an end wall  219   a  of cartridge mounting portion  219  at a position corresponding to liquid damper  94 . 
     Referring to  FIGS. 13 and 14 , a mounting operation for mounting ink cartridge  220 A to cartridge mounting portion  219  is described. Referring to  FIG. 13 , when ink cartridge  220 A is inserted into cartridge mounting portion  219  by a user, the distal end of rod member  55   a  may contact end wall  219   a  of cartridge mounting portion  219  and may be pushed away from annular sealing member  54 , such that ink chamber  51  of ink cartridge  220 A may be brought into communication with the atmosphere (i.e., air communication opening  52  may be uncovered). When air communication opening  52  is uncovered in this manner, pressing portion  96  of cartridge mounting portion  219  may press piston rod  91   a  of ink cartridge  220 A, and a mounting force applied to ink cartridge  220 A by the user may be opposed by liquid damper  94 . Therefore, the amount of reduction of the mounting speed of ink cartridge  220 A may increase in proportion with an increase of the mounting speed. 
     When pressing portion  96  presses piston rod  91   a  slowly, however, liquid  93  may flow smoothly via the gap between the inner peripheral surface of cylinder  90  and outer peripheral surface of piston  91 . As a result, liquid  93  between piston  91  and cylinder  90  may be compressed only slightly, and the mounting resistance may be small. Therefore, when the user inserts ink cartridge  220 A into cartridge mounting portion  219  slowly, the user may feel little resistance. 
     Subsequently, referring to  FIG. 14 , tube  42  may enter ink supply opening  64  and then enter center opening  67   a  of annular sealing member  67  in a liquid-tight manner. Tube  42  may push ink supply valve element  68  away from annular sealing member  67 , such that ink chamber  51  of ink cartridge  220 A may be brought into communication with ink entry openings  42   b  of tube  42  (i.e., ink supply opening  64  may be uncovered). Even if the user tries to mount ink cartridge  220 A to cartridge mounting portion  219  quickly, the mounting speed may be reduced by liquid damper  94  immediately before ink supply opening  64  is uncovered. Accordingly, there may be a sufficient amount of time between uncovering air communication opening  52  and uncovering ink supply opening  64  for the pressure in the ink chamber to equalize with the atmospheric pressure. Therefore, ink chamber  51  may be brought into communication with ink-jet head  35  (see  FIG. 3 ) after the pressure in ink chamber  51  reaches the atmospheric pressure or reaches a pressure close to the atmospheric pressure, thereby preventing entry of air from the nozzles into ink-jet head  35  due to, for example, generation of reverse flow of the ink from the ink-jet head  35  toward the ink cartridge  220 A. 
     Referring to  FIG. 15 , a cartridge mounting portion  319  and an ink cartridge  320 A according to still another embodiment is described. In this embodiment, ink cartridge  320 A may not comprise recess  62  or liquid damper  94 , and cartridge mounting portion  319  may not comprise protrusion  43 . 
     Ink cartridge  320 A may comprise a case  350 . Case  350  may comprise an opening  301  formed through a front wall of case  350 . The front wall of case  350  may be positioned at the front of case  350  during the mounting of ink cartridge  320 A to cartridge mounting portion  319 . Ink cartridge  320 A may comprise an ink supply closing mechanism  371  positioned in opening  301  of case  350 . Ink supply closing mechanism  371  may comprise a tubular sealing member  302  fitted in opening  301  of case  350 . Tubular sealing member  302  may have an ink supply opening  303  formed therethrough. Tubular sealing member  302  may comprise a cylindrical portion  302   a , and a seal lip  302   b  projecting radially inwardly from cylindrical portion  302   a  at a front end of cylindrical portion  302   a . Ink supply closing mechanism  371  may comprise a piston valve  304 , having an H shape when viewed in cross-section. Piston valve  304  may comprise an ink valve element portion  304   a  fitted in tubular sealing member  302 , a piston portion  304   c  stored in a cylinder  305 , and a connecting rod portion  304   b , which connects ink valve element portion  304   a  and piston portion  304   c.    
     Cylinder  305  may be positioned in an ink chamber  351 , such that a center axis of cylinder  305  is aligned with a center axis of tubular sealing member  302  and a gap  307  is formed between cylinder  305  and tubular sealing member  302 . Cylinder  305  may be opened toward tubular sealing member  302  and piston portion  304   c  of piston valve  304  may be positioned therein. A slight gap may be formed between the outer peripheral surface of piston portion  304   c  and inner peripheral surface of the cylinder  305 . Piston valve  304  may be urged by spring  69  to the front of case  350 , and ink valve element portion  304   a  may be tightly fitted in cylindrical portion  302   a , when ink supply opening  303  is covered. Cartridge mounting portion  319  may comprise tube  42  extending from an end wall  319   a.    
     Referring to  FIGS. 16 and 17 , a mounting operation for mounting ink cartridge  320 A to cartridge mounting portion  319  is described. Referring to  FIG. 16 , when ink cartridge  320 A is inserted into cartridge mounting portion  319  by a user, the distal end of rod member  55   a  of air communication valve element  55  of ink cartridge  320 A may be pushed away from annular sealing member  54  by end wall  319   a  of cartridge mounting portion  319  (i.e., air communication opening  52  may be uncovered). When this occurs, tube  42  may enter tubular sealing member  302  in a liquid-tight manner, while tightly contacting seal lip  302   b , and tube  42  may push ink valve element portion  304   a . As a result, piston portion  304   c , which may be formed integrally with ink valve element portion  304   a , may move in cylinder  305 . Ink  100   a  present between piston portion  304   c  and cylinder  305  may be compressed and pressurized, causing a damping effect. 
     More specifically, cylinder  305  has a bottomed cylindrical shape, and the cross-sectional area of a gap between the outer peripheral surface of the piston portion  304   c  and the inner peripheral surface of cylinder  305  may be 1/300 to 1/400 of the cross-sectional area of the interior of cylinder  305 , when viewed in a direction in which piston portion  304   c  moves in cylinder  305 . Accordingly, ink  100   a  in cylinder  305  may be compressed and pressurized by piston portion  304   c , causing a damping effect. Therefore, a damper  375  may comprise cylinder  305 , piston portion  304   c , and ink  100   a  present therebetween. A mounting force applied to ink cartridge  320 A by the user when the user mounts ink cartridge  320 A to cartridge mounting portion  319  may be opposed by damper  375 . Moreover, the amount of reduction of the mounting speed of ink cartridge  320 A may increase in proportion with an increase of the mounting speed. 
     When tube  42  enters ink supply opening  303  slowly, however, ink  100   a  in cylinder  305  may flow out smoothly via the gap between piston portion  304   c  and cylinder  305 , and the mounting resistance may be small. Therefore, when the user inserts ink cartridge  320 A into cartridge mounting portion  319  slowly, the user may feel little resistance. 
     Subsequently, referring to  FIG. 17 , tube  42  may push piston valve  304  inward, such that ink valve element portion  304   a  may pass gap  307  as it moves towards the bottom of cylinder  305 . As a result, ink chamber  351  of ink cartridge  320 A may be brought into communication with ink entry openings  42   b  of tube  42  (i.e., ink supply opening  303  may be uncovered). When ink supply opening  303  is uncovered in this manner, even if the user tries to mount ink cartridge  320 A to cartridge mounting portion  319  quickly, the mounting speed may be reduced by damper  375  immediately before ink supply opening  303  is uncovered and ink chamber  315  is bought into communication with ink entry openings  42   b  of tube  42 . Accordingly, there may be a sufficient amount of time between uncovering air communication opening  52  and uncovering ink supply opening  303  for the pressure in the ink chamber to equalize with the atmospheric pressure. Therefore, ink chamber  351  may be brought into communication with ink-jet head  35  after the pressure in ink chamber  351  reaches the atmospheric pressure or reaches a pressure close to the atmospheric pressure, thereby preventing entry of air from the nozzles into ink-jet head  35  due to, for example, generation of reverse flow of ink from ink-jet head  35  toward ink cartridge  320 A. In this embodiment, a damper, e.g., damper  75  or liquid damper  94 , in an area other than ink supply closing mechanism  371  may be eliminated, making it possible to reduce the size and/or complexity of ink cartridge  320 A and cartridge mounting portion  319 . 
     Although several embodiments of the invention have been described, the invention is not limited to the above-described embodiments. For example, recess  62  may be formed in end wall  19   a  of cartridge mounting portion  19 , and protrusion  43  may be provided on case  50  of an ink cartridge. Liquid damper  94  may be provided on cartridge mounting portion  219 , and pressing portion  96 , which presses piston rod  91   a , may be provided on casing  250  of ink cartridge  220 A. In such an embodiment, ink cartridge  220 A may be formed inexpensively. Also, when damper  75  or liquid  94  are provided independently from ink supply opening  64  and ink supply closing mechanism  71 , ink supply closing mechanism  71  may not be configured selectively cover and uncover ink supply opening  64  by ink supply valve element  68 . Instead, a film or covering, e.g., a sticker, which cannot be closed again after it is opened once by the penetration of tube  42  therethrough, may be used as ink supply closing mechanism  71 . Although several embodiments described above are invention described in relation to an ink-jet printer, the invention may be applied to other devices, e.g., a liquid droplet discharging apparatus for manufacturing color filters of liquid crystal display devices by discharging liquid other than ink (for example, colored liquid), or an apparatus for forming electrical wirings by discharging conductive liquid. 
     While the invention has been described in connection with various exemplary structures and illustrative embodiments, it will be understood by those skilled in the art that other variations and modifications of the structures and embodiments described above may be made without departing from the scope of the invention. Other structures and embodiments will be apparent to those skilled in the art from a consideration of the specification or practice of the invention disclosed herein. It is intended that the specification and the described examples are illustrative with the true scope of the invention being defined by the following claims.