Patent Publication Number: US-8991990-B2

Title: Liquid cartridge having valve for opening and closing air flow path

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority from Japanese Patent Application Nos. 2013-069546 filed Mar. 28, 2013, 2013-069557 filed Mar. 28, 2013 and 2013-069562 filed Mar. 28, 2013. The entire contents of these priority applications are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to a liquid cartridge provided with a liquid chamber and an air flow path configured to permit the liquid chamber to communicate with ambient air to bring pressure of the liquid chamber into atmospheric pressure. 
     BACKGROUND 
     There is known an image recording apparatus that uses ink to record an image onto a recording sheet. This image recording apparatus includes an inkjet type recording head and is configured to selectively spray ink droplets from the recording head toward a recording sheet. The ink droplets are landed onto the recording sheet, thereby a desired image being recorded on the recording sheet. The image recording apparatus can accommodate an ink cartridge having an ink chamber that stores ink to be supplied to the recording head. The ink cartridge is detachably received in an accommodating portion provided in the image recording apparatus. 
     The ink cartridge to be accommodated in the image recording apparatus is internally sealed, before use, so as to prevent ink stored in the ink chamber from leaking outside. The ink chamber is brought into atmospheric pressure when used. To this end, the ink cartridge is provided with an air flow path through which the ink chamber is permitted to communicate with ambient air. Conventionally, a valve mechanism has been provided in the air flow path for opening and closing the same, for example. Japanese Patent Application Publication Nos. 2005-161641 and 2005-111922 disclose such a conventional valve system provided in the ink cartridge. 
     SUMMARY 
     Conceivably, various valve mechanisms can be provided in the air flow path for preventing ink leakage therefrom and for achieving enhanced operability to open and close the air flow path. In any event, it is preferable that such valve mechanism be simple and compact. 
     In view of the foregoing, it is an object of the present invention to provide a simple and compact valve structure for opening and closing an air flow path provided in an ink cartridge. 
     In order to attain the above and other objects, the present invention provides a liquid cartridge including a cartridge body, a liquid supply portion provided at the cartridge body, an air flow path provided in the cartridge body, and a valve configured to open and close the air flow path. The cartridge body defines a liquid chamber therein for storing liquid. The liquid supply portion is configured to supply the liquid stored in the liquid chamber to outside. The air flow path is configured to be in communication with the liquid chamber through a communication hole and in communication with ambient air to permit the liquid chamber to communicate with ambient air through the air flow path, the air flow path having an inner peripheral wall defining an internal space therein. The valve includes a valve main body and a sealing member provided on the valve main body. The valve main body is disposed in the internal space and slidable in a sliding direction. The sealing member includes: a first elastic portion configured to seal the communication hole; and a second elastic portion configured to be in contact with and in sliding contact with the inner peripheral wall. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a conceptual cross-sectional view showing an internal construction of a printer provided with an cartridge accommodating section that detachably accommodates an ink cartridge according to an embodiment of the present invention; 
         FIG. 2  is a perspective view showing an external appearance of the ink cartridge according to the embodiment, wherein a release member is assembled to the ink cartridge; 
         FIG. 3  is a perspective view showing the external appearance of the ink cartridge according to the embodiment, wherein the release member has been removed from the ink cartridge; 
         FIG. 4  is an exploded side view showing an internal structure of the ink cartridge according to the embodiment; 
         FIG. 5  is a vertical cross-sectional view showing the internal structure of the ink cartridge according to the embodiment, wherein the release member has been assembled to the ink cartridge; 
         FIG. 6  is an enlarged view of an essential portion of the ink cartridge enclosed by a rectangle shown in  FIG. 5 , the essential portion including a valve chamber and a valve disposed within the valve chamber; 
         FIG. 7  is an enlarged cross-sectional view of the essential portion of the ink cartridge of the embodiment taken along a plane VII-VII shown in  FIG. 5 , wherein the valve is in a first position; 
         FIG. 8  is an enlarged cross-sectional view of the essential portion of the ink cartridge of the embodiment taken along the plane VII-VII shown in  FIG. 5 , wherein the valve is in a second position; 
         FIG. 9  is a perspective view showing an external appearance of the valve according to the embodiment; 
         FIG. 10  is an exploded view of the valve according to the embodiment; 
         FIG. 11  is an enlarged cross-sectional view showing an area within and in the vicinity of the valve chamber when the ink cartridge according to the embodiment is placed with its left side surface facing downward; and 
         FIG. 12  is an enlarged cross-sectional view showing the area within and in the vicinity of the valve chamber when the ink cartridge according to the embodiment is placed with its right side surface facing downward. 
     
    
    
     DETAILED DESCRIPTION 
     1. Overall Structure of Printer 
     First, a printer  10  adapted to accommodate the ink cartridge  30  according to an embodiment of the present invention will be described with reference to  FIG. 1 . 
     The printer  10  is configured to form an image by ejecting ink droplets onto a sheet in accordance with an ink jet recording system. As shown in  FIG. 1 , the printer  10  includes an ink supply device  100  provided with a cartridge accommodating section  110  configured to detachably accommodate the ink cartridge  30  therein. The printer  10  also includes a recording head  21  and ink tubes  21  connecting the ink supplying device  100  and the recording head  21 . 
     The cartridge accommodating section  110  has one side formed with an opening  112  exposed to an atmosphere. The ink cartridge  30  can be inserted into and removed from the cartridge accommodating section  110  through the opening  112 . 
     The ink cartridge  30  stores therein an ink to be used in the printer  10 . The ink cartridge  30  is connected to the recording head  21  through the corresponding ink tube  20  when the ink cartridge  30  is mounted in the cartridge accommodating section  110 . The recording head  21  has a sub tank  28  in which the ink supplied from the ink cartridge  30  through the ink tube  20  is temporarily stored. The recording head  21  also includes a plurality of nozzles  29  through which ink supplied from the sub tank  28  is selectively ejected in accordance with the ink jet recording system. 
     The printer  10  also includes a sheet supply tray  15 , a sheet supply roller  23 , a sheet path  24 , a pair of transfer rollers  25 , a platen  26 , a pair of discharge rollers  22 , and a discharge tray  16 . A sheet of paper is supplied from the sheet supply tray  15  to the sheet passage  24  by the sheet supply roller  23 , and is then conveyed to the platen  26  by the pair of transfer rollers  25 . Then, the ink is selectively ejected from the recording head  21  onto the sheet passing through the platen  26  to form an inked image on the sheet. The sheet is then discharged onto the discharge tray  16  by the pair of discharge rollers  22 . 
     2. Ink Supply Device 
     The ink supply device  100  functions to supply ink to the recording head  21 , as shown in  FIG. 1 . As described above, the ink supply device  100  includes the cartridge accommodating section  110  in which the ink cartridge  30  is detachable loadable. 
       FIG. 1  shows a state where the ink cartridge  30  has been loaded in the cartridge accommodating section  110 . In the printer  10  of the present embodiment, the cartridge accommodating section  110  is configured to accommodate four kinds of ink cartridges  30  corresponding to four colors of cyan, magenta, yellow and black, respectively. However, for explanatory purpose,  FIG. 1  depicts the cartridge accommodating section  110  that has accommodated only one ink cartridge  30  therein. 
     The ink cartridge  30  is mounted in and removed from the cartridge accommodating section  110  in an upstanding posture shown in  FIGS. 2 to 3 . Specifically, the ink cartridge  30  is loaded into the cartridge accommodating section  110  in a loading direction  56 , and is unloaded from the cartridge accommodating section  110  in an unloading direction  55  while maintaining the upstanding posture. Hereinafter, the loading direction  56  and the unloading direction  55  may be collectively referred to as a loading/unloading direction  50 , whenever necessary, assuming that the loading direction  56  and the unloading direction  55  are interchangeable with each other. 
     The cartridge accommodating section  110  includes a case  101 , an engaging member  145 , an ink needle  113  and an optical sensor  114 . 
     The case  101  defines an outer shape of the cartridge accommodating section  110 . The ink cartridge  30  is accommodated in the case  101 . The case  101  has an end wall opposite the opening  112 . 
     The ink needle  113  is tubular shaped and is formed of a resin. The ink needle  113  is connected to the ink tube  20 . The ink needle  113  is disposed at a lower end portion of the end wall of the case  101  to correspond to an ink supply portion  34  (described later) of the ink cartridge  30  mounted in the cartridge accommodating section  110 . The ink needle  113  is inserted into an ink supply outlet  71  of the ink supply portion  34  (see  FIGS. 2 to 3 ) when the ink cartridge  30  is being mounted in the cartridge accommodating section  110 , thereby opening an ink supply valve  70  provided in the ink supply portion  34 . As a result, the ink stored in an ink chamber  36  of the ink cartridge  30  is flowed out therefrom, through an ink passage  72  formed in the ink supply portion  34 , into the ink tube  20  connected to the ink needle  113 . 
     The optical sensor  114  is provided on the end wall of the case  101  at a position upward of the ink needle  113  in a gravity direction. The optical sensor  114  includes a light-emitting element (LED, for example) and a light-receiving element (phototransistor, for example). The optical sensor  114  has a horseshoe-shaped housing. The light-emitting element and the light-receiving element are disposed respectively on distal end portions of the horseshoe-shaped housing of the optical sensor  114  to oppose each other. In the present embodiment, the light-emitting element is configured to emit light in a horizontal direction (perpendicular to the loading/unloading direction  50 ) and the light-receiving element is configured to receive the light emitted from the light-emitting element. The light-emitting element and the light-receiving element define a space therebetween into which a detecting portion  33  of the ink cartridge  30  enters when the ink cartridge  30  is loaded into the cartridge accommodating section  110 , as will be described later. When entering this space, the detecting portion  33  alters a path of light formed between the light-emitting element and the light-receiving element, thereby enabling the optical sensor  114  to detect changes in amount of light received by the light-receiving element. 
     Further, as shown in  FIG. 1 , the engaging member  145  is provided on an upper wall of the casing  101  at a position adjacent to the opening  112 . Four engaging members  145  are provided for receiving four ink cartridges  30  in the present embodiment, but for explanatory purpose, only one engaging member  145  is depicted in  FIG. 1 . The engaging member  145  is configured to pivot about a shaft  147  provided near the opening  112  on the upper wall. When the ink cartridge  30  is mounted in the cartridge accommodating section  110 , the engaging member  145  is configured to engage an engaging portion  45  of the ink cartridge  30  to keep the ink cartridge  30  mounted in the cartridge accommodating section  110  against a biasing force acting in the unloading direction  55 , as will be described later. 
     For removing the ink cartridge  30  from the cartridge accommodating section  110 , a user pushes down a rear end portion of a pivot member  80  (described later) provided on the ink cartridge  30  to cause the engaging member  145  to pivotally move counterclockwise. The engagement between the engaging member  145  and the engaging portion  45  is thus released by the pivotal movement of the pivot member  80 , thereby permitting the ink cartridge  30  from being removed from the cartridge accommodating section  110 . 
     3. Ink Cartridge 
     The ink cartridge  30  is a container configured to store ink therein. The ink cartridge  30  includes a cartridge body  31 , a bracket  90 , an inner frame  35  accommodated in the cartridge body  31 , and a release member  130 , as shown in  FIGS. 2 to 4 . 
     The ink cartridge  30  defines therein a space for storing ink and this space serves as the ink chamber  36 . In the present embodiment, the ink chamber  36  is formed by the inner frame  35  accommodated in the cartridge body  31  and a pair of films  82  (see  FIG. 1 ) attached to the inner frame  35 . Alternatively, the ink chamber  36  may be defined by the cartridge body  31  itself. 
     The bracket  90  is assembled to the cartridge body  31  to form an outer shape of the ink cartridge  30 . The inner frame  35  is housed within the cartridge body  31  and the bracket  90  assembled to each other. 
     In an assembled state, the ink cartridge  30  has a generally flat rectangular parallelepiped shape in outer appearance. The ink cartridge  30  has a width (in a direction indicated by an arrow  51  which will be referred to as widthwise direction), a height (in a direction indicated by an arrow  52  which will be referred to as height direction or vertical direction) and a depth (in a direction indicated by an arrow  53  which will be referred to as depthwise direction), the height and depth being greater than the width. In other words, side surfaces opposing each other in the widthwise direction  51  are surfaces with a largest area among surfaces constituting the ink cartridge  30 . 
     The loading/unloading direction  50  of the ink cartridge  30  relative to the cartridge accommodating section  110  is coincident with the horizontal direction, or the depthwise direction  53  in the present embodiment. However, loading and unloading of the ink cartridge  30  relative to the cartridge accommodating section  110  may be performed in a direction parallel to a vertical direction, or a direction intersecting with both of the vertical and horizontal directions. 
     Hereinafter, whenever necessary, directions with respect to the ink cartridge  30  will be defined based on the upstanding posture shown in  FIG. 2 . That is, a leading side of the ink cartridge  30  in the loading direction  56  is referred to as the front side of the ink cartridge  30 , whereas a trailing side of the ink cartridge  30  in the unloading direction  55  is referred to as the rear side of the ink cartridge  30 . Specifically, the side at which the ink supply portion  34  is provided is the front side of the ink cartridge  30 , whereas the side opposite to the side at which the ink supply portion  34  is provided in the depthwise direction  53  is the rear side of the ink cartridge  30 . The front-rear direction is thus coincident with the depthwise direction  53  in the present embodiment. 
     (3-1) Cartridge Body 
     The cartridge body  31  is box-like shaped to have a hollow space defined therein for housing the inner frame  35 . The cartridge body  31  includes a pair of side walls  37  and  38  opposed to each other in the widthwise direction  51  (the side wall  37  is not shown in drawings), and upper and lower walls  27  and  41  opposed to each other in the height direction  52 . The cartridge body  31  also includes a rear wall  42  that serves as a trailing end of the ink cartridge  30  in the loading direction  56 . The four walls  37 ,  38 ,  27 , and  41  extend from the rear wall  42  in the depthwise direction  53 . The cartridge body  31  is also formed with an open surface opposed to the rear wall  42  in the depthwise direction  53 . The inner frame  35  is inserted into the space formed inside the cartridge body  31  through this open surface. When the inner frame  35  is accommodated in the cartridge body  31 , the inner frame  35  is partially exposed from the cartridge body  31 . That is, the cartridge body  31  covers a rear portion of the inner frame  35 . 
     As illustrated in  FIG. 1 , the pivot member  80  is provided on the upper wall  27  of the cartridge body  31 . The pivot member  80  has a bent plate-like shape and is disposed to extend in the depthwise direction  53 . The pivot member  80  has a bent portion in which a pivot shaft (not illustrated) is provided. The pivot member  80  is configured to pivot about this pivot shaft. The pivot member  80  has a portion extending from the bent portion toward an engaging surface  46  (described later) formed in the engaging portion  45  of the cartridge body  31 , and another portion extending from the bent portion toward the rear wall  42 . That is, the pivot member  80  is configured of a portion frontward of the pivot shaft (frontward portion) and another portion rearward of the pivot shaft (rearward portion). When the ink cartridge  30  is loaded in the cartridge accommodating section  110 , the frontward portion of the pivot member  80  is positioned below the engaging member  145 . The rearward portion of the pivot member  80  is pressed down by a user when the ink cartridge  30  is removed from the cartridge accommodating section  110  to release the engagement between the engaging member  145  and the engaging portion  45 . 
     (3-2) Bracket 
     The bracket  90  has a box-like shape and is configured of a pair of side walls  143  and  144  opposed to each other in the widthwise direction  51  (the side wall  143  is not shown in the drawings), and upper and lower walls  141  and  142  opposed to each other in the height direction  52 . The bracket  90  also has a front wall  140  that opposes the rear wall  42  of the cartridge body  31  in the depthwise direction  53  when the bracket  90  is assembled to the cartridge body  31 . This front wall  140  serves as a leading end of the ink cartridge  30  when the ink cartridge  30  is being mounted in the cartridge accommodating section  110  in the loading direction  56 . The four walls  143 ,  144 ,  141 , and  142  extend from the front wall  140  in the depthwise direction  53 . The bracket  90  also has an open surface that opposes the front wall  140  in the depthwise direction  53  when the bracket  90  is assembled to the cartridge body  31 . The inner frame  35  is inserted inside the bracket  90  through this open surface. That is, the bracket  90  covers a front portion of the inner frame  35  that is not covered by the cartridge body  31 . 
     When the bracket  90  is assembled to the cartridge body  31 , the upper wall  141  of the bracket  90  and the upper wall  27  of the cartridge body  31  are in continuous with each other to constitute an upper wall of the ink cartridge  30 . Similarly, the lower wall  142  of the bracket  90  and the lower wall  41  of the cartridge body  31  are in continuous with each other to constitute a lower wall of the ink cartridge  30 . The side walls  143  and  144  of the bracket  90  and the side walls  37  and  38  of the cartridge body  31  constitute side walls of the ink cartridge  30 , respectively. Further, in the assembled state of the ink cartridge  30 , the front wall  140  of the bracket  90  constitutes a front wall of the ink cartridge  30  and the rear wall  42  of the cartridge body  31  constitutes a rear wall of the ink cartridge  30 . 
     In the present embodiment, the direction in which the front and rear walls of the ink cartridge  30  (front wall  140  and rear wall  42 ) oppose each other (i.e., depthwise direction  53 ) is the front-rear direction (horizontal direction) and coincides with the loading/unloading direction  50 . Thus, the direction in which the upper and lower walls of the ink cartridge  30  (upper walls  141 ,  39  and lower walls  142 ,  41 ) oppose each other (i.e., height direction  52 ) is coincident with the vertical direction (gravity direction). 
     A through-hole  95  is formed in the bracket  90  to penetrate each of the side walls  143  and  144  in the widthwise direction  51  at a position substantially center in the height direction  52  and adjacent to the front wall  140 . The through-hole  95  functions to expose the detecting portion  33  of the inner frame  35  when the inner frame  35  is accommodated in the bracket  90 . Thus, the through-hole  95  is formed so as to correspond to the detection portion  33  of the inner frame  35  in terms of position, dimension, and shape. 
     An elongated hole  91  is also formed in a lower end portion of each of the side walls  143 ,  144  of the bracket  90 . When the bracket  90  is assembled to the cartridge body  31  in which the inner frame  35  has been accommodated, these elongated holes  91  are configured to engage with engagement claws  43  provided on the inner frame  35 . 
     The front wall  140  is formed with a hole  96  at a position upward of the through-hole  95  in the height direction  52 . The hole  96  penetrates the front wall  140  in the depthwise direction  53 . In a state where the bracket  90  is assembled to the cartridge body  31 , the hole  96  serves to receive the release member  130  functioning to open a sealed air communication portion  120  formed in the inner frame  35 , as will be described later. When the bracket  90  is assembled to the cartridge body  31  as shown in  FIG. 2 , the hole  96  is positioned frontward of a protruding end of the ink supply portion  34  in the front-rear direction (depthwise direction  53 ), as will be described later. 
     On a peripheral wall defining the hole  96 , a pair of cutouts  136  is formed to extend radially outward from the hole  96 . Specifically, the cutouts  136  are positioned to diametrically oppose each other via the hole  96  in the widthwise direction  51 . 
     The front wall  140  is also formed with a hole  97  at a position below the through-hole  95  with respect to the height direction  52 . The hole  97  penetrates the front wall  140  in the depthwise direction  53 . When the bracket  90  is assembled to the cartridge body  31 , the ink supply portion  34  of the inner frame  35  is exposed outside through the hole  97 . Thus, the hole  97  is formed so as to correspond to the ink supply portion  34  of the inner frame  35  in terms of position, dimension, and shape. The hole  97  is positioned rearward of the hole  96  in the front-rear direction (the depthwise direction  53 ). 
     The front wall  140  is provided with a first protrusion  85  and a second protrusion  86 . As shown in  FIGS. 2 to 4 , the first protrusion  85  is formed at an upper end portion of the front wall  140  so as to protrude therefrom in a direction away from the front wall  140  (i.e., frontward, or in the loading direction  56 ). The hole  96  is formed on a protruding end of the first protrusion  85 . The second protrusion  86  is formed at a lower end portion of the front wall  140  so as to protrude therefrom in a direction away from the front wall  140  (i.e., frontward, or in the loading direction  56 ). The hole  97  is positioned between the through-hole  95  and the second protrusion  86  with respect to the height direction  52 . 
     The upper wall  141  of bracket  90  is formed with an opening  89  (see  FIG. 6 ) penetrating the upper wall  141  in the height direction  52 . Referring to  FIG. 6 , in the state wherein the inner frame  35  has been inserted in the bracket  90 , the opening  89  serves to expose an air communication port  125  (described later) formed in the inner frame  35  to atmosphere, as will be described later. Thus, the opening  89  is formed so as to correspond to the air communication port  125  of the inner frame  35  in terms of position, dimension, and shape. Specifically, the opening  89  has a diameter larger than that of the air communication port  125 . The opening  89  is positioned to be spaced away from the air communication port  125  but is aligned with the air communication port  125  in the height direction  52 . 
     A supporting portion  88  is formed adjacent to the opening  89  on the upper wall  141 . The supporting portion  88  is adapted to receive a memory chip  81  having a rectangular flat plate-like shape. Specifically, the supporting portion  88  has a claw-like shape to be engaged with a peripheral end of the memory chip  81 . When the memory chip  81  is coupled to the supporting portion  88 , the opening  89  is closed by (covered with) the memory chip  81 . Instead of the claw-like shape, the supporting portion  88  may be formed as a surface to which an adhesive tape can be attached for fixing a back side of the memory chip  81 . Or the memory chip  81  may be fixed to the supporting portion  88  by melting a boss-shaped resin. 
     The memory chip  81  is a flat plate-shaped substrate having a top surface on which electrodes (shown without reference numerals) are disposed. The memory chip  81  also includes an IC configured to store various electrical signals. More specifically, the IC is configured to store various information on the ink cartridge  30  as electrical signals: for example, information on a type of the ink cartridge  30 , such as an ink color, ink component, and initial amount of ink stored in the ink chamber  36 . 
     The electrodes of the memory chip  81  are exposed upward to allow electrical connection thereto by an external access. When the ink cartridge  30  is mounted in the cartridge accommodating section  110 , electrical contacts  106  ( FIG. 1 ) provided on the cartridge accommodating section  110  electrically contact the electrodes to achieve power supply to the memory chip  81 , thereby enabling the information stored in the IC to be retrieved therefrom. 
     (3-3) Inner Frame 
     As shown in  FIGS. 3 and 4 , the inner frame  35  is formed in a rectangular ring-like shape (or frame-like shape) whose pair of surfaces opposed to each other in the widthwise direction  51  are partially open. Each of the opened surfaces is sealed by the film  82  (see  FIG. 1 ) to form the ink chamber  36  in the inner frame  35  for storing ink. 
     The ink chamber  36  is a space configured to store ink in a free state. Storing ink in a free state means that ink is freely movably stored within the ink chamber  36  without resisting gravity. This is contrast to a state where ink is absorbed and retained in a three-dimensional mesh-structured material, such as a sponge or foam, against gravity. 
     The inner frame  35  has a front wall  40  serving to partially define the ink chamber  36 . The front wall  40  opposes the front wall  140  of the bracket  90  in the depthwise direction  53  when the inner frame  35  is inserted in the bracket  90 . The inner frame  35  is provided with the detection portion  33 , the ink supply portion  34 , the air communication portion  120 , and a valve chamber  32 . 
     The detecting portion  33  protrudes frontward (in the loading direction  56 ) from the front wall  40  at a generally intermediate position in the height direction  52 . The detecting portion  33  has a box-like shape whose one end is open so as to allow the ink in the ink chamber  36  to be in fluid communication with the detecting portion  33  via the open end. The detecting portion  33  is exposed outside of the bracket  90  through the through-hole  95  when the bracket  90  is assembled to the cartridge body  31 . The detecting portion  33  has a pair of side walls made from a light transmissive resin. In the present embodiment, these side walls are configured to allow the light emitted from the optical sensor  114  ( FIG. 1 ) to pass therethrough in the direction perpendicular to the loading/unloading direction  50  (i.e., the widthwise direction  51  or horizontal direction). The light may be infrared light or visible light. 
     The detecting portion  33  provides therein a hollow space between the pair of side walls such that ink can be present therebetween. Within this hollow space, an indicator  62  of a sensor arm  60  is movably positioned, as shown in  FIG. 1 . 
     The sensor arm  60  is pivotably movably provided in the ink chamber  36 . The sensor arm  60  includes an arm body  61  and a pivot shaft  64 . The arm body  61  is plate-like shaped, and is pivotally movably supported to the pivot shaft  64 . The pivot shaft  64  extends in the widthwise direction  51  and is supported to the inner frame  35 . The arm body  61  has one free end provided with the indicator  62  movably positioned in the hollow space of the detecting portion  33 , and another free end provided with a float  63  dipped in the ink. With this structure, the sensor arm  60  is adapted to change its pivoting posture in accordance with an amount of the ink in the ink chamber  36  between a lower position in which the indicator  62  approaches a lower wall of the detecting portion  33  and an upper position in which the indicator  62  approaches an upper wall of the detecting portion  33 . In  FIGS. 4 and 5 , the sensor arm  60  is omitted. 
     With this structure, when the ink cartridge  30  is mounted in the cartridge accommodating section  110 , the detecting portion  33  can change its light transmission state between a transmissive state and a non-transmissive state. In the transmissive state, not less than a predetermined amount of infrared light from the optical sensor  114  can be transmitted through the detecting portion  33  as the sensor arm  60  is at the upper position, and in the non-transmisive state, less than the predetermined amount of infrared light is transmitted therethrough (i.e., the light may be shut off or attenuated) as the sensor arm  60  is at the lower position. In accordance with the light transmission state at the detecting portion  33 , the printer  10  can detect whether the amount of ink in the ink chamber  36  is less than the prescribed amount. 
     As shown in  FIG. 4 , the ink supply portion  34  is provided at the front wall  40  below the detecting portion  33 . The ink supply portion  34  has a hollow cylindrical shape protruding from the front wall  40  in the loading direction  56 , i.e., frontward in the front-rear direction. The ink supply portion  34  is exposed outside through the hole  97  formed in the bracket  90  when the ink cartridge  30  is assembled. 
     The ink supply portion  34  has a protruding end in which the ink supply outlet  71  is formed. As shown in  FIG. 1 , the ink passage  72  is formed inside the ink supply portion  34 . The ink passage  72  extends in the depthwise direction  53  so as to permit fluid communication between the ink supply outlet  71  and the ink chamber  36  through the ink passage  72 . The ink supply valve  70  is disposed in the ink passage  72  to open and close the ink supply outlet  71 . 
     Upon loading of the ink cartridge  30  into the cartridge accommodating section  110 , the ink needle  113  is inserted into the ink supply outlet  71 . The ink needle  113  moves the ink supply valve  70  rearward in the front-rear direction to open the ink supply outlet  71 . Thus, the ink in the ink chamber  36  is permitted to flow into the ink needle  113  via the ink passage  72 . In the present embodiment, the ink flows out in a direction generally coincident with the loading direction  56  (or frontward in the front-rear direction). 
     Instead of the ink supply valve  70 , a film covering the ink supply outlet  71  may be provided. In the latter case, the ink needle  113  breaks the film to open the ink supply outlet  71  upon loading of the ink cartridge  30  into the cartridge accommodating section  110 . 
     As illustrated in  FIG. 4 , a pair of engagement claws  43  is formed at a lower end portion of the front wall  40  of the inner frame  35 . Each engagement claw  43  has a distal end portion that protrudes outward in the widthwise direction  51 . The engagement claws  43  define a distance therebetween in the widthwise direction  51  such that the engagement claws  43  can resiliently deform inward in the widthwise direction  51 . Upon assembly of the bracket  90  to the cartridge body  31  and the inner frame  35 , the distal end portions of the engagement claws  43  respectively enter the pair of elongated holes  91  formed in the bracket  90  and engage inner peripheral surfaces of cylindrical inner walls constituting the elongated holes  91 . 
     The inner frame  35  has an upper wall  39  in which the engaging portion  45  is formed. The engaging portion  45  includes the engaging surface  46  extending in the widthwise direction  51  and the height direction  52 . The engaging surface  46  is configured to engage the engaging member  145  of the cartridge accommodating section  110  when the ink cartridge  30  has been loaded in the cartridge accommodating section  110 . When engaged with the engaging member  145 , the engaging portion  45  (engaging surface  46 ) is adapted to receive (resist) a biasing force acting in the unloading direction  55  to keep the ink cartridge  30  mounted in the cartridge accommodating section  110 , the biasing force being generated by the ink supply valve  70  pushing the ink needle  113 . 
     The air communication portion  120  is formed in the inner frame  35  at a position higher than the detection portion  33  in the height direction  52 , as shown in  FIGS. 4 and 5 . The air communication portion  120  is configured to allow the ink chamber  36  to communicate with outside of the ink cartridge  30 . 
     The air communication portion  120  includes an air flow path through which the ink chamber  36  is permitted to communicate with outside. The air communication portion  120  also includes a valve  48 , and a coil spring  49  biasing the valve  48 . 
     The air flow path is formed between the ink chamber  36  and outside of the ink cartridge  30  in the inner frame  35 . Specifically, the air flow path connects between a communication hole  44  (see  FIG. 6 ) in communication with the ink chamber  36  and the air communication port  125  in communication with atmosphere. 
     The air communication port  125  is formed on the upper wall  39  at a position frontward of the engaging portion  45  to oppose a back surface of the memory chip  81 , as shown in  FIG. 6 . The air communication port  125  is open on the upper wall  39  and is in communication with an air path  128  (described later) in the height direction  52 . As shown in  FIG. 2 , since the air communication port  125  is covered with the bracket  90  and the memory chip  81  in the assembled ink cartridge  30 , a user cannot visually confirm the air communication port  125  from outside. However, the air communication port  125  is in communication with atmosphere (outside of the ink cartridge  30 ) through minute gaps formed between the bracket  90  and the inner frame  35 , for example. 
     The communication hole  44  is a hole formed in a partition wall  121  that partitions between the valve chamber  32  and the ink chamber  36 , as shown in  FIG. 6 . Specifically, the communication hole  44  is positioned in a center of the partition wall  121  in the widthwise direction  51 . The communication hole  44  is defined by an inner peripheral wall  129  to penetrate the partition wall  121  in the depthwise direction  53 . The valve chamber  32  is a space formed in the inner frame  35  to receive the valve  48 . The valve chamber  32  is thus communicable with the ink chamber  36  via the communication hole  44 . As shown in  FIGS. 5 and 6 , the valve chamber  32  is defined by a cylindrical-shaped peripheral wall  119  extending from the partition wall  121  toward the front wall  40  in the depthwise direction  53 . The valve chamber  32  thus has an open end near the front wall  40 , the open end being opposite to the partition wall  121  in the depthwise direction  53 . The communication hole  44  is positioned on an axis of the cylindrical-shaped valve chamber  32  that is coincident with the depthwise direction  53 . In other words, the communication hole  44  is positioned on a center in the widthwise direction  51  and in the height direction  52 . The peripheral wall  119  defining the valve chamber  32  is formed with a through-hole  122  (see  FIGS. 4 and 8 ) extending to a left wall  123  of the inner frame  35 . That is, the through-hole  122  is open on the left wall  123 . 
     The left wall  123  of the inner frame  35  is formed with a winding labyrinth path  124 , as shown in  FIG. 4 . Specifically, the labyrinth path  124  is a space defined by grooves formed in the left wall  123  and the film  82  attached to the left wall  123 . As shown in  FIG. 4 , the labyrinth path  124  is formed to be aligned with the valve chamber  32  in the widthwise direction  51 . 
     The labyrinth path  124  has one end communicating with the through-hole  122 , and another end communicating with the air path  128 . Specifically, the labyrinth path  124  extends from the through-hole  122  generally rearward, and approaches the upper wall  39  while making U-turns and extending in the depthwise direction  53 . Reaching near the upper wall  39 , the labyrinth path  124  then extends linearly frontward and finally reaches a through-hole  127  formed in the left wall  123 . The through-hole  127  is in communication with the air path  128  that is in communication with the air communication port  125 . The air path  128  penetrates the left wall  123  in the widthwise direction  51 , extends to the upper wall  39  and penetrates therethrough to be in communication with the air communication port  125 . 
     In this way, the ink chamber  36  can be in communication with atmosphere via the communication hole  44 , the valve chamber  32 , the through-hole  122 , the labyrinth path  124 , the through-hole  127 , the air path  128 , and the air communication port  125 . This path for achieving air flow between the ink chamber  36  and outside of the ink cartridge  30  is defined as the air flow path formed in the air communication portion  120 . 
     In the inner frame  35 , a pair of engaging claws  126  is formed frontward of the valve chamber  32  near the front wall  40 . Specifically, the engaging claws  126  are formed adjacent to the open end of the valve chamber  32  to protrude radially inward of the same. The engaging claws  126  are spaced away from each other in the height direction  52 . The engaging claws  126  are adapted to engage with a pair of engaging claws  74  formed on the valve  48  so that the valve  48  is prevented from being popped out from the valve chamber  32  due to a biasing force of the coil spring  49 . 
     The valve  48  is movably disposed within the valve chamber  32 . Specifically, the valve  48  is movable in the front-rear direction between a first position shown in  FIGS. 6 and 7  and a second position shown in  FIG. 8 . The valve  48  closes the communication hole  44  at the first position, and opens the communication hole  44  at the second position, as will be described in detail later. 
     As shown in  FIGS. 6 through 10 , the valve  48  includes a valve main body  75 , a sealing member  76 , and an O-ring  99 . 
     The valve main body  75  has an outer profile in conformance with the cylindrical-shaped valve chamber  32  so as to be inserted into the same. The valve main body  75  has a generally columnar shape elongated in the depthwise direction  53  and defining an axis extending in the depthwise direction  53 . The valve main body  75  has an outer diameter smaller than an inner diameter of the valve chamber  32 . Note that, referring to  FIGS. 9 and 10 , the valve main body  75  is not actually columnar shaped as a whole, but has an outer contour of a generally columnar shape. The outer contour of the valve main body  75  is formed by various end faces, including end faces of cross-shaped ribs extending radially outward from an axial center portion of the valve main body  75 . 
     The valve main body  75  is formed with a first opening  83 , a second opening  84 , and an air passage  77  connecting between the first opening  83  and the second opening  84 , as shown in  FIGS. 9 and 10 . 
     The valve main body  75  has an end face  78  configured to oppose the partition wall  121  in the depthwise direction  53  within the valve chamber  32  (see  FIGS. 6 to 8 ). The first opening  83  is open on this end face  78 , as shown in  FIG. 10 . On the end face  78 , the first opening  83  is positioned offset from a center of the end face  78  (axis of the valve main body  75 ) but away from a periphery (outermost ends) of the end face  78  with respect to the widthwise direction  51 . 
     The second opening  84  is formed on a side surface  79  of the valve main body  75 , the side surface  79  facing the peripheral wall  119  defining the valve chamber  32 . 
     More specifically, the first opening  83  is positioned on the end face  78  at a side opposite to the second opening  84  with respect to a center of the end face  78 . In other words, the first opening  83  and the second opening  84  are positioned opposite to each other with respect to a center of the valve main body  75  (the axis of the valve main body  75 ) in the widthwise direction  51 . In the height direction  52 , the first opening  83  is positioned at the same height as the center of the end face  78  (the center of the valve main body  75 ). This means that the first opening  83  is positioned at the same height as the communication hole  44  in the height direction  52  when the valve  48  is disposed within the valve chamber  32 . The first opening  83  has a diameter smaller than a diameter of the communication hole  44 . 
     The air passage  77  extends from the first opening  83  in the depthwise direction  53  and then bends in a direction perpendicular to the depthwise direction  53  (i.e., in the widthwise direction  51 ) to reach the second opening  84  (refer to  FIGS. 7 and 8 ). 
     Specifically, the air passage  77  is configured of a first passage  68  and a second passage  69 . As shown in  FIGS. 7 and 9 , the first passage  68  is a portion extending in the depthwise direction  53  from the first opening  83 , and the second passage  69  is a portion extending from a front end of the first passage  68  and bending in the widthwise direction  51  to be connected to the second opening  84 . That is, the air passage  77  is a passage connecting the end face  78  and the side surface  79  within the valve main body  75  to establish fluid communication between the first opening  83  and the second opening  84 . 
     The second passage  69  has a cross-sectional area S2 larger than a cross-sectional area S1 of the first passage  68  (S1&lt;S2), as shown in  FIGS. 7 and 8 . Here, the cross-sectional area S2 is defined on a plane perpendicular to the widthwise direction  51 , and has a generally rectangular shape in conformance with the outline of the second opening  84  (see  FIG. 9 ). On the other hand, the cross-sectional area S1 is defined on a plane perpendicular to the depthwise direction  53  and has a generally circular shape in conformance with the outline of the first opening  83  (see  FIG. 10 ). Put another way, the cross-sectional area S2 of the second passage  69  has a larger area than the cross-sectional area S1 of the first passage  68  with respect to a direction perpendicular to the direction of air flow that will be established upon insertion of the ink cartridge  30  into the cartridge accommodating section  110 . 
     The valve main body  75  has one end on which the pair of engaging claws  74  is formed, the one end being opposite to the end face  78  in the depthwise direction  53 . The engaging claws  74  are hook-like shaped and spaced apart from each other in the height direction  52 . More specifically, each engaging claws  74  extends outward (upward or downward in the height direction  52 ) from the one end of the valve main body  75  and then bends toward the end face  78  with a distance kept from an outer surface of the valve main body  75 . Each engaging claw  74  has a distal end portion extending away from the outer surface of the valve main body  75  to form a hook-like shape. The engaging claws  74  (precisely, distal end portions thereof) are respectively configured to be engaged with the engaging claws  126  formed at the open end of the valve chamber  32  when the valve  48  is inserted into the valve chamber  32 . Due to the engagement between the engaging claws  74  and the engaging claws  126 , the valve  48  is prevented from coming out of the valve chamber  32 . 
     The engaging claws  74  define a curved surface  73  therebetween in the height direction  52 , as shown in  FIGS. 6 and 9 . The curved surface  73  has a concaved shape in a side view, being recessed toward the end face  78 . The curved surface  73  defines a center that is most recessed toward the end face  78  (deepest position in the depthwise direction  53 ) and the center is generally coincident with the axis (axial center) of the valve main body  75  and the center of the communication hole  44  formed in the partition wall  121 . The curved surface  73  is configured to receive the release member  130  inserted into the valve chamber  32 . 
     On the end face  78 , an engaging portion  87  is also formed. The engaging portion  87  is provided at a position symmetrical with the first opening  83  with respect to the center of the end face  78 . The engaging portion  87  has a hook-like shape, protruding radially outward. The engaging portion  87  functions to achieve engagement between the end face  78  and the sealing member  76 . 
     The sealing member  76  is provided to cover the end face  78  of the valve main body  75 . The sealing member  76  is made of an elastically deformable material, such as rubber and elastomer. The sealing member  76  has a cap-like shape for hermetically sealing the end face  78 . 
     The sealing member  76  includes a circular-shaped cap portion  65 , a protruding portion  92 , and a flange portion  93 . 
     The cap portion  65  has a cap-like shape, and is formed with through-holes  66  and  67 . The through-holes  66  and  67  are both positioned offset from a diametrical center of the cap portion  65  toward a periphery thereof, but away from the periphery (outermost ends) of the cap portion  65  in the widthwise direction  51 . The through-hole  66  receives the engaging portion  87  therein such that the engaging portion  87  penetrates and engages the through-hole  66 . The sealing member  76  is thus assembled to the end face  78  of the valve main body  75  such that the sealing member  76  is in close contact with the end face  78  in an air-tight manner. The through-hole  67  is positioned to correspond to the first opening  83  of the valve main body  75 . The through-hole  67  has a diameter smaller than the diameter of the communication hole  44 . 
     With this structure, the air passage  77  is permitted to communicate with the valve chamber  32  (or a portion of the valve chamber  32  facing the partition wall  121 ; or first chamber as described below) through the through-hole  67  even when the end face  78  of the valve main body  75  is covered (sealed) with the sealing member  76 . 
     The protruding portion  92  protrudes in a direction away from the end face  78  from the cap portion  65  at a position generally center thereof. The protruding portion  92  has a dome-like shape, defining a hollow space therein. That is, a space is provided between the valve main body  75  and the protruding portion  92 . Therefore, the protruding portion  92  can elastically deform inward to allow a volume of the hollow space to shrink so that the protruding portion  92  can be in close contact with the inner peripheral wall  129  defining the communication hole  44 , thereby realizing sealing of the communication hole  44 . 
     The flange portion  93  is formed to protrude radially outward from an entire circumferential portion of the cap portion  65 . The flange portion  93  has a ring-like shape (O-shape) in a plan view, and functions as an O-ring. The flange portion  93  is configured to be in close contact with and in sliding contact with the peripheral wall  119  of the valve chamber  32  to partition the valve chamber  32  into two chambers: a first chamber in communication with the through-hole  67  as well as with the ink chamber  36  via the communication hole  44 ; and a second chamber in communication with the second opening  84  as well as with the labyrinth path  124  via the through-hole  122 . 
     The second opening  84  formed on the side surface  79  of the valve main body  75  is covered with a semipermeable membrane  94 , as shown in  FIGS. 7 and 8 . The semipermeable membrane  94  is made of a porous membrane having minute holes and is configured to allow passage of air but restrict passage of liquid (i.e., ink in the present embodiment). For example, the semipermeable membrane  94  may be made of a fluorine resin, such as polytetrafluoroethylene, polychlorotrifluoroethylene, tetrafluoroethylene-hexafluoropropylen copolymer, tetrafluoroethylene-perfluoroalkylvinylether copolymer, and tetrafluoroethylene-ethylene copolymer. In  FIGS. 9 and 10 , the semipermeable membrane  94  is omitted. 
     With this structure, since the second opening  84  of the air passage  77  is closed by the semipermeable membrane  94  that permits air flow but restricts passage of ink, ink is prevented from flowing into the labyrinth path  124  that is positioned downstream of the semipermeable membrane  94  (closer to the air communication port  125  than the semipermeable membrane  94  to the air communication port  125 ) in the air flow path of the ink cartridge  30 . 
     The valve main body  75  is further formed with a groove  98  between the second opening  84  and the engaging claws  74 , as shown in  FIGS. 9 and 10 . The groove  98  extends along a periphery (circumference) of the valve main body  75  to fittingly receive the O-ring  99  (the O-ring  99  is omitted in  FIGS. 9 and 10 ). As shown in  FIGS. 7 and 8 , the O-ring  99  is configured to be in sliding contact with and in close contact with the peripheral wall  119  of the valve chamber  32  to realize air-tight sealing of the valve chamber  32 . Due to this gastight sealing of the valve chamber  32  by the O-ring  99 , evaporation of moisture from ink can be prevented in the air flow path of the ink cartridge  30 . Moreover, due to the provision of the O-ring  99 , the labyrinth path  124  is communicable with atmosphere only through the air communication port  125  in the air flow path. The intricate construction of the labyrinth path  124  by itself also serves to suppress ink from getting dried by communication with ambient air through the air communication port  125 . 
     As described above, the first chamber defined by the partition wall  121  and the flange portion  93  is in fluid communication with the ink chamber  36  via the communication hole  44 . The second chamber defined by the flange portion  93  and the O-ring  99  is in communication with the first chamber through the through-hole  67 , the first opening  83 , the air passage  77  and the second opening  84 . When the communication hole  44  is opened, ink may possibly flow from the ink chamber  36  into the first chamber and then into the air passage  77  via the through-hole  67  and the first opening  83 . However, since the second opening  84  is covered with the semipermeable membrane  94 , ink entering into the air passage  77  is prevented from flowing out therefrom, i.e., the semipermeable membrane  94  prevents ink flow from the first chamber to the second chamber. In other words, the flange portion  93  of the sealing member  76  functions to achieve liquid-tight sealing between the first chamber and the second chamber within the valve chamber  32  in conjunction with the semipermeable membrane  94 . Put another way, the first chamber of the valve chamber  32  also functions as an ink buffer chamber in the present embodiment. 
     As shown in  FIGS. 5 and 6 , in a state where the valve  48  has been inserted in the valve chamber  32 , the coil spring  49  is disposed between a peripheral portion of the inner frame  35  defining the open end of the valve chamber  32  and the engaging claws  74 . The valve  48  is thus normally biased in a direction away from the partition wall  121  (leftward in  FIGS. 5 and 6 , or frontward) by the biasing force of the coil spring  49 , as shown in  FIG. 8 . This position of the valve  48  shown in  FIG. 8  is the second position. 
     Specifically, in the second position, while the valve  48  receives the biasing force from the coil spring  49 , the engaging claws  74  of the valve main body  75  are engaged with the engaging claws  126  of the inner frame  35  to prevent the valve  48  from coming out of the valve chamber  32 . The valve  48  is thus retained in the second position, as shown in  FIG. 8 . At this time, the protruding portion  92  of the sealing member  76  is separated from the communication hole  44  and the communication hole  44  is opened. 
     In contrast, in the first position as shown in  FIGS. 6 and 7 , the valve  48  is pressed rearward (rightward in  FIGS. 5 to 7 ) by the release member  130  inserted in the valve chamber  32  against the biasing force of the coil spring  49 . The protruding portion  92  of the sealing member  76  is thus tightly fitted with the inner peripheral wall  129  to close the communication hole  44 . At this time, the engaging claws  126  and the engaging claws  74  are separated from each other in the depthwise direction  53  by a prescribed distance, as shown in  FIG. 6 . In other words, this distance by which the engaging claws  74  in the first position are separated from the engaging claws  126  is equivalent to a distance by which the valve  48  is movable in the depthwise direction  53 . 
     When the valve  48  is retained at the second position, the ink chamber  36  is in communication with ambient air (outside of the ink cartridge  30 ) through the communication hole  44 , the valve chamber  32  (the first chamber defined between the partition wall  121  and the flange portion  93 ; the air passage  77  connecting between the first opening  83  and the second opening  84 ; and the second chamber defined between the flange portion  93  and the O-ring  99 ), the through-hole  122 , the labyrinth path  124 , the air path  128 , and the air communication port  125 . All of these elements serving to permit air flow between the ink chamber  36  and atmosphere constitute the air flow path of the air communication portion  120  in the ink cartridge  30 . 
     (3-4) Release Member 
     The release member  130  is assembled to the hole  96  of the bracket  90 , as shown in  FIGS. 2 and 5  to  7 . As described above, when assembled to the bracket  90 , the release member  130  pushes the valve  48  rearward to maintain the valve  48  at the first position against the biasing force of the coil spring  49 . 
     The release member  130  includes a base  131 , a handling rib  132  and a rod  133 . The base  131  has a flat plate-like shape. The base  131  has a front surface from which the handling rib  132  protrudes frontward, and a rear surface from which the rod  133  protrudes rearward. The rear surface of the base  131  can abut on the protruding end of the first protrusion  85  of the bracket  90 . 
     The handling rib  132  is thin plate-like shaped and has a size that permits a user to hold the handling rib  132  with his fingers (see  FIG. 2 ). 
     The rod  133  is a cross-shaped rib extending in the depthwise direction  53 . The rod  133  is sized to be insertable into the hole  96  of the bracket  90 . The rod  133  is formed in a front-rear length suitable for pressing the valve  48  into the first position. More specifically, the rod  133  has a tip end portion (more specifically, a leading surface  134 ) that is configured to abut on the curved surface  73  of the valve  48  while the release member  130  is being inserted into the hole  96  for assembly to the bracket  90 . In a state where the release member  130  has been assembled to the bracket  90  and the rear surface of the base  131  is in abutment with the protruding end of the first protrusion  85  of the bracket  90 , the valve  48  has been pushed rearward into the valve chamber  32  to be maintained at the first position against the biasing force of the coil spring  49 , while the leading surface  134  is in abutment with the curved surface  73 . At this time, since the center of the curved surface  73  is generally coincident with the axial center of the valve main body  75 , the release member  130  applies load to the valve main body  75  against the biasing force of the coil spring  49  in a direction coincident with the axial center of the valve main body  75 . 
     The rod  133  includes a pair of engaging protrusions  135  protruding radially outward (see  FIG. 4  in which only one of the engaging protrusions  135  is shown). The engaging protrusions  135  are positioned to be spaced away from the base  131  (rear surface of the base  131 ) by a distance corresponding to a thickness of a wall constituting the protruding end of the first protrusion  85  of the bracket  90 . The engaging protrusions  135  are formed to diametrically oppose each other with respect to an axis of the rod  133  in correspondence with the cutouts  136  formed on a peripheral portion of the hole  96  (see  FIG. 3 ). When the release member  130  is inserted into the hole  96 , the engaging protrusions  135  are positionally aligned with the cutouts  136  to pass therethrough in the depthwise direction  53 . 
     Once inserted into the hole  96 , the release member  130  is moved either counterclockwise or clockwise about the axis of the rod  133 . The engaging protrusions  135  of the rod  133  are thus displaced such that the engaging protrusions  135  are no longer positionally coincident with the cutouts  136 . As a result, the engaging protrusions  135  abut against the peripheral portion of the hole  96 , thereby maintaining the release member  130  inserted in the hole  96  against a reaction force from the valve  48 , i.e., the biasing force of the coil spring  49 . The release member  130  has been assembled to the bracket  90  in this way, as shown  FIG. 2 . At this time, the handling rib  132  protrudes from the front wall  140  of the bracket  90  outward (frontward), i.e., in a direction the same as that in which the ink supply portion  34  protrudes. 
     4. How to Realize Air Communication in the Ink Cartridge 
     In an unused state of the ink cartridge  30 , the ink chamber  36  is maintained at a negative pressure. The release member  130  assembled to the bracket  90  (see  FIG. 2 ) pushes the valve  48  to be maintained at its first position against the biasing force of the coil spring  49 , thereby causing the protruding portion  92  of the sealing member  76  to be in intimate contact with the inner peripheral wall  129  defining the communication hole  44  in the partition wall  121  to close the communication hole  44 , as shown in  FIG. 7 . The ink chamber  36  is isolated from outside and ink leakage from the ink chamber  36  is prevented. Hence, ink is prevented from reaching (and thus adhering to) the semipermeable membrane  94  that is positioned closer to outside than the communication hole  44  in the air flow path defined in the air communication portion  120 . 
     Upon use of the ink cartridge  30 , a user removes the release member  130  from the bracket  90 . More specifically, the user rotates the release member  130  with holding the handling rib  132  such that the engaging protrusions  135  are aligned with the cutouts  136  in the depthwise direction  53 . Upon alignment of the engaging protrusions  135  with the cutouts  136  in the depthwise direction  53 , since the rod  133  of the release member  130  is applied with the biasing force of the coil spring  49 , the rod  133  is pushed outward (frontward) due to the biasing force of the coil spring  49 . 
     As shown in  FIG. 8 , as the rod  133  is coming out of the hole  96 , the valve  48  moves from the first position to the second position. When the valve  48  has moved from the first position to the second position, the protruding portion  92  of the sealing member  76  is separated from the inner peripheral wall  129  to open the communication hole  44 . As a result, the ink chamber  36  is brought into communication with atmosphere through the communication hole  44 , the valve chamber  32  (first chamber), the air passage  77 , the valve chamber  32  (second chamber), the through-hole  122 , the labyrinth path  124 , and the air communication port  125 . The ink chamber  36  is thus brought into atmospheric pressure. 
     5. How Ink Flows if the Ink Cartridge is Placed in a Posture Other than its Upstanding Posture 
     Since the ink cartridge  30  has the width smaller than its height and depth, a user is likely to hold the ink cartridge  30  with its side surfaces being nipped with his fingers. However, while holding the ink cartridge  30  in this way, the user may turn the ink cartridge  30  into a posture other than the upstanding posture shown in  FIG. 2 . Further, since the side surfaces have the largest area among the surfaces constituting the outer contour of the ink cartridge  30 , possibly, the ink cartridge  30  may be placed on a plane with one of its side surfaces facing downward. 
     Hereinafter, how ink flows based on postures of the ink cartridge  30  will be explained. Also hereinafter, it is assumed that the user holds the ink cartridge  30  just prior to use, and therefore the valve  48  is in the second position and the communication hole  44  is opened. 
       FIG. 11  illustrates a state of the air communication portion  120  (within the valve chamber  32 ), assuming that the ink cartridge  30  is placed on a plane with the side wall  37  of the cartridge body  31  and the side wall  143  of the bracket  90  facing downward. In  FIG. 11 , a surface of the ink flowing out of the ink chamber  36  is labeled as an ink surface  115 . 
     The ink in the ink chamber  36  may flow into the valve chamber  32  (first chamber) via the communication hole  44 , when the ink surface  115  reaches the communication hole  44  or higher. Since the valve  48  is at the second position, the cap portion  65  of the sealing member  76  is separated from the partition wall  121  in the depthwise direction  53 . The ink flowing through the communication hole  44  accumulates in the first chamber of the valve chamber  32 . The through-hole  67  of the sealing member  76  and the first opening  83  of the valve main body  75  are positioned lower than the communication hole  44  in the widthwise direction  51 , but are positioned higher than (away from) a bottom surface of the valve chamber  32  in the widthwise direction  51  (which now corresponds to the vertical direction), as shown in  FIG. 11 . Note that the through-hole  67  and the first opening  83  are respectively not positioned on the outermost ends of the cap portion  65  and of the end face  78 . Hence, ink flowing into the first chamber will not immediately reach and flow into the through-hole  67  and the first opening  83 . 
     If the ink continues to flow into the first chamber, the ink surface  115  rises and the ink starts to flow into the air passage  77  through the through-hole  67  and the first opening  83 . The ink flowing into the air passage  77  enters into the first passage  68  and then into the second passage  69  having a cross-sectional area S2 larger than the cross-sectional area S1 of the first passage  68 . Further, the second opening  84  is positioned higher than the through-hole  67  and the first opening  83  in the widthwise direction  51 . The ink surface  115  needs to rise up to the second opening  84  if the ink surface  115  is to reach the semipermeable membrane  94 . Hence, even if ink may enter into the air passage  77 , the ink does not immediately reach the semipermeable membrane  94 . 
     Next, assume that the ink cartridge  30  is placed with the side wall  38  of the cartridge body  31  and the side wall  144  of the bracket  90  facing downward.  FIG. 12  illustrates a state of the air communication portion  120  (within the valve chamber  32 ) at this time. 
     In this state, the through-hole  67  and the first opening  83  are positioned higher than the communication hole  44  and the second opening  84  in the widthwise direction  51  (which now corresponds to the vertical direction). The ink surface  115  may rise as the ink coming from the ink chamber  36  accumulates in the first chamber of the valve chamber  32 . The ink may enter into the air passage  77  when the ink surface  115  reaches the through-hole  67  and the first opening  83 . However, since the through-hole  67  and the first opening  83  are positioned higher than the axial center of the valve chamber  32  in the widthwise direction  51 , the ink flowing into the first chamber does not immediately enter into the air passage  77  through the through-hole  67  and the first opening  83 . The ink is thus hard to reach the semipermeable membrane  94 . 
     Now assume that the ink cartridge  30  is placed with the upper wall  39  of the inner frame  35  and the upper wall  141  of the bracket  90  facing downward (i.e., the ink cartridge  30  is turned upside down). 
     In this state, since the communication hole  44  is positioned at a lower portion of the ink chamber  36  in the height direction  52 , ink flows into the first chamber (valve chamber  32 ) through the communication hole  44 . However, within the valve chamber  32 , the communication hole  44  and the first opening  83  (the through-hole  67 ) are positioned at the same height as each other with respect to the height direction  52 . Therefore, ink accumulated in the first chamber does not enter into the air passage  77  until the ink surface  115  rises up to the height of the through-hole  67  and the first opening  83  in the height direction  52 . Hence, ink may enter into the valve chamber  32  (first chamber) but is prevented from reaching the semipermeable membrane  94  immediately, even when the ink cartridge  30  is flipped upside down. 
     6. Operations and Technical Advantages 
     According to the structure of the present embodiment, the valve  48  is configured to slide within the valve chamber  32  to cause the protruding portion  92  of the sealing member  76  to open and close the communication hole  44 . The flange portion  93  of the sealing member  76  is in intimate and sliding contact with the peripheral wall  119  of the valve chamber  32  to realize liquid-tight sealing between the first chamber (communicating with the first opening  83 ) and the second chamber (communicating with the second opening  84 ). The valve  48  can become simple and compact, while achieving opening and closing of the air flow path in the air communication portion  120 . 
     Also, the protruding portion  92  is elastically deformable to be in close contact with the inner peripheral wall  129  of the communication hole  44 . Hence, contact area between the protruding portion  92  and the inner peripheral wall  129  can be wider than otherwise, thereby realizing reliable sealing of the communication hole  44 . 
     Further, the protruding portion  92  is easy to deform in conformance with an outer shape of the communication hole  44  due to provision of a hollow space inside the protruding portion  92 . 
     Further, the release member  130  is moved to be detached from the bracket  90  when engagement of the release member  130  with the bracket  90  is released. In accordance with the detachment movement of the release member  130 , the valve  48  is moved move from the first position to the second position due to the biasing force of the coil spring  49 . As a result, the ink chamber  36  is permitted to communicate with atmosphere through the communication hole  44  that is opened by the valve  48  moved to the second position. According to this structure of the present embodiment, the movement of the valve  48  attributed to removal of the release member  130  is achieved solely by the biasing force of the coil spring  49 . Since there is no need for the user to resist the biasing force of the coil spring  49 , the user can feel little load for achieving communication of the ink chamber  36  with atmosphere. 
     Significance of the structure of the present embodiment can be demonstrated clearly when compared to a conventional valve structure in which a valve body is biased by a biasing member in a direction to close an air communication port (see Japanese Patent Application Publication No. 2009-96126, for example). In this type of conventional valve structure, in order to open the air communication port, a user is required to apply a force to move the valve body against a biasing force of the biasing member during mounting of the ink cartridge. Hence, conceivably, user&#39;s workload required during mounting of the ink cartridge is not slight. This hold true not only for a conventional valve structure in which a user needs to apply force against the biasing force of the biasing member to the open the air communication port before mounting the ink cartridge, but also for other conventional technique other than valve structure to open the air communication port: for example, a structure in which a user needs to break a seal closing the air communication port. In any of these conventional techniques, user&#39;s workload could be heavy. In contrast, the structure of the present embodiment can reduce such burden for a user to open the communication hole  44  in order to realize communication between the ink chamber  36  and outside of the ink cartridge  30 , since there is no need for a user to apply force against the biasing force of the coil spring  49 . 
     According to another aspect of the ink cartridge  30  according to the depicted embodiment, the semipermeable membrane  94  is attached to the valve main body  75  of the valve  48  to close the air passage  77 , and the labyrinth path  124  is formed in the inner frame  35 . With this structure, even if ink may flow into the valve chamber  32  through the communication hole  44  for some reason, for example, by user&#39;s turning the ink cartridge  30  upside down, the ink is suppressed from flowing out of the inner frame  35 . 
     Further, the semipermeable membrane  94  is attached to the valve main body  75  of the valve  48 , not attached to the peripheral wall  119  of the valve chamber  32 . This means that, the semipermeable membrane  94  can be attached to the valve main body  75  in a state where the valve main body  75  is removed from the valve chamber  32 . Therefore, providing (attaching) the semipermeable membrane  94  in the air flow path formed in the air communication portion  120  is realized with ease and assembly of the ink cartridge  30  can be facilitated, compared to a case in which the semipermeable membrane  94  is attached to somewhere within the valve chamber  32 . 
     Providing a semipermeable membrane in an air flow path is a conventional art used to seal the air flow path formed in the ink cartridge (see Japanese Patent Application Publication Nos. 2010-221477 and 2012-152998, for example). However, the semipermeable membrane cannot ensure its prescribed air communication performance when exposed to ink, since contact with ink could cause ink meniscus to be formed in minute holes of the semipermeable membrane and result in increase in resistance for air to pass the semipermeable membrane. 
     User&#39;s unintended handling of the ink cartridge (for example, a user may temporarily place the ink cartridge in an orientation other than the upstanding posture before mounting the ink cartridge into an accommodating section or when unpacking a new ink cartridge) could cause ink to flow out from the ink chamber into the air flow path, possibly resulting in contact of the ink with the semipermeable membrane. However, according to the depicted structure of the ink cartridge  30  of the present embodiment, even if the ink cartridge  30  is held or placed in an orientation other than the upstanding posture, the ink flowing into the valve chamber  32  from the ink chamber  36  via the communication hole  44  does not reach the semipermeable membrane  94  immediately. 
     Furthermore, the second passage  69  has the larger cross-sectional area S2 than the cross-sectional area S1 of the first passage  68  with respect to the direction perpendicular to the direction of air flow in the air passage  77 . Therefore, this structure makes it harder for the ink entering into the second passage  69  from the first passage  68  to immediately reach the semipermeable membrane  94 . 
     Still further, the communication hole  44  and the first opening  83  are positioned vertically at the same height as each other in the height direction  52 . Hence, although ink may flow into the valve chamber  32  (first chamber) when the ink cartridge  30  is in the upstanding posture or in a state where the ink cartridge  30  is flipped upside down, the ink does not enter into the air passage  77  until the ink surface  115  within the first chamber rises up to the same height as the through-hole  67  and the first opening  83  in the height direction  52 . This construction is effective in suppressing the ink accumulated in the first chamber from reaching the semipermeable membrane  94 . 
     Still further, since the first opening  83  is positioned to be spaced away from the communication hole  44  in the depthwise direction  53  when the valve  48  is at the second position, the space is formed between the flange portion  93  and the partition wall  121  (first chamber). This space (first chamber) can serve as the ink buffer chamber to prevent ink accumulated therein from immediately reaching the semipermeable membrane  94 . 
     Still further, the communication hole  44  is formed in the center of the partition wall  121  in the widthwise direction  51  in the present embodiment. With this structure, ink in the ink chamber  36  is prevented from flowing into the valve chamber  32  through the communication hole  44  even if the ink cartridge  30  is held or placed with one of the side surfaces facing downward, as long as the ink surface within the ink chamber  36  is below the communication hole  44 . 
     Yet further, the first opening  83 , the second opening  84  and the air passage  77  are formed in the valve  48 , and the communication hole  44  is closed by the valve  48  in the first position. With this structure, ink is prevented from entering into the valve chamber  32  as long as the valve  48  is in the first position. 
     According to still another aspect, when the release member  130  is assembled to the bracket  90 , the handling rib  132  of the release member  130  protrudes from the front wall  140  of the bracket  90  in a direction the same as the direction in which the ink supply portion  34  protrudes (in the loading direction  56 ). With this structure, if the user attempts to insert the ink cartridge  30  into the cartridge accommodating section  110  without removing the release member  130  from the bracket  90 , the release member  130  interferes with the cartridge accommodating section  110  and prevents the ink needle  113  from entering into the ink supply portion  34 . That is, the ink cartridge  30  cannot be loaded in the cartridge accommodating section  110  without removing the release member  130  in advance. This configuration can reliably prevent wrong installation of the ink cartridge  30  into the cartridge accommodating section  110 . 
     In the ink cartridge  30  of the present embodiment, the sealing member  76  and a part of the air flow path (air passage  77 , first and second chambers) are provided within the valve chamber  32 . Space within and in the vicinity of the valve chamber  32  is therefore effectively utilized. 
     Although a part of the air flow path (air passage  77 ) is formed in the valve  48  in the depicted embodiment, the air flow path in entirety may be formed in the inner frame  35  if the valve  48  is not employed in the ink cartridge  30 . 
     Specifically, for example, a chamber that constitutes a part of the air flow path is formed in the inner frame  35  and a foam may be disposed within the chamber to absorb ink. In this case, the chamber filled with the foam is in communication with the labyrinth path  124  at a position closer to the ink chamber  36  than the labyrinth path  124  to the ink chamber  36  in the air flow path. Alternatively, a semipermeable membrane for closing the air flow path may be directly attached to the inner frame  35  at a position closer to the ink chamber  36  than the labyrinth path  124  to the ink chamber  36  in the air flow path. With these structures without the valve  48 , communication between the ink chamber  36  and ambient air can be achieved, while ink leakage can be prevented. 
     While the invention has been described in detail with reference to the specific embodiment thereof, it would be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention.