Patent Publication Number: US-11027555-B2

Title: Printing-fluid cartridge including protrusion and interface

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 15/664,048 filed Jul. 31, 2017, which claims priority from Japanese Patent Application No. 2016-255352 filed Dec. 28, 2016. The entire content of the priority applications are incorporated herein by reference. Further, the present application closely relates to co-pending U.S. patent application Ser. Nos. 15/664,348, 15/664,015 and 15/664,089, all filed on Jul. 31, 2017, which are incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a printing-fluid cartridge having a protrusion and an interface. 
     BACKGROUND 
     Conventionally, there have been known inkjet recording apparatuses configured to record images on recording mediums by ejecting ink stored in ink cartridges through nozzles. There is known an inkjet recording apparatus in which a new ink cartridge is mountable every time ink is consumed. In an inkjet recording apparatus capable of performing color printing, a plurality of ink cartridges can be mountable. For example, Japanese Patent Application Publication No. 2015-58545 discloses an ink cartridge that is provided with an IC board. 
     SUMMARY 
     When the ink cartridge falls on the ground or collides with other objects, the ink cartridge easily has an impact on the IC board disposed at the surface of a cartridge body of the ink cartridge. As a result, an electrical interface on the IC board is broken or deformed so that the information stored in the IC board cannot be read out. Further, when the ink cartridge falls on the ground, not only the IC board but also other members can be broken by colliding with the ground. Providing protection walls around the IC board or the other members can be a solution to the problem, but the protection walls around the IC board or the other members can be obstacles when the IC board is being attached to the cartridge body. 
     In view of the foregoing, it is an object of the present disclosure to provide a printing-fluid cartridge where the electrical interface is well protected from being broken and to which the electrical interface can be attached easily. 
     In order to attain the above and other objects, the present disclosure provides a printing fluid cartridge a printing fluid cartridge configured to be inserted into a printing fluid consuming apparatus in an insertion direction crossing a gravitational direction in an attached posture. The printing fluid cartridge including: a storage chamber, a supply portion, a rear surface, an upper surface, an electrical interface, a locking surface, one protrusion, and another protrusion. The storage chamber is configured to store printing fluid. The supply portion is configured to supply the printing fluid from the storage chamber. The supply portion is provided at the front surface. The rear surface is away from the front surface in a rearward direction opposite to the insertion direction. The storage chamber is positioned between the front surface and the rear surface. The upper surface is disposed upward relative to the storage chamber and faces upward opposite to the gravitational direction in the attached posture. The electrical interface is disposed at the upper surface and configured to contact a contact portion disposed in the printing fluid consuming apparatus. The locking surface is disposed upward relative to the storage chamber in the attached posture and is configured to engage with the printing fluid consuming apparatus. The one protrusion is disposed at the upper surface. The one protrusion is disposed frontward relative to the electrical interface in the insertion direction and has one specific portion. The detection surface is disposed upward relative to the storage chamber in the attached posture and configured to receive a detection signal from the printing fluid consuming apparatus. The another protrusion is disposed at the upper surface and disposed rearward relative to the electrical interface. The another protrusion has another specific portion. The one protrusion and the another protrusion define a plurality of imaginary planes each of which passes through the one protrusion and the another protrusion. Each of the plurality of imaginary planes extends in a widthwise direction perpendicular to the gravitational direction and the insertion direction in the attached posture. The plurality of imaginary planes includes a specific imaginary plane defined by the one specific portion and the another specific portion. The specific imaginary plane is positioned higher than any other imaginary plane between the one protrusion and the another protrusion. The electrical interface is positioned downward relative to the specific imaginary plane in the gravitational direction in the attached posture. The detection surface, the electrical interface, and the locking surface are arranged in a recited order above the upper surface in the rearward direction. 
     According to another aspect, the present disclosure also provides a printing fluid cartridge including a storage chamber, a supply portion, a rear surface, an upper surface, a locking surface, one protrusion, and an electrical interface. The storage chamber is configured to store printing fluid. The supply portion includes a supply hole through which the printing fluid is configured to flow out of the storage chamber in a frontward direction crossing a gravitational direction in an upright posture. The supply portion is provided at the front surface. The rear surface is away from the front surface in a rearward direction opposite to the frontward direction in the upright posture. The storage chamber is positioned between the front surface and the rear surface. The upper surface is disposed upward relative to the storage chamber and facing upward opposite to the gravitational direction in the upright posture. The locking surface is disposed at the upper surface and facing rearward. The one protrusion is positioned at the upper surface and has a detection surface extending in the frontward direction. The electrical interface is disposed at the upper surface. The locking surface, the electrical interface, and the one protrusion are arranged in a recited order in the frontward direction in the upright posture. The one protrusion, the electrical interface, and the locking surface are arranged upward in a recited order in the upright posture. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a schematic cross-sectional diagram conceptually showing an internal configuration of a printer including a cartridge-attachment section configured to detachably accommodate ink cartridges according to an embodiment of the present disclosure; 
         FIG. 2  is a perspective view showing an external appearance of the cartridge-attachment section and an opening of the cartridge-attachment section; 
         FIG. 3  is a cross-sectional view of the cartridge-attachment section taken along a plane in  FIG. 4 , the cartridge-attachment section including gates formed with slits, wherein two of the ink cartridges according to the embodiment are inserted into corresponding insertion spaces; 
         FIG. 4  is a vertical cross-sectional diagram illustrating a state where the ink cartridge (of magenta color) according to the embodiment is attached to the cartridge-attachment section in a first posture; 
         FIG. 5A  is an enlarged cross-sectional view of an enclosed region VB illustrated in  FIG. 4 ; 
         FIG. 5B  is an enlarged cross-sectional view of an enclosed region VA illustrated in  FIG. 4 ; 
         FIG. 6  is a perspective view of the ink cartridge (of magenta color) according to the embodiment when viewed from a perspective frontward and upward thereof; 
         FIG. 7  is a perspective view of the ink cartridge (of magenta color) according to the embodiment when viewed from a perspective rearward and upward thereof; 
         FIG. 8  is a cross-sectional view of the ink cartridge (of magenta color) according to the embodiment taken along an imaginary plane X 2  illustrated in  FIG. 9B  and showing an internal configuration of the ink cartridge according to the embodiment; 
         FIG. 9A  is a left side view of the ink cartridge (of magenta color) according to the embodiment and illustrating arrangement of parts disposed at an upper surface of the ink cartridge according to the embodiment; 
         FIG. 9B  is a rear side view of the ink cartridge (of magenta color) according to the embodiment; 
         FIG. 10  is a left side view of the ink cartridge (of magenta color) according to the embodiment and illustrating positional relationship among various parts of the ink cartridge in the front-rear direction and up-down direction; 
         FIG. 11A  is a perspective view of the ink cartridge of black color according to the embodiment when viewed from a perspective rearward and upward thereof; 
         FIG. 11B  is a rear side view of the ink cartridge of black color according to the embodiment; 
         FIG. 12  is a perspective view of the ink cartridge of black color according to the embodiment when viewed from a perspective frontward and upward thereof; 
         FIGS. 13A through 13D  are top views of the ink cartridges of colors of black, magenta, cyan and yellow, respectively, according to the embodiment; 
         FIG. 14  is a top view of the ink cartridge of black color according to the embodiment; 
         FIG. 15  is a top view of the ink cartridge of magenta color according to the embodiment; 
         FIG. 16  is a vertical cross-sectional diagram illustrating a state where the ink cartridge (of magenta color) according to the embodiment is inserted in the corresponding insertion space of the cartridge-attachment section; 
         FIG. 17  is a vertical cross-sectional diagram illustrating a state where the ink cartridge (of magenta color) according to the embodiment is inserted further frontward in the corresponding insertion space of the cartridge-attachment section after the state illustrated in  FIG. 16  and is in a second posture in the corresponding insertion space; 
         FIG. 18  is a vertical cross-sectional diagram illustrating a state where the ink cartridge (of cyan color) is inserted in the insertion space for the ink cartridge of magenta color and a light-blocking plate (interfering surface) of the ink cartridge (of cyan color) is in abutment with the gate for the ink cartridge of magenta color; 
         FIG. 19  is a flow chart illustrating steps of a process to determine types of the ink cartridges according to the embodiment attached to the cartridge-attachment section performed by a controller of the printer; 
         FIG. 20  is a left side view of an ink cartridge according to a first modification to the embodiment; 
         FIG. 21  is a left side view of an ink cartridge according to a second modification to the embodiment; 
         FIG. 22  is a vertical cross-sectional view of the ink cartridge according to the second modification to the embodiment; 
         FIG. 23A  is a perspective view of an ink cartridge according to a third modification to the embodiment; 
         FIG. 23B  is a vertical cross-sectional view of the ink cartridge according to the third modification to the embodiment taken along a plane XXIIB-XXIIB shown in  FIG. 23A ; 
         FIG. 24  is a left side view of an ink cartridge according to a fourth modification to the embodiment; 
         FIG. 25  is a left side view of an ink cartridge according to a fifth modification to the embodiment; and 
         FIG. 26  is a left side view of an ink cartridge according to a sixth modification to the embodiment; 
         FIG. 27  is a left side view of an ink cartridge according to a seventh modification to the embodiment; 
         FIG. 28  is a vertical cross-sectional view of an ink cartridge according to an eighth modification to the embodiment; and 
         FIG. 29  is a flow chart illustrating steps of a process according to a variation of the embodiment performed by the controller of the printer to determine whether the ink cartridge according to the embodiment is attached to the cartridge-attachment section. 
         FIG. 30  is a flow chart illustrating steps of a process according to another variation of the embodiment performed by the controller of the printer to determine whether the ink cartridge according to the embodiment is attached to the cartridge-attachment section. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, an embodiment of the disclosure is described in detail while referring to accompanying drawings. It would be apparent to those skilled in the art that the embodiment described below is merely an example of the present disclosure and modifications and variations may be made therein without departing from the scope of the disclosure. 
     In the following description, a frontward direction  51  is defined as a direction in which an ink cartridge  30  according to the embodiment is inserted into a cartridge-attachment section  110 , while a rearward direction  52  is defined as a direction opposite the frontward direction  51 , that is, a direction in which the ink cartridge  30  is extracted from the cartridge-attachment section  110 . The frontward direction  51  and rearward direction  52  are horizontal in the present embodiment. 
     Further, a downward direction  53  is defined as a direction perpendicular to the frontward direction  51  or the rearward direction  52 , while an upward direction  54  is defined as a direction opposite the downward direction  53 . Further, a rightward direction  55  and a leftward direction  56  are defined as directions perpendicular to the frontward direction  51  and the downward direction  53 . The rightward direction  55  and the leftward direction  56  are also parallel to the horizontal direction. The rightward direction  55  and the leftward direction  56  are also parallel to a horizontal plane in the present embodiment. 
     In a state where the ink cartridge  30  is attached to the cartridge-attachment section  110  (in an attached state) and the ink cartridge  30  is capable of being used or operated by the printer  10 , the downward direction  53  is coincident with a direction of a gravitational force acting on the ink cartridge  30  (i.e. gravitational direction), and the upward direction  54  is coincident with a direction opposite to the gravitational direction. Further, the rightward direction  55  and the leftward direction  56  are defined as directions perpendicular to the frontward direction  51  and the downward direction  53 . More specifically, in a state where the ink cartridge  30  is attached to the cartridge attachment section  110  and is capable of being used by the printer  10 , the rightward direction  55  is a direction toward the right and the leftward direction  56  is a direction toward the left when the ink cartridge  30  is viewed from a rear side thereof. 
     Note that a state where the ink cartridge  30  is attached to the cartridge attachment section  110  or a state where the ink cartridge  30  is capable of being operated by the printer  10  implies a state of the ink cartridge  30  when the ink cartridge  30  has been completely inserted into an attachment position in the cartridge attachment section  110 . Hereinafter, a posture of the ink cartridge  30  in a state where the ink cartridge  30  is attached to the cartridge attachment section  110  or a state where the ink cartridge  30  is capable of being operated by the printer  10  will be referred to as an “attached posture.” 
     In other words, in the attached posture, the ink cartridge  30  has a height in the gravitational direction; a depth in the frontward direction  51  or in the rearward direction  52  (i.e., insertion direction) which is orthogonal to the gravitational direction; and a width in the rightward direction  55  or in the leftward direction  56  (i.e., widthwise direction) which is orthogonal to the gravitational direction (height) and the insertion direction (depth). 
     Further, in the following description, the frontward direction  51  and the rearward direction  52  may be collectively referred to as a front-rear direction. The upward direction  54  and the downward direction  53  may be collectively referred to as an up-down direction. The rightward direction  55  and the leftward direction  56  may be collectively referred to as a left-right direction. 
     In this specification, “facing frontward” includes facing in a direction including a frontward component, “facing rearward” includes facing in a direction including a rearward component, “facing downward” includes facing in a direction including a downward component, and “facing upward” includes facing in a direction including an upward component. For example, “a front surface faces frontward” denotes that the front surface may face in a frontward direction, or the front surface may face in a direction inclined relative to the frontward direction. 
     &lt;Overview of the Printer  10 &gt; 
       FIG. 1  shows a system  1  configured of a printer  10  and the ink cartridge  30  according to the embodiment. First, a detailed structure of the printer  10  according to the embodiment will be described with reference to  FIG. 1 . 
     The printer  10  is configured to form an image by selectively ejecting ink droplets onto a sheet based on an inkjet recording system. As illustrated in  FIG. 1 , the printer  10  includes a recording head  21 , an ink-supplying device  100 , and ink tubes  20  connecting the recording head  21  to the ink-supplying device  100 . The ink-supplying device  100  includes the cartridge-attachment section  110 . The cartridge-attachment section  110  can detachably accommodate a plurality of ink cartridges  30  therein. 
     Specifically, in the present embodiment, four ink cartridges  30 C,  30 M,  30 Y and  30 K each storing ink of one of four colors of cyan, magenta, yellow, and black can be mounted in corresponding insertion spaces  111 C,  111 M,  111 Y and  111 K of the cartridge-attachment section  110 . Hereinafter, whenever necessary, the ink cartridges  30 C,  30 M,  30 Y and  30 K may be referred to as “ink cartridge  30 ” or “ink cartridges  30 ” when no color distinction is necessary. Likewise, the insertion spaces  111 C,  111 M,  111 Y and  111 K of the cartridge-attachment section  110  may be referred to as “insertion space  111 ” or “insertion spaces  111 ” when no color distinction is necessary. 
     The cartridge-attachment section  110  has a wall formed with an opening  112 . The ink cartridges  30  can be inserted into the cartridge-attachment section  110  in the frontward direction  51  (i.e., insertion direction orthogonal to the gravitational direction) through the opening  112 , and extracted from the cartridge-attachment section  110  in the rearward direction  52  (i.e., removal direction orthogonal to the gravitational direction) through the opening  112 . 
     Each ink cartridge  30  stores ink therein that the printer  10  can use for printing. The ink cartridges  30  are connected to the recording head  21  through the corresponding ink tubes  20  when the ink cartridges  30  are completely mounted in the cartridge-attachment section  110 . 
     The recording head  21  includes sub tanks  28  each serving to temporarily store ink supplied from the corresponding ink cartridge  30  through the corresponding ink tube  20 . The recording head  21  also includes a plurality of nozzles  29  through which the ink supplied from the sub tanks  28  is selectively ejected in accordance with the inkjet recording system. More specifically, the recording head  21  includes a head control board (not shown), and piezoelectric elements  29 A each corresponding to one of the nozzles  29 . The head control board is configured to selectively apply drive voltages to the piezoelectric elements  29 A to eject ink of each color selectively from the nozzles  29 . In this way, the recording head  21  is configured to consume the ink stored in the respective ink cartridges  30  mounted in the cartridge-attachment section  110 . 
     The printer  10  also includes a sheet tray  15 , a sheet feeding roller  23 , a conveying path  24 , a pair of conveying rollers  25 , a platen  26 , a pair of discharge rollers  27 , and a sheet discharge tray  16 . The sheets from the sheet tray  15  are fed by the sheet feeding roller  23  onto the conveying path  24 , and then conveyed by the conveying rollers  25  onto the platen  26 . The recording head  21  is configured to selectively eject ink onto the sheets as the sheets move over the platen  26 , thereby recording images on the sheets. The sheets that have passed the platen  26  are then discharged by the discharge rollers  27  onto the sheet discharge tray  16  disposed at a downstream end of the conveying path  24 . 
     &lt;Ink-Supplying Device  100 &gt; 
     The ink-supplying device  100  is provided in the printer  10 , as illustrated in  FIG. 1 . The ink-supplying device  100  functions to supply ink to the recording head  21 . As described above, the ink-supplying device  100  includes the cartridge-attachment section  110  for detachably receive the ink cartridges  30  therein.  FIG. 1  depicts a state where one of the ink cartridges  30  has been completely received in the cartridge-attachment section  110 . In other words, the ink cartridge  30  depicted in  FIG. 1  is in the attached posture in which the ink cartridge  30  is used by the printer  10 . 
     &lt;Cartridge-Attachment Section  110 &gt; 
     In the ink-supplying device  100 , the ink cartridges  30 C,  30 M,  30 Y and  30 K (the four kinds of ink cartridges  30  corresponding to the colors of cyan, magenta, yellow and black) are detachably mountable. Specifically, as illustrated in  FIGS. 1 through 3 , the cartridge-attachment section  110  includes a case  101 , and four sets of an ink needle  102 , a tank  103 , an optical sensor  113 , four contacts  106 , a rod  125 , a positioning portion  107  and a gate  108 , each set for each of the four ink cartridges  30 C,  30 M,  30 Y and  30 K. 
     &lt;Case  101 &gt; 
     The case  101  constitutes a housing of the cartridge-attachment section  110 . As depicted in  FIG. 2 , the case  101  has a box-like shape defining an internal space therein. Specifically, the case  101  includes a top wall defining a ceiling of the internal space, a bottom wall defining a bottom of the internal space, an end wall connecting the top wall and the bottom wall, and the opening  112  positioned opposite the end wall in the front-rear direction. The opening  112  can be exposed to a surface (user-interface surface) that a user can face when using the printer  10 . 
     The four kinds of ink cartridges  30  can be inserted into and removed from the case  101  through the opening  112 . In the case  101 , the bottom wall is formed with four guide grooves  109  for guiding insertion/removal of the corresponding ink cartridges  30 . Specifically, when the ink cartridges  30  are inserted into and removed from the case  101  through the opening  112 , lower ends of the respective ink cartridges  30  are received in the corresponding guide grooves  109  and guided thereby in the front-rear direction in  FIG. 2 . Further, the case  101  includes three plates  104  that partition the internal space into the four insertion spaces  111 C,  111 M,  111 Y and  111 K. The respective insertion spaces  111 C,  111 M,  111 Y and  111 K are elongated in the up-down direction  53  and  54 . The four kinds of ink cartridges  30 C,  30 M,  30 Y and  30 K can be mounted in the four insertion spaces  111 C,  111 M,  111 Y and  111 K, respectively. 
     As illustrated in  FIG. 2 , when the case  101  is viewed from rearward thereof in the forward direction  51 , the four insertion spaces  111 C,  111 M,  111 Y and  111 K of the case  101  are arranged in this order from the left end to the right. Specifically, the ink cartridge  30 C is adapted to be inserted into the insertion space  111 C. The ink cartridge  30 M is adapted to be inserted into the insertion space  111 M. The ink cartridge  30 Y is adapted to be inserted into the insertion space  111 Y. The ink cartridge  30 K is adapted to be inserted into the insertion space  111 K. That is, when the ink cartridges  30  are accommodated in the case  101 , the ink cartridge  30 M is interposed between the ink cartridges  30 C and  30 Y in the left-right direction. The ink cartridge  30 K has a left-right dimension larger than a left-right dimension of each of the ink cartridges  30 C,  30 M, and  30 Y, as will be described later. Thus, the insertion space  111 K has a left-right dimension that is larger than a left-right dimension of each of the insertion spaces  111 C,  111 M and  111 Y. 
     &lt;Ink Needle  102 &gt; 
     Each ink needle  102  is formed of a resin and has a generally hollow tubular shape. As illustrated in  FIG. 2 , the ink needles  102  are disposed at a lower end portion of the end wall constituting the case  101 . Specifically, each ink needle  102  is disposed at a position corresponding to an ink supply potion  34  (described later) of the corresponding ink cartridge  30  mounted in the cartridge-attachment section  110 . The respective ink needles  102  protrude rearward from the end wall of the case  101 . The ink needle  102  has a distal end  102 E facing rearward. 
     A cylindrical-shaped guide portion  105  is provided at the end wall to surround each of the ink needles  102 . Each guide portion  105  protrudes rearward from the end wall. Each guide portion  105  has a protruding end that is open rearward. Specifically, each ink needle  102  is positioned at a diametrical center of the corresponding guide portion  105 . Each guide portion  105  is shaped to allow the ink supply potion  34  of the corresponding ink cartridge  30  to be received in the corresponding guide portion  105 . 
     During insertion of the ink cartridge  30  into the cartridge-attachment section  110  in the frontward direction  51 , i.e., in a process for moving the ink cartridge  30  to the attached posture, the ink supply potion  34  of the ink cartridge  30  enters into the corresponding guide portion  105  (refer to  FIG. 4 ). As the ink cartridge  30  is inserted further forward in the frontward direction  51 , the ink needle  102  enters into an ink supply port  71  of the corresponding ink supply potion  34 . The ink needle  102  is thus connected to the corresponding ink supply potion  34  to allow communication with each other. Hence, the ink stored in a second ink chamber  33  formed inside the ink cartridge  30  is allowed to flow into the corresponding tank  103  through an ink valve chamber  35  defined in the ink supply potion  34  and an inner space defined in the corresponding ink needle  102 . 
     Incidentally, the distal end  102 E of each ink needle  102  may have a flat shape or a pointed shape. The guide portions  105  may be formed into any shape, provided that the guide portions  105  can allow attachment of the ink cartridges  30  to the cartridge-attachment section  110 . The guide portions  105  need not necessarily be provided in the cartridge-attachment section  110 . 
     &lt;Contacts  106 &gt; 
     A set of the four contacts  106  is provided for each of the four insertion spaces  111  of the case  101 . Precisely, the contacts  106  are provided in a holder (not shown) that is supported by the cartridge-attachment section  110 . As illustrated in  FIG. 4 , each of the four sets of the contacts  106  is disposed at the top wall of the case  101 , for each insertion space  111 , at a position near the end wall of the case  101 . Each set of the four contacts  106  is disposed rearward relative to the corresponding ink needle  102 . Each of the four contacts  106  protrude from a lower surface of the top wall downward toward the corresponding insertion space  111  of the case  101 . Although not illustrated in detail in the drawings, the four contacts  106  in each set are arranged to be spaced apart from one another in the left-right direction. The four contacts  106  in each set are arranged at positions respectively corresponding to four electrodes  65  provided at each of the ink cartridges  30 , as will be described later. Each contact  106  is formed of a material having electrical conductivity and resiliency. The contacts  106  are therefore upwardly resiliently deformable. 
     In the present embodiment, the four sets of the four contacts  106  are disposed each set for each of the four ink cartridges  30 C,  30 M,  30 Y and  30 K in the present embodiment. That is, a total of sixteen contacts  106  are provided at the case  101 . However, the number of contacts  106  and the number of electrodes  65  may be arbitrary. 
     Each contact  106  is electrically connected to an arithmetic-logic unit via an electrical circuit. In the present embodiment, each contact  106  is connected to a controller  117  (see  FIG. 1 ) provided in the cartridge-attachment section  110 . The controller  117  may include a CPU, a ROM, and a RAM, for example. The contacts  106  are engaged with the corresponding electrodes  65  when the ink cartridge  30  is attached to the case  101 . When in contact with the corresponding electrodes  65 , the contacts  106  are electrically connected to the corresponding electrodes  65 , so that a voltage Vc is applied to one of the electrodes  65 ; another one of the electrodes  65  is grounded; signals are exchanged between the controller  117  and another one of the electrodes  65 ; and power is supplied to another one of the electrodes  65 . Due to establishment of the electrical connection between the contacts  106  and the electrodes  65 , the controller  117  is electrically accessible to the data stored in an IC of each ink cartridge  30 . Outputs from the respective contacts  106  through the electrical circuits are configured to be inputted into the controller  117 . 
     &lt;Rod  125 &gt; 
     As illustrated in  FIG. 4 , each rod  125  is provided at the end wall of the case  101  at a position upward of the corresponding ink needle  102  for each insertion space  111 . Each rod  125  has a generally cylindrical shape and protrudes rearward from the end wall of the case  101 . In a state where the ink cartridges  30  are attached to the cartridge-attachment section  110 , that is, when the ink cartridges  30  are in the attached posture, the rods  125  are respectively received in air communication ports  96  (described later) of the corresponding ink cartridges  30 . 
     &lt;Optical Sensor  113 &gt; 
     As illustrated in  FIG. 4 , the optical sensors  113  are disposed at the top wall of the case  101 . Specifically, each optical sensor  113  is disposed, for each insertion space  111 , at a position rearward of the corresponding rod  125  but frontward of the set of four contacts  106 . Each optical sensor  113  includes a light-emitting portion and a light-receiving portion. The light-emitting portion is arranged to oppose the light-receiving portion and is spaced apart from the light-receiving portion in the left-right direction. When the ink cartridge  30  is attached to the cartridge-attachment section  110 , a light-blocking plate  67  of the attached ink cartridge  30  is located between the light-emitting portion and the light-receiving portion of the corresponding optical sensor  113 . In other words, the light-emitting portion and the light-receiving portion are arranged to oppose each other with the light-blocking plate  67  of the ink cartridge  30  attached to the cartridge-attachment section  110  interposed between the light-emitting portion and the light-receiving portion. 
     The optical sensor  113  is configured to output different detection signals depending on whether or not light emitted in the left-right direction from the light-emitting portion is received by the light-receiving portion. For example, the optical sensor  113  outputs a low-level signal when the light emitted from the light-emitting portion is not received at the light-receiving portion (that is, when an intensity of the light received at the light-receiving portion is less than a predetermined intensity). On the other hand, the optical sensor  113  outputs a high-level signal when the light emitted from the light-emitting portion is received by the light-receiving portion (that is, when the intensity of the received light is equal to or greater than the predetermined intensity). 
     &lt;Lock Shaft  145 &gt; 
     As illustrated in  FIG. 4 , a lock shaft  145  is also provided at the case  101 . The lock shaft  145  extends in the left-right direction at a position near the top wall and the opening  112  of the case  101 . The lock shaft  145  is disposed rearward of the contacts  106 . The lock shaft  145  is a rod-like member extending in the left-right direction. For example, the lock shaft  145  is a columnar-shaped metal. The lock shaft  145  has both ends that are fixed to walls defining both ends of the case  101  in the left-right direction. Accordingly, the lock shaft  145  is not movable (for example, is not pivotable) relative to the case  101 . The lock shaft  145  extends in the left-right direction across the four insertion spaces  111  respectively corresponding to the four ink cartridges  30 . In each of the insertion spaces  111 , a space is provided around the lock shaft  145 . Thus, a locking surface  151  (described later) of each ink cartridge  30  can access the lock shaft  145  by moving upward or rearward. 
     The lock shaft  145  functions to maintain the ink cartridges  30  attached to the cartridge-attachment section  110  in the attached state. When the ink cartridge  30  is inserted into the cartridge-attachment section  110  and pivoted into a posture to be used thereby (i.e., attached posture), the ink cartridge  30  is brought into engagement with the lock shaft  145  in the corresponding insertion space  111 . Further, the lock shaft  145  holds the ink cartridge  30  in the attached posture in the cartridge-attachment section  110  against urging forces of coil springs  78  and  98  (described later) of the ink cartridge  30  that push the ink cartridge  30  as a whole rearward. 
     &lt;Positioning Portion  107 &gt; 
     As illustrated in  FIG. 4 , the positioning portions  107  are arranged near the top wall of the case  101 . Each positioning portion  107  is disposed between the corresponding set of contacts  106  and the lock shaft  145  in the front-rear direction. The positioning portions  107  protrude downward from the top wall of the case  101 . The positioning portions  107  are integrally formed with the case  101 . Each positioning portion  107  has a lower end surface that is configured to abut against a contact surface  84  of the corresponding ink cartridge  30  in the state where the ink cartridge  30  is attached to the cartridge-attachment section  110  (in the attached posture). The lower end surface of each positioning portion  107  is positioned slightly upward relative to the lower ends of the corresponding contacts  106 . 
     &lt;Gate  108 &gt; 
     As illustrated in  FIGS. 3 and 4 , the gates  108  (specifically, gates  108 C,  108 M,  108 Y and  108 K) are provided near the top wall of the case  101 . Each gate  108  protrudes downward from a wall defining an upper edge of each insertion space  111 . Each gate  108  is provided for each insertion space  111  at a position between the corresponding optical sensor  113  and the set of contacts  106  in the front-rear direction. Referring to  FIG. 3 , each gate  108  includes a pair of opposing walls  118  and a slit  119  provided between the opposing walls  118 . The opposing walls  118  extend respectively in the left-right direction from neighboring partitioning members that oppose each other in the right-left direction and that define the corresponding insertion space  111 , such as the neighboring two plates  104 . The opposing walls  118  extend in the up-down direction and are paired to oppose each other in the left-right direction with a gap defined therebetween. This gap between the paired opposing walls  118  serve as the slit  119  in each gate  108 . Put another way, each slit  119  is defined by two opposing end faces of the paired opposing walls  118  extending in the up-down direction. However, the slits  119  (slits  119 C,  119 M,  119 Y and  119 K) are formed at different positions from one another in the left-right direction in the respective insertion spaces  111 C,  111 M,  111 Y and  111 K. Specifically, relative positions between the slits  119  (slits  119 C,  119 M,  119 Y and  119 K) and the corresponding contacts  106  in the respective insertion spaces  111 C,  111 M,  111 Y and  111 K in the left-right direction are different from one another. More specifically, for example, referring to  FIG. 3 , while the slit  119 M of the gate  108 M is positioned at a generally left-right center of the insertion space  111 M, the slit  119 C of the gate  108 C is positioned offset from a left-right center of the insertion space  111 C (i.e., rightward relative to the left-right center of the insertion space  111 C). The respective slits  119 C,  119 M,  119 Y and  119 K in the insertion spaces  111 C,  111 M,  111 Y and  111 K are formed at such left-right positions that correspond to left-right positions of the light-blocking plates  67  ( 67 C,  67 M,  67 Y and  67 K) of the ink cartridges  30 C,  30 M,  30 Y and  30 K, respectively. Each slit  119  has a width in the left-right direction that is larger than a width of the corresponding light-blocking plate  67  in the left-right direction (defined as a width W 1  illustrated in  FIGS. 14 and 15 ). That is, the light-blocking plates  67 C,  67 M,  67 Y and  67 K are allowed to pass through the corresponding slits  119 C,  119 M,  119 Y and  119 K in the front-rear direction. 
     &lt;Tank  103 &gt; 
     As illustrated in  FIG. 1 , each tank  103  is provided forward of the case  101  and is connected to the corresponding ink needle  102 . The tank  103  has a box-like shape that allows ink to be stored therein. An atmosphere communication port  124  is formed at an upper portion of each tank  103  so that the tank  103  can be opened to the atmosphere through the atmosphere communication port  124 . The tank  103  has an inner space that communicates with the inner space of the ink needle  102 . With this structure, ink can flow out from the ink cartridge  30  through the ink needle  102  and is stored in the tank  103 . Each tank  103  is also connected to the corresponding ink tube  20 . Thus, the ink stored in the inner space of each tank  103  is supplied to the recording head  21  through the corresponding ink tube  20 . 
     &lt;Cover  114  and Cover Sensor  115 &gt; 
     As illustrated in  FIG. 1 , the cartridge-attachment section  110  also includes a cover  114 , and a cover sensor  115 . The cover  114  is configured to open and close the opening  112  of the case  101 . The cover  114  extends in the left-right direction. The cover  114  is pivotally movable relative to the case  101  about a shaft  116  provided near a lower end of the case  101 . The cover  114  has a substantially flat-plate shape and constitutes a part of the outer surface of the printer  10 . The cover sensor  115  is configured to detect whether or not the cover  114  is in a closing position that closes the opening  112 . 
     In a state illustrated in  FIG. 1 , the cover  114  is at the closing position. The cover  114  at the closing position extends upward relative to the shaft  116 . When the cover  114  is at the closing position, the opening  112  of the case  101  is closed. At this time, a user cannot perform insertion and removal of the ink cartridges  30  relative to the cartridge-attachment section  110 . The cover sensor  115  is disposed at such a position that the cover sensor  115  can detect presence of a portion of the cover  114  at the closing position. To move the cover  114  from the closing position to an opening position opening the opening  112 , the cover  114  is pivoted about the shaft  116  to move an upper end portion of the cover  114  downward. The cover  114  at the opening position extends substantially horizontally in the rearward direction  52  relative to the shaft  116 . When the cover  114  is pivoted from the closing position toward the opening position, the cover  114  goes out of a range within which the cover sensor  115  can detect the cover  114 . When the cover  114  is at the opening position, the opening  112  of the case  101  is opened. In this state, the user can insert/remove the ink cartridges  30  into/from the cartridge-attachment section  110 . 
     &lt;Controller  117 &gt; 
     As illustrated in  FIG. 1 , the cartridge-attachment section  110  also includes a controller  117 . As described earlier, the controller  117  is an arithmetic-logic unit including a CPU, a memory, and the like, for example. The controller  117  may be configured as a controller of the printer  10 . The controller  117  is configured to receive signals outputted from the optical sensor  113  and the cover sensor  115 . In response to receipt of a signal from the cover sensor  115  indicating that the cover  114  is at the closing position, the controller  117  is configured to determine a type of the ink cartridge  30  inserted into the insertion space  111  based on a signal outputted from the optical sensor  113 . Details of the detection performed by the controller  117  will be described later. 
     &lt;Ink Cartridge  30 &gt; 
     The ink cartridge  30  is a container configured to store ink therein. The ink cartridges  30 C,  30 M,  30 Y and  30 K have generally the same structure as each other, but have some differences from one another. 
     Hereinafter, in order to describe a configuration common to all of the ink cartridges  30 , a structure of the ink cartridge  30 M will be first described as an illustrative example, with reference to  FIGS. 4 to 10 . Subsequently, a detailed structure of the ink cartridge  30 K, and differences among the ink cartridges  30 C,  30 M,  30 Y and  30 K will be described. 
     The ink cartridge  30  is inserted into and attached to the cartridge-attachment section  110  in a posture illustrated in  FIGS. 4 to 10 . This posture of the ink cartridge  30  in the attached state (attached posture) will also be called an upright posture, hereinafter, whenever necessary. That is, the upright posture corresponds to the attached posture. In other words, the ink cartridge  30  is in the upright posture when the ink cartridge  30  is attached to the cartridge-attachment section  110 . In the upright posture or in the attached posture, the ink stored in the first ink chamber  32  of the ink cartridge  30  can flow out therefrom to be supplied into the corresponding ink needle  102  through the ink supply port  71  of the ink supply potion  34 . That is, the ink cartridge  30  can be used in the printer  10  when in the attached posture or in the upright posture. 
     Specifically, as will be described later, the ink cartridge  30  includes a front wall  40 , a rear wall  41 , an upper wall  39 , and a bottom wall  42 . When the ink cartridge  30  ( 30 M) is in the upright posture or in the attached posture illustrated in  FIGS. 4 to 10 , a direction from the rear wall  41  toward the front wall  40  coincides with the frontward direction  51 ; a direction from the front wall  40  toward the rear wall  41  coincides with the rearward direction  52 ; a direction from the upper wall  39  toward the bottom wall  42  coincides with the downward direction  53 , and a direction from the bottom wall  42  toward the upper wall  39  coincides with the upward direction  54 . 
     In the upright posture of the ink cartridge  30 , the front wall  40  faces frontward or is oriented in the frontward direction  51 ; the rear wall  41  is spaced away from the front wall  40  in the front-rear direction; the upper wall  39  is positioned between the front wall  40  and the rear wall  41  in the front-rear direction; and the bottom wall  42  is spaced away from the upper wall  39  in the up-down direction. The bottom wall  42  is positioned between the front wall  40  and the rear wall  41  in the front-rear direction. In other words, in the upright posture of the ink cartridge  30 , the front wall  40  faces frontward, the rear wall  41  faces rearward, the bottom wall  42  faces downward, and the upper wall  39  faces upward. 
     More specifically, when the ink cartridge  30  is in the attached posture or in the upright posture, a front surface of the front wall  40  constitutes an front surface of the ink cartridge  30 ; a rear surface of the rear wall  41  constitutes a rear surface of the ink cartridge  30 ; an upper surface of the upper wall  39  constitutes an upper surface of the ink cartridge  30 ; and a bottom surface of the bottom wall  42  constitutes a bottom surface of the ink cartridge  30 . That is, in the upright posture (attached posture) of the ink cartridge  30 , the front surface of the front wall  40  faces frontward, the rear surface of the rear wall  41  faces rearward, the bottom surface of the bottom wall  42  faces downward, and the upper surface of the upper wall  39  faces upward. 
     Hereinafter, for simplifying explanation, whenever necessary, the front surface of the front wall  40  will be referred to as the front surface  40 ; the rear surface of the rear wall  41  will be simply to as the rear surface  41 ; the upper surface of the upper wall  39  will be referred to as the upper surface  39 ; and the bottom surface of the bottom wall  42  will be referred to as the bottom surface  42 . 
     As illustrated in  FIGS. 4 to 10 , the ink cartridge  30  ( 30 M) includes a cartridge body  31  of a substantially rectangular parallelepiped shape. The cartridge body  31  in the upright posture has a generally flat shape having a height in the up-down direction (in the gravitational direction), a width in the left-right direction, and a depth in the front-rear direction, the width being smaller than the height and the depth. The cartridge body  31  includes the front wall  40 , the rear wall  41 , the upper wall  39 , the bottom wall  42  and side walls  37  and  38 . 
     In a state where the ink cartridge  30  is in the upright posture or in the attached state, the front surface  40  (front surface of the front wall  40 ) faces frontward, the rear surface  41  (the rear surface of the rear wall  41 ) faces rearward, the upper surface  39  (the upper surface of the upper wall  39 ) faces upward, and the bottom surface  42  (the bottom surface of the bottom wall  42 ) faces downward. The side walls  37  and  38  extend to intersect with the front wall  40  and rear wall  41  so as to connect the front wall  40  and the rear wall  41 . In the upright posture (attached posture) of the ink cartridge  30 , outer surfaces of the side walls  37  and  38  faces rightward and leftward, respectively. 
     More specifically, in the present embodiment, the cartridge body  31  includes a lower case  31 L, and an upper cover  31 U fitted to the lower case  31 L. Within the lower case  31 L, a first ink chamber  32  and the second ink chamber  33  are formed (see  FIG. 8 ). The lower case  31 L includes the bottom wall  42 , and the upper cover  31 U includes the upper wall  39 . In the cartridge body  31 , at least a portion of the rear wall  41  constituting the lower case  31 L is capable of transmitting light so that a liquid surface of the ink stored in the first ink chamber  32  and second ink chamber  33  can be viewed from outside. An upper surface of the upper cover  31 U constitutes the upper surface  39  of the cartridge body  31 . 
     As illustrated in  FIGS. 7 and 8 , the rear surface  41  includes an upper portion  41 U and a lower portion  41 L. The upper portion  41 U is positioned upward of the lower portion  41 L. The lower portion  41 L is positioned forward of the upper portion  41 U. Each of the upper and lower portions  41 U and  41 L is a flat surface. The upper portion  41 U and lower portion  41 L cross each other but are not orthogonal to each other. Specifically, the lower portion  41 L is inclined relative to the up-down direction so as to extend closer to the front surface  40  toward the lower surface  42 . In other words, in the present embodiment, the upper portion  41 U constitutes a rearmost portion of the rear surface  41  in the rearward direction  52 . Further, in the present embodiment, the upper portion  41 U also constitutes a rearmost portion of the ink cartridge  30 . In  FIG. 10 , a rearmost point of the ink cartridge  30  is illustrated as a point P 5 . 
     As illustrated in  FIGS. 4 and 8 , the lower surface  42  is inclined relative to the front-rear direction. Specifically, assuming the lower surface  42  has a front end  42 F and a rear end  42 R, the bottom surface  42  is inclined relative to the front-rear direction such that the front end  42 F is positioned downward relative to the rear end  42 R. The front end  42 F of the lower surface  42  (inclined surface) is positioned frontward relative to the IC board  64 , as will be described later. The rear end  42 R of the lower surface  42  (inclined surface) is connected to a lower end of the lower portion  41 L of the rear surface  41 . Preferably, the lower surface  42  is inclined relative to the horizontal direction at an angle of 2° to 4°. 
     As illustrated in  FIGS. 6 and 7 , the cartridge body  31  also includes a sub-lower wall  48  and a connecting wall  49  that belong to the lower case  31 L. The sub-lower wall  48  is positioned upward of the lower wall  42 . The sub-lower wall  48  extends rearward from a lower end of the front wall  40 . In the present embodiment, a front end of the sub-lower wall  48  is positioned frontward of a front end of the ink supply portion  34 , and a rear end of the sub-lower wall  48  is positioned rearward of the front end of the ink supply portion  34 . The connecting wall  49  connects the lower wall  42  (lower surface  42 ) and the sub-lower wall  48 . The ink supply portion  34  extends forward from the connecting wall  49  at a position downward of the sub-lower wall  48  and upward of the lower surface  42 . Note that the front end of the sub-lower wall  48  may be arranged at an arbitrary position, for example, at a position rearward of the front end of the ink supply portion  34 . 
     As illustrated in  FIGS. 4, 6-9A and 10 , the upper wall  39  belonging to the upper cover  31 U has a stepped upper surface. Specifically, the upper surface  39  (upper surface of the upper wall  39 ) includes a rearward portion that is raised upward relative to a frontward portion of the upper surface  39 . Hereinafter, the rearward portion will be referred to as a raised portion  39 A, whenever necessary. 
     A first protrusion  43  is provided on the upper surface  39  of the cartridge body  31 . More specifically, the first protrusion  43  is disposed at the raised portion  39 A of the upper surface  39 . The first protrusion  43  extends in the front-rear direction and is positioned at a generally left-right center of the upper surface  39  (raised portion  39 A). The first protrusion  43  has a rear end whose surface faces rearward. This surface serves as the locking surface  151 . 
     The locking surface  151  is a plane parallel to the gravitational direction (downward direction  53 ). That is, the locking surface  151  extends in the up-down direction and in the left-right direction. In the present embodiment, the locking surface  151  extends upward from the upper surface  39  (raised portion  39 A) of the cartridge body  31 . In a state where the ink cartridge  30  is attached to the cartridge-attachment section  110 , the locking surface  151  facing rearward is in contact with the lock shaft  145  from frontward thereof in an engaging region E (illustrated in  FIG. 5A ). In other words, the locking surface  151  has the engaging region E configured to engage the lock shaft  145  in a state where the ink cartridge  30  is attached to the cartridge-attachment section  110 . The engaging region E is positioned upward relative to the IC board  64  in the attached posture. The contact (engagement) between the locking surface  151  (engaging region E) and the lock shaft  145  in the front-rear direction enables the ink cartridge  30  to be held in the cartridge-attachment section  110  against the biasing force of a coil spring  78  of the ink supply potion  34 , as will be described later. Although the locking surface  151  contacts the lock shaft  145  at the engaging region (surface contact) in the embodiment, the locking surface  151  may make contact with the lock shaft  145  at a specific point (point contact), as long as the locking surface  151  can receive the rearward urging force of the coil spring  78  to maintain the ink cartridge  30  in the attached state. As an example, the locking surface  151  may make contact with the lock shaft  145  on an engaging point P 3  within the engaging region E (see  FIG. 5A ). 
     The first protrusion  43  also includes a horizontal surface  154  and an inclined surface  155 . The horizontal surface  154  extends frontward from an upper edge  151 U of the locking surface  151 . That is, the horizontal surface  154  is provided frontward of the locking surface  151 . The horizontal surface  154  is a surface extending in the front-rear direction and in the left-right direction. The horizontal surface  154  is a surface that is positioned farthest away from the upper surface  39  among surfaces constituting the first protrusion  43 . The horizontal surface  154  has a left-right dimension that is smaller than a front-rear dimension thereof. The inclined surface  155  extends frontward and downward from a front edge of the horizontal surface  154 . That is, the front edge of the horizontal surface  154  is the rear edge of the inclined surface  155  (denoted as a point P 1  in  FIGS. 7, 8, 9A and 10 ). The inclined surface  155  is disposed frontward relative to the horizontal surface  154 . The inclined surface  155  is a surface facing upward and forward. Preferably, the inclined surface  155  is included relative to the horizontal direction at an angle of 15° to 25°. Put another way, the locking surface  151  and the inclined surface  155  are connected to each other via the horizontal surface  154 . Thus, a boundary edge between the locking surface  151  and inclined surface  155  does not constitute a ridge-like shape. The inclined surface  155  is positioned between the IC board  64  and the locking surface  151  in the front-rear direction. During insertion of the ink cartridge  30  into the cartridge-attachment section  110 , the lock shaft  145  is smoothly guided toward the rear beyond the locking surface  151  while abutting against and sliding along the inclined surface  155  and horizontal surface  154 . 
     Further, the cartridge body  31  (upper cover  31 U) also includes a pair of sub-upper walls  91  extending in the front-rear direction. One of the sub-upper walls  91  is located frontward of the upper wall  39  (to be referred to as a front sub-upper wall  91 F), while the other sub-upper wall  91  is located rearward of the upper wall  39  (to be referred to as a rear sub-upper wall  91 R). The front sub-upper wall  91 F has a front end connected to an upper end of the front wall  40 , and a rear end connected to a front end of the upper wall  39  via a connecting wall  95  extending in the up-down direction. The rear sub-upper wall  91 R has a rear end connected to an upper end of the rear wall  41 . The front and rear sub-upper walls  91 F and  91 R are positioned downward relative to a center portion of the upper surface  39  in the front-rear direction. 
     An operation portion  90  is also provided on the upper surface  39  (raised portion  39 A) of the cartridge body  31  at a position rearward of the locking surface  151 . The operation portion  90  is disposed upward relative to the rear sub-upper wall  91 R (upper surface of the rear sub-upper wall  91 R) and is spaced apart therefrom in the front-rear direction. The operation portion  90  has a generally flat plate-like shape. Specifically, the operation portion  90  protrudes upward from the raised portion  39 A of the upper surface  39 , and is then bent obliquely rearward and downward. The operation portion  90  protrudes upward from the raised portion  39 A of the upper surface  39  up to the same degree as the first protrusion  43  protrudes from the raised portion  39 A in the up-down direction. Here, “the same degree” means that an upper edge of the operation portion  90  is positioned higher by 0 to 1 mm, or lower by 0 to 1 mm, relative to the upper edge of the first protrusion  43  (i.e., relative to the horizontal surface  154 ). The operation portion  90  is connected to a lower edge  151 L of the locking surface  151  via a surface  156  constituting part of the upper surface  39  (or, part of the raised portion  39 A). A rib  94  is provided between the operation portion  90  and the rear sub-upper wall  91 F. The rib  94  connects the operation portion  90  and the rear sub-upper wall  91 R in the up-down direction and extends in the front-rear direction. The rib  94  has a dimension in the left-right direction that is smaller than each of a dimension of the operation portion  90  and a dimension of the rear sub-upper wall  91 R in the left-right direction. 
     The operation portion  90  has a surface that faces diagonally upward and rearward. This surface serves as an operation surface  92 . The operation surface  92  and the rear sub-upper wall  91 R are aligned with each other at least partially in the up-down direction. In other words, when the ink cartridge  30  is viewed from above, the operation surface  92  and the rear sub-upper wall  91 R overlap with each other. On the operation surface  92 , a plurality of projections, e.g., a plurality of ridges  93  extending in the left-right direction is formed to be spaced apart from one another in the front-rear direction. These ridges  93  (as the plurality of projections) allow the user to easily visually recognize the operation surface  92 . The ridges  93  can also serve to prevent the user&#39;s finger from slipping over the operation surface  92  when he or she operates the operation surface  92 . 
     The operation surface  92  is visible when the ink cartridge  30  is viewed from rearward and from upward. The user operates the operation surface  92  in order to remove the ink cartridge  30  attached to the cartridge-attachment section  110  therefrom. The operation portion  90  is fixed to the cartridge body  31  so as not to move relative to the cartridge body  31 . For example, the operation portion  90  may be formed integrally with the cartridge body  31  so as not to pivot relative to the cartridge body  31 . Thus, a force applied from the user to the operation surface  92  is directly transmitted to the cartridge body  31  without changing a direction of the force. 
     As illustrated in  FIGS. 4, 6-8, 9A and 10 , a second protrusion  83  is also provided at the upper surface  39  (raised portion  39 A) of the cartridge body  31  at a position forward of the first protrusion  43 . The second protrusion  83  is provided at the upper cover  31 U. The second protrusion  83  extends forward from the front end of the first protrusion  43 . That is, the second protrusion  83  and the first protrusion  43  are connected to each other. The second protrusion  83  is formed at the same left-right position as the first protrusion  43 . The second protrusion  83  supports the IC board  64 . The second protrusion  83  has a rear end portion whose upper surface serves as the contact surface  84 . Put another way, the contact surface  84  is connected to a lower end (front end) of the inclined surface  155  and extends frontward therefrom. The contact surface  84  faces upward (i.e., a flat upper surface). That is, the contact surface  84  is positioned between the IC board  64  and the locking surface  151  in the front-rear direction. In a state where the ink cartridge  30  is attached to the cartridge-attachment section  110 , the contact surface  84  is in contact with the positioning portion  107  of the cartridge-attachment section  110 , thereby providing positioning of the ink cartridge  30  relative to the cartridge-attachment section  110  with respect to the up-down direction. The contact surface  84  is a surface that is not movable relative to the IC board  64 . In the present embodiment, the contact surface  84  is made of the same material as a member that supports the IC board  64 , i.e., the upper cover  31 U. The inclined surface  155  may have an arbitrary configuration. For example, a continuous surface need not be formed between the contact surface  84  and the locking surface  151 . Alternatively, for example, the second protrusion  83  having the contact surface  84  and the first protrusion  43  having the locking surface  151  may not be formed to be continuous with each other. That is, the second protrusion  83  and the first protrusion  43  may be provided separately on the upper surface  39  so as to protrude upward therefrom. 
     Note that, the front surface, rear surface, top surface, bottom surface, and side surfaces constituting the ink cartridge  30  need not be configured as one flat plane, respectively. That is, the front surface of the ink cartridge  30  can be any surface(s) that can be seen when the ink cartridge  30  in its upright posture is viewed from its front side, and that is(are) positioned frontward relative to a front-rear center of the ink cartridge  30 . In the present embodiment, the front surface  40  (i.e., the front surface of the front wall  40  connecting the sub-lower wall  48  and front sub-upper wall  91 F) and a front surface of the connecting wall  49  connecting the sub-lower wall  48  and the bottom wall  42  (bottom surface  42 ) constitute the front surface of the ink cartridge  30 . Also, the connecting wall  95  connecting the front sub-upper wall  91 F and the upper wall  39  also constitutes the front surface of the ink cartridges  30 . On the other hand, the ink cartridge  30  may not have the sub-lower wall  48  and the front sub-upper wall  91 F. In other words, the front surface  40  of the ink cartridge  30  may be configured as one surface continuously connecting the upper surface  39  and the lower surface  42 . 
     Likewise, the rear surface of the ink cartridge  30  can be any surface(s) that can be seen when the ink cartridge  30  in its upright posture is viewed from its rear side, and that is(are) positioned rearward relative to the front-rear center of the ink cartridge  30 . The upper surface of the ink cartridge  30  can be any surface(s) that can be seen when the ink cartridge  30  in its upright posture is viewed from above, and that is(are) positioned upward relative to a center of the ink cartridge  30  in the up-down direction. The lower surface of the ink cartridge  30  can be any surface(s) that can be seen when the ink cartridge  30  in its upright posture is viewed from below, and that is(are) positioned downward relative to the center of the ink cartridge  30  in the up-down direction. The same is applied to the side surfaces of the ink cartridge  30 . 
     As illustrated in  FIGS. 4, 6-8, 9A and 10 , the light-blocking plate  67  is also provided at the upper surface  39  (upper surface of the upper wall  39 ). Specifically, the light-blocking plate  67  protrudes upward from the upper surface  39  at a position frontward relative to the raised portion  39 A. In the present embodiment, the light-blocking plate  67  is integrally formed with the upper cover  31 U. The light-blocking plate  67  extends in the front-rear direction. The light-blocking plate  67  is positioned frontward relative to the second protrusion  83 . The light-blocking plate  67  is connected to the raised portion  39 A that supports the second protrusion  83  on which the IC board  64  is disposed. In other words, the raised portion  39 A, which constitutes a part of the upper surface  39 , also serves as a supporting portion that supports the IC board  64 . 
     The light-blocking plate  67  is also positioned frontward and downward relative to the IC board  64 . In the present embodiment, the light-blocking plate  67  is a plate made of resin containing a colored material capable of absorbing light (carbon black pigment, for example). Alternatively, the light-blocking plate  67  may be configured by attaching a material that cannot transmit light, such as aluminum, to a side surface of a plate capable of transmitting light. 
     The light-blocking plate  67  has a flat plate-like shape whose left-right dimension (the width W 1  illustrated in  FIG. 14 ) is smaller than a front-rear dimension thereof. The light-blocking plate  67  has a front surface  67   b , left and right side surfaces  67   a , an upper surface  67   c , and a sloped surface  67   d.    
     The front surface  67   b  of the light-blocking plate  67  is a surface facing frontward in the upright posture of the ink cartridge  30 . The front surface  67   b  serves as an interfering surface  67   b  of the ink cartridge  30 . That is, the interfering surface  67   b  faces frontward in the upright posture of the ink cartridge  30 . The interfering surface  67   b  extends upward from the upper surface  39  of the cartridge body  31 . Put another way, the interfering surface  67   b  is a plane extending upward from the upper surface  39  of the cartridge body  31 . The interfering surface  67   b  is a flat plane extending in the up-down direction and in the left-right direction. The interfering surface  67   b M of the ink cartridge  30 M is configured to abut against any one of the gates  108  other than the corresponding gate  108 M when the ink cartridge  30 M is inserted into any one of the insertion spaces  111  different from the specified insertion space  111 M. That is, the interfering surface  67   b M of the ink cartridge  30 M is designed to abut against the gate  108 C, or the gate  108 Y, or the gate  108 K, in case that the ink cartridge  30 M is inserted into the insertion space  111 C, or the insertion space  111 Y, or the insertion space  111 K. More specifically, the interfering surface  67   b M of the ink cartridge  30 M is designed to abut against any one of the gate  108 C, the gate  108 Y and the gate  108 K, during insertion of the ink cartridge  30 M into any one of the insertion space  111 C, the insertion space  111 Y, and the insertion space  111 K other than the insertion space  111 M, i.e., in a process of insertion of the ink cartridge  30 M until the ink cartridge  30 M is completely attached to the cartridge-attachment section  110  to be at the attached posture. 
     The both side surfaces  67   a  of the light-blocking plate  67  are positioned rearward of the interfering surface  67   b . The both side surfaces  67   a  facing rightward and leftward, respectively, serve as light-blocking surfaces  67   a  of the light-blocking plate  67 . The sloped surface  67   d  is a sloped surface that connects a front edge of the upper surface  67   c  and an upper edge of the interfering surface  67   b . The sloped surface  67   d  faces forward and upward. The rear edge of the sloped surface  67   d , i.e., the front edge of the upper surface  67   c  (denoted as a point P 2  in  FIGS. 7, 8, 9A, 10 ) is the highest portion (i.e. uppermost portion) in the light-blocking plate  67 . The upper edge of the interfering surface  67   b  is positioned slightly downward relative to the upper surface (horizontal surface  154  and inclined surface  155 ) of the first protrusion  43 . The interfering surface  67   b  is positioned forward and downward of the electrodes  65  of the IC board  64 . 
     As illustrated in  FIGS. 6 and 9A , the both side surfaces  67   a  (light-blocking surfaces  67   a ) of the light-blocking plate  67  extend rearward from left and right ends of the interfering surface  67   b  (also see FIG. and  12 ). That is, the interfering surface  67   b  and each side surface  67   a  are aligned with each other in the front-rear direction. Further, referring to  FIG. 8 , the interfering surface  67   b  is positioned rearward relative to an inner surface  40 R (rear surface) of the front wall  40 , the inner surface  40 R defining a front edge of the first ink chamber  32 , as will be described later. 
     The light-blocking plate  67  is configured to block the light of the optical sensor  113  traveling in the left-right direction from the light-emitting portion to the light-receiving portion. More specifically, when the light emitted from the light-emitting portion of the optical sensor  113  is incident on the right or left side surface  67   a  of the light-blocking plate  67  before arriving at the light-receiving portion, the intensity of light received at the light-receiving portion is less than a predetermined intensity, for example, zero. Note that the light-blocking plate  67  may completely block the light traveling in the left-right direction, or may partially attenuate the light, may refract the light to change a traveling direction thereof, or may fully reflect the light. 
     As illustrated in  FIGS. 6-9A and 10 , the light-blocking plate  67  ( 67 M) is formed with the cutout  66  ( 66 M). The cutout  66  is configured to allow light to pass therethrough in the left-right direction (light-transmission portion). The cutout  66  is a space provided by cutting out a portion of an upper end portion of the light-blocking plate  67 . In other words, the cutout  66  is recessed downward from the upper surface  67   c  of the light-blocking plate  67 . The cutout  66  extends in the front-rear direction and in the left-right direction. The cutout  66  is formed at a position coincident with the corresponding optical sensor  113  in the left-right direction when the ink cartridge  30  having the light-blocking plate  67  provided with the cutout  66  is mounted in the corresponding insertion space  111 . In other words, in a state where the ink cartridge  30  is attached to the cartridge-attachment section  110 , the cutout  66  of the light-blocking plate  67  of the attached ink cartridge  30  is located between the light-emitting portion and the light-receiving portion of the corresponding optical sensor  113 . Hence, the light from the light-emitting portion of the corresponding optical sensor  113  is not blocked by the cutout  66 , and is received at the light-receiving portion. 
     Note that, the light-blocking plate  67  of the present embodiment is provided with the cutout  66  as the light-transmission portion. However, the light-transmission portion of the light-blocking plate  67  may not necessarily be provided as a cutout, as long as light from the light-emitting portion of the optical sensor  113  can pass through the light-transmission portion. For example, the light-transmission portion may be provided as a through-hole penetrating a portion of the light-blocking plate  67  in the left-right direction, or as a transparent plate provided in the light-blocking plate  67 . 
     More precisely, in the present embodiment, a portion of each side surface  67   a  enclosed by a broken line D in  FIG. 9A  serves as a light-blocking portion of the light-blocking plate  67 . That is, the light emitted from the light-emitting portion of the corresponding optical sensor  113  is configured to be incident on this portion D of one of the light-blocking surfaces  67   a  during insertion of the ink cartridge  30 . This portion D can block or attenuate the incident light from the optical sensor  113  during insertion of the ink cartridge  30  and is therefore configured to be detected by the controller  117  through the optical sensor  113 . This portion D may serve as a detection surface D of the light-blocking plate  67 . This detection surface D has a rear edge Dr that also constitutes a front edge of the cutout  66  (light-transmission portion). In the attached state of the ink cartridge  30 , the optical sensor  113  is positioned to oppose the cutout  66 . This means that, in the light-blocking surface  67   a , the light from the optical sensor  113  is incident on the detection surface D but cannot be incident on a portion positioned rearward of the cutout  66 . 
     The light-blocking plate  67  may not be formed with the cutout  66 . For example, the light-blocking plate  67  of the ink cartridge  30 C depicted in  FIG. 17  is not formed with the cutout  66 . In case that the cutout  66  is not formed in the light-blocking plate  67 , one of the side surfaces  67   a  of the light-blocking plate  67  opposes the light-emitting portion of the optical sensor  113  in the left-right direction when the ink cartridge  30  is attached to the cartridge-attachment section  110 . Thus, the light emitted from the light-emitting portion of the optical sensor  113  is blocked by the light-blocking plate  67  and is not received at the light-receiving portion. 
     The ink cartridges  30  may or may not include the cutout  66  depending on types of the ink cartridges  30 . For example, the types of the ink cartridges  30  may vary depending on colors of ink, initial amounts of ink (larger or smaller), or types of ink (pigment ink or dye ink) stored in the ink cartridges  30 . In the present embodiment, the ink cartridges  30  are, for each color, configured to store different initial amounts of ink. Specifically, the ink cartridges  30 M storing magenta ink can be classified into two types: larger-amount type and smaller-amount type. The ink cartridge  30 M of the larger-amount type stores a larger amount of ink in the first ink chamber  32  as its initial amount of ink than the initial amount of ink stored in the first ink chamber  32  of the ink cartridge  30 M of the smaller-amount type. In this example, the ink cartridge  30 M of the larger-amount type includes the light-blocking plate  67 M formed with the cutout  66 M, while the ink cartridge  30 M of the smaller amount type includes the light-blocking plate  67 M without the cutout  66 M. In the present embodiment, the type of the ink cartridge  30  (i.e., the initial amount of ink) attached to the cartridge-attachment section  110  can be determined based on presence or absence of the cutout  66  in the light-blocking plate  67 , as will be described later in detail. 
     As illustrated in  FIGS. 6 to 8 , the IC board  64  is disposed at the upper end of the second protrusion  83  and between the light-blocking plate  67  and the first protrusion  43 . The IC board  64  is positioned in a recess that is recessed downward and that is formed in the second protrusion  83 , the recess being positioned frontward of the contact surface  84 . The IC board  64  is supported by the second protrusion  83  from below. Specifically, although not depicted in detail in the drawings, a photocurable resin is filled in the recess of the second protrusion  83 , whereby the IC board  64  is adhered to the second protrusion  83 . 
     The IC board  64  includes a substrate, an IC (not illustrated), and four electrodes  65  mounted on an upper surface of the substrate, for example. The substrate is made of silicon, for example. The IC is a semiconductor integrated circuit and readably stores data indicating information relating to the ink cartridge  30 , such as a lot number, a manufacturing date, and a color of the ink. Alternatively, the IC board  64  may be formed of a flexible board (substrate) having flexibility, provided with the IC and electrodes. 
     The electrodes  65  are electrically connected to the IC. The four electrodes  65  each extend in the front-rear direction. The four electrodes  65  are arranged spaced apart from one another in the left-right direction. The four electrodes  65  are arranged on the upper surface of the substrate such that the electrodes  65  are exposed above to allow electrically access thereto from above. The electrodes  65  of the IC board  64  come into contact with the corresponding contacts  106  each at a contact point P 4  (illustrated in  FIG. 10 ) to be electrically connected thereto during insertion of the ink cartridge  30  into the cartridge-attachment section  110 , and is electrically connected to the corresponding set of contacts  106  in a state where the ink cartridge  30  is attached to the cartridge-attachment section  110 . 
     As illustrated in  FIGS. 9A and 10 , the IC board  64  is arranged rearward relative to the ink supply port  71  of the ink supply potion  34 . The IC board  64  is disposed forward of the locking surface  151 . The IC board  64  is also positioned downward of the upper edge  151 U of the locking surface  151 , but upward relative to the light-blocking plate  67 . Further, as illustrated in  FIG. 4 , the IC board  64  is positioned rearward relative to the distal end  102 E of the ink needle  102  in the frontward direction  51  in the attached posture. 
     As described above, the connecting wall  95  connects the front sub-upper wall  91 F and the upper wall  39 . That is, the connecting wall  95  extends upward from the rear end of the front sub-upper wall  91 F. The connecting wall  95  faces forward. The air communication port  96  is formed in the connecting wall  95 . That is, the air communication port  96  is disposed upward relative to a center of the dimension of the cartridge body  31  in the up-down direction. The air communication port  96  is a through-hole formed in the connecting wall  95 . The air communication port  96  has a substantially circular cross-section (see  FIG. 6 ) and has an inner diameter larger than an outer diameter of the corresponding rod  125  of the cartridge-attachment section  110 . The rod  125  is configured to enter the air communication port  96  during insertion of the ink cartridge  30  into the cartridge-attachment section  110 . 
     &lt;Internal Configuration of Cartridge Body  31 &gt; 
     As illustrated in  FIG. 8 , the first ink chamber  32 , the second ink chamber  33 , the ink valve chamber  35 , and an air valve chamber  36  are provided inside the cartridge body  31 . 
     The first ink chamber  32  and the air valve chamber  36  are partitioned by a partitioning wall  44 . The first ink chamber  32  and the second ink chamber  33  are partitioned by a partitioning wall  45 . The partitioning wall  44  and partitioning wall  45  are both walls extending in the front-rear direction and in the left-right direction. The partitioning wall  44  and partitioning wall  45  are disposed opposite to each other in the up-down direction. A through-hole  46  is formed in the partitioning wall  44 . The first ink chamber  32  and the air valve chamber  36  communicate with each other through the through-hole  46 . 
     As illustrated in  FIG. 8 , specifically, the first ink chamber  32  is a space enclosed by the following surfaces: a lower surface  44 L of the partitioning wall  44 , an upper surface  45 U of the partitioning wall  45 , and the inner surface  40 R of the front wall  40 , an inner surface  41 F of the rear wall  41  (front surface of the rear wall  41 ), and inner surfaces of the side walls  37  and  38 . The lower surface  44 L and upper surface  45 U defines upper and lower edges of the first ink chamber  32 , respectively. The inner surface  40 R, inner surface  41 F, and the inner surfaces of the side walls  37  and  38  defines front, rear and side edges of the first ink chamber  32 , respectively. The inner surface  40 R is the rear surface of the front wall  40 , i.e., a surface opposite to the front surface  40  (front surface of the front wall  40 ). The inner surface  41 F is a front surface of the rear wall  41 , i.e., a surface opposite to the rear surface  41  (rear surface of the rear wall  41 ). The inner surfaces of the side walls  37  and  38  are surfaces opposite to the outer surfaces of the side walls  37  and  38 . In  FIG. 7 , the inner surface of the side wall  38  is not illustrated. 
     The second ink chamber  33  is positioned downward of the first ink chamber  32  in the upright posture of the ink cartridge  30 . The second ink chamber  33  can store ink therein. The second ink chamber  33  has a capacity smaller than a capacity of the first ink chamber  32 . That is, a smaller amount of ink can be stored in the second ink chamber  33  than in the first ink chamber  32 . 
     The second ink chamber  33  and ink valve chamber  35  are partitioned by a partitioning wall  50 . The second ink chamber  33  communicates with the first ink chamber  32  through a communication port  47  formed in the partitioning wall  45  (see  FIG. 8 ). The second ink chamber  33  communicates with the ink valve chamber  35  through a through-hole  99  formed in the partitioning wall  50 . The partitioning wall  50  defines a rear edge of the ink valve chamber  35 , i.e., a rear edge  75 R of the ink supply potion  34  (see  FIG. 8 ). 
     The second ink chamber  33  is a space enclosed by the following surfaces: a lower surface  45 L of the partitioning wall  45 , an upper surface  42 U of the lower wall  42 , a rear surface  50 R of the partitioning wall  50 , the inner surface  41 F of the rear wall  41 , and the inner surfaces of the side walls  37  and  38 . The lower surface  45 L and upper surface  42 U define upper and lower edges of the second ink chamber  33 , respectively. The rear surface  50 R, inner surface  41 F and the inner surfaces of the side walls  37  and  38  define front, rear and side edges of the second ink chamber  33 , respectively. 
     Within the air valve chamber  36 , a valve  97  and the coil spring  98  are disposed. The air valve chamber  36  can communicate with ambient air through the air communication port  96  formed in the connecting wall  95 . The valve  97  is movable between a closing position sealing the air communication port  96  and an opening position separated from the air communication port  96 . The coil spring  98  is disposed rearward of the valve  97  so as to be capable of expanding and contracting in the front-rear direction. The coil spring  98  urges the valve  97  in the frontward direction  51  (toward the air communication port  96 ). Accordingly, in a state that no external force is applied, the valve  97  is in contact with the air communication port  96  to seal the air communication port  96 . The coil spring  98  has a spring constant that is smaller than a spring constant of the coil spring  78  of the ink supply portion  34 . 
     Incidentally, a member for sealing the air communication port  96  is not limited to the valve  97 . For example, a seal may be removably affixed to the connecting wall  95  to seal the air communication port  96 . 
     During insertion of the ink cartridges  30  into the cartridge-attachment section  110 , the rod  125  of the cartridge-attachment section  110  enters inside the air communication port  96 , thereby moving the valve  97  rearward from the closing position toward the opening position against the biasing force of the coil spring  98 . When the valve  97  is separated from the air communication port  96  by the rod  125  and is at the separating position, the first ink chamber  32  is opened to the atmosphere. 
     The ink supply portion  34  is provided at the connecting wall  49  constituting the front surface of the ink cartridge  30 . The ink supply potion  34  has a cylindrical outer shape. More specifically, the ink supply portion  34  includes a hollow cylindrical-shaped cylinder  75 , and a packing  76 . The cylinder  75  protrudes forward from the connecting wall  49 . The cylinder  75  has a front end that is opened to the outside of the ink cartridge  30 . The cylinder  75  defines an inner space therein that serves as the ink valve chamber  35 . 
     The packing  76  is provided at the open front end of the cylinder  75 . The packing  76  is a disk-shaped member and has a center portion formed with a through-hole. The packing  76  is made of an elastic material such as rubber or elastomer. The through-hole penetrates through the center portion of the packing  76  in the front-rear direction to provide a tubular-shaped inner peripheral surface that defines the ink supply port  71 . The ink supply port  71  has a diameter that is slightly smaller than an outer diameter of the ink needle  102 . 
     Within the ink valve chamber  35 , a valve  77  and the coil spring  78  are disposed. The valve  77  is movable in the front-rear direction to open and close the ink supply port  71  penetrating the center portion of the packing  76 . The coil spring  78  biases the valve  77  forward. Accordingly, without application of an external force, the valve  77  closes the ink supply port  71  of the packing  76 . 
     When the ink cartridge  30  is inserted into the cartridge-attachment section  110  in a state where the valve  77  closes the ink supply port  71 , the ink needle  102  enters the ink supply port  71 . An outer peripheral surface of the ink needle  102  entering into the ink supply port  71  is brought into contact with the inner peripheral surface defining the ink supply port  71  to provide liquid-tight seal therewith, while elastically deforming the packing  76 . When the distal end  102 E of the ink needle  102  passes through the ink supply port  71  of the packing  76  and enters inside the ink valve chamber  35 , the distal end  102 E of the ink needle  102  comes in contact with the valve  77 . As the ink cartridge  30  is further inserted into the cartridge-attachment section  110 , the distal end  102 E of the ink needle  102  moves the valve  77  rearward against the biasing force of the coil spring  78 , thereby separating the valve  77  from the ink supply port  71  to open the ink supply port  71 . Accordingly, the ink in the valve chamber  35  is allowed to flow into the inner space of the ink needle  102 . 
     Note that, instead of the valve  77 , the ink supply portion  34  may be closed with a film. In this case, the ink supply port  71  may be defined by the front end of the cylinder  75 , not by the packing  76 . Alternatively, the ink supply port  71  may be configured to be closed by a sealing member without a through-hole. In this case, the ink supply port  71  may be formed by piercing the ink needle  102  into the sealing member, and be closed by an elasticity of the sealing member itself as the ink needle  102  is removed from the sealing member. Still alternatively, the ink supply portion  34  need not be provided as a cylindrical-shaped member. For example, a through-hole may be formed in the front wall  40  to penetrate the same in a thickness direction thereof (front-rear direction). The ink supply potion is partially defined by the front wall  40 . 
     Referring to  FIG. 9A , here, assume an imaginary plane X 1  that includes the point P 1  and the point P 2  and that extends in the left-right direction. As explained above, the point P 1  denotes the boundary edge at which the inclined surface  155  and the horizontal surface  154  are connected to each other; and the point P 2  denotes the front edge of the upper surface  67   c  of the light-blocking plate  67 . In the present embodiment, the imaginary plane X 1  is inclined to extend downward toward frontward. The IC board  64  is disposed below the imaginary plane X 1 . 
     More specifically, assume a region that is defined between the imaginary plane X 1  and the upper surface  39  of the cartridge body  31 , i.e., a space that is above the upper surface  39  of the cartridge body  31  and below the imaginary plane X 1 . The IC board  64  is disposed within this region. Further, the side surfaces  67   a  of the light-blocking plate  67 , the cutout  66 , the IC board  64 , the contact surface  84 , and the inclined surface  155  are all disposed between the point P 1  and the point P 2  in the front-rear direction within the region defined between the upper surface  39  and the imaginary plane X 1  in the up-down direction. In other words, members that can be accessed from above or the left or the right side of the ink cartridge  30  are all disposed within this region. Put another way, in the ink cartridge  30  of the present embodiment, there is no member that extends to cross the imaginary plane X 1  between the point P 1  and the point P 2 . That is, the upper edge of the inclined surface  155  (point P 1 ) is the highest point, and the front edge of the upper surface  67   c  of the light-blocking plate  67  (point P 2 ) is the second highest point among all the members positioned between the point P 1  and point P 2  on the upper surface  39  of the ink cartridge  30 . 
     Specifically, the imaginary plane X 1  is defined as the highest plane among the imaginary planes each of which passes through a front protrusion and a rear protrusion and extends in the widthwise direction between the front protrusion and the rear protrusion. Here, the front protrusion is defined as the protrusion positioned frontward relative to the IC board  64  and the rear protrusion is defined as the protrusion positioned rearward relative to the IC board  64 . In other words, between the front protrusion and the rear protrusion, the imaginary plane X 1  is positioned higher than any other imaginary plane that extends in the widthwise direction and passes through the front protrusion and the rear protrusion. Accordingly, except for the members at which the point P 1  or P 2  is positioned, no member or configuration of the ink cartridge  30  crosses the imaginary plane X 1  between the points P 1  and P 2 . In the embodiment, the light-blocking plate  67  is an example of the front protrusion and the first protrusion  43  and the operation portion  90  are examples of the rear protrusion. 
     In the frontward direction  51 , the locking surface  151 , IC board  64  and light-blocking plate  67  are arranged in this order, from the rear surface  41  toward the front surface  40 . In the up-down direction, the light-blocking plate  67 , IC board  64  and the locking surface  151  are arranged in this order toward the top. More specifically, uppermost portions of the light-blocking plate  67 , the IC board  64  and the locking surface  151  are arranged toward the top in the recited order in the upward direction  54 . 
     Further, as illustrated in  FIG. 14 , the first protrusion  43  has a dimension or width in the left-right direction (width W 3 ) that is greater than the width W 1  of the light-blocking plate  67  in the left-right direction. That is, the first protrusion  43  has a wider width (W 3 ) than the light-blocking plate  67  and protrudes from the upper surface  39  further upward relative to the light-blocking plate  67 . The first protrusion  43  is designed to protect the light-blocking plate  67  from external damages, such as impacts that may be impinged at the time of falling of the ink cartridge  30  onto the floor, for example. 
     Further, referring to  FIG. 8 , the light-blocking plate  67  is positioned frontward relative to a center of gravity G of the ink cartridges  30  in the front-rear direction, whereas the locking surface  151  is positioned rearward relative to the center of gravity G of the ink cartridges  30  in the front-rear direction. In other words, the light-blocking plate  67  is positioned closer to the front surface  40  than the center of gravity G is to the front surface  40  in the front-rear direction. The locking surface  151  is positioned closer to the rear surface  41  than the center of gravity G is to the rear surface  41  in the front-rear direction. 
     Referring to  FIG. 10  in which the ink cartridge  30  is in the attached posture or in the upright posture, the IC board  64  is positioned rearward relative to the ink supply port  71  of the ink supply potion  34  in the front-rear direction. Further, the IC board  64  is positioned rearward relative to the partitioning wall  50  defining the rear edge  75 R of the ink supply potion  34  in the front-rear direction. The contact surface  84  is also positioned rearward relative to the ink supply port  71  of the ink supply potion  34 . The IC board  64 , the contact surface  84  and the inclined surface  155  are aligned in the front-rear direction in this order from the front toward the rear. More specifically, referring to  FIGS. 9B and 13A to 13D , assume an imaginary plane X 2  passing through the left-right center of the IC board  64  and extending parallel to the front-rear direction and up-down direction. In the present embodiment, this imaginary plane X 2  also passes through centers of the contact surface  84 , the inclined surface  155  and the locking surface  151  in the left-right direction. Further, in the present embodiment, the imaginary plane X 2  also passes the left-right center of the ink supply port  71 . 
     Again, on the upper surface  39  between the IC board  64  and the inclined surface  155  in the front-rear direction, the upper edge of the inclined surface  155  (point P 1 ) is the uppermost position. The contact surface  84  is positioned slightly higher relative to the electrodes  65  on the IC board  64 , but is positioned lower than the upper edge (point P 1 ) of the inclined surface  155 . The contact surface  84  is positioned at the substantially same level as or slightly lower relative to the lower edge of the inclined surface  155 . 
     The ink supply potion  34 , the IC board  64  and the locking surface  151  are aligned in the front-rear direction in this order from the front toward the rear. More specifically, referring to  FIGS. 8 and 10 , the IC board  64  is arranged rearward relative to the ink supply potion  34  (ink supply port  71 ) in the front-rear direction. Further, the IC board  64  and contact surface  84  are aligned with each other in the front-rear direction. 
     The light-blocking plate  67  is positioned between the ink supply port  71  of the ink supply potion  34  and the IC board  64  in the front-rear direction. The light-blocking plate  67  is also positioned lower than the upper surface of the IC board  64 , i.e., the electrodes  65 . The front end  42 F of the bottom surface  42  is positioned frontward relative to the IC board  64 . 
       FIG. 10  summarizes positional relationships among the above-mentioned elements of the ink cartridge  30 . 
     A distance D 1  is larger than a distance D 2  (D 1 &gt;D 2 ). Here, the distance D 1  is defined as a distance in the front-rear direction between the ink supply port  71  (i.e., the front end face of the ink supply potion  34  in which the ink supply port  71  is open) and the engaging point P 3  on the locking surface  151 . The distance D 2  is defined as a distance in the front-rear direction between the engaging point P 3  on the locking surface  151  and the upper portion  41 U of the rear surface  41  (rearmost point P 5  on the rear surface  41 ). Further, the distance D 2  is shorter than a distance D 5  (D 2 &lt;D 5 ). The distance D 5  is defined as a distance in the front-rear direction between the contact point P 4  on the electrodes  65  of the IC board  64  and the engaging point P 3  on the locking surface  151 . The distance D 5  is greater than a distance D 6  (D 5 &gt;D 6 ). The distance D 6  is defined as a distance in the front-rear direction between the contact point P 4  on the electrodes  65  of the IC board  64  and the front-rear center of the contact surface  84 . 
     Further, a distance D 3  is longer than a distance D 4  (D 3 &gt;D 4 ). The distance D 3  is defined as a distance in the up-down direction between the vertical center of the ink supply port  71  and the upper edge  151 U of the locking surface  151 . The distance D 4  is defined as a distance in the up-down direction between the vertical center of the ink supply port  71  and the contact surface  84 . Still further, the distance D 4  is shorter than a distance D 7  (D 4 &lt;D 7 ), where the distance D 7  is defined as a distance in the up-down direction between the vertical center of the ink supply port  71  and the upper end  151 U of the inclined surface  155 . The contact point P 4  on the electrodes  65  is spaced away from the ink supply port  71  (front end face of the ink supply potion  34  in which the ink supply port  71  is open) by a distance D 8 . That is, the distance D 8  is defined as a distance in the front-rear direction between the ink supply port  71  (front end face of the ink supply potion  34  in which the ink supply port  71  is open) and the contact point P 4  on the electrodes  65  of the IC board  64 . 
     Preferably, the distance D 1  may range from 90 mm to 95 mm; the distance D 2  may range from 20 mm to 25 mm; the distance D 3  may range from 71 mm to 80 mm; the distance D 4  may range from 70 mm to 73 mm; the distance D 5  may range from 30 mm to 35 mm; and the distance D 6  may range from 10 mm to 13 mm. These numerals are just examples, and should not be limited thereto. 
     Note that, in the present embodiment, among the light-blocking plate  67 , the IC board  64  and the locking surface  151 , the light-blocking plate  67  is positioned closest to the front surface  40  (front surface of the front wall  40 ) that defines a frontmost edge of the ink cartridge  30 . That is, the light-blocking plate  67  is the element that is positioned closest to the frontmost edge of the ink cartridge  30  among those elements that are configured to be accessed from outside (i.e., among the light-blocking plate  67 , the IC board  64  and the locking surface  151 ). Accordingly, the distance D 2  between the rearmost point P 5  and the engaging point P 3  in the front-rear direction is shorter than a distance D 9  defined between the frontmost edge (front surface of the front wall  40 ) and the front edge of the light-blocking plate  67  (i.e., the interfering surface  67   b ) in the front-rear direction. 
     &lt;Comparison of the Ink Cartridges  30 C,  30 M,  30 Y and  30 K&gt; 
     &lt;Ink Cartridge  30 K&gt; 
     The ink cartridge  30 K is different from the ink cartridges  30 C,  30 M, and  30 Y in terms of ink color and capacity of the first ink chamber  32 . 
     The ink cartridge  30 K stores ink of a black color. The ink cartridge  30 K is different from the ink cartridges  30 C,  30 M, and  30 Y in that the cartridge body  31  of the ink cartridge  30 K has a left-right dimension that is larger than a left-right dimension of the cartridge body  31  of the ink cartridges  30 C,  30 M and  30 Y, as illustrated in  FIGS. 11A through 15 . Accordingly, the capacity of the first ink chamber  32  of the ink cartridge  30 K is larger than those of the ink cartridges  30 C,  30 M, and  30 Y. 
     Referring to  FIGS. 13A to 13D , the side surface  37  of the ink cartridge  30 K (labelled as  37 K in  FIG. 13A ) is positioned farther away from the imaginary plane X 2  than the side surface  37  of each of the ink cartridges  30 C,  30 M and  30 Y is from the imaginary plane X 2  in the rightward direction  55 . The left-right dimension of the ink cartridge  30 K is defined as a distance between outer edges of the cartridge body  31  of the ink cartridge  30 K in the left-right direction (i.e., the distance between the side surface  37 K and the side surface  38  of the cartridge body  31  of the ink cartridge  30 K). 
     Further, referring to  FIGS. 13A to 13D , the first protrusion  43  and second protrusion  83  for the ink cartridges  30 C,  30 M and  30 Y are disposed on the upper surface  39  at the left-right center thereof. On the other hand, on the upper surface  39  of the cartridge body  31  of the ink cartridge  30 K, the first protrusion  43  and second protrusion  83  are arranged offset from the left-right center of the upper surface  39  of the cartridge body  31 . More specifically, in the present embodiment, the first protrusion  43  and second protrusion  83  of the ink cartridge  30 K are disposed on the upper surface  39  at a position offset to the left relative to the left-right center of the upper surface  39  of the cartridge body  31 . On the other hand, the first protrusion  43  and second protrusion  83  for the ink cartridges  30 C,  30 M and  30 Y are disposed on the upper surface  39  at the left-right center thereof. 
     The ink cartridges  30 C,  30 M,  30 Y and  30 K are different from one another in terms of the left-right position of the light-blocking plate  67 . That is, specific positions of the respective light-blocking plates  67 C,  67 M,  67 Y and  67 K in the left-right direction differ from one another among the ink cartridges  30 C,  30 M,  30 Y and  30 K, as shown in  FIGS. 13A to 13D . 
     Referring to  FIGS. 13A and 14 , with regard to ink cartridge  30 K, the left-right position of the light-blocking plate  67 K does not fall within the width of the IC board  64  in left-right direction. That is, the light-blocking plate  67 K of the ink cartridge  30 K is not aligned with the IC board  64  (the second protrusion  83  and the first protrusion  43 ) in the front-rear direction. 
     More specifically, as illustrated in  FIG. 14 , in the ink cartridge  30 K, the width W 1  of the light-blocking plate  67 K is smaller than a width W 2  (W 1 &lt;W 2 ), where the width W 2  is a defined as a distance (dimension) in the left-right direction between the right edge of the upper surface  39  (right side surface  37 K) and the right edge of the interfering surface  67   b  (i.e., the right side surface  67   a  of the light-blocking plate  67 K) in the ink cartridge  30 K. Put another way, the width W 2  is a shortest distance in the left-right direction between one of the outer edges of the upper surface  39  (i.e., right edge of the upper surface  39 ) and one of the light-blocking surface  67   a  of the light-blocking plate  67 K (i.e., one of the outer edges of the interfering surface  67   b ) in the ink cartridge  30 K. Note that, in the ink cartridge  30 K, the right edge of the upper surface  39  (right side surface  37 K) is closer to the right side surface  67   a  of the light-blocking plate  67 K (right edge of the interfering surface  67   b ) than the left edge of the upper surface  39  (left side surface  38 ) is to the right side surface  67   a  of the light-blocking plate  67 K in the left-right direction. 
     Further, referring to  FIG. 14 , assume an imaginary plane X 3  that represents an outermost edge of the cartridge body  31  of the ink cartridge  30 M ( 30 C,  30 Y) in the left-right direction. That is, the imaginary plane X 3  corresponds to the side surface  37  of the ink cartridge  30 M ( 30 C,  30 Y) in the present embodiment. The light-blocking plate  67 K of the ink cartridge  30 K is positioned outward relative to the imaginary plane X 3  in the left-right direction, i.e., opposite to the imaginary plane X 2  with respect to the imaginary plane X 3 . Put another way, in the left-right direction, a distance L 1  is greater than a distance L 2  (L 1 &gt;L 2 ), where the distance L 1  is a distance between the side surface  67   a  (left side surface  67   a K) of the light-blocking plate  67 K and the imaginary plane X 2 ; and the distance L 2  is a shortest distance between the imaginary plane X 2  and the outermost edge of the cartridge body  31  of the ink cartridge  30 M ( 30 C,  30 Y) in the left-right direction (i.e., the distance in the left-right direction between the imaginary plane X 2  and the side surface  38  in the present embodiment). That is, in the ink cartridge  30 K, the interfering surface  67   b ( 67   b K) of the light-blocking plate  67 K is not aligned with the IC board  64  in the front-rear direction and is offset toward the right from the imaginary plane X 2 . Or the interfering surface  67   b ( 67   b K) of the light-blocking plate  67 K and the IC board  64  are arranged at different positions from each other in the left-right direction. 
     On the other hand, referring to  FIGS. 13B to 13D , the light-blocking plates  67 C,  67 M and  67 Y of the ink cartridges  30 C,  30 M,  30 Y are all arranged at such left-right positions that fall within a width of the IC board  64  (a width of the second protrusion  83  and the first protrusion  43 ) in the left-right direction. However, the specific positions of the light-blocking plates  67 C,  67 M and  67 Y differ from one another in the left-right direction. 
     More specifically, as illustrated in  FIGS. 13B and 15 , the light-blocking plate  67 M of the ink cartridge  30 M is positioned on the imaginary plane X 2  to extend therealong. The interfering surface  67   b M of the light-blocking plate  67 M intersects with the imaginary plane X 2 , in the present embodiment. As illustrated in  FIG. 13C , the light-blocking plate  67 C of the ink cartridge  30 C is positioned leftward relative to the imaginary plane X 2 . That is, the interfering surface  67   b C of the light-blocking plate  67 C is positioned offset to the left relative to the imaginary plane X 2 . Put different way, the interfering surface  67   b C of the ink cartridge  30 C is closer to the left edge of the upper surface  39  (left side surface  38 ) than the interfering surface  67   b M of the ink cartridge  30 M is to the left edge of the upper surface  39  (left side surface  38 ) in the left-right direction. As illustrated in  FIG. 13D , the light-blocking plate  67 Y of the ink cartridge  30 Y is positioned rightward relative to the imaginary plane X 2 . That is, the interfering surface  67   b Y of the light-blocking plate  67 Y is positioned offset to the right relative to the imaginary plane X 2 . In other words, the interfering surfaces  67   b C,  67   b Y of the light-blocking plate  67 C,  67 Y are positioned away from the imaginary plane X 2  in the left-right direction and offset from the center of the IC board  64  in the left-right direction. 
     [Attachment/Detachment of the Ink Cartridge  30  Relative to the Cartridge-Attachment Section  110 ] 
     Next, a process for attaching the ink cartridge  30  to the cartridge-attachment section  110  will be described with reference to  FIGS. 4, 5A, 5B, 16 and 17 . In  FIGS. 4, 5A, 5B, 16 and 17 , the ink cartridge  30 M is depicted as an example. 
     As illustrated in  FIG. 8 , in the ink cartridges  30  prior to attachment to the cartridge-attachment section  110 , the valve  77  closes the ink supply port  71  of the packing  76 . Accordingly, at this time, ink flow to the outside of the ink cartridge  30  is interrupted. Further, in this state, the valve  97  closes the air communication port  96 . Accordingly, the first ink chamber  32  is not opened to the atmosphere. Further, before attachment of the ink cartridge  30  to the cartridge-attachment section  110 , the opening  112  of the case  101  is closed by the cover  114  at the closing position. 
     For inserting and removing the ink cartridge  30  into/from the cartridge-attachment section  110 , the user pivots the cover  114  from the closing position to the opening position. 
     The ink cartridge  30  is configured to be inserted into the case  101  through the opening  112  of the cartridge-attachment section  110  in the upright posture: that is, in such a posture that the front surface  40  of the cartridge body  31  faces frontward, and the upper surface  39  of the cartridge body  31  face upward. Since the upper portion  41 U of the rear surface  41  of the cartridge body  31  is positioned rearward relative to the lower portion  41 L, that is, since the upper portion  41 U is positioned closer to the user than the lower portion  41 L is to the user, the user pushes the upper portion  41 U forward to insert the ink cartridge  30  into the cartridge-attachment section  110 . The bottom portion of the ink cartridge  30  thus enters the corresponding guide groove  109  provided in the bottom surface of the case  101 . 
     As the ink cartridge  30  is further inserted into the case  101 , the ink supply portion  34  enters the corresponding guide portion  105 . At the same time, the rod  125  enters into the corresponding air communication port  96 . 
     Further, the interfering surface  67   b  of the light-blocking plate  67  arrives at the corresponding gate  108  of the cartridge-attachment section  110 . For example, in case that the ink cartridge  30 M is inserted into the prescribed insertion space  111 M of the case  101 , the left-right position of the interfering surface  67   b M of the light-blocking plate  67 M is coincident with the left-right position of the slit  119 M of the gate  108 M. Accordingly, as the cartridge body  31  of the ink cartridge  30 M is moved in the forward direction  51  along the corresponding guide groove  109 , the interfering surface  67   b M passes through the slit  119 M without abutting against the opposing walls  118  of the gate  108 M, and moves past the gate  108 M to be positioned frontward of the gate  108 M, as depicted in  FIG. 16 . The locking surface  151  is positioned still rearward of the lock shaft  145 . 
     Here, as a comparative example, assume that the ink cartridge  30 C is inserted into the insertion space  111 M that does not correspond to the ink cartridge  30 C. In this case, since the left-right position of the interfering surface  67   b C does not coincide with the left-right position of the slit  119 M, the interfering surface  67   b C abuts against the opposing walls  118  of the gate  108 M as the cartridge body  31  of the ink cartridge  30 C is moved in the forward direction  51  along the guide groove  109 , as illustrated in  FIG. 18 . The interfering surface  67   b C of the ink cartridge  30 C therefore cannot pass through the slit  119 M. As a result, the ink cartridge  30 C cannot be inserted further forward in the frontward direction  51  from the state depicted in  FIG. 18 . Accordingly, the ink needle  102  does not separate the valve  77  of the ink cartridge  30 C from the packing  76 . That is, the ink supply port  71  is not yet opened by the ink needle  102  and thus the ink supply potion  34  is not connected to the ink needle  102 . Still alternatively, the ink needle  102  may be separated from the ink supply port  71  of the ink supply potion  34  in the front-rear direction when the interfering surface  67   b C abuts against the opposing walls  118  of the gate  108 M. In the present embodiment, “the ink supply potion  34  is connected to the ink needle  102 ” denotes a state where the ink needle  102  separates the valve  77  from the ink supply port  71  and the ink supply port  71  is opened. Thus, in  FIG. 18 , the ink supply potion  34  is not connected to the ink needle  102 , since the ink needle  102  is in contact with the packing  76  but the valve  77  still closes the ink supply port  71 . 
     In this way, the light-blocking plate  67  of the ink cartridge  30  can function as a physical key to see whether or not the ink cartridge  30  is inserted into a correct one of the insertion spaces  111  (designated insertion space  111 ) of the cartridge-attachment section  110 . 
     As the ink cartridge  30 M is inserted further in the frontward direction  51  after passing through the gate  108 M, the ink needle  102  passes through the ink supply port  71  to separate the valve  77  from the packing  76  against the biasing force of the coil spring  78 . As a result, the vertical position of the ink supply portion  34  is fixed relative to the cartridge-attachment section  110 . In this state, the ink cartridge  30 M as a whole is applied with the biasing force of the coil spring  78  of the ink supply potion  34  so that the ink cartridge  30 M is urged rearward. The rod  125  having entered into the air communication port  96  abuts against the valve  97  to separate the valve  97  from the air communication port  96  against the biasing force of the coil spring  98 . As a result, the first ink chamber  32  is opened to the atmosphere through the through-hole  46 , the air valve chamber  36 , and the air communication port  96 . 
     Further, the first protrusion  43  reaches the lock shaft  145 , and the inclined surface  155  is brought into contact with the lock shaft  145  and slidingly moves in the frontward direction  51  relative to the lock shaft  145 . 
     The ink cartridge  30 M is applied with biasing forces generated by the compressed coil springs  78  and  98  acting in the rearward direction  52 . The magnitude of the biasing force generated by each of the coil springs  78  and  98  is determined by a spring constant thereof and a distance thereof compressed from its natural length. The spring constant of the coil spring  98  is smaller than the spring constant of the coil spring  78 . The compressed distance of the coil spring  78  (a distance by which the valve  77  is separated from the ink supply port  71 ) is larger than the compressed distance of the coil spring  98  (a distance by which the valve  79  is separated from the air communication port  96 ). As a result, in a state where the ink cartridge  30 M is accommodated in the cartridge-attachment section  110 , the magnitude of the biasing force generated by the coil spring  78  is larger than the magnitude of the biasing force of the biasing force generated by the coil spring  98 . 
     The ink cartridge  30 M is also applied with a rotational moment acting in a counterclockwise direction in  FIG. 16 , since the user pushes the upper portion  41 U of the rear surface  41 . However, against this rotational moment, the contact between the inclined surface  155  and the lock shaft  145  causes the ink cartridge  30 M to pivot in a clockwise direction in  FIG. 17  about a center C of the ink supply port  71  of the packing  76  into which the ink needle  102  is inserted. That is, the center C of the ink supply port  71  serves as a pivot center of the ink cartridge  30  in the present embodiment. 
     Incidentally, the position of the pivot center of the ink cartridge  30  may vary depending on the shape of the ink needle  102  and the shape of the ink supply port  71 . In the present embodiment, indeed, as shown in  FIGS. 4 and 17 , the pivot center is a center of a portion PP at which the ink needle  102  and the inner peripheral surface of the tubular ink supply port  71  are in contact with each other. In the present embodiment, the pivot center is the center of the portion PP at which the ink needle  102  contact the inner peripheral surface of the packing  76  defining the ink supply port  71 . This portion PP at which the ink needle  102  and the ink supply port  71  (the inner peripheral surface of the packing  76 ) contact each other will be referred to as a particular portion PP hereinafter, whenever necessary. The ink cartridge  30  is thus inserted in the frontward direction  51  in a posture illustrated in  FIGS. 16 and 17 . The posture illustrated in  FIGS. 16 and 17  is referred to as a second posture, hereinafter. 
     Since the lower surface  42  of the cartridge body  31  is inclined relative to the front-rear direction (horizontal direction), a space is available between the lower surface  42  and the bottom surface of the guide groove  109 . This space allows the above-described pivotal movement of the ink cartridge  30 M in the clockwise direction. 
     Further, since the inner diameter of the air communication port  96  is larger than the outer diameter of the rod  125 , a space is also provided between the rod  125  and the air communication port  96 . This space also allows the pivotal movement of the ink cartridge  30  in the clockwise direction. In other words, in the state where the ink cartridge  30  is attached to the cartridge-attachment section  110 , the rod  125  and the air communication port  96  do not contact with each other. That is, vertical positioning is not performed between the rod  125  and the air communication port  96 . 
     In the second posture, a space is also provided between the electrodes  65  of the IC board  64  and the corresponding set of contacts  106  in the up-down direction. That is, the electrodes  65  and the contacts  106  are separated from each other in the up-down direction. Further, in the second posture as a result of the clockwise pivoting of the ink cartridge  30 M, the contact surface  84  is located below the corresponding positioning portion  107 . A space is therefore formed between the positioning portion  107  and the contact surface  84  in the up-down direction. That is, the positioning portion  107  and the abutment part  84  are separated from each other in the up-down direction. 
     As the ink cartridge  30 M is further inserted forward in the frontward direction  51  from the state illustrated in  FIG. 16  against the biasing force of the coil spring  78 , the inclined surface  155  and the horizontal surface  154  of the first protrusion  43  move frontward beyond the lock shaft  145 , reaching a position closer to the end wall of the case  101  than the lock shaft  145  is to the end wall, as illustrated in  FIG. 17 . In the ink cartridge  30 M in the second posture, the locking surface  151  is positioned lower relative to the lock shaft  145 . 
     As described above, the ink cartridge  30 M ( 30 ) is applied with the rotational moment acting in the counterclockwise direction in  FIG. 17  due to the user&#39;s forward pushing on the upper portion  41 U of the rear surface  41 . Also, the rotational moment acting in the clockwise direction in  FIG. 17  is also generated in the ink cartridge  30 M ( 30 ) by the biasing force of the coil spring  98  disposed in the air valve chamber  36 . In a state where the inclined surface  155  and the horizontal surface  154  no longer abut against the lock shaft  145 , the ink cartridge  30 M ( 30 ) is caused to pivot in the counterclockwise direction in  FIG. 17  about the pivot center C due to the user&#39;s pushing force against the biasing force of the coil spring  98 . The contact surface  84  is thereby brought into contact with the positioning portion  107  from below. 
     At this time, the locking surface  151  faces rearward and opposes the lock shaft  145  in the front-rear direction. When the user stops pushing the ink cartridge  30 M ( 30 ) in the frontward direction  51 , the ink cartridge  30 M ( 30 ) is moved rearward by the biasing force of the coil spring  78 . The locking surface  151  therefore moves rearward to abut against the lock shaft  145  from frontward thereof. This contact between the locking surface  151  and the lock shaft  145  restricts the ink cartridge  30  from moving further rearward in the rearward direction  52 . That is, positioning of the ink cartridge  30 M ( 30 ) in the front-rear direction relative to the cartridge-attachment section  110  is provided by the contact between the locking surface  151  and the lock shaft  145 . 
     Further, since the contact surface  84  abuts the positioning portion  107  from below at this time, the ink cartridges  30 M ( 30 ) is also restricted from moving upward. That is, the ink cartridge  30 M ( 30 ) is prevented from pivoting further in the counterclockwise direction about the center C. This abutment between the contact surface  84  and the positioning portion  107  thus provides positioning of the ink cartridge  30 M ( 30 ) in the up-down direction. As a result, the ink cartridge  30 M ( 30 ) is fixed in position in the corresponding insertion space  111 M ( 111 ) of the cartridge-attachment section  110 , as illustrated in  FIG. 4 . The posture of the ink cartridge  30 M ( 30 ) illustrated in  FIG. 4  (the attached posture) will also be referred to as a first posture, hereinafter, whenever necessary, for the sake of explanation. Thus, attachment of the ink cartridge  30 M ( 30 ) to the cartridge-attachment section  110  is completed. In other words, the ink cartridge  30  is pivotable about the center C of the ink supply port  71  to move between the first posture and the second posture. 
     In the embodiment, the “insertion of the ink cartridge  30 ” is deemed to be completed when the ink cartridge  30  is fixed in position relative to the cartridge-attachment section  110 , with the locking surface  151  engaged with the lock shaft  145 . That is, the “insertion of the ink cartridge  30 ” is not deemed to end simply because the ink needle  102  is inserted into the ink supply potion  34 . 
     In the first posture (attached posture), following forces act on the ink cartridge  30 . 
     That is, the ink cartridge  30  is applied with a force acting downward (i.e., in a direction moving from the first posture to the second posture) about the center C, due to: a self-weight of the ink cartridge  30 ; a biasing force that the IC board  64  receives from the contacts  106 ; and the rotational moment acting in the clockwise direction and generated by the coil spring  98  provided in the air valve chamber  36 . On the other hand, the ink cartridge  30  is also applied with a force acting upward (i.e., in a direction moving from the second posture to the first posture) about the center C due to the rotational moment acting in the counterclockwise direction, the rotational moment being generated by the coil spring  78  in the ink valve chamber  35  acting on the locking surface  151 . Since the contact surface  84  is in abutment with the positioning portion  107 , the contact surface  84  is in receipt of a component of the upward force acting on the ink cartridge  30 , thereby providing the positioning of the ink cartridge  30  in the up-down direction. 
     In the first posture, the lock shaft  145  is separated in the up-down direction from the surface  156  extending rearward from the lower edge  151 L of the locking surface  151 . That is, the lock shaft  145  does not contribute to any positioning of the ink cartridge  30  in the up-down direction. Thus, in the cartridge-attachment section  110 , the up-down positioning of the ink cartridge  30  is performed, not by the lock shaft  145  provided separately from the case  101 , but by the positioning portion  107  that is integrally formed with the case  101  and that is disposed closer to the set of contacts  106  than the lock shaft  145  is to the contacts  106 . 
     Referring to  FIG. 4 , assume an imaginary arc Q of a circle that is centered on the center C and that passes a center Z of the lock shaft  145  (see  FIG. 5A ). As illustrated in  FIG. 4 , in the ink cartridge  30 M ( 30 ) in the first posture, the upper edge  151 U of the locking surface  151  is positioned outside the imaginary arc Q, while the lower edge  151 L of the locking surface  151  is positioned inside the imaginary arc Q. The ink cartridge  30 M ( 30 ) in the first posture is fixed in position by the contact between the ink supply port  71  and the ink needle  102  and by the contact between the locking surface  151  and the lock shaft  145 . In this state, the ink cartridge  30 M ( 30 ) in the first posture is applied with the biasing force of the coil spring  78  acting in the rearward direction  52 . As a result, a moment acting forward and upward is generated in the ink cartridge  30 M ( 30 ). This moment corresponds to a magnitude of a force urging the ink cartridge  30 M ( 30 ) to pivot in the counterclockwise direction about the center C. 
     In the ink cartridge  30 M ( 30 ) in the first posture, the electrodes  65  of the IC board  64  electrically contact the corresponding contacts  106  while elastically deforming the contacts  106  upward. At this time, while the IC board  64  is urged downward by the elastically deformed contacts  106 , due to the above-described moment acting on the ink cartridge  30 M ( 30 ), the IC board  64  is kept elastically deforming the contacts  106 . 
     Further, in the process of the counterclockwise pivoting of the ink cartridge  30 M from the state illustrated in  FIG. 17 , the electrodes  65  of the IC board  64 , which are positioned rearward of the center C and forward of the locking surface  151 , are respectively brought into contact with the contacts  106  from below to be electrically connected thereto. That is, in the present embodiment, the direction in which the ink cartridge  30  moves during insertion and removal thereof (i.e., the front-rear direction) intersects with the direction in which the electrodes  65  of the IC board  64  and the contacts  106  contact and separate from each other (i.e., the up-down direction). Accordingly, the electrodes  65  of the IC board  64  are prevented from being moved in the front-rear direction relative to the contacts  106  while being in contact with the contacts  106 , thereby suppressing generation of foreign matters such as shavings of the electrodes  65 . 
     After attaching the ink cartridge  30  to the cartridge-attachment section  110 , the user pivots the cover  114  from the opening position to the closing position. When the cover  114  is at the closing position, the cover sensor  115  outputs a detection signal indicative of detection of the cover  114 . In response to receipt of the detection signal from the cover sensor  115 , the controller  117  determines whether or not the cutout  66  is provided in the light-blocking plate  67  of the attached ink cartridge  30 , depending on signals outputted from the optical sensor  113 . The controller  117  then determines the type of the attached ink cartridge  30 , such as an initial capacity of the ink cartridge  30  and a composition of the ink stored in the ink cartridge  30 , based on the presence/absence of the cutout  66 . The relationship between the presence/absence of the cutout  66  and the type of the ink cartridge  30  is prestored in the memory of the controller  117  as predetermined data. 
     Next, a process for removing the attached ink cartridge  30  from the cartridge-attachment section  110  will be described. 
     For removing the ink cartridge  30  from the cartridge-attachment section  110 , the user first pivots the cover  114  from the closing position to the opening position and presses the operation surface  92  of the ink cartridge  30  downward. In the first posture of the ink cartridge  30 , the operation surface  92  faces upward and rearward. Hence, when the user operates the operation surface  92 , a force acting downward and forward is applied the ink cartridge  30 . The locking surface  151  is separated from the lock shaft  145  by the force acting forward, and the ink cartridge  30  is pivoted in the clockwise direction in  FIG. 4  by the downward force. As a result, as illustrated in  FIG. 17 , the contact surface  84  is separated from the positioning portion  107 , and the electrodes  65  of the IC board  64  are separated from the respective contacts  106 . The locking surface  151  is also positioned downward of the lock shaft  145 . That is, the ink cartridge  30  is moved from the first posture to the second posture. When the IC board  64  and the locking surface  151  are separated from the contacts  106  and lock shaft  145 , respectively, in accordance with the change of the ink cartridge  30  from the first posture to the second posture, the ink cartridge  30  is moved rearward relative to the cartridge-attachment section  110  due to the biasing force of the coil spring  78 . The user can therefore hold the cartridge body  31  to remove the ink cartridge  30  out of the cartridge-attachment section  110 . While the ink cartridge  30  is withdrawn from the cartridge-attachment section  110 , the light-blocking plate  67  passes through the slit  119  of the corresponding gate  108 , and moves rearward past the gate  108 . 
     [Determination on the Type of Ink Cartridge  30  Attached to the Cartridge-Attachment Section  110 ] 
     Now, how to determine the type of the ink cartridge  30  attached to the cartridge-attachment section  110  will be described while referring to a flowchart of  FIG. 19 . 
     In the present embodiment, the controller  117  determines the type of the ink cartridges  30  mounted in the insertion space  111  based on output signals from the optical sensor  113 . As described above, the output signals from the optical sensor  113  vary depending on whether or not the cutout  66  is formed in the light-blocking plate  67  in the mounted ink cartridge  30 . 
     Specifically, referring to  FIG. 19 , the controller  117  first determines in S 11  whether or not the cover  114  is at the opening position. The controller  117  repeats the step S 11  (S 11 : NO) unless the controller  117  receives a high level signal from the cover sensor  115 . The controller  117  determines that the cover  114  is at the opening position (S 11 : Yes) upon receipt of the high level signal from the cover sensor  115 . The controller  117  then determines in S 12  whether or not the high level signal from the optical sensor  113  is changed to a low level signal. The signal outputted from the optical sensor  113  becomes low level at least once when the detection surface D of the light-blocking plate  67  of the ink cartridge  30  comes between the light-emitting portion and the light-receiving portion of the optical sensor  113  during insertion of the ink cartridges  30  into the cartridge-attachment section  110 . 
     That is, the change in signal from high level to low level at the optical sensor  113  means that the ink cartridge  30  is inserted into the designated insertion space  111  of the cartridge-attachment section  110 . For example, if the ink cartridge  30 M is inserted into the insertion space  111 C other than the designated insertion space  111 M, the optical sensor  113  of the insertion space  111 C does not output the low level signal since the optical sensor  113  of the insertion space  111 C cannot detect the detection surface D of the light-blocking plate  67 M of the ink cartridge  30 M that cannot passes through the slit  109 C of the gate  108 C, as illustrated in  FIG. 18 . 
     When the signal from the optical sensor  113  changes to low level (S 12 : YES), the controller  117  then sets a flag stored in the memory ON in S 13 . That is, the ON flag means that the ink cartridge  30  having the light-blocking plate  67  (detection surface D) has been inserted into the designated insertion space  111  of the cartridge-attachment section  110 . 
     In case that the signal from the optical sensor  113  does not change to low level but is maintained at high level (S 12 : NO), the controller  117  then advances to the step S 14 . The optical sensor  113  continues to issue the high level signal unless the detection surface D of the light-blocking plate  67  passes the optical sensor  113 , that is, in case that the ink cartridge  30  is not inserted into the designated insertion space  111  of the cartridge-attachment section  110 . Note that, here, even if the ink cartridge  30  without the light-blocking plate  67  (detection surface D) is inserted into the designated insertion space  111 , the optical sensor  113  continues to output the high level signal (S 12 : NO) since the light from the optical sensor  113  is not interrupted. The controller  117  therefore advances to the step S 14 . 
     The controller  117  then determines in S 14  whether or not the cover  114  is closed. Specifically, when the signal outputted from the cover sensor  115  changes to low level, the controller  117  determines that the cover  114  is at the closing position (S 14 : YES) and advances to the step S 15 . The controller  117  goes back to the step S 12  as long as the signal from the cover sensor  115  remains at high level and does not change to low level (S 14 : NO). 
     After the cover  114  is determined to be at the closing position in S 14 , the controller  117  determines in S 15  whether or not accessing to the IC board  64  through the contacts  106  can be made. In case that the controller  117  cannot access the IC board  64  (S 15 : NO), the controller  117  determines in S 21  that the ink cartridge  30  is not attached to the cartridge-attachment section  110 . In this case, the controller  117  may give a warning to the user to inform him that the ink cartridge  30  is not attached to the cartridge-attachment section  110 , for example, through a message such as “No Cartridge” on a display. 
     In case that the controller  117  can access the IC board  64  (S 15 : YES), the controller  117  determines in S 16  whether or not the flag stored in the memory is ON. When the flag is not ON (S 16 : NO), the controller  117  determines in S 20  that the ink cartridge  30  without the light-blocking plate  67  is attached. In this case, the controller  117  may give a warning to the user to inform him that the inserted ink cartridge is abnormal, for example, through a message such as “Unable to Detect Cartridge” on the display. The ink cartridge  30  may lose the light-blocking plate  67 , for example, due to some kind of damages impinged on the light-blocking plate  67 . 
     When the flag is ON (S 16 : YES), the controller  117  then determines in S 17  whether the signal outputted from the optical sensor  113  is high level or low level. In case that the signal from the optical sensor  113  is a high level signal (S 17 : High), the controller  117  determines in S 18  that the attached ink cartridge  30  belongs to a type A. That is, the ink cartridge  30  having the light-blocking plate  67  formed with the cutout  66  as shown in  FIGS. 6 to 8 , for example, belongs to the type A. The optical sensor  113  is configured to output the high level signal in case that the cutout  66  is formed in the light-blocking plate  67  of the attached ink cartridge  30 . The cartridge  30  of the type A may be a high-capacity cartridge whose initial capacity of ink is large, for example. In case that the controller  117  determines that the attached ink cartridge  30  belongs to the type A, the controller  117  may set an initial number of sheets that the printer  10  can print with the initial amount of ink stored in the ink cartridge  30  of the type A. Alternatively, the controller  117  may set a threshold value corresponding to the initial amount of ink stored in the ink cartridge  30  of the type A. The controller  117  may halt printing operations if the printer  10  has used an amount of ink larger than the threshold value, or may give a warning to the user to inform him that little amount of ink is left in the attached ink cartridge  30 . 
     In case that the signal outputted from the optical sensor  113  is a low level signal (S 17 : Low), the controller  117  determines in S 19  that the attached ink cartridge  30  belongs to a type B. That is, the ink cartridge  30  having the light-blocking plate  67  without the cutout  66  as shown in  FIG. 18 , for example, belongs to the type B. The optical sensor  113  is configured to output the low level signal in case that the cutout  66  is not formed in the light-blocking plate  67  of the attached ink cartridge  30 . The cartridge  30  of the type B may be a low-capacity cartridge whose initial capacity of ink is not large, or smaller than the initial capacity of ink of the ink cartridge  30  of the type A. In case that the controller  117  determines that the attached ink cartridge  30  belongs to the type B, the controller  117  may set an initial number of sheets that the printer  10  can print with the initial amount of ink stored in the ink cartridge  30  of the type B. Alternatively, the controller  117  may set a threshold value corresponding to the initial amount of ink stored in the ink cartridge  30  of the type B. The controller  117  may halt printing operations if the printer  10  has used an amount of ink larger than the threshold value, or may give a warning to the user to inform him that little amount of ink is left in the attached ink cartridge  30 . 
     Operational and Technical Advantages of the Embodiment 
     In the ink cartridge  30  according to the present embodiment, the IC board  64  is positioned downward relative to the imaginary plane X 1 . When the ink cartridge  30  is turned upside down and placed on a ground plane such as a floor surface or the ground surface, the imaginary plane X 1  corresponds to the ground plane. Accordingly, in an upside-down posture where the ink cartridge  30  is turned upside down, the points P 1  and P 2  are in contact with the ground plane. Meanwhile, the IC board  64  is positioned in the space defined between the ground plane and the upper surface  39 , whereby the IC board  64  and the imaginary plane X 1  have a distance to provide a gap therebetween. Because of the disposition of these members, the first protrusion  43  or the light-blocking plate  67  can firstly collide with the ground plane, instead of the IC board  64 . Accordingly, the IC board  64  disposed at the upper surface  39  is prevented from being broken. Further in the embodiment, the cutout  66 , the IC board  64 , and the contact surface  84 , and a part of the side surfaces  67   a , which are accessible from upward, leftward, or rightward of the ink cartridge  30 , are disposed in the region defined between the upper surface  39  and the imaginary plane X 1 . Therefore, the members accessible from the outside are protected from the impact caused by dropping the ink cartridge  30  onto the ground plane. 
     Further, the first protrusion  43  and the light-blocking plate  67  are arranged frontward and rearward of the IC board  64 , and the ink cartridge  30  does not need to provide a protrusion protruding upward relative to the IC board  64 . Accordingly, the IC board  64  can be easily attached to the cartridge body  31 . Further, the IC board  64  is positioned between the first protrusion  43  and the light-blocking plate  67  in the front-rear direction so that the IC board  64  is well protected by the first protrusion  43  and the light-blocking plate  67 . 
     The light-blocking plate  67  is positioned frontward relative to the center of gravity G, and the first protrusion  43  is positioned rearward relative to the center of gravity G. Accordingly, the cartridge body  31  can rotate in a rotating direction when the first protrusion  43  and the light-blocking plate  67  collide with the ground plane. Here, the rotating direction is determined by the colliding order of these members, i.e. the first protrusion  43  and the light-blocking plate  67 . That is, when the first protrusion  43  and the light-blocking plate  67  collide with the ground plane in this order, the housing  31  rotates clockwise when viewed from the left side. 
     The first protrusion  43  has the horizontal surface  154  positioned frontward relative to the locking surface  151 . Accordingly, the horizontal surface  154  is likely to collide with the ground surface of floor surface to thereby protect the locking surface  151  when the ink cartridge  30  falls onto the ground plane in the upside-down posture. 
     Further, the upper end portion of the operation portion  90  is separated from the upper surface  39  to the same degree as the first protrusion  43  protrudes from the upper surface  39  or the raised portion  39 A in the up-down direction. The upper end portion of the operation portion  90  is likely to collide with the ground plane together with the first protrusion  43 , and the impact caused by dropping the ink cartridge  30  is therefore dispersed to the first protrusion  43  and the operation portion  90 . Accordingly, the impact on the cartridge body  31  is dispersed effectively. 
     Further, the second protrusion  83  the raised portion  39 A is continuously connected to the light-blocking plate  67 , thereby reinforcing the light-blocking plate  67 . 
     &lt;Variations and Modifications&gt; 
     In the following, various modifications to the depicted embodiment will be described. Like parts and components will be designated with the same reference numerals as those of the depicted embodiment to avoid duplicating explanation. 
     1. First Modification 
     In the above-described embodiment, the interfering surface  67   b  constitutes the front surface of the light-blocking plate  67 . However, the interfering surface  67   b  and the light-blocking plate  67  need not necessarily be formed integrally. For example, as illustrated in  FIG. 20 , an ink cartridge  230  may include a protrusion  285  having an interfering surface  285   b , and a light-blocking plate  267  having a light-blocking surface  267   a  as the detection surface D. That is, the protrusion  285  (interfering surface  285   b ) and light-blocking plate  267  (light-blocking surface  267   a ) are provided independently of each other. As in the embodiment, the interfering surface  285   b  is arranged to be aligned with the light-blocking plate  267  in the front-rear direction. The protrusion  285  is positioned frontward of the light-blocking plate  267  in the front-rear direction. The light-blocking plate  267  is configured to block the light from the corresponding optical sensor  113  during insertion of the ink cartridge  230  and in the attached posture of the ink cartridge  230 . The light-blocking plate  267  shown in  FIG. 20  is not formed with a cutout. The point P 2  is positioned at the uppermost and foremost portion of the light-blocking plate  267 , i.e. the point P 2  is positioned frontward relative to the detection surface D. 
     Incidentally, in this configuration of the first modification, the protrusion  285  may be configured not to block light. That is, in case that the protrusion  285  and the light-blocking plate  267  are provided as separate members from each other, the protrusion  285  may or may not be made of a material capable of transmitting light therethrough (translucent resin, for example). 
     With this structure, by separating the interfering surface  285   b  from the light-blocking plate  267 , impact, which will be impinged on the interfering surface  285   b  at the time of wrong insertion of the ink cartridge  230 , is prevented from being directly transmitted to the light-blocking plate  267 . Further, in case that the protrusion  285  is capable of transmitting light, the protrusion  285  does not disturb detection of the light-blocking plate  267  by the corresponding optical sensor  113  during insertion of the ink cartridge  230  into the corresponding insertion space  111  of the cartridge-attachment section  110 . 
     2. Second Modification 
     Further,  FIGS. 21 and 22  depict an ink cartridge  330  according to a second modification to the embodiment. 
     The ink cartridge  330  includes a cartridge body  331  configured of an upper cover  331 U and a lower case  331 L. The cartridge body  331  includes a front surface  340 , a rear surface  341 , an upper surface  339 , a bottom surface  342 , side surfaces  337  and  338 , a sub-lower wall  348 , and a connecting wall  349  corresponding to the front surface  40 , the rear surface  41 , the upper surface  39 , the bottom surface  42 , the side surfaces  37  and  38 , the sub-lower wall  48 , and the connecting wall  49  of the ink cartridge  30  of the embodiment, respectively. In  FIG. 21 , the side wall  337  is not shown. The ink supply potion  34  is provided at the connecting wall  349 , as in the embodiment. 
     In a side view, as shown in  FIG. 21 , the ink cartridge  330  has the same configuration on the upper surface  339  as that on the upper surface  39  of the ink cartridge  30  of the embodiment. Note that the ink cartridge  330  shown in  FIG. 21  includes the light-blocking plate  67  without the cutout  66 . That is, a portion of the light-blocking plate  67  corresponding to the cutout  66  (a portion indicated by a circle in a broken line in  FIG. 21 ) now serves as the detection surface D. That is, the light from the optical sensor  113  is configured be incident on the detection surface D. 
     In the depicted embodiment, the coil spring  98  is disposed in the air valve chamber  36  to move the valve  97  to open and close the air communication port  96 . Accordingly, while the ink cartridge  30  is inserted into and attached to the cartridge-attachment section  110 , the ink cartridge  30  receives the urging force acting in the clockwise direction (by the coil spring  98 ) as well as the urging force acting in the counterclockwise direction (by the coil spring  78  of the ink supply potion  34 ). 
     In contrast, referring to  FIG. 22 , the ink cartridge  330  according to the second modification does not include the valve  97  and the coil spring  98 . That is, the ink cartridge  330  is configured to receive the urging force of the coil spring  78  of the ink supply potion  34  as an urging force acting in the rearward direction  52  during insertion and attachment of the ink cartridge  330  relative to the cartridge-attachment section  110 . 
     More specifically, once the ink needle  102  is inserted into the ink supply port  71  and connected to the ink supply potion  34 , since no downward rotational moment is applied to the ink cartridge  330 , the ink cartridge  330  is applied with the upward rotational moment about the center C (portion PP) by the urging force of the coil spring  78  acting in the counterclockwise direction, in addition to the user&#39;s forward pushing of an upper portion of the rear surface  341 . The ink cartridge  330  is therefore pivoted counterclockwise from the second posture to the first posture. As a result, as in the depicted embodiment, the electrodes  65  of the IC board  64  are brought into contact with the contacts  106  from below to be electrically connected thereto; and the contact surface  84  is brought into contact with the positioning portion  107  from below. As the user releases his fingers from the ink cartridge  330 , the ink cartridge  330  is moved in the rearward direction  52  due to the urging force of the coil spring  78 , causing the locking surface  151  to abut against the lock shaft  145  from its front side. The ink cartridge  330  is thus fixed in position in the front-rear direction. That is, the locking surface  151  receives the rearward moment applied from the coil spring  78 , thereby maintaining the ink cartridge  330  in the attached state (in the first posture or upright posture). 
     In the ink cartridge  330  of the second modification as well, the light-blocking plate  67  and the IC board  64  are arranged on the upper surface  39  constituting the cartridge body  31  such that the interfering surface  67   b  of the light-blocking plate  67  is disposed frontward and downward relative to the electrodes  65  of the IC board  64 . With this structure, the gate  108  corresponding to the interfering surface  67   b  is less likely to contact the electrodes  65  of the IC board  64  during the insertion of the ink cartridge  330  into the corresponding insertion space  111  of the cartridge-attachment section  110 . 
     Further, as in the ink cartridge  30  of the depicted embodiment, positioning of the ink cartridge  330  relative to the cartridge-attachment section  110  is provided: by the abutment of the locking surface  151  against the lock shaft  145  in the front-rear direction; and by the contact of the contact surface  84  with the positioning portion  107  in the up-down direction. With this simple structure of the second embodiment as well, stable positioning of the ink cartridge  330  relative to the cartridge-attachment section  110  can be realized. 
     Still further, as in the ink cartridge  30  of the depicted embodiment, in the attached state of the ink cartridge  330 , the rearward urging force of the coil spring  78  is stably received by the locking surface  151  that is in contact with the lock shaft  145 , thereby preventing the ink cartridge  330  from moving further in the rearward direction  52  and providing positioning of the ink cartridge  330  in the front-rear direction relative to the cartridge-attachment section  110 . Accordingly, the contact pressure between the electrodes  65  of the IC board  64  and the contacts  106  can be stably maintained. 
     Further, with this structure of the second modification, the same technical and operational advantages as those of the embodiment can be obtained. 
     3. Third Modification 
     In the depicted embodiment, the cartridge body  31  is configured of two different members, i.e., the upper cover  31 U and the lower case  31 L attached to each other. However, the cartridge body  31  may be formed as a single member, without including an upper cover and a lower case. 
       FIGS. 23A and 23B  illustrate an ink cartridge  43  according to a third modification to the embodiment. The ink cartridge  430  includes a cartridge body  431  of a rectangular parallelepiped shape. The cartridge body  431  includes a front wall  440 , a rear wall  441 , an upper wall  439 , a bottom wall  442  and side walls  437  and  438 . Each of these walls  440 ,  441 ,  439 ,  442 ,  437  and  438  constitute an outer shell of the ink cartridge  430 . In other words, the cartridge body  431  is not configured of a cover and a case. Thus, an upper surface of the upper wall  439  constitutes an upper surface of the cartridge body  431 . A front surface of the front wall  440  constitutes a front surface of the cartridge body  431 . The front surface of the front wall  440  (front surface of the cartridge body  431 ) is a flat surface, unlike the front surface ( 40 ,  49 ,  95 ) of the ink cartridge  30  of the embodiment. A rear surface of the rear wall  441  constitutes a rear surface of the cartridge body  431 . The rear surface of the rear wall  441  (rear surface of the cartridge body  431 ) is a flat surface, although the rear surface  41  of the ink cartridge  30  of the embodiment is configured of two portions (upper portion  41 U and lower portion  41 L). 
     An ink chamber  432  is defined inside the cartridge body  431 . More specifically, the ink chamber  432  is defined by inner surfaces of the front wall  440 , the rear wall  441 , the upper wall  439 , the bottom wall  442  and the side walls  437  and  438 . An upper end region in the ink chamber  432  (a region above an ink surface of ink stored in the ink chamber  432 ) is in communication with ambient air through an air communication port  496  formed in the upper wall  439 . Note that, the air communication port  496  may not necessarily be formed in the upper wall  439 , but may be formed in one of other walls constituting the cartridge body  431 . For example, the air communication port  496  may be formed in one of the side walls  437  and  438 . 
     An ink supply portion  434  is provided at the front wall  440 . In this modification, the ink supply potion  434  is a through-hole formed in a lower end portion of the front wall  440  to penetrate therethrough in the front-rear direction. The ink supply potion  434  defines an ink supply port  471  that is open frontward on the front surface of the front wall  440 . 
     On the upper surface  439 , a light-blocking plate  467 , an IC board  464 , a contact surface  484  and a first protrusion  443  having a locking surface  451  are arranged in the front-rear direction, as in the depicted embodiment. Specifically, the light-blocking plate  467 , the IC board  464 , the contact surface  484 , and the locking surface  451  are aligned with one another in the front-rear direction in this order from the front toward the rear. The light-blocking plate  467  is positioned frontward and downward relative to the IC board  64 . The front surface of the light-blocking plate  467  serves as an interfering surface  467   b . The light-blocking plate  467  has side surfaces including the detection surface D. The light-blocking plate  467  shown in  FIGS. 23A and 23B  is not formed with a cutout (i.e., the ink cartridge  430  shown in  FIGS. 23A and 23B  belongs to the type B). The contact surface  484  is arranged between the IC board  464  and the locking surface  451  in the front-rear direction. The contact surface  484  is positioned upward relative to the IC board  464  but downward relative to an upper edge (denoted as the point P 1 ) of the locking surface  451 . The upper edge (the point P 1 ) of the locking surface  451  is the highest (farthest away from the upper surface  439 ) among all parts disposed at the upper surface  439  between the light-blocking plate  467  and the locking surface  451  in the front-rear direction. That is, the upper edge (the point P 1 ) of the locking surface  451  constitutes an uppermost edge of the ink cartridge  430  between the light-blocking plate  467  and the locking surface  451 . The point P 2  is positioned at the uppermost and foremost portion of the light-blocking plate  467 , i.e. the point P 2  is positioned frontward relative to the detection surface D. The locking surface  451  is positioned closer to the rear wall  441  than to the IC board  464  in the front-rear direction. 
     h this structure, since the detection surface D (light-blocking surface) of the light-blocking plate  467  is positioned frontward and downward relative to the contact surface  484 , the positioning portion  107  of the printer  10 , which is configured to contact the contact surface  484 , is less likely to interfere with the light-blocking plate  467  (i.e., the interfering surface  467   b  and the detection surface D) during insertion of the ink cartridge  430  into the cartridge-attachment section  110 . Further, the lock shaft  145  of the cartridge-attachment section  110 , which is configured to engage the locking surface  451 , is less likely to interfere with the contact surface  484 , the detection surface D (interfering surface  467   b ), and the IC board  64  during the insertion of the ink cartridge  30  into the cartridge-attachment section  110 . 
     With this structure of the third modification, the same technical and operational advantages as those of the embodiment can be obtained. 
     4. Fourth Modification 
     In the above-depicted embodiment, the light-blocking plate  67  has a substantially rectangular shape when viewed from the left or right side. Alternatively, the light-blocking plate may have various shapes as in the fourth modification. 
     Further,  FIG. 24  depicts an ink cartridge  530  according to a fourth modification to the embodiment. The ink cartridge  530  includes a light-blocking plate  567 . The light-blocking plate  567  has side surfaces  567   a , a front surface  567   b , and an upper surface  567   c.    
     In the fourth modification, an ink cartridge  530  has a light-blocking plate  567  having a polygon shape when viewed from the left or right side. The dimension of the front surface  567   b  in the up-down direction is smaller than the height of the upper surface  567   c  from the upper surface  39 . That is, the light-blocking plate  567  has a plurality of stepped portion, and the highest surface of the light-blocking plate  567  is the upper surface  567   c.    
     The front edge of the upper surface  567   c , which is the highest portion (i.e. uppermost portion) of the light-blocking plate  567 , defines the point P 2 . The imaginary plane X 1  passes through the point P 1  and the point P 2 . The front end portion of the light-blocking plate  567  is positioned below the imaginary plane X 1 . 
     In the fourth modification, the IC board  64  is positioned downward relative to the imaginary plane X 1  and the IC board  64  is therefore protected from contacting the ground plane when the ink cartridge  530  falls onto the ground. Since the P 2  is closer to the raised portion  39 A than the front end portion of the light-blocking plate  567  is to the raised portion  39 A, the light-blocking plate  567  is effectively reinforced by the raised portion  39 A so that the light-blocking plate  567  can withstand the impact of the ground plane. The light-blocking plate  567  is durable against the impact caused by contacting the ground as compared to the configuration where the point P 2  is positioned at the front end portion of the light-blocking plate  567 . 
     5. Fifth Modification 
       FIG. 25  illustrated an ink cartridge  630  as a fifth modification to the embodiment. The ink cartridge  630  includes a light-blocking plate  667 . The light-blocking plate  667  has side surfaces  667   a , a front surface  667   b , and an upper surface  667   c . The upper surface  667   c  has a front part and a rear part positioned rearward of the front part. The front part of the upper surface  667   c  is inclined toward the upper surface in the front direction. That is, the front part of the upper surface  667   c  is inclined downward with respect to the front-rear direction in the upright posture to form an inclined surface that defines the point P 2 , and the point P 2  may be positioned frontward relative to the detection surface D. The imaginary plane X 1  passing through the point P 1 , point P 2 , and the front part of the upper surface  667   c . In the fifth modification, the IC board  64  is positioned downward relative to the imaginary plane X 1  and the IC board  64  is therefore protected from contacting the ground plane when the ink cartridge  630  falls onto the ground. 
     According to the above configuration, the upper surface  667   c  has the surface that can contact the ground plane. The impact can be dispersed along the front part of the upper surface  667   c  when the upper surface  667   c  is hit by the ground plane. Accordingly, the light-blocking plate  667  is durable against the impact caused by contacting the ground as compared to the configuration where only the points P 1  and P 2  can contact the ground plane. The ink cartridge  630  of the fifth embodiment effectively protects the IC board  64 . 
     6. Sixth Modification 
     In the embodiment, the light-blocking plate  67  contacts the upper surface  67 . Alternatively, the light-blocking plate  67  needs not necessarily contact the upper surface  39 . 
       FIG. 26  illustrates an ink cartridge  730  as a sixth modification to the embodiment. The ink cartridge  730  includes a light-blocking plate  767 . The light-blocking plate  767  has side surfaces  767   a , a front surface  767   b , and an upper surface  767   c . The  767  extends frontward from the front surface of the raised portion  39 A. The light-blocking plate  767  is separated upward from the upper surface  39 , and the bottom portion of the light-blocking plate  767  does not contact the upper surface  39 . The front end portion of the upper surface  767   c  and the uppermost and foremost portion of the front surface  767   b  define the point P 2  that the imaginary plane X 1  passes through. That is, the point P 2  is positioned frontward relative to the detection surface D. 
     In the sixth modification, the IC board  64  is positioned downward relative to the imaginary plane X 1  and the IC board  64  is therefore protected from contacting the ground plane when the ink cartridge  730  falls onto the ground. 
     7. Seventh Modification 
     In the embodiment, the light-blocking plate  67  contacts the upper surface  67 . Alternatively, the light-blocking plate  67  needs not necessarily contact the raised portion  39 A. 
       FIG. 27  illustrates an ink cartridge  830  as a seventh modification to the embodiment. The ink cartridge  830  includes a light-blocking plate  867 . The light-blocking plate  867  has side surfaces  867   a , a front surface  867   b , and an upper surface  867   c . The light-blocking plate  867  has a square shape when viewed from the left or right side, and the lower end portion of the light-blocking plate  867  contacts the upper surface  39 . The light-blocking plate  867  is separated frontward from the raised portion  39 A, and the bottom portion of the light-blocking plate  867  contacts the upper surface  39 . The front end portion of the upper surface  767   c  and the uppermost and foremost portion of the front surface  767   b  define the point P 2  that the imaginary plane X 1  passes through. That is, the point P 2  is positioned frontward relative to the detection surface D 
     The ink cartridge  830  further includes an operation portion  890  that has an operation surface  892 . The operation portion  890  or the operation surface  892  has the point P 1  at the front-upper end portion thereof. Specifically, the operation portion  890  protrudes higher than the first protrusion  43  to thereby define the point P 1 . The point P 1  is the uppermost and foremost portion of the operation portion  890 . The imaginary plane X 1  extending in the widthwise direction passes through points P 1  and P 2 , and the IC board  64  is positioned below the imaginary plane X 1 . 
     As depicted above, the point P 1  is not necessarily positioned at the first protrusion  43 . Since the imaginary plane X 1  is in coincidence with the ground plane, the point rearward of the IC board  64  that defines the highest imaginary plane X 1  can be the point P 1 . In other words, if the operation portion  890  is positioned lower than the first protrusion  43  in the attached posture, the first protrusion  43  may define the point P 1  as depicted in the embodiment and the above-described modifications. 
     In the seventh modification, the IC board  64  is positioned downward relative to the imaginary plane X 1  and the IC board  64  is therefore protected from contacting the ground plane when the ink cartridge  830  falls onto the ground. 
     8. Eighth Modification 
     In the embodiment, the light-blocking plate  67  has the point P 2 . Alternatively, another member may have the point P 2 . 
       FIG. 28  shows an ink cartridge  930  as an eighth modification to the embodiment. The ink cartridge  930  includes a protrusion  968  positioned frontward of the light-blocking plate  67 . The protrusion  968  and the light-blocking plate  67  overlap with each other when viewed from frontward, and the protrusion  968  has a width equal to or less than the width of the light-blocking plate  67 . The protrusion  968  protrudes upward from the upper surface  39  in the upright posture. The top of the protrusion  968  is higher than the upper portion of the  67  and defines the point P 2  that the imaginary plane X 1  passes through. That is, the uppermost and foremost portion of the protrusion  968  defines the point P 2 , i.e. the point P 2  is positioned frontward relative to the detection surface D. The imaginary plane X 1  also passes through the point P 1  positioned at the first protrusion  43 . 
     In the eighth modification, the IC board  64  is positioned downward relative to the imaginary plane X 1  and the IC board  64  is therefore protected from contacting the ground plane when the ink cartridge  930  falls onto the ground. Further, since the protrusion  968  can contact the ground plane when the ink cartridge  930  falls onto the ground, the light-blocking plate  67  is protected from being broken. 
     9. Other Variations 
     In the above-described embodiment, the light-blocking plate  67  is formed with the cutout  66 , and the cutout  66  needs not necessarily provided at the light-blocking plate  67 . The light-blocking plate  67  may be configured without a cutout. 
     In the above-described embodiment, the controller  117  is configured to determine the type of the ink cartridge  30  attached to the cartridge-attachment section  110  based on the presence/absence of the cutout  66  in the light-blocking plate  67 , during insertion of the ink cartridge  30  into the cartridge-attachment section  110  and at the time of completion of the attachment of the ink cartridge  30  to the cartridge-attachment section  110 . Alternatively, assuming that the cutout  66  is not formed in each light-blocking plate  67 , the controller  117  may be configured to determine whether or not the ink cartridge  30  is attached to the cartridge-attachment section  110  based on presence/absence of the light-blocking plate  67 . 
     Specifically, referring to a flowchart of  FIG. 29 , the controller  117  first determines in S 101  whether or not the cover  114  is closed. Specifically, when the signal outputted from the cover sensor  115  changes to low level, the controller  117  determines that the cover  114  is at the closing position (S 101 : YES) and advances to the step S 102 . The controller  117  repeats the step S 101  as long as the signal from the cover sensor  115  remains at high level and does not change to low level (S 101 : NO). 
     After the cover  114  is determined to be at the closing position in S 101 , the controller  117  determines in S 102  whether or not accessing to the IC board  64  through the contacts  106  can be made. For example, the controller  117  may determine whether or not the accessing to the IC board  64  is possible based on: whether or not a specific voltage can be applied to the IC board  64  (i.e., based on absence or presence of the IC board  64 ); or whether or not the controller  117  can get access to a memory of the IC board  64 . 
     In case that the controller  117  cannot access the IC board  64  (S 102 : NO), the controller  117  determines in S 106  that the ink cartridge  30  is not attached to the cartridge-attachment section  110 . In this case, the controller  117  may give a warning to the user to inform him that the ink cartridge  30  is not attached to the cartridge-attachment section  110 , for example, through a message such as “No Cartridge” on the display. 
     In case that the controller  117  can access the IC board  64  (S 102 : YES), the controller  117  determines in S 103  whether the signal outputted from the optical sensor  113  is high level or low level. In case that the signal from the optical sensor  113  is a high level signal (S 103 : High), the controller  117  determines in S 104  that an abnormal ink cartridge  30  is attached to the cartridge-attachment section  110 . The optical sensor  113  is configured to output the high level signal in case that the light-blocking plate  67  is not provided at the attached ink cartridge  30 . Thus, the controller  117  determines the attached ink cartridge  30  is abnormal. In case that the controller  117  determines that the attached ink cartridge  30  is abnormal, the controller  117  may give a warning to the user to inform him so, for example, through a message such as “Abnormal Cartridge Attached” on the display. 
     In case that the signal outputted from the optical sensor  113  is a low level signal (S 103 : Low), the controller  117  determines in S 105  that the ink cartridge  30  is correctly attached to the cartridge-attachment section  110 . Here, the optical sensor  113  is configured to output the low level signal, since the light-blocking plate  67  of the attached ink cartridge  30  blocks the light emitted from the optical sensor  113 . In other words, the controller  117  is configured to determine whether or not the ink cartridge  30  is attached to the cartridge-attachment section  110  by detecting the presence/absence of the light-blocking plate  67 . According to this variation, the ink cartridge  30  is determined to be attached to the cartridge-attachment section  110  in case that: the controller  117  can access the IC board  64 ; and the light-blocking plate  67  blocks or attenuates the light from the optical sensor  113 . 
     Still another variation is conceivable with regard to the determination performed by the controller  117 . 
     In the depicted embodiment, the controller  117  may determine whether or not the ink cartridge  30  is attached to the cartridge-attachment section  110  based on whether or not accessing to the IC board  64  is possible; and the controller  117  is configured to determine the type of the ink cartridge  30  attached to the cartridge-attachment section  110  based on the presence/absence of the cutout  66  in the light-blocking plate  67 . 
     However, the controller  117  may determine whether or not the ink cartridge  30  is attached to the cartridge-attachment section  110  based on presence or absence of the light-blocking plate  67 : and the controller  117  may further determine whether or not the attached ink cartridge  30  is abnormal based on whether or not accessing to the IC board  64  is possible. Assume in this case as well that the cutout  66  is not formed in each light-blocking plate  67 . 
     More specifically, referring to a flowchart of  FIG. 30 , the controller  117  first determines in S 201  whether or not the cover  114  is closed. Specifically, when the signal outputted from the cover sensor  115  changes to low level, the controller  117  determines that the cover  114  is at the closing position (S 201 : YES) and advances to the step S 202 . The controller  117  repeats the step S 201  as long as the signal from the cover sensor  115  remains at high level and does not change to low level (S 201 : NO). 
     After the cover  114  is determined to be at the closing position in S 201 , the controller  117  determines in S 202  whether the signal outputted from the optical sensor  113  is high level or low level. The optical sensor  113  is configured to output the high level signal in case that the light-blocking plate  67  is not provided at the attached ink cartridge  30  and thus the light from the optical sensor  113  is not blocked or attenuated by the light-blocking plate  67 . In case that the signal from the optical sensor  113  is a high level signal (S 202 : High), the controller  117  determines in S 206  that the ink cartridge  30  is not attached to the cartridge-attachment section  110 . In case that the controller  117  determines in S 206  that no ink cartridge  30  is attached, the controller  117  may give a warning to the user to inform him so, for example, through a message such as “No Cartridge” on the display. 
     In case that the signal from the optical sensor  113  is a low level signal (S 202 : Low), the controller  117  then determines in S 203  whether or not accessing to the IC board  64  can be made. For example, the controller  117  may determine whether or not the accessing to the IC board  64  is possible based on: whether or not a specific voltage can be applied to the IC board  64  (i.e., based on absence or presence of the IC board  64 ); or whether or not the controller  117  can get access to a memory of the IC board  64 . 
     In case that the controller  117  cannot access the IC board  64  (S 203 : NO), the controller  117  determines in S 204  that the attached ink cartridge  30  is abnormal. In case that the controller  117  determines that the attached ink cartridge  30  is abnormal, the controller  117  may give a warning to the user to inform him so, for example, through a message such as “Abnormal Cartridge Attached” on the display. 
     In case that the controller  117  can access the IC board  64  (S 203 : YES), the controller  117  determines in S 205  that the ink cartridge  30  is correctly attached to the cartridge-attachment section  110 . 
     Further, in the above-described embodiment, the ink cartridge  30  is pivotable about the center C of the ink supply port  71  to move between the first posture and the second posture. Alternatively, the pivot center may be positioned other than the ink supply port  71 . For example, the pivot center may be a prescribed position on a particular portion of an outer surface of the cylinder  75  that contacts the guide portion  105 . Alternatively, in case that a member may be provided at the cartridge-attachment section  110  so as to make contact with the sub-lower wall  48  of the attached ink cartridge  30 , the pivot center may be set to a position at which the member and the sub-lower wall  48  contact each other. In the embodiment, since the center C of the ink supply port  71  is defined as the pivot center, the ink needle  102  inserted in the ink supply port  71  is less likely to come off the packing  76  during pivotal movement of the ink cartridge  30  between the first posture and the second posture, thereby suppressing leakage of ink. 
     Still alternatively, the ink cartridge  30  may be configured to slide in the up-down direction to move between the first posture and the second posture. 
     Further, instead of the cartridge body  31  configured of the upper cover  31 U and the lower case  31 L, the cartridge body may have a nesting structure configured of two separate members: an inner case and an outer case that houses the inner case therein. In this case, the inner case defines an ink chamber therein, and the outer case constitutes an outer shell of the cartridge body  31 . 
     Further, in the depicted embodiment, the light-blocking plate  67  is connected to the raised portion  39 A constituting the upper surface  39  of the ink cartridge  30 . However, the upper surface  39  does not necessarily include the raised portion  39 A, but may be a flat plane, as in the third modification shown in  FIGS. 23A and 23B . Further, even if the upper surface  39  includes the rear portion  39 A (i.e., the upper surface  39  has a stepped structure as in the embodiment), the light-blocking plate  67  is not necessarily connected to the rear portion  39 A. 
     Further, in the above-described embodiment, four kinds of the ink cartridges  30 C,  30 M,  30 Y and  30 K adapted to be inserted into the designated insertion spaces  111 C,  111 M,  111 Y and  111 K, respectively, are provided as a set. However, more than four kinds of ink cartridges  30  may be provided as one set of the printing-fluid cartridges. 
     Note that the rearmost point P 5  of the ink cartridge  30  may not be defined on the rear surface  41  of the cartridge body  31 . The rearmost point P 5  may be defined on the operation portion  90 , in case that the operation portion  90  has a portion that protrudes further rearward relative to the rear surface  41  constituting the cartridge body  31  of the ink cartridge  30 . 
     Further, in the above-described embodiment, the coil spring  78  of the ink supply portion  34  functions to urge the ink cartridge  30  attached to the cartridge-attachment section  110  rearward. However, a different structure from the depicted configuration may be employed for urging the ink cartridge  30  attached to the cartridge-attachment section  110  rearward. 
     For example, a spring for biasing the ink cartridge  30  rearward may be provided at a position other than the ink supply portion  34 . A spring may be provided at the front surface  40  of the cartridge body  31  to extend frontward therefrom for urging the ink cartridges  30  rearward. Alternatively, a spring may be disposed at the end wall of the case  101  to extend rearward therefrom to urge the ink cartridge  30  attached to the cartridge-attachment section  110  in the rearward direction  52 . 
     In the depicted embodiment, the coil spring  98  is disposed within the air valve chamber  36  to move the valve  97  to open and close the air communication port  96 . This coil spring  98  also serves to urge the ink cartridge  30  rearward in the depicted embodiment. However, a coil spring different from the coil spring  98  may be provided solely for urging the ink cartridge  30  in the rearward direction  52 . For example, assuming that the air communication port  96  is formed in the connecting wall  95  or in an outer wall other than the front wall  40 , a coil spring may be disposed at the connecting wall  95  or somewhere in an inner space defined in the upper cover  31 U such that the coil spring does not serves to open the first ink chamber  32  to the atmosphere. 
     Further, while ink serves as an example of the printing fluid in the depicted embodiment, the printing fluid of the present disclosure is not limited to ink. For example, a pretreatment liquid that is ejected onto sheets prior to ink during a printing operation may be stored in the printing-fluid cartridge. Alternatively, cleaning water for cleaning the recoding head  21  may be stored in the printing-fluid cartridge. Still further, powder-like material having fluidity, such as toner, may be used as the printing fluid. 
     The first ink chamber  32 , the second ink chamber  33 , and the ink chamber  432  are examples of a storage chamber. The ink supply potion  34 ,  434  is an example of a supply portion. The front surface  40 ,  340 ,  440 , and the connecting wall  49  are examples of a front surface. The IC board  64 ,  464  and the electrodes  65 ,  465  are examples of an electrical interface. The light-blocking plate  67 ,  267 ,  467 ,  567 ,  667 ,  767 ,  867  and the protrusion  285 ,  968  are examples of one protrusion. The light-blocking surface  67   a ,  267   a ,  567   a ,  667   a ,  767   a ,  867   a  is an example of a detection surface. The first protrusion  43  and the operation portion  90 ,  890  are examples of another protrusion. The point P 1  is an example of another specific portion. The point P 2  is an example of one specific portion. The horizontal surface  154  is an example of an abutting surface. The upper surface  67   c ,  567   c ,  667   c ,  767   c ,  867   c  is an example of a top surface. The ink supply port  71 ,  471  is an example of a supply hole. The coil spring  98 ,  298  is an example of an urging member. The imaginary plane X 1  is an example of a specific imaginary plane.