Patent Publication Number: US-8991989-B2

Title: Ink cartridge and recording apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This is a continuation application of U.S. application Ser. No. 13/072,728, filed Mar. 27, 2011, which claims priority from Japanese Patent Application No. 2010-137810 filed Jun. 17, 2010. The entire contents of the above noted applications are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to an ink cartridge loadable on an image forming device provided with a biasing member for biasing the ink cartridge in a predetermined direction opposite to an installation direction defined as a direction in which the ink cartridge moves during an installation process. 
     BACKGROUND 
     An image forming device that forms an inked image on a sheet is known. Such the image forming device includes a recording head having nozzles through each of which an ink droplet is selectively ejected onto the sheet. The ink droplets adhered on the sheet forms a desired image. The image forming device has a cartridge installation portion, and uses an ink cartridge storing therein an ink to be supplied into the recording head. The ink cartridge is installable in and removable from the cartridge installation portion. 
     When the ink cartridge is removed from the cartridge loading portion since the ink in the ink cartridge runs down, the ink in the ink cartridge or an ink in an ink needle drops on an inner perimeter of the cartridge installation portion. Then a new ink cartridge is installed in the cartridge installation portion. The ink is then adhered to an outer perimeter of the new ink cartridge that is installed in the cartridge installation portion. The cartridge installation portion has a locking mechanism for positioning the ink cartridge and for retaining the ink cartridge in an installed state in the cartridge installation portion. Further, a biasing member is provided to bias the ink cartridge, which has been installed in the cartridge installation portion and engaged with the locking mechanism, in a removal direction in which the ink cartridge is removed from the cartridge installation portion. For removing the ink cartridge from the cartridge installation portion, the locking mechanism is operated to release (unlock) the ink cartridge, such that the ink cartridge is moved toward an opening of the cartridge installation portion by a biasing force of the biasing member. Thus, the ink cartridge is easily removed from the cartridge installation portion. 
     Further, when the ink cartridge is released, the ink cartridge could move vigorously, and the ink cartridge may be thrown out of the cartridge installation portion through the opening of the cartridge installation portion. As a result, the ink cartridge is thrown away (popped up) from the cartridge installation portion and impacts on the floor, thereby imparting impact on the ink cartridge to splash the ink out of the ink cartridge. Further, when the ink cartridge impacts onto a floor, the ink cartridge may be damaged. In order to avoid such accidental pop-up, a pop-up restraint mechanism is proposed in Laid-out Japanese Patent Application Publication No. 2005-288866. 
     According to the disclosed pop-up restraint (locking) mechanism, a resiliently deformable hooking pawl is provided at a cartridge installation portion, and an ink cartridge is formed with an engagement recess to be engageable with the pawl to avoid the pop-up when the ink cartridge is released from the biasing force of the biasing member. 
     SUMMARY 
     When a user replaces the ink cartridge repeatedly, for example, due to mis-installation of the ink cartridge, the hooking pawl may be plastically deformed. Therefore, the resiliency of the pawl may be impaired, or the pawl may be broken. As a result, the ink cartridge cannot be prevented from being popped up from the cartridge installation portion. In this case, the cartridge installation portion including the pawl must be replaced by a new cartridge installation portion. Incidentally, the replacement is also required in case of breakdown or mechanical fatigue of the locking mechanism. Thus, the user has to buy a new image forming device due to decline in function of the pawl and the locking mechanism. 
     It is, therefore, an object of the present invention to provide an ink cartridge capable of easily retaining a fully installed state of an ink cartridge in a cartridge installation portion. 
     In order to attain the above and other objects, the present invention provides an ink cartridge including a body, a particular interface and an engagement portion. The body has a front side at which an ink supply portion is located for supplying ink stored in an ink chamber to an exterior of the ink chamber, and a rear side located to face the front side. The particular interface is positioned substantially adjacent to the ink supply portion at the front side, wherein the particular interface is configured to be biased by a biasing member in a specific direction. The engagement portion is configured to be engaged with a locking section of a cartridge installation portion for retaining the body in an installed state. 
     According to another aspect of the present invention, there is provided a recording apparatus including a cartridge installation portion and a pressing mechanism. In the cartridge installation portion, an ink cartridge is installable. The ink cartridge includes: a body having a front side at which an ink supply portion is located for supplying ink stored in an ink chamber to an exterior of the ink chamber, and a rear side located to face the front side, the body having an upper surface extending from the front side to the rear side; a particular interface positioned substantially adjacent to the ink supply portion at the front side, wherein the particular interface is configured to be biased by a biasing member in a specific direction; and an engagement portion configured to be engaged with a locking section of a cartridge installation portion for retaining the body in an installed state. The pressing mechanism is provided at an upper portion of the cartridge installation portion and includes a biasing member and a lever portion. The biasing member is configured to bias the lever portion, and the lever portion is configured to press the upper surface of the ink cartridge downward such that the engagement portion frictionally engages the locking section. 
     According to still another aspect of the present invention, there is provided an ink cartridge to be loaded on and unloaded from a cartridge loading portion provided with a biasing member that biases the ink cartridge loaded in the cartridge loading portion in an unloading direction opposite to a loading direction. The ink cartridge includes a cartridge body, an ink supply portion, a protrusion and a first holding portion. The cartridge body has a front wall which is a leading side in the loading direction and a rear wall which is a trailing side in the loading direction, the cartridge body defining therein an ink chamber in which an ink is accommodated. The ink supply portion is positioned at a lower portion of the front wall for supplying the ink in the ink chamber to an outside. The protrusion protrudes from the front wall in the loading direction and positioned lower than the ink supply portion, the protrusion having a tip end abuttable on the biasing member to be biased in the unloading direction. The first holding portion retains the cartridge body at a predetermined position against a biasing force of the biasing member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a schematic cross-sectional view schematically illustrating an internal structure of a printer, including an ink supply device, according to an embodiment of the present invention; 
         FIG. 2  is a perspective view illustrating an external configuration of an ink cartridge according to a first embodiment of the invention; 
         FIG. 3  is a vertical cross-sectional view illustrating an internal configuration of the ink cartridge according to the first embodiment of the invention; 
         FIG. 4  is vertical cross-sectional view illustrating an internal configuration of a cartridge installation portion according to the first embodiment of the invention; 
         FIG. 5  is a perspective view illustrating an external configuration of the cartridge installation portion according to the first embodiment; 
         FIG. 6  is a vertical cross-sectional view illustrating the internal configurations of the ink cartridge and the cartridge installation portion according to the first embodiment, and illustrating a fully installed state of the ink cartridge into the cartridge installation portion; 
         FIG. 7  is a vertical cross-sectional view illustrating the internal configurations of the ink cartridge and the cartridge loading portion according to the first embodiment, and illustrating an initial installing state of the ink cartridge into the cartridge installation portion; 
         FIG. 8  is a vertical cross-sectional view illustrating the internal configurations of the ink cartridge and the cartridge installation portion according to the first embodiment, and illustrating an installing state of the ink cartridge into the cartridge installation portion after the state of  FIG. 7 ; 
         FIG. 9  is a vertical cross-sectional view illustrating an ink cartridge according to a second embodiment of the present invention, and illustrating an installed state of the ink cartridge into the cartridge installation portion; 
         FIG. 10  is a vertical cross-sectional view illustrating an ink cartridge according to a third embodiment of the present invention, and illustrating an installed state of the ink cartridge into the cartridge installation portion; 
         FIG. 11  is a vertical cross-sectional view illustrating an ink cartridge according to a fourth embodiment of the present invention and the cartridge installation portion, and illustrating a fully installed state of the ink cartridge into the cartridge installation portion; 
         FIG. 12  is a vertical cross-sectional view illustrating the ink cartridge according to the fourth embodiment and the cartridge installation portion, and illustrating a half-installed state of the ink cartridge into the cartridge installation portion; 
         FIG. 13  is an enlarged horizontal cross-sectional view illustrating an engagement between an ink cartridge according to a fifth embodiment of the present invention and the cartridge installation portion; 
         FIG. 14  is a vertical cross-sectional view illustrating an ink cartridge according to a sixth embodiment of the present invention and the cartridge installation portion, and illustrating an installed state of the ink cartridge into the cartridge installation portion; 
         FIG. 15  is a vertical cross-sectional view illustrating an ink cartridge according to a seventh embodiment of the present invention and the cartridge installation portion, and illustrating an installed state of the ink cartridge into the cartridge installation portion; and 
         FIG. 16  is a vertical cross-sectional view illustrating the ink cartridge according to the first embodiment and a cartridge installation portion according to a fourth modification of the present invention (different from that of  FIGS. 2 through 15 ), and illustrating an installed state of the ink cartridge into the cartridge installation portion. 
     
    
    
     DETAILED DESCRIPTION 
     An ink cartridge  30  according to a first embodiment of the present invention will be described with reference to  FIGS. 1 through 8 . 
     First, a printer  10  in which the ink cartridge  30  is accommodated will be described with reference to  FIG. 1 . The terms “upward”, “downward”, “upper”, “lower”, “above”, “below”, “beneath”, “right”, “left”, “front”, “rear” and the like will be used throughout the description assuming that the printer  10  is disposed in an orientation in which it is intended to be used. 
     The printer  10  is configured to form an image by ejecting ink droplets onto a sheet in accordance with an ink jet recording system. As shown in  FIG. 1 , the printer  10  includes an ink supply device  100  provided with a cartridge installation portion  110  in which the ink cartridge  30  detachably installable. The cartridge installation portion  110  has one side formed with an opening  112  exposed to an atmosphere. The ink cartridge  30  is detachably installable in the cartridge installation portion  110  through the opening  112 . That is, the ink cartridge  30  can be inserted into the cartridge installation portion  110 , and removed therefrom through the opening  112 . The opening  112  is normally covered by a cover member (not shown) provided at a frame of the printer  10 . The cover is opened for installation of the ink cartridge  30 . 
     The ink cartridge  30  stores therein an ink to be used in the printer  10 . The printer  10  includes a recording head  21  connected to the ink cartridge  30  via an ink tube  20  when the ink cartridge  30  is installed in the cartridge installation portion  110 . The recording head  21  has a sub tank  28  in which the ink supplied through the ink tube  20  is temporarily stored. The recording head  21  also includes a plurality of nozzles  29  through which ink supplied from the sub tank  28  is selectively ejected in accordance with a recording image. 
     The printer  10  also includes a sheet supply tray  15 , a sheet supply roller  23 , a sheet passage  24 , a pair of transfer rollers  25 , a platen  26 , a pair of discharge rollers  22 , and a discharge tray  16  arranged in this order in a sheet feeding direction. The sheet supplied from the sheet supply tray  15  to the sheet passage  24  by the sheet supply roller  23  is conveyed to the platen  26  by the pair of transfer rollers  25 . Then, the ink is selectively ejected from the recording head  21  onto the sheet passing through the platen  26  to form an image on the sheet. The sheet is then discharged onto the discharge tray  16  by the pair of discharge rollers  22 . 
     Next, the ink cartridge  30  will be described. As shown in  FIGS. 2 and 3 , the ink cartridge  30  defines therein an ink chamber  36  in which the ink is stored. The ink cartridge  30  has e.g., a cartridge body  31  defining an outer perimeter of the ink cartridge  30 . The ink chamber  36  may be defined inside the cartridge body  31 , or may be defined by a member separate from the cartridge body  31  but inside the cartridge body  31 . 
     The cartridge body  31  has a generally flat rectangular shape having small width (in a direction indicated by an arrow  51  which will be referred to as a widthwise direction or a horizontal direction), height (in a direction indicated by an arrow  52  which will be referred to as a vertical direction that is perpendicular to the widthwise direction) and depth (in a direction indicated by an arrow  53  which will be referred to as a depthwise direction that is perpendicular to the vertical direction and the widthwise direction) those greater than the width. 
     The ink cartridge  30  is installed in or removed from the cartridge installation portion  110  with respect to two directions  50  indicated by a two-way arrow  50  shown in  FIG. 2  which are parallel to the depthwise direction  53 . More specifically, as show in  FIG. 3 , the ink cartridge  30  is installed in the cartridge installation portion  110  in an insertion direction  56  and removed from the cartridge installation portion  110  in a removal direction  55  while retaining an upstanding state shown in  FIGS. 2 and 3 . 
     The cartridge body  31  has a front wall  40 , a rear wall  42 , a pair of side walls  83 ,  84 , a top wall  39 , and a bottom wall  41 . The front wall  40  and the rear wall  42  are located on a leading side and on a trailing side, respectively, when installing the ink cartridge  30  into the cartridge installation portion  110 , and are spaced away from each other in the depthwise direction  53 . The pair of side walls  83 ,  84  extends in the depthwise direction  53  and are connected to the front wall  40  and the rear wall  42 . The top wall  39  extends in the depthwise direction  53  for connecting upper ends of the front wall  40 , rear wall  42 , and the pair of side walls  83 ,  84 . The bottom wall  41  extends in the depthwise direction  53  for connecting lower ends of the front wall  40 , rear wall  42 , and the pair of side walls  83 ,  84 . 
     A detection portion  33  protrudes frontward (in the depthwise direction  53 ) from the front wall  40  at an approximately intermediate position in the vertical direction  52 . Further, a protrusion  46  also protrudes frontward from a lower end portion of the front wall  40 . The protrusion  46  protrudes farther forward than the detection portion  33  in the depthwise direction  53 . That is, the detecting portion  33  has a protruding length smaller than that of the protrusion  46 . The detection portion  33  has a box shape with an opening for allowing the detection portion  33  to be in fluid communication with an interior of the ink chamber  36 . Further, the detection portion  33  has a pair of side walls (left and right walls) made from a translucent resin material and connected to the front wall  40 . The side walls allow light emitted from an optical sensor  114  ( FIG. 4 ) to pass therethrough. Each side wall extends in the vertical direction  52  or can be slanted relative to the vertical direction  52 . The optical sensor  114  is provided at the cartridge installation portion  110 . 
     As shown in  FIG. 3 , the detection portion  33  provides therein a hollow box space. A sensor arm  60  is movably provided in the ink chamber  36 . The sensor arm  60  includes an arm body  61  and a shaft  64 . The arm body  61  is plate shaped, and is pivotally movably supported to the shaft  64 . The shaft  64  extends in the widthwise direction  51  and supported by a wall (not shown) extending from the interior of the ink cartridge  30 . The arm body  61  includes an indicator  62  and a float  63 , respectively positioned at opposite ends of the arm body  61 . The indicator  62  is movably positioned in the hollow box space of the detection portion  33 , i.e., between the pair of left and right walls of the detection portion  33  in the widthwise direction  51 . With this structure, the sensor arm  60  is adapted to shift its pivoting posture in accordance with an amount of the ink in the ink chamber  36  between a lower position as shown by a solid line in  FIG. 3  in which the indicator  62  approaches a lower wall of the detection portion  33  and an upper position as shown by a broken line in  FIG. 3  in which the indicator  62  approaches an upper wall of the detection portion  33 . 
     In the installed state of the ink cartridge  30  into the cartridge installation portion  110 , the detection portion  33  is changeable between a light-transmissive state and a non-light-transmissive state. In the light-transmissive state, not less than a predetermined amount of infrared light can be transmitted through the detection portion  33 , and in the non-light-transmissive state, less than the predetermined amount of infrared light is transmitted therethrough (the light is blocked, deflected or attenuated, or the light may be shut off, attenuated by a prism or reflected by a mirror to alter a path of the light). More specifically, the light-transmissive state and non-light-transmissive state are provided when the indicator  62  is at its upper position and lower position, respectively. In accordance with the light transmission state at the detection portion  33 , whether the amount of ink in the ink chamber  36  is less than a predetermined amount of ink can be detected. 
     As described later, the optical sensor  114  includes a light emitting element  118  and a light receiving element  119  in opposition to each other in the widthwise direction  51  ( FIG. 5 ). Light emitted from the light-emitting element  118  is received by the light receiving element  119 . The sensor arm  60  may not be provided within the detection portion  33 . The interior of the detection portion  33  is in fluid communication with the interior of the ink chamber  36  as described above. Therefore, infrared light emitted from the light emitting element  118  will be blocked, deflected or attenuated if ink is in the detection portion  33 , while the infrared light will be transmitted through the detection portion  33  if ink is absent or insufficient in the detection portion  33 . Alternatively, the infrared light emitted from the light emitting element  118  can be reflected to avoid incidence into the light receiving element  119  if ink is in the detection portion  33 , and the infrared light emitted from the light emitting element  118  can be reflected to be falling on the light receiving element  119  if ink is absent or insufficient in the detection portion  33 . 
     As shown in  FIGS. 2 and 3 , a through-hole  34  is formed in the front wall  40  at a position above the detection portion  33 . Further, a segment  32  formed with an air communication passage  32   a  in alignment with the through-hole  34  is provided at a rear surface of the front wall  40  for permitting an air layer in the ink chamber  36  to be communicated with the atmosphere. The air communication passage  32   a  is sealed with a film (not shown) in an unused state before installation of a new ink cartridge  30  into the cartridge installation portion  110 , for example, prior to shipment. Therefore, if the ink chamber  36  is decompressed, the decompression can be maintained. Upon installing the ink cartridge  30  into the cartridge installation portion  110 , a rod  124  (described later) provided at the cartridge installation portion  110  breaks the sealing film to open the air communication passage  32   a , so that the ink chamber  36  becomes atmospheric pressure. 
     The air communication passage  32   a  can be communicated with or shut off from the atmosphere by a valve (not shown). Upon opening the valve, negative pressure in the ink chamber  36  becomes the atmospheric pressure. Incidentally, the air communication passage  32   a  can be positioned at a position other than the front wall  40  as long as the interior of the ink chamber  36  is communicated with the atmosphere. In particular, adhesion of ink to a circuit substrate of the optical sensor  114  can be avoided if the air communication passage  32   a  is positioned lower than the detection portion  33  or positioned at the rear wall  42 . Further, the air communication passage  32   a  is not necessarily required if the ink cartridge  30  is used with maintaining negative pressure. 
     As shown in  FIGS. 2 and 3 , an ink supply portion  37  is provided at the front wall  40  at a position below the detection portion  33 . More specifically, the ink supply portion  37  is positioned below an imaginary horizontal line  54  extending in the depthwise direction  53  in  FIG. 3 , the imaginary horizontal line  54  being positioned at a vertically intermediate height of the cartridge body  31  and passing through a center point between upper and lower ends of the front wall  40  and another center point between upper and lower ends of the rear wall  42 . 
     The ink supply portion  37  has a cylindrical configuration protruding from the front wall  40  frontward in the installation direction  56  (in a direction away from the ink chamber  36 ). An ink passage  38  extending in the installation direction  56  is formed in the ink supply portion  37 . The ink passage  38  has an outer end functioning as an ink supply outlet  71  which is opened or closed by an ink supply valve (not shown). The ink supply outlet  71  is in fluid communication with the ink chamber  36  through the ink passage  38 . The cartridge installation portion  110  is provided with an ink needle  122  ( FIG. 4 ). Upon installing the ink cartridge  30  into the cartridge installation portion  110 , the ink needle  122  is inserted into the ink supply outlet  71  to open the ink supply valve, whereupon ink is flowed out of the ink chamber  36  into the ink needle  122  through the ink passage  38 . 
     Instead of the ink supply valve, a film covering the ink supply outlet  71  is available. In the latter case, upon installation of the ink cartridge  30  into the cartridge installation portion  110 , the ink needle  122  breaks the film to open the ink supply outlet  71 . 
     As shown in  FIGS. 2 and 3 , the protrusion  46  is provided at the lower end portion of the front wall  40 , i.e., the protrusion  46  is positioned lower than the ink supply portion  37  on the front wall  40 . 
     The protrusion  46  has a width approximately the same as that of the front wall  40  in the widthwise direction  51 . The protrusion  46  protrudes from a lower end of the front wall  40  in a direction away from the rear wall  42  (frontward in the installation direction  56 ). The protrusion  46  has a tip end  75  positioned farther frontward than the ink supply outlet  71  in the installation direction  56 . The protruding length of the protrusion  46  is altered depending on a type of the ink cartridge  30 , such as ink color, ink constituent, and amount of ink to be initially stored in the ink chamber  36 . The protrusion  46  corresponds to a particular interface. The protrusion  46  may be biased by a biasing member  139 ,  135  in a direction  55  opposite to the installation direction  56 . Moreover, the protrusion  46  may protrude from an upper end of the front wall  40  in the installation direction  56 . 
     As shown in  FIG. 2 , the cartridge body  31  further includes a guide portion  35  protruding upward from the top wall  39  and extending in the depthwise direction  53 . A rib or projecting segment is available as the guide portion  35 . Further, the guide portion  35  has a width smaller than that of the cartridge body  31 . 
     Another guide portion  44  protrudes downward from the bottom wall  41  and extends in the depthwise direction  53 . A rib or projecting segment is available as the guide portion  44 . Further, the guide portion  44  has a width smaller than that of the cartridge body  31 . The cartridge installation portion  110  has guide grooves  109  ( FIG. 5 ) so as to guide the guide portions  35  and  44  therealong. 
     As described earlier, the printer  10  includes the ink supply device  100  configured to supply ink to the recording head  21 . The ink supply device  100  has the cartridge installation portion  110  in which the ink cartridge  30  can be detachably installed.  FIG. 1  shows an installed state of the ink cartridge  30  into the cartridge installation portion  110 . 
     The cartridge installation portion  110  will be described next in detail. As shown in  FIGS. 4 and 5 , the cartridge installation portion  110  is defined by a casing  101  that is a hollow box shaped member formed with the opening  112  at a front side of the printer  10 . An internal space of the casing  101  is defined by a top wall  111  formed with the guide grooves  109 , a bottom wall  107  also formed with the guide grooves  109 , a terminal end wall  104 , and a pair of side walls  115 ,  116  extending in the installation direction  56  and connecting the top wall  111  to the bottom wall  107 . The ink cartridge  30  is installed in and removed from the casing  101  through the opening  112 . At this time, the guide portion  35  is inserted into one of the guide grooves  109  at the top wall  111 , and the guide portion  44  is inserted into corresponding one of the guide grooves  109  at the bottom wall  107 . As a result, movement of the ink cartridge  30  in the installation direction  56  and the removal direction  55  can be guided by the guide grooves  109 . Four ink cartridges  30  of cyan, magenta, yellow and black are loaded into the casing  101 . 
     As shown in  FIG. 5 , three plates  102  extend in the vertical direction  52  are arrayed in the widthwise direction  51  so as to partition the internal space of the casing  101  into four vertically elongated spaces. Thus, four ink cartridges  30  are respectively installed in the four spaces. These plates  102  are positioned offset from the opening  112  but are positioned adjacent to or at the terminal end wall  104  of the casing  101 . 
     The bottom wall  107  has engagement holes  108 , each positioned in each guide groove  109 . In other words, respective engagement holes  108  are positioned near the plates  102 . The engagement hole  108  permits the ink leaked from the ink supply portion  37  to escape to the outside of the cartridge installation portion  110 , for example. To this effect, an ink tray (not shown) is disposed at a position below the engagement holes  108  in order to absorb the leaked ink by capillary force. In this embodiment, the bottom wall  107  of the cartridge installation portion  110  has four engagement holes  108 , each engagement hole  108  being formed as a through-hole of the bottom wall  107  of the cartridge installation portion  110  (also see  FIGS. 6 through 8 ). The engagement hole  108  corresponds to a locking section of the cartridge installation portion  110 . 
     As shown in  FIG. 4 , a connecting portion  103  is provided at the terminal end wall  104  of the casing  101 . The position of the connecting portion  103  is aligned with the ink supply portion  37  when the ink cartridge  30  is installed in the casing  101 . In the first embodiment, four connecting portions  103  are provided corresponding to four ink cartridges  30  installable in the casing  101 . 
     The connecting portion  103  includes the ink needle  122  and a holding portion  121 . The ink needle  122  is tubular shaped and is formed of a resin. The ink needle  122  is connected to the ink tube  20 . Each ink tube  20  connected to each ink needle  122  extends upward along an outer surface of the terminal end wall  104 , and extends to the recording head  21  (See  FIG. 1 ). 
     The holding portion  121  has a hollow cylindrical shape, and the ink needle  122  coaxially extends in the holding portion  121 . As shown in  FIG. 6 , upon installing the ink cartridge  30  into the cartridge installation portion  110 , the ink supply portion  37  is hermetically inserted, by a predetermined depth, into an inner peripheral surface of the holding portion  121 . As a result of the insertion of the ink supply portion  37  into the holding portion  121 , the ink needle  122  is inserted into the ink supply outlet  71 . Thus, the ink stored in the ink chamber  36  can be flowed into the ink needle  122  from the ink chamber  36 . 
     As shown in  FIG. 4 , the rod  124  extends from an upper portion of the terminal end wall  104  of the casing  101  in the removal direction  55 . Upon loading the ink cartridge  30  into the cartridge installation portion  110 , the rod  124  is inserted in the air communication passage  32   a  as shown in  FIG. 6 , thereby breaking the sealing film to allow the ink chamber  36  to communicate with the atmosphere. 
     As shown in  FIGS. 4 through 6 , a sensor unit is provided at the terminal end wall  104  at a position above the connecting portion  103 . The sensor unit includes the circuit substrate (not shown) and the optical sensor  114  assembled on the circuit substrate. The sensor unit contains four optical sensors  114  corresponding to four ink cartridges  30  insertable in the casing  101 . Each optical sensor  114  is positioned within each of the four spaces of the casing  101  (between the neighboring plates  102  or between one of the plates  102  and one of the side walls  115 ,  116 ). These optical sensors  114  are arrayed in line in the widthwise direction  51 . 
     Each optical sensor  114  includes the light emitting element  118  such as LED, and the light receiving element  119  such as a photo-transistor. The light emitting element  118  and the light receiving element  119  are surrounded by a U-shaped housing, and an outer shape of the optical sensor  114  is U-shaped. The light emitting element  118  is adapted to emit light in one direction from the housing. The light receiving element  119  is adapted to receive the light. The light emitting element  118  and the light receiving element  119  are facing each other with a predetermined distance in the U-shaped housing. The detection portion  33  of the ink cartridge  30  can be entered into a space between the light emitting element  118  and the light receiving element  119 , such that the optical sensor  114  may or may not detect receive the predetermined amount of light through the detection portion  33 . 
     As shown in  FIG. 5 , covers  105 ,  106  for covering the light emitting element  118  and light receiving element  119 , respectively are provided at the casing  101 . Four pairs of covers  105 ,  106  are provided for four optical sensors  114 . 
     As shown in  FIGS. 4 and 6 , a chamber  130  is provided at a lower end portion of the terminal end wall  104 , and a slide member  135  is movably retained in the chamber  130 . In the present embodiment, four slide members  135  are positioned to correspond to four ink cartridges  30  which the casing  101  can accommodate therein. Here, a number of slide members  135  may not necessarily be limited to four. The chamber  130  is in fluid communication with the internal space of the cartridge installation portion  110 . The slide member  135  has a substantially rectangular parallelepiped external shape. A rib  136  extends upward from the slide member  135  and is positioned in alignment with the protrusion  46  in the installation direction  56 , so that the tip end  75  of the protrusion  46  is abuttable on the rib  136 . In other words, the slide member  135  is positioned in an insertion path of the protrusion  46  of the ink cartridge  30  into the cartridge loading section  110  and contacts the tip end  75  of the protrusion  46  during the installation process of the ink cartridge  30 . 
     A coil spring  139  is disposed in the chamber  130  for biasing the slide member  135  toward the opening  112 , i.e., for biasing the ink cartridge  30  in the removal direction  55 . The coil spring  139  is interposed between the slide member  135  and a terminal wall  131  defining an inner terminal end of the chamber  130 . The slide member  135  is positioned at a predetermined position on a side closer to the opening  112  when the coil spring  139  has a natural length, i.e., when the slide member  135  is not applied with an external force, as shown in  FIG. 4 . In the process of the installation of the ink cartridge  30  into the cartridge installation portion  110 , the protrusion  46  is brought into contact with the slide member  135 , and the slide member  135  is pressed and slidingly moved toward the terminal wall  131  of the chamber  130  against the biasing force of the coil spring  139 . Thereby, the coil spring  139  is contracted, and the slide member  135  slides to a position on another side of the chamber  130  closer to the terminal wall  131  as shown  FIG. 6 . Consequently, the compressed coil spring  139  biases the ink cartridge  30  in the removal direction  55  via the slide member  135 . In other words, the protrusion  46  of the ink cartridge  30  is subjected to the biasing force from the slide member  135  and the coil spring  139 . The slide member  135  and the coil spring  139  correspond to a biasing member. 
     As shown in  FIG. 4 , the casing  101  includes a cartridge holding mechanism  144 . The holding mechanism  144  includes a lever portion  145 , a support shaft  147 , and a coil spring  148 . The lever portion  145  serves to retain the ink cartridge  30  installed in the cartridge installation portion  110  at an installed position against the biasing force of the coil spring  139 . The lever portion  145  is provided at an upper end of the opening  112  of the casing  101 . In the first embodiment, four levers  145  are provided in correspondence with four ink cartridges  30  installable in the casing  101 . 
     The lever portion  145  has a substantially arm shape. The lever portion  145  has a center portion through which the support shaft  147  extends. The support shaft  147  is supported to the casing  101 . Thus, the lever portion  145  is pivotally movable about the support shaft  147  at the upper portion of the opening  112 . 
     The lever portion  145  has one side serving as an operation portion  149  and another side serving as a pressing portion  146 . The operation portion  149  extends outward from the opening  112  for user&#39;s manually pivotally moving the lever portion  145 . 
     The pressing portion  146  extends into the casing  101 . The pressing portion  146  has a tip end portion  146 A. The coil spring  148  (as an example of biasing members) is interposed between the casing  101  and the lever portion  145  to bias the pressing portion  146  downward (to pivotally move the pressing portion  146  in the clockwise direction in  FIG. 4 ). The pressing portion  146  is adapted to abut on the guide portion  35  of the ink cartridge  30  and presses the ink cartridge  30  downward during loading of the ink cartridge  30  into the cartridge installation portion  110  due to the biasing force of the coil spring  148 . 
     As shown in  FIG. 3 , the bottom wall  41  of the ink cartridge  30  has a front side portion that is formed with a recess  94  whose open end is at a lower surface of the cartridge body  31 . As shown in  FIG. 6 , the bottom wall  41  is in direct confrontation with the bottom wall  107  of the cartridge installation portion  110 . The recess  94  has a width equal to that of the bottom wall  41 , and the recess  94  also extends through the guide portion  44 . As a modification, the width of the recess  94  can be smaller than that of the bottom wall  41 . 
     A leaf spring  90  is provided at the bottom wall  41  at a position adjacent to the recess  94 . The leaf spring  90  has a width substantially equal to or smaller than that of the recess  94 , so that the leaf spring  90  can be received in the recess  94  during installation or removal process. The leaf spring  90  serves as an engagement portion in the present embodiment. The leaf spring  90  (engagement portion) engages the engagement hole  108  (corresponding to the locking member) of the cartridge installation portion  110 , as will be described next. 
     In the first embodiment, the position of the recess  94  and the leaf spring  90  in the depthwise direction  53  is coincident with the position of the engagement hole  108  when the ink cartridge  30  is in the installed state in the cartridge installation portion  110 . The position of the recess  94  and the leaf spring  90  is not limited to the above position. For example, if the cartridge installation portion  110  is formed with additional recess or opening other than the engagement hole  108 , the recess  94  and leaf spring  90  can be positioned to be in coincidence with the additional recess or opening. 
     The leaf spring  90  has a first part  91 , a second part  92  and a third part  93 . These parts of the leaf spring  90  are flat shape in which lengths in the depthwise direction  53  and widthwise directions  51  are greater than a length (thickness) in the vertical direction  52 . Further, these three parts  91 ,  92 ,  93  have flat surfaces. The first through third parts  91 ,  92 ,  93  are arranged in this order and integral in the depthwise direction  53 , and the leaf spring  90  is made from a resilient material such as a metal. 
     The third part  93  is fixed to one of the guide portion  44  and the bottom wall  41  ( FIG. 3  shows the third part  93  fixed to the guide portion  44 ). The third part  93  extends in the depthwise direction  53 , i.e., horizontally. 
     The second part  92  has one end (at the rear wall  42  side) integrally connected to the third part  93  and another end (at the front wall  40  side) integrally connected to the first part  91 . The one end is positioned higher than the other end. In other words, the second part  92  is inclined such that the other end (at the front wall  40  side) is positioned farther from a bottom surface  97  of the recess  94  than the one end (at the rear wall  42  side) from the bottom surface  97 . 
     The first part  91  has one end (at the rear wall  42  side) integrally connected to the other end of the second part  92 , and has another free end (at the front wall  40  side). Further, the one end of the first part  91  is positioned lower than the other end of the first part  91 . In other words, the first part  91  is inclined such that the one end (at the rear wall  42  side) of the first part  91  is positioned farther from the bottom surface  97  of the recess  94  than the other end (at the front wall  40  side) from the bottom surface  97 . 
     Since one end (at the rear wall  42  side) of the leaf spring  90  is fixed whereas the other end (at the front wall  40  side) of the leaf spring  90  is a free end, and since the leaf spring  90  is made from the resilient material, the leaf spring  90  is resiliently deformed in a counterclockwise direction  96  in  FIG. 3  when pressed from below. In other words, the first part  91  and second part  92  are pivotally moved about a boundary  95  between the second part  92  and the third part  93 , so that the first part  91  and second part  92  are received in the recess  94 . 
     As shown in  FIG. 3 , a first angle θ 1  is defined as an intersection angle between a broken line extending along the lower surface of the bottom wall  41  and upper or lower surface of the first part  91 , and a second angle θ 2  is defined as an intersection angle between the broken line and upper or lower surface of the second part  92 . Here, the second angle θ 2  is greater than the first angle θ 1 . In other words, the second part  92  is steeper than the first part  91  relative to the broken line. 
     Apparently, the combination of the first part  91  and the second part  92  provides a V-shape whose bent corner is positioned lower than the remaining portion. In other words, the combined shape of the first and second regions  91 ,  92  protrudes from the bottom wall  41  toward the bottom wall  107  of the cartridge installation portion  110 . The lower surface of the first part  91  corresponds to a first guide surface and the lower surface of the second part  92  corresponds to a second guide surface. 
     In the above described embodiment, the engagement portion (leaf spring  90 ) has a flat upper and lower segmental surfaces. However, an arcuate or spherical surface is also available. Further, in the depicted embodiment, the leaf spring  90  and the recess  94  are provided at the bottom wall  41 . However, these can be provided at one of the top wall  39  and the side walls  83 ,  84 . 
     The cartridge body  31  of the ink cartridge  30  may have a printed marking that specifies nipping regions for user&#39;s access to the ink cartridge  30 . Alternatively, an anti-slipping member is provided to the cartridge body  31 , or an anti-slipping shape is partly formed at an outer perimeter of the cartridge body  31  for facilitating nipping of the cartridge body  31  by user&#39;s fingers. For example, a projection  74  shown by a broken line in  FIG. 6  can be provided for a finger gripped portion. The projection  74  protrudes from the rear wall  42  in the removal direction  55 . Further, the projection  74  is at a vertical position between the imaginary horizontal line  54  and the upper end of the cartridge body  31 . Installation and removal of the ink cartridge  30  into and from the cartridge installation portion  110  can be easily performed by nipping the projection  74  with user&#39;s fingers. 
     A process of installation operation of the ink cartridge  30  into the cartridge installation portion  110  will be described with reference to  FIGS. 6 through 8 . 
     As shown in  FIG. 7 , the ink cartridge  30  is aligned with the opening  112  after opening the cover member (not shown) that normally covers the opening  112 , such that the front wall  40  is at a leading side in the installation direction  56 . For the installation of the ink cartridge  30 , a user holds by his fingers a portion of the cartridge body  31 , the portion being close to the rear wall  42 . The finger-held portion of the cartridge body  31  is not definite. However, according to an envisioned or assumed loading manner, the insertion of the ink cartridge  30  into the cartridge installation portion  110  is accompanied by user&#39;s looking down the opening  112  of the cartridge installation portion  110  provided that the printer  10  is often installed on a user&#39;s desk. Therefore, the user may often nip with his fingers a portion located in a region spanning between the vertical center portion and the upper end portion of the cartridge body  31 . 
     In the initial stage of insertion of the ink cartridge  30  into the cartridge installation portion  110 , a tip end (a leading end portion) of the guide portion  35  comes into contact with the lever portion  145 . When the ink cartridge  30  is further inserted into the cartridge installation portion  110 , the pressing portion  146  of the lever portion  145  rides over the guide portion  35 . Thus, the lever portion  145  is pivotally moved in the counterclockwise direction in  FIG. 8 . Since the lever portion  145  is biased to be pivotally moved in the clockwise direction by the biasing force of the coil spring  148 , the ink cartridge  30  is pushed downward by the holding mechanism  144 . Consequently, the leaf spring  90  is brought into contact with an upper surface of the bottom wall  107  of the casing  101 . Accordingly, as shown in  FIG. 8 , the first part  91  and second part  92  of the leaf spring  90  are resiliently deformed by the upper surface, so that these parts are received in the recess  94 . 
     When the ink cartridge  30  is further inserted into the cartridge installation portion  110 , the tip end  75  of the protrusion  46  (the particular interface) is brought into abutment with the slide member  135  biased toward the opening  112  by the coil spring  139 . Then, the ink cartridge  30  is further inserted into the cartridge installation portion  110  against the biasing force of the coil spring  139 . That is, the user is required to push the rear wall  42  of the ink cartridge  30  further frontward in the installation direction  56 . The installation velocity is thus reduced (moderated) by the biasing force of the coil spring  139 . 
     When the ink cartridge  30  is further inserted into the cartridge installation portion  110 , the recess  94  of the ink cartridge  30  is brought into alignment with the engagement hole  108  of the cartridge installation portion  110  as shown in  FIG. 6 . Therefore, no pressing force is exerted on the leaf spring  90  from the bottom wall  107 . As a result, the leaf spring  90  having been received in the recess  94  is then received in the engagement hole  108  to restore original posture shown in  FIG. 3 . As a result, the second part  92  comes into engagement with a boundary edge of the bottom wall  107  which constitutes the engagement hole  108 . 
     In a state shown in  FIG. 6 , the ink cartridge  30  is biased in the removal direction  55  by the biasing force of the coil spring  139  via the protrusion  46 . Therefore, if the user released his fingers from the ink cartridge  30 , the ink cartridge  30  is pushed in the removal direction  55  by the coil spring  139 . However, displacement of the ink cartridge  30  in the removal direction  55  can be restrained since the second part  92  is in contact with the boundary edge of the engagement hole  108 , thereby retaining the installed state shown in  FIG. 6 . In other words, the engagement of the leaf spring  90  with the engagement hole  108  retains the installed state of the ink cartridge  30  as shown in  FIG. 6  against the biasing force of the coil spring  139 . 
     When the user nips the rear wall  42  of the ink cartridge  30  with his fingers and pulls out the fully installed ink cartridge  30  in the removal direction  55 , the second part  92  is pushed by the boundary edge of the engagement hole  108 , so that the leaf spring  90  is resiliently deformed to be pivotally moved in the direction indicated by the arrow  96  in  FIG. 3 . Thus, the leaf spring  90  is disengaged from the boundary edge of the engagement hole  108  and is received in the recess  94 . At this time, as shown in  FIG. 8 , at least a part of the leaf spring  90  is positioned in the recess  94 . 
     As a result of reception of the leaf spring  90  into the recess  94 , the user can pull the ink cartridge  30  in the removal direction  55 . The ink cartridge  30  is then pulled out of the cartridge installation portion  110  through the opening  112  by the user to provide a state shown in  FIG. 7 . 
     The leaf spring  90  is provided at the ink cartridge  30  for retaining the installed state of the ink cartridge  30 . Therefore, no additional component or part is required in the cartridge installation portion  110  for retaining the installed state. The leaf spring  90  is attached to the bottom wall  41  of the ink cartridge  30  in this embodiment, but, can be integrally molded with the ink cartridge  30  (for example, with the bottom wall  41 ). 
     In the above-described embodiment, the holding mechanism  144  does not lock the ink cartridge  30  at the fully installed position, but presses the ink cartridge  30  downward. In other words, no locking structure is provided between the holding mechanism  144  and the ink cartridge  30 . Therefore, loading and unloading of the ink cartridge  30  into and from the cartridge installation portion  110  can be performed even if the holding mechanism  144  is damaged or broken. 
     Further, if the biasing force of the coil spring  148  in the holding mechanism  144  is sufficiently large to move the ink cartridge  30  downward such that the bottom wall  41  is brought into contact with the bottom wall  107  of the casing  101 , a resultant frictional force between the bottom wall  41  of the ink cartridge  30  and the bottom wall  107  of the casing  101  in the installation direction  56  can become greater than the biasing force of the coil spring  139  acting in the removal direction  55 . As a result, the installed state of the cartridge  30  into the cartridge installation portion  110  can be retained. 
     Further, when the ink cartridge  30  is initially inserted into the cartridge installation portion  110 , the first part  91  is pushed by the upper surface of the bottom wall  107 , whereupon a frictional force is generated between the second part  92  of the leaf spring  90  and the upper surface. By selecting the resiliency of the leaf spring  90  or a frictional force of a material that is attached on the second part  92  of the leaf spring  90 , the frictional force between the second part  92  of the leaf spring  90  and the upper surface of the bottom wall  107  (a frictional coefficient generated by the second region  92 ) can be greater than the biasing force of the coil spring  139 . As a result, the ink cartridge  30  can be held at the installed position in the cartridge installation portion  110 . 
     Further, as shown in  FIG. 3 , the second angle θ 2  is greater than the first angle θ 1 . Generally, resilient deformation of the leaf spring  90  can easily occur if these angles are smaller when the leaf spring  90  is pressed by the bottom wall  107  of the cartridge installation portion  110 . Therefore, the installation process of the ink cartridge  30  into the cartridge installation portion  110  attributed to the pressed deformation of the first part  91  by the bottom wall  107  can be performed with a force smaller than a force required in removal of the ink cartridge  30  from the cartridge installation portion  110  attributed to the pressed deformation of the second part  92  by the bottom wall  107 . 
     Hereinafter, other embodiments of the present invention will be described with accompanying drawings wherein like parts and components are designated by the same reference numerals as those of the first embodiment to avoid duplicating description. 
     An ink cartridge  30 A according to a second embodiment of the present invention is shown in  FIG. 9 . A cartridge body  31 A has a guide portion  35 A formed with a latching portion  43  engageable with the tip end portion  146 A of the holding mechanism  144 . The latching portion  43  includes a vertical engaging surface having a height and a width. The pressing portion  146  of the holding mechanism  144  rides on a top surface of the guide portion  35 A when the ink cartridge  30 A is initially inserted into the cartridge installation portion  110 . When the engaging surface of the latching portion  43  is aligned with the tip end portion  146 A as a result of movement of the ink cartridge  30 A in the installation direction  56 , the holding mechanism  144  is pivotally moved in the clockwise direction in  FIG. 9  by the biasing force of the coil spring  148 , so that the tip end portion  146 A is engaged with the engaging surface of the latching portion  43 . Therefore, the installed position can also be locked by the holding mechanism  144 . This is in contrast to the first embodiment where the holding mechanism  144  does not lock the ink cartridge  30  at the installed position, but merely presses the ink cartridge  30  downward. 
     More specifically, the lever portion  145  can provide a lockable pivot position as shown in  FIG. 4  by the biasing force of the coil spring  148  where the tip end portion  146 A is engageable with the latching portion  43 , and can provide an unlocked pivot position as shown in  FIG. 6  where the engagement portion  146 A cannot be engaged with the latching portion  43 . 
     If the operation portion  149  is manually pressed downward, the holding mechanism  144  is pivotally moved from the lockable position to the unlocked position. The holding mechanism  144  also functions as a locking mechanism in the second embodiment, in addition to as the cartridge holding mechanism. Instead of the vertical engaging surface of the latching portion  43 , a sloped engaging surface  43 ′ as shown by a broken line in  FIG. 9  is also available. Still alternatively, the engaging surface of the latching portion  43  may be provided by a plate member extending in the installation direction  56  and the widthwise direction  51 . 
       FIG. 10  shows an ink cartridge  30 B according to a third embodiment of the present invention. In the ink cartridge  30 B, a cartridge body  31 B has a height lower than that of the foregoing embodiments. More specifically, the lowermost portion of the lever portion  145  (i.e., a lower surface of the engagement portion  146 A) at its lockable position is out of contact from the uppermost surface of the cartridge body  31 B (i.e., a top surface of a guide portion  35 B) when the ink cartridge  30 B is installed in the cartridge installation portion  110 . Therefore, the holding mechanism  144  does not act on the ink cartridge  30 B at any phase during the installation and removal process of the ink cartridge  30 B. Still however, the ink cartridge  30 B can be remained at the installed position because of the engagement of the leaf spring  90  with the boundary edge of the engagement hole  108  against the biasing force of the biasing member  139 . 
     An ink cartridge  30 C according to a fourth embodiment of the present invention will be described with reference to  FIGS. 11 and 12 . In the fourth embodiment, a cartridge body  31 C is formed with a protrusion  125 , as the engagement portion, on the lower surface of the bottom wall  41 . 
     More specifically, the protrusion  125  has a segmental spherical surface and is disposed at the outer surface of the bottom wall  41  of the ink cartridge  30 C, that is, a lower surface of the cartridge body  31 C. The protrusion  125  is provided at a position in confrontation with the engagement hole  108  when the ink cartridge  30 C is inserted in the cartridge installation portion  110 . The ink cartridge  30 C is installed into or removed from the cartridge installation portion  110 , as shown in  FIG. 12 , while being slightly lifted up. When the ink cartridge  30 C is installed in the cartridge installation portion  110 , the protrusion  125  is in engagement with the engagement hole  108 . 
     The protrusion  125  is disposed at the bottom wall  41  in the fourth embodiment, but, can be disposed at the top wall  39 , or at the side walls  83 ,  84 . 
     The engagement portion may be disposed at one of surfaces (outer surface of the top wall  39 , the bottom wall  41 , the front wall  40  or the side walls  83 ,  84 ) in confrontation with a through-hole or an opening (the engagement hole  108  in the fourth embodiment), a recess (not shown), or a projection (not shown) formed in the inner perimeter of the cartridge installation portion  110  (i.e., the top wall  111 , the bottom wall  107 , the pair of side walls  115 ,  116 , or the terminal end wall  104 ). The surface at which the engagement portion is disposed (outer surface of the top wall  39 , the bottom wall  41 , the front wall  40  or the side walls  83 ,  84 ) corresponds to the first surface. The engagement portion is formed in a shape engageable with the through-hole (opening), the recess, or the projection. Still further, the engagement portion may be disposed at the first surface so as to be engageable with the neighboring plate  102  partitioning the inner space of the cartridge installation portion  110 . 
     In the installed state of the ink cartridge  30 C in the cartridge installation portion  110 , the ink cartridge  30 C is biased by the slide member  135  and the coil spring  139  in the removal direction  55 . However, in the fourth embodiment, the ink cartridge  30 C can resist the biasing force of the slide member  135  and the coil spring  139  by engagement of the protrusion  125  (or can be a through-hole, opening, protrusion, or recess) of the ink cartridge  30 C with the engagement hole  108  (or a protrusion, recess, opening or projection in accordance with the shape of the corresponding engagement portion) of the cartridge installation portion  110 . As a result, the ink cartridge  30 C can be retained at the installed position. 
     If the cartridge installation portion  110  is formed with a recess or an opening other than the engagement hole  108 , the recess  94  and the leaf spring  90  can be provided (instead of the protrusion  125 ) at a position in confrontation with the recess or the opening. 
     When a projection is provided on at least one of the top wall  111 , the bottom wall  107 , the terminal end wall  104 , the pair of side walls  115 ,  116 , and the plate  102  of the cartridge installation portion  110 , the engagement portion of the ink cartridge  30 C can be a recess having a shape engageable with the projection and provided on the at least one of the outer surfaces of the top wall  39 , the bottom wall  41 , the front wall  40  and the side walls  83 ,  84  of the cartridge body  31  so as to be in confrontation with the projection. 
     An ink cartridge  30 D according to a fifth embodiment of the present invention will be described with reference to  FIG. 13 . In the fifth embodiment, a guide portion  44 D has a shape different from the guide portion  44  of the forgoing embodiments and serves as the engagement portion. The guide portion  35  remains unchanged and is also available on the ink cartridge  30 D. 
     The guide portion  44 D protrudes downward from the bottom wall  41 . As shown in  FIG. 13 , the guide portion  44 D has a pair of side surfaces  77 ,  78  extending in the vertical direction  52  and in the depthwise direction  53  and facing each other in the widthwise direction  51 . The cartridge installation portion  110  is formed with the guide groove  109  having a pair of side walls  76 A,  76 B extending in the installation direction  56 . The side surface  77  confronts the side wall  76 A while the side surface  78  confronts the side wall  76 B. The pair of side surfaces  77 ,  78  are positioned between the side walls  76 A,  76 B of the guide grooves  109  in the widthwise direction  51 . That is, the guide portion  44 D has a width smaller than that of the guide groove  109 . The side surface  77  extends diagonally frontward in the installation direction  56  and outward in the widthwise direction  51 , such that the side surface  77  gradually approaches the side wall  76 A in the installation direction  56 . The side surface  78  extends diagonally frontward in the installation direction  56  and outward in the widthwise direction  51 , such that the side wall  76 B gradually approaches the side surface  78  in the installation direction  56 . In other words, the width of the guide portion  44 D is gradually increased toward the front wall  40  in installation direction  56 . The side surface  77  has a portion  77 A adjacent to the front wall  40 , and the portion  77 A is in brought into contact with the side wall  76 A. The side surface  78  has a portion  78 A adjacent to the front wall  40 , and the portion  78 A is brought into contact with the side surface  76 B. The portions  77 A,  78 A of the side surfaces  77 ,  78  have sufficient square measure to restrain the cartridge body  31  installed in the cartridge installation portion  110  from moving in the removal direction  55  against the biasing force biasing the cartridge body  31 . 
     In this embodiment, the side surfaces  77 ,  78  have a flat plane (surface), but a step-like surface is also applicable as the side surface  77 ,  78 . 
     When the ink cartridge  30 D is being installed into or removed from the cartridge installation portion  110 , the portions  77 A,  78 A of the side surfaces  77 ,  78  are brought into contact with the side walls  76 A,  76 B, respectively. As a result, a frictional force applying a load against the biasing force of the slide member  135  and the coil spring  139  is generated. Hence, the ink cartridge  30 D can be retained at the installed position. The guide groove  109  that is engageable with the guide portion  44 D (engagement portion) corresponds to the locking section in the fifth embodiment. 
     Either the guide portion  44 D or the guide portion  35  can be formed as described above. Alternatively, both of the guide portion  44 D and the guide portion  35  can be formed as described above. Further, the guide groove  109  can be formed on at least one of the side walls  115 , 116 , and the plate  102  of the cartridge installation portion  110 , and the guide portion  44 D can be provided on at least one of the side walls  83 ,  84  of the cartridge body  31 D. 
     An ink cartridge  30 E according to a sixth embodiment of the present invention is shown in  FIG. 14 . As shown in  FIG. 14 , a latch lever  151  is also available as the engagement portion. The latch lever  151  can be disposed at one of the top wall  39 , the bottom wall  41  and the side walls  83 ,  84  of the ink cartridge  30 E. In  FIG. 14 , the latch lever  15  is disposed at the recess  94  formed in the bottom wall  41 . 
     The latch lever  151  is formed in a plate shape. The latch lever  151  has a rear-side end portion formed with a through-hole  152 . The through-hole  152  allows a shaft (not shown) to penetrate therethrough in the widthwise direction  51 . Each widthwise end of the shaft is rotatably supported by a protrusions  45  protruding from a rear wall of the recess  94 . The latch lever  151  is pivotally movable about the shaft in directions indicated by arrows  153 ,  154  in  FIG. 14 . 
     Pivotal movement of the latch lever  151  in the direction  153  brings the latch lever  151  into contact with the rear wall of the recess  94 . Hence, the pivotal movement of the latch lever  151  in the direction  153  is stopped at a position indicated by a solid line in  FIG. 14  (hereinafter referred to as “first position” or “lock position”). Further, pivotal movement of the latch lever  151  in the direction  154  brings the latch lever  151  into contact with a bottom wall  97  of the recess  94 . Hence, the pivotal movement of the latch lever  151  in the direction  154  is stopped at a position indicated by a broken line in  FIG. 14  (hereinafter referred to as “second position” or “release position”). The latch lever  151  is thus movable between the first position and the second position. 
     Further, the latch lever  151  is urged in the direction  153  by an urging member (not shown). A torsion spring is employed as the urging member, for example. The torsion spring includes a coil portion and two arm portions extending from each end of the coil portion. The coil portion is provided to the pivot shaft. The two arm portions are connected to the latch lever  151  so as to define an angle for biasing the latch lever  151  in the direction  153 . 
     When the ink cartridge  30 E is not installed in the cartridge installation portion  110 , the latch lever  151  is in the first position. When the ink cartridge  30 E is being inserted into the cartridge installation portion  110 , the latch lever  151  is pushed by the bottom wall  107  of the cartridge installation portion  110 , thereby changing its position from the first position to the second position. When the ink cartridge  30 E is further inserted into the cartridge installation portion  110  so that the recess  94  of the ink cartridge  30  confronts the engagement hole  108  of the cartridge installation portion  110 , the latch lever  151  again changes its position from the second position to the first position. As a result, the ink cartridge  30 E can be retained at the installed position. The recess  94  that is engageable with the latch lever  151  (engagement portion) corresponds to the locking section in the sixth embodiment. 
     When the ink cartridge  30 E is removed from the cartridge installation portion  110 , the ink cartridge  30 E is pulled out in the removal direction  55  while being slightly lifted upward by the user. That is, in the sixth embodiment, in the same manner as  FIG. 10 , the ink cartridge  30 E has a height smaller than that of the ink cartridge  30  shown in  FIG. 3 . 
     In the sixth embodiment, the latch lever  151  is provided on the ink cartridge  30 E. However, the latch lever  151  can be provided on the cartridge installation portion  110  (for example, on the engagement hole  108 ). 
     An ink cartridge  30 F according to a seventh embodiment of the present invention is shown in  FIG. 15 . As shown in  FIG. 15 , a resiliently deformable latch lever  151 F extends in the depthwise direction  53  and has a base end that is resiliently supported on at least a front portion of the bottom wall  41  of the ink cartridge  30 F. The latch lever  151 F includes a latching knob  155  provided at a free end opposite to the base end, and a protrusion  156  functioning as a latching claw. In this embodiment, the latching claw  156  serves as the engagement portion. In the installed state of the ink cartridge  30 F in the cartridge installation portion  110 , the latching knob  155  protrudes from the opening  112  of the cartridge installation portion  110 . Further, in the installed state of the ink cartridge  30 F in the cartridge installation portion  110 , one surface of the latching claw  156  faces the boundary edge of the bottom wall  107  which constitutes the engagement hole  108 , and the latching claw  156  is in engagement with the engagement hole  108 . The engagement hole  108  that is engageable with the latching claw  156  (engagement portion) corresponds to the locking section in the seventh embodiment. 
     When the ink cartridge  30 F is unloaded from the cartridge installation portion  110 , the user holds the top wall  39  and the latching knob  155  and pulls up the cartridge body  31 F upward so as to disengage the latching claw  156  from the boundary edge of the engagement hole  108 . If the user releases the latching knob  155 , the latching knob  155  is resiliently moved downward to engage the latching claw  156  with the boundary edge of the engagement hole  108 . In the seventh embodiment, in the same manner as  FIGS. 10 and 14 , the ink cartridge  30 F has a height smaller than that of the ink cartridge  30  shown in  FIG. 3 . Hence, upward pivotal movement of the latching knob  155  enables the latching claw  156  to disengage from the boundary edge of the engagement hole  108 . Further, since the slide member  135  presses the protrusion  46 , the ink cartridge  30 F is pushed out of the cartridge installation portion  110  in the removal direction  55 . Thus, the latch lever  151 F helps user&#39;s removal of the ink cartridge  30 F from the cartridge installation portion  110 . 
     The latch lever  151 F is disposed at the bottom wall  41  in the seventh embodiment, but can be disposed at one of the top wall  39 , the front wall  40  and the side walls  83 ,  84  of the ink cartridge  30 F. In either case, the latch lever  151 F may be engaged with a part of the cartridge installation portion  110 , such as the plates  102 , the guide grooves  109 , and the rod  124 . 
     Various modifications are conceivable. 
     First Modification 
     In the process of inserting the ink cartridge into the cartridge installation portion  110  or removing the ink cartridge from the cartridge installation portion  110 , frictional contact of the engagement portion with an inner perimeter of the cartridge installation portion  110  (the top wall  111 , the bottom wall  107 , the front wall  40 , the pair of side walls  115 ,  116 ) can generate a frictional force that is greater than the biasing force of the coil spring  139  and that applies a resistive load against the biasing force. As long as such frictional force can be generated, the engagement portion is not limited to the leaf spring  90 . 
     For example, an elastic member, such as rubber, is available as the engagement portion. The elastic member can be provided at a portion where the engagement portion comes into contact with the inner perimeter of the cartridge installation portion  110  when the ink cartridge is installed in or removed from the cartridge installation portion  110 . The elastic member is provided on at least one of outer surfaces of the top wall  39 , the bottom wall  41 , the front wall  40 , the side walls  83 ,  84 , the guide portion  35 , and the guide portion  44  so as to be stretched therealong. Here, the outer surface is a surface in direct confrontation with the inner perimeter of the cartridge installation portion  110  when the ink cartridge is loaded into or unloaded from the cartridge installation portion  110 . As described above, the portion where the engagement portion comes into contact with the inner perimeter of the cartridge installation portion  110  is at least one of the surfaces of the top wall  39 , the bottom wall  41 , the front wall  40  and the side walls  83 ,  84 . When the ink cartridge is installed in the cartridge installation portion  110 , the elastic member provided on the outer surface of the ink cartridge is brought into close contact with the inner perimeter of the cartridge installation portion  110 , thereby generating a frictional force. 
     However, the elastic member can be dispensed with. Without the elastic member provided at the outer surface, the frictional force can be generated by direct contact of the outer surface of the ink cartridge with the inner perimeter of the cartridge installation portion  110 . 
     Further, the elastic member can be provided at the outer peripheral surface of the ink supply portion  37 . As shown in  FIG. 6 , upon installation of the ink cartridge  30  into the cartridge installation portion  110 , the ink supply portion  37  is inserted into the cylindrical holding portion  121 . As a result, the elastic member provided at the outer peripheral surface of the ink supply portion  37  is brought into close contact with the inner peripheral surface of the holding portion  121 , thereby generating a frictional force. 
     Further, the elastic member can be provided at an inner peripheral surface of the air communication passage  32   a . As shown in  FIG. 6 , upon insertion of the ink cartridge  30  into the cartridge installation portion  110 , the rod  124  is inserted into the air communication passage  32   a . As a result, the elastic member provided at the inner peripheral surface of the air communication passage  32   a  is brought into close contact with the outer peripheral surface of the rod  124 , thereby generating a frictional force. The elastic member is provided not at all the inner peripheral surface of the air communication passage  32   a  but at a part of the inner peripheral surface of the air communication passage  32   a  for permitting the air in the ink chamber  36  to be communicated with the atmosphere when the ink cartridge  30  is installed in the cartridge installation portion  110 . 
     Further, in case that the air communication passage  32   a  is provided at one of the outer surfaces of the ink cartridge other than the front wall  40 , the elastic member may be provided at the front wall  40 . Specifically, the front wall  40  may be formed with a hole, an opening or a recess at which the elastic member is disposed. A portion of the cartridge installation portion  110  (for example, the rod  124 ) is engageable with the hole, an opening or a recess formed on the front wall  40 . 
     Further, the elastic member can be provided at the pair of side walls  85 ,  86  of the detection portion  33  (shown in  FIG. 2 ). In the installed state of the ink cartridge  30  in the cartridge installation portion  110 , the side walls  85 ,  86  are in direct confrontation with the covers  105 ,  106  (shown in  FIG. 5 ), respectively. Therefore, the elastic member provided at the pair of side walls  85 ,  86  are brought into close contact with the covers  105 ,  106 , thereby generating a frictional force. In order not to impair the inherent function of the detection portion  33  (the function for transmitting light emitted from the optical sensor  114 ), the elastic member is provided at a part of the side walls  85 ,  86  of the detection portion  33  (a portion except for an area irradiated with the light emitted from the optical sensor  114 ). 
     Further, the leaf spring  90  of the first embodiment is applicable to the elastic member. As described while referring to  FIG. 8 , when the ink cartridge  30  is being inserted into the cartridge installation portion  110 , the first guide part  91  of the leaf spring  90  is pressed against the bottom wall  107  of the cartridge installation portion  110  so as to be resiliently deformed. As a result of resilient deformation, the first guide part  91  is accommodated within the recess  94 . At this time, the first guide part  91  is in pressure contact with the bottom wall  107 , thereby generating the frictional force. 
     In the first modification described above, the frictional contact of the engagement portion with the inner perimeter of the cartridge installation portion  110  can generate the frictional force in the installation direction  56  that is greater than the biasing force generated by the coil spring  139 . As a result, the frictional force can prevent the ink cartridge from being moved in the removal direction  55  against the biasing force of the coil spring  139 . 
     Second Modification 
     As the engagement portion, a member having a frictional force acting upon installation of the ink cartridge into the cartridge installation portion  110  that is smaller than a frictional force acting upon unloading of the ink cartridge from the cartridge installation portion  110  is also available. 
     For example, as the engagement portion, a member having high-frictional properties (or an anti-slippage member) is also available. The high-frictional member includes a plurality of protrusions formed in a predetermined area of a portion where the engagement portion comes into contact with the cartridge installation portion  110  when the ink cartridge is installed into or removed from the cartridge installation portion  110 . 
     Here, the portion where the engagement portion is brought into contact with the cartridge installation portion  110  is at least one of the outer surfaces of the top wall  39 , the bottom wall  41 , the front wall  40  and the side walls  83 ,  84 , in the same manner as the first modification. 
     Each of the protrusions of the high-frictional member has a first slant surface and a second slant surface extending from the first slant surface. The first slant surface is oriented in the removal direction  55  and extends diagonally downward in the installation direction  56 . The second slant surface is oriented in the installation direction  56  and extends diagonally downward toward the rear wall  42 . 
     A third angle defined between the first slant surface and the outer surface is greater than a fourth angle defined between the second slant surface and the outer surface. That is, the first slant surface is steeper than the second slant surface relative to the outer surface. 
     Consequently, a frictional force generated by the first slant surface when the ink cartridge is removed from the cartridge installation portion  110  is greater than a frictional force generated by the second slant surface when the ink cartridge is installed into the cartridge installation portion  110 . Hence, the process of inserting the ink cartridge into the cartridge installation portion  110  can be easier than the process of removing the ink cartridge from the cartridge installation portion  110 . 
     Third Modification 
     The ink cartridge can be retained at the installed position by a pair of stoppers  126  (shown in  FIG. 5 ) provided in the guide groove  109  on the inner surface of the bottom wall  107  of the cartridge installation portion  110 . The pair of stoppers  126  protrudes inward in the widthwise direction  51  from the pair of side walls  76 A,  76 B (shown in  FIG. 14 ), respectively. The pair of stoppers  126  is in alignment with each other in the installation direction  56 , that is, each of the stoppers  126  is disposed at a rear end portion of the guide groove  109 . Each of the stoppers  126  has a height substantially the same as that of the side walls  76 A,  76 B. The stopper  126  is formed of an elastically deformable material such as a rubber. 
     When the ink cartridge  30  is being inserted into the cartridge installation portion  110 , the pair of side surfaces of the guide portion  44  (corresponding to the side surfaces  77 ,  78  shown in  FIG. 14  of the guide portion  44 D of the ink cartridge  30 D) is brought into contact with the pair of stoppers  126 . At this time, the user may have a click-like tactile impression in inserting the ink cartridge  30  into the cartridge installation portion  110 . However, if the user further inserts the ink cartridge  30  into the cartridge installation portion  110 , the pair of stoppers  126  is elastically deformed so as to be oriented outward of the guide grooves  109  in the widthwise direction  51 , that is, toward the pair of side walls  76 A,  76 B. Thus, the guide portion  44  can move past the pair of the stoppers  126  while the guide portion  44  is in contact with the pair of stoppers  126 , and the ink cartridge  30  is installed in the cartridge installation portion  110 . 
     When the ink cartridge  30  is installed in the cartridge installation portion  110 , the rear end portion of the guide portion  44  comes into contact with the pair of stoppers  126  and is tightly nipped thereby. Accordingly, the ink cartridge  30  can be retained at the installed position against the biasing force of the coil spring  139 . In other words, the ink cartridge  30  can be engaged with the cartridge installation portion  110  by the stoppers  126 . In the third modification, the guide portion  44  (more specifically, the rear end portion of the guide portion  44 ) corresponds to the first surface. 
     The ink cartridge  30  can be pulled out of the cartridge installation portion  110  by the user. At this time, because the guide portion  44  is in contact with the pair of stoppers  126 , the user finds slight resistance in removing the ink cartridge  30  from the cartridge installation portion  110 . However, if the user further pulls the ink cartridge  30  out of the cartridge installation portion  110 , the pair of stoppers  126  is elastically deformed so as to be oriented outward of the guide grooves  109  in the widthwise direction  51 , that is, toward the pair of side walls  76 A,  76 B. Therefore, the guide portion  44  can pass between the pair of the stoppers  126  while the guide portion  44  is in contact with the pair of stoppers  126 , and the ink cartridge  30  is removed from the cartridge installation portion  110 . 
     Fourth Modification 
     As shown in  FIG. 16 , a cartridge installation portion  110 A may not be provided with the holding mechanism  144 . Still however, the ink cartridge  30  can be held at the installed position because of the provision of the leaf spring  90  (engagement portion). 
     While the invention has been described in detail with reference to the embodiments thereof, it would be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention.