Abstract:
A carriage for an ink cartridge of an image forming apparatus employing an improved locking structure that draws out the ink cartridge with a simple unlocking thereof, thereby improving a user convenience in replacing the ink cartridge. The carriage for the ink cartridge of the ink jet printer has: a carriage body with a mounting portion, in which the ink cartridge is accommodated; a latch rotatably disposed at the carriage body to open and close the mounting portion; a resilient latch member to resiliently bias the latch in an opening direction; and a locking unit to lock the latch to the carriage body, wherein when the latch is unlocked with respect to the carriage body, the locking unit rotates together with the latch, and draws out the ink cartridge from the mounting portion.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    This application claims the benefit of Korean Patent Application No. 2003-3430, filed Jan. 17, 2003, in the Korean Intellectual Property Office, and Korean Patent Application No. 2003-25233, filed Apr. 21, 2003, the disclosures of which are incorporated herein by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to an image forming apparatus, such as an ink jet printer, and more particularly, to a carriage for an ink cartridge of an ink jet printer having an improved latch system, which enables easy mounting and releasing of the ink cartridge.  
           [0004]    2. Description of the Related Art  
           [0005]    An ink jet printer ejects droplets of printing ink on a desired position to create a desired image on a paper. The printing ink is generally contained in an ink cartridge that is removably mounted in the ink jet printer. A structure of such a removable ink cartridge is disclosed in Japanese Publication No. 10-157162.  
           [0006]    [0006]FIG. 1 is a cross sectional view showing a carriage for an ink cartridge of a conventional image forming apparatus, such as an ink jet printer, in which reference numerals  10 ,  13 ,  15 , and  20  indicate a carriage, a guide rod, a snap hook, and a locking lever, respectively.  
           [0007]    The carriage  10  is provided with a nozzle unit  12  in a carriage body  11 , and the carriage  10  accommodates an ink cartridge  14  in connection with the nozzle unit  12 . The carriage  10  reciprocally moves along the guide rod  13 , and the ink cartridge  14  is secured in position as the snap hook  15  is hooked into the locking lever  20 .  
           [0008]    The carriage body  11  includes a shaft supporting portion  11   a , on which the locking lever  20  is hinged, and an opening  11   b , which allows the ink cartridge  14  to be removed from the carriage  10 .  
           [0009]    The locking lever  20  includes a rotary shaft  21 , a cover plate  22 , and a knob  23 , and is secured to the carriage body  11  by the snap hook  15 .  
           [0010]    The rotary shaft  21  includes the shaft supporting portion  11   a  of the carriage body  11 . The locking lever  20  pivots on the rotary shaft  21 .  
           [0011]    The cover plate  22  protects the ink cartridge  14  accommodated in the carriage body  11 , and has protrusions  26  positioned on center portions of the cover plate  22 . The protrusions  26  function to compress the ink cartridge  14  to lock the ink cartridge in the carriage  10 .  
           [0012]    The cover plate  22  is provided with a window  24  positioned thereon. The window  24  is sized to allow a pole type head  15   b  of the snap hook  15  to be inserted when the locking lever  20  is completely pivoted to a locking position.  
           [0013]    The snap hook  15  includes a cantilever  15   a  and the pole type head  15   b.    
           [0014]    The cantilever  15   a  deforms as the locking lever  20  moves to the locking position, and then snaps back to a non-stress state after the locking lever  20  reaches the locking position.  
           [0015]    The pole type head  15   b  passes through the window  24 , and is held by the knob  23 , thereby locking the locking lever  20 .  
           [0016]    The knob  23  has a sliding slant  25  so that the pole-shaped head  15   b  of the snap hook  15  smoothly locks onto the knob  23 .  
           [0017]    In the carriage  10  constructed as above, to remove the ink cartridge  14 , the cantilever  15   a  is first pushed in a direction “A”. Accordingly, the pole type head  15   b  is released through the window  24 . The locking lever  20  is pivoted through a predetermined range by a recovering force of a pressure occurring when the protrusions  26  press the ink cartridge  14 , to thus be released from the locking position. A user then opens the locking lever  20  to a full extent with her/his hands to replace the ink cartridge  14  with a new one.  
           [0018]    But since such a locking device including the locking lever  20  mainly uses a resilient member such as the snap hook  15 , a problem occurs if the resilient force is decreased or if the resilient member deforms due to repeated use. In this case, the ink cartridge  14  is not locked in the carriage  10  securely, and frequently unlocks as external shocks are applied.  
           [0019]    Further, to remove the ink cartridge  14 , a user is required to press the snap hook  15 , manually pivot the locking lever  20 , and then remove the ink cartridge  14  uprightly. Thus, the user experiences inconvenience, and an ink cartridge locking device that has an improved locking force and provides user convenience has been demanded.  
         SUMMARY OF THE INVENTION  
         [0020]    The present invention has been developed to solve the above and/or other problems in the related art. Accordingly, an aspect of the present invention provides a carriage for an ink cartridge of an image forming apparatus such as an ink jet printer, employing an improved locking structure, which guarantees a secure locking.  
           [0021]    Another aspect of the present invention provides a carriage for an ink cartridge of an image forming apparatus such as an ink jet printer, in which the ink cartridge is drawn out with a simple unlocking thereof, thereby improving a user convenience in replacing the ink cartridge.  
           [0022]    To achieve the above and/or other aspects, a carriage for an ink cartridge of an image forming apparatus is provided, and has: a carriage body with a mounting portion, in which the ink cartridge is accommodated, a latch rotatably disposed at the carriage body to open and close the mounting portion, a resilient latch member to resiliently bias the latch in an opening direction, and a locking unit to lock the latch to the carriage body, wherein when the latch is unlocked with respect to the carriage body, the locking unit rotates together with the latch, and draws out the ink cartridge from the mounting portion.  
           [0023]    According to one aspect, the locking unit comprises: a locking projection disposed at a first wall of the carriage body, a hook member, hinged on the latch to be selectively hooked with the locking projection, that when the latch is released, the hook member hooks with the ink cartridge, and a release handle to release the hook member from the locking projection.  
           [0024]    According to one aspect, the hook member comprises: an ascending protrusion that hooks with the ink cartridge to lift the ink cartridge when the latch is released.  
           [0025]    According to one aspect, a pair of the hook members is disposed on opposing walls of the carriage body, with the ink cartridge being selectively interposed therebetween.  
           [0026]    According to one aspect, the release handle is disposed at the latch coaxially with the hook member. According to another aspect, the release handle is disposed at the latch on a different axis than the hook member.  
           [0027]    According to one aspect, the locking unit further comprises a resilient release handle member interposed between the release handle and the hook member, to resiliently compress the hook member to closely contact the locking projection.  
           [0028]    According to one aspect, the hook member, the locking projection and the ascending protrusion are respectively provided with sliding slants, and when a user presses an upper surface of the latch, the sliding slants on the hook member and the locking projection slide on each other to lock the latch.  
           [0029]    To achieve the above and/or other aspects, a carriage for an ink cartridge of an image forming apparatus is provided, which comprises: a carriage body with a mounting portion, in which the ink cartridge having a latching portion is accommodated, a latch rotatably disposed at the carriage body to close the mounting portion by locking, that when unlocking with respect to the carriage body, draws the ink cartridge out of the mounting portion, a resilient latch member to resiliently bias the latch in an opening direction, and a locking unit to lock the latch to the carriage body.  
           [0030]    According to one aspect, the latch comprises a latch body, and a guide arm extended from the latch body to guide both side surfaces of the ink cartridge. According to one aspect, the guide arm comprises a first guide portion that hooks into the latching portion to lift the ink cartridge, when the latch is unlocked, and a second guide portion extended stepwise from the first guide portion to guide a side of the latching portion.  
           [0031]    According to one aspect, the locking unit comprises a locking projection disposed at a sidewall of the carriage body, a hook member hinged on the latch and selectively hooked into the locking projection, and a release handle to release the hook member from the locking projection.  
           [0032]    According to one aspect, the carriage further comprises a sliding unit that limits an opening angle of the latch with respect to the carriage body.  
           [0033]    According to one aspect, the sliding unit comprises a sliding protrusion disposed on the latch; and a sliding hole portion disposed on the carriage body opposite to the sliding protrusion, to accommodate the sliding protrusion.  
           [0034]    According to one aspect, the sliding hole portion comprises a first penetrating hole receiving the sliding protrusion at a first position when the latch is locked, a second penetrating hole receiving the sliding protrusion at a second position when the latch is opened, and a connection portion connecting the first and the second penetrating holes.  
           [0035]    According to one aspect, the connection portion has a distance defined between opposing surfaces thereof that is smaller than a diameter of the sliding protrusion.  
           [0036]    According to one aspect, a first imaginary line, which is parallel to an upper surface of the latch in a locked position, and a second imaginary line, which is parallel to the upper surface of the latch in an opened position, form an interior angle ranging from about 20° to about 30°. According to one aspect, the interior angle is approximately 21°.  
           [0037]    Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0038]    The above/or and other aspects, features, and advantages of the present invention will be more apparent from the following detailed description of the embodiments, taken in conjunction with the accompanying drawings, in which:  
         [0039]    [0039]FIG. 1 is a cross sectional view showing a conventional carriage for an ink cartridge;  
         [0040]    [0040]FIG. 2 is a perspective view showing a carriage for an ink cartridge according to a first embodiment of the present invention;  
         [0041]    [0041]FIG. 3 is a side elevation view of FIG. 2;  
         [0042]    [0042]FIG. 4 is a perspective view showing the carriage for the ink cartridge of FIG. 2, with the latch being released open;  
         [0043]    [0043]FIG. 5 is a front view showing main parts of FIG. 4;  
         [0044]    [0044]FIG. 6 is a side elevation view of FIG. 4;  
         [0045]    [0045]FIG. 7 is a side elevation view showing the carriage for the ink cartridge of FIG. 2 with the latch being locked;  
         [0046]    [0046]FIG. 8 is a perspective view showing a carriage for an ink cartridge according to a second embodiment of the present invention;  
         [0047]    [0047]FIG. 9 is a side elevation view of FIG. 8 to explain an unlocking method of the latch;  
         [0048]    [0048]FIG. 10A is a left side elevation view of FIG. 8 showing an ascending latch hooking the ink cartridge;  
         [0049]    [0049]FIG. 10B is an enlarged view showing main parts of FIG. 10A;  
         [0050]    [0050]FIG. 11 is a perspective view showing the carriage of FIG. 8 with the latch being released open;  
         [0051]    [0051]FIG. 12 is a front view showing main parts of FIG. 11;  
         [0052]    [0052]FIG. 13 is a perspective view showing the ink cartridge before the ink cartridge is mounted in the carriage of FIG. 8; and  
         [0053]    [0053]FIG. 14 is a side elevation view showing the carriage for the ink cartridge of FIG. 8 with the latch being locked. 
     
    
     DETAILED DESCRIPTION  
       [0054]    Reference will now made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments described below explain the present invention by referring to the figures.  
         [0055]    Referring to FIGS. 2 through 7 showing a first embodiment according to the present invention, there are provided an ink cartridge  110 , a guide rail  120 , and a carriage  130 . The carriage body  131  reciprocally moves along the guide rail  120 .  
         [0056]    The carriage  130  includes a carriage body  131 , a latch  132 , a resilient latch member  133 , and a locking unit  200 . The carriage body  131  is provided with a mounting portion  134  on which the ink cartridge  110  is mounted.  
         [0057]    The latch  132  is pivotably disposed at the carriage body  131  to open and close an open portion of the carriage body  131 , through which the ink cartridge  110  is mounted, and removed.  
         [0058]    Meanwhile, on a surface of the latch  132  opposite to the ink cartridge  110 , there is provided a plunger  135 , with a spring  136  interposed between the surface of the latch  132  and the plunger  135 . As the latch  132  is locked, the plunger  135  compresses the ink cartridge  110  using a resilient force of the spring  136  to secure a head of the ink cartridge  110  in a mounted position.  
         [0059]    The resilient member  133  resiliently biases the latch  132  in an opening direction. Due to the presence of the resilient member  133 , the opening of the latch  132  is easily performed.  
         [0060]    The locking unit  200  locks the latch  132  in a closed position, and includes a hook member  210 , a release handle  220 , and a locking projection  230 .  
         [0061]    The hook member  210  is pivotably disposed at the latch  132 , and has a locking protrusion  211  locked in the locking projection  230  and an ascending protrusion  212  positioned on a surface of the hook member  210 , opposite to the ink cartridge  110 .  
         [0062]    The ascending protrusion  212  (see FIG. 5) hooks into a latching portion  111  disposed at an upper portion of the ink cartridge  110 , when the latch  132  is opened by the release handle  220 . Accordingly, the ink cartridge  110  is lifted up by the ascending protrusion  212 , and is separated from the carriage body  131 .  
         [0063]    According to one aspect, a pair of hook members  210  are provided, with the ink cartridge interposed therebetween. Accordingly, the ascending protrusions  212  support the latching portions  111  at opposing sides of the ink cartridge  110 , to thereby prevent the ink cartridge  110  from deviating from a predetermined path while being removed.  
         [0064]    The release handle  220  pivots the hook member  210  in an unlocking direction, and according to one aspect, the release handle  220  is hinged on the latch  132 , where the hook member  210  is disposed, so that the release handle  220  pivots on the same rotary shaft as the hook member  210 . In this case, together with the lifting of the release handle  220  in an arrowed direction of FIG. 3, the hook member  210  is concurrently rotated and released from the locking projection  230 .  
         [0065]    According to one aspect, the release handle  220  is further provided with a resilient release handle member  221  to bias the hook member  210  toward the locking projection  230 . According to one aspect, the resilient release handle member  221  comprises a spring mounted on an axis of rotation of the release handle  220 . When the release handle  220 , including the resilient release handle member  221 , is no longer controlled by a user, the release handler  220  automatically returns to an initial position, and as a result, user convenience is improved.  
         [0066]    The locking projection  230  is disposed at a sidewall of the carriage body  131  to engage the hook member  210 .  
         [0067]    As shown in FIGS.  2  to  7 , according to one aspect, the locking projection  230 , the locking protrusion  211 , and the ascending protrusion  212  of the hook member  210 , respectively, have sliding slants. Due to the presence of the sliding slants, the hook member  210  is easily hooked into the locking projection  230  in the locking of the latch  132  and requires less effort from a user than the conventional inkjet carriage. Also, if the release handle  220  is not controlled by the user in an opening direction of the latch  132 , the locking state is maintained.  
         [0068]    Reference will now be made to the operation of mounting and removing the ink cartridge from the carriage  130 , with reference to the accompanying drawings.  
         [0069]    Referring to FIGS. 2 and 3, the ink cartridge  110  is received in the mounting portion  134  of the carriage body  131 , and secured therein by the locking unit  200 .  
         [0070]    When the ink cartridge  110  is completely consumed, and thus has to be replaced with a new one, a user presses the latch  132  with his/her thumb and lifts up the release handle  220  in the arrowed direction of FIG. 3 with his/her index finger or middle finger. As the release handle  220  is lifted, the hook member  210  assembled with a hinge portion of the latch  132  together with the release handle  220  is concurrently rotated in an unlocking direction, i.e., in the arrowed direction of FIG. 3.  
         [0071]    Accordingly, as the hook member  210  engaged with the locking projection  230  for a locking state is rotated in the unlocking direction, the latch  132  releases from the locking state, and as shown in FIG. 4, the latch  132  receives a rotation force in the opening direction due to the resilient recovering force of the resilient latch member  133  and the spring  136 .  
         [0072]    Accordingly, the latch  132  released from the locking state is opened to a maximum extent by the user, as shown in FIGS.  4  to  6 , to allow the ink cartridge  110  to be removed in an arrowed direction of FIG. 6.  
         [0073]    As is also shown in FIGS. 5 and 6, the ascending protrusion  212 , which protrudes out of the surface of the locking member  210  opposite to the ink cartridge  110 , pivots in conjunction with the opening of the latch  132 , as the latch  132  is opened by a user.  
         [0074]    According to one aspect, the latching portion  111  is positioned along an external perimeter of the ink cartridge  110 . The ascending protrusion  212  pivots while the latching portion  111  engages the ascending protrusion  212 , thereby raising the ink cartridge  110  into a position to be removed from the mounting portion  134 . According to one aspect, the latching portion  111  is positioned along an upper and outer perimeter of the ink cartridge  110 . This is to maximize a moment applied by the ascending protrusion  212 , to enable the user to remove the ink cartridge  110  with less effort.  
         [0075]    Accordingly, when a user rotates the latch  132  and opens the carriage body  131 , the ink cartridge  110  can be easily removed from the mounting portion  134  of the carriage  130  due to the presence of the ascending protrusion  212 .  
         [0076]    After the used ink cartridge  110  is removed, a new ink cartridge  110  full of ink is mounted in the carriage  130 . That is, as shown in FIG. 7, the ink cartridge  110  is placed in the mounting portion  134  of the carriage  130 . Then, the latch  132  is rotated in the locking direction, opposite the unlocking direction, and is then pressed by the user in an arrowed direction of FIG. 7. The hook member  210  slides on the sliding slant of a contact surface contacting with the locking projection  230 , and then engages the locking projection  230 , to accomplish the locking.  
         [0077]    At this point, since the ascending protrusion  212  positioned on the surface of the hook member  210  opposite to the ink cartridge  110  also includes the sliding slant, as shown in FIG. 5, the ascending protrusion  212  slides on the latching portion  111  positioned along the external perimeter of the ink cartridge  110 , so that the hook member  210  is engaged with the locking projection  230 . Also, the plunger  135  provided on the latch  132  resiliently compresses the ink cartridge  110 , thereby firmly securing the ink cartridge  110  to the mounting portion  134  of the carriage  130 .  
         [0078]    Reference will now be made to the carriage for the ink cartridge according to a second embodiment of the present invention with reference to the accompanying drawings.  
         [0079]    Referring to FIGS. 8 and 9, according to the second embodiment, there is provided an ink cartridge  510 , a guide rail  520 , and a carriage  530 .  
         [0080]    The ink cartridge  510 , which discharges ink contained in a body thereof through a nozzle disposed at a lower surface of the ink cartridge  510  according to a print signal of a controller, has a latching portion  511  positioned along an upper and outer circumference of the ink cartridge  510 , to allow the ink cartridge  510  to be easily mounted and removed. This is to maximize a moment force applied by a guide arm  532   b  during removal of the ink cartridge  510 , thereby enabling a user remove the ink cartridge  510  with less effort.  
         [0081]    The guide rail  520  is disposed in a body of the ink jet printer, to support the carriage  530  and guide a printing path.  
         [0082]    The carriage  530  includes a carriage body  531 , a latch  532 , a resilient latch member  533 , and a locking unit  600 . The carriage body  531  is provided with a mounting portion  534  to accommodate the ink cartridge  510  thereon, and reciprocally moves along the guide rail  520 .  
         [0083]    The latch  532  is pivotably disposed at the carriage body  531 , to open and close an opening portion of the carriage body  531 , through which the ink cartridge  510  is mounted and removed. The latch  532  draws out and separates the ink cartridge  510  from the mounting portion  534  during an opening operation.  
         [0084]    The latch  532  includes a latch body  532   a , and the guide arm  532   b  extending from the latch body  532   a , to guide side surfaces of the ink cartridge  510 . According to one aspect, the guide arm  532   b  includes: a first guide portion  532   b ′ that hooks into the latching portion  511  during the opening operation, to lift up the ink cartridge  510 ; and a second guide portion  532   b ″ extending stepwise from the first guide portion  532   b ′, to guide the latching portion  511 .  
         [0085]    The first and the second guide portions  532   b ′ and  532   b ″, respectively, have inclined surfaces, each setting an angle to the horizontal when the latch  532  is locked with an inclination having an upward tendency relative to an advancing direction of the ink cartridge  510 . That is, the guide arm  532   b  having the first and the second guide portions  532   b ′ and  532   b ″, is shaped in an arc having a predetermined curvature, so that the ink cartridge  510  advances toward a lower surface of the carriage. Due to the guide arm  532   b  having the predetermined curvature, an area where an upper surface of the first guide portion  532   b ′ contacts with a lower surface  511 ′ (see FIG. 12) of the latching portion  511  increases as the latch  532  is opened. Also, since the guide arm  532   b  contacts the ink cartridge  510  at a position that is in front of a center of gravity of the ink cartridge  510 , a user removes the ink cartridge  510  with less effort.  
         [0086]    On a surface of the latch  532  opposite to the ink cartridge  510 , there is provided a plunger  535  integrally formed with the latch body  532   a . As the latch  532  is locked, the plunger  535  elastically deforms to compress the ink cartridge  510  and secure a head of the ink cartridge  510  mounted in the carriage  532 .  
         [0087]    The resilient latch member  533  resiliently biases the latch  532  in an opening direction. Due to the presence of the resilient latch member  533 , the opening of the latch  532  is easily performed.  
         [0088]    The locking unit  600  locks the latch  532  in a closed position, and includes a hook member  610 , a release handle  620  and a locking projection  630 . The hook member  610  is pivotably disposed at the latch  532  and has a locking protrusion  611  (not shown—similar to locking protrusion  211  of FIG. 3) that locks the locking projection  630 .  
         [0089]    According to one aspect, a pair of opposite hook members  610  are provided with the ink cartridge  510  interposed therebetween. Accordingly, the pair of hook members  610  simultaneously hook into the locking projections  630  at both sides, to prevent the latch  532  from deviating from a predetermined position while being opened or locked.  
         [0090]    The release handle  620  pivots the hook member  610  in an unlocking direction, and according to one aspect, is integrally formed with the hook member  610 , and pivotably hinged on the latch  532 . In this case, the hook member  610  extends from the release handle  620 , and is concurrently rotated and released from the locking projection  630  simultaneously with the lifting of the release handle  620  in an arrowed direction of FIG. 9. According to one aspect, however, the release handle  620  and the hook member  610  are separately formed. In this case, the hook member  610  and the release handle  620  are connected to each other and move in association with each other.  
         [0091]    Also, the release handler  620  may be further provided with a resilient release handle member  621  to ensure a close contact between the hook member  610  and the locking projection  630 . The resilient release handle member  621  uses a spring that is interposed between the latch  532  and the release handle  620  as shown in FIG. 8. When the release handle  620 , including the resilient release handle member  621 , is no longer controlled by a user, the release handler  620  automatically returns to an initial locked position, and as a result, user convenience is improved.  
         [0092]    According to one aspect, the locking projection  630  is disposed at a sidewall of the carriage body  531  to engage the locking protrusion  611 .  
         [0093]    As shown in FIGS.  8  to  14 , the locking projection  630  and the hook member  610  respectively, have sliding slants. The sliding slants are positioned so that the respective contacting surfaces of the hook member  610  and the locking projection  630  slide on each other when the latch  532  is locked.  
         [0094]    Meanwhile, as shown in FIGS. 10A and 10B, a sliding unit  300  is provided at the carriage body  531  and the latch  532 , to limit an opening angle S of the latch  532 .  
         [0095]    The sliding unit  300  includes a sliding protrusion  310  disposed at the latch  532 , and a sliding hole portion  0 . 320  disposed in the carriage body  531 , that corresponds to the sliding protrusion  310 . According to one aspect, the sliding protrusion  310  is a cylinder that protrudes from the latch body  532   a.    
         [0096]    The sliding hole portion  320  is defined in the carriage body  531  to correspond to the sliding protrusion  310 . The sliding hole portion  320  includes a first penetrating hole  321 , a second penetrating hole  322 , and a connection portion  323  connecting the first and the second penetrating holes  321  and  322 . The sliding protrusion  310  is received in the first penetrating hole  321  at a first position when the latch  532  is locked. And the sliding protrusion  310  is received in the second penetrating hole  322  at a second position when the latch  532  is opened to the maximum degree.  
         [0097]    According to one aspect, the first and the second penetrating holes  321  and  322  have the same diameter. According to another aspect, the first penetrating hole  321  has a greater diameter than that of the second penetrating hole  322 , to achieve a smooth locking of the latch  532 .  
         [0098]    The connection portion  323  has a distance “d” between opposing surfaces thereof, which is smaller than a diameter “D” of the sliding protrusion  310 . If the distance “d” of the connection portion  323  is too small, the sliding protrusion  310  cannot slide toward the second penetrating hole  322 . In this case, the latch  532  would not open. On the contrary, if the distance “d” of the connection portion  323  is too large, the sliding protrusion  310  is not supported by the connection portion  323  in the second penetrating hole  322  when the latch  532  is opened. In this case, the latch  532  is unstably opened, and thus, when the latch  532  is no longer controlled by a user, the latch  532  returns to the initial locking position due to self-weight. Thus, according to one aspect, it is preferred that the distance “d” of the connection portion  232  corresponds to 80%˜90% of the diameter “D” of the sliding protrusion  310 .  
         [0099]    Accordingly, when the latch  532  is opened, since the sliding protrusion  310  is received in the second penetrating hole  322  of the carriage body  531  and also supported in the connection portion  323 , the opening state of the latch  532  is stably maintained, to thus open the mounting portion  534 .  
         [0100]    Also, the sliding unit  300  restricts the opening angle “S” of the latch  532 . According to one aspect, the opening angle “S”, which is an interior angle between a first imaginary line “a” parallel to an upper surface of the latch  532  at the locking position, and a second imaginary line “b” parallel to the upper surface of the latch  532  at a maximum opening position, is within a range of approximately 20° to 30° (see FIG. 14). If the opening angle “S” is greater than the range, then, when a user inserts the ink cartridge, the latching portion  511  does not contact the upper surface of the first guide portion  532   b ′, but rather, advances under the first guide portion  532   b ′, so that the ink cartridge  510  is not locked. Also, if the opening angle “S” is less than the range, it is difficult for a user to insert and remove the ink cartridge. According to one aspect, the opening angle “S” is approximately 21°.  
         [0101]    Therefore, the sliding unit  300  maintains the latch  532  at the opening angle “S” of 21°, thereby minimizing an error that may otherwise occur when the ink cartridge  510  is replaced with a new ink cartridge.  
         [0102]    Reference will now be made to the operations of inserting and removing the ink cartridge  510 , with reference to the accompanying drawings.  
         [0103]    Referring to FIGS. 8 and 9, the ink cartridge  510  is accommodated in the mounting portion  534  provided in the carriage body  531  of the carriage  530 , and secured by the locking unit  600 .  
         [0104]    When the ink cartridge  510  is completely consumed and thus has to be replaced with a new ink cartridge  510 , a user presses the latch  532  with his/her thumb and lifts the release handle  620  in the arrowed direction of FIG. 9 with his/her index finger or middle finger.  
         [0105]    As the release handle  620  is lifted, rotation of the release handle  620  causes the hook member  610  to rotate in an unlocking direction i.e. in the arrowed direction of FIG. 9.  
         [0106]    Accordingly, as the hook member  610 , engaged with the locking projection  630  during a locking state, is rotated in the arrowed direction of FIG. 9, the latch  532  is released from the locking state, as shown in FIG. 10A, and the latch  532  receives a rotation force in the opening direction due to the resilient recovering force of the resilient latch member  533  and the plunger  535 .  
         [0107]    The latch  532  released from the locking state is opened to the maximum degree by the user as shown in FIGS. 11 and 12, to remove the ink cartridge  510  in an arrowed direction of FIG. 11.  
         [0108]    As shown in the drawings, the latch  532  is provided with the guide arms  532   b  positioned at opposing sides to support the ink cartridge  510 . Each guide arm  532   b  includes the first guide portion  532   b ′ supporting the latching portion  511  of the ink cartridge  510 , and the second guide portion  532   b ″ supporting a side surface of the latching portion  511 .  
         [0109]    Accordingly, when the latch  532  is opened, the ink cartridge  510  comes into contact with the guide arms  532   b , and is separated from the mounting portion  534  in a manner such that the lower surface  511 ′ of the latching portion  511 , which protrudes from an upper surface of the ink cartridge  510 , slides in contact with an upper surface of the first guide portion  532   b ′. That is, the ink cartridge  510  is drawn out of the mounting portion  534  in association with the ascending movement of the guide arm  532   b.    
         [0110]    The sliding unit  300  limits the opening angle “S” of the latch  532  to approximately 21°, and thus the latch  532  is supported by the connection portion  323  at the maximum opening position and stops opening. When the latch  532  reaches the maximum opening position, the sliding protrusion  310  protruding from the latch body  532   a  slides into the second penetrating hole  322  of the sliding hole portion  320 . Since the distance “d” of the connection portion  323  is smaller than the diameter “D” of the second penetrating hole  322 , the sliding protrusion  310  is supported by a wall surface of the connection portion  323  at an entrance of the connection portion  323 . Accordingly, the latch  532  is fixed at the maximum opening position.  
         [0111]    When the ink cartridge  510  is separated from the mounting portion  534 , a user removes the ink cartridge  510  in the arrowed direction of FIG. 11. Then, the user inserts a new ink cartridge  510  in a manner such that the upper surface of the first guide portion  532   b ′ contacts with the lower surface  511 ′ of the latching portion  511 . The inserting movement of the ink cartridge  510  continues until a projection  512  comes into contact with the plunger  535 . If the insertion is not complete, the latch  532  does not lock the ink cartridge  510  properly.  
         [0112]    When the inserting of the ink cartridge  510  is complete, a user presses an upper surface of the latch  532  in an arrowed direction of B as shown in FIG. 14, and mounts the ink cartridge  510  in the mounting portion  534 . The hook member  610  and the locking projection  630  have the sliding slants on the opposing surfaces thereof. Accordingly, the hook member  610  slides on the sliding slant of the locking projection  630 , and rotates together with the release handle  620  in contact with the sliding slant by a predetermined angle. Thereafter, the hook member  610  returns to the locking position by a resilient recovering force of the resilient release handle member  621 , and hooks the locking projection  630 .  
         [0113]    Also, the plunger  535  provided on the latch  532  resiliently compresses the projection  512  disposed on the upper surface of the ink cartridge  510 , thereby firmly securing the ink cartridge  510  to the mounting portion  534  of the carriage  530 .  
         [0114]    Accordingly, in case that there occurs an external shock to the ink jet printer, the carriage  530  having the locking device as described above provides a stable locking of the ink cartridge  510 . Also, since the user can easily install and remove the ink cartridge  510  precisely, improper operation of the printer is prevented, and the user convenience is improved.  
         [0115]    Further, since there is the hook member  610  pivotably disposed at the latch  532  to hook the locking projection  630 , the ink cartridge is prevented from being separated from the carriage  530  by the external shock. Also, since the ink cartridge  510  is guided to the mounting position without deviation, due to the presence of the guide arm  532   b  formed integrally with the latch  532 , mistakes occur less frequently when the user replace the ink cartridge  510  with a new ink cartridge  510 .  
         [0116]    Also, since the latch  532  is maintained in an open state until the ink cartridge  510  is re-mounted, the user is not required to open the latch again to mount the ink cartridge  510 . Accordingly, the user convenience is improved.  
         [0117]    Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.