Abstract:
A casing body of an ink cartridge includes a first chamber allowing atmospheric air to enter therein, and a second chamber that stores ink. A lid within the second chamber moves vertically while partitioning the second chamber into a first space above the lid and a second space below the lid for storing ink. A gap between an outer periphery of the lid and an inner periphery of the second chamber allows a meniscus of ink to form therebetween. A partition is provided at an upper end of the second chamber to partition the first and second chambers. The partition includes a through hole at a portion which is away from the inner periphery of the second chamber, to allow the atmospheric air to enter the second chamber. An elastic member in the second chamber urges the lid upwards to maintain the second space of the second chamber at a negative pressure.

Description:
BACKGROUND OF THE INVENTION 
   The present invention claims foreign priority under 35 USC 119 based on Japanese Patent Application No. 2002-358386, filed Dec. 10, 2002, the contents of which are incorporated herein by reference. 
   The present invention relates to an ink cartridge having a plurality of ink chambers, each ink chamber having a movable member that descends with ink consumption. The invention also relates to an ink jet printer incorporating such an ink cartridge as an ink supply source. 
   In the related art ink cartridge for an ink jet printer, a bag-type related art ink tank is constructed such that a flexible ink bag filled with ink is in a rigid plastic case. Alternatively, a foam-type ink tank is constructed such that ink-absorbent foam or felt is in a rigid plastic case. 
   However, related art ink tanks have various problems and disadvantages. For example, but not by way of limitation, the efficiency of drawing ink from the bag and the foam or felt is poor. Also, the filling efficiency of the ink is low. As a result, it is difficult to reduce the size of the ink tank. Further, the bag-type ink tank has a probability of ink leakage due to poor sealing of the ink bag. 
   Additionally, the ink bag can break, such that ink leaks out of the bag when the ink bag and the plastic case containing the ink bag rub during transport. Related art attempts to prevent the rubbing and the bag breakage have included increasing the rigidity and strength of the flexible material forming the ink bag. However, in this modified related art ink bag, a negative pressure for supplying ink increases, and various problems arise. For example, but not by way of limitation, the amount of consumed ink increases, and the amount of residual ink varies. 
   Also, in the related art foam-type ink tank, foreign materials may enter the ink supplied from the foam. The foreign materials enter the ink and flow into the print head, thereby causing clogging of the printer head. 
     FIG. 7  shows a related art ink cartridge  100 . Four ink chambers  102 ( 1 ) to  102 ( 4 ) are disposed side by side, with their upper ends open within a case  101 . An L-shaped waste ink chamber  110  extends from the upper parts of those ink chambers to the side parts thereof. 
   The ink chambers  102 ( 1 ) to  102 ( 4 ) respectively include lids  103 ( 1 ) to  103 ( 4 ), which are vertically movable along the inner peripheral surfaces  102   a  of those chambers. Ink outlets  104 ( 1 ) to  104 ( 4 ) are formed in the bottom surfaces of the four ink chambers  102 ( 1 ) to  102 ( 4 ). Ink reservoirs  105  are respectively formed by bottom surfaces  102   b  and the inner peripheral surfaces  102   a  of the ink chambers, and the movable lids  103 ( 1 ) to  103 ( 4 ). 
   The movable lids  103 ( 1 ) to  103 ( 4 ) are urged by spring members  106  in an upward direction. As a result, the ink reservoirs  105  experience negative pressure. The strength of an ink meniscus formed in a gap between each inner peripheral surface  102   a  and an associated one of those movable lids  103 ( 1 ) to  103 ( 4 ) is selected such that the ink meniscus is not broken by an ink suction force of the print head, which exerts pressure on the ink outlet. 
   The foregoing related art ink cartridge  100  may be used for a multi-color ink cartridge, in which different colors of ink are stored in the four ink chambers  102 ( 1 ) to  102 ( 4 ). 
   However, each of the movable lids  103 ( 1 ) to  103 ( 4 ) is held within an associated one of the ink chambers  102 ( 1 ) to  102 ( 4 ) by the ink meniscus formed in a gap between the inner peripheral surface  102   a  of the ink chamber and the outer peripheral surface of the movable lid to form the ink reservoir  105  in the lower side of the movable lid. Thus, the ink meniscus may break when impact is applied to the ink cartridge  100 , so that ink leaks to the upper side of the movable lid (i.e., the side closer to the waste ink chamber  110 ). 
   When the ink leaks to the upper side of the movable lid, the leaked ink from the respective ink reservoirs  105  may mix with ink from other reservoirs. Then, the mixed ink may return to the respective ink reservoirs  105 . In addition, since the waste ink chamber  110  is filled with an ink absorbing member of foam or felt, fine particles contained in the ink absorbing member may mix with the leaked ink and enter the ink reservoirs  105 . 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to overcome at least the foregoing related art problems, as well as other problems well-known to those skilled in the art. However, the present invention is not required to be directed to solving any of the aforementioned related art problems. 
   It is therefore an object of the invention to provide an ink cartridge capable of preventing foreign materials from entering ink reservoirs, and avoiding mixture of ink leaked from the other ink reservoirs. 
   It is also an object of the invention to provide an ink jet printer incorporating such an ink cartridge as an ink supply source. 
   To achieve at least the above objects, according to an exemplary, non-limiting embodiment of the present invention, an ink cartridge is provided, comprising: 
   a casing body, including a first chamber, allowing atmospheric air to enter therein, and a second chamber storing ink therein; 
   a lid member, disposed within the second chamber movably in a vertical direction, while partitioning the second chamber into a first space above the lid member and a second space below the lid member for storing ink, the lid member configured such that a gap is formed between an outer periphery of the lid member and an inner periphery of the second chamber such that a meniscus of ink is formed therebetween; 
   a partition member, which partitions the first chamber from the second chamber, the partition member provided at an upper end of the second chamber, and having a through hole formed at a portion which is away from the inner periphery of the second chamber, the through hole allowing the atmospheric air to enter the second chamber; and 
   an elastic member, disposed in the second chamber to urge the lid member upwards so as to maintain the second space of the second chamber at a negative pressure. 
   In such a configuration, since the first chamber communicating with the atmosphere is partitioned from the second chamber, ink leaked from the second space of the second chamber via the outer periphery of the lid member hardly flows to an exterior of the ink cartridge via the first chamber. 
   This configuration is applicable to a multi-color ink cartridge in which a plurality of second chambers for storing plural colors of ink are provided. In such a case, even if one color of ink is leaked to the first space of the second chamber, the ink will not mix with another color of ink. Accordingly, troubles due to ink mixture can be avoided when the leaked ink returns to the second space of the second chamber. 
   Preferably, the ink cartridge further comprises a projection formed around the through hole so as to project from the partition member toward the first chamber. 
   In such a configuration, ink leaked to the first chamber will not return to the second chamber. Accordingly, it is possible to avoid problems and/or disadvantages caused by mixture of foreign matters with the leaked ink. 
   Preferably, the ink cartridge further comprises an ink absorber, disposed in the first chamber so as to surround an end of the through hole facing the first chamber. 
   In such a configuration, since ink leaked to the first chamber is absorbed by the ink absorber, at least the related art problems caused by the mixture of foreign matter with the leaked ink can be avoided. 
   Here, it is preferable that the ink absorber is positioned away from the end of the through hole. 
   If the ink absorber is in contact with the through hole, ink leaked to the first space of the second chamber may be sucked by the ink absorber. 
   According to the above configuration of the present invention, only the ink leaked to the first chamber is absorbed by the ink absorber, so that less ink is wasted. 
   Preferably, the ink cartridge further comprises a projection provided on at least one of a surface of the partition member facing the first space of the second chamber and an upper face of the lid member. 
   In such a configuration, since the lid member and the partition member are brought into substantially line contact with each other, adhesion of these members due to face contact therebetween is avoided. 
   Here, it is preferable that the projection is formed around the through hole so as to project from the partition member toward the second chamber. 
   Preferably, a dimension of an inner periphery of the second chamber is gradually reduced toward a lower end of the second chamber. 
   When the lid member closes to the lower end of the second chamber due to ink consumption, the urging force of the elastic member increases so that the meniscus formed in the gap between the outer periphery of the lid member and the inner periphery of the second chamber tends to be broken. However, according to the above configuration, the gap is narrowed in accordance with the ink consumption, so that the strength of the meniscus increases. Therefore, even when the air bubbles do not enter the second space of the second chamber. 
   Preferably, the ink cartridge further comprises: an inlet, connected to the first chamber and configured to supply waste ink to the first chamber; an outlet, connected to the second chamber at a lower end of the second chamber, through which the ink is supplied to an exterior of the ink cartridge; and a vent port, formed at a top portion of the ink cartridge to allow the atmospheric air to enter the first chamber. The first chamber communicates with the atmosphere at a top portion of the ink cartridge. 
   Preferably, the first chamber is an L-shaped space formed above and lateral to the at least one second chamber, for collection and storage of waste ink. 
   Preferably, the at least one second chamber comprises first through fourth supply chambers filled with black ink, cyan ink, magenta ink, and yellow ink, respectively. 
   According to the invention, there is also provided an ink jet printer, comprising: a print head; and the above ink cartridge, which supplies the ink from the second chamber to the print head. 
   Since the above ink cartridge is capable of preventing ink mixture invasion of foreign matter or air bubbles, nozzle clogging of the print head is avoided. Therefore, excellent quality of printing operation is secured. 
   Preferably, the ink jet printer further comprises: a platen for feeding a recording sheet in a sheet feeding direction, wherein a nozzle of the print head faces the platen; a carriage that reciprocatively moves the print head in a primary scanning direction; a cartridge holder that receives the ink cartridge and supplies ink to the print head via a nozzle; and a drive controller that controls operations of the ink jet printer. 
   Here, it is preferable that the cartridge holder includes an ink supply needle for removing ink from the second chamber, and an ink recovery needle that supplies a waste ink to the first chamber. 
   It is further preferable that the ink recovery needle receives the waste ink via a waste ink collecting passage from a nozzle cap by a pumping device positioned between the nozzle cap and the ink recovery needle. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above objects and advantages of the present invention will become more apparent by describing in detail exemplary, non-limiting embodiments thereof, with reference to the accompanying drawings, wherein: 
       FIG. 1  illustrates a configuration of an ink jet printer according to an exemplary, non-limiting embodiment of the present invention; 
       FIG. 2A  is a top plan view of an ink cartridge according to an exemplary, non-limiting embodiment of the invention; 
       FIG. 2B  is a side view of the ink cartridge according to an exemplary, non-limiting embodiment of the present invention; 
       FIGS. 2C and 2D  are side views of the ink cartridge according to an exemplary, non-limiting embodiment of the present invention; 
       FIG. 3  is a perspective view of the ink cartridge according to an exemplary, non-limiting embodiment of the present invention; 
       FIG. 4  is a perspective view of a disassembled state of the ink cartridge according to an exemplary, non-limiting embodiment of the present invention; 
       FIG. 5A  is a section view of the ink cartridge, taken along the line  5 A— 5 A in  FIG. 2A , according to an exemplary, non-limiting embodiment of the present invention; 
       FIG. 5B  is an enlarged view of a bottom portion of an ink chamber in the ink cartridge, according to an exemplary, non-limiting embodiment of the present invention; 
       FIG. 6A  is a perspective view of an upper side of a partition plate in the ink cartridge according to an exemplary, non-limiting embodiment of the present invention; 
       FIG. 6B  is a perspective view of a lower side of a partition plate in the ink cartridge according to an exemplary, non-limiting embodiment of the present invention; and 
       FIG. 7  is a section view of a related art ink cartridge. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Exemplary, non-limiting embodiments of the present invention will be described with reference to the accompanying drawings. 
     FIG. 1  schematically shows an ink jet printer according to an exemplary, non-limiting embodiment of the present invention. The ink jet printer  1  includes: a platen  3  for feeding a recording sheet  2  in a sheet feeding direction Y; a print head  4  having a nozzle face  4   a  facing the platen  3 ; a carriage  5  for reciprocatively moving the print head  4  in a primary scanning direction X; a cartridge holder  7  for receiving a multi-color ink cartridge  10  which supplies different colors of ink to the ink nozzles of the print head  4 ; and a drive controller  8  for controlling the driving operations of related components. 
   The ink cartridge  10  includes, for example but not by way of limitation, four independent ink chambers which contain, for example, black ink, cyan ink, yellow ink and magenta ink, and an waste ink chamber  14  for collecting waste ink (described later in detail). The cartridge holder  7  is provided with ink supplying needles  7 ( 1 ) to  7 ( 4 ) for removing ink from the ink chambers, and an ink recovery needle  7 ( 5 ) for supplying waste ink to the waste ink chamber  14 . When the ink cartridge  10  is attached to the cartridge holder  7 , ink supply passages are formed, which supply different colors of ink from the ink cartridge  10  to the print head  4 . 
   The ink jet printer  1  includes a nozzle cap  9  located apart from the platen  3  in the printing direction X. The nozzle cap  9  is connected to the ink recovery needle  7 ( 5 ), through a pump  6 . When the ink cartridge  10  is attached to the cartridge holder  7 , a waste ink collecting passage is formed ranging from the nozzle cap  9  to the waste ink chamber  14  in the ink cartridge  10 , via the ink recovery needle  7 ( 5 ). To collect waste ink from the print head  4 , the nozzle face  4   a  of the print head  4  is covered with the nozzle cap  9 . In this state, the ink pump  6  is driven. 
   As shown in  FIGS. 2A through 5B , the ink cartridge  10  includes: a cartridge case  12  having a laterally elongated box shape; four ink chambers  13 ( 1 ) to  13 ( 4 ); and a waste ink chamber  14 . The cartridge case  12  includes a case body  12   a  and a cover plate  12   b  that covers an opening of the top end of the case body  12   a . The cover plate  12   b  is a thin plate, and its reverse side is a substantially flat surface. Ink outlets  15 ( 1 ) to  15 ( 4 ) for taking out ink from the ink chambers  13 ( 1 ) to  13 ( 4 ), and an ink inlet  16  for supplying waste ink into the waste ink chamber  14 , are formed in a bottom plate  21  of the case body  12   a.    
   The respective portions of the ink cartridge  10  will be described in detail. As shown in  FIGS. 4 and 5A , the case body  12   a  of the cartridge case  12  is formed with the bottom plate  21  having the ink outlets  15 ( 1 ) to  15 ( 4 ) and the ink inlet  16 , opposed side walls  22  and  23  extending from the edges of the long sides of the bottom plate  21 , and opposed end portions  24  and  25  extending from the edges of the short sides of the bottom plate  21 . The end plate portion  25  is arcuate in shape, and smoothly continuous to the side walls  22 ,  23 . 
   Four ink chambers  13 ( 1 ) to  13 ( 4 ), each circular in cross section, are formed within the case body  12   a  of the cartridge case  12 . Those ink chambers are open at top ends, and partitioned by four partition walls  26  to  29 , each of which connects to both of the side walls  22 ,  23 . Top end openings  13   a  of the ink chambers  13 ( 1 ) to  13 ( 4 ) are sealingly closed with a partition plate  20  made of a plastic material, for example but not by way of limitation. 
     FIGS. 6A and 6B  are perspective views showing the partition plate  20  as viewed from top and bottom, respectively. Four annular projections  20   a  are provided on the lower surface of the partition plate  20 , while corresponding in position to circular edges  13   b  (see  FIG. 4 ) of the top end openings  13   a  of the ink chambers  13 ( 1 ) to  13 ( 4 ). The annular projections  20   a  are thermally fused onto the edges  13   b , so that the partition plate  20  is joined to the edges  13   b.    
   Tubular projections  20   c  are formed at the centers of the annular projections  20   a , and tubular projections  20   d  are formed on an upper surface  20   e  of the partition plate  20 , so as to correspond to the projections  20   c . Air holes  20   b  extend from upper ends of the projections  20   d  to lower ends of the projections  20   c  while penetrating through the partition plate  20  in its thickness direction. 
   As shown in  FIG. 5A , a space as an ink trap is elongated laterally between the partition plate  20  and the cover plate  12   b , and a space for collecting the waste ink is elongated vertically between the side wall  24  and the partition wall  26 , so that an L-shaped space is formed as the waste ink chamber  14 . An ink absorbing member  17 , such as foam or felt, is disposed in the waste ink chamber  14 . An air hole  12   d  is located at a position of the cover plate  12   b  laterally with respect to the ink chamber  13 ( 1 ). 
   Empty spaces  14   a , each being circular in cross section, in which the ink absorbing member  17  is not present, correspond to the air holes  20   b  of the partition plate  20 . By those empty spaces  14   a , the air holes  20   b  are spaced from the ink absorbing member  17 . 
   The ink chambers  13 ( 1 ) to  13 ( 4 ) are filled with black ink, cyan ink, magenta ink and yellow ink, respectively. Since the structure of those ink chambers  13 ( 1 ) to  13 ( 4 ) are the same, the structure of the ink chamber  13 ( 2 ) will be representatively described, and in describing the remaining ink chambers  13 ( 1 ),  13 ( 3 ) and  13 ( 4 ), like reference numerals are used for designating like elements. 
   The ink chamber  13 ( 2 ) includes a cylindrical container  31  defined by the bottom plate  21 , the side walls  22  and  23 , and the partition walls  27  and  28 . The upper end opening of the cylindrical container  31 , viz., the top end openings  13   a  of the ink chamber  13 ( 2 ), is sealed with the partition plate  20 . A coiled spring  34  and a movable lid  33  are inserted into the cylindrical container  31  through the top end openings  13   a  before the partition plate  20  is thermally fused to the cylindrical container. The movable lid  33  is upwardly urged by the coiled spring  34 . The ink outlet  15 ( 2 ) is formed at the central part of the bottom surface  31   b  of the cylindrical container  31 . 
   An ink reservoir  35  which reserves the ink is defined by the bottom surface  31   b , the inner peripheral surface  31   a , and the movable lid  33 . An upper space  38  of the movable lid  33  communicates with the waste ink chamber  14 , which is open to the air via the air hole  20   b  of the partition plate  20 . 
   The movable lid  33  is vertically movable along the inner peripheral surface  31   a  of the cylindrical container  31 . It includes a disc-shaped lid part  33   a  and a cylindrical part  33   b  which extends downwardly from the outer peripheral edge of the lid part  33   a . By designing the cylindrical body part  33   b  to have a predetermined length, the movable lid  33  may be smoothly moved without rattling or dragging on the inner peripheral surface  31   a . Filling the container  31  with ink, the ink advances into a gap  37  between the movable lid  33  and the inner peripheral surface  31   a  to form an ink meniscus therein. If the gap  37  is designed to have an appropriate dimension, a strength of the ink meniscus formed in the gap  37  is larger than an ink suction force acting on the ink outlet  15 ( 2 ), so that the ink meniscus is not broken even at the time of ink sucking operation. 
   Specifically, the outer diameter of the cylindrical body part  33   b  of the movable lids  33  is smaller than the inner diameter of the inner peripheral surface  31   a  of the cylindrical container  31  by about 0.1 mm. When the movable lid  33  is inserted into the cylindrical container  31  in a coaxial fashion, an annular gap  37  of about 0.05 mm wide is formed between them. To prevent the movable lid  33  from dragging along the inner peripheral surface  31   a , the length of the cylindrical body part  33   b  is about 8 mm. 
   Further, the ink reservoir  35  is always in a state that a predetermined negative pressure is applied by a lifting force of the movable lid  33  caused by the coiled spring  34 . Accordingly, when the ink suction force does not act on the ink outlet  15 ( 2 ), the ink does not leak out of the ink reservoir  35  via the ink outlet  15 ( 2 ). 
   A lifting force of the movable lid  33  caused by the coiled spring  34  is smaller than a strength of the ink meniscus and the ink suction force exerted by an outlet port  15   b . Therefore, the ink meniscus is not broken by the lifting force of the coiled spring  34 , and air bubbles do not advance into the ink reservoir  35 . 
   When the ink is sucked from the ink outlet  15 ( 2 ), the movable lids  33  move toward the ink outlet  15 ( 2 ) in accordance with an ink suction amount. For example, the lifting force by the coiled spring  34  is selected to fall within a range from about 5 gf to about 15 gf, in view of the strength of the meniscus in the gap  37 . 
   Since the central part of the upper surface of each movable lid  33  is flat, when the movable lid  33  moves upward, the upper surface of the movable lid  33  is brought into a substantially line contact with the lower end of the projection  20   c  of the partition plate  20 , to stop the upward movement of the movable lid  33  (see  FIG. 5A ). 
   As shown in  FIG. 5B , at a part  31   d  of the inner peripheral surface  31   a  in the vicinity of the bottom surface  31   b , the inner diameter of the container  31  is gradually reduced such that the inner diameter of the container  31  is made identical with the outer diameter of the movable lid  33  at a lower end portion  31   e  of the container  31 . The lower end portion  31   e  continues to the bottom surface  31   b  via a curved corner  31   f . In such a configuration, the gap between the lid  33  and the inner peripheral surface  31   a  is narrowed while the movable lid  33  closes to the bottom surface  31   b , so that the strength of the meniscus formed in the gap increases. When the movable lid  33  reaches the lower end portion  31   e , the movable lid  33  is secured by the inner peripheral surface  31   a.    
   At a portion of the bottom wall  21  corresponding to the center of the bottom surface  31   b , a circular opening  41  is formed and a tubular frame  42  is extended downward to surround the opening  41 . An annular rubber packing  43  formed with a through hole is fitted into the cylindrical frame  42  so that the through hole serves as an ink outlet port  15   b . A tubular frame  44  extends upward from the bottom surface  31   b  so as to surround the opening  41  to define a passage  45  between the ink reservoir  35  and the ink outlet port  15   b . A valve  46  capable of sealing the ink outlet port  15   b  is disposed in the passage  45 . The valve  46  is always pressed against the rubber packing  43  by a coiled spring  47  to seal the ink outlet port  15   b.    
   A filter  48  for filtering out foreign materials is attached to an upper end of the tubular frame  44 . Accordingly, the filter  48  catches foreign materials contained in the ink supplied from the ink reservoir  35  to the ink supplying needle  7 ( 2 ), thereby preventing the foreign materials from entering the print head  4 . 
   When the ink reservoirs  35  of the ink chambers  13 ( 1 ) to  13 ( 4 ) are filled with the respective colors of ink, the movable lids  33  are placed in the vicinity of the partition plate  20  as shown in  FIG. 5A . Specifically, the movable lids  33  are positioned near the upper ends of the cylindrical containers  31 . 
   Since ink meniscuses are each formed between the movable lid  33  and the inner peripheral surface  31   a  of each cylindrical container  31 , the spaces  38  in the upper side of the movable lids  33 , which communicate with the waste ink chamber  14 , are partitioned from the ink reservoirs  35  by the movable lids  33 . Further, since the movable lids  33  are each pushed upward by the coiled spring  34 , the ink reservoirs  35  are each kept at a predetermined negative pressure. 
   When an ink suction force is exerted from the print head  4  of the ink jet printer  1  on each ink outlet port  15   b , the movable lid  33  moves toward the ink outlet port  15   b  against the spring force of the coiled spring  34 . As a result, a predetermined amount of ink is supplied to the print head  4 , via the ink outlet port  15   b.    
   The strength of the ink meniscus formed in the gap  37  between the movable lid  33  and the inner peripheral surface  31   a  of the cylindrical container  31  is larger than the ink suction force. Therefore, the ink meniscus is not broken by the ink suction force. As a result, air bubbles do not advance from the upper side of the movable lid  33  into the ink reservoir  35 , via the gap  37 . Further, ink does not leak from the ink reservoir  35  to the upper side of the movable lid  33 , via the gap  37 . 
   When the ink chambers  13 ( 1 ) to  13 ( 4 ) are each in an ink end state (i.e., there is substantially no more ink remaining in the chambers), the movable lids  33  are placed at the lower end portions  31   e  of the cylindrical containers  31 , and capacities of the ink reservoirs  35  are reduced to the minimum. When the movable lid  33  descends, the coiled spring  34  is compressed and the force for lifting the movable lid  33  increases. Accordingly, the ink meniscus would be easy to break if the inner diameters remained the same. 
   However, since the inner diameters of the containers  31  are gradually reduced at tapered portions  31   d  so that the strength of the meniscuses increases, the invasion of air bubbles to the ink reservoirs  35  due to the meniscus breakage can be avoided, even in the ink end state. 
   When the ink cartridge  10  is accidentally dropped, or an impact force is applied to the ink cartridge  10 , the movable lids  33  vibrate so that the ink meniscuses are broken. As a result, the ink leaks to the upper side of the movable lid  33 . However, since the spaces  38  in the upper side of the movable lids  33  are separated from one another by the movable lid  33  and the partition plate  20  for each of the ink chambers  13 ( 1 ) to  13 ( 4 ), the ink leaked from the respective ink reservoirs  35  will not mix with ink from other reservoirs  35 . In addition, since the air holes  20   b  are separated from the respective inner peripheral surfaces  31   a , the ink leaked via the outer periphery of the movable lid  33  will not directly enter to the waste ink chamber  14  via the air holes  20   b . To the contrary, the ink leaked to the spaces  38  returns to the respective ink reservoirs  35  along the inner peripheral surfaces  13   a.    
   Even when ink leaks to the side of the waste ink chamber  14  via the air hole  20   b  formed at the upper end of the projection  20   d  and extended from the upper surface  20   e  of the partition plate  20 , the leaked ink will not enter another ink chamber via another air hole  20   b . Instead, the leaked ink is absorbed by the ink absorbing member  17  surrounding the projections  20   d , and thus prevented from returning to the ink chambers  13 ( 1 ) to  13 ( 4 ) while being prevented from mixing with another color of ink. Since the leaked ink absorbed by the ink absorbing member  17  does not return to the ink chambers  13 ( 1 ) to  13 ( 4 ), the foreign matters derived from the ink absorbing material  17  will not mix with the ink leaked to the space  38 , and returns to the ink reservoir  35 . 
   Even when a substantial amount of ink leaks from the ink reservoir  35  and the space  38  fills with the leaked ink, since the air hole  20   b  is separated from the ink absorbing member  17 , the leaked ink will not be sucked by the ink absorbing member  17 . Since only ink leaked to the waste ink chamber  14  via the air hole  20   b  is absorbed by the ink absorbing member  17 , less ink is rendered useless, and ink wastage is reduced. 
   Further, since the movable lids  33  are brought into the line contact with the lower ends of the projections  20   c , the upper surfaces of the movable lids  33  are not brought into the face contact with the partition plate  20  and adhered thereon. 
   The present invention may also have various advantages, although it is not limited to these advantages, nor is it required to have these advantages. For example, but not by way of limitation, less ink is wasted, and inks of different colors are not mixed with one another. Further, foreign matter does not re-enter the reservoir, and the related art problems associated with dropping or impact of the cartridge are also substantially eliminated. 
   Although the present invention has been shown and described with reference to specific exemplary, non-limiting embodiments, various changes and modifications will be apparent to those skilled in the art from the teachings herein. Such changes and modifications as are obvious are deemed to come within the spirit, scope and contemplation of the invention as defined in the appended claims. 
   For example, but not by way of limitation, although the ink cartridge  10  of the above embodiment comprises four ink chambers, the number of the ink chambers may be less than or greater than four. 
   Further, the projections  20   d  may be omitted. Even in such a case, ink leaked through the air hole  20   b  is absorbed by the ink absorbing member  17  surrounding the air hole  20   b.    
   In the above embodiment, a ringing phenomenon in which the partition plate  20  and the movable lid  35  are adhered is prevented by the tubular projection  20   c . The tubular projection  20   c  may be provided on at least one of the partition plate  20  and the movable lid  35 .