Patent Publication Number: US-6666550-B2

Title: Ink cartridge

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The invention relates to an ink cartridge for storing ink therein to be supplied to an ink-jet head of an ink-jet recording device. 
     2. Description of Related Art 
     U.S. Pat. No. 6,270,207 B1 discloses an ink cartridge that includes a case having therein side partitioning walls and a bottom partitioning wall to divide the inside of the case into a first ink chamber, a second ink chamber and an atmosphere connection chamber. In the ink cartridge, the bottom partition wall has a connecting hole that connects the first chamber and the second chamber to each other. The opening of the connecting hole is circular in horizontal cross-section. 
     U.S. Pat. No. 6,074,051 discloses an ink cartridge that includes a cartridge case having a partition which partitions the cartridge case interior into an ink chamber and a storage chamber. The ink chamber contains ink, and the storage chamber contains a member impregnated with ink. The partition has an ink passage formed through it at its bottom to connect the ink chamber and the storage chamber. 
     SUMMARY OF THE INVENTION 
     The invention provides an ink cartridge wherein blocking of a connecting hole, which connects a porous member storage chamber and an ink chamber, by an air-bubble, is prevented, thereby effectively preventing ink leakage from an ink-jet head. 
     According to one aspect of the invention, an ink cartridge for storing ink to be supplied to an ink-jet head, includes a case having a partition therein for dividing an inside of the case into a first chamber and a second chamber, and a porous member is accommodated in the first chamber and impregnated with the ink. In the ink cartridge, the partition wall has a connecting hole that passes through the partition wall in a gravity direction when printing is performed by the ink-jet head. The connecting hole connects the first chamber and the second chamber in the gravity direction. The opening of the connecting hole has noncircular cross-section in a direction perpendicular to the gravity direction. 
     With this structure, the connecting hole is prevented from being closed by an air-bubble, so that ink stored in the first chamber and ink stored in the second chamber can always be in contact with one another. Accordingly, the ink in the ink chamber can be absorbed by the porous member at all times. Consequently, ink leakage from the ink-jet head can be effectively prevented. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Exemplary embodiments of the invention will be described in detail with reference to the drawings wherein: 
     FIG. 1 is a perspective view showing an embodiment of a color ink-jet printer; 
     FIG. 2 is a sectional view showing an embodiment of an ink cartridge of the invention; 
     FIG. 3 is a plan view of a connecting hole provided in the ink cartridge of FIG. 2; 
     FIG. 4 is a plan view of another embodiment of a connecting hole provided in the ink cartridge of FIG. 2; and 
     FIG. 5 is a plan view of another embodiment of a connecting hole provided in the ink cartridge of FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Exemplary embodiments of the invention will be described with reference to the accompanying drawings. As shown in FIG. 1, the exemplary color ink jet printer  21  includes four ink cartridges  22  (although there could be more or less ink cartridges  22 ), an ink-jet head  24 , a head unit  25 , a carriage  26 , a drive unit  27 , a platen roller  28 , and a purge device  29 . The ink cartridges  22  are each filled with a particular color of ink, such as cyan, magenta, yellow and black. The ink-jet head  24  performs printing using the color inks on a recording medium  23 , such as a recording sheet. The ink-jet head  24  is provided on the head unit  25 . The ink cartridges  22  and the head unit  25  are mounted on the carriage  26 . The drive unit  27  reciprocates the carriage  26  in a straight line. The platen roller  28  extends in a carriage reciprocating direction and faces the ink-jet head  24 . 
     The drive unit  27  includes a carriage shaft  30 , a guide plate  31 , two pulleys  32 ,  33  and an endless belt  34 . The carriage shaft  30  is disposed at a lower end of the carriage  26  and extends in a direction parallel to the platen roller  28 . The guide plate  31  is disposed at an upper end of the carriage  26  and extends in a direction parallel to the carriage shaft  30 . The pulleys  32 ,  33  are disposed at both ends of the carriage shaft  30 , between the carriage  26  and the guide plate  31 . The endless belt  34  is stretched between the pulleys  32  and  33 . 
     A carriage shaft support portion  35 , into which the carriage shaft  30  is inserted, and a guide plate contact portion  36 , which can abut against the guide plate  31 , are provided at the lower and upper end portions of the carriage  26 , respectively. The endless belt  34  is connected with a rear surface of the carriage  26 . 
     As the pulley  32  is rotated in normal and reverse directions by a carriage motor  32 A, the carriage  26  connected to the endless belt  34  reciprocates in the straight line, along the carriage shaft  30  and the guide plate  31 , according to the rotation in the normal and reverse directions of the pulley  32 . 
     The recording medium  23  is fed from a sheet cassette (not shown) provided in a side or a lower part of the color ink jet printer  21 . The recording medium  23 , fed from the sheet cassette, is fed between the ink-jet head  24  and the platen roller  28  to perform printing on the recording medium  23  by ink droplets ejected from the ink-jet head  24 . Then, the recording medium  23  is discharged from the color ink jet printer  21 . In FIG. 1, the sheet feeding mechanism and the discharging mechanism for the recording medium  23  are omitted. 
     A purge device  29  is disposed next to the platen roller  28 . When the head unit  25  is in a reset position, the purge device  29  is opposed to the ink-jet head  24 . The purge device  29  serves to recover a condition of the ink-jet head  24  to prevent the occurrence of an ink ejection failure, caused by a buildup of ink and development of air-bubbles in the ink-jet head  24  when ink is first provided to the ink-jet head  24 . The purge device  29  includes a suction cap  37 , a pump  38 , a cam  39  and a waste ink reservoir  42 . When the head unit  25  is located in the reset position, the suction cap  37  covers a nozzle surface to cover nozzles (not shown) formed in the ink-jet head  24  to draw ink, including air-bubbles trapped in the ink-jet head  24 , using the suction pump  38  activated by the cam  39 , thereby purging the ink-jet head  24 . The drawn ink is stored in the waste ink reservoir  42 . 
     The ink cartridge  22  includes a substantially rectangular case  51 , a top cover  52  that covers the top of the case  51 , and a bottom cover  53  that covers the bottom of the case  51 . 
     The case  51  has side outer walls  58 ,  59 , and side partition walls  60 ,  61  and a bottom partition wall  63  therein. The side partition walls  60 ,  61  extend in a direction parallel to the side outer walls  58 ,  59 , respectively, at a predetermined distance therefrom. Both upper ends of the side partition walls  60 ,  61  abut against the top cover  52 . The bottom partition wall  63  extends in a direction parallel to the bottom cover  53 , so as to bridge between the lower ends of the side partition walls  60 ,  61 , and is provided at a predetermined distance from the bottom cover  53 . Therefore, the case  51  has a double-walled structure. A partition wall  64  is provided substantially in the middle of a longitudinal side of the ink cartridge  22 , between the bottom partition wall  63  and the bottom cover  64 , so as to extend in a direction parallel to the walls  58 ,  59 . 
     The inside of the case  51  is separated into three areas by partition walls  60 ,  61 ,  63  and  64 , namely, a porous member storage chamber  55 , an ink chamber  56 , and an air trap chamber  57 . The porous member storage chamber  55  is defined by the top cover  52 , the side partition walls  60 ,  61 , and the bottom partition wall  63 . The porous member storage chamber  55  accommodates therein a porous member  54  that is made of urethane foam and impregnated with ink. 
     The ink chamber  56  contains ink therein. The ink chamber  56  includes a space that is defined by the top cover  52 , the side outer wall  58  and the side partition wall  60  so as to extend vertically, and a space that is defined by the bottom cover  53 , the bottom partition wall  63  and the partition wall  64  so as to extend in a horizontal direction. These spaces are connected to each other. 
     The air trap chamber  57  is a space for providing air into the porous member storage chamber  55 . The air trap chamber  57  includes a space that is defined by the top cover  52 , the side outer wall  59  and the side partition wall  61  so as to extend vertically, and a space that is defined by the bottom cover  53 , the bottom partition wall  63  and the partition  64  so as to extend in the horizontal direction opposite to the direction of the horizontally extending portion the ink chamber  56 . 
     The bottom partition wall  63  has a connecting hole  65  near the partition wall  64 . The connection hole is rectangular in cross section, and connects the porous member storage chamber  55  and the ink chamber  56  with each other. The bottom cover  53  has an ink outlet  67  to supply ink to the ink-jet head  24  from the ink chamber  56 . 
     The bottom cover  53  of the air trap chamber  57  has an air inlet  68 , so that the air trap chamber  57  communicates with the outside (the air) via the air inlet  68 . The top cover  52  has a communication path  69  to connect the porous member storage chamber  55  and the air trap chamber  57  with each other for the supply of air. 
     The head unit  25  includes the ink-jet head  24 . The ink-jet head  24  is covered with a head cover  81 , except for a nozzle surface, and attached to a head holder  71 , to which the ink cartridges  22  are attached. The head unit  25  is attached to the carriage  26  via the head holder  71 . 
     The ink-jet head  24  includes an actuator  73  and a manifold  74 . The actuator  73  has a plurality of ejection channels  76  for ejecting ink droplets from nozzles. The manifold  74  is connected with the actuator  73  and supplies ink to each of the ejection channels  76  in the actuator  73 . 
     The manifold  74  is made of a resin. In the manifold  74 , an ink leading portion  75  and an ink supply portion  78  are integrally formed. The ink leading portion  75  leads ink to the ink supply portion  78  from the ink cartridge  22 . The ink supply portion  78  supplies the ink to each of the ejection channels  76  in the actuator  73 . 
     The head holder  71  has a hole  72  in a position opposed to the ink outlet  67  of the ink cartridge  22 . A ring-shaped seal member  79 , made of an elastic material, is adhesively fixed in the hole  72 . 
     The ink leading portion  75  of the manifold  74  is inserted in the seal member  79 . Thus, the ink leading portion  75  is connected with the ink outlet  67  of the ink chamber  56  via the seal member  79 . 
     A base plate  80  made of a metal material is interposed between the head holder  71  and the ink leading portion  75 . The base plate  80  is used to determine a reference position of the ink-jet head  24 . The ink supply portion  78  is bonded to the base plate  80 , thereby supporting the ink-jet head  24  by the base plate  80 . The base plate  80  is bonded to the head holder  71 . 
     Ink contained in the ink chamber  56  of the ink cartridge  22  is supplied to the ink supply portion  78  of the manifold  74  via the ink outlet  67  and the ink leading portion  75 . Then, the ink is supplied to the ejection channels  76  of the actuator  73  from the ink supply portion  78 . The actuator  73  is, for example, made of a piezoelectric ceramic material. The ink, supplied to the ejection channels  76  of the actuator  73 , is ejected from the nozzles when the actuator  73  is deformed so as to reduce its volume therein. When the volume of the actuator  73  is increased, that is, the actuator  73  goes back to its normal state, the ink is drawn into the ejection channels  76  from the ink supply portion  78 . By repeating such an operation, printing is performed on a recording sheet. 
     When the ink-jet head  24  is driven, ink absorbed by the porous member  54  is supplied to the ink chamber  56 , via the connecting hole  65 , and is stored therein. Then, the ink is supplied to the ink-jet head  24  via the ink outlet  67  of the ink chamber  56  and the seal member  79 . At that time, the amount of the ink absorbed by the porous member  54  is reduced by the supply of the ink to the ink-jet head  24 . Air, which flowed into the air trap chamber  57  via the air inlet  68 , flows into the porous member storage chamber  55  from above via the communication path  69 , so that the ink level in the chamber  55  is gradually lowered by air pressure. Thus, ink can be continuously supplied to the ink-jet head  24 . 
     When the ink absorbed by the porous member  54  runs out, the ink stored in the ink chamber  56  is supplied to the ink-jet head  24 . As the ink is supplied to the ink-jet head  24 , air flows into the ink chamber  56 , through the connecting hole  65 , from the porous member storage chamber  55 . At that time, the air becomes air-bubbles and flows into the ink chamber  56  through the connecting hole  65 . The air-bubbles, which flow into the ink chamber  56 , stay on the surface of the ink (the upper portion of the ink chamber  56 ). Thus, the ink level also gradually lowers in the ink chamber  56 , so that the ink can be continuously supplied to the ink-jet head  24 . 
     When the ink-jet head is not driven, the porous member  54  absorbs the ink stored in the ink chamber  56  by capillary attraction because the ink in the ink chamber  56  contacts the porous member  54  via the connecting hole  65 . Accordingly, ink leakage from the ink-jet head  24  can be effectively prevented. 
     As shown in FIG. 2, in the ink cartridge  22 , the connecting hole  65  is provided in the middle of the bottom partition wall  63  (substantially centered between the side partition walls  60  and  61 ). As shown in FIG. 3, the shape in horizontal cross-section of the opening of the connecting hole  65  is a rectangle. The connecting hole  65  is tapered from the porous member storage chamber side to the ink chamber side. More specifically, the connecting hole  65  extends in a direction along a longer side of the bottom partition wall  63 . The connecting hole  65  has sides extending along the longer sides of the bottom partition wall  63  (hereinafter, referred to as longer sides X) and sides extending along a direction perpendicular to the longer sides of the bottom partition wall  63  (hereinafter, referred to as shorter sides Y). 
     The sides X, extending along the longer sides of the bottom partition wall  63 , are longer than the sides Y, extending along the shorter sides of the bottom partition wall  63 . A ratio of a length between the longer sides X and the shorter sides Y in the connecting hole  65  is substantially equal to a ratio of a length between the longer sides and the shorter sides in the bottom partition wall  63 . 
     The connecting hole  65  is provided in the bottom partition wall  63 , at a predetermined distance W, inside in the direction perpendicular to the longer sides of the bottom partition wall  63 , from the longer sides of the bottom partition wall  63  (that is, from each inner surface of walls  66  extending in a direction perpendicular to the outer wall sides  58 ,  59  of the ink cartridge  22 ). The connecting hole  65  is provided equidistant from the four corners of the bottom partition wall  63 . 
     In the ink cartridge  22 , as the ink stored in the ink chamber  56  is supplied to the ink-jet head  24 , the air, flowing into the ink chamber  56  from the porous member storage chamber  55  through the connecting hole  65 , becomes air-bubbles, and an air-bubble may be trapped in the connecting hole  65 . However, the ink cartridge  22  has the connecting hole  65 , whose opening is a rectangle in the horizontal cross-section. With this structure, a portion appears in the connecting hole  65 , where the air-bubble does not contact the edge of the connecting hole  65 . Thus, the connecting hole  65  is not completely occluded by the air-bubble. Therefore, the ink absorbed by the porous member  54  and the ink stored in the ink chamber  56  can always be in contact with each other via the connecting hole  65 . Accordingly, the ink stored in the ink chamber  56  can be absorbed by the porous member  54  at all times, thereby effectively preventing ink leakage from the ink-jet head  24 . 
     In the ink cartridge  22 , the connecting hole  65  is provided in the middle of the bottom partition wall  63 , extending in the direction along the longer sides of the bottom partition wall  63 . The ink is likely to remain at corners of the porous member  54  (the corner formed by the side partition wall  60  and the bottom partition wall  63  and the corner formed by the side partition wall  61  and the bottom partition wall  63 ). However, with the structure of the ink cartridge  22  described above, the ink is easily lead to the connecting hole  65 . Thus, the ink can be satisfactorily supplied. 
     In the ink cartridge  22 , the connecting hole  65  is provided in the bottom partition wall  63 , at the predetermined distance W inside the walls  66 , extending in the direction toward the shorter sides of the bottom partition wall  63 , and from the longer sides of the bottom partition wall  63 . The porous member  54  cannot make enough contact with the wall at the corners of the porous member storage chamber  55 . As a result of this, the resistance of the porous member  54  is reduced so that air-bubbles flow easily into the connecting hole  65  along the edge of the porous member storage chamber  55 . However, with this structure, such air-bubbles can be effectively prevented from flowing into and filling the connecting hole  65 . Accordingly, occlusion of the connecting hole  65  caused by such air-bubbles can be further effectively prevented. 
     In the ink cartridge  22 , the connecting hole  65  is tapered from the porous member storage chamber side to the ink chamber side and is provided equidistant from the corners of the bottom partition wall  63 . The ink cartridge  22  has an ink filling hole  62  in the top cover  52  so as to connect the ink chamber  56 . With this structure, when ink is filled into the ink cartridge  22  from the ink filling hole  62 , the ink is first filled into the ink chamber  56  and then filled into the porous member storage chamber  55  via the tapered connecting hole  65 . Therefore, the ink can be easily distributed over the porous member  54 . Further, the connecting hole  65  has a rectangular shape in cross section. Therefore, the rectangular connecting hole  65  can be easily formed when manufacturing the ink cartridge  22 . This results in increasing production efficiency of the ink cartridge  22 . 
     In the embodiment described above, the horizontal cross-sectional shape of the opening of the connecting hole  65  of the ink cartridge  22  is a rectangle. In the invention, however, the shape of the opening of the connecting hole  65  is not particularly restricted to a rectangle, so long as the connecting hole  65  is noncircular in cross-section and extends in the direction along the longer sides of the bottom partition wall  63 . For example, as shown in FIG. 4, the connecting hole  65  can be triangle in horizontal cross-section. With this structure, the contact area of an air-bubble and the connecting hole  65  can be further reduced. Accordingly, the occlusion of the connecting hole  65  by the air-bubble can be further prevented. 
     Further, as shown in FIG. 5, the connecting hole  65  can have, for example, a substantially H-shape in horizontal cross-section. Further, the connecting hole  65  may have complicated shape. For example, the connecting hole  65  can be shaped like a star. 
     While the invention has been described in detail with reference to specific embodiments thereof, it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit of the invention.