Patent Publication Number: US-8109620-B2

Title: Liquid storage container and liquid ejection recording apparatus having the container mounted thereon

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 11/390,835 filed Mar. 28, 2006, which claims the benefit of Japanese Application No. 2005-101929 filed Mar. 31, 2005, all of which are hereby incorporated by reference herein in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an ink cartridge for storing ink therein to be fed to an inkjet recording head and an inkjet recording apparatus having the ink cartridge mounted thereon. 
     2. Description of the Related Art 
     Various types of ink cartridge have been proposed. An ink cartridge is a liquid storage container storing ink therein for feeding the ink to an inkjet recording apparatus. Ink cartridges are roughly classified into three types as follows. 
     A first type is a so-called whole sponge type for retaining ink by arranging a capillary material, such as a sponge, within the entire internal space of the ink cartridge. A second type is a so-called whole raw ink type directly storing ink in a bag without using such a capillary material. A third type is a so-called semi-raw ink type in that one half of the ink cartridge is provided with the capillary material while the other half is provided with a raw ink chamber for directly storing ink within a casing. 
     In order to preferably feed ink to the recording head for ejecting the ink, in any of these types of ink cartridges, a configuration for adjusting holding power of the ink stored in the ink cartridge is important. Since this holding power is for leaving the pressure of an ink ejection part of the recording head negative relative to the atmosphere, the holding power is called a negative pressure. 
     In the whole sponge type mentioned above, ink is retained due to the characteristics of the capillary material and the negative pressure applied to the ink, so that this type has been adopted in various products. 
     However, in the whole sponge type, the amount of ink retained in the ink cartridge is small in ratio in comparison with the whole raw type. Also, since the negative pressure level and the flow resistance are increased just before ink is used up, the ink remains within the sponge, so that the available ink amount is smaller than the entire volume of the ink cartridge, i.e., the storing efficiency is small. Thus, a whole raw type ink cartridge is proposed in which a spring member is provided in an ink bag for urging the ink bag so as to maintain the bag at a negative pressure in order to increase the ink capacity per unit volume of the ink cartridge and also to achieve stable ink feeding (Japanese Patent Laid-Open No. H06-198904). 
       FIG. 6  is an exploded view of an ink cartridge having the configuration disclosed in Japanese Patent Laid-Open No. H06-198904, and  FIG. 7  shows the interior of the ink cartridge being urged so as to maintain it under negative pressure. 
     An ink cartridge  10  shown in  FIG. 6  includes a plastic frame  16  defining an open space serving as an ink reservoir. Within the open space of the frame  16 , a pressure regulator  30  is accommodated for maintaining the interior at a negative pressure. On one side of the open space of the frame  16  is provided a flexible thin film  22  bonded to the plastic frame so as to close the one side of the open space. A hard cover plate  12  is bonded with an adhesive on the thin film  22  so as to cover it. On the other side of the open space is provided a flexible thin film  24  bonded to the plastic frame so as to close the open space. A hard cover plate  14  is bonded with an adhesive on the thin film  24  so as to cover it. Thereby, a flexible ink reservoir having a pressure regulator  30  accommodated therein is formed within the ink cartridge  10 . 
     A tip portion  13  of the ink cartridge  10  is provided with an ink ejection nozzle arranged on the bottom end wall, to which a print head (not shown) is mounted and electrically driven. 
     The pressure regulator  30  includes a pair of plates  40  and  50  spaced in parallel with each other and urged with a bow spring  60  in a direction separating each other so as to move into engagement with the thin films  22  and  24  forming the flexible ink reservoir, respectively. An ink filter  18  is provided at a position inside the frame  16  and corresponding to the tip portion  13 . The ink filter  18  is communicated with the ink reservoir by an appropriate porting element and includes an ink outlet communicated with the print head. 
     Under no stress conditions, the bow spring  60  is shaped as shown in solid lines of  FIG. 7 . When ink is fed outside the ink cartridge  10  from the ink reservoir, the thin films  22  and  24  move close to each other. Along with this movement, the side plates  40  and  50  of the pressure regulator  30  also move gradually so as to approach each other. Thereby, the side plates  40  and  50  and the bow spring  60  move to a mid point as shown by two-dot chain lines of  FIG. 7 . At this time, the bow spring  60  for urging the ink reservoir is compressed, so that the negative pressure level in the ink reservoir is increased. 
     In the ink cartridge configured as described above, if an external impact is directly transmitted to the thin films forming the ink reservoir, the thin film may be torn, causing ink leakage. This also applies large vibration to the ink stored in the flexible ink reservoir so that the ink supply to the head becomes unstable, which may cause printing nonconformity. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an ink cartridge and an inkjet recording apparatus incorporating the same which prevent printing nonconformity even during high speed inkjet-recording with multiple nozzles by alleviating rapid external impact applied from the outside of the ink cartridge. 
     Furthermore, the present invention provides an ink cartridge capable of sufficiently feeding ink without affecting the ink supply when the negative pressure level in the ink cartridge is rapidly increased by the increase in the ink supply per unit time from the ink cartridge to the inkjet head along with high speed inkjet-recording with multiple nozzles or by the temporary increase in the ink supply from the ink cartridge during recovery operation of the inkjet head, even when having an alleviation structure for external impact. The present invention also solves the possible problem in that even when having an alleviation structure for external impact, the negative pressure level in the ink cartridge is increased by the increase in ink resistance due to changes in ink physical property (especially in viscosity) so that ink does not flow smoothly. 
     In one aspect of the present invention, a liquid storage container includes a liquid reservoir adapted to store a liquid therein; a first spring member accommodated within the liquid reservoir and urging the liquid reservoir so as to maintain the interior of the liquid reservoir at a negative pressure; a casing having a wall and accommodating the liquid reservoir therein; a supply port formed on the wall and facilitating supplying the liquid in the liquid reservoir to the outside; and a stress damping unit provided between the liquid reservoir and the wall of the casing, the stress damping unit damping stress applied to the liquid reservoir. 
     According to the present invention, a reliable ink cartridge and inkjet recording apparatus can be provided, which reduce printing nonconformity even during high speed inkjet-recording with multiple nozzles by alleviating rapid external impact applied from the outside of the ink cartridge. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view of an ink cartridge according to a first embodiment of the present invention. 
         FIG. 2  is a sectional view of an ink cartridge according to a second embodiment of the present invention. 
         FIG. 3A  is a drawing showing the ink cartridge when ink is consumed according to the second embodiment. 
         FIG. 3B  is a drawing showing the ink cartridge when ink is consumed according to the second embodiment. 
         FIG. 3C  is a drawing showing the ink cartridge when ink is consumed according to the second embodiment. 
         FIG. 4  is a sectional view of an ink cartridge according to a third embodiment of the present invention. 
         FIG. 5  is an explanatory drawing illustrating an example of a liquid-ejection recording apparatus capable of mounting a liquid storage container according to the present invention. 
         FIG. 6  is an exploded view of the conventional ink cartridge disclosed in Japanese Patent Laid-Open No. H06-198904. 
         FIG. 7  is an explanatory drawing illustrating the pressure regulator shown in  FIG. 6 . 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Embodiments according to the present invention will be described with reference to the drawings. In the following embodiments, ink is exemplified as a liquid in the ink cartridge. However, the liquid is not limited to ink and may also include a processing liquid for a recording medium in inkjet recording. 
     First Embodiment 
       FIG. 1  is a sectional view of an ink cartridge according to a first embodiment of the present invention. 
     An ink cartridge (liquid container)  100  shown in  FIG. 1  includes a hard casing  110  having an interior space and an ink supply port  111  formed on the wall of the casing  110  for supplying ink  112  (shown by reticular lines in the drawing) to the outside. 
     Within the casing  110 , a film-like flexible bag  107  is accommodated for storing the ink  112  therein. The opening of the flexible bag  107  is joined onto the wall position where the ink supply port  111  is formed so as to form an ink reservoir  103 . A sheet member  113  is provided on a portion of the flexible bag  107  opposing the wall position of the casing  110  where the ink supply port  111  is formed for flattening the portion. Between the wall position of the casing  110  where the ink supply port  111  is formed and the sheet member  113 , a compression spring  105  is provided for urging the flexible bag  107  in a direction expanding the flexible bag  107 . That is, the compression spring  105  urges the flexible bag  107  so as to maintain the interior of the flexible bag  107  at a negative pressure. 
     Between the surface of the flexible bag  107  where the sheet member  113  is bonded and the wall surface of the casing  110 , a stress damping chamber  104  is formed for damping the stress applied to the flexible bag  107 . The stress damping chamber  104  and the ink reservoir  103  are arranged in series in an expansion/contraction direction of the compression spring  105 . The stress damping chamber  104  is formed by joining one opening of an elastically flexible cylinder  108  (such as a bellows, and the flexible cylinder  108  itself applies no stress to the flexible bag  107 ) on the surface of the flexible bag  107  where the sheet member  113  is bonded as well as by joining the other opening on the wall surface of the casing  110 . 
     The wall surface where the other opening of the flexible cylinder  108  is attached is provided with an orifice  115  formed thereon. The stress damping chamber  104 , which is an air chamber, is communicated with the atmosphere outside the ink cartridge via the orifice  115  formed on the wall surface of the casing  110 . The orifice  115  allows air to promptly flow in the chamber in accordance with the displacement of the flexible bag  107  accompanied by ink consumption due to the normal operation of the ink cartridge mounted on a printer. However, if an external impact is applied so as to promptly displace the flexible bag  107 , the flexible cylinder  108  is also displaced rapidly along with the displacement of the flexible bag  107 . At this time, the volume of the stress damping chamber  104  formed of the flexible cylinder  108  changes. Due to this change, outside air of the stress damping chamber  104  may be pulled in or inside air may be extruded. At this time, the orifice  115  serves as a resistance against the rapid air flow so as to suppress the displacement of the flexible bag  107  by inhibiting the displacement of the stress damping chamber  104 . That is, the stress damping chamber  104  serves as a shock absorber using the resistance during air flow into and out through the orifice  115  due to the expansion/contraction of the flexible cylinder  108 . 
     In the ink cartridge  100  structured as described above, an external impact applied from the outside of the ink cartridge is attenuated by the stress damping chamber  104 , so that the impact is not directly transmitted to the flexible bag  107  forming the ink reservoir  103 . Thereby, the flexible bag  107  may not be damaged by the impact so as to prevent ink leakage. 
     The vibration of ink within the flexible bag  107  due to an external impact can also be suppressed, so that the ink can be stably supplied to the inkjet head. 
     Second Embodiment 
       FIG. 2  is a sectional view of an ink cartridge according to a second embodiment of the present invention. Like reference characters designate like components common to the first embodiment. 
     An ink cartridge  200  shown in  FIG. 2  includes the hard casing  110  having an interior space and the ink supply port  111  formed on the wall of the casing  110  for supplying the ink  112  (shown by reticular lines in the drawing) to the outside. 
     Within the casing  110 , the film-like flexible bag  107  is accommodated for storing the ink  112  therein. The opening of the flexible bag  107  is joined onto the wall position where the ink supply port  111  is formed so as to form the ink reservoir  103 . The sheet member  113  is bonded on a portion of the flexible bag  107  opposing the wall position of the casing  110  where the ink supply port  111  is formed for flattening the portion. Between the wall position of the casing  110  where the ink supply port  111  is formed and the sheet member  113 , the compression spring  105  is provided for urging the flexible bag  107  in a direction expanding the flexible bag  107 . That is, the compression spring  105  urges the flexible bag  107  so as to maintain the inside of the flexible bag  107  at a negative pressure. 
     Between the surface of the flexible bag  107  where the sheet member  113  is bonded and the wall surface of the casing  110 , the stress damping chamber  104  is formed. The stress damping chamber  104  and the ink reservoir  103  are arranged in series in an expansion/contraction direction of the compression spring  105 . 
     The structure described above is the same as that of the first embodiment. Whereas, the following configuration is different from that of the first embodiment. 
     According to the second embodiment, the stress damping chamber  104  is formed by joining an opening of a flexible bag  208  on the surface of the flexible bag  107  where the sheet member  113  is bonded. The flexible bag  208  can expand/contract like a bellows. 
     A sheet member  114  is bonded on a portion of the flexible bag  208  opposing the sheet member  113  of the flexible bag  107  for flattening the portion. Between the surface of the flexible bag  107  where the sheet member  113  is bonded and the sheet member  114 , a compression spring  106  is arranged substantially in series with the compression spring  105  in an expansion/contraction direction. Thereby, the sheet members  113  and  114  are urged in a direction in which the sheet members move apart. The stress damping chamber  104  is communicated with the atmosphere via an air inlet  109  penetrating the sheet member  114  and the flexible bag  208  which is bonded to the sheet member  114 . 
     Within the casing  110 , a shape-memory alloy wire  101  capable of expanding/contracting by electric energy is arranged so as to surround parts of a bonded structure composed of the flexible bag  107  and the flexible bag  208 . Parts of the shape-memory alloy wire  101  are mechanically fixed on the surface of the flexible bag  208  where the sheet member  114  is bonded, while both ends of the shape-memory alloy wire  101  are connected to an electric contact block  102  arranged on the outer wall of the casing  110  where the ink supply port  111  is formed. In a state of the shape-memory alloy wire  101  arranged in such a manner, as shown in  FIG. 2 , the flexible bag  208  is constrained by the shape-memory alloy wire  101  in a contracting direction against the repulsive force of the compression spring  106 . 
     Since the compression springs  105  and  106  are arranged within the flexible bags  107  and  208 , respectively, at the center, the shape-memory alloy wire  101  surrounding the bonded structure composed of the flexible bags  107  and  208  is arranged so as to pass through the center of the surface of the flexible bag  208  where the sheet member  114  is bonded. By such a manner, when the shape-memory alloy wire  101  is contracted, the flexible bags  107  and  208  can be contracted in a well-balanced state. 
     The relationship in force (repulsive force and contractive force) among the compression spring  105  of the ink reservoir  103 , the compression spring  106  of the stress damping chamber  104 , and the shape-memory alloy wire  101  is as follows. 
     “the contractive force of the shape-memory alloy wire  101 &gt;the repulsive force of the compression spring  105 &gt;the repulsive force of the compression spring  106 ” 
     Then, operations of components within the ink cartridge according to the embodiment will be described with reference to  FIGS. 3A to 3C . 
       FIGS. 3A to 3C  are drawings showing the ink being consumed according to the second embodiment. 
     When the ink supply port  111  is opened so as to supply the ink  112  to the head (not shown) from the state of  FIG. 3A , the ink volume in the ink reservoir  103  decreases so as to displace the flexible bag  107  forming the ink reservoir  103  as shown in  FIG. 3B . Along with this displacement, the compression spring  105  arranged within the ink reservoir  103  is compressed so that the boundary wall between the ink reservoir  103  and the stress damping chamber  104  is moved in the direction of the arrow shown in  FIG. 3B . At this time, the compression spring  106  arranged in the stress damping chamber  104  is released in compression so as to expand. Air is absorbed into the stress damping chamber  104  via the air inlet  109  arranged in the stress damping chamber  104 , and the volume of the stress damping chamber  104  increases. Thereby, the total width W of the ink reservoir  103  and the stress damping chamber  104  shown in  FIGS. 3A and 3B  does not change. As a result, the shape-memory alloy wire  101  arranged so as to surround part of the bonded structure composed of the ink reservoir  103  and the stress damping chamber  104  does not slack and maintains the initial state. 
     From such a state, by electrifying the shape-memory alloy wire  101  via the electric contact block  102 , the flexible bag  208  shrinks due to the contraction of the shape-memory alloy wire  101 . Thus, the compression spring  106  arranged within the stress damping chamber  104  compresses so as to increase its repulsive force. As a result, as shown in  FIG. 3C , the boundary wall between the ink reservoir  103  and the stress damping chamber  104  moves in the arrow direction so that the negative pressure level in the ink reservoir  103  is reduced. Because when the shape-memory alloy wire  101  is operated and the compression spring  106  is compressed before the compression of the compression spring  105  so as to decrease the volume of the stress damping chamber  104 , the impact generated by the contraction of the shape-memory alloy wire  101  is absorbed by the stress damping chamber  104 , preventing the ink leakage from the ink reservoir  103  due to the impact. 
     The operation timing of the shape-memory alloy wire  101  is effective when printing with high duty ratio, supplying a large amount of ink in recovery operation, and when the negative pressure level in the ink cartridge is decreased by an increase in ink resistance due to an increase in ink physical properties (viscosity especially) with external environmental factors such as temperature changes. Such situations can be recognized from the printer, so that the shape-memory alloy wire  101  can be electrified via the electric contact block  102  with good timing by determining the situation from the printer. 
     As described above, according to the embodiment, the stress damping chamber  104  is arranged so as to connect it to part of the ink reservoir  103  (the flexible bag  107 ) of the whole raw-ink type ink cartridge; the stress damping chamber  104  is contracted using the shape-memory alloy wire  101  operated by a drive current applied from the printer so as to increase the repulsive force of the compression spring  106  arranged in the stress damping chamber  104 ; and by displacing the flexible bag  107  with the increased repulsive force, the negative pressure level in the ink reservoir  103  can be reduced. That is, when the negative pressure level in the ink reservoir is rapidly increased, by operating the shape-memory alloy wire  101 , the negative pressure level can be improved. As a result, ink can be stably supplied, so that a reliable ink cartridge and inkjet recording apparatus that reduce printing nonconformity can be provided. The ink cartridge according to the embodiment is effective against external impact in the same way as in the first embodiment. 
     The shape-memory alloy wire  101  according to the embodiment expands/contracts with changing temperature by martensite transformation. As it has a high electric resistance, the shape-memory alloy wire  101  can easily be heated by electrification. Thus, the wire can be expanded/contracted by controlling the applied current. A product having such properties includes NT Wire for an electric current actuator (model NT-H7-TTR) manufactured by Furukawa Techno Material Co., LTD. 
     Third Embodiment 
       FIG. 4  is a sectional view of an ink cartridge according to a third embodiment of the present invention. An ink cartridge  300  according to the embodiment has basically the same configuration and operation as those of the second embodiment, and so description thereof is omitted. 
     The point in which the third embodiment differs from the second embodiment is that the electric contact block  102  for electrifying the shape-memory alloy wire  101  is arranged on a surface different from that of the casing  110  where the ink supply port  111  is provided. Thus, the shape-memory alloy wire  101  is folded to the interior of the casing  110  at a fulcrum  116  arranged in the vicinity of the wall of the casing  110  where the ink supply port  111  is formed. 
     According to the embodiment, an electrical defect can be prevented, which might be caused by the adhesion of ink leaked from the ink supply port  111  for supplying the ink to the exterior by some reason. 
     Other Embodiments 
     Then, an inkjet recording apparatus (liquid ejection recording apparatus) according to another embodiment capable of mounting the ink cartridge described above thereon will be described.  FIG. 5  is an explanatory drawing illustrating an example of the liquid ejection recording apparatus capable of mounting the ink cartridge according to the present invention thereon. 
     In the recording apparatus shown in  FIG. 5 , a recording head H 1001  connected to the ink supply port  111  of the ink cartridge according to the embodiments described above is replaceably mounted on a carriage  1102 . On the carriage  1102 , an electric connection part (not shown) is provided for transmitting a drive signal to each discharge port train via the electric connection part on the recording head H 1001 . 
     The carriage  1102  is guided by a guide shaft  1103  arranged on an apparatus body so as to extend in a principal scanning direction so that the carriage  1102  can move back and forth along the guide shaft  1103 . The carriage  1102  is driven by a principal scanning motor  1104  via a driving mechanism such as a motor pulley  1105 , a driven pulley  1106 , and a timing belt  1107  while being controlled in position and movement. The carriage  1102  is also provided with a home position sensor  1130  arranged thereon. Thus, the position can be known when the home position sensor  1130  on the carriage  1102  passes through the position of a shielding plate  1136 . 
     At the position (home position) of the carriage where the home position sensor  1130  detects the shielding plate  1136 , a cap  1137  is arranged for covering the front surface where ink discharge ports of the recording head H 1001  are formed. The cap  1137  is used for recovering the recording head by absorbing ink via openings inside the cap by an absorbing element (not shown). The cap  1137  is moved by a drive force transmitted through gears so as to cover the ink discharge surface. A cleaning blade  1138  is provided in the vicinity of the cap  1137 . These capping, cleaning, and absorption recovering are performed for the ink discharge surface of the recording head when the carriage  1102  is moved to the home position. 
     Recording media  1108 , such as printing paper and plastic thin sheets, are separated one by one from an automatic sheet feeder  1132  (ASF below) by rotating a pick-up roller  1131  with a feed motor  1135  via gears. The sheet is further transferred (secondarily scanned) by the rotation of transfer rollers  1109  so as to pass through a position (printing position) opposing the ink discharge surface of the recording head. The transfer roller  1109  is rotated by the rotation of an LF motor  1134  via gears. During the transfer, the determination of whether the sheet is fed and the confirmation of a cue position when the sheet is fed are executed when a recording medium  1108  passes through a paper end sensor  1133 . Moreover, the paper end sensor  1133  is also used for sensing the actual position of the trailing end of the recording medium  1108  so as to finally determine the present recording position from the trailing end. 
     The bottom surface of the recording medium  1108  is supported on a platen (not shown) so as to form a flat printing surface at the printing position. In this case, the discharge surface of the recording head H 1001  mounted on the carriage  1102  protrudes downward from the carriage  1102  so as to be supported between two pairs of the transfer rollers in parallel with the recording medium  1108 . 
     The recording head H 1001  is mounted on the carriage  1102  so that the lining direction of discharge ports for each discharge port train intersects with the scanning direction of the carriage  1102  for recording by ejecting liquid from these discharge port trains. 
     According to the embodiments described above, an electrothermal conversion element is provided for generating thermal energy for ejecting ink. Alternatively, the present invention may incorporate other ink ejection systems such as a system using a vibration element. 
     The present invention, in addition to general printing apparatuses, may be applied to copying machines, facsimile machines with communication systems, word processors having printers, and industrial recording apparatuses combined with various processing devices. In such printing apparatuses for recording with carriage scanning, to the ink cartridge having scanning vibration applied thereto, the configuration of the present invention is effective such that ink can be stably fed so as to suppress the reduction in printing quality. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all modifications, equivalent structures and functions.