Patent Publication Number: US-6209980-B1

Title: Ink cartridge for printer having electrodes

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to an ink cartridge which is loaded into an ink jet printer for printing, a mounting device for retaining the ink cartridge, and detection plates capable of detecting the amount of ink remaining in the ink cartridge, and when this ink has been depleted. 
     By way of example, an ink detector is shown in Japanese Patent Laid-Open No. Hei 3-277558 (known example 1), and depicts conventional means for detecting when the amount of ink in an ink cartridge is reduced below a predetermined level by printing. The ink end detector depicted in known example 1 is formed with a pair of electrodes placed in through holes formed on an inner wall face of an ink tank, which is used for supplying ink to a printer head. The depletion of the ink from the ink tank is determined as a change in the conduction state between the electrodes caused by the lack of ink therebetween, and therefore an increased resistance. Seal members for preventing ink leakage from around the electrodes are inserted in the outer periphery of the electrodes positioned within an ink cartridge. 
     By way of an additional example, an ink cartridge is disclosed in Japanese Patent Laid-Open No. Hei 5-270001 (known example 2). A first of two electrodes for detecting when the amount of ink remaining in the ink cartridge falls below a predetermined level is disposed in a chamber of the ink cartridge. The second of the two electrodes is disposed in an ink outlet port of the ink cartridge. A porous material is placed in the ink outlet port below the second ink outlet electrode for preventing air from being sucked into the ink cartridge when the ink cartridge is removed from a printer by providing a sufficient capillary force, thereby blocking any flow of bubbles into the ink cartridge. 
     By way of a further example, an ink end detector is disclosed in Japanese Patent Laid-Open No. Hei 6-262772 (known example 3). In this ink end detector one electrode is placed in an opening of the ink cartridge and the other electrode is placed in the cartridge. As the resistance value between the electrodes changes, the sucking and removing of bubbles in the proximity of an ink supply port is performed. 
     By way of yet another example, an additional known ink end detector is disclosed in Japanese Patent Laid-Open No. Hei 2-198866 (known example 4). In this ink end detector, a mesh electrode is placed so as to cover a portion ink supply port extending into the ink tank from where ink exits the ink cartridge. The mesh electrode covers the inner portion of the ink supply port maintained within the ink tank. 
     The use of the detectors depicted in known examples 1-3, does not greatly affect the supplying of ink from the ink cartridge to printer means. However, in known examples 1 and 2, since one electrode is placed in the ink supply port, there is some degradation of the detection accuracy of the depletion of ink from the ink tank. Since the distance between the two electrodes is great, the resistance between the electrodes is also great, and as a result, the detection accuracy decreases, and may be affected by environmental changes. The placement of the two electrodes in the ink cartridge, rather than in the ink supply port, reduces this problem. Additionally, as is shown in known example 2, in the ink cartridge with the porous material placed in the ink supply port below the electrode contained therein, foreign material may accumulate on the porous material during use, thereby affecting the detection accuracy. Additionally, the apparatus known example 3 is very complicated and costly. 
     Additionally, as is depicted in known examples 1 and 2, since one electrode is disposed in an ink reservoir or ink support port, apart from the other electrode in the ink reservoir, porous material positioned between the two electrodes increases the detection resistance value. Thus, the accuracy of detection of the required predetermined change in the resistance value in accordance with ink consumption is reduced. Additionally, it is feared that the detection accuracy may largely vary based on environmental factors, such as temperature. Further, since one of the electrodes is positioned within the ink supply port, the port must be large. However, a cartridge provided with a large number of ink chambers for holding different colors for color printing has limited space. Thus, it becomes difficult to provide adequately large ink supply ports to place the electrode therein. 
     In known example 4 in which the mesh electrode is disposed so as to cover the inner portion of the ink supply port, the device may inaccurately detect the depletion of ink from the ink tank. 
     Additionally, in known examples 1 and 2, ink leakage prevention means, comprising a rubber stopper or other seal material, is required to seal the electrode which is disposed in the ink reservoir or ink supply port where the electrode passes through the wall of the ink tank. 
     In each known example in which one electrode is disposed projecting into the ink reservoir or ink supply port, when ink flows past this electrode, the ink flow is disrupted and bubbles are prone to occur in ink, resulting in unstable and inaccurate detection of the depletion of ink from the ink tank. Therefore, it would be beneficial to provide an ink end detector which overcomes these shortcomings of these known detectors. 
     SUMMARY OF THE INVENTION 
     Generally speaking, in accordance with the invention, an improved ink end detector is provided. In order to overcome the problems of the known ink end detectors, the invention includes an ink cartridge for an ink jet printer comprising an ink chamber containing a porous material impregnated with ink and wherein paired electrode pins for detecting the depletion of ink from the ink tank are disposed in the proximity of an ink supply section in the ink chamber. The electrodes are positioned so as to penetrate a highly compressed portion of the porous material in the proximity of the ink supply section. The electrode pins are formed as thin needles and are pressingly engaged at their base points with electrode plates which are in turn electrically coupled with determiners which utilize information from the electrode pins to determine if the ink has been depleted. The electrode pins are placed so as to penetrate the porous material so as to traverse the ink chamber of the ink cartridge. 
     The invention also comprises an ink cartridge for an ink jet printer comprising an ink chamber containing a porous material impregnated with ink, wherein one of a pair of electrode pins is disposed so as to penetrate a highly compressed portion of the porous material in the ink chamber and the other is disposed so as to be exposed to an internal portion of an ink supply port of an ink supply section. 
     The invention further comprises an apparatus for mounting an ink cartridge for an ink jet printer, comprising electrode pins positioned within the ink cartridge capable of detecting the depletion of ink from the ink cartridge, the device comprising at least an ink cartridge replacement mode setter, an ink suctioner, and a determination circuit for detecting the existence of ink in an ink supply section and determining whether a printing process may be performed. The result of the determination circuit as to whether a printing process may be performed may be displayed. 
     The invention further comprises an ink cartridge for a recording apparatus containing porous material for holding ink and comprising a pair of electrodes for detecting the amount of ink remaining. A filter is disposed facing the porous material in the proximity of an ink supply section where a capillary force generated by the porous material is comparatively large. At least one of the pair of electrodes is electrically connected to the filter. The filter is formed so as to generate a capillary force stronger than that generated by the porous member. The at least one electrode and the filter are electrically connected by an electric conductor. The second of the pair of electrodes is disposed on a raised portion of the wall of the ink tank at a position lower than the position of the filter in the ink chamber. An outer end portion of one of the electrodes is bent outside the ink tank and an open end thereof abuts against a side wall of the cartridge. An intermediate projection of the bent electrode can be brought into elastic contact with a detection plate of a detection circuit. One of the electrodes may be made of a filter formed of a fine mesh, a first portion of the filter may be embedded in the wall of the cartridge and a second portion of the filter may be disposed on an outside portion of the cartridge. An ink supply section in the ink chamber may be formed with an enlarged projection and an inner end portion of the filter may be embedded therein by insert molding, etc. 
     A detection plate of an ink end detection apparatus may be connected to a detection circuit and positioned so as to be in electrical communication with electrodes of a cartridge. The detection plate may be formed with microscopic asperities in areas brought into contact with the electrodes. The microscopic asperities may be formed of microscopic holes or microscopic grooves. 
     The invention also comprises an ink recorder cartridge for a recording apparatus containing a porous member adapted to hold ink and comprising paired electrodes for detecting the amount of ink remaining wherein one of the paired electrodes is embedded in a wall of an ink vessel formed of a thermoplastic material such as a synthetic resin material by insert molding so that it is exposed partially to an ink supply port formed in an ink supply section of the ink vessel. 
     An ink conducting hole smaller than the ink supply port may be formed in the electrode facing the ink supply port. A cylindrical boss may be formed extending along the periphery of the ink conducting hole of the electrode. 
     The invention also comprises an ink cartridge comprising a plurality of ink chambers containing porous materials therein capable of separately storing different color inks, wherein one of an associated pair of electrodes for detecting the depletion of ink is inserted into each of the plurality of ink chambers. 
     It is therefore a first object of the invention to provide an improved ink cartridge capable of precisely detecting the depletion of ink from an ink cartridge. 
     It is a second object of the invention to provide an ink cartridge which improves contact between the electrode pins and electrode plates. 
     It is a third object of the invention to provide an ink cartridge which decreases the number of parts and simplifies assembly. 
     It is a fourth object of the invention to provide an ink cartridge mounting device having a simple structure which insures safe, good printing It is a fifth object of the invention to provide a cartridge comprising electrodes which detect the depletion of ink with a high reliability. 
     It is a sixth object of the invention to provide a cartridge comprising a filter positioned in an ink supply section, the filter acting as an electrode for detecting the depletion of ink. 
     It is a seventh object of the invention to provide a cartridge capable of maintaining a good electrical connection between a filter and electrode. 
     It is an eighth object of the invention to provide a cartridge and detection plates which are maintained in electric conduction. 
     It is a ninth object of the invention to provide a cartridge comprising a filter acting as an electrode which decreases the spacing between a pair of electrodes, and thus enhances detection accuracy. 
     It is a tenth object of the invention to provide a cartridge not requiring any seal material for preventing ink leakage at the point the electrodes pass through the wall of the ink tank. 
     It is an eleventh object of the invention to provide a cartridge enabling ink to smoothly flow through an ink supply section which removes any restriction which might generate bubbles. 
     It is a twelfth object of the invention to provide a cartridge enabling ink to come into contact with electrodes over a wide contact area for accurate detection of the depletion of ink. 
     It is a thirteenth object of the invention to provide a cartridge having a simplified structure. 
     It is a fourteenth object of the invention to provide a cartridge having multiple ink vessels comprising at least one common electrode for at least two of the vessels for simplifying the structure and reducing the costs associated with construction. 
     The invention accordingly comprises the features of construction, combination of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims. 
     Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     For a fuller understanding of the invention, reference is had to the following description taken in connection with the accompanying drawings, in which: 
     FIG. 1 is a cross-sectional view of an ink cartridge constructed in accordance with a first embodiment of the invention; 
     FIG. 2 is a cross-sectional view of the ink cartridge of FIG. 1 taken in a direction orthogonal to the cross-section of FIG. 1 in part through the ink supply ports, in part through another portion of the cartridge; 
     FIG. 3 is a side elevational view of the ink cartridge in FIG. 1; 
     FIG. 4 is a cross-sectional view of an ink cartridge constructed in accordance with a second embodiment of the invention; 
     FIG. 5 is a cross-sectional view of an ink cartridge constructed in accordance with a third embodiment of the invention and a functional block diagram of a mounting device of the ink cartridge; 
     FIG. 6 is a cross-sectional view of the ink cartridge of FIG. 5 taken in a direction orthogonal to the cross-section of FIG. 5 in part through the ink supply ports, in part through another portion of the cartridge; 
     FIG. 7 is a side elevational view of the ink cartridge in FIG. 5; 
     FIG. 8 is a flowchart depicting the functioning of the ink cartridge of this third embodiment; 
     FIG. 9 is a cross-sectional view of an ink cartridge constructed in accordance with a fourth embodiment of the invention; 
     FIG. 10 is a cross-sectional view of an ink cartridge constructed in accordance with a fifth embodiment of the invention; 
     FIG. 11 is a cross-sectional view of an ink cartridge constructed in accordance with a sixth embodiment of the invention; 
     FIG. 12 is a bottom plan view of the ink cartridge of FIG. 11; 
     FIG. 13 is a cross-sectional view taken along line  13 — 13  in FIG. 12; 
     FIG. 14 is a cross-sectional view of an ink cartridge constructed in accordance with a seventh embodiment of the invention; 
     FIG. 15 is a side elevational view of the cartridge of FIG. 14; 
     FIG. 16 is a plan view of first and second detection plates as shown in FIG. 15; 
     FIG. 17 is a cross-sectional view of an ink cartridge constructed in accordance with an eighth embodiment of the invention; 
     FIG. 18 is a plan view of first and second detection plates constructed in accordance with a ninth embodiment of the invention; 
     FIG. 19 is a magnified plan view of a portion of first and second detection plates of FIG. 18; 
     FIG. 20 is a magnified plan view of a portion of alternatively constructed first and second detection plates of FIG. 18; 
     FIG. 21 is a cutaway cross-sectional view of an ink cartridge constructed in accordance with a tenth embodiment of the invention; 
     FIG. 22 is a cutaway cross-sectional view of an ink cartridge constructed in accordance with an eleventh embodiment of the invention; 
     FIG. 23 is a cross-sectional view of an ink cartridge constructed in accordance with a twelfth embodiment of the invention; 
     FIG. 24 is a bottom plan view of the ink cartridge of FIG. 23; 
     FIG. 25 is a cross-sectional view taken along line  25 — 25  of FIG. 24; 
     FIG. 26 is a fragmentary cross-sectional view of an ink cartridge constructed in accordance with a thirteenth embodiment of the invention; 
     FIG. 27 is a fragmentary cross-sectional view of an ink cartridge constructed in accordance with a fourteenth embodiment of the invention; 
     FIG. 28 is a cutaway cross-sectional side view of an ink cartridge constructed in accordance with a fifteenth embodiment of the invention; and 
     FIG. 29 is a cutaway cross-sectional side view of an ink cartridge constructed in accordance with a sixteenth embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The invention will be discussed based on embodiments shown in the accompanying drawings. Reference numerals are classified into a first group for the first to fifth embodiments, a second group for the sixth to eleventh embodiments, and a third group for the twelfth to sixteenth embodiments, like elements being denoted by like reference numerals. 
     Embodiment 1: 
     An ink cartridge, depicted generally as  1  and constructed in accordance with a first embodiment of the invention, is shown in FIGS. 1 to  3 . Ink cartridge  1  is formed so as to be able to store a different color ink separately in each of ink chambers  13 - 15 , which are separated by partitions  11  and  12 . A porous material  16  capable of holding the ink contained in each ink chamber  13 - 15  is positioned within each ink chamber  13 - 15 . An associated ink supply section  17  projects from the bottom of each of ink chambers  13 - 15 . The lower portion of each portion of porous material  16  is partially compressed by the associated ink supply section  17 , and forms a highly compressed area  16 A having an enhanced capillary force to aid in the supply of ink to the associated ink supply portion  17 . A filter  171  is positioned on the top of each ink supply section  17  through which ink can be supplied to an associated ink supply port  172  and further to an associated print head (not shown). Ink cartridge  1  is provided with a detection circuit  2  associated with each ink chamber  13 - 15  for detecting an amount of ink remaining in each ink chamber  13 - 15 . The ink level in each ink chamber  13 - 15  is decreased gradually in response to printing by the printer, When the ink remaining reaches a predetermined amount, the detector detects that the ink has been depleted from the ink tank. 
     Detection circuit  2  is formed as follows. A thick electrode support section  1 B is formed integral with a side wall  1 A of ink cartridge  1 . A pair of needle-like electrode pins  21  and  22  ( 22  not being shown in FIG. 1, but positioned behind pin  21  in FIG. 1) penetrate electrode support section  1 B into highly compressed portion  16 A of porous material  16  adjacent the top of filter  171 . Large-diameter bases  21 A and  22 A of the electrode pins  21  and  22  respectively are each supported by electrode support section  1 A in fluid-tight relation by a corresponding seal ring  23  fitted into a recess  1 C of electrode support section  1 B. The outer base ends of electrode pins  21  and  22  are pressed and maintained in contact with a pair of electrode plates  3  and  4  (only  3  being visible in FIGS. 1,  4  being positioned behind  3 ). 
     When ink cartridge  1  is mounted on a printer, electrode plates  3  and  4 , which comprise open ends of a detection circuit, are coupled to electrode pins  21  and  22 . When there is sufficient ink in cartridge  1  to conduct a printing operation, water-soluble ink is positioned between electrodes  21  and  22  and is used as an electric conductor. Thus, the detector senses the ink between the electrodes. If sufficient ink exists between electrode pins  21  and  22  and thus between electrode plates  3  and  4 , the ink detection circuit detects in a low resistance state between the electrode plates  3  and  4 , and it is determined that sufficient ink exists in the cartridge to perform a printing operation. As printing is conducted, the amount of ink in the ink chamber decreases and the electric resistance value between the electrode pins  21  and  22 , and thus the electrode plates  3  and  4 , increases. 
     Electrode pins  21  and  22  of ink cartridge  1 , which penetrate electrode support section  1 B into highly compressed section  16 A of the porous material  16 , are always maintained in extremely good contact with ink, since ink is concentrated at compression section  16 A. Thus, the detector can be expected to provide exceptional, highly reliable ink depletion detection capability. Since electrode pins  21  and  22  are formed as needles, electrode pins  21  and  22  can also easily penetrate electrode support section  1 B into porous material  16  for improving assembly efficiency. Additionally, if gold or silver or other noble metal material is used to form electrode pins  21  and  22 , conductivity can be improved. Finally, if electrode pins  21  and  22  are plated with gold or silver, costs can be decreased and conductivity improved. 
     In addition, when it becomes necessary to remove ink cartridge  1  from the printer head for maintenance, inspection, or the like, ink is maintained between electrode pins  21  and  22 . Thus, even if ink cartridge  1  is again mounted to the printer without special preparation, ink is maintained between electrode pins  21  and  22 , and thus a safe and continuous flow of ink can be provided without a false ink end indication. 
     Embodiment 2: 
     An ink cartridge, indicated generally as  100  and constructed in accordance with a second embodiment of the invention, is shown in FIG.  4 . Ink cartridge  100  differs from ink cartridge  1  of the first embodiment in that electrode pins  210 ,  220  are formed as thin needles having an equal cross-sectional area along their entire length. A base  210   a ,  220   a  of each of electrode pins  210 ,  220  penetrates a thick electrode support section  100 B of a side wall  100 A of ink cartridge  100 , and are supported in fluid-tight relation therewith by associated seal rings  230 . A free end of each electrode pin  210 ,  220  penetrates a porous member  160  and extends across almost the entire length of ink cartridge  100 , almost to a position in proximity to an opposed side wall  100 C opposite wall  100 A of ink cartridge  100 . Other components are similar to those of the ink cartridge  1  of the first embodiment. 
     Therefore, in accordance with this second embodiment of the invention, and as a function of ink cartridge  100 , long electrode pins  210  and  220  penetrate porous member  160  along almost the entire length of ink cartridge  100 , so that the contact area between electrode pins  210  and  220  and ink contained within ink cartridge  100  is increased, and is therefore more stable. Further, since electrode pins  210  and  220  are formed as thin needles, the contact area between electrode pins  210  and  220  and an electrode plate  310  is drastically reduced to a diameter equal to the cross-sectional area at the end of electrode pins  210  and  220 . Thus, even if the pressing pressure of an electrode plate  310  on electrode pins  210  and  220  is reduced, sufficient contract pressure can be provided between electrode pins  210  and  220  and electrode plate  310 , thus maintaining sufficient electrical contact therebetween. Thus, ink cartridge  100  provides a highly reliable ink depletion detection device. 
     Embodiment 3: 
     An ink cartridge, indicated generally as  400  and a mounting device  500  for mounting of ink cartridge  400 , constructed in accordance with a third embodiment of the invention, will be discussed, making reference to FIGS. 5 to  8 . 
     (1) Ink cartridge  400   
     Ink cartridge  400  is depicted generally in FIG. 5, and differs from ink cartridge  1  of the first embodiment in that a second electrode pin  420 , which is formed with a base  420   a  with a greater cross-sectional area than the tip  420   b , is positioned to penetrate a thick bottom wall  400 C of ink cartridge  400 . Tip  420   b  of second electrode pin  420  is placed so as to be positioned within an ink supply port  472  of an ink supply section  470 . The large-diameter base portion of second electrode pin  420  is sealed in fluid-tight relation by a seal ring  430 . Base portion  420   a  projects beyond the outer edge of ink cartridge  400  and is pressed into contact with an electrode plate  510 A,  510 B of mounting device  500  (described below). 
     Components similar to ink cartridge  1  of the first embodiment are indicated by similar reference numerals. 
     (2) Ink cartridge mounting device  500   
     As is further shown in FIG. 5, mounting device  500  for mounting ink cartridge  400  for use in a printer (P) comprising a printer head (PH), a suction pump (PU), etc., is electrically coupled to ink cartridge  400  through electrode plates  510 A,  510 B and electrode pins  410 ,  420 . Mounting device  500  is provided with an ink cartridge receiving section (not shown) for receiving ink cartridge  400  in a position at which electrode pins  410 ,  420  engage electrode plates  510 A,  510 B, and determination circuit  520  for determining whether or not ink remains in the ink tank, and therefore can be supplied in association with measurements received from electrode plates  510 A and  510 B. 
     Mounting device  500  further includes a display panel  530  equipped with a REMAIN display section  531  for indicating that sufficient ink remains in ink cartridge  400  and can be supplied for printing, an EMPTY display section  532  indicating that sufficient ink does not remain within ink cartridge  400 , or that some other ink problem, such as air mixed with the ink, requires that ink not be supplied for printing, and a replacement mode switch  533  used to allow replacement of ink cartridge  400 . The determination of whether sufficient ink is present in ink cartridge  400 , and therefore whether printing can take place, is made by determination circuit  520  based upon values received from electrode plates  510 A,  510 B, and electrode pins  410  and  420 . 
     (3) Mounting Procedure of Ink Cartridge  400   
     A procedure for mounting ink cartridge  400  will be discussed with reference to the flowchart shown in FIG.  8 . 
     Ink cartridge  400  is loaded into the printer (P). If electricity may be conducted between first and second electrode pins  410  and  420  because of ink positioned therebetween, it is determined that safe printing may take place, and printing by printer (P) is enabled. If the ink in ink cartridge  400  runs low, a high resistance value is measured between electrode pins  410  and  420  since no conductive liquid will be present between electrode pins  410 ,  420 , thereby, alerting the operator as to the necessity for replacing ink cartridge  400 , as in the other embodiments. 
     When an empty ink cartridge  400  is replaced with new ink cartridge  400 , during mounting air bubbles may be sucked into ink supply port  472 , and the print quality will degrade. Because of these air bubbles, electricity will not be conducted between first and second electrode pins  410  and  420 , and it is thus determined that there is no ink adjacent first and second electrode pins  410  and  420  and the ink detection device will indicate that the ink has been depleted from the ink tank. Thus, even if sufficient ink remains in ink cartridge  400 , the ink cartridge  400  cannot be used. 
     In order to remedy this state in which such air bubbles enter ink supply port  472 , a small amount of ink, and hopefully the air bubbles, is sucked from ink cartridge  400  and the air bubbles are removed. 
     Thus, during use, the operator operates replacement mode switch  533  for setting the switch to a replacement mode of ink cartridge  400  at step SP 1 . Next, ink cartridge  400  is replaced at step SP 2 . After ink cartridge  400  is properly mounted, suction pump (PU) is started sequentially for sucking a small amount of ink from ink cartridge  400  and extracting any air bubbles from ink supply port  472  at step SP 3 . 
     Next, determination circuit  520  compares the resistance measured between electrode pins  410 ,  420  with a predetermined resistance value at step SP 4 . If it is determined that the measured electrical resistance is less than the predetermined resistance value, determination circuit  520  confirms that the air bubbles have been removed from ink supply port  472  and that the portion of ink cartridge  400  adjacent first and second electrode pins  410  and  420  is filled with ink, REMAIN display section  531  is displayed, and print head (PH) stands by printing at step SP 5 . 
     However, if bubbles still remain within ink supply section  470 , EMPTY display section  532  is displayed at step SP 6  and control returns to step SP 3  at which ink is again sucked to remove any bubbles which have not yet been removed. Therefore, through the use of mounting device  500 , highly reliable printing can also be executed safely after ink cartridge  400  is loaded. 
     Embodiment 4: 
     An ink cartridge, indicated generally as  400   a  and constructed in accordance with a fourth embodiment of the invention, is shown in FIG.  9 . Ink cartridge  400   a  differs from ink cartridge  400  of the third embodiment shown in FIGS. 5 to  8  in that a first electrode pin  410   a  is disposed so as to penetrate across different color ink chambers  413   a ,  414   a , and  415   a  contiguous with each other for detecting the depletion of ink from any of the ink chambers. 
     As is shown in FIG. 9, the lack of sufficient ink in any of ink chambers  413   a ,  414   a , and  415   a  can be more accurately detected, and moreover the configuration of the detection circuit can be greatly simplified. Other components of this fourth embodiment are almost similar to those of the third embodiment and therefore are indicated by reference numerals with suffix a. 
     Embodiment 5: 
     An ink cartridge, indicated generally as  400   b  and constructed in accordance with a fifth embodiment of the invention, is shown in FIG.  10 . Ink cartridge  400   b  differs from the ink cartridge  400   a  of the fourth embodiment shown in FIG. 9 in that a second electrode pin  420   b  is disposed so as to penetrate across different color ink chambers  413   b ,  414   b , and  415   b  contiguous with each other for detecting the depletion of ink from any of the ink chambers. It has similar advantages to those of the ink cartridge  400   a  of the fourth embodiment. 
     Other components of the fifth embodiment which are similar to the components of prior embodiments are indicated by reference numerals in FIG. 9 to which suffix b is added. 
     Embodiment 6: 
     An ink cartridge, depicted generally as  1000  and constructed in accordance with a sixth embodiment of the invention, is shown in FIGS. 11 to  13 . Ink cartridge  1000  is a color ink cartridge comprising ink chambers  1011 — 1013  for storing ink. In a preferred embodiment, this ink may comprise three different color inks, yellow, magenta, cyan, or the like. Since the features of ink chambers  1011 — 1013  are in common of this description will refer to chamber  1012  only as a representative of ink chambers  1011 - 11013 . 
     Ink chamber  1012  contains a porous member  1021  therein. A filter  1023  formed of a conducting material is positioned on the top of an ink supply section  1022  projecting inward to the interior of ink chamber  1012 , as in conventional cartridges. 
     A first long electrode  1024  penetrates a side wall  1012 B and is positioned on a raised bottom  1012 A within chamber  1012  so at to be maintained in sufficient contact with porous member  1021 . An outer end of electrode  1024  extends through a seal ring B to the exterior of the cartridge. A U-shaped electric conductor  1026  is connected at a front end  1026   a  thereof to filter  1023 , is connected at a rear end  1026   c  thereof into elastic contact with the inner face of side wall  1012 B and is in turn brought at a center portion  1026   b  thereof into elastic contact with a second, short electrode  1025 . An outer end of electrode  1025  extends through a seal ring A to the exterior of the cartridge. Second electrode  1025  is positioned adjacent to first electrode  1024 , being separated therefrom by porous member  1021 . When cartridge  1000  is loaded into a printer (not shown) so as to face the ink head, power is supplied to first and second electrodes  1024  and  1025  by detection circuit  1200  of the printer. First and second electrodes  1024  and  1025  are brought into an electrically conductive state by means of ink contained in porous member  1021  adjacent first and second electrodes  1024  and  1025  in ink chamber  1012 . Any variance in the electric resistance value between first and second electrodes  1024  and  1025 , which varies according to a change in the remaining amount of ink, is detected by detection circuit  1200 . 
     The pores of filter  1023  generate a stronger capillary force than the capillary force generated by the portion of porous member  1021  adjacent filter  1021  As the ink in porous member  1021  is consumed and the amount of ink decreases, the electric resistance value between the first and second electrodes  1024  and  1025  grows. By measuring this electric resistance value, when the electric resistance reaches a predetermined value it can be precisely determined when the ink has been depleted from the ink tank. Porous member  1021  is loaded so that it is compressed to the greatest extent, and therefore has the maximum capillary force, in the proximity of the filter  1023 . Thus, the ink is guided stably into the area of porous member  1021  adjacent to filter  1023  until the ink is depleted from the ink cartridge. In this area adjacent filter  1023 , the existence of ink is detected by the first and second electrodes  1024  and  1025 . Because of this increased capillary force adjacent filter  1023 , the spacing between first and second electrodes  1024  and  1025  can be decreased while the depletion of ink from cartridge  1000  can be accurately detected. Thus, all of the ink in cartridge  1000  will be depleted before a new cartridge must be placed onto the printer. Thus, waste of ink is eliminated and high-quality printing can be provided for a longer time. 
     First electrode  1025  is electrically connected to filter  1023  via electric conductor  1026 . Filter  1023  serves a function as an electrode, and also generates a capillary force larger than porous member  1021  adjacent filter  1023 . Thus, even if cartridge  1000  is removed from the printer carelessly during the use, air will not flow into porous member  1021  through filter  1023 . Thus, ink cartridge  100  can be replaced in the printer without resulting in a false ink end reading because of air bubbles in the ink, and a print failure caused by an ink-out condition does not occur. 
     Porous member  1021  is therefore brought into contact with filter  1023  at a position at which ink and air do not mix, no air being able to enter ink cartridge  1012 . Thus, at least second electrode  1025  comes into reliable contact only with ink and not with air, and therefore the measured conduction resistance value is more stable. Thus, highly-reliable ink depletion detection can be insured. Further, as viewed from second electrode  1025 , electric conductor  1026  is brought into contact with filter  1023  by utilizing the compression force generated by porous member  1021 , so that the detection of the depletion of ink becomes more reliable. 
     First electrode  1024  is placed on raised bottom  1012 A. Porous member  1021  is compressed to a greater extent at the position of second electrode  1025 . Thus, the capillary force is at a maximum at the position of filter  1023 , where porous member  1021  is most compressed. Thus, a mistake in the detection of ink can be prevented during ink supply by precluding air bubbles from entering into ink cartridge  1000  when cartridge  1000  is loaded onto the printer. 
     The same description applies to the other different color ink chambers  1011  or  1012  of cartridge  1000  and therefore a detailed description of ink chambers  1011  and  1013  will not be provided. 
     Embodiment 7: 
     An ink cartridge, depicted generally as  1000   a  and constructed in accordance with a seventh embodiment of the invention, is shown in FIGS. 14 and 15. Ink cartridge  1000   a  differs from cartridge  1000  of the sixth embodiment in that first and second electrodes  1024   a  and  1025   a  each have outer an end portion L projecting from a side wall  1012 Ba of an ink chamber  1012   a . Each outer end portion L is formed with a bent structure, the inner face of an open end LE positioned abutting side wall  1012 Ba, whereby a biasing force is provided by portion L. The outer face of intermediate projection LM of each of the three first electrodes  1025   a  is brought into elastic contact with an arm of a first detection plate  1210   a  shaped like the letter “E”, the outer face of intermediate projection LM of each of the three second electrodes  1024   a  is brought into elastic contact with one of the arms of second detection plates  1220   a , each shaped like the letter “I” and positioned adjacent to an arm of first detection plate  1210   a  as shown in FIG. 16 in a detection circuit  1200   a . Other components are similar to those of the cartridge  1000 . 
     If an electrode  1024   a  or  1025   a  is deformed because cartridge  1000   a  is handled incorrectly and, for example, it is feared that the positioning of the electrode may be impaired, thus possibly disrupting the required electrical connection between the electrode and the detection plates, the biasing force of portion L can ensure contact between the electrode and detection plates. As a result, an erroneous determination that the ink has been depleted, caused by a contact failure between one of first and second electrodes  1024   a  and  1025   a  and the corresponding first or second detection plates  1210   a  or  1220   a  can be prevented. 
     If outer end part L becomes permanently deformed because it is handled incorrectly, cartridge  1000   a  can be replaced with a new cartridge, immediately solving the problem of contact failure. 
     Embodiment 8: 
     An ink cartridge, depicted generally as  1000   b  and constructed in accordance with an eighth embodiment of the invention, is shown in FIG.  17 . Ink cartridge  1000   b  differs from cartridge  1000  or  1000   a  in that a second electrode  1025   b  is formed completely of a fine mesh comprising a filter formed of a conductive material. Inner end portion IE of second electrode  1025   b  is embedded in a portion of an ink supply section  1022   b  opposing the top of ink supply section  1022   b . Intermediate portion ME of second electrode  125   b  is embedded in a bottom wall  1012 Ab of ink cartridge  1000   b . Outer end portion OE is bent upward in FIG.  17  and abuts the outer surface of a side wall  1012 Bb of ink cartridge  1000   b . When cartridge  1000   b  is manufactured, ink chamber  1012   b  and second electrode  1025   b , formed of mesh to form a filter, are molded in one piece by insert molding or the like. Ink supply section  1022   b  is formed with an enlarged projection EN for enlarging the contact area between ink supply section  1022   b  and with porous member  1021   b.    
     Therefore, when constructing cartridge  1000   b , the ink chamber  1012   b  and second electrode  1025   b  are molded in one piece by insert molding or the like. Electrode  1025   b  can therefore be attached to ink chamber  1012   b  so that ink leakage from the insertion point of the electrode can be prevented completely. Further, portion OE of second electrode  1025   b , which is formed of a mesh filter, is brought into contact with a detection plate  1310   b  of a printer. Thus, when cartridge  1000   b  is mounted, electrode  1025   b  is rubbed against detection plate  1310   b  during relative movement and fine dust, etc., deposited on the surface of the mesh filter material is removed, insuring good electric conductivity therebetween. Moreover, the dust, etc., is drawn into the mesh structure, serving a self-cleaning function. 
     Since ink supply section  1022   b  comprises enlarged projection EN, the portion of porous member  1021   b  which experiences the greatest compression can be expanded. Thus, the flow of ink through porous member  1021   b  can be maintained until the ink is completely depleted from the ink tank. Thus, much more of the ink from the ink tank ink can be supplied to a printer head for printing. 
     Embodiment 9: 
     First and second detection plates  1210   c  and  1220   c  are shown in FIGS. 18 to  20  and are constructed in accordance with a ninth embodiment of the invention. First and second detection plates  1210   c  and  1220   c  are similar to first and second detection plates  210   a  and  220   a  of the seventh embodiment in general structure. However they are formed with small holes SH formed on the surface thereof, as shown in FIG. 19, or with small cross grooves SS formed on the surface thereof, as shown in FIG.  20 . 
     Thus, the construction of first and second detection plates  1210   c  and  1220   c  with asperities (small holes SH or small cross grooves SS) formed on the surfaces thereof, locally increases the contract pressure with electrodes (not shown) on the raised portions of the plates for providing good electric conduction. Further, when the cartridge is mounted, both detection plates  1210   c  and  1220   c  rub against the electrodes and are vibrated. Thus, dust and the like which may be positioned between the electrodes and detection plates  1210   c  and  1220   c  is removed effectively. The electrical conduction between the electrodes and detection plates is insured, and a false detection ink depletion can be prevented. 
     Embodiment 10: 
     An ink cartridge, depicted generally as  1000   c  and constructed in accordance with a tenth embodiment of the invention, is shown in FIG.  21 . Ink cartridge  1000   c  differs from the ink cartridge  1000  of the sixth embodiment shown in FIG. 13 in that a first electrode  1024   c  is disposed so as to penetrate through different color ink chambers  1011   c ,  1012   c , and  1013   c  contiguous with each other for detecting the depletion of ink from any of the ink chambers. A second electrode  1025   c  extends orthogonally of first electrode  1024   c  and is electrically coupled to the corresponding filter  1023   c . According to this structure, the depletion of ink from any ink chambers  1011   c ,  1012   c , and  1013   c  can be detected without error, and moreover the configuration of the detection circuit can be simplified. 
     Other components of the tenth embodiment are similar to those of the sixth embodiment of FIG.  11  and therefore are indicated by reference numerals with suffix c. 
     Embodiment 11: 
     An ink cartridge, depicted generally as  1000   d  and constructed in accordance with an eleventh embodiment of the invention, is shown in FIG.  22 . Ink cartridge  1000   d  differs from ink cartridge  1000   c  of the tenth embodiment shown in FIG. 21 in that a second electrode  1025   d  is disposed so as to penetrate through different color ink chambers  1011   d ,  1012   d , and  1013   d  contiguous with each other for detecting the depletion of ink from any of the ink chambers. A first electrode  1024   d  extends orthogonally to second electrode  1025   d  in each chamber alongside each ink supply section. It has similar advantages to those of the ink cartridge  1   c  of the tenth embodiment. 
     Other components of the eleventh embodiment are indicated by reference numerals in the sixth embodiment of FIG. 11 to which suffix d is added. 
     Embodiment 12: 
     An ink cartridge, depicted generally as  2000  and constructed in accordance with a twelfth embodiment of the invention, is shown in FIGS. 23-25. Ink cartridge  2000  comprises a plurality of ink chambers  2011 , which, in a preferred embodiment are capable of separately storing different color inks of yellow, magenta, cyan, or the like. The construction of each of ink chambers  2011  are similar, and therefore are one ink vessel  2011  will be discussed as a representative of all ink chambers  2011 . 
     Ink chamber  2011  contains porous member  2012  therein for retaining ink and a filter  2014  positioned on top of an ink supply section  2013 , ink supply section  2013  projecting inward to the interior of ink cartridge  1000 , as in conventional cartridges. 
     Ink vessel  2011  is provided with a pair of electrodes  2015 ,  2016  for detecting the amount of ink remaining in ink chamber  2011 . First long electrode  2015  has an inner end portion  2015   c  which extends substantially to the center of ink chamber  2011  so that it is maintained in sufficient contact with porous member  2012 . First electrode  2015  is formed with a base  2015   a  embedded in a raised bottom  2011 A of ink chamber  2011  by insert molding, and an outer end portion  2015   b , which is exposed to the outside of ink chamber  2011 . A second short electrode  2016  is positioned adjacent first electrode  2015  has a base  2016   a  embedded in the raised bottom  2011 A, which is formed by insert molding similar to first electrode  2015 , and an inner end portion  2016   c  exposed to an ink supply port  2013 A of an ink supply section  2013 . Inner end portion  2016   c  is positioned to be able to come into contact with ink in ink supply port  2013 A. If ink cartridge  2000  is loaded into a print head of a printer (not shown) so as to face the ink jet print head, first and second electrodes  2015  and  2016  are energized through detection plates (CP) by detection circuit (CC) of the printer and electricity is conducted therebetween by using ink retained within porous member  2012  in ink chamber  2011  as a conductive medium. The electric resistance value between first and second electrodes  2015  and  2016  varies with a change in the amount of ink remaining in ink chamber  2011 . This variance in the electrical resistance is detected by detection circuit (CC). 
     As the ink in porous member  2012  is consumed, and the ink level decreases, the electric resistance value between first and second electrodes  2015  and  2016  increases. When the electric resistance value increases above a predetermined value, the depletion of ink from ink vessel can be detected. The ink flows through ink supply hole  2013 A and comes into contact with inner portion  2016   c  of second electrode  2016  without being obstructed by second electrode  2016 . Thus, bubbles are not generated in the ink and the ink is circulated with a regulated flow, so that the electrical resistance value between first and second electrodes  2015  and  2016  can be precisely measured for stable and accurate detection of the depletion of ink. 
     Therefore, cartridge  2000  will not be replaced with a new cartridge when ink still remains in cartridge  2000 . Thus, the waste of ink is avoided and high-quality printing can be performed for a longer time. 
     Embodiment 13: 
     An ink cartridge, depicted generally as  3000  and constructed in accordance with a thirteenth embodiment of the invention, is shown in FIG. 26, only the ink supply portion thereof being shown. Ink cartridge  3000  differs from ink cartridge  2000  in that a second electrode  3116  has an intermediate area that extends across an ink supply port  3130 A, and is therefore exposed in a traverse manner in ink supply port  3130 A of an ink supply section  3130 . An ink conducting through hole  3116 A, smaller than ink supply port  3130 A is formed in second electrode  3116 . A base  3116 B and an inner end portion  3116 C are embedded in a raised bottom  3110 A by insert molding. Other components and the procedure of abutting a detection plate (CP) against an L-shaped outer end of the second electrode are similar to those of the cartridge  1000  of the sixth embodiment. A first electrode  3115  extends into each chamber along bottom wall  3110 A. 
     During use of cartridge  3000 , ink is passed through a filter  3140 , and is then passed through ink conducting hole  3116 A of second electrode  3116 , positioned within ink supply port  3130 A for supplying the ink to a printer. Ink comes into contact with second electrode  3116  on the top face of second electrode  3116 , along the inner face of ink conducting hole  3116 A, and the bottom face of second electrode  3116 . Thus, the amount of ink remaining in ink cartridge  3000  can be accurately detected. 
     Embodiment 14: 
     An ink cartridge, depicted generally as  200  and constructed in accordance with a fourteenth embodiment of the invention, is shown in FIG. 27, only the ink supply portion thereof being shown. Ink cartridge  200  differs from the cartridge  2000  or  3000  in that an ink conducting hole  216 A is formed in a second electrode  216 , and that ink conducting hole  216 A is formed integrally with a cylindrical boss  216 B extending toward the exterior end of ink supply section  4130 . Other components are similar to those of ink cartridge  100  of the thirteenth embodiment. 
     That is, during use of cartridge  200 , contact between the second electrode  216  and ink occurs over a wide range of the top face of the electrode  216 , the wide inner cylindrical face of ink conducting hole  216 A and the cylindrical boss  216 B, and the bottom face of electrode  216  defined by the end of base  216 B. Thus, the contact area between ink and second electrode  216  is furthermore increased and the depletion of ink from an ink cartridge  200  can be accurately detected. Cartridge  200  has effects similar to those of other embodiments. 
     The same description goes for other ink vessels provided with multi-color cartridge and therefore these additional ink vessels will not be discussed. 
     Embodiment 15: 
     An ink cartridge, depicted generally as  100   a  and constructed in accordance with a fifteenth embodiment of the invention, is shown in FIG.  28 . Ink cartridge  100   a  differs from ink cartridge  2000  of the twelfth embodiment shown in FIG. 23 in that a first electrode  15   a  is disposed so as to penetrate through different color ink chambers  11   a  contiguous with each other for detecting the depletion of ink from any of ink chambers  11   a . One second electrode  16   a  associated with each ink chamber is positioned within each ink chamber in a direction orthogonal to said first electrode  15   a , each passing through an associated ink supply section and ink supply port. 
     According to this structure, the depletion of ink in any of ink chambers  11   a  can be detected without error and the configuration of the detection circuit can be simplified. 
     Other components of the fifteenth embodiment are almost similar to those of the fourteenth embodiment and therefore are indicated by reference numerals with suffix a. 
     Embodiment 16: 
     An ink cartridge, depicted generally as  100   b  and constructed in accordance with a sixteenth embodiment of the invention, is shown in FIG.  29 . Ink cartridge  100   b  differs from the ink cartridge  100   a  of the fifteenth embodiment shown in FIG. 28 in that a second electrode  16   b  is disposed so as to penetrate through different color ink chambers  11   b  contiguous with each other for detecting the depletion of ink from any of ink chambers  11   b . A first electrode  15   b  associated with each ink chamber is positioned within each ink chamber in a direction orthogonal to said second electrode, each first electrode being embedded in a portion of the wall of said ink cartridge  100   a . It has similar advantages to those of the ink cartridge  100   a  of the fifteenth embodiment. 
     Other components of the sixteenth embodiment are indicated by reference numerals in FIG. 28 to which suffix b is added. 
     As a result of the invention, the depletion of ink from an ink cartridge can be detected with high accuracy and high-quality printing can be insured. Since the ink cartridge has a small number of components, it can be manufactured easily at low cost. Contact between the electrode pins and the electrode plates can be provided upon insertion of the ink cartridge in a printer. After a porous material is loaded into the ink cartridge, the electrode pins are made to penetrate the porous material, whereby assembly is facilitated. When the ink cartridge is replaced, printing can be continued by easy operation without disturbance. Since the filter may be used as one of the detection electrodes, the amount of ink remaining in the ink cartridge can be detected with high accuracy. Since the filter acts as an electrode, the spacing between the pair of electrodes is decreased, and the detection accuracy of the depletion of ink can be improved. Since the filter generates a larger capillary force than the compressed porous material in the ink tank adjacent the filter, all of the ink in the ink cartridge can be precisely detected and thus supplied for printing. Since the filter and porous material come into reliable contact with each other, the amount of ink remaining in the ink tank can be precisely detected. Since the filter or detection electrode may be formed having a coarse surface, good contact therebetween is provided and the remaining amount of ink can be precisely detected. Since the electrode may be embedded in the ink vessel by insert molding, a cartridge of a simple structure capable of sufficiently preventing ink leakage without the need for seals is provided. 
     In the invention, a cartridge is provided wherein ink can be supplied smoothly so as to prevent bubbles from occurring in the ink supply port, and good electrical contact between ink and an electrode is provided for preventing a false indication that the ink has been depleted from the ink tank. 
     In the invention a cartridge is provided wherein ink can be circulated smoothly in a boss constructed following an ink conducting hole formed in an electrode, and ink and the electrode are brought into contact with each other over an extremely wide area for aiding in further precisely detecting the depletion of ink. Since at least one electrode can be formed to pass through a plurality of ink chambers, the depletion of ink in any of the chambers can be detected, and the ink tank and detection production structure can be simplified and costs can be reduced. 
     It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the above constructions without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. 
     It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween