Patent Publication Number: US-6908182-B2

Title: Ink cartridge and ink jet printer

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to an ink cartridge used as an ink supply source of an ink jet printer and, in particular, to an ink cartridge comprising a configuration adequate for recycling and a configuration adequate for miniaturization. The present invention also relates to an ink jet printer using the above-described ink cartridge. 
   2. Description of the Related Art 
   A known ink supply mechanism of an ink jet printer is as follows An ink supply needle is placed in an ink cartridge placement part formed in an ink jet printer and, if an ink cartridge is placed so that the ink supply needle is inserted into an ink outlet formed in the ink cartridge, ink stored in the ink cartridge can be supplied to an ink jet head of the ink jet printer. 
   The ink cartridges used with such an ink jet printer are disclosed in JP-A-63-116833, JP-A-5-162333, JP-A-11-70672, etc. For example, the ink cartridge disclosed in JP-A-11-70672 comprises a cartridge case housing an ink back and a waste-ink absorption material, and a detection plate—for detecting when the amount of ink, remaining in the ink bag, gets low—is attached to the ink bag. 
   Some ink jet printers require two or more ink cartridges. For example, ink cartridges housing ink bags storing different color inks need to be placed in an ink jet printer for executing color printing. 
   However, if two ink cartridges are placed in the ink jet printer, it becomes cumbersome to attach and detach the ink cartridges and the ink cartridge placement part is upsized. 
   Thus, to simplify the ink cartridge placement operation and miniaturize the ink cartridge placement part, an ink cartridge housing two or more ink bags may be used. In this case, to make it possible to house the ink bags at the determined positions, and possible precisely to detect the amount of ink remaining in each ink bag by means of a detection plate attached thereto, the cartridge case may be divided into two partitions by a partition plate so that the ink bags separately are housed in the partitions. 
   However, to use the ink cartridge housing a plurality of ink bags, if any one of the ink bags becomes empty of ink, the ink cartridge needs to be replaced regardless of how much ink remains in any other ink bag. Therefore, it is extremely uneconomical to replace the ink cartridge if a large amount of ink remains in any ink bag other than the empty one. Generally, black ink is consumed in larger quantities than is colored ink and, thus, the ink cartridge must be replaced without entirely consuming the colored ink. 
   On the other hand, in recent years, for environmental protection, it has been desired that in so far as possible an ink cartridge be made up of recyclable parts. From this viewpoint, to recycle a cartridge case, it is desired that the cartridge case designed for easy disassembling. 
   SUMMARY OF THE INVENTION 
   It is an object of the invention to provide an ink cartridge comprising a plurality of ink bags advantageous for miniaturization. 
   It is another object of the invention to provide an ink cartridge comprising a plurality of ink bags intended to facilitate disassembly work at recycling time. 
   It is still another object of the invention to provide an ink cartridge comprising a plurality of ink bags advantageous for miniaturization, wherein ink outlets of the ink bags can be positioned reliably. 
   It is still yet another object of the invention to provide an ink cartridge comprising a plurality of ink bags that can be easily attached and detached from one another. 
   It is a further object of the invention to provide an ink cartridge comprising a plurality of ink bags intended for reducing waste-ink in the ink bags. 
   On the other hand, it is an object of the invention to provide an ink jet recorder using such a new ink cartridge as an ink supply source. 
   To accomplish the above-mentioned and other objects, according to the invention there is provided an ink cartridge including: 
   a cartridge main body having a first case and a second case joined to the first case; 
   at least first and second ink bags, each having a bag main body storing ink, and an outlet through which the ink can be discharged from the bag main body, one or a plurality of the ink bags being housed in either or both of the first case and the second case, 
   wherein when the first case and the second case are joined, the outlets of the first and second ink bags are pressed against each other by the first case and the second case. 
   Generally, the outer size of the ink outlet is larger than the thickness of the bag main body when the ink bag is filled with ink. Therefore, if the ink outlet parts are stacked in the case thickness direction so that they contact one another, the thickness of the ink cartridge can be reduced. This structure is particularly advantageous for miniaturization of an ink cartridge in which three or more ink bags are housed. 
   As one method for providing such an ink cartridge, the first case may be a case main body having a bottom plate portion and a side plate portion with an opening on its top for housing the first and second ink bags. Further, the second case may be a case lid for covering the opening of the case main body. In this case, the ink outlet parts are stacked in the case thickness direction without intervention of a partition plate, and the thickness of the ink cartridge can be reduced as much as the thickness of the partition plate. 
   In addition to the above-described configuration, it is also effective that a partition plate, for separating the housing space of the first ink bag and the housing space of the second ink bag, is attached to a predetermined position of the case main body. In this case, the partition plate prevents the first ink bag and the second ink bag from interfering with each other. Thus, a failure wherein ink flows out from the lower ink bag because the weight of the upper ink bag presses the lower ink bag, for example, or the like, can be prevented. 
   It is desirable that the partition plate be placed movably in the thickness direction of the case main body along the side plate portion and the case main body, and that the case lid comprise partition plate clamp faces for defining the position of the partition plate by clamping the partition plate. 
   According to the above configuration, the partition plate does not mechanically engage the case main body as like a snap-fit, etc. Therefore, in disassembly at recycling time, the partition plate can be easily detached from the case main body after the case lid is opened. Also, at assembly time, the partition plate may be simply dropped inside the case main body through the upper opening thereof. 
   Further, it is desirable that a waste-ink holding member, for storing waste ink poured therein from the outside, be attached to the case lid. According to this configuration, when the maximum amount of waste ink is stored, only the case lid may need to be replaced. 
   To fix the ink outlets of the ink bags to determined positions, the case main body and the case lid may comprise ink outlet clamp faces that define the positions of the ink outlets by clamping the ink outlets in stacked relation on each other. In this case, to make it possible to reliably clamp the ink outlets without rattle, it is desirable that at least one of the ink outlet clamp faces be made elastically displaceable. 
   Next, to reliably fix the partition plate to a predetermined position, the ink outlet of each ink bag may be used to fix the partition plate. That is, it is desirable that each ink outlet should comprise a partition plate clamp face for defining the position of the partition plate. 
   In this case, it is desirable that each of the ink outlets comprise a portion (stacked in the case thickness direction without intervention of the partition plate) and a partition plate clamp portion (stacked in a state in which a part of the partition plate is clamped), and that the partition plate clamp face should be formed in the partition plate clamp portion. In doing so, the partition plate can be reliably fixed, and the thickness of the ink cartridge can be reduced by as much as the thickness of the partition plate. 
   The ink cartridge of the invention can adopt a configuration in which each of the first and second ink bags has a detection plate that moves in the ink cartridge thickness direction in response to the amount of ink remaining in the corresponding ink bag. Further, first and second detection projections are extended in the thickness direction, of the bag main body, from the side margins of the first and second detection plates, wherein the detection projections and have tips projected from the rear of the case main body as the amounts of ink remaining in the first and second ink bags decrease. Moreover, the first and second detection projections differ from each other at least in shape or color. 
   On the other hand, the ink cartridge of the invention is characterized by the fact that the first case is a first ink cartridge for housing the first ink bag and the second case is a second ink cartridge for housing the second ink bag. The invention further comprising a joint mechanism fordetachably joining the first ink cartridge and the second ink cartridge. 
   According to this configuration, the ink cartridge of the invention comprises at least two ink cartridges detachably formed into one piece. Therefore, the cartridges can be attached to or detached from a cartridge placement section of an ink jet printer by one operation as with a single ink cartridge. If one ink cartridge becomes empty of ink, only the ink cartridge which becomes empty of ink need be replaced, so that the waste of ink can be eliminated. 
   The first ink cartridge can comprise the waste-ink holding member for storing waste ink in the first ink cartridge. 
   The joint mechanism can have snap fit parts formed in a side portion of the first ink cartridge and a side portion of the second ink cartridge. 
   According to the joint mechanism, both ink cartridges are overlaid and snap-fitted, whereby they can be joined easily. If the snap-fit part is thus formed in the side portion of the ink cartridge, the snap fit part is not directly grasped when the ink cartridge is handled. 
   The ink cartridge is pushed toward the front end face, whereby it is placed in the cartridge placement section of the ink jet printer. Thus, to prevent the first and second ink cartridges from shifting back and forth at the placement or removal time, it is desirable that the second ink cartridge be formed with a recess into which the first ink cartridge can be fitted in the thickness direction thereof, and that the first ink cartridge be placed in the recess. 
   Next, to detect a small amount of ink remaining in each ink bag, first and second detection plates—each moved in the thickness direction of the bag main body in response to the amount of ink remaining in the ink bag—may be attached to the first and second ink bags. Additionally, first and second detection projections may be extended in the thickness direction of the bag main body from the side margins of the first and second detection plates. Further, the detection projections may have tips projected from the rear of the second ink cartridge as the amounts of ink remaining in the first and second ink bags are reduced. 
   In this case, if either of the detection projections is projected from the rear of the ink cartridge, and the ink cartridge empty of ink is detected, to make it possible to immediately check which cartridge is empty of ink—by visual inspection of the detection projection of the ink cartridge after removing the cartridge from the cartridge placement section of the ink jet printer—it is desirable that the first and second detection projections differ from each other at least in shape or color. 
   It is effective to form the first ink cartridge with a side portion having a protection guide surrounding the first detection projection so that the detection projection is not broken or deformed when the first ink cartridge is not coupled to a second one. 
   To detect an ink-end condition with good accuracy, and to decrease the amount of ink remaining in the ink bag in the ink-end condition, it is desirable that the following configuration should be adopted: 
   First: the first and second detection plates are put on surfaces of the bag main bodies of the first and second ink bags, and the plane form of each detection plate overlapping the corresponding bag main body is rectangular; the width dimension of each detection plate—as measured in a direction along the side where the ink outlets of the first and second ink bags are attached—is a value within the range of 0.5 to 1.0 times the width dimension of the corresponding ink bag measured in the direction along the side where the ink outlets of the first and second ink bags are attached; and the length dimension of each detection plate is a value within the range of 0.4 to 0.8 times the length dimension of each ink bag. 
   Further, the ratio between: (i) the ratio between the lateral dimension of each detection plate and the lateral dimension of each ink bag; and (ii) the ratio between the longitudinal dimension of each detection plate and the longitudinal dimension of each ink bag, is within the range of 0.8 to 1.2. 
   Next, in the ink cartridge of the invention, it is desirable that the ink bag storing black ink, which is generally used most often, should be housed in the second ink cartridge having a larger capacity. And it is desirable that the ink bag of colored ink, which is relatively less often used, should be housed in the first ink cartridge having a smaller capacity as it also contains the waste-ink holding member. 
   Thus, according to the invention, ink cartridges are miniaturized, whereby the ink cartridge placement section can also be miniaturized, and it is made possible to provide a small-sized ink jet printer. 
   Also, according to the invention, there is provided an ink jet printer comprising; 
   an ink cartridge comprising a plurality of ink cartridges at least including a first ink cartridge for housing a first ink bag storing first ink and a second ink cartridge for housing a second ink bag storing second ink of a different color than the first ink and including an ink cartridge comprising a waste-ink holding member for storing waste ink poured therein from the outside, the plurality of ink cartridges being formed in one piece by a joint mechanism for detachably joining the plurality of ink cartridges; 
   a placement section in which the ink cartridge detachably is placed; and 
   an ink jet head comprising a plurality of ink nozzle groups including a first ink nozzle group for ejecting the ink in the first ink bag of the ink cartridge placed in the placement section, and a second ink nozzle group for ejecting the ink in the second ink bag of the ink cartridge placed in the placement section for executing any desired printing on record paper relatively moved, 
   wherein the waste-ink holding member is placed in the cartridge having the smallest value resulting from dividing the amount of ink in the ink bag housed in each ink cartridge by the number of nozzles of the ink nozzle group corresponding to the ink bag. 
   According to this configuration, the ink cartridge having a low probability of use is provided with the waste-ink holding member, so that the capacity of the waste-ink holding member can be used effectively. Also, the volume of the ink cartridge placement section can be reduced and the ink jet printer can be miniaturized as compared with the case where every ink cartridge includes a waste-ink holding portion. 
   It is desirable that the waste-ink holding member have a holding capacity in the range of 1 to 1.3 times a capacity found by multiplying: (i) the volume of ink available to the ink jet head as the amount of ink stored in the ink cartridge in which the waste-ink holding member is placed; by (ii) the total number of nozzles contained in the plurality of ink nozzle groups divided by the number of the ink nozzle groups for ejecting ink from the ink cartridge having the waste-ink holding member. According to this configuration, the waste-ink holding member becomes a small-sized waste-ink holding member capable of reliably preventing waste ink from leaking. Therefore, the volume of the ink cartridge is reduced, and the volume of the ink cartridge replacement section is reduced, whereby the ink jet printer can be miniaturized. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects and advantages of the present invention will become more apparent by describing in detail preferred exemplary embodiments thereof with reference to the accompanying drawings, wherein like reference numerals designate like or corresponding parts throughout the several views, and wherein: 
       FIG. 1  is an external perspective view of an ink cartridge with a partition plate according to an embodiment of the invention when the ink cartridge is viewed from the top; 
       FIG. 2  is an external perspective view of the ink cartridge in  FIG. 1  when the ink cartridge is viewed from the bottom; 
       FIG. 3  is a longitudinal sectional view of the ink cartridge in  FIG. 1 ; 
       FIG. 4  is a transverse sectional view of the ink cartridge in  FIG. 1 ; 
       FIG. 5  is an exploded perspective view of the ink cartridge in  FIG. 1 ; 
       FIG. 6  is a fragmentary sectional view showing a snap fit portion of a case main body and a case lid of the ink cartridge in  FIG. 1 ; 
       FIG. 7  is a schematic representation showing a fix structure of an ink outlet of the ink cartridge in  FIG. 1 ; 
       FIG. 8  is a schematic representation to describe the relationship between the contour shapes of an ink bag and a detection plate in the ink cartridge in  FIG. 1 ; 
       FIG. 9  is an exploded perspective view showing a second embodiment of an ink cartridge with a partition plate of the invention; 
       FIG. 10  is a transverse sectional view of the ink cartridge in  FIG. 9 ; 
       FIG. 11  is a schematic configuration drawing showing ink supply and discharge channels of an ink jet printer in which the ink cartridge in  FIG. 1  is placed; 
       FIG. 12  is a schematic representation showing an ink end detection mechanism attached to an ink cartridge placement section in  FIG. 11 ; 
       FIG. 13  is a schematic block diagram showing a control system of the ink jet printer in  FIG. 11 ; 
       FIG. 14  is a schematic block diagram showing another example of the controller in  FIG. 13 ; 
       FIG. 15  is a schematic configuration drawing showing ink supply and discharge channels of an ink jet printer in which the ink cartridge in  FIG. 9  can be placed; 
       FIG. 16  is a schematic representation showing an ink end detection mechanism in the ink jet printer in  FIG. 15 ; 
       FIG. 17  is a schematic block diagram showing a control system of the ink jet printer in  FIG. 15 ; 
       FIG. 18  is an external perspective view of a split-type ink cartridge of another embodiment of the invention when the ink cartridge is viewed from the top; 
       FIG. 19  is an external perspective view of the ink cartridge in  FIG. 18  when the ink cartridge is viewed from the bottom; 
       FIG. 20  is a longitudinal sectional view of the ink cartridge in  FIG. 18 ; 
       FIG. 21  is an exploded perspective view of the ink cartridge in  FIG. 18 ; 
       FIG. 22  is a perspective view showing the operation of joining first and second ink cartridges of the ink cartridge in  FIG. 18 ; 
       FIG. 23  is a perspective view of the first ink cartridge shown in  FIG. 18  when the ink cartridge is viewed from the top; 
       FIG. 24  is a perspective view of the first ink cartridge shown in  FIG. 18  when the ink cartridge is viewed from the bottom; 
       FIG. 25  is a longitudinal sectional view of the first ink cartridge shown in  FIG. 18 ; 
       FIG. 26  is a perspective view of the second ink cartridge shown in  FIG. 18  when the ink cartridge is viewed from the top; 
       FIG. 27  is a perspective view of the second ink cartridge shown in  FIG. 18  when the ink cartridge is viewed from the bottom; 
       FIG. 28  is a longitudinal sectional view of the second ink cartridge shown in  FIG. 18 ; and 
       FIG. 29  is a schematic configuration drawing to show ink supply and collection channels of an ink jet printer using the ink cartridge in  FIG. 18  as an ink supply source. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring now to the accompanying drawings, there are shown preferred embodiments of ink cartridges incorporating the invention and ink jet printers using the ink cartridges as ink supply sources. 
   First Embodiment—an Ink Cartridge having a Partition Plate 
     FIG. 1  is an external perspective view of an ink cartridge with a partition plate according to an embodiment of the invention when the ink cartridge is viewed from the top.  FIG. 2  is an external perspective view of the ink cartridge when the ink cartridge is viewed from the bottom.  FIG. 3  is a longitudinal sectional view of the ink cartridge.  FIG. 4  is a transverse sectional view of the ink cartridge.  FIG. 5  is an exploded perspective view of the ink cartridge.  FIG. 6  is a fragmentary sectional view showing a joint structure of a case main body and a case lid of a cartridge case.  FIG. 7  is a schematic representation showing a structure by which ink outlets of ink bags are fixedly housed. 
   As shown in the figures, an ink cartridge  1  comprises a cartridge case  2  shaped like a fiat rectangular parallelepiped, first and second ink bags  3 ( 1 ) and  3 ( 2 ) housed in the cartridge case  2 , a partition plate  4  placed between the ink bags, and a waste-ink absorption material  5 . 
   First, the ink bags  3 ( 1 ) and  3 ( 2 ) are of the same structure and, therefore, only one ink bag  3 ( 1 ) will be discussed. Parts of the ink bag  3 ( 2 ) corresponding to those of the ink bag  3 ( 1 ) are denoted by the same reference numerals and will not be discussed again. The ink bag  3 ( 1 ) is formed of a flexible material such as, for example, an aluminum laminate film comprising aluminum foil sandwiched between two films, wherein a nylon film is the outer film and a polyethylene film is the inner film for enhancing a gas barrier property. 
   In the example shown in the figures, two aluminum laminate films are put on each other and are jointed around their peripheries by a method of heat sealing, or the like, whereby a bag main body portion  6  of the ink bag  3 ( 1 ) is formed. An ink outlet part  7 , for taking ink out of the ink bag in which it is stored, is attached to the front margin center of the bag main body portion  6  by a method of heat sealing, or the like. 
   The above-described ink bag  3 ( 1 ) has its ink outlet part  7  fixed to the front part of the cartridge case  2 , and its bag main body portion  6  fixed to the cartridge case  2  with a double-faced adhesive, or the like. The other ink bag  3 ( 2 ) has its ink outlet part  7  fixed to the front part of the partition plate  4 , and its bag main body portion  6  fixed to the partition plate  4  with a double-faced adhesive, or the like. 
   A detection plate  8  is fixed to the ink bag  3 ( 1 ) by, for example, double-faced tape (not shown). The detection plate  8  is provided for detecting when the amount of ink remaining in the ink bag  3 ( 1 ) decreases to a predetermined amount. A detection projection  9  is formed on the detection plate  8  so that it is capable of projecting to the outside from an opening  11  made in the bottom of the cartridge case  2 . The amount of projection is increased with a decrease in the amount of ink remaining and, when the projection amount of the detection projection  9  becomes equal to or greater than a determined amount, the detection projection  9 , is detected by an ink end detection mechanism (not shown) so that it is known when ink runs out. 
   Next, the cartridge case  2  will be described. The cartridge case  2  includes a case main body  12  open on its top (i.e., having opening  13 ) and a case lid  14  detachably covering the upper opening  13 . The front  15  of the cartridge case  2  is formed with ink supply needle insertion holes  16  and  17 , and a waste-ink collection needle insertion hole  18 . The bottom of the cartridge case  2  is formed with the above-described opening  11 . If the ink bag  3 ( 1 ),  3 ( 2 ) contained in the cartridge case  2  becomes empty of ink, the detection projection  9  projects from the opening  11  so that it can be, detected when the ink runs out. Three circular holes  19 ,  20 , and  21 , are made in the cartridge case front  15 . The holes  19 ,  20 ,  21 , are used for positioning the cartridge  1  when it is placed in a cartridge placement part formed in an ink jet printer, as described later. 
   In the cartridge case  2 , in order from the bottom, the first ink bag  3 ( 1 ), the partition plate  4 , the second ink bag  3 ( 2 ), and the waste-ink absorption material  5  are arranged in a case thickness direction  2 V. See FIG.  3 . 
   Next, the detailed structures of the parts of the ink cartridge  1  will be discussed. First, the case main body  12 , which forms a part of the cartridge case  2 , comprises a rectangular bottom plate portion  22  and a front wall portion  23 , left and right side wall portions  24  and  25 , and a rear wall portion  26 , wherein the wall portions are formed as side plate portions rising upright from four peripheral margins of the bottom plate portion  22 . Additionally, the case main body  12  has the opening  13  on its top. The opening  11 , for detecting the detection projection, is made in the bottom plate portion  22 . Further, an inclined part  27 , which is inclined to the case top, is formed in the rear portion and is contiguous to the rear wall portion  26 . 
   The front wall portion  23 , the left and right side wall portions  24  and  25 , and the rear wall portion  26 , are formed on inner surfaces with a plurality of ribs  31 ,  32 ,  33 , and  34 . Upper end faces of the ribs (also called partition plate clamp faces)  31   a ,  32   a , 33   a , and  34   a  are at the same height, thereby determining the position of the partition plate  4  in the cartridge case  2 . 
   The case lid  14 , which covers the upper opening  13  of the case main body  12 , comprises a rectangular lid main body portion  35 , an outer frame portion  36  formed in the four peripheral margins of the lid main body portion  35 , and a rectangular inner frame portion  37  formed inside the outer frame portion  36 . The outer frame portion  36  is formed on its outer surface with a step part  38  notched inside. The upper end parts of the front wall portion  23 , the side wall portions  24  and  25 , and the rear wall portion  26  of the case main body  12  are fitted into the step part  38  from the lower side. An end face  39  of the outer frame portion  36  functions as a partition plate clamp face for pressing the partition plate  4  against the rib upper end faces (also called partition plate clamp faces)  31   a ,  32   a ,  33   a , and  34   a  formed in the case main body  12  from the upper side. 
   The inner frame portion  37  is taller than the outer frame portion  36 , and the waste-ink absorption material  5  is housed inside the inner frame portion  37 . Further, the waste-ink absorption material  5  is scaled in the inner frame portion  37  with a rectangular plastic film  41  put on the end face of the inner frame portion  37 . 
   The joint structure of the case main body  12  and the case lid  14  will now be discussed. In this embodiment, the case lid  14  is detachably attached to the case main body  12  according to a snap-fit structure. That is, left and right insertion claws  43  and  44  are formed on, and are projected forward from, a front wall portion  42  of the outer frame portion  36  of the case lid  14 . Insertion holes  45  and  46 , into which the claws  43  and  44  can be inserted from the rear, are made in the upper end portion of the front wall portion  23  of the case main body  12 . 
   On the other hand, as seen in  FIG. 6 , left and right side-wall portions  47  and  48  on the inner frame portion  37  of the case lid  14 , are formed with engagement claws  49  and  50  of to snap-fit type, wherein the engagement claws  49  and  50  are projected outward. Engagement grooves  51  and  52 , into which the engagement claws  49  and  50  can be fitted, arc formed at corresponding positions on the inner surfaces of the left and right side wall portions  24  and  25  of the case main body  12 . 
   If the claws  43  and  44 , on the front of the case lid  14 , are inserted into the insertion holes  45  and  46  of the case main body  12 , and then the rear portion of the case lid  14  is pushed into the opening  13  of the case main body  12  from the upper side, the left and right side wall portions  24  and  25  of the case main body  12  are elastically displaced and slightly widen so that the engagement claws  49  and  50  can be fitted into the engagement grooves  51  and  52 . When the engagement claws  49  and  50  are fitted into the engagement grooves  51  and  52 , the left and right side wall portions  24  and  25  arc elastically restored so that the case lid  14  is attached to the case main body  12 . 
   To detach the case lid  14 , a jig such as a screwdriver may be inserted into a gap G between the sidewall portion  24 ,  25  of the case main body  12  and the engagement claw  49 ,  50  so that the gap G may be forcibly widened for lifting up the case lid  14 . See FIG.  6 . In this embodiment, to easily detach the case lid  14 , the gap G is made wider than that in the snap-fit structure in the related art, so that a screwdriver, etc., can be easily inserted into the gap G. Thus, in this embodiment, the case lid  14  can be easily detached so that the ink cartridge  1  can be easily disassembled when it is recycled, etc. 
   Next, the partition plate  4 , which is housed in the cartridge case  2 , comprises a rectangular main body portion  61  and a rectangular frame portion  62  rising upward from the four peripheral margins of the main body portion  61 . The frame portion  62  is dimensioned for allowing the frame portion  62  to drop through the upper opening  13  and move along the inner surface of the case main body  12  in a slidable state. Upper end face portions  63 , at the four corners of the frame portion  62 , are at higher positions than other portions of the partition plate. The four corners of the frame portion  62  abut the outer frame end face (partition plate clamp face)  39  of the case lid  14  when the lid is attached to the case main body  12 . 
   The main body portion  61  of the partition plate  4  is formed in its rear portion with an inclined part  64  which is inclined upward so that the rear end thereof is contiguous to the rear wall portion of the frame portion  62 . The second ink bag  3 ( 2 ) is mounted on the partition plate  4 . The second ink bag  3 ( 2 ) has its ink outlet  7  fixed to the outer frame front wall portion of the partition plate  4 , and the rear face of its bag main body portion  6  is fixed to the surface of the main body portion  61  with a double-faced adhesive, or the like. The rear portion of the bag main body portion  6  is supported by the inclined part  64  formed in the rear portion of the main body portion  61  so that its position in the up and down direction of the case is defined. 
   Thus, if the partition plate  4  in this embodiment is dropped through the upper opening  13  and into the case main body  12 , it abuts the rib upper end faces  31   a ,  32   a ,  33   a , and  34   a  formed in the case main body  12  so that its position in the up and down direction in the case is defined. When the case lid  14  is attached to the case main body  12 , the upper end face portions  63 , at the four corners of the partition plate  4 , are pressed downward by the end face  39  of the outer frame portion formed on the case lid  14 . 
   Therefore, the partition plate  4  in this embodiment prevents the ink bags  3 ( 1 ) and  3 ( 2 ) from interfering with each other, and is sandwiched up and down between the case main body  12  and the case lid  14  so that it is held at a predetermined position in the case. Thus, the partition plate  4  easily can be detached from the case main body  12 , unlike the case wherein the partition plate  4  is fixed to the case main body  12  with a joint structure of the snap-fit type. Consequently, the ink cartridge  1  of this embodiment can be assembled and disassembled extremely easily and, particularly, the partition plate can be attached and detached extremely easily. 
   Next will be discussed a positioning structure for fixing each ink outlet part  7 , of the ink bag  3 ( 1 ),  3 ( 2 ) in this embodiment, to a predetermined position. 
   The ink outlet part  7  is, for example, a plastic molded article and includes a cylindrical ink derivation tube portion  71 , a cylindrical opening tube portion  72 , and a columnar outlet elastic body  73 . The cylindrical ink derivation tube portion  71  is for deriving ink from the ink bag. The cylindrical opening tube portion  72  is of a large diameter and is formed at the tip of the ink derivation tube portion  71 . Further, the columnar outlet elastic body  73  is made of an elastic material such as rubber, or the like, and is fitted into the opening tube portion  72  so that ink is sealed within the ink bag by the columnar outlet elastic body  73 . The opening tube portion  72  has formed on its outer peripheral surface, an annular groove  74  that is rectangular in cross section. 
   In the case of main body  12 , an ink outlet placement part  75  is formed at the center in the width direction of the front wall portion  23 . Referring to  FIGS. 3 ,  5 , and  7 , the ink outlet placement part  75  includes a projection wall portion  76  projected like a half circle, and also includes an ink supply needle insertion hole  16  made in the center of the projection wall portion  76 . A positioning plate  78 , formed with a semi-circular positioning groove  77  opened upward, is formed on the rear of the projection wall portion  76 . If the ink bag&#39;s opening tube portion  72  is inserted into the ink outlet placement part  75  from the upper side, the positioning groove inner peripheral margin portion (also called an ink outlet clamp face) of the positioning plate  78  is fitted into the annular groove  74 , whereby the ink bags ink outlet part  7  is fixed to the case main body  12 . 
   An ink outlet placement part  80 , having a similar structure to that of the ink outlet placement part  75 , is formed at the center in the width direction of a front wall portion  79  of the partition plate  4 . The ink outlet placement part  80  includes a projection wall portion  81  forwardly projected like a rectangle, and also includes an ink supply needle insertion hole  17  made in the center of the projection wall portion  81 . A positioning plate  83 , formed with a semi-circular positioning groove  82  opened upward, is formed on the rear of the projection wall portion  81 . If the ink bag&#39;s opening tube portion  72  is inserted into the ink outlet placement part  80  from the upper side, the positioning groove inner peripheral margin portion of the positioning plate  83  is fitted into the annular groove  74 , whereby the ink bags ink outlet part  7  is fixed to the partition plate  4 . 
   As seen in  FIGS. 3 and 7 , in this embodiment, the ink outlet parts  7  and  7  of the ink bags  3 ( 1 ) and  3 ( 2 ) are overlaid on each other so that they are in direct contact with each other in the case thickness direction. Also, and the width of a center portion  83   a , formed on the partition plate  4  (that is, its dimension in the up and down direction of the case) is determined so that the center portion  83   a  is just housed in the annular grooves  74  and  74  formed in the outer peripheral surfaces of the opening tube portions  72  and  72  of the ink outlet parts  7  and  7 . 
   Next, vertical guide grooves  84  and  85  are formed in the partition plate  4  so that they are located on both sides of the projection wall portion  76 . Additionally, in the front wall portion of the case main body  12 , vertical guide rails  87  and  88  are formed in vertical margin portions on both sides of an opening  86  made above the ink outlet placement part  75 . If the vertical guide rails  87  and  88  are inserted into the vertical guide grooves  84  and  85  in the partition plate  4  and, in this state, the partition plate  4  is dropped into the case main body  12 , the ink outlet part  7  of the second ink bag  3 ( 2 ) mounted on the partition plate  4  is positioned just above the ink outlet part  7  of the first ink bag  3 ( 1 ) mounted on the bottom plate portion  22  of the case main body  12  so that the outer peripheral surfaces of the opening tube portions  72  and  72  abut each other. At the same time, the center portion  83   a  is sandwiched up and down between the annular grooves  74  and  74  formed in the outer peripheral surfaces of the opening tube portions  72  and  72 . 
   Next, an ink outlet press part  91  is formed in the front center portion of the case lid  14 . The ink outlet press part  91  includes left and right vertical frames  92  and  93 , and a horizontal frame  94  for joining the lower ends of the vertical frames  92  and  93 . The horizontal frame  94  is formed at the center of its lower face with a circular arc face  95  that matches the outer peripheral surface of the opening tube portion  72  of the ink outlet. Also, the circular arc face  95  is formed at its center with a projection that is slightly projected downward. Since the horizontal frame portion  94  is formed with the circular arc face  95  having a thin thickness, it is low in rigidity as compared with other portions and, therefore, easily becomes elastically deformed in the up and down direction so that it can function as a plate spring. A cylindrical waste-ink introduction tube  96 , for introducing wasted ink into the waste-ink absorption material  5 , is placed at the depth of the ink outlet press part  91  and is also formed of an elastic material, such as rubber, or the like. Further, a waste-ink collection needle is inserted into the waste-ink introduction tube  96 . 
   The ink outlet press part  91  can also be inserted into the upper opening  13  of the case main body  12  from the upper side. When the ink outlet press part  91  is completely inserted into the upper opening  13 , it presses the outer peripheral surface of the opening tube portion  72  of the second ink bag  3 ( 2 ) with its circular arc face  95  of the horizontal frame  94 . 
   Thus, in this embodiment, the ink outlet parts  7  and  7  are stacked up and down on each other without intervention of the partition plate  4 . Therefore, the thickness of the ink cartridge  1  can be reduced by as much as the thickness of the partition plate as compared with the case where the partition plate intervenes between ink outlet parts. Generally, in the ink bag  3 ( 1 ),  3 ( 2 ), the outer diameter dimension of the opening tube portion  72  of the ink outlet part  7  is larger than the thickness of the bag main body portion  6  (when the bag main body portion is filled with ink) and, thus, the thickness of the ink bag housing portion depends on the thickness (outer diameter dimension) of the ink outlet part  7 . If the partition plate  4  is sandwiched between the ink outlet parts  7  and  7 , the thickness of the ink-bag housing portion is increased by as much as the thickness of the partition plate  4 . In the embodiment, however, the ink outlet parts  7  and  7  are stacked up and down on each other with the opening tube portions  72  brought into direct contact with the ink outlet parts  7 , so that the ink cartridge can be minimized and particularly the thickness dimension of the ink cartridge can be reduced. 
   In this embodiment, the case lid  14 —formed with the ink outlet press part  91  having the circular arc face  95 —presses the ink outlet parts  7  and  7  so that they are stacked up and down on each other against the bottom plate portion of the case main body  12  from the upper side. Therefore, the ink outlet parts  7  and  7  can be reliably fixed to predetermined positions. 
   Further, in this embodiment, the horizontal frame portion  94  in the ink outlet press part  91  is provided with a spring property so that the ink outlet parts  7  and  7  can be reliably fixed to the predetermined positions without involving looseness, and the like. 
   For example, red ink may be stored in the ink bag  3 ( 1 ) and black ink may be stored in the ink bag  3 ( 2 ). To use the ink cartridge of this embodiment with an ink jet recorder, as described later, usually black ink is used for printing and the portion to be highlighted is printed in red ink, whereby it is made possible to print in a lively style. For example, when the balance becomes minus, the bankbook is printed in red ink, whereby the bankbook owner can be warned of the balance due. 
   Alternatively, it is possible to store dark black ink and light black ink in the inkbags  3 ( 1 ) and  3 ( 2 ), respectively, in order to print a halftone like a photo, whereby smooth printing with less granular feeling can be executed on the ink jet printer. 
   Detection Plate 
   Next, the contour shape of the detection plate  8 , which is attached to the ink bag  3 ( 1 ),  3 ( 2 ), will be discussed with reference to FIG.  8 . The contour shape of the detection plate  8  is set so as to reduce the amount of useless ink remaining accumulated in the peripheral portions of the bag main body portion  6 , which portions are not covered by the detection plate  8 . Movement of the detection plate  8 , as the ink bag  3 ( 1 ),  3 ( 2 ) becomes deformed, is smooth so that variations in the amount of ink remaining after the detection plate indicates the end can be suppressed and the amount itself can be reduced. 
   The detection plate  8  is almost rectangular and is fixed to the bag main body portion  6  of the ink bag  3 ( 1 ),  3 ( 2 ), which is also rectangular, so that their sides become almost parallel with each other as shown in the figure. 
   According to the experiment of the inventors, it has been shown that it is desirable to place lateral dimension  8 W of the detection plate  8  within 0.5 to 1.0 times lateral dimension  6 W of the bag main body portion  6 , particularly within the range of 0.7 to 1.0 times the lateral dimension  6 W. Likewise, it has been shown that it is desirable to place longitudinal dimension  8 L of the detection plate  8  within 0.4 to 0.8 times longitudinal dimension  6 L of the bag main body portion  6 , particularly within the range of 0.6 to 0.8 times the longitudinal dimension  6 L. 
   In addition, to make the detection plate  8  easily follow deformation of the bag main body portion  6  of the ink bag—namely, deformation with a decrease in the amount of ink—for detecting the ink end with good accuracy, it is desirable to: 
   Place the ratio between: (i) the ratio between the lateral dimension  8 W of the detection plate  8  and the lateral dimension  6 W of the bag main body portion  6  ( 8 W/ 6 W); and (ii) the ratio between the longitudinal dimension  8 L of the detection plate  8  and the longitudinal dimension  6 L of the bag main body portion  6  ( 8 L/ 6 L), within the range of 0.8 to 1.2, particularly within the range of 0.9 to 1.1. In other words, it is desirable to make the contour shape of the detection plate  8  similar to the contour shape of the bag main body portion  6 . 
   Further, to make the detection plate  8  easily follow deformation of the bag main body portion  6  of the ink bag—namely, deformation with a decrease in the amount of ink—for detecting the ink end with good accuracy, it is also desirable to set the thickness of the detection plate  8  within the range of 0.7 mm to 1.2 mm, particularly within the range of 0.8 mm to 1.0 mm. 
   The above-described ink cartridge  1  includes waste-ink absorption material, but the invention can also be applied to an ink cartridge having no waste-ink absorption material. 
   The above-described ink cartridge  1  includes detection plates  8 , but the invention can also be applied to an ink cartridge having no detection plate. 
   Second Embodiment—an Ink Cartridge having a Partition Plate 
   The above-described ink cartridge  1 , having a partition plate, comprises two ink bags and one partition plate placed therebetween. However, of course the invention can also be applied to an ink cartridge comprising three or more ink bags and partition plates each placed between two ink bags. 
     FIGS. 9 and 10 , respectively, are an exploded perspective view and a transverse sectional view showing a second embodiment of an ink cartridge comprising three ink bags and two partition plates each for partitioning the ink bags. 
   As shown in the figures, an ink cartridge  100  has a case main body  112 , first, second, and third ink bags  103 ( 1 ),  103 ( 2 ), and  103 ( 3 ) housed in the case main body  112 , two partition plates  104 ( 1 ) and  104 ( 2 ) each placed between two ink bags, a waste-ink absorption material  105 , and a case lid  114 . 
   The case main body  112  and the case lid  114  are joined according to a snap fit structure as described above in connection with the ink cartridge  1 ; the case lid  114  is thus detachably attached to the case main body  112 . The case lid  114  is easily detached so that the ink cartridge  100  can be easily disassembled when it is recycled, etc. 
   The ink bag  103 ( 1 ),  103 ( 2 ),  103 ( 3 ) has the same structure and configuration as the ink bag  3 ( 1 ),  3 ( 2 ) of the ink cartridge  1 . Yellow ink may be stored in the ink bag  103 ( 1 ), magenta ink may be stored in the ink bag  103 ( 2 ), and cyan ink may be stored in the ink bag  103 ( 3 ). 
   The case main body  112  includes a rectangular bottom plate portion  122 , a front wall portion  123 , two side-wall portions  124  and  125 , and a rear wall portion  126 . The wall portions are formed as side plate portions rising upward from four peripheral margins of the bottom plate portion  122 . Further, the case main body  112  has an opening  113  on its top. 
   The front wall portion  123  is formed with an ink supply needle insertion hole  116  into which an ink supply needle (described later) is inserted. Likewise, the front portions of the partition plates  104 ( 1 ) and  104 ( 2 ) are also each formed with an ink supply needle insertion hole  117 . Further, the front portion of the case lid  114  is formed with a waste ink collection needle insertion hole  118 . 
   As with the ink cartridge  1 , the ink bag  103 ( 1 ) has an ink outlet portion fixed to the front wall portion  123  of the case main body  112 , and also has a bag main body portion  106  fixed to the bottom plate portion  122  of the case main body  112  with a double-faced adhesive, or the like, (not shown). The ink bag  103 ( 2 ) has an ink outlet portion fixed to the front portion of the partition plate  104 ( 1 ), and also has a bag main body portion  106  fixed to a bottom plate portion  161  of the partition plate  104 ( 1 ) with a double-faced adhesive, or the like, (not shown). Similarly, the ink bag  103 ( 3 ) has an ink outlet portion fixed to the front portion of the partition plate  104 ( 2 ), and also has a bag main body portion  106  fixed to a bottom plate portion  161  of the partition plate  104 ( 2 ) with a double-faced adhesive, or the like, (not shown). 
   The front wall portion  123 , the left and right side wall portions  124  and  125 , and the rear wall portion  126 , have formed, on their inner surfaces, a plurality of ribs  131 ,  132 ,  133 , and  134 . The upper ends of the ribs (also called partition plate clamp faces) are at the same height, thereby determining the position of the partition plate  104 ( 1 ) in the ink cartridge  100 . 
   The case lid  114  includes a rectangular lid main body portion  135 , and an outer frame portion  136  formed in the four peripheral margins of the lid main body portion  135 . An end face  139 , of the outer frame portion  136 , functions as a partition plate clamp face for pressing the partition plate  104 ( 1 ),  104 ( 2 ) against the rib upper ends (also called partition plate clamp faces) formed in the case main body  112 . 
   Each of the partition plates  104 ( 1 ) and  104 ( 2 ) housed in the case main body  112  comprises the above-mentioned bottom plate portion  161  and a rectangular frame portion  162  rising upward from the four peripheral margins of the bottom plate portion  161 . The frame portion  162  is dimensioned to allow the frame portion  162  to drop through the opening  113  of the case main body  112  and along the inner surface thereof in a slidable state. Upper end face portions  163 , at the four corners of the frame portion  162 , are at higher positions than are other portions of the frame portion. Also, the end face portions  163  abut the outer frame end face (partition plate clamp face)  139  of the case lid  114  when it is attached to the case main body  112 . 
   Thus, if the first partition plate  104 ( 1 ) in this embodiment is dropped through the upper opening  113  and into the case main body  112 , it abuts the upper end faces of ribs  131 ,  132 ,  133 , and  134  formed in the case main body  112 , and its position in the up and down direction in the case is defined. Next, if the second partition plate  104 ( 2 ) is dropped through the upper opening  113  and into the case main body  112 , it abuts the upper end face portions  163  at the four corners of the first partition plate  104 ( 1 ), and its position in the up and down direction in the case is defined. Further, if the case lid  114  is then attached to the case main body  112 , the upper end face portions  163  at the four corners in the frame portion  162  of the second partition plate  104 ( 2 ) are pressed downward by the end face  139  of the outer frame portion  136  formed on the case lid  114 . 
   Therefore, the first and second partition plates  104 ( 1 ) and  104 ( 2 ) in this embodiment are sandwiched up and down between the case main body  112  and the case lid  114  so that they are held at predetermined height positions in the case. Thus, the partition plates  104 ( 1 ) and  104 ( 2 ) can be easily detached from the case main body  112 , unlike the case where the partition plates  104 ( 1 ) and  104 ( 2 ) are fixed to the case main body  112  by a joint structure of the snap fit type. Consequently, the ink cartridge  100  of this embodiment can also be assembled and disassembled extremely easily and, particularly, the partition plates can be attached and detached extremely easily. 
   A detection plate  108 ( 1 ) is fixed to the ink bag  103 ( 1 ) by, for example, double-faced tape (not shown). The detection plate  108 ( 1 ) is provided for detecting when the amount of ink remaining in the ink bag  103 ( 1 ) has decreased to a predetermined amount. A detection projection  109 ( 1 ) is formed on the detection plate  108 ( 1 ) so that it is capable of projecting to the outside from an opening  111  made in the bottom plate portion  122  of the case main body  112 . The amount of projection is increased with a decrease in the amount of ink remaining and, when the projection length of the detection projection  109 ( 1 ) becomes equal to or greater than a determined length, the detection projection  109 ( 1 ) is detected by an ink end detection mechanism (described later) so that it is known when the yellow ink runs out. 
   A detection plate  108 ( 2 ) is fixed to the ink bag  103 ( 2 ). The detection plate  108 ( 2 ) is also provided for detecting when the amount of ink remaining in the ink bag  103 ( 2 ) decreases to a predetermined amount. A detection projection  109 ( 2 ) is formed on the detection plate  108 ( 2 ) so that it is capable of passing through an opening  161   a  made in the bottom plate portion  161  of the partition plate  104 ( 1 ), and so that a tip thereof is capable of being placed in the space formed by: the bottom plate portion  122 ; the front wall portion  123 ; the left and right side wall portions  124  and  125 ; and the rear wall portion  126 ; and the bottom plate portion  161  of the partition plate  104 ( 1 ). The detection projection  109 ( 2 ) is capable of projecting to the outside from the opening  111 , which is made in the bottom plate portion  122  of the case main body  112 , in such a manner that the amount of projection is increased with a decrease in the amount of ink remaining. When the projection length of the detection projection  109 ( 2 ) becomes equal to or greater than a determined length, the detection projection  109 ( 2 ) is detected by the ink end detection mechanism and it is known that magenta ink has run out. 
   Likewise, a detection plate  108 ( 3 ) is fixed to the ink bag  103 ( 3 ). The detection plate  108 ( 3 ) is also provided for detecting when the amount of ink remaining in the ink bag  103 ( 3 ) decreases to a predetermined amount. A detection projection  109 ( 3 ) is formed on the detection plate  108 ( 3 ) so that it is capable of passing through an opening  161   a  made in the bottom plate portion  161  of the partition plate  104 ( 1 ) and an opening  161   a  made in the bottom plate portion  161  of the partition plate  104 ( 2 ), and so that a tip thereof is capable of being placed in the space formed by; the bottom plate portion  122 ; the front wall portion  123 ; the left and right side wall portions  124  and  125 ; the rear wall portion  126  of the case main body  112 ; and the bottom plate portion  161  of the partition plate  104 ( 1 ). The detection projection  109 ( 3 )projects to the outside from the opening  111 , which is made in the bottom plate portion  122  of the case main body  112 , in such a manner that the amount of projection is increased with a decrease in the amount of ink remaining. When the projection length of the detection projection  109 ( 3 ) becomes equal to or greater than a determined length, the detection projection  109 ( 3 ) is detected by the ink end detection mechanism (described later) and it is known that cyan ink has run out. 
   As described above, the first and second partition plates  104 ( 1 ) and  104 ( 2 ) in this embodiment are sandwiched up and down between the upper end faces of the ribs  131 ,  132 ,  133 , and  134  (also called partition plate clamp faces) formed in the case main body  112 , and the outer frame end face (also called the partition plate clamp face)  139  of the case lid  114  so that they are held at predetermined positions in the case. Thus, the up and down positions of the partition plates  104 ( 1 ) and  104 ( 2 ) in the case are defined, and the up and down positions of the second and third ink bags  103 ( 2 ) and  103 ( 3 )—which are held on the partition plates  104 ( 1 ) and  104 ( 2 )—can also be defined with good accuracy. Further, the projection accuracy of the detection projections  109 ( 2 ) and  109 ( 3 ), of the detection plates attached to the ink bags, is enhanced so that the amount of ink remaining in each of the second and third ink bags  103 ( 2 ) and  103 ( 3 ) can be detected with good accuracy. That is, the ends of magenta ink and cyan ink can be detected with the same level of accuracy as is detected the end of yellow ink. 
   The above-described ink cartridge  100  includes waste-ink absorption material but, of course, the invention can also be applied to an ink cartridge having no waste-ink absorption material. 
   Third Embodiment—Ink Jet Printer using an Ink Cartridge  1  as an Ink Supply Source 
   An embodiment of an ink jet printer using the above-described ink cartridge  1 , having a partition plate, as an ink supply source will be discussed with reference to  FIGS. 11 ,  12 , and  13 . 
   First, ink supply and discharge channels of an ink jet printer  200  of this embodiment will be discussed with reference to FIG.  11 . The basic configuration of the ink jet printer  200  is similar to that of a generally used ink jet printer and, therefore, will not be discussed here. The ink jet printer  200  is formed with a cartridge placement section  203  in which the ink cartridge  1  detachably is placed. Two ink supply needles  204 ( 1 ) and  204 ( 2 ), and one waste ink collection needle  205 , are attached to the cartridge placement section  203 , for example, horizontally. If the needles  204 ( 1 ),  204 ( 2 ), and  205  respectively are inserted into the ink supply needle insertion holes  16  and  17  and the waste ink collection needle insertion hole  18  in the ink cartridge  1 , ink flow passages for supplying and discharging ink are formed between the ink cartridge  1  and the ink jet printer  200 . 
   When the ink flow passages are formed, ink stored in the cartridge&#39;s ink bag  3 ( 1 ) and ink in the ink bag  3 ( 2 ) are taken out into ink supply tubes  207 ( 1 ) and  207 ( 2 ) through the ink supply needles  204 ( 1 ) and  204 ( 2 ). Filters  208 ( 1 ) and  208 ( 2 ), for filtering dust and foreign substance in the ink, are placed at midpoints of the ink supply tubes  207 ( 1 ) and  207 ( 2 ). 
   Ink is introduced into an ink jet head  209 , of the ink jet printer  200 , through the ink supply tubes  207 ( 1 ) and  207 ( 2 ). The ink jet head  209  is mounted on a carriage (not shown) and is reciprocated in the length direction along the surface of a platen  211 . Record paper (not shown) is transported in a direction orthogonal to the move direction of the ink jet head  209  along the surface of the platen  211 , and is printed with the ink jet head  209 . 
   To maintain the print quality of the ink jet head  209 , ink nozzles of the ink jet head  209  are cleaned by sucking ink therefrom. For this purpose, a head cap  212  is placed at a position out of a print area of the ink jet head  209 , and the ink jet head  209  periodically is moved to the position of the head cap  212 . A waste ink tube  213 , for collecting waste ink collected or sucked from the ink jet head  209  by way of the head cap  212 , is connected to the head cap  212 . A waste ink pump  214 , as a drive source for collecting waste ink, is connected to the waste ink tube  213 . 
   The waste ink passes through the waste ink tube  213 , by action of the waste ink pump  214 , and then passes through the waste ink collection needle  205  so that it enters the cartridge. Thus, waste ink is collected and held in the waste-ink absorption material  5 , which is in the cartridge. 
     FIG. 12  is a schematic representation to describe an ink end detection mechanism contained in the ink jet printer  200  of this embodiment. As shown in the figure, an ink end detector  215  is installed in the cartridge placement section  203 , and a transfer plate  216  is fixed to the ink end detector  215  with an adhesive, or the like. If the remaining amount of red ink in the ink bag  3 ( 1 ) is decreased to a predetermined amount, or if the remaining amount of black ink in the ink bag  3 ( 2 ) is decreased to a predetermined amount, the detection projection  9 ( 1 ) formed on the detection plate  8 ( 1 ) or the detection projection  9 ( 2 ) formed on the detection plate  8 ( 2 ) presses the transfer plate  216  thereby turning on the ink end detector  215 . The transfer plate  216  is a thin plate having rigidity; here, an acrylic plate  1  mm thick is used. The ink end detector  215  is a switch of the mechanical contact type. 
   Next will be described  FIG. 13 , which is a schematic block diagram showing a control system of the ink jet printer  200  of this embodiment. In the figure, reference numeral  221  denotes a power switch for making the printer operational, and as an example of power supply, a DC regulator is connected to an AC power supply as a drive source. Numeral  209  denotes the above-described ink jet head, numeral  215  denotes the above-described ink end detector, and numeral  222  denotes a drive motor having capabilities of moving the carriage on which the ink jet head  209  is mounted, transporting record paper, and driving the waste ink pump  214 . Numeral  223  denotes recovery processing means for driving the drive motor  222 , and for controlling the cleaning of the ink jet head  209  and the sucking of ink. Separate drive motors for moving the carriage, transporting record paper, and driving the waste ink pump may be provided as the drive motor  222 . 
   Numeral  224  denotes print operation control means for expanding print data from an external instruction system, such as a personal computer, into a printer language. The print operation control means is also for controlling head drive means  225  and the drive motor  222  with a print control signal, based on a print command signal, for executing print control. Further, the print operation control means  224  controls the recovery processing means  223  and display means  226 . Numeral  227  denotes storage means, used by the print operation control means  224  to perform operation processing, and the like, for temporarily storing the print data and the provided print language. 
   The ink jet head  209  of this embodiment is divided into a portion for jetting red ink supplied from the ink bag  3 ( 1 ) of the ink cartridge  1 , and a portion for jetting black ink supplied from the ink bag  3 ( 2 ). To jet ink in a liquid drop state from the nozzles of the ink jet head  209  for printing record paper, the ink jet head drive means  225  controls the driving of the ink jet head  209  for each portion based on the print control signal. 
   The display means  226  displays various pieces of information for the operator of the ink jet printer  200 . Numeral  228  denotes ink end determination means for receiving a detection signal from the ink end detector  215 , and for determining whether either ink in the ink cartridge  1  runs out. 
   If the remaining amount of red ink in the ink bag  3 ( 1 ) is decreased to the predetermined amount, or if the remaining amount of black ink in the ink bag  3 ( 2 ) is decreased to the predetermined amount, the ink end detector  215  is turned on, the ink end determination means  228  receives an ink end detection signal and determines that the ink has run out. The ink end determination means  228  transfers the determination result to the print operation control means  224 , which then stops the operation of the head drive means  225  to stop printing and displays a message on the display means  226  that ink has run out. 
   Next,  FIG. 14  is a schematic block diagram showing another exemplary configuration of the controller of the ink jet printer  200  of this embodiment. In the figure, ink jet head  209 , ink end detector  215 , recovery processing means  223 , head drive means  225 , drive motor  222 , power switch  221 , and display means  226  are, in operation and control method, identical with or similar to those previously described with reference to  FIG. 13 and , therefore, will not be discussed again. 
   In the controller, numeral  229  denotes measuring means for measuring the amount of ink jetted from the ink jet head  209 , and the amount of ink consumed as waste ink, based on a command from print operation control means  224 . The amount of ink jetted from the ink jet head  209  is calculated from the number of times each nozzle has been driven by the head drive means  225 , for example. The amount of ink consumed as waste ink is calculated from the number of times the waste ink pump  214  has been driven, for example. 
   The print operation control means  224  expands print data from an external instruction system, such as a personal computer, into a printer language and controls the head drive means  225  and the drive motor  222  with a print control signal based on a print command signal for executing print control. The print operation control means  224  controls the display means  226 , and the measuring means  229 , as well as the recovery processing means  223  and, thereby, determines the ink end. 
   Storage means  227  temporarily stores the print data, and the provided print language, when the print operation control means  224  performs operation processing, and the like. Also, the storage means  227  stores a predetermined ink amount and the ink amount measured by the measuring means  229 . 
   If the remaining amount of red ink in the cartridges ink bag  3 ( 1 ) is decreased to a predetermined amount, or if the remaining amount of black ink in the ink bag  3 ( 2 ) is decreased to a predetermined amount, the ink end detector  215  is turned on and the print operation control means  224  receives an ink-near-end detection signal. Upon reception of the ink-near-end detection signal, the print operation control means  224  displays, on the display means  226 , a message indicating that the ink is near end and instructs the measuring means  229  to measure the amount of ink jetted from the head  209  and the amount of ink consumed as waste ink. When a print command signal is input to control the recovery processing means  223 , the print operation control means  224  checks the ink amount measured by the measuring means  229 . When the power switch  221  is turned off, the print operation control means  224  temporarily stores, in the storage means  227 , the ink amount measured by the measuring means  229 . The predetermined ink amount is also stored in the storage means  227 . Thus, if the print operation control means  224  determines that the ink amount measured by the measuring means  229  has reached the predetermined ink amount, it stops the operation of the head drive means  225  to stop printing, and displays a message on the display means  226  indicating that the ink has run out. 
   It is possible for the ink jet printer, having the above-described controller, to continue printing until the predetermined amount of ink as stored in the storage means  227  is used up, even after the message indicating that the ink is near its end is displayed on the display means  226 . Meanwhile, the operator of the ink jet printer may have a new ink cartridge on hand. Thus, the ink jet printer provides excellent usability and is convenient for the operator of the printer. 
   In this case, after detecting that the ink is near its end, the remaining amount of ink can be displayed on the display means  226 , for example. That is, the display means  226  will indicate the amount of ink remaining until the print operation control means  224  stops the operation of the head drive means  225  to stop printing when the amount of ink measured by the measuring means  229  reaches the predetermined amount of ink. This makes it furthermore convenient for the operator of the ink jet printer. 
   The ink jet printer  200  in which the small-sized ink cartridge  1 , although no ink bags are housed therein, is placed can print in a plurality of inks and the ink jet printer itself can be miniaturized. 
   With an ink jet printer wherein one ink bag is housed in an ink cartridge and one ink cartridge is placed for each ink, the volume of a cartridge placement section of the ink jet printer grows. And when ink is used up, it is necessary to replace the ink cartridge for each ink so that the operator of the ink jet printer is inconvenienced. Further, the operator of the ink jet printer needs to have an ink cartridge on hand for each type of ink used. 
   In contrast, in the present invention, the volume of the cartridge placement section is reduced and, thus, the ink jet printer can also be miniaturized. Further, an ink cartridge needs to be replaced only once for a plurality of inks, so that the ink cartridge replacement frequency is low, and so that the replacement operation is easy. To print in a plurality of colors, the operator of the ink jet printer needs to have only one ink cartridge on hand; it is convenient for the operator. In addition, the ink jet printer of the present embodiment contains one ink end detector and, thus, can be miniaturized along with its cost being reduced. 
   Fourth Embodiment—an Ink Jet Printer Using an Ink Cartridge  100  as an Ink Supply Source 
     FIG. 15  is a schematic configuration drawing showing ink supply and discharge channels of an ink jet printer using the above-described ink cartridge  100 , which has partition plates, as an ink supply source.  FIG. 16  is a schematic representation to describe an ink end detection mechanism in the ink jet printer.  FIG. 17  is a schematic block diagram showing a control system of the ink jet printer. 
   First, the configuration of an ink jet printer  300  of this embodiment and an ink end detection method will be discussed with reference to  FIGS. 15 and 16 . The ink jet printer  300  is formed with a cartridge placement section  303  in which the ink cartridge  100  detachably is placed. Three ink supply needles  304 ( 1 ),  304 ( 2 ), and  304 ( 3 ) and one wastes ink collection needle  305  are attached to the cartridge placement section  203  so that they extend horizontally. If the ink supply needle  304 ( 1 ) is inserted into the ink supply needle insertion hole  116 , the ink supply needles  304 ( 2 ) and  304 ( 3 ) are inserted into the two ink supply needle insertion holes  117  and  117 , and the waste ink collection needle  305  is inserted into the waste ink collection needle insertion hole  118 , ink flow passages for supplying and discharging ink are formed between the ink cartridge  100  and the ink jet printer  300 . 
   When the ink flow passages are formed, yellow ink, magenta ink, and cyan ink stored in the three ink bags  103 ( 1 ),  103 ( 2 ), and  103 ( 3 ) are taken out into ink supply tubes  307 ( 1 ),  307 ( 2 ), and  307 ( 3 ) through the ink supply needles  304 ( 1 ),  304 ( 2 ), and  304 ( 3 ). 
   Yellow, magenta, and cyan inks are introduced into three ink jet heads  309 ( 1 ),  309 ( 2 ), and  309 ( 3 ) of the ink jet printer  300  through the ink supply tubes  307 ( 1 ),  307 ( 2 ), and  307 ( 3 ). Nozzle groups  310 ( 1 ),  310 ( 2 ), and  310 ( 3 ) are placed in the heads  309 ( 1 ),  309 ( 2 ), and  309 ( 3 ) in a direction orthogonal to the paper face and are filled with inks introduced from the ink supply tubes  307 ( 1 ),  307 ( 2 ), and  307 ( 3 ). That is, the nozzle group  310 ( 1 ) of the head  309 ( 1 ) is filled with yellow ink, the nozzle group  310 ( 2 ) of the head  309 ( 2 ) is filled with magenta ink, and the nozzle group  310 ( 3 ) of the head  309 ( 3 ) is filled with cyan ink. Record paper  308  is transported in the arrangement direction of the three heads  309 ( 1 ),  309 ( 2 ), and  309 ( 3 ) along the surface of a platen  311 , and is printed with the heads  309 ( 1 ),  309 ( 2 ), and  309 ( 3 ). 
   To maintain the print quality of the heads  309 ( 1 ),  309 ( 2 ), and  309 ( 3 ), they are cleaned by sucking ink therefrom. A head cap  312  is placed below the platen  311 , and the heads  309 ( 1 ),  309 ( 2 ), and  309 ( 3 ) together are moved in the direction of arrow H to the position of the head cap  312 . The head cap  312  abuts the three heads  309 ( 1 ),  309 ( 2 ), and  309 ( 3 ) and sucks inks from the nozzle groups  310 ( 1 ),  310 ( 2 ), and  310 ( 3 ) at the same time. A waste ink tube  313 , for collecting waste ink collected or sucked from the heads  309 ( 1 ),  309 ( 2 ), and  309 ( 3 ) by the head cap  312 , is connected to the head cap  312 . A waste ink pump  314 , as a drive source for collecting waste ink, is connected to the waste ink tube  313 . 
   The waste ink flows through the waste ink tube  313  by action of the waste ink pump  314 . The waste ink then flows through the waste ink collection needle  305  and into the waste-ink absorption material  105 , where it is collected and held. 
   Three ink end detectors  315 ( 1 ),  315 ( 2 ), and  315 ( 3 ) are installed in the cartridge placement section  303 . If the remaining amount of yellow ink in the ink bag  103 ( 1 ) is decreased to a predetermined amount, the detection projection  109 ( 1 ) formed on the detection plate  108 ( 1 ) turns on the ink end detector  315 ( 1 ). Likewise, if the remaining amount of magenta ink in the ink bag  103 ( 2 ) is decreased to a predetermined amount, the detection projection  109 ( 2 ) formed on the detection plate  108 ( 2 ) turns on the ink end detector  315 ( 2 ). And if the remaining amount of yellow ink in the ink bag  103 ( 3 ) is decreased to a predetermined amount, the detection projection  109 ( 3 ) formed on the detection plate  108 ( 3 ) turns on the ink end detector  315 ( 3 ). The ink end detector  315 ( 1 ),  315 ( 2 ),  315 ( 3 ) may be of a mechanical contact type, or may be of light detection type such as a photo interrupter, or any other type as long as the ink end detector can detect the fact that the projection length of the detection projection  109 ( 1 ),  109 ( 2 ),  109 ( 3 ) from the ink cartridge  100  becomes equal to or greater than a determined length. 
   Next, the control operation in the ink jet printer  300  will be discussed with reference to FIG.  17 . Numeral  321  denotes a power switch for making the printer operational. Numerals  309 ( 1 ),  309 ( 2 ), and  309 ( 3 ) denote the above-described ink jet heads, and numeral  322  denotes a drive motor capable of transporting the record paper  308  and driving the waste ink pump  314 . Numeral  323  denotes recovery processing means for driving the drive motor  322 , for controlling the cleaning of the heads  309 ( 1 ),  309 ( 2 ), and  309 ( 3 ), and for controlling the sucking of ink. Separate drive motors for transporting record paper and driving the waste ink pump may be provided as the drive motor  322 . 
   Numeral  324  denotes print operation control means for expanding print data from an external instruction system, such as a personal computer; into a printer language. The print operation control means is also for controlling the head drive means  325  and the drive motor  322  with a print control signal, based on a print command signal, for executing print control. Further, the print operation control means  324  receives a detection signal from the ink end detector  315 ( 1 ),  315 ( 2 ), or  315 ( 3 ), and determines which colored ink in the ink cartridge  100  has run out. Numeral  326  denotes storage means, used by the print operation control means  324  to perform operation processing, and the like, for temporarily storing the print data and the provided print language. 
   To jet ink in a liquid drop state from the nozzles of the heads  309 ( 1 ),  309 ( 2 ), and  309 ( 3 ), for printing record paper, the head drive means  325  controls the driving of the heads  309 ( 1 ),  309 ( 2 ), and  309 ( 3 ) based on the print control signal. In this embodiment, the head drive means  325  is divided and the control signal can be transferred for each head so that the heads  309 ( 1 ),  309 ( 2 ), and  309 ( 3 ) can be controlled separately. 
   For example, if yellow color print data and print command signal are input after the ink end detector  315 ( 1 ) is turned on, and the print operation control means  324  determines that yellow ink has run out, the print operation control means  324  transfers a print control signal to the head drive means  325  so as to print in magenta ink or cyan ink, i.e., an ink that does not correspond to the detection signal received from the ink end detector. When one ink runs out, the print operation control means  324  determines which color to be used based on the data stored in the storage means  326 . 
   The ink jet printer  300  is thus controlled, whereby all inks stored in the ink cartridge  100  can be used up, useless ink can be reduced, and the running costs of the ink jet printer  300  can be decreased. 
   Fifth Embodiment—A Split-type Ink Cartridge 
   Next, an ink cartridge of another configuration incorporating the present invention will be discussed. The ink cartridge described below is a split-type ink cartridge having a structure that can be split up and down. 
     FIG. 18  is an external perspective view of the split-type ink cartridge of this embodiment as the ink cartridge is viewed from the top,  FIG. 19  is an external perspective view of the split-type ink cartridge of this embodiment as the ink cartridge is viewed from the bottom,  FIG. 20  is a longitudinal sectional view of the split-type ink cartridge, and  FIG. 21  is an exploded perspective view of the split-type ink cartridge. 
   Referring to the figures, an ink cartridge  400  includes a first ink cartridge  500  and a second ink cartridge  600 . The ink cartridge  500  is shaped like a flat rectangular parallelepiped in which a first ink bag  401 ( 1 ) and a waste-ink absorption material  402  are housed. Similarly, the second ink cartridge  600  is shaped like a flat rectangular parallelepiped in which a second ink bag  401 ( 2 ) is housed. The first and second ink cartridges detachably are joined in a state in which they are overlaid on each other. 
   The first ink cartridge  500  comprises a cartridge case  501  shaped like a flat rectangular parallelepiped, and the above-mentioned first ink bag  401 ( 1 ) and waste-ink absorption material  402  are housed in the cartridge case  501 . The cartridge case  501  includes a case main body  502  open on its top (upper opening  503 ) and a case lid  504  detachably covering the upper opening  503 . A front end face  505  of the cartridge case  501  is formed with an ink supply needle insertion hole  506  and a waste ink collection needle insertion hole  507 . A bottom  508  of the cartridge case  501  is formed with an opening  509  for allowing a detection projection to pass therethrough. Further, a detection projection protection cover  510 , extending downward, is formed in the main body case side portion positioned on the side of the opening  509 . In the cartridge case  501 , the first ink bag  401 ( 1 ) and the waste-ink absorption material  402  are arranged in this order in the case thickness direction from the bottom  508  of the cartridge case  501 . 
   The second ink cartridge  600  also comprises a cartridge case  601  shaped like a flat rectangular parallelepiped wherein the above-mentioned second ink bag  401 ( 2 ) is housed. The cartridge case  601  includes a case main body  602  opened to the top (upper opening  603 ) and a case lid  604  detachably covering the upper opening  603 . A front end face  605  of the cartridge case  601  is formed with an ink supply needle insertion hole  606 . Guide holes  611  and  612 , into which are inserted guide shafts of an ink jet printer (see  FIG. 29 ) as described later, are made in left and right end parts of the main body case front end face  605 . 
   A bottom  608  of the cartridge case  601  is formed with an opening  609  for allowing a detection projection to pass therethrough. The cartridge case  601  also includes a recess part  613  for inserting the detection projection protection cover  510  formed on the first ink cartridge  500 . The recess part  613  is formed in the main body case side portion positioned on the side of the opening  609  in the case thickness direction. 
   Next, the ink bags  401 ( 1 ) and  401 ( 2 ) are basically the same except for the ink storage capacity or stored ink and, therefore, the small-capacity ink bag  401 ( 1 ) storing colored ink will be discussed. Parts of the ink bag  401 ( 2 ) corresponding to those of the ink bag  401 ( 1 ) are denoted by the same reference numerals and will not be discussed again. The ink bag  401 ( 1 ) is formed of a flexible material, such as an aluminum laminate film comprising aluminum foil sandwiched between two films, with a nylon film as the outer film and a polyethylene film as the inner film for enhancing a gas barrier property. 
   For example, two aluminum laminate films are put on each other and are joined at their peripheries by a method of heat scaling, or the like, whereby a bag main body portion  461  of the ink bag  401 ( 1 ) is formed. An ink outlet part  462 , for removing ink stored in the ink bag, is attached to the front margin center of the bag main body portion  461  by a method of heat sealing, or the like. 
   The ink outlet part  462  is fixed to the front end face part of the cartridge case  501 , and the bag main body portion  461  is fixed to the bottom  508  of the cartridge case  501  with a double-faced adhesive, or the like. The other ink bag  401 ( 2 ) also has its ink outlet part  462  fixed to the front end face part of the cartridge case  601 , and has its bag main body portion  461  fixed to the bottom  608  of the cartridge case with a double-faced adhesive, or the like. 
   When the first ink cartridge  500  and the second ink cartridge  600  are joined and are overlaid on each other, as seen in  FIG. 20 , the ink outlet pan  462  of the ink bag  401 ( 1 ) and the ink outlet part  462  of the ink bag  401 ( 2 ) arc brought into direct contact with each other in the case thickness direction, and are fixed to the cartridge cases  501  and  601 . The configuration for fixing the cartridge cases and the ink bags is similar to the configuration previously described with reference to the accompanying drawing in the first embodiment of the ink cartridge having a partition plate. 
   Consequently, in the embodiment of the split-type ink cartridge, the ink outlet parts  462  and  462  are also stacked up and down on each other with the parts brought into direct contact with each other, so that the size of the ink cartridge  400  can be minimized and, particularly, the thickness of the ink cartridge  400  can be reduced. 
   A detection plate  463  is fixed to the ink bag  401 ( 1 ) by double-faced tape (not shown), or the like. The detection plate  463  is provided for detecting when the amount of ink remaining in the ink bag  401 ( 1 ) has decreased to a predetermined amount. A detection projection  464 , bent at right angles, is formed integrally with the detection plate  463  in a side margin thereof. The detection projection  464  penetrates the opening  509  and is extended into a through hole of the detection projection protection cover  510 . When the ink bag  401 ( 1 ) becomes thin with a decrease in the amount of ink remaining therein, the detection plate  463  accordingly falls toward the bottom  508 . Thus, the tip of the detection projection  464  projects downward from the rear of the second ink cartridge  600 . When the detection projection  464  projects, it is detected by an ink end sensor of the ink jet printer (described later), so that it is known when the ink runs out. 
   A detection plate  463  is also attached to the second ink bag  401 ( 2 ). A detection projection  464   a , formed in a side margin of the detection plate  463 , also passes through the opening  609  made in the bottom  608  and projects downward from the rear as the amount of ink remaining is decreased. Similarly to the situation with detection projection  464 , as the amount of ink remaining in bag  401 ( 2 ) decreases, the detection projection  464   a  projects downward and is detected by the ink end sensor placed in the ink jet printer (described later). 
   The detection plate  463  in this embodiment has the same contour shape as the detection plate  8  in the first embodiment of the ink cartridge having a partition plate. 
   If the detection projection  464  or  464   a  is detected by the common ink end sensor, which detection projection is detected is unknown. However, in this embodiment, the detection projection  464   a  is made narrower than the detection projection  464 , so that which of the ink cartridges  500  and  600  has become empty of ink can be immediately recognized by a visual inspection. Of course, the tip shapes of the detection projections may be made different, or the colors can be made different for producing a similar effect. 
   Next,  FIG. 22  is a perspective view showing the operation of attaching and detaching the first and second ink cartridges  500  and  600 .  FIGS. 23  to  25  are, respectively, a perspective view of the first ink cartridge  500  when the ink cartridge is viewed from the top, a perspective view of the first ink cartridge  500  when the ink cartridge is viewed from the rear, and a longitudinal sectional view of the first ink cartridge  500 . 
   First, a joint mechanism, which detachably joins the first and second ink cartridges, will be discussed with reference to the figures. The joint mechanism in this embodiment includes a recess  403  in which the first ink cartridge  500  can be placed, wherein the recess  403  is formed on the top of the second ink cartridge  600 , left and right snap fit parts  531  and  532  formed on both sides of the first and second ink cartridges  500  and  600 , and insertion parts  541  and  542  formed in the front end faces of the first and second ink cartridges  500  and  600 . 
   As seen in  FIG. 26 , the recess  403  is defined by side plate portions and end plate portions that extend upward from the four corner portions of the case lid  604  on the top of the second ink cartridge  600 . That is, left and right side plate portions  621  and  622  and left and right end plate portions  623  and  624  are formed on the front end side of the case lid  604  and, likewise, side plate portions  625  and  626  and end plate portions  627  and  628  are formed on the rear end side. The rear portion of the case main body  502 , of the first ink cartridge  500 , can be fitted into the recess  403  by inserting it from the upper side. 
   The snap fit parts  531  and  532  are formed between the side plate portions  625  and  626  on the rear end side, and the left and right side portions of the case main body  502  of the first ink cartridge  500  opposed to the side plate portions  625  and  626 . More particularly, the snap fit part  531  is made up of an engagement hole  533  in the case lid side plate portion  625  of the second ink cartridge  600 , and of an engagement projection  534  formed on the side portion  525  of the case main body  502  of the first ink cartridge  500 . If the rear end portion of the first ink cartridge  500  is pushed into the recess  403  of the second ink cartridge  600 , the side plate portion  625  and the side portion  525  are elastically displaced relative to one another and the engagement projection  534  is fitted into the engagement hole  533 , whereby the first and second ink cartridges are joined. The other snap fit part  532  has the same structure as the snap fit part  531  and, therefore, it will not be discussed again. 
   Insertion holes  543  and  544  are made in the front end plate portions  623  and  624  of the second ink cartridge  600 , and insertion projections  545  and  546  are formed at corresponding positions on the front end face  505  of the case main body  502  of the first ink cartridge  500 . Therefore, as shown in  FIG. 22 , if the front end portion of the first ink cartridge  500  is inserted into the recess  403  of the second ink cartridge  600  from the upper side and is pushed out forward, the insertion projections  545  and  546  are inserted into the corresponding insertion holes  543  and  544 , forming the left and right insertion parts  541  and  542 . 
   After this, as described above, if the rear end portion of the first ink cartridge  500  is pushed into the recess  403 , the left and right snap fit parts  531  and  532  are formed. Consequently, the first and second ink cartridges  500  and  600  are joined in a state in which they are overlaid on each other, in the case thickness direction. To separate the first and second ink cartridges  500  and  600 , if the left and right snap fit parts  531  and  532  are disengaged from each other and the rear end portions of the first and second ink cartridges  500  and  600  are separated as shown in FIG.  22  and then the first ink cartridge  500  is pulled relatively backward, the insertion parts  541  and  542  are detached and both ink cartridges  500  and  600  can be separated completely. 
   Thus, in the ink cartridge  400  of this embodiment, the first ink cartridge  500  is fitted into the recess  403  formed in the second ink cartridge  600 . Therefore, there is no risk that both ink cartridges  500  and  600  may relatively shift back and forth or left and right. Thus, when the ink cartridge  400  is placed in or detached from the cartridge placement section of the ink jet printer, relative movement between the first and second ink cartridges  500  and  600 —which relative movement would tend to separate the cartridges  500  and  600 —is prevented by the recess  403 . Therefore, when the ink cartridge  400  is attached or detached, the first and second ink cartridges  500  and  600  can be reliably prevented from shifting and being separated. 
   In this embodiment, the front end portions of the first and second ink cartridges  500  and  600  are joined in the insertion manner and then the rear end portions are joined in the snap fit manner, so that both ink cartridges  500  and  600  are easily positioned and can be easily joined. Further, there is no worry that the first and second ink cartridges  500  and  600  will be accidentally separated. 
   Next, referring mainly to  FIGS. 23  to  25 , the structures of the parts of the first ink cartridge  500  will be discussed. The case main body  502 , forming a part of the cartridge case  501 , has a rear end portion inclined so that an elongated rectangular knob recess  551 , which is triangular in cross section, is formed. Since the knob recess  551  is formed, if the first ink cartridge  500  is separated from the second cartridge  600 , it becomes easy to grasp the first ink cartridge  500  and the risk of dropping and breaking the first ink cartridge  500  is reduced. 
   The case lid  504 , attached to the opening  503  of the case main body  502 , is formed on the rear with a rectangular frame  552 . The waste-ink absorption material  402  is housed in a recess  553  formed by the rectangular frame  552 , and is sealed in the recess  553  with a plastic film  554 . 
   The case lid  504  is fitted into the opening  503  of the case main body  502 , and is formed on its front end portion with a pair of left and right insertion projections  555  and  556 , whereas the case main body  502  is formed on its front end face  505  with insertion holes  557  and  558  at the positions corresponding to the insertion projections  555  and  556 . Further, the case lid  504  and the case main body  502  are formed with engagement claws of snap fit type and engagement grooves in which can be fitted the engagement claws. The engagement claws are as previously described with reference to  FIG. 6  in the first embodiment of the ink cartridge. The case lid  504  is thus attached to the case main body  502  by engaging the engagement claws and engagement grooves. Thus, the case lid  504  is easily removed from the case main body  502 , so that the first ink cartridge  500  can be disassembled easily when it is recycled. 
   Next, referring mainly to  FIGS. 26  to  28 , the structure of the second ink cartridge  600  will be discussed. The case main body  602 , forming a part of the cartridge case  601 , has a rear end portion inclined so that an elongated rectangular knob recess  631 , which is triangular in cross section, is formed. Since the knob recess  631  is formed, the ink cartridge  400  is easy to grasp, and the risk of dropping and breaking the ink cartridge is reduced. Even after the second ink cartridge  600  is separated from the first ink cartridge  500 , the knob recess  631  can be used as a knob to grasp the second ink cartridge  600 . 
   The case lid  604 , attached to the opening  603  of the case main body  602 , is fitted into the opening  603  of the case main body  602  and is formed on its front end portion with a pair of left and right insertion projections  641  and  642 , whereas the case main body  602  is formed on its front end portion  605  with insertion holes  643  and  644  at corresponding positions. Further, the case lid  604  and the case main body  602  are formed with engagement claws of a snap-fit type and engagement grooves in which the engagement claws can be fit as with the first ink cartridge  500 . The case lid  604  is attached to the case main body  602  by engaging the engagement claws with the engagement grooves in an insertion manner. Thus, the case lid  604  is easily removed from the case main body  602 , so that the second ink cartridge  600  can also be disassembled easily when it is recycled. 
   The waste-ink holding capacity of the waste-ink absorption material  402  now will be discussed with reference to Tables 1 and 2. 
   Let the volume of color ink available until the detection projection  464  of the detection plate  463  fixed to the first ink bag  401 ( 1 ) is detected by an ink end sensor of ink jet printer (described later) be V 1 . 
   Likewise, let the volume of color ink available until the detection projection  464   a  of the detection plate  463  fixed to the second ink bag  401 ( 2 ) is detected by the ink end sensor of the ink jet printer be V 2 . 
   Let the number of ink nozzles of an ink jet head  709  (described later) for ejecting color ink be n 1  and the number of ink nozzles for ejecting black ink be n 2 . 
   If printing with color ink is not executed, a plurality of second ink cartridges  600  storing black ink (p second ink cartridges  600  in Table 1) can be used by the time one first ink cartridge  500  storing color ink is used up, as listed in Table 1. 
   That is, even when color ink is not used for printing, it is used during preliminary ejecting of the ink jet head  709 , and is also used during recovery processing of a head cap  712  and a waste ink pump  714  (described later), thereby producing waste ink. 
   In Table 1, the volume of color ink used as waste ink while the first ink cartridge  600  is used is shown as b 1  (cc), and the volume of black ink used for printing is shown as a 1  (cc). 
   Since the number of ink nozzles for ejecting black ink is (n 2 /n 1 ) times the number of ink nozzles for ejecting color ink, the volume of waste ink produced from black ink also becomes (n 2 /n 1 ) times the volume of waste ink produced from color ink. Thus, the waste ink volume of black ink produced while the first ink cartridge  600  is used can be represented as b 1 (n 2 /n 1 ) (cc). 
   Likewise, if the volume of color ink used as waste ink while the second ink cartridge  600  is used is shown as b 2  (cc), and the volume of black ink used for printing is shown as a 2  (cc), the waste ink volume of black ink can be represented asb 2 (n 2 /n 1 ) (cc). 
   A similar representation can also be made concerning thep&#39;th ink cartridge  600 . Thus, the following relational expressions hold as listed in Table 1: 
   Concerning the second (black ink) cartridge  600 , 
     a   1 + b   1 ( n   2 / n   1 )= a   2 + b   2 ( n   2   /n   1 )= . . . = ap+bp ( n   2 / n   1 )= V   2   
   Concerning the first (color ink) cartridge  500 ,
 
 b   1   +b   2   +. . . +bp=Σbi=V   1 
 
   Concerning the amount of waste ink produced,
 
Σ bi ( n   2   /n   1 )+Σ bi=Σbi (( n   1   +n   2 )/ n   1 )= V   1 (( n   1   +n   2 )/ n   1 )
 
   Next, to print also with color ink, it is assumed that q second ink cartridges  600  storing black ink are used by the time one first ink cartridge  500  storing color ink is used up, as listed in Table 2. Here, the relation of q&lt;p holds. If the volume of color ink used for printing—while the first ink cartridge  600  is used—is shown as c 1  (cc), and the volume of color ink used as waste ink is shown as e 1  (cc), and the volume of black ink used for printing is shown as d 1  (cc), the volume of black ink used as waste ink can be represented as e 1 (n 2 /n 1 ) (cc). 
   A similar representation can also be made concerning theq&#39;th ink cartridge  600 . Thus, the following relational expressions hold as listed in Table 2: 
   Concerning the second (black ink) cartridge  600 ,
 
 d   1 + c   1 ( n   2 / n   1 )= d   2   +e   2 ( n   2 / n   1 )= . . .  dq+eq ( n   2 / n   1 )= V 2
 
   Concerning the first (color ink) cartridge  500 ,
 
( c   1   + . . . +cq )+( e   1   +. . . +eq )=Σ ci+Σei=V   1 
 
   Concerning the amount of waste ink produced,
 
Σ ei ( n   2 / n   1 )+Σ ei=Σei (( n   1   +n   2 )/ n   1 )=(( n   1   +n   2 )/ n   1 )( V   1 −Σ ci )≦ V   1 (( n   1 + n   2 )/ n   1 )
 
   That is, in this embodiment, if the waste ink absorption material  402  has a waste-ink holding capacity S of V 1 ((n 1 +n 2 )/n 1 ) or more, waste ink does not leak. 
   The available color ink volume V 1  generally varies by about ±15%. As the capacity (volume) of the waste-ink absorption material  402  is smaller, it is more advantageous for miniaturization of the ink cartridge using the waste-ink absorption material  402 , and also more advantageous for the ink jet printer in which the ink cartridge is placed. Thus, it is desired that the waste-ink holding capacity S of the waste-ink absorption material  402  be 1.3 or less times V 1 ((n 1 +n 2 )/n 1 ). 
   Next, in contrast to the above-described embodiment, if the first ink bag  401 ( 1 ) housed in the first ink cartridge  500  stores black ink, the second ink bag  401 ( 2 ) housed in the second ink cartridge  600  stores color ink, the available black ink volume is V 2 , the available color ink volume is V 1 , the number of ink nozzles for ejecting black ink is n 2 , and the number of ink nozzles for ejecting color ink is n 1 , the amount of waste ink produce when printing with black ink is not executed—can be represented by the following expression:
 
 V   2 (( n   1   +n   2 )/ n   2 )
 
   Thus, in this case, if the waste ink absorption material has a waste-ink holding capacity M of V 2 ((n 1 +n 2 )/n 2 ) or more, waste ink does not leak. 
   Now will be discussed which of the following cases allows the waste-ink holding capacity to be smaller (i) where an ink bag storing color ink and a waste-ink absorption material are housed in one ink cartridge; or (ii) where an ink bag storing black ink and a waste-ink absorption material are housed in one ink cartridge.
 
 S/M =( V   1 ( n   1 + n   2 )/ n   1 )/( V   2 ( n   1 + n   2 )/ n   2 )=( V   1   /n   1)/(   V   2   /n   2 )
 
   The value resulting from dividing the available color ink volume V 1  by the number of ink nozzles for ejecting color ink, n 1 , is compared with the value resulting from dividing the available black ink volume V 2  by the number of ink nozzles for ejecting black ink, n 2 . If a waste ink absorption material is housed in the ink cartridge having the smaller value, the waste-ink holding capacity may be smaller. 
   That is, the waste ink absorption material is attached to the ink cartridge having the smaller value resulting from dividing the available ink volume by the number of ink nozzles for ejecting the corresponding ink, whereby the waste ink absorption material having the smaller waste-ink holding capacity can prevent waste ink from leaking. 
   Sixth Embodiment—An Ink Jet Printer using an Ink Cartridge  400  as an Ink Supply Source 
     FIG. 29  is a schematic configuration drawing showing an example of an ink jet printer in which the above-described split-type ink cartridge can be placed as an ink supply source. The basic configuration of an ink jet printer  700  of this embodiment is similar to that of a generally used ink jet printer and, therefore, is not shown, whereas only ink supply and discharge channels arc shown. Also, only the ink supply and discharge channels will be discussed. 
   Referring to  FIG. 29 , the ink jet printer  700  of this embodiment includes a cartridge placement section  703  in which the ink cartridge  400  detachably is placed. Two ink supply needles  704 ( 1 ) and  704 ( 2 ) and one waste ink collection needle  705  are attached to the cartridge placement section  703  so that they extend horizontally at the same height positions. If the needles  704 ( 1 ),  704 ( 2 ), and  705  respectively are inserted into the ink supply needle insertion holes  506  and  606  and the waste ink collection needle insertion hole  507  of the ink cartridge  400 , ink flow passages for supplying and discharging ink are formed between the ink cartridge  400  and the ink jet printer  700 . 
   When the ink flow passages arc formed, ink stored in the first ink bag  401 ( 1 ) and ink in the second ink bag  401 ( 2 ) arc taken out into ink supply tubes  707 ( 1 ) and  707 ( 2 ) through the ink supply needles  704 ( 1 ) and  704 ( 2 ). In the ink cartridge  400 , red colored ink, or the like, is stored in the first ink bag  401 ( 1 ), whereas black ink is stored in the second ink bag  401 ( 2 ). Thus, colored ink is supplied through the ink supply tube  707 ( 1 ) and black ink is supplied through the ink supply tube  707 ( 2 ). Filters  708 ( 1 ) and  708 ( 2 ) filter dust and foreign substances from the ink, and are placed at midpoints of the ink supply tubes  707 ( 1 ) and  707 ( 2 ). 
   Ink is introduced into an ink jet head  709 , of the ink jet printer  700 , through the ink supply tubes  707 ( 1 ) and  707 ( 2 ). The ink jet head  709  is mounted on a carriage (not shown) and is reciprocated in the length direction along the surface of a platen  711 . Record paper (not shown) is transported in a direction orthogonal to the ink jet head&#39;s movement direction along the surface of the platen  711 , and is printed with the ink jet head  709 . 
   To maintain the print quality of the ink jet head  709 , ink nozzles of the ink jet head  709  are cleaned by sucking ink therefrom (recovery processing). For this purpose, a head cap  712  is placed at a position out of a print area of the ink jet head  709 , and the ink jet head  709  periodically is moved to the position of the head cap  712 . A waste ink tube  713 , for collecting waste ink collected or sucked from the ink jet head  709  by way of the head cap  712 , is connected to the head cap  712 . A waste ink pump  714 , as a drive source for collecting waste ink, is connected to the waste ink tube  713 . 
   The waste ink passes through the waste ink tube  713  by action of the waste ink pump  714 . The waste ink then passes through the waste ink collection needle  705  and into the waste-ink absorption material  402  wherein it is collected and held. 
   Further in this embodiment, a cartridge presence/absence sensor  716  is attached to the cartridge placement section  703 , and detects placement or no placement of the ink cartridge  400  by sensing the front end face of the side where the color ink bag  401 ( 1 ) is housed in the ink cartridge  400 . Two ink end detectors  717  and  717   a  are attached to the cartridge placement section  703  and, when the detection projection  464  or  464   a  attached to the ink cartridge  400  is detected, produce an output indicating which of color ink and black ink remains only a little. In addition, two guide shafts  718  and  719 , for guiding placement of the ink cartridge  400 , are attached in the cartridge placement section. 
   The split-type ink cartridge  400  can be placed in the cartridge placement section  703  of the ink jet printer  700  with the first and second ink cartridges  500  and  600  together in one piece. Therefore, the ink cartridge attachment/detachment operation is easy as compared with the case where an ink cartridge for each color is placed or removed. 
   If the ink cartridge that becomes empty of ink is detected by the ink end sensor  717  or  717   a , only the ink cartridge that becomes empty of ink needs to be replaced, so that waste of ink—as is in an ink cartridge containing a plurality of ink bags—does not occur. 
   In this embodiment, black ink used in a large amount is filled into the large-capacity ink bag  401 ( 2 ) housed in the second ink cartridge  600  in which the waste-ink absorption material  402  is not housed, whereas color ink used in a small amount is stored in the first ink cartridge  500  in which the waste-ink absorption material  402  is housed. Therefore, the ink cartridge replacement frequency can be decreased as compared with the case where black ink is stored in the first ink cartridge  500 . 
   Also in this embodiment, the two guide shafts  718  and  719  horizontally project into the cartridge placement section  703 . Further, the guide shaft insertion holes  611  and  612 , into which the guide shafts  718  and  719  can be inserted, are made only in the front end face of the second ink cartridge  600 . Therefore, if the ink cartridge  400  is placed in the cartridge placement section  703  in an opposite direction left to right, the tip of the guide shaft  718 ,  719  abuts the front end face or the rear end face of the ink cartridge  400 . Thus, the ink cartridge  400  is prevented from being placed in the cartridge placement section  703  in an erroneous position. 
   According to the configuration of the split-type ink cartridge  400  and the cartridge placement section  703  in this embodiment, the first ink cartridge  500  alone can be placed in the cartridge placement section  703 . In this case, the cartridge presence/absence sensor  716  installed in the cartridge placement section  703  detects the first ink cartridge  500  as if the ink cartridge  400  were placed. If the ink jet printer  700  is driven in this state, the second ink cartridge  600  storing black ink is not placed and it is impossible to print in black ink, thus the operator immediately recognizes the state in which the second ink cartridge  600  is not placed. 
   The waste ink collection channel prevents the detrimental effect of leaking out waste ink to the outside. Of course, if two cartridge presence/absence sensors for detecting the first and second ink cartridges  500  and  600  are attached, when the operator forgets about placing the black ink cartridge  600 , he or she can be informed of the fact. 
   In this case, to reliably prevent waste ink from leaking from the waste ink absorption material, the waste ink absorption material is housed in the ink cartridge having the smallest value resulting from dividing the volume of ink stored in each ink cartridge by the number of ink nozzles of the ink jet-printer for ejecting the corresponding ink, whereby even with the smaller waste-ink holding capacity, waste ink can be reliably prevented from leaking. 
   The split-type ink cartridge  400  includes the waste-ink absorption material, but of course the invention can also be applied to a split-type ink cartridge having no waste-ink absorption material. Further, the waste-ink holding member for storing waste ink from the ink jet printer is not limited to the waste ink absorption material, but may be any if it can hold liquid waste ink, such as a bag, of course. 
   The split-type ink cartridge  400  includes two ink cartridges joined, but of course the invention can also be applied to a split-type ink cartridge comprising three or more ink cartridges joined together. 
   Further, waste ink—produced from the ink jet printer comprising a plurality of ink nozzle groups for separately ejecting different types of inks from a plurality of ink cartridges storing the inks, which cartridges can be attached and detached separately—can be held reliably with a small capacity. Therefore, the invention can also be applied to a plurality of ink cartridges wherein a waste-ink holding member for collecting and holding waste ink is placed in the ink cartridge having the smallest value resulting from dividing the volume of ink available to the ink jet printer, as stored in each ink cartridge, by the number of ink nozzle groups for ejecting the corresponding ink. 
   Further, to detect the ink end condition of each ink bag in the split-type ink cartridge  400 , the ink end condition detection mechanism shown in  FIGS. 13  to  17  and as described above can also be adopted intact. 
   The ink jet printer of the invention can also be applied to other machines that print, such as facsimile machines, or the like. 
   As described above, in the ink cartridge having a partition plate, a plurality of housed ink bags are overlaid on each other in the case thickness direction in a state in which their ink outlet parts are in direct contact with each other without sandwiching a partition plate between the ink outlet parts. Generally, the outer size of the ink outlet part is larger than the thickness of the ink bag when the ink bag main body is filled with ink, so that the ink cartridge can be thinned by placing no partition plate between the ink outlet parts, and thus it is advantageous for miniaturizing the ink cartridge. 
   The partition plate placed between the ink bags is mounted in a slidable state relative to the cartridge case, and is sandwiched between the case main body and the case lid forming the cartridge case, whereby the installation position of the partition plate is defined. Therefore, the partition plate can be easily installed and removed, whereby it is easy to disassemble and assemble the ink cartridge when the ink cartridge is recycled, and the like. 
   Further, the ink outlet parts of the ink bags overlaid on each other in the case thickness direction are pressed and fixed by a portion that can be elastically displaced in the case thickness direction, so that the ink outlet parts can be reliably fixed to their predetermined positions. Consequently, the ink supply needle can always be inserted into the appropriate position. 
   Further, the ink outlet parts of the ink bags placed in the case thickness direction are used to fix the partition plate, so that the partition plate holding each ink bag can be reliably fixed to the predetermined position. Consequently, the position of the ink bag held on the partition plate can also be defined with good accuracy, so that it is possible for the detection plate attached to the ink bag to detect, with good accuracy, when the ink runs out. 
   Next, in the split-type ink cartridge, the ink outlet parts of the ink bags housed in the first and second ink cartridges are overlaid on each other so that they are in direct contact with each other in the case thickness direction. Because of this direct contact, the ink cartridge can be miniaturized as compared with the case wherein each ink cartridge intervenes. 
   The first and second ink cartridges are joined in a detachable state. Therefore, the operation of attaching and detaching the ink cartridge (including multiple colors of ink) to and from the cartridge placement section of the ink jet printer can be performed easily and efficiently as compared with the case where two ink cartridges are attached and detached separately. 
   Further, if an ink cartridge becomes empty of ink, only the ink cartridge which becomes empty of ink needs to be replaced, so that the detrimental effect of replacing an ink cartridge wherein a large amount of ink remains in one ink bag as with the ink cartridge housing a plurality of ink bag—can be circumvented, and waste of ink can be reduced. 
   Further, the joint mechanism of the first and second ink cartridges includes a configuration which prevents a relative shift, so that the cartridges are reliably prevented from being accidentally detached from one another as they are inserted into, or removed from, the cartridge placement section. 
   In addition, the joint mechanism includes snap fit parts and the insertion parts, so that both ink cartridges can be easily aligned and joined. Further, the erroneous operation of forcibly joining both ink cartridges in an erroneous orientation can also be prevented. 
   Still further, the snap fit parts of the joint mechanism are formed in the side portions that are not touched by the operator operating the ink cartridge, and are not exposed to the outside. Therefore, there is little risk that the snap fit parts may be detached when the ink cartridge is attached or detached. If the ink cartridge is dropped by mistake, the risk of breaking the components of the snap fit parts is also small. 
   Also, in the ink cartridge of the invention, the contour shape and thickness of the detection plate attached to the ink bag are set so as to appropriately correspond to the contour shape of the bag main body of the ink bag. 
   Therefore, the amount of ink remaining when the ink end is detected can be reduced, so that the amount of wasted ink can be decreased. Since the detection plate can be moved in connection with the deformation of the ink bag as the amount of ink remaining decreases, ink end detection with good accuracy can be accomplished. 
   Moreover, the detection projections, to detect the ink amounts remaining in the first and second ink bags, are made different in shape or color so that it can easily and conveniently be recognized, by visual inspection, which of the ink cartridges becomes empty of ink. 
   In the split-type ink cartridge of the present invention, the waste-ink holding member—for collecting and holding waste ink entered therein from the outsides attached to the ink cartridge having the smallest value resulting from dividing the volume of ink available to the ink jet printer, as stored in each ink cartridge, by the number of ink nozzles of the ink jet printer for ejecting the corresponding ink. 
   Therefore, only one of the ink cartridges is provided with the waste-ink holding member, so that the whole volume of the ink cartridge is reduced whereby the ink cartridge can be miniaturized as compared with the case where every ink cartridge is provided with a waste-ink holding member. 
   In addition, the waste-ink holding capacity of the waste-ink holding member is set to the value resulting from multiplying (i) the volume of ink available to the ink jet printer, as stored in the ink cartridge having the waste-ink holding member, by (ii) the total number of ink nozzles of the ink jet printer divided by the number of the ink nozzles for ejecting the ink stored in the ink cartridge having the waste-ink holding member. 
   Therefore, even the waste-ink holding member having a smaller waste-ink holding capacity can reliably prevent waste ink from leaking from the waste-ink holding member.