Patent Publication Number: US-7708378-B2

Title: Ink cartridge, ink jet recording apparatus and waste-ink cartridge

Description:
FIELD OF THE INVENTION 
     The present invention relates to an ink cartridge for supplying ink to an ink jet type recording head that discharges ink from an array of nozzles arranged in a discharging surface, and an ink jet recording apparatus, which the ink cartridge is removably attached to. The present invention further relates to a waste-ink cartridge for storing waste-ink as collected by cleaning the recording head. 
     BACKGROUND ARTS 
     An ink jet recording apparatus has been known, which has a recording head for discharging ink as droplets onto a recording paper to print an image. The ink jet recording apparatus is provided with at least an ink container containing ink, to supply the ink from the ink container to the recording head. In an example, the recording head is provided with nozzles and an oscillation plate driven by a piezoelectric element. Making use of pressure change in the nozzles, which is caused by oscillating the oscillation plate, the ink is sucked from the ink container into the nozzles, and is discharged through ink outlets of the nozzles. Because the ink is a consumable material, the ink container is often formed as a cartridge that is removably attached to the ink jet recording apparatus, so that the ink may be supplied conveniently. 
     In the ink jet recording apparatus, the ink can stick to the ink outlets of the nozzles as it is dried to be viscous. Paper particles from the recording paper or dusts can also stick to the ink outlets. If the ink outlets are clogged with such obstacles, the recording head cannot discharge the ink, or ejects the ink in wrong direction. Besides that, if air bubbles enter inside the nozzles, ink discharging from the outlets becomes unstable. 
     To avoid these troubles, many of the ink jet recording apparatuses are provided with a capping mechanism that covers the outlets of the nozzles, as arranged on a discharging surface, with a cap while the recording head is at rest, to prevent the ink from being dried at the outlets, and/or a head cleaning device, such as a vacuum recovery mechanism that sucks viscous portions of the ink or air bubbles together with the ink out of the nozzles while covering the nozzles with a cap that is connected to a suction pump, or a wiping mechanism that wipes the obstacles like sticky ink and paper particles off the discharging surface, using an elastic wiper made of rubber or the like. 
     The ink sucked or wiped out of the recording head, hereinafter called waste-ink, is conventionally collected, for example through the suction pump, into a waste-ink container that is removably attached to the ink jet recording apparatus. The waste-ink container is changed with another when the waste-ink accumulated in the waste-ink container gets to a certain amount. In order to prevent spilling the waste-ink from the container as it is detached from the recording apparatus, Japanese Laid-open Patent Application No. Hei 10-244665 suggests inserting a high water absorbent polymer in the waste-ink container, so that the collected waste-ink is absorbed and coagulated by the polymer. 
     In order to make it easy and convenient for the user or operator to change the waste-ink container, it is desirable to form the waste-ink container as a cartridge, and insert a high water absorbent polymer or the like in the cartridge so as to prevent leakage of the waste-ink. 
     For the purpose of reducing load on the environment, the above-described ink cartridges are collected after use by the manufacturers, so as to recycle the containers of the used ink cartridges after disposing of the residual ink appropriately. As for the waste-ink container formed as a cartridge, hereinafter called the waste-ink cartridge, it is also desirable to collect and recycle the waste-ink cartridge after it is filled up with the waste-ink and removed from the ink jet printer. However, if the waste-ink is coagulated by the high water-absorbent polymer or the like in the waste-ink cartridge and the waste-ink cartridge has a tight case body for preventing leakage of the waste-ink, it is hard to take out the waste-ink from the waste-ink cartridge. In that case, the waste-ink cartridge must be disassembled to take out the waste-ink, which raises the requisite number of processes for recycling and thus raises the cost for recycling. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, a primary object of the present invention is to provide such a cartridge that stores waste-ink as collected from an ink jet type recording head, and securely prevents leakage of the waste-ink when the cartridge is removed from an ink jet recording apparatus, but facilitates recycling the removed cartridge. 
     Another object of the present invention is to provide an ink jet recording apparatus for use with the inventive cartridge. 
     A waste-ink cartridge of the present invention comprises a waste-ink storage portion for storing waste-ink collected by cleaning an ink jet type recording head, and an ink coagulant contained in the waste-ink storage portion, wherein the ink coagulant melts as heated up to a melting temperature and mixes with the stored waste-ink and, thereafter, solidifies the stored waste-ink as cooled. 
     The present invention also provides an ink cartridge for supplying ink to an ink jet type recording head that has nozzles to discharge the ink toward a recording material. The ink cartridge of the present invention comprises a recording ink storage portion storing the ink to be supplied to the recording head, a waste-ink storage portion for storing waste-ink collected by cleaning the recording head, and an ink coagulant contained in the waste-ink storage portion, wherein the ink coagulant melts as heated up to a given melting temperature and mixes with the stored waste-ink and, thereafter, solidifies the stored waste-ink as cooled. 
     The ink coagulant contained in the waste-ink storage portion preferably has a property that the ink coagulant and thus the solidified waste-ink are liquefied again as they are heated, and solidified again as they are cooled. 
     The ink coagulant is preferably made of at least one of agar, gelatin, karaginan and pectin. 
     According to a preferred embodiment, the recording ink storage portion and the waste-ink storage portion are provided by sectioning a case body of the ink cartridge into two chambers. 
     According to another preferred embodiment, the recording ink storage portion and the waste-ink storage portion are constituted of two ink bags contained in a case body of the ink cartridge. 
     An ink jet recording apparatus of the present invention, wherein outlets of nozzles of a recording head are arranged in a discharging surface, comprises a cartridge mounting section for removably mounting at least an ink cartridge that has a waste-ink storage portion for storing waste-ink collected from the recording head, the waste-ink storage portion containing an ink coagulant that melts as heated up to a given melting temperature and mixes with the stored waste-ink and, thereafter, solidifies the stored waste-ink as cooled; a head cleaning device for cleaning the recording head to collect the waste-ink and feed the collected waste-ink to the waste-ink storage portion of the ink cartridge as mounted to the cartridge mounting section; a heating device for heating the ink cartridge as mounted to the cartridge mounting section; and a temperature controller for driving the heating device to heat the ink cartridge till the ink coagulant is melted into the stored waste-ink. 
     The head cleaning device preferably comprises at least one of a vacuum smoothing mechanism for sucking the ink and any obstacles out of the nozzles, and a wiper for wiping the ink off the discharging surface, and feeds the ink sucked by the vacuum smoothing mechanism and/or the ink wiped off the discharging surface as the waste-ink to the waste-ink storage portion. 
     Where the ink cartridge has the waste-ink storage portion in addition to a recording ink storage portion storing the ink to be supplied to the recording head, the ink jet recording apparatus further comprises a detection device for detecting that the ink in the recording ink storage portion is used up. In that case, the temperature controller starts driving the heating device when the detection device detects that the ink is used up. 
     Since the waste-ink storage portion contains the ink coagulant that melts into the waste-ink as heated up to the melting temperature, and solidifies the waste-ink as cooled, the waste-ink is surely prevented from leaking if the waste-ink is solidified before the cartridge is removed from the ink jet recording apparatus. Because the solidified waste-ink and the ink coagulant are liquefied again as heated up to the melting temperature, it is easy to take out them from the waste-ink storage portion, which facilitates recycling the cartridge. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects and advantages of the present invention will be more apparent from the following detailed description of the preferred embodiments when read in connection with the accompanied drawings, wherein like reference numerals designate like or corresponding parts throughout the several views, and wherein: 
         FIG. 1  is an explanatory diagram illustrating essential elements of an ink jet recording apparatus according to an embodiment of the invention; 
         FIG. 2  is an explanatory diagram illustrating an ink cartridge and a head cleaning unit of the ink jet recording apparatus; 
         FIG. 3A ,  3 B and  3 C are sectional views of the ink cartridge, illustrating different stages of reaction between waste-ink and an ink coagulant; 
         FIG. 4  is an explanatory diagram illustrating an ink cartridge having an ink bag and a waste-ink bag, according to another embodiment of the invention; and 
         FIG. 5  is an explanatory diagram illustrating an ink cartridge that is provided with a thermal fuse, according to another embodiment of the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An ink jet recording apparatus  10  shown in  FIG. 1  is provided with a recording head  12  that discharges ink toward a paper sheet  11  to print images thereon. The recording head  12  is provided with a plurality of nozzles for discharging the ink from individual outlets. The outlets of the nozzles are aligned according to colors in a plane to form a discharging surface, and the discharging surface is placed in face to a recording surface of the paper sheet  11 . The recording head  12  is mounted in a carriage  13  that is movable in a widthwise direction of the paper sheet  11 , that is, a main scanning direction X. The discharging surface is exposed through an opening formed through a bottom of the carriage  13 . While reciprocating together with the carriage  13  in the widthwise direction of the paper sheet  11 , the recording head  12  records an image in a line sequential fashion. Each time the recording head  12  makes one lap to record a line of the image, the recording paper  11  is fed by not-shown conveyer rollers in a sub scanning direction Y, which is orthogonal to the main scanning direction X, by a length corresponding to a width of each image line as recorded by the recording head  12 . Thus, a frame of image is recorded line after line. 
     The carriage  13  is mounted on a pair of guide rods  14   a  and  14   b  to slide thereon, and is driven by a belt mechanism  17  consisting of a belt  15  and a pair of pulleys  16 . One end or terminal area of the belt mechanism  17  is defined as a home position where the discharging surface of the recording head  12  does not face the paper sheet  11 . As shown by phantom lines in  FIG. 1 , the carriage  13  is held in the home position while the ink jet recording apparatus  10  is at rest, e.g., while it is disconnected from a power source or in a standby state. While the recording head  12  is recording an image, the carriage  13  moves out of the home position and reciprocate in the main scanning direction X across a recording area where the recording head  12  faces the paper sheet  11 . 
     The ink jet recording apparatus  10  is provided with a cartridge mounting section  19  for mounting ink cartridges  21 , e.g. four ink cartridges containing inks of four different colors: yellow, magenta, cyan and black. The cartridge mounting section  19  is provided with four slots  19   a , into which the four ink cartridges  21  are removably plugged. In the recording head  12 , oscillation plates are provided in correspondence to the respective nozzles. The oscillation plates are driven individually by piezoelectric elements, to change pressure inside the tube  32 . Thereby, the ink in the ink cartridge  21  is sucked into the nozzles, and is ejected from the outlets of the nozzles. 
     In the home position, the discharging surface of the recording head  12  is opposed to a head cleaning unit  18 , which wipes the ink, paper particles and dusts off the discharging surface, and sucks sticky ink and air bubbles out of the nozzles to prevent clogging of the nozzles. The head cleaning unit  18  cleans the discharging surface at predetermined timings, e.g. immediately after the recording head  12  is powered on, and immediately before and after the image recording operation. The head cleaning unit  18  collects the ink as removed from the recording head  12 , hereinafter called waste-ink, and other obstacles, and drains them toward the ink cartridge  21 . 
     As shown in  FIG. 2 , a hollow case body  22  of the ink cartridge  21  is divided by a partition wall  23  into an upper chamber  24  and a lower chamber  25 . The upper chamber  24  is used as a recording ink storage chamber  24  for storing the ink to be supplied to the recording head  12 , whereas the lower chamber is used as a waste-ink storage chamber  25  for storing the waste-ink as collected by the head cleaning unit  18 . Since the ink cartridge  21  of this embodiment not only supplies the ink but also accepts the waste-ink, the user has only to change the ink cartridge  21  when the ink in the recording ink storage chamber  24  is used up. Disposal of the waste-ink may be done simultaneously with recycling of the used-up ink cartridge  21 . Although the partition wall  23  divides the case body  22  substantially into halves in the illustrated embodiment, the position of the partition wall  23 , i.e. the ratio in volume between the recording ink storage chamber  24  and the waste-ink storage chamber  25 , may be defined appropriately according to an estimated amount of waste-ink to be collected from one ink cartridge  21 . 
     On one side of the case body  22 , there are provided an ink outlet for letting the recording ink out of the recording ink storage chamber  24 , a waste-ink inlet  27  for letting the waste-ink into the waste-ink storage chamber  25 , an air inlet  28  for letting the air into the recording ink storage chamber  24  by an amount corresponding to the ink supplied to the recording head  12 , and a vent hole  29  for keeping pressure inside the waste-ink storage chamber  25  equal to atmospheric pressure. Each of the outlet  26 , the inlet  27  and the air inlet  28  consists of a hole formed through the one side of the case body  22 , and a cylindrical sheave protruding outward from the rim of the hole. The case body  22  is made of a transparent plastic or the like, so that the recording ink and the waste-ink in the respective chambers  24  and  25  are visible from outside. In order to hinder leakage of the ink from the chambers  24  and  25 , the ink outlet  26 , the waste-ink inlet  27  and the air inlet  28  are mounted individually with a filter formed from a porous material and a valve mechanism, though they are omitted from the drawings. 
     The recording ink storage chamber  24  is also provided with a not-shown prism used for detecting that the recording ink is used up. The prism is located on the opposite side from the ink outlet  26 , near the bottom of the recording ink storage chamber  24 . The peak of the prism is oriented inward of the recording ink storage chamber  24 . A residual ink detection sensor  58  is disposed in the ink jet recording apparatus  10 , in a position facing to the prism of the ink cartridge  21  as plugged in the slot  19   a . As an example, the residual ink detection sensor  58  is a photo-interrupter that consists of a light emitter for emitting light toward the prism, and a light receiver for receiving light reflected from the prism. The residual ink detection sensor  58  outputs a signal whose level corresponds to the volume of the reflected light from the prism. With a change in the ink level in the recording ink storage chamber  24 , the volume of the reflected light from the prism changes, so the ink jet recording apparatus  10  detects based on the signal level from the residual ink detection sensor  58  that the recording ink storage chamber  24  is running out of the ink. 
     The waste-ink storage chamber  25  contains an ink coagulant  30  for coagulating the waste-ink after it is fed into the waste-ink storage chamber  25 . The ink coagulant  30  is initially contained as a dry solid material, and has a property that it melts as heated up to a certain temperature, and gets solid as cooled. The ink coagulant  30  is water-soluble, so it is dissolved in the waste-ink when the ink coagulant  30  is heated and melted after the waste-ink is fed in the waste-ink storage chamber  25 . As the mixture of the ink coagulant  30  and the waste-ink cools down, it is solidified into gel. The gelled mixture of the ink coagulant  30  and the waste-ink may be repeatedly melted and solidified by heating and cooling it. 
     Therefore, if the waste-ink is coagulated when the ink cartridge  21  is removed from the slot  19   a , the waste-ink is surely prevented from leaking. In view of the environmental safety of the waste disposal, it is preferable to use as the ink coagulant  30  a naturally-derived material, such as agar, gelatin, karaginan or pectin. Beside the natural materials, water-soluble resin materials that are melted and solidified by heating and cooling them, e.g. SBR (styrene-butadiene rubber) are usable as the ink coagulant  30 . Instead of the solid ink coagulant  30 , powdery or flaky ink coagulant is usable. 
     Heat radiation fins  31  are provided on the same side of the case body  22  as the ink outlet  26  and  27  are formed. The heat radiation fins  31  are located in opposition to the waste-ink storage chamber  25 , so as to promote heat radiation on cooling the melted ink coagulant  30 . The heat radiation fin  31  may be formed from a material with high heat conductivity, like a metal, and then affixed to the case body  22 . The heat radiation fin  31  may also be formed integrally with the case body  22 . 
     Referring back to  FIG. 1 , the cartridge mounting section  19  is provided with fitting holes  19   b ,  19   c  and  19   d , which are respectively fitted on the ink outlet  26 , the waste-ink inlet  27  and the air inlet  28  as the ink cartridge  21  is plugged in the individual slot  19   a . The fitting hole  19   b  is connected through a tube  32  to the recording head  12 , whereas the fitting hole  19   c  is connected through a tube  33  to the head cleaning unit  18 , and the fitting hole  19   d  is connected through an L-shaped air duct  34  to an air introduction hole  19   e  that is formed on a top side of the cartridge mounting section  19 . Furthermore, the fitting holes  19   b ,  19   c  and  19   d  are respectively provided with hollow accessing needles  35 ,  36  and  37 , which constitute a section of the tube  32  or  33  or the air duct  34  respectively. As the ink cartridge  21  is plugged in the slot  19   a , the accessing needles  35 ,  36  and  37  stick into the ink outlet  26 , the waste-ink inlet  27  and the air inlet  28 , respectively, to protrude into the chambers  24  and  25 . Thus, the recording ink storage chamber  24  is connected to the recording head  12  through the accessing needle  35  and the tube  32 , whereas the waste-ink storage chamber  25  is connected to the head cleaning unit  18  through the accessing needle  36  and the tube  33 . 
     The cartridge mounting section  19  is also provided with heaters  38  and cooling fans  39  which are arranged in correspondence with the respective slots  19   a . Each of the heaters  38  comes into contact with the bottom of the ink cartridge  21  as the ink cartridge  21  is plugged in the slot  19   a , and heats the ink coagulant  30  as contained in the waste-ink storage chamber  25  upon an electric voltage being applied. Each of the cooling fans  39  is opposed to the heat radiation fins  31  as the ink cartridge  21  is plugged in the slot  19   a , and blows the heat radiation fins  31  to cool the ink coagulant  30 . 
     The heaters  38  and the cooling fans  39  are connected to a temperature controller  40 . When a command for coagulating the waste-ink, the temperature controller  40  applies the voltage to the heater  38  to melt the ink coagulant  30  and thereafter drives the cooling fan  39  to cool and solidify the ink coagulant  30 . The temperature controller  40  drives the heaters  38  and the cooling fans  39  individually at timings predetermined according to physical properties of the ink coagulant  30 , such as melting temperature, solidification temperature and heat capacity of the ink coagulant  30 , capacity of the heater  38  and air volume of the cooling fan  39 . 
     The head cleaning unit  18  has a number of caps  50  and a wiper  51 . The caps  50  are formed from an elastic material like rubber, and are positioned to face the discharging surfaces of the respective colors while the recording head  12  is in the home position. The caps  50  are movable up and down by use of a not-shown mechanism, and are brought into contact with the recording head  12  after the recording head  12  is moved to the home position. Thus, the individual caps  50  cover the counterpart discharging surfaces to prevent evaporation or drying of the ink in the nozzles while the recording head  12  is at rest. 
     The wiper  51  consists of an elastic blade  52  made of rubber or the like, and a holder  53  holding the blade  52 . The wiper  51  is placed on one side of the caps  50  in a moving direction of the carriage  13 , and is adjusted in height such that a top edge of the blade  52  a little touches the discharging surface as the carriage  13  moves with the recording head  12  over the wiper  51 . Thus, each time the carriage  13  moves from the home position to the recording area and moves back to the home position, the blade  52  wipes the discharging surfaces. Note that the blade  52  has a width extending across the discharging surfaces of the respective colors in a horizontally crossing direction to the moving direction of the carriage  13 , though it looks like a rod from its sectional contour shown in  FIG. 2 . The wiper  51  is not limited to the illustrated embodiment. It is possible to make the wiper  51  movable up and down so as to wipe the discharging surface only when it is required. It is also possible to move the wiper  51  itself for wiping. 
     The tube  33  interconnecting between the head cleaning unit  18  and the fitting hole  19   c  is branched into two tubes  33   a  and  33   b  in the head cleaning unit  18 , which are connected to the cap  50  and the wiper  51 , respectively. The head cleaning unit  18  is further provided with a pump  54  for changing pressure inside the tube  33  to push the fluid in the tube  33  toward the waste-ink storage chamber  25 . 
     The tube  33   a  is put through the cap  50  and connected to a recess  50   a  of the cap  50 , so as to transmit the pressure variation of the pump  54  to the recess  50   a . By driving the pump  54  while pressing the cap  50  onto the recording head  12 , the waste-ink is sucked out of the nozzles and fed to the waste-ink storage chamber  25  of the associated cartridge  21 . That is, the cap  50  and the pump  54  constitute a vacuum smoothing mechanism. On the other hand, the tube  33   b  is connected to a groove  53   a  between the holder  53  and the blade  52 . The waste-ink sticking to the discharging surface of the recording head  12  is wiped off by the blade  52  with the movement of the carriage  13 . The waste-ink wiped drains along the blade  52  into the groove  53   a . So the waste-ink pooled in the groove  53   a  is sucked and sent to the waste-ink storage chamber  25  of the associated cartridge  21  also by driving the pump  54 . Valves  55  and  56  are disposed in the tubes  33   a  and  33   b , so as to switch on or off the transmission of the pressure change to the cap  50  and the wiper  51 , as caused by the pump  54 . Since the wiper  51  is commonly used for wiping all the discharging surfaces of the recording head  12 , the wiper  51  may be connected to the waste-ink storage chamber  25  of only one of the ink cartridges  21  through the tube  33   b . The tubes  33  as connected to other ink cartridges  21  are not branched, but connected to the caps  50  alone. 
     In the above embodiment, the caps  50  are provided for the discharging surfaces of the respective colors, so the waste-ink of each color is sucked out from the nozzles and collected in the waste-ink storage chamber  25  of the corresponding ink cartridge  21 . However, it is possible to use a single cap that covers the discharging surfaces of all colors. In that case, the cartridge mounting section  19  may be provided with a device for delivering the waste-ink equally to the respective waste-ink storage chamber  25  of the ink cartridges  21 . 
     Now the operation of the ink jet recording apparatus of the above embodiment will be described with reference to  FIGS. 2 and 3 . 
     When the ink cartridge  21  having the recording ink storage chamber  24  and the waste-ink storage chamber  25  is plugged in the slot  19   a  of the cartridge mounting section  19 , the recording ink storage chamber  24  is connected to the recording head  12  through the accessing needle  35  and the tube  32 , and the waste-ink storage chamber  25  is connected to the head cleaning unit  18  through the accessing needle  36  and the tube  33 . 
     While the recording head  12  is at rest and not printing, the carriage  13  is held in the home position, and the caps  50  cover up the discharging surfaces of the recording head  12 , to prevent evaporation of the recording ink in the nozzles. Immediately before and after the printing, as well as when a head cleaning command is entered, the head cleaning unit  18  opens the valve  55  and closes the valve  56  and then drives the pump  54 . So the pump  54  sucks the sticky waste-ink and other obstacles out of the nozzles through the caps  50 . The sucked waste-ink is fed through the tube  33  and the accessing needle  36  to the waste-ink storage chamber  25  of the ink cartridge  21 . 
     When a printing command is entered, the carriage  13  begins to move from the home position to the recording area, and the blade  52  of the wiper  51  wipes the waste-ink off the discharging surfaces of the recording head  12 . The wiped waste-ink drains along the blade  52  into the groove  53   a . At a predetermined timing, e.g. when the carriage  13  moves completely into the recording area, the head cleaning unit  18  closes the valve  55  and opens the valve  56 , and thereafter drives the pump  54 . Then, the pump  54  sucks the waste-ink from the groove  53   a , and sends it to the waste-ink storage chamber  25 . Thus, the waste-ink as collected by the head cleaning unit  18  is stored in the waste-ink storage chamber  25 . 
     Responsive to the printing command, the recording head  12  applies voltage to those piezoelectric elements corresponding to the pixels to record, so the associated oscillation plates are driven to change pressure inside the tube  32  to suck the recording ink from the recording ink storage chamber  24 . The sucked recording ink is ejected from the outlet of the nozzles onto the paper sheet  11 . The ink jet recording apparatus  10  drives the recording head  12  while moving the carriage  13  in the main scanning direction X across the recording area, and conveying the paper sheet  11  in the sub scanning direction Y. Thus, an image frame is printed on the paper sheet  11 . 
     As the recording head  12  continues printing, the recording ink in the recording ink storage chamber  24  is finally used up, as shown in  FIG. 3A . When the residual ink detection sensor  58  detects that the recording ink is used up, the ink jet recording apparatus  10  commands the temperature controller  40  to coagulate the waste-ink. Then, the temperature controller  40  applies a voltage to the heater  38  to heat the ink coagulant  30  up to its melting temperature at the predetermined timings. The melted ink coagulant  30  is mixed with the waste-ink, as show in  FIG. 3B . After the ink coagulant  30  and the waste-ink are mixed up, the temperature controller  40  turns off the heater  38  to stop heating, and then drives the cooling fan  39  to start blowing the heat radiation fins  31  to cool the ink coagulant  30 . As being cooled, the ink coagulant  30  is coagulated again to solidify the waste-ink into gel, as shown in  FIG. 3C . 
     While solidifying the waste-ink, the ink jet recording apparatus  10  displays a message on a not-shown display device, to notify the user of the fact that one of the ink cartridges  21  has run out of the recording ink. Instead of displaying the message, it is possible to warn the ink run-out by use of a lamp or an LED, or acoustically by a speaker or the like. 
     Since the waste-ink is coagulated by the ink coagulant  30  when the user takes out the ink cartridge  21 , the waste-ink would not leak out of the ink cartridge  21  through the accessing needle  36  or the vent hole  29 . So the user can change the ink cartridge  21  with ease. By heating the used-up ink cartridge  21  after it is removed from the printer, the gelled mixture of the waste-ink and the ink coagulant  30  is liquefied again, making it easy to drain the waste-ink and the ink coagulant  30  out of the case body  22  through the waste-ink inlet  27  just by removing the filter and the valve mechanism from the waste-ink inlet  27 . Accordingly, the case body  22  is easy to reuse or recycle. Furthermore, it is possible to reuse or recycle the ink coagulant  30  by separating the ink coagulant  30  from the waste-ink through washing, heating and drying processes. 
     Moreover, if a high water absorbent polymer is used as a coagulant for the waste-ink, and the solidified waste-ink is not properly treated but incinerated with combustible rubbish, it would produce hazardous substances like dioxin. On the contrary, according to the present embodiment, a naturally-derived material, such as agar, gelatin, karaginan or pectin, is usable as the ink coagulant  30 . So the gelatinized waste-ink would not produce any hazardous substances even if it is incinerated. 
     In the above embodiment, the waste-ink is solidified when the output signal from the residual ink detection sensor  58  shows that the recording ink in the recording ink storage chamber  24  is used up. But the timing of solidifying the waste-ink is not limited to this embodiment. For example, it is possible to solidify the waste-ink each time the pump  54  of the head cleaning unit  18  is driven to suck and feed the waste-ink into the waste-ink storage chamber  25 . This method eliminates the risk that the waste-ink can leak if the ink cartridge  21  is removed from the printer  10  before the residual ink detection sensor  58  detects the ink run-out. It is alternatively possible to count the number of times the pump  54  is driven, and estimate based on the count the amount of the waste-ink stored in the waste-ink storage chamber  25 , so as to execute the solidification when the amount of the stored waste-ink reaches a predetermined value, e.g. a value permitting the ink coagulant  30  to coagulate the waste-ink. According to this alternative, the number of times driving the heater  38  and the cooling fan  39  is limited to a requisite minimum, so the power consumption is reduced. 
     Although the case body  22  of the ink cartridge  21  is sectioned by the partition wall into the upper recording ink storage chamber  24  and the lower waste-ink storage chamber  25 , it is alternatively possible to provide two flexible bags for containing the recording ink and the waste-ink, as show in  FIG. 4 , wherein like components are designated by the same reference numerals, so the detailed description of these components is omitted. 
     An ink cartridge  60  shown in  FIG. 4  consists of a recording ink bag  61  containing a recording ink, a waste-ink bag  62  for containing the waste-ink, and a case body  63  encasing and protecting these ink bags  61  and  62 . The case body  63  has on its one side an ink outlet  64  for letting the recording ink out of the recording ink bag  61 , and a waste-ink inlet  65  for letting the waste-ink into the waste-ink bag  62 . Openings of the respective ink bags  61  and  62  are joined from inside to the ink outlet  64  and the waste-ink inlet  65 . An air inlet  66  is formed through the same side of the case body  22  as the ink outlet  64  and the waste-ink inlet  65 . The air inlet  66  keeps pressure inside the case body  63  at atmospheric pressure. The waste-ink bag  62  contains a solid ink coagulant  30 , like the waste-ink storage chamber  25  of the first embodiment. The waste-ink bag  62  is affixed to an inner bottom surface of the case body  63 , for example by an adhesive agent, so that the heat from a heater  38  may be efficiently transmitted to the ink coagulant  30 . 
     Using the ink cartridge  60 , the waste-ink, which is collected from a recording head  12  by a head cleaning unit  18 , is stored and solidified into gel in the waste-ink bag  62 , by heating and cooling the ink coagulant  30 . So the embodiment shown in  FIG. 4  achieves the same effect as the first embodiment. In addition to that, the recording ink bag  61  deflates as the contained ink is consumed, whereas the waste-ink bag  62  swells as the waste-ink is fed into it. That is, the volumes of the ink bags  61  and  62  change oppositely to each other. Accordingly, it is possible to exploit the internal space of the case body  63  efficiently to minimize the ink cartridge  60 . 
     In the above-described embodiment, the temperature controller  40  drives the heater  38  and the cooling fan  39  at the timings predetermined according to physical properties of the ink coagulant  30 , capacity of the heater  38  and air volume of the cooling fan  39 . According to another embodiment, as shown in  FIG. 5 , an ink cartridge  70  is provided with a thermal fuse  71 , so as to drive a heater  38  and a cooling fan  39  when the thermal fuse  71  melts down. 
     The thermal fuse  71  is built in a case body  72  of the ink cartridge  70 , and has a fusible alloy that melts down at a melt-down temperature that is predetermined according to the melting temperature of an ink coagulant  30 . So the fusible alloy melts down when the ink coagulant  30  is heated up to melt by the heater  38 . Two wires are led from the thermal fuse  71  to a couple of contact terminals  73   a  and  73   b , respectively. The contact terminals  73   a  and  73   b  are built in a bottom portion of the case body  72 . In correspondence with the contact terminals  73   a  and  73   b , a couple of contact terminals  81   a  and  81   b  are built in a cartridge mounting section  80 , so that the contact terminals  73   a  and  73   b  come into contact with the contact terminals  81   a  and  81   b  respectively as the ink cartridge  70  is plugged in a slot of the cartridge mounting section  80 . 
     The contact terminal  81   a  is connected to one terminal of the heater  38 , whereas the contact terminal  81   b  is connected to the temperature controller  40 . The other terminal of the heater  38  is connected through a wire to the temperature controller  40 . Thus, only while the ink cartridge  70  is mounted in the cartridge mounting section  80 , the heater  38  is connected to the temperature controller  40  through the contact terminals  73   a ,  73   b ,  81   a  and  81   b  and the thermal fuse  71 . So the thermal fuse  71  constitutes a section of the circuit interconnecting between the heater  38  and the temperature controller  40 . 
     Upon a command for solidifying the waste-ink, the temperature controller  40  first applies a voltage to the heater  38  to heat the ink coagulant  30 . When the ink coagulant  30  is heated up to the melting temperature and is mixed with the waste-ink in a waste-ink storage chamber  25  of the ink cartridge  70 , the thermal fuse  71  melts down. As the thermal fuse  71  melts down, the heater  38  is disconnected from the temperature controller  40 , so the heater  38  stops heating. The meltdown of the thermal fuse  71  is detected by the temperature controller  40 , for example, by monitoring current or voltage. Then, the temperature controller  40  starts driving the cooling fan  39 , to cool the ink coagulant  30 . 
     In the first embodiment, the heater  38  and the cooling fan  39  are driven at the predetermined timings, so there is a risk that the ink coagulant  30  cannot reach the melting temperature or can be excessively heated due to variations in environmental temperature or humidity. If the ink coagulant  30  does not reach the melting temperature, it cannot mix well with the waste-ink. If the ink coagulant  30  is heated too much, the properties of the ink coagulant  30  will change. According to the embodiment shown in  FIG. 5 , because the ink cartridge  70  is provided with the thermal fuse  71 , of which meltdown temperature corresponds to the melting temperature of the ink coagulant  30 , the thermal fuse  71  melts down to stop the heater  38 , so the risk of insufficient or excessive heating of the ink coagulant  30  is eliminated. Moreover, because the thermal fuse  71  prevents the excessive heating of the ink coagulant  30  and the waste-ink, the ink cartridge  70  contributes to improving the safety of the ink jet recording apparatus  10 . 
     Instead of the thermal fuse  71 , it is possible to provide a fusible member in the wiring from the contact terminal  73   a  to the contact terminal  73   b , which is built in the ink cartridge  70 . The fusible member is made of a material fusible at a temperature corresponding to the melting temperature of the ink coagulant  30 , e.g. a low-melting point resin. Then, the fusible member is fused to disconnect the wiring when the case body  72  reaches a certain temperature. 
     Although the ink coagulant  30  is previously contained in the waste-ink storage chamber  25  or in the waste-ink bag  62  in the above embodiment, it is possible to mix a powdery ink coagulant previously in the recording ink. According to this embodiment, the content of the ink coagulant in the recording ink is constant, so the gelatinized mixture of the waste-ink and the ink coagulant is always kept in the same condition. 
     In the above embodiment, the heater  38  is used merely for solidifying the waste-ink. But it is possible to use the heater  38  for heating the recording ink while the recording head  12  is printing an image. Heating the recording ink lowers the viscosity of the recording ink and thus reduces the viscous resistance of the recording ink to the tubes. As a result, stability on supplying the recording ink to the recording head  12 , as well as on ejecting the recording ink from the nozzles is improved. 
     Although the present invention has been described with respect to those ink cartridges where the recording ink storage chamber and the waste-ink storage chamber are integrated into the same ink cartridge, the present invention is not to be limited to these embodiments. It is possible to provide a waste-ink cartridge that previously contains the ink coagulant  30  separately from an ink cartridge that contains the recording ink as usual, and mount the waste-ink cartridge and the ink cartridge in the ink jet recording apparatus of the present invention. 
     Thus the present invention is not to be limited to the above-described embodiments, but various modifications will be possible without departing from the scope of claims as appended hereto.