Abstract:
An inkjet printing apparatus is provided. The inkjet printing apparatus includes a recording head, which ejects ink onto s recording medium, an ink cartridge, which contains the ink therein, an ink cartridge storage to store the ink cartridge, an ink conveyer tube, which connects the recording head and the ink cartridge to convey the ink, a releasing system, arranged in the ink conveyer tube to switch an open state and a closed state, a release controller, which controls switching of the releasing system, and a judging system, which judges as to whether the ink in the ink conveyer tube is capable of being withdrawn in the ink cartridge. The release controller switches the releasing system in the open state to be in the closed state when the judging system judges that the ink is incapable of being withdrawn in the ink cartridge.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority from Japanese Patent Application No. 2009-008509, filed on Jan. 19, 2009, the entire subject matter of which is incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    An aspect of the present invention relates to an inkjet printing apparatus, specifically to an inkjet printing apparatus configured to collect ink from an inkjet head and an ink tube and to store the ink in an ink cartridge. 
         [0004]    2. Related Art 
         [0005]    Conventionally, an inkjet printer, which is equipped with a means to collect the ink adhered to the inkjet head and remaining in the ink tube therefrom and a means to store store the collected ink in the ink cartridge, has been known. 
         [0006]    For example, an inkjet printer having a cleaning mechanism to clean an ink conveyer path, which is between an ink supplier tube and a sub tank, is known. The ink remaining in the ink conveyer path is collected and stored in the ink cartridge. The ink cartridge is settled in a lower position with respect to the sub tank in a direction of gravity force; therefore, when an ink supplier valve provided in the ink conveyer path opens, the ink flows back from the sub tank to the ink cartridge. Thus, the reversed ink is collected and stored in the ink cartridge. Thereafter, by an operator, the ink cartridge can be manually replaced with a cleaner cartridge. Cleaner liquid prepared in the cleaner cartridge is drawn in the ink conveyer path, and accordingly, the ink conveyer path is cleaned. 
       SUMMARY 
       [0007]    However, in the inkjet printer configured as above, the operator may, for example, accidentally remove the ink cartridge from the inkjet printer during the ink-collecting operation. Therefore, the path for the reversed ink is disconnected, and the ink may flow out of the ink tube and leak in and out of the inkjet printer. 
         [0008]    In view of the above drawbacks, the present invention is advantageous in that an inkjet printing apparatus, in which leakage of the ink out of the ink tube upon removal of the ink cartridge can be prevented, is provided. 
         [0009]    According to an aspect of the present invention, an inkjet printing apparatus to form an image on a recording medium according to print data representing the image, is provided. The inkjet printing apparatus includes a recording head, which ejects ink onto the recording medium, an ink cartridge, which contains the ink therein, an ink cartridge storage to store the ink cartridge, an ink conveyer tube, which connects the recording head and the ink cartridge to convey the ink, a releasing system, which is arranged in the ink. conveyer tube to switch an open state in which air flow in the ink conveyer tube is released and a closed state in which the air flow in the ink conveyer tube is shut down, a release controller, which controls switching of the releasing system, and a judging system, which judges as to whether the ink in the ink conveyer tube is capable of being withdrawn in the ink cartridge. The release controller switches the releasing system in the open state to be in the closed state when the judging system judges that the ink is incapable of being withdrawn in the ink cartridge. 
     
    
     
       BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS 
         [0010]      FIG. 1  is a plane view of an inkjet printer  1  according to an embodiment of the present invention. 
           [0011]      FIG. 2  is a front view of the inkjet printer  1  according to the embodiment of the present invention. 
           [0012]      FIG. 3  is an enlarged partial view of the inkjet printer  1  according to the embodiment of the present invention. 
           [0013]      FIG. 4  is a front view of a first recording head  21  and a release valve  44  in the inkjet printer  1  according to the embodiment of the present invention. 
           [0014]      FIGS. 5A and 5B  illustrate an ink collecting operation of the release valve  44  in the inkjet printer  1  according to the embodiment of the present invention. 
           [0015]      FIG. 6  is a block diagram to illustrate an electric configuration of the inkjet printer  1  according to the embodiment of the present invention. 
           [0016]      FIGS. 7A and 7B  are diagrams to illustrate an operation indicator panel  28  in the inkjet printer  1  according to the embodiment of the present invention. 
           [0017]      FIG. 8  is a flowchart to illustrate a main flow of the operation of the inkjet printer  1  according to the embodiment of the present invention. 
           [0018]      FIG. 9  is a flowchart to illustrate an ink withdrawal operation to be executed in the inkjet printer  1  according to the embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Hereinafter, an embodiment according to an aspect of the present invention will be described with reference to the accompanying drawings. Firstly, an inkjet printer  1  according to the present embodiment will be described with reference to  FIGS. 1  though  7 . The inkjet printer  1  is an inkjet printer for printing an image on a piece of fabric in an inkjet method. 
         [0020]    The inkjet printer  1  in the present embodiment is a known inkjet printer having first recording heads  21  and second recording heads  22  to form an image on a recording medium in inks ejected from nozzle surfaces of the first and the second recording heads  21 ,  22  according to image data. In the inkjet printer  1 , a piece of fabric can be used as a recording medium, and the piece of fabric may be, for example, a T-shirt. As shown in  FIGS. 1 and 2 , the inkjet printer  1  is provided with a flat base plate  2  at a bottom and a chassis  10  to cover the entire body of the inkjet printer  1 . 
         [0021]    The first recording heads  21  are mounted on a carriage  13 , which is reciprocated in a right-and-left direction in  FIG. 1  along a guide rail  11 . In the vicinity of a right-hand end of the guide rail  11 , a first carriage motor  24  ( FIG. 6 ) to carry the first inkjet heads  21  is provided. Further, a pulley (not shown) is provided in the vicinity of a left-hand end of the guide rail  11 , and a carriage belt (not shown) is drawn between the first carriage motor  24  and the pulley. The carriage belt is fixed to a rear side of the carriage  13 . The carriage  13  is slidably connected to the guide rail  11  and reciprocated along the guide rail  11  in the right-and-left direction (i.e., the main scanning direction) when the first carriage motor  24  is activated. At one of the right-hand end and the left-hand end of the reciprocative range of the carriage  13 , a maintenance mechanism (not shown) such as a capping unit, a wipe unit, and a purge unit for the first recording heads  21  is provided. 
         [0022]    A first ink cartridge container  31   a  is provided on the right-hand end of the chassis  10 . The first ink cartridge container  31   a  has housing portions to house four first ink cartridges  31 , which contain opaque white ink therein. 
         [0023]    As shown in  FIG. 3 , each of the housing portions formed in the first ink cartridge container  31   a  is provided with a cartridge detective sensor  61 . In this embodiment, optical sensors are used as the cartridge detective sensors  61 . 
         [0024]    On the upper surface of the housing portions, supporting members  70 , which have squared U-shaped forms, in a lateral view, are provided. The supporting member  70  supports a rod-like ink amount detecting member  71  to be swingable about the supporting member  70  itself. The ink amount detecting member  71  is placed above the first ink cartridge  31  and provided with a detecting portion  72 , which is made of resin and substantially triangular-shaped, at the right end. 
         [0025]    The first ink cartridge container  31   a  is provided with an in-cartridge ink amount detective sensor  62  for each of the housing portion. The in-cartridge ink amount detective sensor  62  is located below the left end of the ink amount detecting member  71 . In this embodiment, optical sensors are used as the in-cartridge ink amount detective sensors  62 . 
         [0026]    The triangular portion of the detecting portion  72  is configured to face downward and intrude in the first ink cartridge  31  through a hole formed substantially in a center of an upper wall of the first ink cartridge  31 , and contact an ink pack  3  lb settled in the first ink cartridge  31 . Due to a weight balance, the ink amount detecting member  71  is held by the supporting member  70  to be inclined to have the detecting portion  72  at the right-hand end in a lower position and the left-hand end in a higher position (see  FIG. 3 ) in normal state. The inclination of the ink amount detecting member  71  changes according to the amount of the ink contained in the ink pack  31   b.    
         [0027]    The first ink cartridges  31  are connected to each of the first recording heads  21  by first ink conveyer tubes  34 . In a printing operation, the white ink stored in the first ink cartridges  31  are conveyed to each channel of the first recording heads  21  via the first ink conveyer tubes  34 . 
         [0028]    The first ink conveyer tubes  34  are transparent and flexible tubes. The first ink conveyer tubes  34  to supply the ink to the first recording heads  21  are moved along with the first recording heads  21  when the carriage  13  with the first recording heads  21  is reciprocated in the main scanning direction between the right side end and the left side end of the guide rail  11 . Therefore, the first ink conveyer tubes  34  are formed to be longer than a length of the guide rail  11 . The inkjet printer  1  is equipped with a first arm  36  so that, when the carriage  13  is moved, the first ink conveyer tubes  34  can smoothly move to follow the carriage  13 . 
         [0029]    The first arm  36  includes a rear portion, which is a thin and elongated plate rotatable about a supporting point  36   a,  and a supporting point  36   b  is provided at an end of the rear portion. The first arm  36  further includes a front portion, which is a thin and elongated plate rotatable about the supporting point  36   b  and is coupled to the carriage  13  at a supporting point  36   c.    
         [0030]    The inkjet printer  1  according to the embodiment is equipped with a guide rail  12 , which is arranged in parallel with the guide rail  11 , to guide a carriage  14  with a second recording head  22  being mounted. As shown in  FIG. 2 , the guide rail  12  is arranged in a position higher than the guide rail  11 . 
         [0031]    In the vicinity of a left-hand end of the guide rail  12 , a second carriage motor  25  ( FIG. 6 ) is provided, and in the vicinity of the right-hand end of the guide rail  12 , a pulley (not shown) is provided. Further, a carriage belt (not shown) is drawn between the second carriage motor  25  and the pulley. The carriage belt is fixed to the carriage  14  so that the carriage  14  is reciprocated along the guide rail  12  in the left-and-right direction (i.e., the main scanning direction) when the second carriage motor  25  is activated. At one of the right-hand end and the left-hand end of the reciprocative range of the carriage  14 , a maintenance mechanism (not shown) such as a capping unit, a wipe unit, and a purge unit for the second recording heads  22  is provided. 
         [0032]    A second ink cartridge container  32   a  is provided on the left-hand end of the chassis  10 . The second ink cartridge container  32   a  has housing portions to house each of four second ink cartridges  32 , which contains CMYK (cyan, magenta, yellow, and black) colored inks respectively therein. The second ink cartridges  32  are connected to each of the second recording heads  22  by second ink conveyer tubes  35  so that the CMYK colored inks stored in the second ink cartridges  32  are conveyed to each channel of the second recording heads  22 . 
         [0033]    The second ink conveyer tubes  35  are flexible tubes. The CMYK colored inks are supplied to the second recording heads  22  during a printing operation. The second ink conveyer tubes  35  to supply the ink to the second recording heads  22  are moved along with second recording heads  22  when the carriage  14  with the second recording heads  22  is reciprocated in the main scanning direction between the right side end and the left side end of the guide rail  12 . Therefore, the second ink conveyer tubes  35  are formed to be longer than a length of the guide rail  12 . The inkjet printer  1  is equipped with a second arm  37  so that, when the carriage  14  is moved, the second ink conveyer tubes  35  can smoothly move to follow the carriage  14 . 
         [0034]    The second arm  37  includes a rear portion, which is a thin and elongated plate, rotatable about a supporting point  37   a,  and a supporting point  37   b  is provided at an end of the rear portion. The second arm  37  further includes a front portion, which is a thin and elongated plate, rotatable about the supporting point  37   b  and is coupled to the carriage  14  at a supporting point  37   c.    
         [0035]    It is to be noted that, in the present embodiment, the main scanning direction of the first recording heads  21  and the second recording heads  22  (i.e., left-and right direction in  FIG. 1 ) indicates the right-and-left direction of the inkjet printer  1 . 
         [0036]    The flat base plate  2  of the inkjet printer  1  is provided with a platen feed unit  7  to move a platen  5  in the front-and-rear direction. The upper side and the lower side of the inkjet printer  1  as shown in  FIG. 1  correspond to the frontward and rearward of the inkjet printer  1 , respectively. The platen feed unit  7  includes a guide rail (not shown) and a platen feed motor  40  ( FIG. 6 ) being a stepping motor arranged at a rear end portion (i.e., upper end in  FIG. 1 ) of the guide rail. When the platen feed motor  40  is activated, the platen  5  is reciprocated along the guide rail in the up-and-down direction in  FIG. 1 . 
         [0037]    The platen  5  is a substantially rectangular-shaped flat plate with a shorter side facing an operator excurved. The recording medium (e.g., a T-shirt) is placed in a printable posture in the inkjet printer  1 . The inkjet printer  1  may have a plurality of sizes of platen  5 , which can be selected according to, for example, sizes and shapes of the recording media. 
         [0038]    As shown in  FIG. 1 , at right-hand front of the inkjet printer  1  is provided an operation panel  28 , through which the operator inputs an instruction for the inkjet printer  1 . The operation panel  28  includes print buttons  29  and a display  30  being a LCD (liquid crystal display). 
         [0039]    Next, a fluid releasing mechanism according to the present embodiment will be described with reference to  FIG. 4 . The inkjet printer  1  in the present embodiment is equipped with an air release valve  44 , which releases and shuts down air flow in the first ink conveyer tubes  34 . As has been mentioned above, the first ink conveyer tubes  34  connect the first ink cartridges  31  and the channels of the first recording heads  21 . The air release valve  44  is an electromagnetic valve, which is switched from an open position and a closed position, and vice versa, to release and shut down the air flow in between the first recording heads  21  and the first ink cartridges  31  in the first ink conveyer tubes  34 , according to electric signals. When the air release valve  44  is opened to release the air flow in the first ink conveyer tubes  34  with the first recording heads  21  being covered with caps  45  (see  FIG. 5 ), the ink remaining in the first ink conveyer tubes  34  is withdrawn in the first ink cartridges  31 . 
         [0040]    As shown in  FIG. 5A , when the caps  45  cover the nozzle surfaces of the first recording heads  21 , and the air release valve  44  is switched to shut down the air flow in the first ink conveyer tubes  34 , a hydraulic head difference between a level of the nozzle surfaces of the first recording heads  21  and an ink supplying level (i.e., vertical positions of the first ink cartridges  31 ) is substantially small so that the ink remaining in the first ink conveyer tubes  34  is not withdrawn in the first ink cartridges  31 . 
         [0041]    However, as shown in  FIG. 5B , when the caps  45  cover the nozzle surfaces of the first recording heads  21 , and the air release valve  44  is switched to release the air flow in the first ink conveyer tubes  34 , the hydraulic head difference between a level of the air release valve  44  and the ink supplying level of the first ink cartridges  31  is substantially large so that the ink remaining in the first ink conveyer tubes  34  is withdrawn in the first ink cartridges  31 . The ink reloading process will be described later in detail with reference to  FIG. 9 . 
         [0042]    It is to be noted in the present embodiment that the first ink cartridges  31  are provided with filters  51   b,  and the first recording heads  21  are provided with filters  51   a  at positions indicated by dotted lines in  FIGS. 5A and 5B . These filters  51   a,    51   b  serve to catch obstacles flowing in the ink when the ink is collected. 
         [0043]    As shown in  FIG. 4 , the air release valve  44  is provided with in-tube ink detective sensors  63  to detect presence of ink in the first ink conveyer tubes  34 . In the present embodiment, the in-tube ink detective sensors  63  are optical sensors. 
         [0044]    The in-tube ink detective sensor  63  includes a photo-emitting element  63   a  and a photo-sensitive element  63   b  with the first ink conveyer tube  34  intervening therebetween. The photo-emitting element  63   a  and the photo-sensitive element  63   b  being a pair is provided to each of the first ink conveyer tubes  34 , although solely the rightmost pair is shown in  FIG. 4 , and the other three pairs are omitted for simplicity of explanation. 
         [0045]    Next, referring to  FIG. 6 , an electrical configuration of the inkjet printer  1  will be described. As shown in  FIG. 6 , the inkjet printer  1  is provided with a control unit  100 , and the control unit  100  includes a CPU  110  that controls the entire operation in the inkjet printer  1 . The CPU  110  is connected with a ROM  120 , a RAM  130  through a bus  115 . The ROM  120  stores various controlling programs to be executed in the CPU  110 . The RAM  130  temporarily stores data concerning the operations in the inkjet printer  1 . 
         [0046]    The CPU  110  is further connected with a communication unit  150  and with a PC (personal computer)  170  through a communication cable  160 . Furthermore, the CPU  110  is connected with a print control unit  140  to control printing operations in the inkjet printer  1  through the bus  115 . 
         [0047]    The print control unit  140  includes a head controller  141 , a head drive controller  142 , a platen feed motor controller  143 , an air release controller  144 , a key input unit  145 , the display control unit  146 , and a sensor input unit  147 . 
         [0048]    The head controller  141  drives piezoelectric actuators for each of the channels in the first recording heads  21  and the second recording heads  22 . The head drive controller  142  activates the first carriage motor  24  and the second carriage motor  25 , and the platen feed motor controller  143  activates the platen feed motor  40 . Further, the air release controller  144  controls switching of the air release valve  44 . 
         [0049]    The key input unit  145  receives signals entered through a print start key  29   a,  a cancel key  29   b,  a maintenance key  29   c,  a cursor (up) key  29   d,  a cursor (down) key  29   e,  and an OK key  29   f.  The keys  29   a - 29   f  are provided in the operation panel  28  (see  FIG. 7A ). The operation panel  28  further includes a data reception indicator  30   a,  an error indicator  30   b,  and a display  30 , which are controlled by the display control unit  146 . 
         [0050]    When the maintenance key  29   c  is pressed by the operator, the display  30  shows a menu screen (see  FIG. 7A ), on which menu options “Head Cleaning,” “Test Print,” and “Ink Unloading” are displayed. When the menu options are displayed, a background of an option being currently selected (i.e., “Head Cleaning” in  FIG. 7A ) is inverted. An option to be selected can be specified by up and down motions of a cursor, which can be shifted by the cursor (up) key  29   d  and the cursor (down) key  29   e.  Thus, when the cursor (down) key  29   e  is pressed twice from the position shown in  FIG. 7A , the display  30  shows the option “Ink Unloading” inverted as shown in  FIG. 7B . At this time, if the option “Ink Unloading” is selected with the OK key  29   f,  the ink withdrawal operation is started. 
         [0051]    The sensor input unit  147  receives signals provided from the cartridge detective sensors  61 , the in-cartridge ink amount detective sensors  62 , and the in-tube ink detective sensors  63 . 
         [0052]    The cartridge detective sensor  61  includes a photo-emitter and a photo-receiver. When the first ink cartridge  31  is set in the first ink cartridge container  31   a,  a light blocker  31   c  provided to the first ink cartridge  31  is interposed between the photo-emitter and the photo-receiver to block the light from the photo-emitter. Thus, presence of the first ink cartridge  31  in the housing portion of the first ink cartridge container  31   a  is detected. 
         [0053]    The in-cartridge ink amount detective sensor  62  has a photo-emitter (not shown) and a photo-receiver (not shown). When the ink is withdrawn into the ink pack  31   b  and a volume of the ink in the ink pack  31   b  increases, the ink pack  31   b  is inflated to lift up the detecting portion  72  at the right-hand end of the ink amount detecting member  71 . Accordingly, the ink amount detecting member  71  swings about the supporting member  70 , and the left-hand end of the ink amount detecting member  71  is lowered. Further, when the ink pack  31   b  is filled with the withdrawn ink, the left-hand end of the ink amount detecting member  71  is further lowered and interposed between the photo-emitter and the photo-receiver of the in-cartridge ink amount detective sensor  62  to block the light emitted from the photo-emitter. Accordingly, the ink being full in the ink pack  31   b  is detected. 
         [0054]    The in-tube ink detective sensor  63 , as mentioned above, includes the photo-emitting element  63   a  and the photo-sensitive element  63   b.  When substantially no ink remains in the first ink conveyer tube  34 , the light from the photo-emitting element  63   a  transmits through the transparent first ink conveyer tube  34  and can be received by the photo-sensitive element  63   b  without being blocked by the opaque white ink. On the other hand, when the ink remains in the first ink conveyer tube  34 , the light from the photo-emitting element  63   a  is blocked by the opaque white ink and cannot be received by the photo-sensitive element  63   b.  Therefore, in the present embodiment, presence of the ink remaining in the first ink conveyer tube  34  can be detected on bases of the signals provided by the photo-sensitive element  63   b.    
         [0055]    Next, a main flow of the operation of the inkjet printer  1  according to the embodiment of the present invention will be described with reference to  FIG. 8 . When the inkjet printer  1  is powered on by the operator and the operation starts in S 1 , the inkjet printer  1  is initialized. The initialization includes, for example, a flushing operation to prepare the nozzles of the first and the second recording heads  21 ,  22  in condition for ejecting ink drops. In S 2 , determination is made as to whether the initialization successfully completed. When the initialization fails (S 2 : NO), in S 9 , the error indicator  30   b  is activated. When the error indicator  30   b  is activated, for example, an indicator lamp is lit and/or an error indicating sound is generated. 
         [0056]    Following S 9 , in S 10 , it is examined as to whether one of operation menus, which exclude “print,” “ink withdrawal,” and “head cleaning,” is selected. When one of the operation menus is selected (S 10  YES), in S 11 , an operation corresponding to the selection is performed. Thereafter, the inkjet printer  1  waits for next input to select an operation menu. 
         [0057]    In S 10 , if power to the inkjet printer  1  is shut off (S 10 : NO, S 12 : YES), the operation is terminated. If the power supply to the inkjet printer  1  is maintained (S 12 : NO), the process repeats S 10 . 
         [0058]    In S 2 , when the initialization successfully completes (S 2 : YES), the inkjet printer  1  waits for selection of an operation menu to be entered. In S 3 , it is examined as to whether the print start key  29   a  has been operated. If the print start key  29   a  has been operated (S 3 : YES), in S 4 , it is examined as to whether the inkjet printer  1  is provided with print data. If no print data has been provided (S 4 : NO), in S 6 , an error is indicated, and the process returns to S 3 . If the inkjet printer  1  is provided with print data (S 4 : YES), in S 5 , a printing operation to print an image according to the print data is performed. The process returns to S 3  thereafter. 
         [0059]    In S 3 , if the print start key  29   a  has not been operated (S 3 : NO), in S 7 , it is examined as to whether an ink withdrawal operation is selected through a menu window displayed in the operation panel  28 . If selection for the ink withdrawal operation is made (S 7 : YES), in S 8 , the ink remaining in the first ink conveyer tubes  34  is withdrawn in the first ink cartridges  31 . The process returns to S 3  thereafter. The ink withdrawal operation will be described later in detail. 
         [0060]    Next, the ink withdrawal operation will be described with reference to  FIG. 9 . If the OK key  29   f  is pressed with the option “Ink Unloading” being selected, as shown in  FIG. 7B , the ink withdrawal operation is started. 
         [0061]    When the ink withdrawal operation starts, in S 20 , a message to indicate that the ink withdrawal is started is presented in the display  30 . Next, in S 21 , it is examined, based on the input from the cartridge detective sensor  61 , as to whether the first ink cartridges  31  are set to the housing portions of the first ink cartridge container  31   a . If the first ink cartridges  31  are not set in the first ink cartridge container  31   a  (S 21 : NO), the error lamp  30   b  is lit, and in S 30 , an error message (e.g., “ink cartridges are not set”) is displayed on the display  30 . Thereafter, the operation is terminated. 
         [0062]    In S 21 , when the first ink cartridges  31  are set in the first ink cartridge container  31   a  (S 21 : YES), in S 22 , the air release valve  44  is switched to release the air flow in the ink conveyer tubes  34 . 
         [0063]    If the air release valve  44  is switched to release the air flow, in S 23 , a message (e.g., “Unloading . . . ”) to indicate that the ink is being withdrawn is presented in the display  30 . The ink remaining in the first ink conveyer tubes  34  can be withdrawn and collected in the first ink cartridges  31  by utilizing the hydraulic head difference. Thereafter, in S 24 , it is examined again as to whether the first ink cartridges  31  are set in the housing portions of the first ink cartridge container  31   a.    
         [0064]    When the first ink cartridges  31  are not set in the predetermined positions of the housing portions (S 24 : NO), in S 31 , the air release valve  44  is switched to shut down the air flow in the first ink conveyer tubes  34 . After switching the air release valve  44  to shut down the air flow, the error lamp  30   b  is lit, and in S 32 , an error message (e.g., “ink cartridge is not set”) is displayed in the display  30 . Thereafter, the ink withdrawal operation is terminated. According to the above configuration, even when the first ink cartridges  31  are removed from the first ink cartridge container  31  a during the ink withdrawal, the ink being withdrawn is prevented from leaking out of the first ink conveyer tubes and around the inkjet printer  1 . 
         [0065]    When the first ink cartridge  31  is set in the first ink cartridge container  31   a  (S 24 : YES), in S 25 , it is examined, based on the input from the in-cartridge ink amount detective sensor  62 , as to whether the amount of the ink in the first ink cartridges  31  reaches a predetermined level. In the present embodiment, the predetermined level refers to the full amount in the first ink cartridges  31 . 
         [0066]    Therefore, in S 25 , if the first ink cartridges  31  are filled with the ink (S 25 : YES), in S 33 , the air release valve  44  is switched to shut down the air flow in the first ink conveyer tubes  34 . After switching the air release valve  44  to shut down the air flow, in S 34 , a message (e.g., “ink cartridge is full”) is displayed on the display  30 . Thereafter, the ink withdrawal operation is terminated. According to the above configuration, even when the first ink cartridges  31  are filled with the ink to the full amount during the ink withdrawal, the ink being withdrawn is prevented from being overflowed from the first ink cartridge  31 . 
         [0067]    In S 25 , when the amount of the ink in the first ink cartridges  31  has not reached the predetermined level (S 25 : NO), in S 26 , it is examined, based on the input from the in-tube ink detective sensor  63 , as to whether the ink remains in the first ink conveyer tubes  34 . 
         [0068]    In S 26 , if the ink does not remain in the first ink conveyer tubes  34  (S 26 : NO), in S 35 , the air release valve  44  is switched to shut down the air flow in the first ink conveyer tubes  34 . After switching the air release valve  44  to shut down the air flow, in S 36 , a message (e.g., “no ink in the tubes”) is displayed in the display  30 . Thereafter, the operation is terminated. Accordingly, when the remaining ink is cleared from the first ink conveyer tubes  34 , the air release valve  44  is switched promptly to shut down the air flow in the first ink conveyer tubes  34 , and the ink withdrawal operation is aborted; thus, operation efficiency of the inkjet printer  1  can be improved. 
         [0069]    In S 26 , when the ink remains in the first ink conveyer tubes  34  (S 26 : YES), in S 27 , it is examined as to whether a predetermined time period, which is substantially long to withdraw the remaining ink from the first ink conveyer tubes  34 , has elapsed. In this step, when the air release valve  44  is switched to release the air flow in the first ink conveyer tubes  34  in S 22 , the CPU  110  activates an inner timer. In S 27 , the CPU  110  compares the elapsed time of the inner timer activated in S 22  with a predetermined period. 
         [0070]    If the predetermined period has not elapsed (S 27 : NO), the process returns to S 24 . When the predetermined period elapses (S 27 : YES), in S 28 , the air release valve  44  is switched to shut down the air flow in the first ink conveyer tubes  34 . Thus, because the air release valve  44  is switched to shut down the air flow in the first ink conveyer tubes  34  after the predetermined period, the inner surface of the ink conveyer tubes  34  is prevented from being exposed to open air so that even the minimum amount of ink remaining in the ink conveyer tubes  34  should not be dried out. 
         [0071]    In S 29 , a message (e.g., “Ink withdrawn”) to indicate completion of the ink withdrawal is presented in the display  30 . The operation is terminated thereafter. 
         [0072]    According to the above operation, the ink remaining in the first the ink conveyer tubes  34  can be withdrawn and collected to be stored in the first ink cartridges  31  by utilizing the hydraulic head difference. Once the ink is collected, the ink can be stirred when the first ink cartridges  31  are removed from the inkjet printer  1  and shaken manually. When the first ink cartridges  31  containing the stirred ink are set again in the inkjet printer  1 , the well-conditioned white ink can be ejected smoothly from the nozzles. Thus, the remaining ink, which may have been wasted in the conventional purging operation, can be prevented from being wasted. According to the above configuration, removal of the first ink conveyer tubes  34  in order to collect the remaining ink is not required, or branch structures to collect the remaining ink are not specifically required in the first ink conveyer tubes  34 . 
         [0073]    According to the above embodiment, the first ink conveyer tubes  34  can be switched between an open state and a closed state by the air release valve  44  provided in the first ink conveyer tubes  34 . Therefore, by releasing the air flow in the first ink conveyer tubes  34  and utilizing the hydraulic head difference, the ink remaining in the first ink conveyer tubes  34  can be withdrawn therefrom to the first ink cartridges  31 . Further, with the air release valve  44  in the open state, it is judged as to whether the ink can be withdrawn and collected in the first ink cartridges  31  in S 24 -S 26 . If it is judged that the ink should not be withdrawn, the ink withdrawal operation is terminated by shutting down the air flow in the first ink conveyer tubes  34 . 
         [0074]    According to the above embodiment, when the first ink cartridges  31  are not installed in the ink cartridge container  31   a , the ink withdrawal operation to withdraw the ink to the first ink cartridges  31  is terminated; therefore, leakage of the reversed ink out of the disconnected first ink conveyer tubes  34  can be prevented. 
         [0075]    According to the above embodiment, when the amount of the ink in the first ink cartridges  34  reaches the predetermined level, the ink withdrawal operation is terminated; therefore, overflow of the reversed ink out of the first ink cartridges  31  can be prevented. 
         [0076]    According to the above embodiment, when the ink does not remain in the first ink conveyer tubes  34 , the ink withdrawal operation is terminated; therefore, it can be prevented that the air flow in the first ink conveyer tubes  34  is maintained released even after the ink withdrawal completes. Accordingly, operation efficiency of the inkjet printer  1  can be improved. 
         [0077]    According to the above embodiment, the optical sensors to detect the presence of the first ink cartridges  31  in the ink cartridge container  31   a  are provided inside the first ink cartridge container  31   a ; therefore, the optical sensors can be maintained without being exposed to the open air, and adherence of dust to the cartridge detective sensors  61  can be prevented. 
         [0078]    According to the above embodiment, the optical sensors to detect the full amount of the ink in the first ink cartridges  34  are provided inside the first ink cartridge container  31   a ; therefore, the optical sensors can be maintained without being exposed to the open air, and adherence of dust to the in-cartridge ink amount detective sensors  62  can be prevented. 
         [0079]    Although an example of carrying out the invention has been described, those skilled in the art will appreciate that there are numerous variations and permutations of the inkjet printing apparatus that fall within the spirit and scope of the invention as set forth in the appended claims. It is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or act described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims. 
         [0080]    For example, the in-cartridge ink amount detective sensor  62 , which examines as to whether the ink in the first ink cartridge  31  reaches the predetermined level, may not necessarily be an optical sensor, but may be a weight sensor (e.g., a load cell) or a combination of the optical sensor and the weight sensor. With the weight sensor, the CPU  110  examines the amount of the ink in the first ink cartridges  31  based on that weight of the first ink cartridges  31  reaches a predetermined weight. If the weight of the first ink cartridges  31  reaches the predetermined weight, the air release valve  44  is switched to shut down the air flow in the first ink conveyer tubes  34 . 
         [0081]    With such a weight sensor, similarly with the optical sensor, the inkjet printer  1  can prevent the ink withdrawn from the first ink conveyer tube  34  from being overflowed out of the first ink cartridges  31 . Further, with combination of the optical sensor and the weight sensor, the amount of ink in the first ink cartridge  31  can be even more reliably detected. 
         [0082]    For another example, the predetermined level of the ink in the first ink cartridges  31  refers to the full amount to fill the first ink cartridges  31 . However, the predetermined level may alternately be defined as a substantially operable amount. The in-cartridge ink amount detective sensor  62  is necessary to be located at an appropriate height corresponding to the definition of the predetermined level. 
         [0083]    In the above embodiment, the in-tube ink detective sensors  63  are attached to the air release valve  44 . However, it is even more preferable that the in-tube ink detective sensors  63  are fixed to portions in the vicinity of the first ink cartridges  31  by a fixing means. 
         [0084]    In addition to the air release valve  44  in the first ink conveyer tubes  34  for white ink, air release valves in a similar configuration may be provided to the second ink conveyer tubes  35  for the CMYK inks. 
         [0085]    Further, it is to be noted that the air releasing mechanism may be provided to other inks than the white ink, containing solid component which may be deposited in the ink, to prevent concentration gradient. 
         [0086]    Furthermore, the present invention can be similarly applied to an inkjet printer which is capable of printing an image on a sheet of paper and other recording medium, in place of a piece of fabric, in inks. Moreover, the present invention can be effectively applied to an ink applying apparatus, which ejects, for example, ultraviolet curable ink or other ultraviolet curable agent (e.g., foundation coat and overcoat) to surfaces of an object.