Patent Publication Number: US-9889672-B2

Title: Attachment, liquid container, and liquid supply apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of co-pending U.S. patent application Ser. No. 14/048,247 filed on Oct. 8, 2013, which is a divisional of co-pending U.S. patent application Ser. No. 13/187,925 filed on Jul. 21, 2011, which is a continuation U.S. patent application Ser. No. 12/426,780 filed on Apr. 20, 2009, now U.S. Pat. No. 8,007,084, which is a continuation of U.S. patent application Ser. No. 11/344,825, now U.S. Pat. No. 7,677,710 which was filed on Feb. 1, 2006 and is based upon and claims the benefit of priority from prior Japanese Patent Applications No. 2005-025985, filed on Feb. 2, 2005, No. 2005-025986, filed also on Feb. 2, 2005, and No. 2005-042589, filed on Feb. 18, 2005, the entire contents of each of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to attachments and liquid supply apparatuses that are preferably used in liquid ejection apparatuses. The present invention also relates to liquid containers and liquid supply apparatuses, and, more particularly, to liquid containers and liquid supply apparatuses that replace liquid cartridges in a liquid ejection apparatus, such as an inkjet recording apparatus, and allow supply of a liquid, such as ink, from an external source. 
     For example, an inkjet recording apparatus (a liquid ejection apparatus) typically includes an inkjet recording head (a liquid ejecting portion) and a paper feeder mechanism. The recording head is formed in a carriage and thus moved in a direction defined by the width of a sheet of recording paper. The paper feeder mechanism moves the paper sheet in a direction perpendicular to the movement direction of the recording head and relative to the recording head. The paper sheet is thus subjected to recording through ejection of ink droplets from the recording head in accordance with printing data. 
     If the inkjet recording apparatus is used on business, the apparatus must tolerate relatively large work load. It is thus necessary to employ a corresponding large-capacity cartridge. To meet such need, an off-carriage type recording apparatus including small-capacity sub tanks and main tanks serving as cartridges is known. The sub tanks are installed in the carriage in which the recording head is provided. The main tanks are arranged in a mounting portion (a cartridge holder), which is formed at, for example, a side of the body of the recording apparatus. Ink is supplied from each of the main tanks to the associated one of the sub tanks through an ink tube. The ink is then sent from the sub tanks to the recording head. 
     Further, to perform printing on a large-sized sheet of paper, it is now required to provide a large-sized recording apparatus that has an increased scanning distance of a carriage. The recording apparatus includes an increased quantity of nozzles formed in a recording head, thus improving the throughput of the apparatus. 
     To further improve the throughput of the apparatus, it is desirable that ink be fed from main tanks to sub tanks formed in a carriage when necessary while printing is being performed. The ink is thus stably supplied to the recording head through the sub tanks. 
     In this apparatus, each of the main tanks is connected to the corresponding one of the sub tanks through an ink supply tube provided specifically for each of the ink types employed by the apparatus. However, since the scanning distance of the carriage is relatively great in this apparatus, the length of each ink supply tube is increased and thus pressure variation occurs in the ink supply tube. Further, since the recording head includes the increased number of the nozzles, as has been described, the apparatus consumes an increased amount of ink. This raises the dynamical pressure of the ink in each ink supply tube, which connects the associated main tank to the sub tank. The amount of the ink supplied to the sub tank thus may become insufficient. 
     To solve this problem, for example, an inkjet recording apparatus having an ink supply valve unit, which includes a movable valve, has been proposed (see, for example, Japanese Laid-Open Patent Publication No. 2004-142405). The ink supply valve unit selectively opens and closes the valve in order to connect or disconnect an ink supply chamber with respect to a pressure chamber. The ink supply valve unit receives the ink that is to be supplied from a cartridge to a liquid ejection head, thus eliminating pressure variation in an ink supply tube. 
     Alternatively, for example, a structure in which air pressure is applied to a main tank has been proposed (see, for example, Japanese Laid-Open Patent Publications Nos. 2001-212974, 2001-287380, and 2003-311997). In this structure, an ink flow from the main tank to a sub tank is forcibly produced by the air pressure. A sufficient amount of ink free from pressure variation is thus supplied to the sub tank. 
       FIG. 24  is a view schematically showing a typical inkjet recording apparatus in which air pressure is applied to a main tank.  FIG. 25  shows the structure of a cartridge  18  serving as the main tank. 
     As shown in  FIG. 24 , a recording head  15 , a sub tank  103 , a pressurization pump  20 , and a cartridge holder  17  are formed in a printer  301 . The cartridge holder  17  accommodates a cartridge  18  filled with ink Ik. 
     As is shown in detail in  FIG. 25 , the cartridge  18  includes a casing  39 , which is a sealed casing formed of hard resin, and an ink pack  42  formed of flexible material. The ink pack  42  is received in the casing  39 . An air inlet port  46  and a liquid outlet port  44  are defined in an end of the casing  39 . Pressurized air is introduced from an external source to the ink pack  42  through the air inlet port  46 . The pressurized air thus pressurizes and sends the ink Ik from the ink pack  42  to the exterior through the liquid outlet port  44 . When the cartridge  18  is accommodated in the cartridge holder  17  of the printer  301 , the liquid outlet port  44  and the air inlet port  46  are connected to the sub tank  103  and the pressurization pump  20 , respectively. 
     Since the conventional cartridge  18  is supposed to be accommodated in the cartridge holder  17  of the printer  301 , the size of the cartridge  18  is restricted correspondingly. A large-sized cartridge is thus actually unusable. In other words, the cartridge holder that accommodates the cartridge is formed in a restricted space in the printer. The amount of the ink retained in the cartridge is thus typically small. Thus, the greater the work load of the printer becomes, the more often the cartridge must be replaced. This complicates operation of the printer and raises the running cost of the printer. Particularly, if the printer is a small-sized type or a thin type and the space for accommodating the cartridge holder is restricted, the amount of the ink retained in the cartridge becomes correspondingly small. In this case, the above-described problem is pronounced. 
     Therefore, if the capacity of the cartridge must be increased, an external tank may be employed as an option for supplying the ink the external tank to the printer. 
     However, there may be a case in which the external tank for feeding the ink Ik is not compatible with a pressurization supply system of the ink Ik through the pressurization pump  20  of the printer  301 . In this case, the printer  301  may cause an error in operation. 
     As described in Japanese Laid-Open Patent Publication No. 2003-326732, for example, an ink supply system using an attachment has been proposed. The attachment is mounted on a cartridge holder in the same manner as a cartridge, when the work load of the printer is relatively great. The ink is supplied from an external large-capacity ink tank to a recording head through the attachment. More specifically, a hollow sub tank is defined in the attachment, which is mounted on the cartridge holder. With the attachment mounted on the cartridge holder, the ink is introduced out of the external tank to the sub tank of the attachment to a predetermined level through actuation of a pump associated with the attachment. The ink is then sent from a liquid outlet port defined in a lower portion of the attachment to a liquid inlet port defined in the recording head. 
     However, when mounting the attachment of Japanese Laid-Open Patent Publication No. 2003-326732 on the cartridge holder, the pump must be activated to depressurize the sub tank of the attachment to a negative level. The ink is thus sent from the external tank to the sub tank until the ink level in the sub tank reaches the predetermined level. This prolongs the time needed for accomplishing the procedure for mounting the attachment. Further, it is necessary to install the pump, which sends the ink from the external tank to the sub tank, in association with the attachment. The cost for providing the attachment thus increases. That is, the attachment of Japanese Laid-Open Patent Publication No. 2003-326732 complicates the procedure for mounting the attachment on the cartridge holder as a replacement of the cartridge and increases the cost. In this regard, the attachment is not necessarily easy to employ. 
     SUMMARY 
     Accordingly, it is an objective of the present invention to provide low-cost and easy-to-use attachment and liquid supply apparatus that are easily and quickly mounted on a liquid ejection apparatus. 
     It is another objective of the present invention to provide a liquid container and a liquid supply apparatus that are compatible with a liquid pressurization supply system through an air pressurizing portion of a liquid ejection apparatus and stabilize supply of liquid. 
     To achieve the foregoing objectives, one aspect of the invention provides an attachment that is mountable on a liquid ejection apparatus. A liquid retainer is detachably mounted on a mounting portion of the liquid ejection apparatus. The mounting portion has a liquid inlet portion through which a liquid is introduced from the liquid retainer. The liquid is supplied from the exterior of the liquid ejection apparatus to the attachment through a liquid supply passage. The attachment includes an attachment body that is mountable on the mounting portion as a replacement of the liquid retainer, and a link portion that defines a link passage. The link portion is arranged in the attachment body in such a manner that, when the attachment body is mounted on the mounting portion, a downstream end of the link passage is positioned with respect to and connected to the liquid inlet portion. A downstream end of the liquid supply passage is connectable to an upstream end of the link passage of the link portion. 
     Another aspect of the present invention provides a liquid container that is mountable on a mounting portion of a liquid ejection apparatus. The liquid ejection apparatus has a liquid ejecting portion and an air pressurizing portion. The liquid container includes an air inlet port, a liquid outlet port, a liquid supply port, and a check valve. Through the air inlet port, a pressurized air is introduced from the exterior. The air inlet port is connected to the air pressurizing portion when the liquid container is mounted on the mounting portion. The liquid outlet port is connected to the liquid ejecting portion when the liquid container is mounted on the mounting portion. When an air is introduced into the liquid container through the air inlet port, a liquid is sent from the liquid container to the liquid ejecting portion through the liquid outlet port by a pressure generated by the air. Through the liquid supply port, the liquid is supplied to the liquid container. The check valve is provided in the liquid supply port. The check valve becomes open when an external pressure of the liquid supply port is greater than an internal pressure of the liquid supply port, and is closed when the internal pressure is greater than the external pressure. 
     A further aspect of the present invention provides a liquid supply apparatus that supplies a liquid to a liquid ejection apparatus. The liquid ejection apparatus has a liquid ejecting portion, an air pressurizing portion, and a mounting portion. A liquid cartridge is mountable on the mounting portion. The liquid cartridge has a first air inlet port and a first liquid outlet port. Liquid retained in the liquid cartridge is sent to the exterior from the first liquid outlet port by a pressure generated by a pressurized air when the pressurized air is introduced into the liquid cartridge through the first air inlet port. The liquid supply apparatus includes an attachment, an external tank, a tubular passage, and a pressure adjusting portion. The attachment is mountable on the mounting portion as a replacement of the liquid cartridge. The attachment has a second liquid outlet port and a second air inlet port. When the attachment is mounted on the mounting portion, the second liquid outlet port is connected to the liquid ejecting portion and the second air inlet port is connected to the air pressurizing portion. The external tank retains a liquid supply. The tubular passage connects the external tank to the second liquid outlet port. The liquid supply is supplied from the external tank to the second liquid outlet port through the tubular passage. The pressure adjusting portion adjusts a supply pressure of the liquid supply. The pressure adjusting portion also adjusts the supply pressure in correspondence with an air pressure introduced from the air pressurizing portion through the second air inlet port. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which: 
         FIG. 1  is a perspective view showing a printer according to a first embodiment of the present invention; 
         FIG. 2  is a perspective view showing a main portion of the printer of  FIG. 1 ; 
         FIG. 3  is a partially exploded perspective view showing a cartridge holder of  FIG. 1 ; 
         FIG. 4A  is a plan view showing a cartridge installed in the cartridge holder of  FIG. 1  in a state separated from a lid member; 
         FIG. 4B  is a front view showing the cartridge of  FIG. 4A ; 
         FIG. 5  is an exploded perspective view showing an attachment of  FIG. 1 ; 
         FIG. 6  is a side view showing a liquid supply apparatus arranged with respect to the printer of  FIG. 1 ; 
         FIG. 7A  is a plan view showing an attachment according to a second embodiment of the present invention in a state separated from a lid member; 
         FIG. 7B  is a front view showing the attachment of  FIG. 7A ; 
         FIG. 8  is a perspective view showing a printer in which an attachment according to a third embodiment of the present invention is installed; 
         FIG. 9  is a perspective view showing an attachment according to a fourth embodiment of the present invention; 
         FIG. 10  is an exploded perspective view showing the attachment of  FIG. 9 ; 
         FIG. 11  is a plan view showing a connection portion of a cartridge holder on which the attachment of  FIG. 9  is mounted; 
         FIG. 12  is a plan view showing the attachment of  FIG. 9  mounted on the mounting portion of  FIG. 11 ; 
         FIG. 13  is a side view showing arrangement of a liquid supply apparatus of a modified embodiment; 
         FIG. 14  is a side view showing arrangement of a liquid supply apparatus of another modified embodiment; 
         FIG. 15  is a side view showing arrangement of a liquid supply apparatus of another modified embodiment; 
         FIG. 16  is a block diagram schematically representing an inkjet recording apparatus in which a liquid container according to a fifth embodiment of the present invention is installed as a replacement of a liquid cartridge; 
         FIG. 17  is a longitudinal cross-sectional view showing the liquid container of  FIG. 16 ; 
         FIG. 18  is a longitudinal cross-sectional view showing a modified embodiment of the liquid container of  FIG. 16 ; 
         FIG. 19  is a block diagram schematically representing a liquid supply apparatus according to a sixth embodiment of the present invention; 
         FIG. 20  is a perspective view showing the appearance of the liquid supply apparatus of  FIG. 19 ; 
         FIG. 21  is a longitudinal cross-sectional view showing an attachment of  FIG. 20 ; 
         FIG. 22  is a schematic view showing an example of a pressure adjusting portion of  FIG. 19 ; 
         FIG. 23  is a schematic view showing a modified embodiment of the pressure adjusting portion; 
         FIG. 24  is a block diagram schematically representing a typical inkjet recording apparatus; and 
         FIG. 25  is a longitudinal cross-sectional view showing a cartridge of  FIG. 24 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A first embodiment of the present invention will now be described with reference to  FIGS. 1 to 6 . 
     As shown in  FIGS. 1 and 2 , an inkjet printer (hereinafter, a “printer”)  10 , or a liquid ejection apparatus of the first embodiment, includes a substantially box-like body casing  11 . A pair of opposing frame members  12   a ,  12   b  are provided at opposing lateral sides of the body casing  11 . A rod-like guide shaft  13  extends between the frame members  12   a ,  12   b . A carriage  14  is movably passed through the guide shaft  13 . The carriage  14  is thus reciprocated in a direction (a main scanning direction X of  FIG. 2 ) along the longitudinal direction of the guide shaft  13  while driven by the drive force generated by a non-illustrated carriage motor provided in the printer  10 . 
     A recording head  15  is formed on a bottom surface of the carriage  14  as a liquid ejection head. A plurality of nozzles (not shown) are defined in the recording head  15  for ejecting ink as liquid. Valve units  16  are arranged on an upper surface of the carriage  14  and supply the ink under an adjusted pressure to the recording head  15 . In the first embodiment, three valve units  16  are provided in the carriage  14 . Each of the valve units  16  adjusts the pressures of two color inks and supplies the ink to the recording head  15 . In other words, six color inks (black, yellow, magenta, cyan, light cyan, light magenta, and light cyan inks) are fed to the recording head  15 . 
     A platen (not shown), or a paper feeding portion, extends parallel with the guide shaft  13  below the zone in which the carriage  14  moves between the frame members  12   a ,  12   b  of the body casing  11 . The platen sends a recording paper PA as a target in a sub scanning direction Y (see  FIG. 2 ) perpendicular to the main scanning direction X. By ejecting ink droplets onto the recording paper PA, which is moved in the sub scanning direction Y, through the ejection nozzles of the recording head  15 , the printer  10  of the first embodiment performs printing. 
     A cartridge holder  17 , or a mounting portion, is provided in a fixed manner (fixed in an immovable manner) above the zone in which the carriage  14  moves between the frame members  12   a ,  12   b  of the body casing  11 . The cartridge holder  17  holds cartridges as liquid retainers (hereinafter, “cartridges”)  18  of  FIGS. 4A, 4B  or attachments  19  of  FIG. 5 . The cartridges  18  and the attachments  19  are mutually replaceable. In  FIG. 1 , six attachments  19  are mounted on the cartridge holder  17  of the printer  10 . 
     As shown in  FIG. 1 , a pressurization pump  20  is arranged in a rear portion of the body casing  11 . A belt-like tube ribbon  21  formed of flexible material extends in the body casing  11  and passes through the vicinity of the pressurization pump  20 . The tube ribbon  21  connects the valve units  16  to the cartridge holder  17  (see  FIG. 2 ). The tube ribbon  21  includes six ink passages, or liquid passages, and a single air passage, or a gas passage. Each of the ink passages supplies the ink from the corresponding cartridge  18  (or the attachment  19 ) mounted on the cartridge holder  17  to the associated valve unit  16 . The air passage sends pressurized air from the pressurization pump  20  to the cartridges  18  (or the attachments  19 ), which are held by the cartridge holder  17 . 
     As shown in  FIG. 3 , the cartridge holder  17  has a box-like holder casing  17   a  that encompasses the outer circumference of the cartridge holder  17 . A plurality of (six, in the first embodiment) sockets  22  are defined in the interior of the holder casing  17   a  for receiving the cartridges  18  (or the attachments  19 ). In  FIG. 3 , two of the sockets  22  are illustrated (while the socket  22   a  located on the near side is empty, the socket  22   b  located on the far side is occupied by the cartridge  18  (or the attachment  19 )). When mounting the cartridge  18  (the attachment  19 ) on the cartridge holder  17 , the cartridge  18  (the attachment  19 ) is inserted into the corresponding socket  22  in an insert direction indicated by arrow L of  FIG. 3 . When detaching the cartridge  18  (the attachment  19 ) from the cartridge holder  17 , the cartridge  18  (the attachment  19 ) is retracted from the socket  22  in a retract direction indicated by arrow R of  FIG. 3 . 
     A substantially parallelepiped slider  23  is arranged in each of the sockets  22 . The lateral width of the slider  23  coincides with a substantially entire lateral width of the socket  22 . A pair of positioning projections  24   a ,  24   b  project from positions close to opposing lateral ends of a front surface (a surface located foremost in direction R of  FIG. 3 ) of each slider  23 . A through hole  25  having a rectangular cross-sectional shape is defined between the positioning projections  24   a ,  24   b  and extends in the front-rear direction of the slider  23 . An air outlet port  26  having a circular cross-sectional shape is defined between the through hole  25  and the positioning projection  24   a  (as viewed to the left in  FIG. 3 ) and extends in the front-rear direction of the slider  23 . A terminal portion  27  having a plurality of contacts (not shown) extends forward from the opposing end of the front surface of the slider  23  (as viewed to the right in  FIG. 3 ). 
     A pair of rails  28   a ,  28   b  extend rearward from positions close to the opposing lateral ends of a rear surface (a surface located foremost in direction L of  FIG. 3 ) of each slider  23 . Support guides  29   a ,  29   b  are fixed to a bottom surface of each socket  22 . The rails  28   a ,  28   b  are allowed to slide along the support guides  29   a ,  29   b  in the front-rear direction of the slider  23 . A rod-like shaft  30  projects rearward from the rear surface of each slider  23  at a position between the through hole  25  and the rail  28   b  (as viewed to the right in  FIG. 3 ). 
     A coil spring  31  is loosely wound around the shaft  30  of each slider  23 . An end (a rear end) of the coil spring  31  is engaged with an engagement projection  32  fixed to the bottom surface of the socket  22 . An opposing end (a front end) of the coil spring  31  contacts the rear surface of the slider  23 . Thus, the slider  23  is urged normally in the retract direction (indicated by arrow R of  FIG. 3 ) by the force generated by the coil spring  31 . In this state, the rails  28   a ,  28   b  are allowed to slide along the support guides  29   a ,  29   b , thus reciprocating in the front-rear direction. 
     As shown in  FIG. 3 , a support table  33  is arranged in a substantial lateral middle of each socket  22 . Each of the support tables  33  is located rearward from the zone in which the associated slider  23  is allowed to reciprocate. An ink supply needle  34 , or a liquid inlet portion of the printer  10 , projects forward from a front surface of the support table  33 . Each of the ink supply needles  34  is formed by a pipe through which a liquid passage (not shown) extends. An inlet port  34   a  is defined in a front end portion of the outer circumferential surface of each ink supply needle  34  for introducing the ink into the interior of the ink supply needle  34 . As in the upper socket  22   b  in  FIG. 3 , when the slider  23  is moved rearward against the force of the coil spring  31 , the ink supply needle  34  is passed through the through hole  25  of the slider  23  thoroughly from a rear end of the through hole  25  to a front end. In this state, the front end portion of the ink supply needle  34  in which the inlet port  34   a  is defined is projected forward from the front surface of the slider  23 . 
     A connection pipe  35  extends rearward from a rear surface of each support table  33 . Each of the connection pipes  35  communicates with the interior of the associated ink supply needle  34  and thus defines a liquid passage. A rear end (a downstream end) of each connection pipe  35  is connected to a connection passage  36 , which extends along a substantially entire lateral width of the holder casing  17   a . The connection passage  36  is formed as an integral body of six ink passages (not shown), each of which defines a liquid passage of the corresponding socket  22 , and a single air passage (not shown), which defines a gas passage. Each of the ink passages is connected to the associated one of the ink passages defined in the tube ribbon  21 . 
     Flexible pressurized air supply tubes  37  extend from the air passage of the connection passage  36 . A distal end of each of the pressurized air supply tubes  37  is connected to the air outlet port  26  of the corresponding slider  23  from behind. In other words, after having been sent from the pressurization pump  20 , the pressurized air is introduced into each pressurized air supply tube  37  through the tube ribbon  21  and the connection passage  36 . The pressurized air is then sent forward from the air outlet port  26  of each slider  23 . 
     An engagement lever  38  defining a fixing portion is arranged on a bottom surface of each socket  22 , extending in the front-rear direction of the corresponding slider  23  and below the slider  23 . A projection  38   a  projects from a front end of each, engagement lever  38 . Thus, when the socket  22  receives (accommodates) the cartridge  18  (or the attachment  19 ) and the slider  23  is retracted, the front end of the corresponding engagement lever  38  from which the projection  38   a  projects is located forward from a front surface of the slider  23 . In this state, the projection  38   a , which projects from the front end of the engagement lever  38 , is engaged with an engagement portion  47  formed in the cartridge  18  (see  FIG. 4A ) or an engagement portion  56  formed in the attachment  19  (see  FIG. 5 ). This immovably holds the cartridge  18  or the attachment  19  in the socket  22 . 
     Next, the cartridge  18  and the attachment  19 , which are mutually replaceable and received in each socket  22  of the cartridge holder  17 , will be explained. The explanation starts with the cartridge  18  with reference to  FIGS. 4A and 4B  and proceeds to the attachment  19  with reference to  FIG. 5 . 
     As shown in  FIGS. 4A and 4B , the cartridge  18  includes a box-like casing  39  formed of synthetic resin. An annular wall  40  defines an accommodation chamber (a first air inlet chamber)  41  having a constant volume in the casing  39 . The accommodation chamber  41  accommodates an ink pack  42 , or a flexible bag, in which the ink is sealed. An ink outlet member  43  is arranged at an end of the ink pack  42  (the left end of the ink pack  42  as viewed in  FIG. 4B ) as a liquid outlet portion. The ink is thus introduced from the ink pack  42  to the exterior through the ink outlet member  43 . Although not illustrated, a valve mechanism (not shown) functioning as a check valve is provided in the ink outlet member  43 . The casing  39  is shaped like a non-lidded box with a bottom. The upper opening of the casing  39  is blocked by a lid member (not shown). 
     A first liquid outlet port  44  functioning as a support port extends through a substantial center of a front surface  39   a  (located forward in the insert direction when the cartridge  18  is inserted (received) in the socket  22 ) of the casing  39 . The first liquid outlet port  44  corresponds to the through hole  25  extending through the slider  23  of the socket  22 . Thus, when the cartridge  18  is inserted (accommodated) in the socket  22 , the first liquid outlet port  44  is positioned with respect to the through hole  25 . The ink outlet member  43  of the ink pack  42 , which is accommodated in the casing  39 , is inserted in and supported by the first liquid outlet port  44 . Therefore, when the cartridge  18  is inserted (accommodated) in the socket  22  and the first liquid outlet port  44  of the casing  39  is positioned with respect to the through hole  25  of the slider  23 , the front end of the ink supply needle  34 , which projects forward from the through hole  25 , is connected to the ink outlet member  43  of the ink pack  42  in a state positioned with respect to the ink outlet member  43 . 
     A pair of positioning recesses  45   a ,  45   b  are defined at positions close to opposing lateral ends of the front surface  39   a  of the casing  39 . The positioning recess  45   a  and the positioning recess  45   b  correspond to a positioning projection  24   a  and a positioning projection  24   b , respectively, each of which is projected from the slider  23  of the socket  22 . Thus, when the cartridge  18  is inserted (accommodated) in the socket  22 , the positioning recesses  45   a ,  45   b  are positioned with respect to the corresponding positioning projections  24   a ,  24   b . In this state, the positioning projections  24   a ,  24   b  are fitted in the corresponding positioning recesses  45   a ,  45   b  in such a manner as to restrict movement of the cartridge  18  in a direction crossing the insert direction, thus positioning the cartridge  18 . 
     A first air inlet port  46  is defined in the front surface  39   a  of the casing  39  at a position between the first liquid outlet port, 44  and the positioning recess  45   a  (the lower positioning recess as viewed in  FIG. 4A ). The first air inlet port  46  communicates with the accommodation chamber  41  in which the ink pack  42  is received. The first air inlet port  46  corresponds to the air outlet port  26  extending through, the slider  23  of the socket  22 . Thus, when the cartridge  18  is inserted (accommodated) in the socket  22 , the first air inlet port  46  is positioned with respect to the air outlet port  26 . In this state, the pressurized air that has been supplied from the pressurization pump  20  through the pressurized air supply tube  37  is introduced into the accommodation chamber  41  through the air outlet port  26  and the first air inlet port  46 . The ink pack  42  is thus squeezed and deformed by the pressurization force generated by the pressurized air, and the ink in the ink pack  42  moves out of the ink outlet member  43 . 
     An engagement portion  47  is defined at a position closer to the opposing end (the upper end as viewed in  FIG. 4A ) of the front surface  39   a  of the casing  39  and extends along a bottom surface (the left surface as viewed in  FIG. 4A ) of the casing  39 . The engagement portion  47  is engageable with the engagement lever  38 , which is provided in the socket  22  of the cartridge holder  17 . A circuit substrate  48  is secured to a portion of the other side surface (the upper surface as viewed in  FIG. 4A ) of the casing  39  that is closer to the front surface  39   a . The circuit substrate  48  is connectable to the terminal portion  27 , which is projected from the slider  23  of the socket  22 . Thus, when the cartridge  18  is inserted (accommodated) in the socket  22 , the engagement portion  47  becomes engaged with the engagement lever  38  of the socket  22  and the circuit substrate  48  becomes connected to the terminal portion  27  of the socket  22 . 
     The attachment  19  will hereafter be explained. 
     As shown in  FIG. 5 , the attachment  19  has an attachment body  49  shaped like a box having a bottom and a lid member  50 , which can cover an upper opening defined in the attachment body  49 . The attachment body  49  and the lid member  50  include a plurality of engagement recesses  51  and a plurality of engagement pieces  52 , respectively. Each of the engagement recesses  51  is defined at a position coinciding with the position at which the corresponding one of the engagement pieces  52  is arranged. The engagement recesses  51  are thus elastically engaged with the corresponding engagement pieces  52 . Through such engagement, the lid member  50  is engaged with and held by the attachment body  49 . 
     The attachment body  49  is shaped substantially identical to the casing  39  of the cartridge  18  of  FIGS. 4A and 4B . Specifically, an annular wall  53 , like the annular wall  40  formed in the casing  39  of the cartridge  18 , is provided in the attachment body  49 . A second liquid outlet port  54  and a pair of positioning recesses  55   a ,  55   b  are defined in a front surface  49   a  of the attachment body  49  at positions corresponding to the first liquid outlet port  44  and the positioning recesses  45   a ,  45   b , which are defined in the casing  39  of the cartridge  18 . The second liquid outlet port  54  and the positioning recesses  55   a ,  55   b  are configured in the same manner as the first liquid outlet port  44  and the positioning recesses  45   a ,  45   b , respectively. Further, an engagement portion  56  and a circuit substrate  57  are provided in the attachment body  49  at positions corresponding to the engagement portion  47  and the circuit substrate  48 , which are arranged in the casing  39  of the cartridge  18 . The engagement portion  56  and the circuit substrate  57  are configured in the same manner as the engagement portion  47  and the circuit substrate  48 , respectively. 
     A blocking portion  58  shaped like a circular seat is formed on the front surface  49   a  of the attachment body  49  at a position corresponding to the first air inlet port  46 , which is defined in the front surface  39   a  of the casing  39  of the cartridge  18 . In this regard, the attachment body  49  is configured differently from the casing  39  of the carriage  18 . Further, unlike the casing  39  of the cartridge  18 , the attachment body  49  includes cutout portions  59 , or tube support portions. The cutout portions  59  are defined in a portion (a rear portion) of a circumferential wall  49   b  and a corresponding portion of the wall  53  of the attachment body  49 . 
     As has been described, the ink pack  42  is accommodated in the accommodation chamber  41  defined in the casing  39  of the carriage  18 . An ink outlet member  60  functioning as a link portion and a liquid outlet member is separably received in the attachment body  49 . A passage in which the ink flows, or a link passage  61 , extends through the ink outlet member  60 . A distal end (a downstream end)  62   a  of an ink tube  62  serving as a flexible ink supply tube (defining a liquid supply passage) is connected to a proximal end  60   a  of the ink outlet member  60 , which is an upstream end of the link passage  61 . 
     A support portion  65  is arranged inside the wall  53  of the attachment body  49  and in the vicinity of the second liquid outlet port  54 , or a support port, which is defined in the front surface  49   a  of the attachment body  49 . The support portion  65  includes a pair of ribs  63   a ,  63   b  and a support seat  64 . The ink outlet member  60  is positioned by the support portion  65  with a distal end  60   b  of the ink outlet member  60 , or a downstream end of the link passage  61 , passed through and supported by the second liquid outlet port  54 . The ink outlet member  60  is thus secured to the attachment body  49 . In this state, a portion of the ink tube  62  located proximally (upstream) from the distal end (the downstream end)  62   a  is supported by the corresponding cutout portion  59 , which is defined in the circumferential wall  49   b  and the wall  53  of the attachment body  49 . 
     A coil spring  66 , a stopper  67  for blocking the link passage  61 , and an annular packing  68  including a stopper seat (not shown) are incorporated in the link passage  61  at the distal end  60   b  of the ink outlet member  60 . The link passage  61  is thus normally held in a closed state by the stopper  67  that is urged toward the packing  68  by the coil spring  66 . However, when the attachment body  49  is inserted (accommodated) in the socket  22  of the cartridge holder  17 , the front end of the ink supply needle  34  is passed through the second liquid outlet port  54  and thus presses the stopper  67  into the link passage  61  against the urging force of the coil spring  66 . This disengages the link passage  61  from the stopper  67  and allows the ink to flow through the link passage  61 . 
     In the attachment  19  constructed as above-described, the attachment body  49  is shaped identically to the casing  39  of the cartridge  18 . The second liquid outlet port  54 , the positioning recesses  55   a ,  55   b , the engagement portion  56 , and the circuit substrate  57  are arranged in the attachment body  49  at the positions coinciding with the positions of the first liquid outlet port  44 , the positioning recesses  45   a ,  45   b , the engagement portion  47 , and the circuit substrate  48  of the casing  39  of the cartridge  18 . The attachment  19  is thus mountable to the socket  22  of the cartridge holder  17  in the same manner as the cartridge  18 , or replaceable with the cartridge  18 . 
     An ink supply system of the first embodiment will hereafter be explained. 
     As shown in  FIG. 6 , in operation, the printer  10  of the illustrated embodiment is mounted on a rack  69  having a multiple-stage structure. The rack  69  includes a lower mounting portion  69   a , an intermediate mounting portion  69   b , and an upper mounting portion  69   c . The printer  10  is mounted on the intermediate mounting portion  69   b . A waste liquid tank  70 , or an external waste liquid collector, is provided on the lower mounting portion  69   a . A waste liquid tube  71  defining a waste liquid passage connects the waste liquid tank  70  to the printer  10 . An upstream end of the waste liquid tube  71  is connected to a waste liquid collector (not shown) provided in the printer  10 . After having been drained from the printer  10 , waste ink (waste liquid) is sent to the waste liquid tank  70  having an increased capacity, which is located-below the printer  10  and connected to the printer  10  through the waste liquid tube  71 . 
     An external tank  72 , or an external retainer retaining a greater volume of ink than the ink pack  42  of each cartridge  18 , is mounted on the upper mounting portion  69   c  of the rack  69 . An upstream end of the ink tube  62  is introduced into a retainer chamber  72   a , which is defined in the external tank  72  and retains the ink. A downstream end of the ink tube  62  is connected to the ink outlet member  60  of the attachment  19 . The ink is thus supplied from the retainer chamber  72   a  of the external tank  72  to the attachment  19  through the corresponding ink tube  62  due to the difference between the liquid head in the attachment  19  and the liquid head in the retainer chamber  72   a.    
     In other words, by arranging the external tank  72  at a position higher than the attachment  19 , a difference is ensured between the level of the ink Ik in the external tank  72  and the level of the ink Ik in the attachment  19 . The distal end of the corresponding ink tube  62 , or a supply tube connected to a liquid supply port  125  of the attachment  19 , is passed through a lid  133  secured to the upper end of the external tank  72 . The distal end of the ink tube  62  is this received in the bottom of the external tank  72 . An air port  133   a  is defined in the lid  133  in such a manner that the atmospheric pressure acts on the surface of the ink Ik. 
     In the illustrated embodiment, the attachment  19 , the external tank  72 , and the corresponding ink tube  62  define a liquid supply apparatus  73  serving as an ink supply apparatus that supplies the ink (the liquid) to the printer  10 . 
     Operation of the attachment  19  and the liquid supply apparatus  73  of the printer  10  will hereafter be described. 
     If the cartridge  18  is held in the cartridge holder  17  when the work load of the printer  10  is to be increased, the cartridge  18  is removed from the cartridge holder  17  and replaced by the attachment  19 , which is inserted in the cartridge holder  17 . In such insertion, the slider  23  of the socket  22  is pressed by the attachment  19  to move from the position (a standby position) illustrated in the left and near socket  22  ( 22   a ) of  FIG. 3  to the position (an insert position) illustrated in the right and far socket  22  ( 22   b ) of the drawing. At the insert position, the attachment  19  is arranged (accommodated) in the socket  22  in such a manner that the second liquid outlet port  54  or the like defined in the front surface  49   a  of the attachment body  49  are positioned with respect to the through hole  25  or the like defined in the slider  23  of the socket  22 . 
     Specifically, the positioning projections  24   a ,  24   b  of the slider  23  are positioned with respect to and fitted in the positioning recesses  55   a ,  55   b  of the attachment body  49 . The engagement lever  38  of the socket  22  is engaged with the engagement portion  56  of the attachment body  49 , thus engaging and holding the attachment  19  in an immovable state. The terminal portion  27  of the slider  23  is connected to the circuit substrate  57  of the attachment body  49 , allowing communication between the attachment  19  and a controller (not shown) of the printer  10  for transmitting and receiving information regarding the ink consumption or the like. The blocking portion  58  of the attachment body  49  is positioned with respect to the air outlet port  26  of the slider  23  and thus blocks the air outlet port  26 . 
     Further, the front end of the ink supply needle  34  of the socket  22  is positioned with respect to and inserted in the second liquid outlet port  54  of the attachment body  49  (and the distal end  60   b  of the ink outlet member  60 ). The stopper  67  blocking the link passage  61  is thus further inserted into the link passage  61  against the urging force of the coil spring  66 . This opens the link passage  61 , allowing the ink to quickly flow into the inlet port  34   a  of the ink supply needle  34  through the link passage  61  after having been sent from the external tank  72  to the ink outlet member  60  of the attachment  19  through the corresponding ink tube  62  due to the liquid head difference. The ink then flows in the ink passage including the ink supply needle  34 , the connection pipe  35 , the connection passage  36 , and the tube ribbon  21  and is thus supplied to the valve unit  16  of the recording head  15 . 
     The first embodiment has the following advantages. 
     (1) When the attachment  19  is inserted in the socket  22  of the cartridge holder  17 , the second liquid outlet port  54  (the ink outlet member  60 ) of the attachment body  49  is positioned with respect to the through hole  25  (the ink supply needle  34 ) of the socket  22 . This permits supply of the ink to the printer  10 . In other words, by simply inserting (mounting) the attachment body  49  in the socket  22 , the ink supply from the external tank  72  to the recording head  15  of the printer  10  is permitted. The attachment  19  is thus easily and quickly installed in the printer  10 . Accordingly, the attachment  19  is extremely easy to use. 
     (2) The ink outlet member  60  in which the link passage  61  is defined is detachable and attachable with respect to the attachment body  49 . Thus, if clogging occurs in the link passage  61  or an operational problem happens in the stopper  67 , the ink outlet member  60  can be removed from the attachment body  49  for performing maintenance work. This makes it further easy to use the attachment  19  in the printer  10 . 
     (3) The cartridge holder  17  in which the attachments  19  are installed is immovably fixed to the body casing  11 , instead of the carriage  14 , which reciprocates when printing. Each of the ink tube  62  extending from the external tank  72  is thus prevented from being pulled by the carriage  14  when the carriage  14  is reciprocated. This ensures smooth supply of the ink from the external tank  72  to the attachment  19  through the corresponding ink tube  62 . 
     (4) The installation state of the ink tubes  62  may become unstable due to the flexibility of the material forming the ink tubes  62 . However, each cutout portion  59  of the attachment body  49  effectively supports the portion of the corresponding ink tube  62  upstream from the distal (downstream) end  62   a  of the ink tube  62 , which is connected to the ink outlet member  60 . This stabilizes the installation state of the ink tubes  62 , making it further easy to use the attachments  19 . 
     (5) In the liquid supply apparatus  73 , the external tank  72  is mounted on the upper mounting portion  69   c  of the rack  69  and the printer  10  in which the attachment  19  is installed is mounted on the intermediate mounting portion  69   b  of the rack  69 . This forcibly supplies the ink from the external tank  72  to the attachment  19  through the corresponding ink tube  62  due to the liquid head difference between the external tank  72  and the attachment  19 . This ensures a sufficient ink supply to the recording head  15  of the printer  10 . 
     (6) The printer  10  is mounted on the intermediate mounting portion  69   b  of the rack  69 . The waste liquid tank  70  is mounted on the lower mounting portion  69   a , which is located below the intermediate mounting portion  69   b . The waste liquid tank  70  is connected to the printer  10  through the waste liquid tube  71 . Thus, the waste ink (the waste liquid) drained from the printer  10  is effectively sent to the waste liquid tank  70  using the liquid head difference between the printer  10  and the waste liquid tank  70 . 
     (7) There may be cases in which the printer  10  includes a detection mechanism. The detection mechanism detects a pressurization error (for example, air leakage) when the amount of the pressurized air supplied by the pressurization pump  20  exceeds a predetermined level. When the cartridge  18  is replaced by the attachment  19 , the pressurization error may be detected erroneously. However, in the illustrated embodiment, when the attachment  19  is inserted (accommodated) in the socket  22  of the cartridge holder  17 , the blocking portion  58  of the front surface  49   a  of the attachment body  49  blocks the air outlet port  26  defined in the slider  23  of the socket  22 . This structure prevents the aforementioned erroneous error detection. 
     A second embodiment of the present invention will hereafter be described with reference to  FIGS. 7A and 7B . 
     Unlike the attachment  19  of the first embodiment, an attachment  74  of the second embodiment includes a second air inlet port  75  and an air inlet chamber  76  instead of the blocking portion  58  of the attachment  19 . The remainder of the attachment  74  is identical to the corresponding parts of the attachment  19 . Therefore, same or like reference numerals are given to parts (components) of the second embodiment that are the same as or like corresponding parts of the first embodiment and detailed description thereof will be omitted. The following description thus focuses on the difference between the first embodiment and the second embodiment. 
     As shown in  FIGS. 7A and 7B , in the second embodiment, a second air inlet port  75  is defined in the front surface  49   a  of the attachment body  49  of the attachment  74 . An air inlet chamber  76  is defined in the attachment body  49  at a position corresponding to the second air inlet port  75 . The volume of the air inlet chamber  76  is smaller than the volume of the accommodation chamber  41 , which serves as the air inlet chamber defined in the casing  39  of the cartridge  18 . 
     Thus, in the second embodiment, when the attachment  74  is inserted (accommodated) in the socket  22  of the cartridge holder  17 , the second air inlet port  75  defined in the front surface  49   a  of the attachment body  49  is positioned with respect to and connected to the air outlet port  26  defined in the slider  23  of the socket  22 . This allows the pressurized air supplied by the pressurization pump  20  to flow from the air outlet port  26  into the air inlet chamber  76 .through the second air inlet port  75 . 
     Accordingly, in addition to the advantages (1) to (6) of the first embodiment, the second embodiment has the following advantages. 
     (8) The printer  10  may have a detection mechanism, which detects a pressurization error (for example, air leakage) when the amount of the pressurized air supplied by the pressurization pump  20  exceeds a predetermined level (for example, a level corresponding to the volume of the accommodation chamber  41  of the cartridge  18 ). When the cartridge  18  is replaced by the attachment  19 , the pressurization error may be detected erroneously. However, in the second embodiment, with the attachment  74  inserted (accommodated) in the socket  22  of the cartridge holder  17 , the acceptable amount of the pressurized air flowing from the air outlet port  26  of the slider  23  into the air inlet chamber  76  through the second air inlet port  75  of the attachment body  49  is set to an extremely small value. This prevents the aforementioned erroneous error detection, substantially in the same manner as has been described in the advantage (7) of the first embodiment. 
     (9) There may be cases in which the printer  10  includes a control system that detects a pressurization error (for example, insufficient pressurization caused by blockage of an air path) if the amount of the pressurized air supplied by the pressurization pump  20  is smaller than a predetermined level (for example, the level corresponding to the volume of the air inlet chamber  76  of the attachment  74 ). The second embodiment is particularly advantageous in that such detection error is effectively detected. 
     A third embodiment of the present invention will now be described with reference to  FIG. 8 . 
     As shown in  FIG. 8 , in the third embodiment, an attachment  77  is a large-sized type formed by integrating a number of (in the third embodiment, six) the attachments  19  of the first embodiment corresponding to the quantity of the sockets  22  of the cartridge holder  17 . In the attachment  77 , the attachments  19  are aligned in parallel and formed as an integral body. The attachment  77  includes an attachment body  78  and a lid member  79 . The attachment body  78  has a shape defined collectively by six attachment bodies  49  of the attachment  19  of the first embodiment, which are aligned in parallel. The lid member  79  has a shape collectively defined by six lid members  50  of the attachment  19  of the first embodiment, which are aligned in parallel. 
     Although not illustrated, six ink outlet members  60 , each of which is identical to the ink outlet member  60  of the first embodiment, are removably installed and equally spaced in the attachment body  78 . When the attachment  77  is received in the cartridge holder  17 , each of the ink outlet members  60  is positioned with respect to the corresponding one of the ink supply needles  34 , which are each provided in the corresponding one of the six sockets  22 . In the attachment  77 , each ink tube  62 , which has the distal end  62   a  connected to the proximal end  60   a  of the corresponding ink outlet member  60 , is introduced out to the exterior through the cutout portions  59  of the attachment body  78 . Each ink tube  62  is thus connected to the external tank  72  (see  FIG. 6 ). 
     Accordingly, the third embodiment has the following advantage in addition to the advantages (1) to (6) of the first embodiment. 
     To replace the multiple (six) cartridges  18  by the attachment  77  in the cartridge holder  17 , removal of the cartridges  18  must be repeated for six times. Contrastingly, through a single replacement of the attachment  77 , the ink outlet members  60  are simultaneously connected to the ink supply needles  34  of the corresponding sockets  22 . In other words, the attachment  77  is defined as a simply attachable multi-color attachment  77  corresponding to the cartridges  18  of the six color inks. The attachment  77  is thus further quickly installed. 
     A fourth embodiment of the present invention will now be described with reference to  FIGS. 9 to 11 . 
     As shown in  FIGS. 9 and 10 , in the fourth embodiment, an attachment  80  has an attachment body  81  and a lid member  82 . The attachment body  81  is shaped like a laterally elongated box with a bottom. The lid member  82  covers an upper opening of the attachment body  81 . Referring to  FIG. 10 , a plurality of (in the fourth embodiment, six) lower support portions  83   a  are formed on a front surface  81   a  of the attachment body  81  and equally spaced in a lateral direction of the attachment body  81 . In correspondence with the lower support portions  83   a  of the attachment body  81 , a plurality of (in the fourth embodiment, six) upper support portions  83   b  are formed on a front end  82   a  of the lid member  82 . Each of the lower support portions  83   a  and the corresponding one of the upper support portions  83   b  have opposing semicircular ends. The lower support portions  83   a  and the corresponding upper support portions  83   b  are mutually engaged when the attachment body  81  is covered by the lid member  82 . This defines a plurality of (in the fourth embodiment, six) support ports  83  that are aligned in parallel and spaced equally in the lateral direction of the attachment body  81  (see  FIG. 9 ). 
     A support portion  84  defined by a flanged groove is defined behind each of the lower support portions  83   a  of the attachment body  81 . An ink outlet member (a link portion)  60  like the one for the attachment  19  of the first embodiment is separably supported by each support portion  84 . The distal end (the downstream end)  62   a  of the corresponding ink tube  62 , or the liquid supply passage extending from the external tank  72  (see  FIG. 6 ), is connected to the proximal end  60   a  of the corresponding ink outlet member  60 , or the upstream end of the link passage  61  of the ink outlet member  60 . 
     A pair of positioning recesses  85   a ,  85   b  are defined in opposing lateral ends of the front surface  81   a  of the attachment body  81 . A waste ink inlet port (a second waste liquid inlet portion)  86  is provided at the left side of the positioning recess  85   a  of one end (in  FIG. 9 , the right end) of the front surface  81   a  of the attachment body  81 . The waste ink (the waste liquid) is introduced into the attachment body  81  through the waste ink inlet port  86 . A flanged support groove  87  is defined behind the waste ink inlet port  86 . A waste ink inlet member  88  identical to the ink outlet member  60  is separably supported by the support groove  87 . The waste liquid tube  71 , which extends from the waste liquid tank  70  (see  FIG. 6 ) is connected to the waste ink inlet member  88 . 
     A flat, second contact portion  89  is defined at the left side of the positioning recess  85   b  of the opposing end (the left end of  FIG. 9 ) of the front surface  81   a  of the attachment body  81 . A circuit substrate receiving recess  90  is defined in the front surface  81   a  of the attachment body  81  and below the second contact portion  89 . A non-illustrated circuit substrate is received in the circuit substrate receiving recess  90 . Like the attachment  77  of the third embodiment, the attachment  80  of the fourth embodiment is a multi-color attachment  80 . The attachment  80  is mounted on the cartridge holder  17  as a replacement of a multi-color cartridge (not shown) that incorporates six color-ink packs and has the same configuration as the attachment  80 . The cartridge includes a first waste liquid inlet portion (a waste ink inlet port) defined in a front surface of the cartridge. The cartridge thus functions as a waste liquid collector. A first contact portion (not shown) is also defined in the front surface of the cartridge. The first contact portion contacts and presses the valve opening lever  99 , which will be described later. 
     The cartridge holder  17  will now be described with reference to  FIGS. 11 and 12 . The attachment  80  is received in the cartridge holder  17  as a replacement of the multi-color cartridge functioning as a waste liquid collector. 
     As shown in  FIG. 11 , in the fourth embodiment, the cartridge holder  17  includes a substantially parallelepiped connection portion  91 , which is laterally elongated like the attachment  80  (or the cartridge). The connection portion  91  has a front surface  91   a  that faces the front surface  81   a  of the attachment body  81  when the attachment  80  is received in the cartridge holder  17 . A pair of positioning projections  92   a ,  92   b  are projected from the front surface  91   a  of the connection portion  91  at positions corresponding to the positioning recesses  85   a ,  85   b  of the attachment  80 . A terminal portion  93  is projected from the front surface  91   a  at a position corresponding to the circuit substrate receiving recess  90  of the attachment  80 . 
     Thus, when the attachment  80  is mounted on the connection portion  91 , each of the positioning projections  92   a ,  92   b  is fitted in the corresponding one of the positioning recesses  85   a ,  85   b . This restricts movement of the attachment  80  in a direction crossing the insert direction of the attachment  80  (in  FIG. 11 , a horizontal direction). In this state, the terminal portion  93  contacts the circuit substrate received in the circuit substrate receiving recess  90 , thus permitting communication between the attachment  80  and the controller (not shown) of the printer  10  for transmitting and receiving information regarding the ink consumption or the like. Although not illustrated, an engagement portion is provided in the attachment  80  and an engagement lever is formed in the connection portion  91 . Through engagement between the engagement portion and the engagement lever, the attachment  80  is immovably mounted on the connection portion  91  of the cartridge holder  17 . 
     A waste ink outlet needle (a waste liquid outlet portion)  94  is projected from the front surface  91   a  of the connection portion  91  at a position corresponding to the waste ink inlet port  86  of the attachment  80 . Ink supply needles (liquid inlet portions)  95  are projected from the front surface  91   a  at positions corresponding to the support ports  83 . A non-illustrated inlet bore is defined in the distal end of each of the ink supply needles  95 . Ink passages (liquid passages)  96  are defined in the connection portion  91  in correspondence with the ink supply needles  95 . The proximal end of each ink supply needle  95  is connected to the corresponding ink passage  96 . 
     Thus, when the attachment  80  is mounted on the connection portion  91 , the waste ink outlet needle  94  is fitted in the waste ink inlet port  86 . The waste ink drained from the printer  10  is sent from the waste ink inlet member  88  to the waste liquid tank  70  (see  FIG. 6 ) through the waste liquid tube  71 . Meanwhile, the ink supplied from the external tank  72  through the corresponding ink tube  62  flows in the link passages  61  of the ink outlet members  60  and is introduced into each of the ink passages  96  of the connection portion  91  through the corresponding ink supply needles  95 . 
     A passage valve  97  is provided in the connection portion  91 . A communicating portion  98  is projected from the front surface  91   a  of the connection portion  91 . After having been introduced into each ink passage  96 , the ink passes through the passage valve  97  and is supplied to the recording head  15  of the printer  10  through the communicating portion  98 . In order to stop a backflow of the ink, when the attachment  80  (or the cartridge) is not received in the connection portion  91 , the passage valve  97  is held in a closed state for maintaining the ink passages  96  in a closed state. Thus, referring to  FIG. 11 , a valve opening lever (a movable member)  99  is provided in the connection portion  91  at a position corresponding to the second contact portion  89  of the attachment  80 . When the attachment  80  is provided in the connection portion  91 , the valve opening lever  99  operates to open the ink passages  96 . 
     The valve opening lever  99  includes an operating piece  99   a , an operated piece  99   b , and a pivotal shaft  99   c . With the operating piece  99   a  and the operated piece  99   b  fixedly connected together, the pivotal shaft  99   c  functions as the pivotal center of the operating piece  99   a  and the operated piece  99   b . The operating piece  99   a  is shaped like a plate and a projection  99   d  projects from a corner of a front end of the operating piece  99   a . The operating piece  99   a  is (the operating piece  99   a  and the operated piece  99   b  are) urged by the force generated by a non-illustrated urging spring normally in the direction indicated by the arrow of  FIG. 11  (a counterclockwise direction). The front end of the operating piece  99   a  is thus maintained in a state slightly inclined with respect to the insert direction of the attachment  80 . 
     In this state, by installing the attachment  80  in the connection portion  91  of the cartridge holder  17 , the second contact portion  89  of the attachment  80  is brought into contact with the projection  99   d  of the operating piece  99   a  of the valve opening lever  99 . This pivots the operating piece  99   a  about the pivotal shaft  99   c  in a clockwise direction. The operated piece  99   b  is thus caused to pivot in the clockwise direction, switching the passage valve  97  from the closed state to the open state. This connects the recording head  15  of the printer  10  to the ink supply needles  95  through the corresponding ink passages  96 , thus permitting the ink supply. 
     Accordingly, in addition to the substantially equivalent advantages as the advantages (1) to (6) of the first embodiment, the fourth embodiment has the following advantages. 
     (11) When installing the attachment  80  in the connection portion  91  of the cartridge holder  17 , the second contact portion  89  of the attachment  80  presses the valve opening lever  99  of the connection portion  91  to switch to the open state. This effectively permits communication between the ink supply needles  95  and the recording head  15  through the ink passages  96 . Accordingly, modification of the printer  10  is unnecessary when installing the attachment  80  in the cartridge holder  17  having the passage valve  97  as a replacement of a cartridge. Also, the attachment  80  suppresses an ink back flow. That is, the attachment  80  is generally applicable to different printers. 
     (12) The attachment  80  includes the waste ink inlet port  86  and the waste ink inlet member  88 . Accordingly, if the attachment  80  is installed as a replacement of a cartridge functioning as a waste liquid collector, the waste ink is effectively sent to the waste liquid tank  70  through the waste liquid tube  71  after having passed through the waste ink inlet port  86  and the waste ink inlet member  88 . 
     The illustrated embodiments may be modified in the following forms. 
     As shown in  FIG. 13 , an area above the link level in the retainer chamber  72   a  of the external tank  72  may be defined as an air inlet chamber. An air supply tube  135 , or a pressurized air supply tube, supplies pressurized air into the air inlet chamber through actuation of an air pump  134  serving as a pressurization pump. Specifically, the air pump  134  is connected to the air port  133   a  of the lid  133 , which covers the upper end of the external tank  72 , through the air supply tube  135 . The level surface of the ink Ik in the external tank  72  thus receives air pressure generated by the air pump  134 , instead of atmospheric pressure. 
     This arrangement forcibly supplies the ink from the external tank  72  to the attachment  19  (or  74  or the attachment  77  or  80 ) through the corresponding ink tube  62  by the pressurization force generated by the pressurized air. Insufficient ink supply to the recording head  15  of the printer  10  is thus suppressed. 
     It is thus unnecessary to ensure a difference between the height of the external tank  72  and the height of the attachment  19 . Also, by controlling operation of the air pump  134 , supply of the ink supply pressure can be easily suspended or adjusted. 
       FIG. 14  is another modified embodiment performing the forcible ink supply. As shown in the drawing, a large-capacity ink pack  130  is received in the retainer chamber (the air inlet chamber)  72   a  of the external tank  72 . The pressurized air is introduced from the air pump  134 , the pressurization pump, into the retainer chamber  72   a  through the air supply tube  135 . That is, the air pressure produced by the air pump  134  is introduced into the external tank  72 , which is a sealed casing formed of hard material. This squeezes the ink Ik out of the ink pack  130  and sends the ink Ik to the attachment  19 . 
     In this case, the air pressure that squeezes the ink Ik out from the ink pack  130  ensures generation of supply pressure of the ink Ik, which is supplied to the attachment  19 . It is thus unnecessary to provide a difference between the height of the external tank  72  and the height of the attachment  19 . Further, by controlling operation of the air pump  134 , supply of the ink supply pressure can be easily suspended or adjusted. 
     Alternatively, as shown in  FIG. 15 , a liquid pump  137 , or a suction pump, may be arranged in each ink tube  62 , which connects the large-capacity ink pack  130  received in the retainer chamber  72   a  of the external tank  72  to the attachment  19  ( 74 ,  77 ,  80 ). Specifically, the external tank  72  is defined as an open casing. The ink Ik is sent from the ink pack  130  in the external tank  72  to the attachment  19  through pressurization by the liquid pump  137 . This ensures generation of the supply pressure of the ink Ik. 
     In this case, through actuation of the liquid pump  137 , the ink is drawn from the ink pack  130 , which is located upstream from the liquid pump  137 . The ink is then forcibly supplied to the attachment  19  ( 74 ,  77 ,  80 ), which is located downstream from the liquid pump  137 . Accordingly, by controlling operation of the liquid pump  137 , supply of the ink supply pressure is easily suspended or adjusted. 
     A waste ink inlet port (a waste liquid inlet port) may be defined in the attachment body  49  (the attachment body  78 ) of the attachment  19  (the attachment  74 ,  77 ). A waste ink inlet member is secured to the attachment body  49  (the attachment body  78 ). A waste liquid tube (a waste liquid passage) is connected to the ink inlet member, thus sending the waste ink to the waste liquid tank. 
     In the fourth embodiment, the valve opening lever  99  is employed as the movable member that selectively opens and closes the ink passages (the liquid passages)  96  by being pressed by or released from the second contact portion  89  of the attachment  80 . However, the movable member may be defined by any suitable component other than the valve opening lever  99 , such as a component that selectively opens and closes the passage valve  97  through linear movement caused by pressing by the second contact portion  89 . 
     In the second embodiment, the volume of the air inlet chamber  76  in the attachment body  49  may be altered as needed, as long as such volume is smaller than the volume of the accommodation chamber  41  of each cartridge  18 . 
     As tube support portions of any of the attachment bodies  49 ,  78 ,  81 , tube support ribs or tube support grooves may be provided in addition to the cutout portions  59 . 
     The cartridge holder  17  may be arranged in the carriage  14  of the printer  10 . 
     As long as the ink outlet member  60 , which serves as the link portion and the liquid outlet member, has a cylindrical shape in which the link passage  61  is defined, the ink outlet member  60  may be defined by, for example, a simple pipe body. 
     The link portion may be formed integrally with the attachment body  49 ,  78 ,  81 . 
     A liquid container and a liquid supply apparatus according to a fifth embodiment of the present invention will hereafter be described with reference to the attached drawings. 
     As shown in  FIG. 16 , the printer  10  serving as an inkjet recording apparatus includes a recording head  15 , or a liquid ejecting portion, a sub tank  103 , a pressurization pump  20 , or an air pressurizing portion, and a cartridge holder  17 . The cartridge holder  17  holds a plurality of attachments  120 , or liquid containers according to the fifth embodiment. 
     Each of the attachments  120  has an outline identical to that of the typical cartridge  18  of  FIG. 25 . As illustrated in  FIG. 17 , each attachment  120  is formed by accommodating an ink pack  122  formed of flexible material in a sealed casing  121 , which is formed of hard resin. A second air inlet port  75  and a second liquid outlet port  54  are defined in one end of the sealed casing  121 . Externally produced pressurized air is introduced into the sealed casing  121  through the second air inlet port  75 . The pressurized air thus produces pressure that acts to send the ink (the liquid) Ik from the ink pack  122  to the exterior through the second liquid outlet port  54 . 
     When the attachments  120  are received in the cartridge holder  17  of the printer  10 , the second liquid outlet port  54  and the second air inlet port  75  are connected to the sub tank  103  and the pressurization pump  20 . 
     Unlike the cartridges  18 , a liquid supply port  125  is defined in the other end of the sealed casing  121  of each attachment  120 . The ink Ik is supplied from the exterior to the attachment  120  through the liquid supply port  125 . A check valve  126  is provided in the liquid supply port  125 . The check valve  126  opens when the external pressure is greater than the internal pressure. The check valve  126  closes when the internal pressure greater than the external pressure. 
     As illustrated in  FIG. 16 , the external tank  72  is connected to the liquid supply port  125  of each attachment  120  through the corresponding ink tube  62 . Thus, the attachment  120 , the ink tube  62 , and the external tank  72  define the liquid supply apparatus  73 . 
     The supply pressure of the ink (liquid supply) Ik, which acts to send the ink Ik from the external tank  72  to each attachment  120  through the liquid supply port  125 , is greater than the atmospheric pressure but smaller than the air pressure produced by the pressurization pump  20  (the outlet pressure of the ink Ik generated by the pressurized air, which acts to move the ink Ik out from the attachment  120  through the second liquid outlet port  54 ). 
     Operation of each attachment  120  and that of the liquid supply apparatus  73  will now be explained. 
     In the fifth embodiment, each attachment  120  includes the check valve  126  provided in the liquid supply port  125  of the attachment  120 . The supply pressure of the ink Ik, which acts to send the ink Ik from the external tank  72  to the attachment  120  through the liquid supply port  125 , is smaller than the outlet pressure of the ink Ik produced by the pressurized air, which acts to move the ink Ik out from the attachment  120  through the second liquid outlet port  54 . The check valve  126  thus closes if the pressurized air generated by the pressurization pump  20  flows into the attachment  120 , even when the ink Ik is being supplied from the external tank  72  to the attachment  120 . 
     When supply of the pressurized air by the pressurization pump  20  is suspended, the supply pressure of the ink Ik flowing from the external tank  72  (the pressure in the exterior of the attachment  120 ) becomes greater than the pressure in the attachment  120 . This opens the check valve  126 , thus introducing the ink Ik into the attachment  120 . 
     That is, the ink Ik can be supplied to each attachment  120  without influencing supply of the ink Ik into the recording head  15  by air pressure. Therefore, if the cartridge  18  is replaced by the attachment  120 , the attachment  120  is perfectly compatible with the pressurization pump  20  used in the ink pressurization supply system of the printer  10 . Normal operation of the printer  10  is thus ensured. 
     Further, since modification of the printer  10  is unnecessary when replacing each cartridge  18  by the attachment  120  according to the present invention, an optional supply system of the ink Ik from the large-capacity external tank  72  is easily employed. Also, since the supply pressure of the ink Ik to the attachment  120  is set to a value lower than the pressure produced by the pressurization pump  20  of the printer  10 , the configuration of the liquid supply apparatus  73  is simplified. 
     Accordingly, the attachments  120  and the liquid supply apparatus  73  can be employed without modifying the printer  10 , while ensuring compatibility between the attachments  120  and the liquid supply apparatus  73  and the pressurization pump  20  of the pressurization supply system of the ink Ik of the printer  10 . The attachment  120  and the liquid supply apparatus  73  thus stabilize supply of the ink Ik. 
     Referring to  FIG. 17 , in each attachment  120  of the fifth embodiment, the ink Ik is retained in the ink pack  122 , which is received in the sealed casing  121 . The pressurized air is introduced into the space defined outside the ink pack  122  in the sealed casing  121 , thus sending the ink Ik out from the ink pack  122 . However, as in an attachment  120 A of  FIG. 18 , the ink Ik may be retained directly in the sealed casing  121 . An air pack  122 A is received in the sealed casing  121  and the pressurized air is introduced into the air pack  122 A. Also in this case, the ink Ik can be introduced out of the attachment  120 A by the pressure corresponding to the pressure produced by the air from the pressurization pump  20 . 
     Next, methods for applying the supply pressure of the ink Ik, which is supplied from the external tank  72  of the liquid supply apparatus  73  to each attachment  120  ( 120 A) of the fifth embodiment, will be described. Specifically, the respective methods are illustrated in  FIGS. 6 and 13 to 15 . 
     In  FIG. 6 , the position head corresponding to the difference between the level of the ink Ik in the external tank  72  and the level of the ink Ik in the attachment  120  is applied to the liquid supply port  125  of the attachment  120  ( 120 A) as the supply pressure of the ink Ik. Such supply pressure is thus easily adjusted by altering the height of the level of the ink Ik in the external tank  72 . 
     In  FIG. 13 , the air pressure that presses the ink Ik in the external tank  72  ensures generation of the supply pressure of the ink Ik, which is supplied to the attachment  120  ( 120 A). 
     In  FIG. 14 , the air pressure that presses the ink Ik in the ink pack  130  ensures generation of the supply pressure of the ink Ik, which is supplied to the attachment  120  ( 120 A). Supply of the supply pressure is thus easily suspended or adjusted by controlling operation of the air pump  134 . 
     In  FIG. 15 , if the ink Ik is supplied to the attachment  120  ( 120 A) through pressurization by the liquid pump  137 , supply of the supply pressure is easily suspended or adjusted by controlling operation of the liquid pump  137 . 
     The configurations of the liquid container and the air inlet port, the liquid outlet port, the liquid supply port, the check valve, and the external tank of the liquid supply apparatus according to the present invention are not restricted to those of the illustrated embodiments. It is to be understood that these configurations may be modified in various forms in accordance with the intent of the present invention. 
     A liquid supply apparatus according to a sixth embodiment of the present invention will now be described with reference to the attached drawings. 
     As shown in  FIG. 19 , a liquid supply apparatus  100  according to an embodiment of the present invention is incorporated in the printer  10 . The printer  10  includes the recording head  15 , the sub tank  103 , the pressurization pump  20 , and the cartridge holder  17 . Referring to  FIG. 20 , attachments  220  are received in the cartridge holder  17 , instead of typical liquid cartridges. 
     Each of the attachments  220  has an outline identical to the outline of the typical cartridge  18  of  FIG. 25 . With reference to  FIG. 21 , a second liquid outlet port  54  and a second air inlet port  75  are defined at an end of a hollow casing  220 A of each attachment  220 , which is formed of hard resin. The second liquid outlet port  54  serves as a first connection port through which the ink Ik is sent out of the hollow casing  220 A. The second air inlet port  75  serves as a second connection port through which pressurized air is supplied from the exterior into the hollow casing  220 A. 
     When the attachment  220  is mounted on the cartridge holder  17  of the printer  10 , the second liquid outlet port  54  and the second air inlet port  75  of the attachment  220  are connected to the sub tank  103  and the pressurization pump  20  of the printer  10 , respectively. 
     Referring to  FIG. 21 , a distal end of an air detection tube  221  is,connected to the second air inlet port  75  of each attachment  220  from inside the hollow casing  220 A. A distal end of the corresponding ink tube  62 , or a tubular passage, is connected to the second liquid outlet port  54  of the attachment  220  from inside the hollow casing  220 A. The air detection tube  221  and the ink tube  62  are introduced out of the hollow casing  220 A from an opposing end of the hollow casing  220 A. The air detection tube  221  and the ink tube  62  are thus connected to a liquid supply apparatus body  100 A of  FIG. 20 . 
     The liquid supply apparatus  100  is formed by the liquid supply apparatus body  100 A, the air detection tubes  221 , the ink tubes  62 , and the attachments  220 . 
     As illustrated in  FIG. 19 , the liquid supply apparatus body  100 A includes the external tank  72 , a pressure detector  223 , and a pressure adjusting portion  225 . The external tank  72  retains the ink Ik (the liquid to be supplied) and is connected to the second liquid outlet port  54  of each attachment  220  through the corresponding ink tube  62 . The pressure detector  223  detects air pressure applied by the pressurization pump  20  of the printer  10  through the second air inlet port  75  of the attachment  220  and the air detection tube  221 . The pressure adjusting portion  225  adjusts the supply pressure of the ink Ik, which is sent from the external tank  72  to the second liquid outlet port  54  of the attachment  220 . 
     The pressure adjusting portion  225  includes a pressurizing portion  226 , a release valve  227 , and a CPU (a controller)  240 . The pressurizing portion  226  pressurizes the ink Ik in the external tank  72  to a level exceeding the supply pressure of the pressurization pump  20 . The release valve  227  adjusts the supply pressure by releasing the pressurization force generated by the pressurizing portion  226  as needed. The CPU  240  controls operation of the pressurizing portion  226  and operation of the release valve  227  in accordance with a detection signal generated by the pressure detector  223 . In this manner, the supply pressure of the ink Ik is set to a level equal to the pressure detected by the pressure detector  223 . 
     In the sixth embodiment, the volume of the portion of the air detection tube  221  from the second air inlet port  75  to the pressure detector  223  corresponds to the volume of the space for detecting the air pressure. The volume of this portion is set to a value substantially equal to the volume of the space for receiving the pressurized air in the typical cartridge  18  (see  FIG. 25 ). 
     Next, operation of the liquid supply apparatus  100  of the sixth embodiment will be explained. 
     When the liquid supply apparatus  100  of the sixth embodiment is received in the cartridge holder  17  as a replacement of the typical cartridges  18  (see  FIG. 25 ), the pressure adjusting portion  225  supplies the ink Ik to the recording head  15  by the supply pressure corresponding to the air pressure set by the printer  10 . An ink pressurization supply system provided by the liquid supply apparatus  100  is thus compatible with the ink pressurization supply system (the liquid pressurization supply system) provided by the pressurization pump  20  of the printer  10 . This ensures normal operation of the printer  10 . 
     That is, replaceability between the ink pressurization supply system of the cartridge  18  and the ink pressurization supply system of the liquid supply apparatus  100  is ensured. The ink Ik is thus supplied from the external tank  72  to the recording head  15 , allowing the printer  10  to operate normally. Particularly, the pressure adjusting portion  225  supplies the ink Ik to the recording head  15  by the pressure equal to the air pressure generated by the pressurization pump  20  of the printer  10 . Thus, the printing performance of the recording head  15  with the attachments  220  becomes equivalent to the printing performance of the recording head  15  with the typical cartridges  18 . Further, the attachments  220  become usable simply by replacing the cartridges  18 , without modifying the printer  10 . This makes it possible to employ the large-capacity external tank  72  as an option. 
     Further, in the sixth embodiment, the pressure adjusting portion  225  detects the air pressure applied by the pressurization pump  20  through the second air inlet port  75  by means of the pressure detector  223 . The supply pressure of the ink Ik is adjusted in accordance with the detected pressure. The supply pressure of the ink Ik is thus accurately controlled. 
     Controlling of the air pressure by the printer  10  is executed based on operation with the typical cartridges  18 . Thus, if the volume of the space from the second air inlet port  75  to the pressure detector  223  is greatly different from the volume of the space for introducing the pressurized air in each cartridge  18 , erroneous detection of a problem may occur in the printer  10 . However, in the sixth embodiment, since the volumes of these spaces are substantially equal to each other, such problem detection is avoided, allowing the printer  10  to operate stably. 
     Next, an example of the pressure adjusting portion  225  that adjusts the supply pressure of the ink Ik, which is supplied from the external tank  72  of the liquid supply apparatus  100  to the second liquid outlet port  54  of each attachment  220 , will be explained. As the pressure adjusting portion  225 , the different structures shown in  FIGS. 13 to 15, 22, and 23  may be employed. 
     In  FIG. 22 , a lift device  232  functions as the pressurizing portion  226 . The lift device  232  has a base  232   a  on which the external tank  72  is mounted and a movable portion  232   b  on which the external tank  72  is mounted. The external tank  72  is located higher than the attachment  220 . 
     In this pressure adjusting portion  225 , the position liquid head corresponding to the difference between the level of the ink Ik in the external tank  72  and the level of the ink Ik in the attachment  220  is supplied to the second liquid outlet port  54  of the attachment  220 . This structure makes it unnecessary to provide power to generate the supply pressure. 
     The height of the external tank  72  is adjustable by means of the lift device  232 . Through such adjustment, the extent of the position liquid head, which acts as the supply pressure of the ink Ik, is regulated. 
     Thus, by operating the lift device  232  in correspondence with an output of the pressure detector  223 , the CPU  240  adjusts the supply pressure of the ink Ik to a level equal to the air pressure generated by the pressurization pump  20 . The printing performance of the recording head  15  with the attachments  220  thus becomes equivalent to that of a case with the typical cartridges  18 . 
     In  FIG. 13 , the air pump  134  functions as the pressurizing portion  226 . In this pressure adjusting portion  225 , the supply pressure of the ink Ik sent to the second liquid outlet port  54  of the attachment  220  is ensured by the air pressure that acts to send the ink Ik out from the external tank  72 . Supply of the supply pressure is thus easily suspended or adjusted by controlling operation of the air pump  134 . 
     Also in  FIG. 14 , the air pump  134  functions as the pressurizing portion  226 . This pressure adjusting portion  225  also ensures generation of the supply pressure of the ink Ik without providing a difference between the height of the external tank  72  and the height of each attachment  220 . Further, the supply of the supply pressure is easily suspended or adjusted by controlling the operation of the air pump  134 . 
     In  FIG. 15 , the liquid pump  137  functions as the pressurizing portion  226 . In this pressure adjusting portion  225 , the supply pressure of the ink Ik is generated by the pressure of the liquid pump  137  that acts to send the ink Ik out from the external tank  72 . Thus, by controlling operation of the liquid pump  137 , supply of the supply pressure is easily suspended or adjusted. Further, through such controlling, the supply pressure of the ink Ik can be adjusted to the level equal to the air pressure of the pressurization pump  20 , which is introduced through the second air inlet port  75 . The resulting printing performance of the printer  10  thus becomes equivalent to the printing performance of the case with the typical cartridges  18 . 
     In  FIG. 23 , the air pump  134  functions as the pressurizing portion  226 . The ink pack  130  is received in the external tank  72  formed of hard material. The air pump  134  introduces fluid pressure such as air pressure into the external tank  72 , thus sending the ink Ik from the ink pack  130  to the second liquid outlet port  54  of the attachment  220 . The pressure adjusting portion  225  includes a valve  239  and a valve control section  241 . The valve  239  is arranged in the corresponding ink tube  62 , which is a pressurization supply passage extending from the external tank  72  to the second liquid outlet port  54  of the attachment  220 . The valve control section  241  controls operation of the valve  239  so that the supply pressure of the ink Ik becomes equal to the air pressure generated by the pressurization pump  20 , which is introduced through the second air inlet port  75 . The CPU  240  functions also as the valve control section  241 . 
     The air pump  134  sends the ink Ik from the external tank  72  to the second liquid outlet port  54  of the attachment  220  by pressure greater than the pressure generated by the pressurization pump  20 . 
     The pressure detector  223  detects the air pressure introduced from the pressurization pump  20  of the printer  10  through the second air inlet port  75  of the attachment  220  and the air detection tube  221 . By controlling operation of the valve  239  in correspondence with the pressure detected by the pressure detector  223 , the valve control section  241  adjusts the supply pressure of the ink Ik, which is supplied from the external tank  72  to the second liquid outlet port  54  of the attachment  220 . 
     In this pressure adjusting portion  225 , supply of the supply pressure of the ink Ik is easily suspended or adjusted by the valve control section  241  that controls operation of the valve  239 . Further, through such controlling, the supply pressure of the ink Ik is adjusted to the level equal to the air pressure introduced from the pressurization pump  20  through the second air inlet port  75 . The resulting printing performance of the printer  10  thus becomes equivalent to the printing performance of the case with the typical cartridges  18 . 
     Also, the valve control section  241  may adjust the supply pressure of the ink Ik, which is supplied from the external tank  72  to the second liquid outlet port  54  of the attachment  220 , by controlling the operation of the valve  239  directly by the air pressure produced by the pressurization pump  20  of the printer  10 , for example. 
     In the liquid supply apparatus according to the present invention, the air inlet port, the liquid outlet port, the first air inlet port, the attachments, the external tank, the pressure adjusting portion are not restricted to the configurations of the illustrated embodiments. It is to be understood that these components may be configured in different forms based on the intent of the invention. 
     For example, in the illustrated embodiments, the liquid cartridges have been explained as the cartridges of the inkjet recording apparatus (the printer) by way of example. However, it is to be understood that the present invention is applicable to different liquid cartridges that supply different liquids to liquid ejecting portions. The liquids include color material used by a color filter manufacturing apparatus, electrode material (conductive paste) for forming electrodes of organic EL displays or FEDs, and biological organic material used by a biochip manufacturing apparatus. 
     It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.