Abstract:
A printer cartridge stationarily fixes an ink package and movably provides a print head, and a separate printer body movably provides a carriage. Prior to mounting of the printer cartridge onto the printer body, the print head is held at a fixed position of the printer cartridge by a pressing member. Because the print head is pressed downward by the pressing member, mounting the cartridge onto the printer body will insert the print head into the carriage. After the print head is inserted into the carriage, a pawl and a protrusion of the carriage fit into an engagement groove and an indentation, respectively, in the print head. Also another protrusions of the print head are supported on an upper edge of the carriage. As a result, the print head is mounted onto the carriage in association with mounting of the print cartridge onto the printer body. A printer cartridge has a retaining member formed with an engaging groove, and the print head has a rectangular protrusion. When the printer cartridge is detached from the printer body, the rectangular protrusion is trapped by the upwardly moving retaining member and is engaged with the engaging groove. Thus, the print head is automatically disengaged from the carriage in interlocking relation with detachment of the printer cartridge from the printer body.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an image forming device and a cartridge unit capable of preventing different colored inks from mixing when exchanging a cartridge unit filled with one colored ink with that filled with another colored ink and capable of reducing load imparted on a driving means for driving a print head. 
     There has been known an ink jet type print device having a print head. Ink is supplied to the print head from an ink-filled ink cartridge. The print head ejects the ink onto a print sheet in order to print characters and the like. A variety of configurations are known for supplying ink from a cartridge to a print head. For example, Japanese Patent Application Publication (Kokai) HEI-5-218 discloses an ink cartridge connected by an ink supply tube to a print head, which is mounted on a carriage of a printing device. Ink filling the ink cartridge is supplied through the ink supply tube to the print head. 
     However, with this configuration, when the ink cartridge in this printing device is to be exchanged for a new one, ink from the old ink cartridge can remain in the ink supply tube and in the print head when the new cartridge is exchanged. When an ink cartridge filled with one color of ink is replaced with an ink cartridge filled with a different color of ink, then the ink remaining in the ink supply tube and the print head can undesirably mix with the ink in the new ink cartridge. For example, if the ink cartridge presently mounted on the carriage is filled with black ink and the ink cartridge to replace the present ink cartridge is filled with magenta colored ink, then the black ink remaining in the ink supply tube and the print head can mix into the newly supplied magenta colored ink and change the color of the magenta colored ink. 
     Japanese Patent Publication (Kokoku) SHO-62-42792 discloses a print head cartridge configured from an integral print head and ink tank. A printing device using this print head cartridge can print in a desired color when a print head cartridge filled with a desired colored ink is mounted onto the carriage of the printing device. Further, when the print head cartridge is exchanged, the print head is also exchanged, so undesirable mixing of different colored inks can be prevented. 
     Since the print head cartridge includes not only the print head but also the ink tank, the load weight on the carriage includes not only the print head but also the ink tank. Therefore, the carriage motor for driving the carriage must be large enough to also move the weight of the ink tank, thereby requiring a large carriage motor. Further, a large amount of power is used for driving the carriage motor. 
     Further, as the ink stored in the ink tank is consumed during printing operations, the load on the carriage drops. As a result, the load imparted on the carriage motor fluctuates over time. When the load on the carriage motor fluctuates, the moving speed of the carriage also fluctuates so that it is difficult to obtain uniform and proper printing quality. As a result, there is a need to provide a separate control means for controlling moving speed of the carriage in association with change in the amount of ink in the ink tank. This special control device increases the production costs of the printing device. 
     Japanese Patent Application Publication (Kokai) HEI-6-234209 discloses a printing device having a print head and an ink tank connected together by an ink supply tube. The print head and ink tank form a unit that can be exchanged by detaching the unit from the main body of the printing device. The ink tank is fixed to a predetermined position of the unit, and only the print head is mounted on the carriage of the printing device. 
     Therefore, even when the ink in the ink tank is consumed during printing operations, load on the carriage will remain the same. For this reason, load on the carriage motor will also remain stable so that uniform and proper printing quality can be achieved. Further, printing can be performed in the desired colored ink by mounting a unit, including an ink tank filled with a desired colored ink, onto the main body of the printing device. By exchanging the unit, the print head is also exchanged so that undesirable mixing of different colored inks can be prevented. 
     SUMMARY OF THE INVENTION 
     However, with the exchangeable unit disclosed in Japanese Patent Application Publication (Kokai) HEI-6-234209, the print head must be grasped by fingers for its attachment to or detachment from the carriage. This makes exchanging the unit very troublesome. Further, because the user must grasp the print head by hand when detaching the print head from the carriage, the user may touch the nozzles of the print head, the user can stain his or her hands with ink. 
     It is, therefore an object of the present invention to overcome the above-described problems and to provide an image forming device and a cartridge unit capable of preventing undesirable mixture of ink when cartridge units for different colored inks are used, and capable of reducing the load imparted on the driving means for driving the print head, and enabling replacement of the print head on the carriage with a simple mounting operation. 
     These and other object of the present invention will be attained by providing an image forming device for forming an image on a print sheet including a printer body, a cartridge unit, a print head, a colored agent supply means, a carriage, driving means, and assisting means. The cartridge unit is detachably provided to the printer body. The print head impinges a colored agent onto the print sheet to print on the print sheet. The print head is slidably movably disposed in the cartridge unit. The colored agent supply means supplies colored agent to the print head. The supply means is disposed at a fixed position in the cartridge unit. The carriage is provided in the printer body and is reciprocally movable therein. The print head is detachably mounted on the carriage and is movable in accordance with the reciprocal movement of the carriage. The driving means is disposed in the printer body and drives the carriage. The assisting means assists mounting of the print head onto the carriage in interlocking relation with mounting of the cartridge unit onto the printer body. 
     In another aspect of the invention, there is provided an image forming device for forming an image on a print sheet including the printer body, the cartridge unit, the print head, the colored agent supply means, the carriage, the driving means, and a print head detachment means. The print head detachment means is adapted for detaching the print head from the carriage in interlocking relation with detachment of the cartridge unit from the printer body. 
     In still another aspect of the invention, there is provided an image forming device for forming an image on a print sheet including the printer body, the cartridge unit, the print head, the colored agent supply means, the carriage, the driving means, the assisting means, and the print head detachment means. 
     In still another aspect of the invention, there is provided a cartridge unit for use in combination with an image forming device, the image forming device having a printer body and a carriage reciprocally movably disposed therein, the cartridge unit including a cartridge case, a print head, a colored agent supply means, and assisting means. The cartridge case is detachably mountable to the printer body. The print head impinges a colored agent onto a print sheet to print on the print sheet. The print head is detachably mountable to the carriage and reciprocally movable in the cartridge case. The colored agent supply means supplies colored agent to the print head. The colored agent supply means is disposed at a predetermined position on the cartridge case. The assisting means assists mounting of the print head onto the carriage in interlocking relation with mounting of the cartridge unit onto the printer body. 
     In still another aspect of the invention, there is provided a cartridge unit for use in combination with an image forming device, the image forming device having a printer body and a carriage reciprocally movably disposed therein, the cartridge unit including the cartridge case, the print head, the colored agent supply means, and a print head detachment means. The print head detachment means is adapted for detaching the print head from the carriage in interlocking relation with detachment of the cartridge unit from the printer body. 
     In still another aspect of the invention, there is provided a cartridge unit for use in combination with an image forming device, the image forming device having a printer body and a carriage reciprocally movably disposed therein, the cartridge unit including the cartridge case, the print head, the colored agent supply means, the assisting means, and the print head detachment means. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is an exploded perspective view showing an ink jet printer including a printer cartridge according to a first embodiment of the present invention; 
     FIGS. 2 is a cross-sectional view showing a portion of a print head of the printer shown in FIG. 1; 
     FIG.;  3  is an exploded perspective view showing an ink cartridge including an ink package used in the printer of FIG. 1; 
     FIG. 4 is a graph representing effect that thickness of laminated sheet forming the ink package has on the relationship between pressure in the ink packages and consumption of ink from the ink package; 
     FIG. 5 is a graph representing effect that length to wide ratio of ink package has on the relationship between pressure in the ink package and consumption of ink from the ink package; 
     FIG. 6 is a graph representing effect that length of the ink package has on the relationship between pressure in the ink packages and consumption of ink from the ink package; 
     FIG. 7 is a chart showing the effect that diameter of a needle used to pierce and extract ink from the ink package has on quality of seal formed between the ink package and the ink extraction needle; 
     FIG. 8 is an exploded perspective view showing an ink jet printer including a printer cartridge according to a second embodiment of the present invention; 
     FIG. 9 an exploded perspective view showing an ink jet printer including a printer cartridge according to a third embodiment of the present invention; 
     FIG. 10 is plan view showing an ink jet printer according to a fourth embodiment of the present invention; 
     FIG. 11 is a cross-sectional view taken along the line XI—XI of FIG. 10; 
     FIG. 12 is a front view as viewed from the line XII—XII of FIG. 11 for showing an internal arrangement of the ink jet printer; 
     FIG. 13 is an enlarged cross-sectional view showing details of a left side portion of FIG. 12; 
     FIG. 14 an enlarged cross-sectional view showing the view of FIG. 13 after a print cartridge has been lifted slightly upward; and 
     FIG. 15 is an enlarged cross-sectional view showing the view of FIG. 14 after the print cartridge is separated from a printer body of the printer of FIG.  10 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An ink jet printer  1  and a printer cartridge  3  assembled thereinto according to a first embodiment of the present invention will be described with reference to FIGS. 1 through 7. Throughout the specification, terms such as left, right, up, down, front, and rear for describing direction are used to describe locations of components in the ink jet printer  1  while the ink jet printer  1  is in the orientation in which it is intended to be used. 
     FIG. 1 shows a table top type ink jet printer  1  including a box-shaped printer body  2 , the print cartridge  3 , and an ink cartridge  40  housing an ink package  30  and that is detachably mountable on the print cartridge  3 . The print cartridge  3  is detachably mountable on the printer body  2  and is provided with a print head  21 . 
     The printer body  2  includes a main frame  12  having a front wall, a rear wall, a pair of side walls, a top wall and a bottom wall. A laterally extending discharge port  13  is formed in the front wall of the main frame  12  for discharging printed-on print sheets from the printer body  2 , and a laterally extending head movement groove  14  is formed in the top wall. Although not shown in the drawings, a sheet supply port through which unprinted print sheets are inserted into the printer body  2  is formed at the rear wall and at a position opposing the sheet discharge port  13 . The print cartridge  3  includes a cartridge frame  26 . The main frame  12 , the discharge port  13 , the head movement groove  14 , and the cartridge frame  26  are indicated by two-dot chain lines in FIG.  1 . The movement direction for mounting the ink cartridge  40  onto the print cartridge  3  is indicated by an arrow X in FIG.  1 . 
     A transport roller  4  for transporting a print sheet through the ink jet printer  1  is rotatably supported on the main frame  12  of the printer body  2 . A follower gear  4   a  is attached to the left end of the transport roller  4 . The follower gear  4   a  is meshingly engaged with a drive gear  5   a  of a line feed motor  5  disposed adjacent to the follower gear  4   a . With this configuration, rotation of the line feed motor  5  rotates the drive gear  5   a  and consequently the transport roller  4  so that the print sheet can be is transported. 
     A guide bar  17  is disposed in the main frame  12  in parallel with the transport roller  4 . It should be noted that the end portions of the guide bar  17  are not shown in FIG. 1. A carriage  6  on which the print head  21  of the print cartridge  3  is mounted, is itself mounted on the guide bar  17  via holes formed through the carriage  6 . With this configuration, the carriage  6  can slidingly move along the guide bar  17  in a direction perpendicular to the transport direction of the print sheet. 
     A mechanism for driving the carriage  6  includes a carriage return (CR) motor  7  disposed at the right end of the main frame  12 , a drive pulley  7   a  driven by rotation of the CR motor  7 , a follower pulley  7   b  provided at the left end of the main frame  12 , and a belt  7   c  spanning between the drive pulley  7   a  and the follower pulley  7   b  and connected to the carriage  6 . With this configuration, rotation of the CR motor  7  rotates the drive pulley  7   a  so that the belt  7   c  reciprocally transports the carriage  6  in the lengthwise direction of the printer body  2 , that is, in the direction parallel with the axes of the guide bar  17  and the transport roller  4 . As a result, the print head  21  mounted on the carriage  6  is also reciprocally transported in the lengthwise direction of the printer body  2  so that printing can be performed on the print sheet. It should be noted that a portion of the belt  7   c  is omitted from FIG. 1 to facilitate understanding of the transport roller  4  and the guide bar  17 . 
     Although the print head  21  and the ink cartridge  40  will be described in further detail later, it will be noted here that the print head  21  is mounted on the carriage  6 , but the ink cartridge  40  is mounted at the left end of the cartridge frame  26  and not on the carriage  6 . With this configuration, the load imparted on the carriage  6  when the carriage  6  is driven to move is less than if the ink cartridge  40  were also mounted on the carriage  6 . For this reason, the ink jet printer  1  of the first embodiment requires less power to drive the carriage  6  than does a conventional printer wherein the ink cartridge is also mounted on the carriage. As a result, the load such as start-up torque on the CR motor  7  is reduced. Also, through-up period of the CR motor  7  can be reduced. These reductions in the load and through-up period of the CR motor  7  translate into a reduction in the amount of power consumed by the CR motor  7 . 
     Because the load applied on the carriage  6  is reduced, a small motor with only a small amount of torque can be used as the CR motor  7 . Because the CR motor  7  can be a small motor, the size of the printer body  2  of the ink jet printer  1  can be made more compact. Because the printer body  2  can be made more compact, the ink jet printer  1  is more portable and can be easily carried with and used with a laptop computer or a personal digital assistant (PDA). 
     Because only the print head  21  is mounted on the carriage  6 , less drive force is required to drive the carriage  6 . As a result, the CR motor  7  can drive the carriage  6  stably at a high speed. That is to say, because only the print head  21  is mounted on the carriage  6 , the weight applied on the carriage  6  will not change as ink is consumed. This differs from the conventional situation wherein the ink cartridge is also mounted on the carriage. Accordingly, the ink jet printer  1  according to the first embodiment does not require a control means for controlling fluctuation in moving speed of the carriage  6  because moving speed of the carriage  6  will not change with consumption of ink. Therefore, overall cost of the ink jet printer  1  will be reduced by the cost of the unneeded control means. 
     The print head  21  has nozzles  21   a  including nozzle openings  21   b  (FIG.  2 ). A suction cap  8  and a suction pump  9  are disposed at the left end of the printer body  2 . The suction cap  8  and the suction pump  9  are for performing purging processes for recovering the print head  21  to a proper ink ejecting condition. That is, the suction cap  8  is for sealing closed the nozzle openings  21   b . The suction pump  9  is for sucking ink from the nozzle openings  21   b , once the nozzle openings  21   b  are sealed closed by the suction cap  8 . When these purge processes are to be performed, the CR motor  7  moves the carriage  6  mounted with the print head  21  to the left side of the ink jet printer  1 , whereupon the suction cap  8  seals closed the nozzle openings  21   b  of the print head  21 . When the suction pump  9  is driven while the suction cap  8  covers the nozzle openings  21   b  in this manner, dried ink and bubbles are sucked from the nozzle openings  21   b  so that the nozzle openings  21   b  of the nozzles  21   a  are recovered to a sufficient ink ejection condition. It should be noted that purge processes are performed when dried ink or the like clogs the nozzle openings  21   b , which prevents the surface of the liquid ink filling the nozzle openings  21   b  from forming into a concave shaped meniscus M shown in FIG.  2 . 
     A protective cap  10  for covering the nozzles  21   a  of the print head  21  is disposed at the left side of the suction cap  8 . The protective cap  10  covers the nozzles  21   a  to prevent ink in the nozzles  21   a  from evaporating and drying out when printing is not performed using the print head  21 , that is, when the carriage  6  is in a stand-by condition. 
     A control circuit board  11  mounted with a central processing unit (CPU)  11   a  and the like is disposed within the lower portion of the printer body  2 . The CPU  11   a  is for controlling the ink jet printer  1  according to control programs with respect to an operation of the ink jet printer  1 . A PC card  15  is connected to the control circuit board  11  via a connection cable  16 . The PC card  15  is inserted into a PC card slot of a personal computer (not shown in the drawings) to enable input of print data and the like from the personal computer to the ink jet printer  1 . 
     It should be noted that by inserting the PC card  15  into the PC card slot of the personal computer, power of the personal computer is also supplied to the ink jet printer  1  over the connection cable  16  and the PC card  15 . Accordingly, there is no need to connect the ink jet printer  1  to an AC power source when the ink jet printer  1  is used to print. For example, the ink jet printer  1  can be used outside of the office or outdoors by using the power source of a laptop personal computer. 
     The printer  1  according to the present embodiment is designed so that the heavier components, such as the line feed motor  5  and the CR motor  7 , are disposed in the printer body  2 . As a result, the central gravity of the ink jet printer  1  is located in the printer body  2 . Because the printer body  2  is disposed in the lower portion of the ink jet printer  1 , the ink jet printer  1  is more stably set in place. With this configuration, the ink jet printer  1  can be prevented from falling over because of vibration caused by the movement of the carriage  6  or the transport roller  4 , for example. Further, the printer body  2  can be prevented from toppling over when the print cartridge  3  is exchanged. 
     A connector  18  is disposed in the upper surface of the top wall of the main frame  12 . The connector  18  is adapted for supplying power for driving the print head and electrical signals based on image data to the print head  21  of the print cartridge  3 . Although not shown in the drawings, the connector  18  is connected to the control circuit board  11  disposed on the lower portion of the printer body  2 . A plurality of connection holes  18   a  are formed in the upper surface of the connector  18 . Each connector hole  18   a  is formed for receiving a particular one of a plurality of connection pins (not shown), which are provided on the lower surface of an attachment member  25  disposed on the print cartridge  3 . 
     The rectangular shaped head movement groove  14  is provided in the upper wall of the main frame  12  so that when the print cartridge  3  is attached to the printer body  2 , the print head  21  can be mounted in the carriage  6  through the head movement groove  14 . 
     The print cartridge  3  is configured to be attachable to and detachable from the top wall of the printer body  2 . The print cartridge  3  has a box shaped cartridge frame  26 , which houses the print head  21  and other components, such as an ink extraction needle  22 , an ink supply tube  23 , an attachment member  24  and the attachment member  25 . The attachment members  24 ,  25  are for connecting the ink extraction needle  22  and the print head  2  to the ink supply tube  23 . 
     The print head  21  is installed so as to be capable of reciprocal movement in a main scanning direction, that is, in the lengthwise direction of the print cartridge  3 . The print cartridge  3  supports the print head  21  along all or a portion of its reciprocal movement region within the print cartridge  3 . This configuration is achieved by providing protrusion members that protrude from side or upper surfaces of the print head  21  and by also providing retaining members on the inner side walls of the print cartridge  3  for retaining these protrusion members. The retaining members are provided in the print cartridge  3  along a portion of the reciprocal movement region of the print head  21 . Alternatively, the retaining members can be provided in the print cartridge  3  so as to span the entire reciprocal moving region of the print head  21 . 
     By configuring the print cartridge  3  in this manner, the print head  21  is held by the retaining members at a position within the reciprocal moving region in the print cartridge  3 . Therefore, when the print cartridge  3  is removed from the printer body  2 , the retaining members lift up the protrusion members. Therefore, the print head  21  can be removed from the printer body  2  with the state that the print cartridge  3  holds the print head  21 . Further, the print head  21  can be mounted onto the carriage  6  by fitting the print head  21  into the carriage  6  when the print cartridge  3  is mounted in the printer body  2 . 
     In order t o accurately mount the print head  21  to and detach the print head  21  from the carriage  6  when attaching the print cartridge  3  to and detaching the print cartridge  3  from the printer body  2 , the CPU  11   a , for example, must control the stop of the carriage  6  always at a predetermined stop position upon completion of printing operations. This is particularly the case when the retaining members are provided in the print cartridge  3  along a portion of the reciprocal movement region of the print head  21 . In this case, in order to accurately attach the print head  21  to and detach the print head  21  from the carriage  6  by attaching the print cartridge  3  to and detaching the print cartridge  3  from the printer body  2 , the CPU  11   a  and the like must control to stop the carriage  6  at a position directly beneath the retaining members of the print cartridge  3  at the end of printing operations. 
     It should be noted that the protrusion members, the retaining members, and other means for mounting the print head  21  to the carriage  6 , that is, when the print cartridge  3  is mounted onto the printer body  2 , configure a print head mounting means and a print head detachment means of the present invention. An exemplary embodiment of this configuration will be described later while referring to FIGS. 10 through 15. Even though, FIGS. 10 through 15 pertain to a fourth embodiment, the print head mount-assist means and print head detachment means shown in FIGS. 10 though  15  are also provided in the first through third embodiments. 
     The print head includes the nozzles  21   a  formed from piezoelectric elements. As shown in FIG. 2, the nozzles  21   a  include the plurality of nozzle openings  21   b . Each nozzle opening  21   b  is filled with ink supplied from the ink package  30  housed in the ink cartridge  40 . When a voltage is applied to the nozzles  21   a , the nozzles  21   a  deform to an extent proportional to the applied voltage so that the volume of each nozzle opening  21   b  can be selectively reduced. When the volume of one of the nozzle openings  21   b  is reduced, the ink filling the particular nozzle opening  21   b  is ejected toward the print sheet PP so that printing is performed. It should be noted that the printing method used to drive the print head  21 , which is provided with the nozzles  21   a  made from piezoelectric elements, will be referred to as a piezoelectric drive method hereinafter in the present specification. 
     Piezoelectric elements require less power to eject ink droplets than do the ink ejection means of a thermal jet (bubble jet) method. Therefore the piezoelectric drive method consumes less power than does the thermal jet method. The ink jet printer  1  saves power because it uses the piezoelectric drive method and also because the CR motor  7  is burdened with a smaller load as described previously. These power savings enable reduction of power consumption by the ink jet printer  1 . Also, the PC card  15  can be used to supply power to the ink jet printer  1  from the power source, such as a small dry cell battery or a secondary cell battery, of a laptop type personal computer. 
     The nozzle openings  21   b  of the print head  21  are spaced away from each other by a pitch of approximately 180 dots per inch (dpi). The carriage  6  mounted with the print head  21  can print monochrome characters and the like at the resolution of 180 dpi by reciprocally moving in the lengthwise direction of the printer body  2  as viewed in FIG.  1 . 
     When the ink filling the nozzle openings  21   b  has a concave shaped meniscus M at the lower surface of the ink, proper ink ejection can be achieved so that clear printing results can be obtained. Concave menisci M can be formed in the nozzle openings  21   b  by maintaining negative pressure in the ink filling the nozzle openings  21   b . For example, concave menisci M can be formed at the ink surface in the nozzle openings  21   b  by maintaining the ink supply pressure in the print head  21  to within an operating pressure range of from about not less than 0 mm Aq (water column) to about not more than about −300 mmAq (water column) with respect to atmospheric pressure. It should be noted that the method of maintaining a negative pressure in the ink supply pressure will be later explained while explaining the ink package  30 . 
     As shown in FIG. 1, one end of the ink supply tube  23  is connected to the print head  21  by the attachment member  24 , which is provided on the upper portion of the print head  21 , and the other end of the ink supply tube  23  is attached to the ink extraction needle  22  through the attachment member  25 . The ink extraction needle  22  is for extracting ink from the ink package  30  housed within the ink cartridge  40 . The ink extracted by the ink extraction needle  22  is supplied to the print head  21  via the ink supply tube  23  and the attachment members  24 ,  25 . 
     The ink supply tube  23  is generally linear in shape but curves greatly near the attachment member  24 . For this reason, the ink supply tube  23  is formed shorter than conventional tubes, and without a plurality of bends in the tube in the manner of conventional ink supply tubes. Because the ink supply tube  23  is shorter than conventional ink supply tubes and without any discontinuous bent portions, resistance to flow of ink flowing through the ink supply tube  23  to the print head  21  can be reduced. Also, the amount of ink sucked out during purge operations, which also sucks ink out of the ink tube in addition to out of the print head, is also reduced. Further, because the short ink supply tube  23  can be used, manufacturing costs can be reduced. 
     Although not shown in the drawings, a harness and the like is formed integrally with the ink supply tube  23  and is connected between the print head  21  and the attachment member  25 . The harness is for supplying power for driving the print head  21  and is for supplying electric signals based on image data to the print head  21 . 
     Although not shown in the drawings, a plurality of connection pins are provided to the lower surface of the attachment member  25 . Each connection pin is formed so as to be insertable into the corresponding one of the plurality of connection holes  18   a  formed in the upper surface of the connector  18 . Each connection pin of the attachment member  25  is inserted into the corresponding connection hole  18   a  of the connector  18  when the print cartridge  3  is mounted onto the printer body  2 . As a result, the print head  21  and the control circuit board  11  are connected via the attachment member  24 , the ink supply tube  23 , the attachment member  25 , and the connector  18 . Therefore, power for driving the print head and electric signals based on image data can be supplied from the control circuit board  11  to the print head  21 . 
     The print head  21 , the ink extraction needle  22 , the ink supply tube  23 , and the attachment members  24 ,  25  will be referred to collectively as the print head  21  and the like, hereinafter. The print head  21  and the like are connected and adhered using adhesive or fuse-bonding. That is, no seal members such as detachable O-rings are used in the print cartridge  3 . Therefore, when breakdowns or other problems occur at positions anywhere in the print cartridge  3 , the problem can be resolved by disposing of the print cartridge  3  and replacing it with a new print cartridge  3  of the same type. For this reason, there is no need to exchange separately each part of the print cartridge  3  so that maintenance of the ink jet printer  1  is easily performed. Because there is no need to solely exchange the print head  21  separately, there is no danger that the user will accidentally touch the nozzles  21   a  of the print head  21  and stain his or her hand. 
     Because sections of the print head  21  and the like are attached or connected by fuse-bonding or by adhering with adhesive, the connection portions and the attachment portions of the print head  21  and the like can be maintained in an air tight condition. Accordingly, air and the like will not enter into the print head  21 , and, ink will not leak out of the print head  21  through the adhering or bonding part. 
     The ink extraction needle  22  is formed in a hollow needle shape and is formed with an ink extraction port  22 a in its tip. With this configuration, the ink extraction needle  22  can be inserted into an ink holding portion  31  of the ink package  30  to extract ink from the ink holding portion  31  through the ink extraction port  22   a . The ink extraction needle  22  is formed from a corrosion resistant ceramic or metal, such as stainless steel. 
     This ink extraction operation will described in more detail here. First, the ink cartridge  40  housing the ink package  30  is inserted into the print cartridge  3  and slid in the direction indicated by an arrow X in FIG.  1 . This sliding motion inserts the ink extraction needle  22  into the ink holding portion  31  through a through hole  42  shown in FIG.  3 . Once the ink cartridge  40  is disposed adjacent to the attachment member  25  as indicated in two-dot chain line in FIG. 1, ink within the ink package  30  flows into the hollow space of the ink extraction needle  22  through the ink extraction port  22   a . Ink that flows into the ink extraction needle  22  further flows into the ink supply tube  23  through the attachment member  25 . Further, ink is supplied to the ink head  21  through the attachment member  24 . An explanation of the ink package  30  will be provided later along with description of an outer diameter d of the ink extraction needle  22 . 
     The print cartridge  3  is designed to be light weight. That is, the print cartridge  3  is installed with components, such as the print head  21  and the ink supply tube  23 , that are lighter than components, such as the CR motor  7 , the line feed motor  5 , and the guide bar  17 , which are installed in the printer body  2 . For this reason, the print cartridge  3  is easily lifted up and carried around when exchanging the print cartridge  3 . Also, the print cartridge  3  will not cause injury to hands or feet, for example, if accidentally dropped. 
     Next, the ink package  30  and the ink cartridge  40  housed therein will be described in detail while referring to FIGS. 3 to  6 . As shown in FIG. 3, the ink cartridge  40  is formed in a substantially box shape and is detachable from the print cartridge  3 . The ink cartridge  40  includes a cartridge body  41 , a lid  43 , and the ink package  30 . The cartridge body  41  is opened at its upper surface to enable insertion of the ink package  30 . The lid  43  is provided for covering the upper open end of the cartridge body  41  after the ink package  30  has been inserted therein. After the lid  43  is placed over the upper open end of the cartridge body  41 , the lid  43  is fuse-bonded to the cartridge body  41  to attach it to cartridge body  41 . Instead of fuse-bonding the lid  43  to the cartridge body  41 , the lid  43  can be attached to the cartridge body  41  by providing attachment members to both the cartridge body  41  and the lid  43 . 
     The through hole  42  is opened to the side wall of the cartridge body  41 . As described above, the ink extraction needle  22  is inserted into the ink cartridge  40  through the through hole  42 . By inserting the ink extraction needle  22  into the through hole  42 , the ink extraction needle  22  can be inserted into an indentation portion  32  of the ink package  30  housed in the ink cartridge  40 . Providing a seal member, such as packing formed, for example, from NBR to the through hole  42  is helpful in preventing ink from leaking out of the ink cartridge  40  when the ink cartridge  40  is removed from the print cartridge  3  and the ink extraction needle  22  is removed from the ink package  30 . It should be noted that to fit the ink package  30  within the ink cartridge  40 , heat seal portions  33 ,  34 ,  35  of the ink package  30  can be either folded and bent while the ink package  30  is being inserted into the ink cartridge or cut off before the ink package  30  is inserted into the cartridge body  41 . 
     The ink package  30  is formed into a substantially rectangular bag shape from a laminated film formed from a plurality of, for example, ten polyethylene resin film sheets. The ink holding portion  31 , which is filled with ink for printing, is formed in the approximate center of the ink package  30 . The left edge of the ink holding portion  31  is defined by the indentation portion  32 , which has an indented shape as viewed from above and which is where the ink extraction needle  22  is inserted. The other three edges are defined by the heat seal portions  33 ,  34 ,  35 . With this configuration, the indentation portion  32  is supported at both ends by heat-seal portions  33 ,  34 . Therefore the ink extraction needle  22  can easily penetrate into the ink holding portion  31  when the ink extraction needle  22  is inserted into the indentation portion  32 . 
     Here, a method for manufacturing the ink package  30  will be described. First, the rectangular shaped laminated film is folded in half so that the two halves overlap each other. The overlapping edges opposite the folded portion of the laminated film member are heat-sealed together to form the heat seal portion  35 . At this point, the laminated film is in a hollow tubular shape. Next, the overlapping edges at one of the open ends of the hollow tube are heat-sealed together to form the heat-seal portion  33 . At this point, the laminated film is in the shape of a bag, with the end corresponding to the fused portion  34  still open. Next, ink is introduced into the bag through this open portion. After ink is introduced into the bag, the open end of the bag, which is positioned opposite of the fused portion  33 , is fused closed to form the fused portion  34  and the indentation portion  32  at one edge of the ink holding portion  31 . 
     At this point, the ink package  30 , wherein ink is sealed in the ink holding portion  31 , is positioned at one end of the folded halves of the rectangular shaped lamination film. After the ink package  30  is formed, the heat seal portion  34  is cut from the folded halves, so that the ink package  30  can be separated from the folded halves. This completes production of the ink package  30 . It should be noted that the ink holding portion  31  is maintained at a positive pressure while ink is being introduced into the bag. This prevents air and the like from being introduced into the ink holding portion  31  of new and unused ink packages  30 . 
     Next, a manner for maintaining ink supply pressure of ink supplied to the print head  21  will be described. The ink package  30  is formed from the laminated film member as described above. Therefore, when the ink package  30  is penetrated with the ink extraction needle  22 , the outer peripheral surface of the inserted ink extraction needle  22  is in a sealed condition with the laminated film member of the ink package  30 . Accordingly, ink can be prevented from leaking out of the ink holding portion  31 . Also, air can be prevented from entering into the ink holding portion  31 , in particular while ink is being extracted through the ink extraction needle  22  during consumption of ink. Said differently, ink extracted from the ink holding portion  31  is not replaced by air and the like in amounts that correspond to the amount of ink consumed. Therefore, the internal pressure P of the ink holding portion  31  is maintained in a negative pressure. 
     Further, strengthening the rigidity of the laminated film member forming the ink package  30  increases a dimensional stability or shape-restoring property of the laminated film member, thereby preventing the ink holding portion  31  of the ink package  30  from changing its shape. Therefore, ink can be extracted from the ink holding portion  31  through the ink extraction needle  22  without the ink holding portion  31  being compressed by atmospheric pressure and the like. As a result, the internal pressure P of the ink holding portion  31  can be maintained at a negative pressure so that when the ink extracted from the ink extraction needle  22  is supplied to the print head  21 , the ink supply pressure of ink can be maintained at a negative pressure. 
     Next, an explanation for a method of strengthening the rigidity of the laminated film member will be provided while referring to FIGS. 4 through 6. FIG. 4 is a graph comparing ink packages  30  in which thickness w of the laminated structure film materials is different, FIG. 5 is a graph comparing ink packages  30  in which the ratio h of the longitudinal direction length A to the lateral direction length B (aspect ratio) of the ink sealing portion  31  is different, and FIG. 6 comparing ink packages  30  in which either one of the longitudinal direction length A or the lateral direction length B of the ink sealing portion  31  is different. In FIGS. 4-6, the horizontal axes  51 ,  61  and  71  represent the consumed amount V of the ink sealed inside the ink sealing portion, and the vertical axes  52 ,  62  and  72  represent the inner pressure P inside the ink holding portion  31 . 
     Regarding the thickness w of the laminated structure film materials in the respective ink packages  30  shown in FIG. 4, the curves  53  (alternating long and short dashed line),  54  (alternating long and two short dashed line),  55  (solid line),  56  (dotted line) and  57  (broken line) correspond to 300 ìm, 160 ìm, 100 ìm, 80 ìm and 30 ìm, respectively. When the respective curves  53 - 57  are compared, with increase in the amount V of consumed ink, the inner pressure P drastically decreased in the order of curves  53 ,  54 ,  55 ,  56  and  57 . In other words, as the thickness w of the laminated structure film material increases, the rigidity of the film material forming the ink sealing portion  31  increases. With these thickness, the shape stability of the laminated structure film material becomes significantly large, and a change in the shape of the ink sealing portion  31  is restrained. Thus, in the present embodiment, on the basis of the result from FIG. 4, the thickness w of the laminated structure film material is set from approximately 30 ìm to approximately 300 ìm, in order to set the ink supplying pressure, that is, the inner pressure P inside the ink sealing portion  31 ,  25  within the print head workable pressure ranging from approximately −100 mmAq to approximately 0 mmAq. 
     Since in the present embodiment the thickness w of the laminated structure film material is set approximately 30 ìm to approximately 300 ìm, in the aforementioned manner, an excessive increase in heating time and an excessive rise in heating temperature are prevented in the fuse-bonding step for forming the heat-sealed portions  33 ,  34  and  35  of the ink package  30 . Thus, the cost for making the ink package  30  can be reduced. Further, the ink extraction needle  22  can be easily inserted into the ink package  30  with little resistance. 
     Regarding the aspect ratio h of the ink holding portion  31  of the respective ink packages  30  shown in FIG. 5, the curves  63  (alternating long and two short dashed line),  64  (solid line) and  65  (dotted line) correspond to “1”, “1.5” and “2”, respectively. When the respective curves  63 - 65  in FIG. 5 are compared, with an increase in the amount V of consumed ink, the inner pressure P drastically decreased in the order of curves  63 ,  64  and  65 . In other words, as the aspect ratio h of the ink sealing portion  31  decreases, the rigidity of the laminated structure film material  10  forming the ink holding portion  31  increases Therefore, with these ratio, the shape stability of the laminated structure film material becomes significantly large, and a change in the shape of the ink holding portion  31  is prevented. Thus, in the present embodiment, on the basis of the result from FIG. 5, the aspect ratio h of the ink holding portion  31  is set about from “1” to “2”, that is, the length in the longitudinal direction A (the length in the lateral direction) of the ink holding portion  31  is set to about from 1 to 2 times as long as the lateral direction length B (the length in the longitudinal direction A), in order to set the ink supplying pressure, that is, the inner pressure P in the ink sealing portion  31  within the print head workable pressure ranging from approximately −100 mmAq to approximately 0 mmAq. It should be noted that in FIG. 5, “A:B=2:1” provided the result the same as the result of “A:B=1:2”. In other words, in the lower limit, the one side and another side perpendicular to the one side has the same length, and in the upper limit, the one side has a length twice as long as the other side. 
     Regarding the length in the longitudinal direction A (the length in the lateral direction B) of the holding portion  31  of the respective ink packages  30  shown in FIG. 6, the curves  73  (alternating long and short dashed line),  74  (alternating long and two short dashed line),  75  (solid line), and  76  (dotted line) correspond to 30 mm, 50 mm 70 mm and 100 mm, respectively. When the respective curves  73 - 76  in FIG.6 are compared, with an increase in the amount V of consumed ink, the inner pressure P drastically decreased in the order of curves  73 ,  74 ,  75  and  76 . In other words, as the length in the longitudinal direction A (the length in the lateral direction B) of the ink holding portion  31  decreases, the rigidity of the ink holding portion  31  increased. Therefore, the shape stability of the laminated structure  30  film material becomes significantly large, and a change in the shape of the ink sealing portion  31  is prevented. Thus, in the present embodiment, on the basis of the result from FIG. 6, the longitudinal direction length A (the lateral direction length) of the ink holding portion  31  is set about 100 or less mm, in order to set the ink supplying  17  pressure, that is, the inner pressure P in the ink sealing portion  31  within the print head workable pressure ranging from approximately −100 mmAq to approximately 0 mmAq. It should be noted that this length is available for both the side A and side B. 
     Next, while referring to FIG. 7, an explanation will be provided for the relationship between diameter d of the ink extraction needle  22  and the seal formed between the ink package  30  and the ink extraction needle  22 . In the chart of FIG. 7, the seal formed between the ink package  30  and the ink extraction needle  22  is represented as a pressing force F. The pressing force F was determined for each different diameter ink extraction needle  22  by inserting each ink extraction needle  22  into an ink package  30 , and measuring the pressing force F applied to the ink package  30  in its thickness directions at the time when the ink extraction needle  22  was pushed out of ink package  30 . The ink package  30  used during these experiments was formed from a laminated film member having a thickness of about 100 μm. 
     As shown in FIG. 7, as the outer diameter d of the ink extracting member  22  increased, the pressing power F that the ink extraction member  22  is pulled out from the ink package  30  increased. Preferably, the pressing power F is approximately 100 g or less. On the basis of this result, the outer diameter d of the ink extracting member  22  is set to about 5 mm or less, in order to maintain the intimate contact power of the outer surface of the ink extraction member  22  stuck into the ink package  30  with the laminated structure film material of the ink package  30 . 
     The ink supply pressure can be adjusted and maintained at a negative pressure by supplying ink to the print head  21  using this ink package  30  and the ink extraction needle  22  formed as described above. Therefore, there is no need to provide an ink supply pressure adjustment means, such as an ink supply pump and a sub-tank disposed below the print head  21  for generating a negative ink supply pressure. As a result, the ink jet printer  1  can be produced with fewer components so that overall costs of making the ink jet printer  1  can be reduced. Because no ink supply pump and the like is needed, the ink jet printer  1  can be driven without consuming as much power as conventional printers. The details of the lamination film and the ink package  30  is described, for example, in a copending U.S. patent application Ser. No. 09/132,486 filed Aug. 11, 1998, the disclosure of which is hereby incorporated by reference. 
     Next, while referring to FIGS. 1 to  3 , a method for assembling the ink jet printer  1  will be described. First, the ink package  30  shown in FIG. 3 is inserted into the cartridge body  41  by either bending or partly cutting the heat-seal portions  33 ,  34 ,  35  of the ink package  30 . After the ink package  30  is inserted into the cartridge body  41 , the lid  43  is placed on the top of the cartridge body  41 . Then the ink package  30  is sealed within the ink cartridge  40  by fuse-bonding the lid  43  to the cartridge body  41 . 
     Next, the through hole  42  of the ink cartridge  40  is aligned with the ink extraction needle  22 . By sliding the ink cartridge  40  in the direction X, the ink extraction needle  22  is inserted into the through hole  42  of the ink cartridge  40 . After the ink extraction needle  22  is inserted into the through hole  42 , the ink extraction needle  22  easily pierces the indentation portion  32  of the ink holding portion  31  of the ink package  30  housed in the ink cartridge  40 . Because the indentation portion  32  of the ink package  30  is supported at its two sides by the heat-seal portions  33 ,  34 , the ink holding portion  31  can be prevented from deforming when pressed by the ink extraction needle  22  and when the ink extraction needle  22  pierces the indentation portion  32 . 
     When the ink cartridge  40  is further slid in the direction X, the ink cartridge  40  will be installed in the left-hand portion of the print cartridge  3  in the position indicated by the two dot chain line at the left-hand side of the FIG.  1 . This completes operations for mounting the ink cartridge  40  into the print cartridge  3 . In the mounted condition, the ink cartridge  40  will tilt downward toward the attachment member  25 , that is, toward the right center as viewed in FIG.  1 . Said differently, the ink cartridge  40  will be disposed so that it tilts downward from the left end of the ink cartridge  40  to the right end of the ink cartridge  40 . With this orientation, any air and the like mixed in the ink when filling the ink package  30  during manufacture of the ink package  30  will gather at the upper left end of the ink cartridge  40 . Therefore, air can be prevented from entering the ink extraction needle  22 . It is desirable that when the ink cartridge  40  is in its mounted condition in the ink package  30 , it should have a slanting angle of about 0 to 10 degrees or optimally about 0 to 3 degrees. Further, because the laminated film member forming the ink package  30  is in sufficient sealing contact with the outer peripheral surface of the ink extraction needle  22 , air can be prevented from entering the ink package  30  and ink can be prevented from leaking out of the ink package  30 . 
     When the ink extraction needle  22  pierces the ink holding portion  31  of the ink package  30 , ink is extracted from the ink holding portion  31  through the ink extraction port  22   a . The ink flows through the attachment member  25 , the ink supply tube  23 , and the attachment member  24 , whereupon it is supplied to the print head  21 . Because the laminated film forming the ink package  30  has strength and rigidity sufficient to enable the ink package  30  to recover its shape, change in the shape of the ink holding portion  31  of the ink package ink package  30  is restricted. Accordingly, the internal pressure P of the ink holding portion  31  can be maintained in a negative pressure while ink is being extracted through the ink extraction needle  22 . That is, the ink holding portion  31  will not be squeezed by atmospheric pressure and the like so that the ink supply pressure can be maintained at negative pressure when ink extracted by the ink extraction needle  22  is supplied to the print head  21 . As a result, a concave meniscus M can be formed in ink filling each of the nozzle ports  21   b , thereby enabling the print head  21  to properly eject ink to produce good clean printing results. 
     Next, the print cartridge  3  is mounted onto the printer body  2  while inserting the print head  21  of the print cartridge  3  into the carriage  6  of the printer body  2 . At this time, the print head  21  can be easily mounted of the carriage  6  without any labor by merely mounting the print cartridge  3  onto the printer body  2  using a print head mounting means to be described later. After the print cartridge  3  has been mounted, the PC card  15  of the ink jet printer  1  is inserted into the PC slot of a personal computer to electrically connect the ink jet printer  1  with the personal computer. In this condition, power is supplied from the personal computer to the ink jet printer. Also print data and the like can be transmitted between the personal computer and the ink jet printer  1 . 
     Printing is performed on the print sheet PP when the ink jet printer  1  receives transmission of print data from the personal computer. In this case, when an unused print sheet PP is inserted into the sheet supply port (not shown) of the ink jet printer  1 , the transport roller  4  transports the print sheet PP along the transport pathway under the print head  21 , which is mounted on the carriage  6 . When the transported print sheet PP passes through the transport pathway under the print head  21 , the print head  21  ejects ink from the nozzle ports  21   b  to print characters and the like on the print sheet PP. This printed print sheet PP is then discharged through the discharge port  13 . 
     Next, while referring to FIG. 8, an ink jet printer  100  having a print cartridge  103  according to a second embodiment of the present invention will be explained. The print cartridge  103  of the ink jet printer  100  is a modification of the print cartridge  3  of the first embodiment. 
     The print cartridge  103  of the ink jet printer  100  includes a print head  121 , which is similar to the print head  21 . The print heads  21  and  121  are positioned side by side in the scanning direction of the carriage. The print head  121  includes a row of nozzles  121   a  at its lower surface. In a manner similar to the print head  21 , A nozzle opening is formed at the lower end of each nozzle of the row of nozzles  121   a . The nozzle opening are disposed at a pitch corresponding to 180 dpi. The rows of nozzles  21   a ,  121   a  are shifted with respect to each other in the sheet feeding direction by a half pitch distance, that is, by a distance corresponding to a pitch of 360 dpi. When both the print heads  21 ,  121  are used for printing, printing can be performed at a resolution of 360 dpi by reciprocally moving the carriage  6 , on which both of the print heads  21 ,  121  are mounted, in the lengthwise direction of the printer body  2 . Accordingly, the ink jet printer  100  according to the second embodiment can perform higher resolution printing within a shortened period in comparison with the first embodiment. 
     The ink jet printer  100  of the second embodiment uses the same printer body  2  as the ink jet printer  1  of the first embodiment. Therefore, the ink jet printer  100  of the second embodiment can be used as part of the ink jet printer  1  by merely replacing the print cartridge  3  of the first embodiment with print cartridge  103  of the second embodiment. 
     Next, an ink jet printer  200  according to a third embodiment of the present invention will be described while referring to FIG.  9 . The ink jet printer  200  includes a print cartridge  203  and ink cartridges  240 , which are modifications of the print cartridge  3  and the ink cartridge  40  of the first embodiment. 
     The print cartridge  203  of the ink jet printer  200  is mounted with four ink cartridges  240  and two print heads  221   a ,  222   a . Each ink cartridge  240  houses an ink package  30 . In the present embodiment, each ink package  30  is filled with one of four different colored inks, that is, black ink, yellow ink, cyan ink, and magenta ink from top to bottom as viewed in FIG.  9 . Although not show in the drawings, a plurality of nozzles are provided to the print heads  221 ,  222 . The four different colored inks from the ink packages  30  are supplied to the print heads  221 ,  222  and ejected from the nozzles to print in full color on a print sheet PP. 
     More black ink than other colored inks is consumed during printing. For this reason, the ink package  30  filled with black ink needs to be replaced more frequently than the other ink packages  30 . Therefore, the ink cartridge  40  housing the ink package  30  filled with black ink is mounted above the other ink cartridges  40  to facilitate operations for replacing the ink cartridge  40  filled with black ink. Also, with this configuration exchange operations can b e performed without mistaking the position for mounting the black ink cartridge  40 . 
     The ink jet printer  200  has the same printer body  2  as the ink jet printers  1 ,  100  of the first and second embodiments. Therefore, by exchanging the print cartridge  203  with the print cartridges  3 ,  103  of the first and second embodiments, the ink jet printer  200  can be converted into either of the ink jet printers  1 ,  100 . In other words, by merely exchanging the print cartridges  3 ,  103 ,  203 , the user can easily switch between monochrome printing using the print cartridges  3 ,  103  and full color printing using the print cartridge  203 . Further, because the user exchanges the print cartridges  3 ,  103 ,  203  to switch between monochrome printing and full color printing, different colored inks within the ink supply pathway, that is, the ink within the print head  21 , the ink extraction needle  22 , the ink supply tube  23 , and the attachment members  24 ,  25 , can be prevented from mixing together. 
     The print cartridge  203  includes four ink supply tubes  23  for connecting the ink cartridges  40  to the print heads  221   a ,  222   a . The ink supply tubes  23  are aligned vertically one on top of the other as shown in FIG.  9 . This configuration prevents the ink supply tubes  23  from bending downward, that is, as viewed in FIG. 9, under their self-weight. Accordingly, fluctuation in ink supply pressure and damage to the ink supply tubes  23  resulting from the buckling of the ink supply tubes  23  when they bend can be prevented. 
     Four attachment members  125   a  to  125   d  are provided, one for each of the four ink cartridges  40 . As shown in FIG. 9, each attachment member  125   a  to  125   d  has an ink extraction needle  22  attached thereto at a different position in the front-to-rear direction of the printer  1 . Although not shown in the drawings, the through holes  42  of the ink cartridges  40  are similarly aligned in correspondence with positions of the ink extraction needle  22 . As long as the ink cartridges  40  are mounted on the print cartridge  203  in the proper order of magenta, cyan, yellow, and black, that is, starting with magenta on the bottom and ending with black on the top as viewed in FIG. 9, then each ink extraction needle  22  will be positioned at a through hole  42 . On the other hand, if the ink cartridges  40  are mounted in any other order, the ink extraction needle  22  will not be positioned at a through hole  42  of the mismounted ink cartridge  40 . This configuration prevents a user from accidentally mounting the wrong ink cartridge  40  and mixing ink from one ink cartridge with ink from another ink cartridge. It should be noted that the ink cartridges  40  can alternately be formed into an integral unit. 
     Next, while referring to FIGS. 10 to  15 , an ink jet printer  300  according to a fourth embodiment of the present invention will be described. The ink jet printer  300  includes a print head mounting means and a print head separation means. It should be noted that the print head mounting means and the print head separation means are essential components of the ink jet printers of the first to third embodiments and will be explained here using the ink jet printer  300  merely as a representative example. 
     FIG. 10 is a plan view showing the ink jet printer  300  according to the fourth embodiment. The ink jet printer  300  includes a printer body  301  and a print cartridge  302 . The printer body  301  has a main frame  301   a  formed in an approximately box shape. The print cartridge  302  has a cartridge frame  302   a  formed in a substantially box shape. The print cartridge  302  is detachably provided on the printer body  301 . A rectangular shaped discharge port  303  through which printed print sheets PP are discharged is formed in the front wall of the printer body  301 . 
     As shown in FIG. 11, the print cartridge  302  includes ink cartridges  311  disposed at a predetermined position. A print head  309  is formed with nozzles  309   a  for ejecting ink toward print sheet PP. In the ink jet printer  300  with this configuration, ink from the ink cartridges  311  is supplied to the print head  309 . The print head  309  ejects the ink from the nozzles  309   a  to print on a print sheet PP. 
     A sheet feed port  304  through which unprinted print sheets PP are inserted is formed in the lower right side of the printer body  301 . Print sheet PP inserted through the sheet feed port  304  are transported in a sheet transport direction Y indicated in FIG. 11. A transport roller  305  and a pressing roller  306  are disposed downstream from the sheet feed port  304  in the transport direction Y. The transport roller  305  for transporting print sheets PP and the pressing roller  306  for pressing the print sheets PP against the transport roller  305  cooperate together to press and support print sheets PP while transporting them. 
     A sheet discharge roller  307  and a pressing roller  308  are disposed downstream from the rollers  305 ,  306 . The sheet discharge roller  307  is for discharging print sheets PP transported by the transport roller  305  out of the printer body  301 . The pressing roller  308  is for pressing print sheet PP against the sheet discharge roller  307 . A carriage  310  is disposed above where sheets are disposed when supported between the transport roller  305  and the sheet discharge roller  307 . The print head  309  is detachably mounted on carriage  310  above where sheets are disposed when supported between the transport roller  305  and the sheet discharge roller  307 . 
     A guide bar  313  spans between opposing sides of a frame  319  of the printer body  301 . The carriage  310 , on which the print head  309  is detachably mounted, is reciprocally movable along the guide bar  313  in a direction Z indicated in FIG.  12  and in a direction opposite to the direction Z. The nozzles  309   a  are formed in the print head  309  at the side thereof confronting the print sheet PP supported between the transport roller  305  and the sheet discharge roller  307 . Rectangular protrusions  309   b  are provided on the upper edges of the side walls of the print head  309 . As will be described later, the rectangular protrusions  309   b  are for stopping the print head  309  at a predetermined position in the print cartridge  302  when the print cartridge  302  is detached from the printer body  301 . 
     Retaining members  314  for supporting the protrusions  309   b  are formed integrally with the print cartridge  302  at positions immediately below corresponding protrusions  309   b . Rectangular engagement grooves  314   a , into which the protrusions  309   b  are fitted, are formed in the upper surface of the retaining members  314  at positions in opposition with corresponding protrusions  309   b . With this configuration, when the print cartridge  302  is lifted up and removed from the printer body  301 , the retaining members  314  will be raised up so that the protrusions  309   b  of the print head  309  engage in corresponding engagement grooves  314   a . Thus, the print head  309  is engaged with the print cartridge  302 . 
     As will be described later, a pressing spring member  315  presses down on the print head  309  while the print head  309  is held onto the print cartridge  302  via engagement of the protrusions  309   b  in the engagement grooves  314   a  of the retaining members  314 . The pressing spring member  315  insures that the print head  309  will be properly pressed down so that even if the printer cartridge  302  is dropped or otherwise subjected to a large shock, the downward pressing operation will not be accidentally released and the print head  309  will not be shifted out of position. 
     The four ink cartridges  311  are detachably mounted in the print cartridge  302 , stacked one on top of the other. Each ink cartridge  311  is filled with a different colored ink. In the example shown in FIG. 11, the upper-most ink cartridge  311  is filled with black ink, the second one down is filled with yellow ink, the third one down is filled with cyan colored ink, and the lowest ink cartridge  311  is filled with magenta colored ink. 
     Four ink supply tubes  312  are provided for supplying ink to the print head  309 . Each ink supply tube  312  is attached at one end to a corresponding one of the ink cartridges  311  and at the other end to the upper portion of the print head  309 , which is disposed below the ink cartridge  311 . Because the ink supply tubes  312  connect the print head  309  with each ink cartridge  311 , ink can be supplied from the ink cartridges  311 , which are disposed at predetermined positions in the print cartridge  302 , to the print head  309 . It should be noted that the print head  309  is mounted on the carriage  310  and moves reciprocally within the ink jet printer  300  leftward and rightward as viewed in FIG.  12 . 
     As shown in FIG. 12, the retaining members  314  are formed in a substantial plate shape. The engagement grooves  314   a  are formed in the upper surface of the retaining members  314  in confrontation with the protrusion  309   b  of the print head  309 . The engagement grooves  314   a  are formed to substantially the same depth as the thickness of the protrusion  309   b . Further, the engagement grooves  314   a  and the protrusions  309   b  of the print head  309  are formed to the same length in the lengthwise direction of the ink jet printer  300 . With this configuration, when the protrusions  309   b  are fitted in the engagement grooves  314   a , the print head  309  is held to the print cartridge  302  and prevented from rattling around. The lengthwise ends of the protrusion members  309   b , that is, the ends of the protrusions  309   b  that confront sidewalls of the engagement grooves  314   a , are formed in a curved shape as best shown in FIG.  13 . Therefore, when the protrusions  309   b  are fitted in the engagement grooves  314   a , the edges of the protrusions  309   b  formed with these curve surfaces can be easily fitted in the engagement grooves  314   a . Alternatively, the ends of the protrusions  309   b  are chamfered for the same purpose. 
     A carriage return motor or CR motor  320  is disposed at the upper portion of the frame  319 , which is disposed at the left side of the printer body  301 . The carriage return motor  320  is for supplying drive force for reciprocally moving the carriage  310  rightward in the direction Z and leftward in the direction opposite the direction Z. A line feed motor or LF motor  321  for rotating the transport roller  305  and the sheet discharge roller  307  is disposed below the carriage return motor  320 . 
     As shown in FIG. 13, the print head  309  is formed with a rectangular shape holding groove  309   c  in its right side surface and with a substantially trapezoid shaped indentation  309   d  in its left side surface, that is, in the side surface opposite the side surface in which the holding groove  309   c  is formed. The print head  309  is further formed with two protrusion portion  309   e , one above each of the holding groove  309   c  and the indentation  309   d . The protrusion portions  309   e  are both formed so as to protrude outward away from the print head  309  and are positioned to abut against the upper surface of the carriage  310  as shown in FIG.  13 . With this abutment, the print head  309  can be prevented from passing through and falling away from the carriage  310 . 
     The carriage  310  is formed in a hollow box shape with the upper and lower surfaces open. The print head  309  is insertingly mounted in the open portion of the carriage  310 . A holding pawl  310   a  is fixed to the right side of the carriage  310 , and an approximately trapezoid shaped protrusion  310   b  is formed in the left side of the carriage  310 . Both the holding pawl  310   a  and the protrusion  310   a  are for holding the print head  309  firmly onto the carriage  310  as will be described next. 
     The holding pawl  310   a  is formed at its upper free end portion in a substantially D shaped bend that fits in the holding groove  309   c  of the print head  309  so that the print head  309  is held firmly to the carriage  310 . The holding pawl  310   a  is formed from a resilient material, such as spring steel material, and so as to be capable of resiliently deforming. Accordingly, the holding pawl  310   a  fits in and pulls out of the holding groove  309   c  of the print head  309  as the print head  309  is attached to or detached from the carriage  310 . It should be noted that in order to mount the print head  309  onto the carriage  310  by resiliently deforming the holding pawl  310   a , it is necessary to press the print head  309  onto the carriage  310  using a force of about 1 kgf, which force is sufficient to provide the resilient deformation of the holding pawl  310   a . The protrusion  310   b  protrudes toward the interior of the carriage  310  and is formed in a shape adapted to fit into the indentation  309   d  of the print head  309 . 
     With this configuration, the print head  309  can be fixed to the carriage  310  by fitting the protrusion  310   b  and the holding pawl  310   a  into the indentation  309   d  and the holding groove  309   c , respectively. Because the protrusion  310   b , and the bent upper portion of the holding pawl  310   a , are disposed at positions confronting the carriage  310  at the same level, the protrusion  310   b  and the holding pawl  310   a  are fitted into the indentation  309   d  and the holding groove  309   c , respectively, at almost the same time. Accordingly, the possibility of either one of the holding pawl  310   a  or the protrusion  310   b  being fitted first, that is, into the holding groove  309   c  and the indentation  309   d , respectively, before the other can be prevented, so that the print head  309  will not be mounted at a tilting posture. There is also no danger of the user forcefully mounting the print head  309  onto the carriage  310  at the tilting posture. The printer body  301  and the print cartridge  302  are consequently more durable, and so can withstand repeated attachment and detachment of the print cartridge  302  to and from the print cartridge  302 . 
     As shown in FIG. 13, when the print cartridge  302  is mounted on the printer body  301 , the lower surface of each protrusion  309   b , which are both disposed at the upper sides of the print head  309 , will be positioned spaced away from the upper surface of corresponding engagement grooves  314   a , which are formed in the retaining members  314  of the print cartridge  302 . Therefore, during printing on the print sheet PP, the print head  309  mounted on the carriage  310  can be reciprocally moved in the left and right directions as viewed in FIG. 13 without the protrusions  309   b  catching in the engagement grooves  314   a  of the retaining members  314 . 
     The pressing spring member  315  for pressing against the upper edge of the print head  309  is provided to the lower left side of the print cartridge  302 . The pressing spring member  315  is disposed above and to the left of the print head  309 . The pressing spring member  315  is a coil spring formed from a resilient material such as spring steel. The pressing spring member  315  has an abutment portion  315   b  at one end, an attachment portion  315   c  at its substantial center, and a pressing portion  315   a  at its other end. The attachment portion  315   c  is wound around a support shaft  316  formed in the print cartridge  302 , so that the pressing spring member  315  is supported to the print cartridge. The abutment portion  315   b  is disposed in abutment with the inner left wall of the print cartridge  302 . The pressing portion  315   a  is disposed above the print head  309 . The pressing portion  315   a  and the abutment portion  315   b  are formed in combination into L-shape. 
     The pressing portion  315   a  is disposed so as to be swingable in the vertical direction about the support shaft  316 . The pressing portion  315   a  has a substantially V shaped tip. The abutment portion  315   b  urges the pressing portion  315   a  downward so that the V shaped tip abuts against the upper end of the print head  309  and presses the print head  309  downward, thereby preventing the print head  309  from moving upward. As shown in FIG. 13, the V shaped tip of the pressing portion  315   a  is formed at a position separated by a distance L 1  from an axial center of the support shaft  316 . 
     In a manner to be described later, it is necessary to press the print head  309  into the carriage  310  with pressing force of about 1 kgf in order to mount the print head  309  onto the carriage  310 . Therefore, the pressing spring member  315  is formed to press the upper surface of the print head  309  downward with a pressing force of more than 1 kgf. 
     A rectangular shaped guide member  318  is formed on the print cartridge  302 . A link member  317  formed in a substantially rod shape is slidably mounted in the guide member  318 . The link member  317  is disposed below the pressing spring member  315  and is for pressing the pressing spring member  315  upward in a manner to be described below. A rectangular shaped pressed portion  317   a  is fixed to the lower tip of the link member  317 . A stop portion  317   b  for preventing the link member  317  from falling out of the guide member  318  is fixed to the link member  317  at a position above the guide member  318 . Therefore, the downward travel can be stopped by the abutment of the stop portion  317   b  against the top surface of the guide member  318 . 
     The plate shaped frame  319  is provided to the printer body  301  at a position directly below the pressed portion  317   a  of the link member  317 . A link pressing portion  319 a for pressing the link member  317  upward is integrally formed with the frame  319  and extends upward from the upper edge of the frame  319 . With this configuration, there is no need to provide the printer body  301  with a separate member for pressing the link member  317  upward, so the ink jet printer  300  can be produced using fewer parts. 
     The link member  317  is disposed at a position so that its upper tip abuts the lower surface of the pressing portion  315   a  at a position near the attachment portion  315   c . More specifically, the link member  317  is positioned by the guide member  318  so that the upper tip of the link member  317  abuts against and presses the pressing spring member  315  upward at a position separated by a distance L 2  from the axial center of the support shaft  316 , wherein the distance L 2  is smaller than the distance L 1 . Accordingly, the link member  317  abuts the pressing portion  315   a  at a position nearer to the attachment portion  315   c  than where the pressing portion  315   a  abuts against the print head  309 . Therefore, the pressing portion  315   a  can be lowered downward greatly by moving the link member  317  downward only by a slight amount. The amount that the pressing portion  315   a  is raised and lowered can be made much greater than the amount that the link member  317  is raised and lowered. Accordingly, by moving the link member  317  only slightly with respect to the pressing spring member  315 , the pressing portion  315   a  can be swung greatly in the vertical direction. 
     In the ink jet printer  300  of the fourth embodiment, the guide member  318  is positioned so that the L 2  is about one third of the distance L 1 . Accordingly, when the upper tip of the link member  317  presses the pressing spring member  315  upward by about 3 mm, the pressing portion  315   a  can be pressed upward by three times that amount, or by 9 mm. Accordingly, the pressing spring member  315  can be prevented from abutting against the print head  309  and obstructing movement of the print head  309  while the print head  309  is mounted on the carriage  310  and printing is performed by reciprocally moving the print head  309  in the direction Z and in the direction opposite the direction Z. 
     Next, while referring to FIG. 14, operations for removing the print cartridge  302  from the printer body  301  will be described. FIG. 14 is a cross-sectional view similar to FIG. 13, showing the print cartridge slightly detached from the printer body  301  so that the pressing spring member  315  presses against the print head  309  mounted on the carriage  310 . As shown in FIG. 14, to detach the print cartridge  302  from the printer body  301 , first, the print cartridge  302  is lifted up slightly away from the printer body  301 . That is, the print cartridge  302  shown in FIG. 13 is lifted and moved upward to the position shown for the print cartridge  302  in FIG.  14 . When the print cartridge  302  is moved slightly upward, the retaining members  314  move upward with the print cartridge  302  so that the protrusions  309   b  fit into the engagement grooves  314   a . Simultaneously with this, slight upward movement of the print cartridge  302  is translated into slight downward movement of the link member  317 . Therefore, the pressing portion  315   a  moves downward and abuts against the upper surface of the print head  309  so that the print head  309  is pressed downward. 
     Because the link member  317  abuts the pressing portion  315   a  at a position closer to the attachment portion  315   c  than where the pressing portion  315   a  abuts against the print head  309 , the slight downward movement of the link member  317  is translated into a large downward movement of the pressing portion  315   a . Therefore, by merely lifting the print cartridge  302  slightly upward, the pressing spring member  315  will rapidly press against the print head  309  so that when the print cartridge  302  is removed, the print head  309  can be prevented from moving out of place. 
     When the print cartridge  302  is further lifted upward, the print head  309  will also be lifted upward. When the print head  309  is lifted upward, the holding pawl  310   a  deforms and separates from the holding groove  309   c . Simultaneously, the protrusion  310   b  of the carriage  310  separates from the indentation  309   d  of the print head  309 . As a result, the print head  309  separates from the carriage  310  in association with separation of the printer cartridge  302  from the printer body  301 . 
     When the print head  309  separates from the carriage  310  and the print cartridge  302  separates from the printer body  301 , the pressed portion  317   a  of the link member  317  separates from the link pressing portion  319   a  of the frame  319 . When the pressed portion  317   a  separates from the upper tip of the link pressing portion  319   a , the link member  317  further slides downward via the guide member  318 . As a result, the upper tip of the link member  317  separates from the pressing spring member  315  so that the pressing spring member  315  completely presses against the print head  309 . At this time, the print head  309  is pressed down while in the left side portion of the print cartridge  302 . 
     Next, while referring to FIGS. 14 and 15, operations to mount the print cartridge  302  onto the printer body  301  will be described. The operations for mounting the print cartridge  302  onto the printer body  301  are performed using the opposite order of operations for separating the print cartridge  302  from the printer body  301 . As shown in FIG. 15, the print cartridge  302  is first aligned above the printer body  301  with the print head  309  in opposition with the carriage  310 . 
     After the print cartridge  302  is positioned in this manner, the print head  309  is inserted into the carriage  310 . At this time, the print head  309  is pressed downward by the pressing spring member  315 . The printhead  309  is inserted into the carriage  310  until the holding pawl  310   a  and the protrusion  310   b  of the carriage  310  are fitted in the holding groove  309   c  and the indentation  309   d , respectively, of the print head  309  and until both of the protrusion portions  309   e  of the print head  309  abut against the upper surface of the carriage  310 . In this way, the print head  309  is mounted on the carriage  310  as shown in FIG. 14 in association with mounting of the print cartridge  302  onto the printer body  301 . 
     As mentioned above, the print head  309  must be pressed downward with a pressing force of about 1 kgf when inserted into the carriage  310  so as to deform the holding pawl  310   a . Since print head  309  is pressed downward by the pressing spring member  315  by a force of more than 1 kgf, the print head  309  can be easily pressed into the print head  309 . 
     As shown in FIG. 14, the pressed portion  317   a  is brought into abutment with the link pressing portion  319   a  simultaneously with mounting of the print head  309  onto the carriage  310 . As a result, the link member  317  is pressed and slidingly moved upward by the link pressing portion  319   a  relative to the guide member  318 . When the link member  317  is pressed upward, the upper tip of the link member  317  abuts against the pressing spring member  315  and the link member  317  starts to press the pressing portion  315   a  upward. Afterward, when the print cartridge  302  is further pressed onto the print cartridge  302  so that the print cartridge  302  slightly moves downward, the link pressing portion  319   a  further presses the link member  317  slightly upward so that the link member  317  presses the pressing portion  315   a  upward away from the print head  309 . 
     Because the link member  317  abuts against the pressing portion  315   a  at a position nearer the attachment portion  315   c  than where the pressing portion  315   a  abuts against the print head  309 , the slight upward movement of the link member  317  translates into a large upward movement of the pressing portion  315   a . That is to say, the upward movement amount of the pressing portion  315   a  is much greater than the upward movement amount of the link member  317 . Therefore, by pressing the print cartridge  302  slightly downward onto the print cartridge  302 , the pressing portion  315   a  can be reliably pressed upward away from the print head  309 . It should be noted that according to the present embodiment, when the link pressing portion  319   a  presses the link member  317  upward by about 3 mm, the pressing portion  315   a  will be pressed upward by about 9 mm. 
     When the print cartridge  302  moves further downward, the link member  317  presses the pressing portion  315   a  further upward away from the print head  309 . Also, the retaining members  314  move downward with movement of the print cartridge  302 . As a result, the protrusions  309   b  is moved upward relative to the engagement grooves  314   a  so that the protrusions  309   b  separate from the engagement grooves  314   a . By the time the protrusions  309   b  separate from the engagement grooves  314   a , the pressing spring member  315  has stopped pressing against the print head  309 . This completes operations for mounting the print cartridge  302  onto the printer body  301 . 
     When the print cartridge  302  is mounted in this manner, the ink jet printer  300  is capable of printing on a print sheet PP. That is to say, when an unused print sheet PP is inserted into the sheet feed port  304 , the line feed motor  321  rotates to drive rotation of the transport roller  305  and the pressing roller  306 , thereby transporting the unused print sheet PP to below the print head  309 . When the print sheet PP transported in this manner passes below the print head  309 , the carriage  310  is driven by the carriage return motor  320  and ink is ejected from the nozzles  309   a  formed in the print head  309  mounted on the carriage  310  so that printing is performed on the print sheet PP. The printed print sheet PP is then discharged through the discharge port  303  by rotation of the sheet discharge roller  307  and the pressing roller  308 , which are driven by rotation of the line feed motor  321 . It should be noted that the ink filling the ink cartridge  311  is supplied to the print head  309  through the ink supply tube  312  and ejected from the nozzles  309   a  of the print head  309 . 
     According to the ink jet printer  300  of the fourth embodiment, the protrusions  309   b  and the engagement grooves  314   a  hold the print head  309 , which is capable of reciprocal movement within the ink jet printer  300  in association with movement of the carriage  310 , at a predetermined position in the print cartridge  302  when the print cartridge  302  is separated from the printer body  301 . Also, the pressing spring member  315  presses the print head  309  at a predetermined position of the print cartridge  302 . Accordingly, the print cartridge  302  can be detached from the printer body  301  and carried around without the print head  309  moving around in the print cartridge  302 . Further, the print head  309  can be attached to and detached from the carriage  310  in association with the attachment and detachment of the print cartridge  302  to and from the printer body  301 . 
     Because the print head  309  is pressed and held in place at a predetermined position of the print cartridge  302  when the print cartridge  302  is mounted on the printer body  301  and the print head  309  is mounted on the carriage  310 , there is no need for the user to grasp the print head  309  by hand and move it to a predetermined position. Therefore, the user can avoid staining his or her hands. printer body  301  so that the print head  309  is mounted on the carriage  310 , the link member  317  and the link pressing portion  319   a  prevent the pressing spring member  315  from pressing against the print head  309 . Accordingly, the pressing spring member  315  will not interfere with movement of the print head  309 . Therefore, the print head  309  mounted on the carriage  310  can reciprocally move within the ink jet printer  300  without interference. 
     While the invention has been described in detail with reference to specific embodiments thereof, it would be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention. 
     In the forgoing embodiments, the entire ink package  30  was formed from a laminated film and the ink extraction needle  22  was inserted into the indentation portion  32  to extract ink. However, different configurations can be provided for performing extraction of ink. For example, ink can be sealed directly into the ink cartridge itself without using the ink package  30 . In this case, a laminated film to be pierced by the ink extraction needle  22  can be fused onto a portion of the ink cartridge. During use, the laminated film member is pierced by the ink extraction needle  22  and ink is extracted from the ink cartridge. It should be noted that in this case, the ink cartridge can be formed from a polyoxymethylene (POM) or other material that can, without undesirable results, come into contact with ink used in printing. In other words, the cartridge should be formed of a material compatible with the ink. 
     The third embodiment describes that the ink extraction needles  22  are attached at different positions with respect to the front and rear direction of FIG.  9  and that the through hole  42  are formed at positions corresponding to the ink extraction needles  22 . However, the positions of the ink extraction needle  22  and the through hole  42  are not restricted to this configuration. For example, ink extraction needles can be disposed at the same position with respect to the front and rear direction of FIG.  9 . That is, ink extraction needles can be disposed in a vertically aligned arrangement. In this case, the through holes are formed at about the same position in their respective ink cartridges so that the same cartridge body can be used for all different colored inks. In this case, the number of different types of print cartridge  203  can be reduced. 
     The third embodiment describes use of a plurality of separate ink cartridges  40 . However, a plurality of ink cartridges can be formed in an integral unit. In this case, by providing a partition member between adjacent ink packages housed in the integral ink cartridge, the ink packages can be prevented from directly contacting each other. Accordingly, there is no danger that contact between the ink packages will change internal pressure within the ink sealed portions. 
     Regarding all embodiments, the link pressing portion  319   a  is provided at the upper surface of the frame  319  for pressing the link member  317  upward. However, other configurations can be provided for pressing the link member  317  upward. For example, a separate pressing member for pressing the link member upward can be provided to the printer body. In other words, any kind of arrangement is available as long as the link member can press the spring member  315  upward above the print head when the printer cartridge is mounted on the printer body. 
     In the foregoing embodiments, the holding pawl  310   a  and the trapezoid shaped protrusion  310   b  are provided to the carriage  310 , and the holding groove  309   c  and the trapezoid shaped indentation  309   d  are formed in the print head  309 . However, the holding pawl and the trapezoid shaped protrusion can be provided to the print head and the holding groove an the trapezoid shaped indentation can be formed in the carriage.