Patent Publication Number: US-7905583-B2

Title: Ink supply system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2005-220411, filed Jul. 29, 2005, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an ink supply system and an image recording apparatus including the ink supply system which stably supplies the ink fed from an ink supply section to a plurality of ink nozzles in recording heads. 
     2. Description of the Related Art 
     In recent years, an image recording apparatus which easily, inexpensively and rapidly records an image on a recording medium has a recording head group (a linear ink head module) mounted therein. The recording head group has a structure in which a plurality of recoding heads are arranged in rows on a fixed carriage. An image recording apparatus which records an image with respect to a recording medium to be carried in this manner has been put into practical use. 
     In general, this recording head group is arranged to be greater than a width of a recording medium along a direction (a width direction of the recording medium) perpendicular to a carriage direction of the recording medium, and a plurality of ink nozzles arranged in each recording head along the width direction of the recording medium. The plurality of ink nozzles form a nozzle line. In the case of an image recording apparatus which performs color recording, a plurality of nozzle lines corresponding to this color recording must be configured. 
     In order to improve and stabilize a quality of an image to be recorded, a pressure loss of the recording head group with respect to an ink path must be uniformed when supplying the ink to respective recording heads for the same color. 
     As a prior art of a recording apparatus which uniforms such a pressure loss of an ink path, e.g., Jpn. Pat. Appln. KOKAI Publication No. 2003-251826 is disclosed.  FIG. 9  shows a recording apparatus disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2003-251826. 
     In this recording apparatus is provided a liquid storing container  72  (including a negative pressure stabilizing mechanism) having a movable member  71  which can at least partially transform in accordance with an amount of ink, a spring member  73  which exercises a spreading force with respect to the movable member  71  to generate a necessary negative pressure (a pressure loss), and communication openings  74  through which air is introduced into the inside in accordance with an increasing negative pressure. 
     This recording apparatus introduces air into the liquid storing container  72  from the communication openings  74  in accordance with an amount of ink in the liquid storing container  72 . A negative pressure in the liquid storing container  72  is stabilized by the introduced air and the spring member  73 . Therefore, a pressure loss of an ink path is uniformed. As a result, the recording apparatus stably supplies the ink. 
     Further, Published Japanese Patent No. 2738777 also discloses a similar inkjet recording apparatus. In this inkjet recording apparatus are provided each recording head provided in accordance with ink of each of a plurality of colors, an ink supply source which supplies the ink to each recording head, and each ink supply tube which couples each recording head with the ink supply source. 
     A length of the ink supply tube (an ink supply path) is configured to be shorter as the ink supply tube is compatible with ink which is apt to be hardened and fixed. 
     BRIEF SUMMARY OF THE INVENTION 
     An ink supply system to which an ink of a predetermined color is supplied from an ink supply section according to the present invention comprises at least one of a recording head group in which there are provided a plurality of recording heads each having a plurality ink nozzles through which the ink of the predetermined color is discharged to a recording medium to be carried; a reservoir tank which stores the ink of the predetermined color supplied from the ink supply section; and an ink chamber which distributes and supplies the ink of the predetermined color fed from the reservoir tank to the recording heads provided in the recording head group, wherein the inside of the ink chamber is maintained in a predetermined negative pressure state. 
     An image recording apparatus according to the present invention comprises an ink supply system which has at least one of a recording head group in which there are provided a plurality of recording heads each having a plurality ink nozzles through which the ink of a predetermined color is discharged to a recording medium to be carried, a reservoir tank which stores the ink of the predetermined color and an ink chamber which distributes and supplies the ink of the predetermined color supplied from the reservoir tank to the recording heads provided in the recording head group; an ink supply section which supplies the ink of the predetermined color to the reservoir tank include in the ink supply system; a conveying mechanism which is provided to opposed to the recording head group included in the ink supply system and carries the recording medium; a feeding system which stores the recording medium and feeds the medium to the conveying mechanism; an storing system which stores the recording medium having an image recorded by the recording head group; and a control section which controls the ink supply system, the ink supply section, the carriage mechanism, the feeding system and the storing system. 
     Advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention. 
         FIG. 1  is a conceptual block diagram showing a relationship between an ink supply system and an image recording apparatus including the ink supply system according to the present invention; 
         FIG. 2  is an arrangement plan of the image recording apparatus excluding an ink supply section, a control section and a part of the ink supply system; 
         FIG. 3  is a perspective view showing a first embodiment of the ink supply system according to the present invention; 
         FIG. 4  is a front view showing the first embodiment of the ink supply system according to the present invention; 
         FIG. 5  is a top view showing the first embodiment of the ink supply system according to the present invention; 
         FIG. 6  is a perspective view showing a second embodiment of the ink supply system according to the present invention; 
         FIG. 7  is a top view showing a first modification of the first and second embodiments of the ink supply system according to the present invention; 
         FIG. 8  is a top view showing a second modification of the first and second embodiments of the ink supply system according to the present invention; and 
         FIG. 9  is a view showing an ink supply path provided in a conventional recording apparatus. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments according to the present invention will now be described hereinafter in detail with reference to the accompanying drawings. 
     An embodiment according to the present invention will be explained in conjunction with  FIGS. 1 to 8 . 
       FIG. 1  is a conceptual block diagram showing a relationship between an ink supply system and an image recording apparatus including the ink supply system according to the present invention; 
     The image recording apparatus  11  shown in  FIG. 1  is provided with at least a conveying mechanism  14  having a conveyance information generating section  15  and a driving section  16 , a feeding system  17  which feeds a recording medium (not shown in  FIG. 1 ) to the conveying mechanism  14 , a storing system  18  which stores the recording medium having an image recorded thereon which has been ejected by the conveying mechanism  14 , an ink supply section  12  which stores an ink of a predetermined color and supplies the ink of the predetermined color to a later-described ink supply system  1 , and a control section  13 . Further, the image recording apparatus  11  includes at least one of the ink supply system  1  which is characteristic of the present invention. 
     The control section  13  controls the ink supply system  1 , the ink supply section  12 , the conveying mechanism  14 , the feeding system  17 , and the storing system  18 . 
     The ink supply system  1  is provided with at least a reservoir tank  2  which stores a predetermined amount of the ink of the predetermined color supplied from the ink supply section  12 , an ink chamber  3  which stores a predetermined amount of the ink supplied from the reservoir tank  2  and distributes this ink to recording heads, and a recording head group  4  having a plurality of recording heads. 
     Each recording head in this recording head group  4  has a plurality of ink nozzles from which the ink is discharged to the recording medium to be carried. 
     A description will now be given as to an arrangement of the image recording apparatus  11  excluding the ink supply section  12 , the control section  13  and a part of the ink supply system  1  with reference to  FIG. 2 . 
     In the feeding system  17  are provided a feeding tray  22 , a pickup roller  23  and a resist roller pair  24 . 
     The feeding tray  22  stores a plurality of the recording mediums  21 . 
     The pickup roller  23  is provided above the feeding tray  22  picks up and carries the recording mediums  21  one by one. 
     The resist roller pair  24  temporarily comes into contact with the picked-up and carried recording medium  21  to correct oblique traveling of the recording medium  21 , and holds and carries the recording medium  21  to the conveying mechanism  14  side after correction. 
     In the conveying mechanism  14  are provided three platen rollers  25 ,  26  and  27  which are distanced from each other at predetermined distances between, e.g., an upstream side and a downstream side of a carriage direction of the recording medium  21  and arranged substantially parallel. An endless belt  30  is wound around the platen rollers  25 ,  26  and  27  to allow its swiveling movement. As a result, the conveying mechanism  14  constitutes a belt conveyance mechanism. 
     For example, a rotary encoder which is the conveyance information generating section  15  is connected with a rotary shaft of the platen roller  25 . For example, a motor which is the driving section  16  is connected with a rotary shaft of the platen roller  27 . 
     Furthermore, rollers  28  and  29  are provided above the platen rollers  25  and  27  opposed to the rollers  25  and  27  across the endless belt  30 , respectively. The rollers  28  and  29  prevent the recording medium  21  from being raised. 
     In the carriage direction of the recording medium  21 , a sucking section  31  having suction fans  32  are provided between the platen roller  25  and the platen roller  27  provided in the inner side of the endless belt  30  along the carriage direction of the recording medium  21 . The sucking section  31  sucks the carried recording medium  21  onto the endless belt  30  by using the suction fan  32 . 
     The recording head group  4  has the plurality of recording heads. A nozzle line (a nozzle forming surface)  4   a  forming the plurality of ink nozzles is provided in each recording head to be opposed to, e.g., the endless belt  30  (a carried surface of the recording medium  21 ) of the conveying mechanism  14 . The recording head group  4  is fixed in a carriage  33  to be opposed to an entire width of the recording medium  21  in a direction perpendicular to the carriage direction of the recording medium  21 . (It is to be noted that  FIG. 2  shows an example where the respective recording head groups K [black], C [cyan], M [magenta] and Y [yellow] are arranged at predetermined intervals from the upstream side toward the downstream side of the carriage direction of the recording medium  21 .) 
     In the carriage direction of the recording medium  21 , a roller pair  34  which carries the recording medium  21  having an image recorded thereon to a storing tray  35  is provided in the upstream side of the storing tray  35  in the storing system  18 . 
     A first embodiment of the ink supply system according to the present invention will now be described with reference to  FIGS. 1 and 3  to  5 . 
     The ink supply section  12  which supplies the ink to the ink supply system  1  will be first explained. This ink supply section  12  supplies the ink to the ink supply system  1  which is characteristic of the present invention, and it is a constituent element different from the ink supply system  1 . 
       FIGS. 3 and 4  show the ink supply section  12  adopting a mode which utilizes a gravitational fall to supply ink. It is assumed that the fall at this time is a distance H. 
     In this ink supply section  12  are provided an ink bottle  65 , an ink supply pipe  66  and an ink opening/closing valve  67 . When the control section  13  opens the ink opening/closing valve  67 , an ink  61  of a predetermined color stored in the ink bottle  65  is supplied to the ink supply system  1 . 
     Moreover, this ink bottle  65  may be substituted by, e.g., a flexible ink container. 
     It is to be noted that the ink supply section  12  may supply the ink from, e.g., an ink tank or the like storing the ink  61  of the predetermined color to the ink supply system  1  through an ink supply pump or the like. 
     As shown in  FIGS. 3 and 4 , a first liquid level detecting section  6  is provided to the reservoir tank  2  of the ink supply system  1 , and a first atmospheric opening valve  5  and a first path  7  are provided above the same. One end of the first path  7  is inserted into the reservoir tank  2  from above and communicates with a position below a liquid level detected by the first liquid level detecting section  6 . 
     The first atmospheric opening valve  5  is constituted of, e.g., an electromagnetic valve. The first liquid level detecting section  6  is formed of, e.g., a float switch, an optical sensor or an electrostatic capacitance sensor. The first path  7  is constituted of a general pipe for ink. 
     As shown in  FIG. 2  and  FIG. 3 , each ink chamber  3  of the ink supply system  1  is arranged with a length which is not smaller than at least a width of the recording medium  21  in a direction of a Y axis (which is substantially perpendicular to the carriage direction of the recording medium), and the number of the ink chambers  3  is the same as the number of the recording head groups  4 . The ink chamber  3  is provided at least above the recording head group. Additionally, the ink chamber  3  has, on both sides of the carriage direction of the recording medium  21 , a head attachment section  44  which holds the plurality of recording heads in a direction substantially vertical to the carried surface of the recording medium  21 . It is to be noted that this head attachment section  44  is integrally or separately provided to the ink chamber  3 . 
     Further, as shown in  FIGS. 3 and 4 , a second liquid level detecting section  9  is provided to the ink chamber  3 , a second atmospheric opening valve  8  is provided above the ink chamber  3 , and the other end of the first path  7  is inserted into the same. The other end of the first path  7  communicates with the ink chamber  3  to be put into the ink  61  of a predetermined color whose liquid level is set by the second liquid level detecting section  9 . 
     The second atmospheric opening valve  8  is constituted of, e.g., an electromagnetic valve. The second liquid level detecting section  9  is formed of, e.g., a float switch, an optical sensor, or an electrostatic capacitance sensor. In initial filling of the reservoir tank  2  and the ink chamber  3  with the ink, when the control section  13  opens the first atmospheric opening valve  5  and the ink opening/closing valve  67 , the ink  61  of the predetermined color is supplied into the reservoir tank  2  from the ink supply section  12 . When the supplied ink  61  is fed to reach a liquid level height position in the reservoir tank  2  by the first liquid level detecting section  6 , the control section  13  closes the first atmospheric opening valve  5 . 
     Then, the control section  13  opens the second atmospheric opening valve  8 . Then, the ink  61  of the predetermined color supplied from the ink supply section  12  and stored in the reservoir tank  2  is fed into the ink chamber  3  through the first path  7 . When the ink  61  is supplied to reach a predetermined liquid level height position in the ink chamber  3  by the second liquid level detecting section  9 , the control section  13  closes the ink opening/closing valve  67  and the second atmospheric opening valve  8  to stop supply of the ink  61 . Initial filling of the reservoir tank  2  and the ink chamber  3  with the ink is carried out in this manner. At this time, the supplied ink  61  of the predetermined color is supplied into the plurality of ink nozzles of the plurality of recording heads  4 - 1  to  4 - 4  through a head-side ink supply openings  43  provided at below the ink chamber  3  and upper parts of the recording heads  4 - 1  to  4 - 4  in the recording head group  4 , a ink supply openings  41  whose number is equal to that of the head-side ink supply openings  43 , and a connection paths  42 . It is to be noted that the head-side ink supply opening  43  is provided at a substantially central part of the nozzle line of each of the recording heads  4 - 1  to  4 - 4 . These recording heads  4 - 1  to  4 - 4  suggest the nozzle lines (each of which records one line with respect to the recording medium  21 ) formed with a length which is not smaller than the width of the recording medium  21 . 
     Therefore,  FIGS. 3 to 5  and later-explained  FIGS. 6 to 8  are shown in a case where n=4 is achieved in the plurality of recording heads  4 - 1  to  4 - n.    
     In the ink chamber  3 , the recording heads  4 - 1  to  4 - 4  are alternately arranged at lengthwise positions in the carriage direction of the recording medium  21 , and the ink supply openings  41  are provided on both sides with a central line between the alternately arranged plurality of recording heads at the center in the vicinity of the arranged recording heads  4 - 1  to  4 - 4 . The number of the ink supply openings  41  is the same as that of the recording heads. 
     It is to be noted that the vicinity of the recording heads  4 - 1  to  4 - 4  suggests a gap or a position immediately above this gap between the plurality of recording heads  4 - 1  to  4 - 4  when they are alternately arranged at the lengthwise positions in the carriage direction of the recording medium  21 , for example. 
     Furthermore, in the ink chamber  3 , the ink supply openings  41  are alternately arranged above the arranged recording heads  4 - 1  to  4 - 4  in accordance with the arrangement positions of the alternately arranged recording heads  4 - 1  to  4 - 4 . 
     Further, in the ink chamber  3 , each ink supply opening  41  is arranged at a substantially central position of the nozzle line of the plurality of ink nozzles of each recording head above the arranged recording heads  4 - 1  to  4 - 4 . 
     The ink supply openings  41  are connected with the head-side ink supply openings  43  through the connection paths  42  whose number is equal to that of the recording heads. These connection paths  42  have the same length. 
     Here, as shown in  FIG. 4 , positions of the nozzle forming surfaces  4   a  forming the plurality of ink nozzles of the recording heads  4 - 1  to  4 - 4  are set above a predetermined liquid level height position set by the first liquid level detecting section  6  by a distance h in the reservoir tank  2 . 
     That is, the ink  61  of the predetermined color supplied from the ink supply section  12  through the reservoir tank  2  is stored in the plurality of ink nozzles of the recording heads  4 - 1  to  4 - 4  without leaking from the ink nozzles. Furthermore, this ink  61  is stored at the predetermined liquid level height position by the second liquid level detecting section  9  in the ink chamber  3 . Moreover, when the ink  61  of the predetermined color in the reservoir tank  2  and the ink chamber  3  reaches the predetermined liquid level height positions by the first liquid level detecting section  6  and the second liquid level detecting section  9 , the control section  13  closes the second atmospheric opening valve  8  so that a predetermined negative pressure acts on the ink  61  of the predetermined color in the ink nozzles by a difference of elevation based on the ink liquid level with the distance h. 
     This predetermined negative pressure state is a so-called water head pressure, and it is generally a mandatory requirement which allows the recording heads to stably discharge ink in the recording heads whose respective ink nozzles are controlled by a piezoelectric element. 
     As a result, the control section  13  can perform ink discharge control in image recording with respect to the ink  61  of the predetermined color in the plurality of ink nozzles of the recording heads  4 - 1  to  4 - 4  in a state where the predetermined water head pressure constantly acts, thereby stably recording an image. 
     It is to be noted that, in recording an image, the first atmospheric opening valve  5  is opened. That is, when the control section  13  controls opening/closing operations of the ink opening/closing valve  67 , the ink liquid level in the reservoir tank  2  can be maintained at a predetermined height, and this liquid level can be maintained in a state where the predetermined water head pressure acts on the ink  61  in the ink nozzles. 
     As described above, according to the first embodiment of the ink supply system of the present invention, the reservoir tank  2  which stores the ink  61  of the predetermined color at a position (an ink liquid level) which is below the positions of the nozzle forming surfaces  4   a  of the recording heads  4 - 1  to  4 - 4  by the distance h is communicated with the ink chamber  3  provided above the recording heads through the first path  7 . As a result, this embodiment can readily set and maintain the water head pressure with respect to the ink  61  in the ink nozzles of the recording heads  4 - 1  to  4 - 4 . 
     Moreover, in the ink chamber  3 , the recording heads  4 - 1  to  4 - 4  are alternately arranged at the lengthwise positions in the carriage direction of the recording medium  21 , and the ink supply openings  41  are arranged on both sides with the central line between the alternately arranged recording heads  4 - 1  to  4 - 4  at the center in the vicinity of the arranged recording heads  4 - 1  to  4 - 4 . Therefore, the ink chamber  3  can uniform a pressure loss in the ink supply paths leading to the recording heads  4 - 1  to  4 - 4 . 
     A second embodiment of a ink supply system  1  according to the present invention will now be described with reference to  FIGS. 1 and 6 . 
     The second embodiment of the ink supply system  1  is different from the first embodiment in that a predetermined liquid level height position in a reservoir tank  2  set by a first liquid level detecting section  6  is above positions of a nozzle forming surfaces  4   a  of a recording heads  4 - 1  to  4 - 4  as shown in  FIG. 6 , whereas the positions of the nozzle forming surfaces  4   a  of the recording heads  4 - 1  to  4 - 4  are set above the predetermined liquid level height position in the reservoir tank  2  set by the first liquid level detecting section  6  by the distance h in the first embodiment. 
     Moreover, another difference from the first embodiment lies in that the reservoir tank  2  is provided above an ink chamber  3 . Therefore, one end of a first path  7  is put into the reservoir tank  2 . Additionally, the other end of the same is put into ink stored in the ink chamber  3  like the foregoing embodiment. The reservoir tank  2  communicates with the ink chamber  3  through the first path  7 . 
     Further, still another difference from the first embodiment lies in that one end of a second path  10  communicates with the reservoir tank  2  at a position above the predetermined liquid level height position set by the first liquid level detecting section  6 , and a negative pressure generation pump  62  is connected with the other end of the second path  10  through a negative pressure opening/closing valve  64 . 
     Yet another difference from the first embodiment lies in that an ink opening/closing valve  63  is provided to the first path  7  communicating with the ink chamber  3 . 
     An ink  61  of a predetermined color in an ink supply section  12  is supplied to the reservoir tank  2  when a first atmospheric opening valve  5  and an ink opening/closing valve  67  are controlled to be opened by a control section  13  like the first embodiment. 
     Moreover, when the ink  61  of the predetermined color in the reservoir tank  2  is supplied into a plurality of ink nozzles of the recording heads  4 - 1  to  4 - 4  and the ink chamber  3 , the control section  13  opens the first atmospheric opening valve  5 , the ink opening/closing valve  63  and a second atmospheric opening valve  8 , respectively. The ink  61  is supplied by a gravitational fall. When the ink  61  is supplied to reach a predetermined liquid level height detected by a second liquid level detecting section  9 , the control section  13  closes both the second atmospheric opening valve  8  and the ink opening/closing valve  63 . The ink is allowed to flow in or blocked off by opening/closing the valves in this manner, thereby adjusting an ink supply amount. 
     Then, when the ink  61  of the predetermined color in the reservoir tank  2  is at the predetermined liquid level height position detected by the first liquid level detecting section  6 , the control section  13  closes both the first atmospheric opening valve  5  and the ink opening/closing valve  67 , opens both the ink opening/closing valve  63  and the negative pressure opening/closing valve  64 , thereby driving the negative pressure generation pump  62 . As a result, a predetermined negative pressure acts on the ink  61  of the predetermined color in the plurality of ink nozzles of the recording heads  4 - 1  to  4 - 4 . This predetermined negative pressure state corresponds to a setting of the so-called water head pressure described in conjunction with the first embodiment. 
     When the predetermined negative pressure acts on the ink  61  in the ink nozzles, the control section  13  stops driving the negative pressure generation pump  62  to close the negative pressure opening/closing valve  64 . In this manner, according to this embodiment, since the predetermined water head pressure constantly acts on the ink  61  of the predetermined color in the plurality of ink nozzles of the recording heads  4 - 1  to  4 - 4  in a recording head group  4 , an image can be stably recorded. 
     It is to be noted that the first atmospheric opening valve  5  is opened during recording an image in the first embodiment, but the first atmospheric opening valve  5  is closed in this embodiment. 
     As described above, according to this embodiment, when the ink  61  of the predetermined color in the reservoir tank  2  is supplied into the reservoir tank  2  to reach the predetermined liquid level height position detected by the first liquid level detecting section  6 , the control section  13  drives the negative pressure generation pump  62  to generate the negative pressure in the second path  10 . 
     The generated negative pressure acts on the ink  61  of the predetermined color in the ink chamber  3  through the communicated reservoir tank  2 , the first path  7  and the ink opening/closing valve  63 . Therefore, this embodiment can readily set and maintain the predetermined water head pressure with respect to the ink  61  of the predetermined color in the plurality of ink nozzles of the recording heads  4 - 1  to  4 - 4 . 
     Additionally, in the ink chamber  3 , the recording heads  4 - 1  to  4 - 4  are alternately arranged at lengthwise positions in a carriage direction of a recording medium  21 . Further, in the ink chamber  3 , ink supply openings  41  are provided in both sides in the vicinity of the recoding heads  4 - 1  to  4 - 4  with a central line between the alternately arranged recording heads  4 - 1  to  4 - 4  at the center. Therefore, this embodiment can uniform a pressure loss of ink supply paths leading to the recording heads  4 - 1  to  4 - 4  like the first embodiment. 
     A description will now be given as to a first modification of the first and second embodiments of a ink supply system according to the present invention. 
       FIG. 7  shows the first modification of the first and second embodiments. 
     In the ink chamber  3  according to the first and second embodiments, the head-side ink supply openings  43  are arranged at the substantially central part of the nozzle lines of the recording heads  4 - 1  to  4 - 4  in order to connect the head-side ink supply openings  43  with the connection paths  42  above the arranged recording heads  4 - 1  to  4 - 4 . On the other hand, according to the first modification, a head-side ink supply openings  52   a  and  52   b  are arranged at a both end sections  51  of each of the recording heads  4 - 1  to  4 - 4  in a nozzle line direction. The head-side ink supply openings  52   a  and  52   b  are symmetrically arranged with a central position of the nozzle line of each of the recording heads  4 - 1  to  4 - 4  at the center, and they can be connected with the connection path  42 . 
     The ink chamber  3  according to this first modification is different from the counterpart according to the foregoing embodiments in that the recording heads  4 - 1  to  4 - 4  are alternately arranged at the lengthwise positions in the carriage direction of the recording medium  21  and each ink supply opening  41  is arranged on both sides with the central line between the recording heads  4 - 1  to  4 - 4  at the center in accordance with the two head-side ink supply openings  52   a  and  52   b.    
     As a result, according to this first modification, each ink supply opening  41  can be selectively connected with one of the head-side ink supply openings  52   a  and  52   b  and used. At this time, the head-side ink supply opening  52   a  or  52   b  which is not used is closed by, e.g., thermofusion. 
     Further, according to the first embodiment, when the head-side ink supply openings  52   a  and  52   b  are provided in both sides of the both end sections  51  of the recording heads  4 - 1  to  4 - 4  along the nozzle line direction, an electrical connecting section for an actuator of each of the recording heads  4 - 1  to  4 - 4  can be provided between the head-side ink supply opening  52   a  and the head-side ink supply opening  52   b , for example. 
     Furthermore, according to this first modification, since the two head-side ink supply openings  52   a  and  52   b  are provided with respect to one recording head, circulation cleaning of a head ink chamber can be performed by using a cleaning liquid at the time of manufacture of the recording heads. Alternatively, there can be obtained a secondary effect. For example, air bubbles are stored in a head common pressure chamber, and an air damper can be provided for a fluctuation in a pressure in the head common pressure chamber. Moreover, there can be also obtained another secondary effect that this recording head can be likewise applied to an ink supply system constituting a circulation ink path without changing a conformation. 
     As described above, according to the first modification, in the ink chamber  3 , the recording heads  4 - 1  to  4 - 4  are alternately arranged at the lengthwise positions in the carriage direction of the recording medium  21 , and the ink supply openings  41  are provided in both sides in the vicinity of the recording heads  4 - 1  to  4 - 4  with the central line between the alternately arranged recording heads  4 - 1  to  4 - 1  at the center. Therefore, this modification has specific characteristics obtained by providing the head-side ink supply openings  52   a  and  52   b  on both sides of the both end sections  51  of each of the recording heads  4 - 1  to  4 - 4  in the nozzle line direction in addition to the effect of uniforming a pressure loss of the ink supply paths leading to the recording heads  4 - 1  to  4 - 4 . 
     A description will now be given as to a second modification of the first and second embodiments of a ink supply system according to the present invention. 
       FIG. 8  shows a second modification of the first and second embodiments. 
     The second modification is the same as the first modification in that a head-side ink supply openings  52   a  and  52   b  are symmetrically arranged in a both end sections  51  of each of a recording heads  4 - 1  to  4 - 4  in a nozzle line direction with a central position of the nozzle line of each recording head at the center, and these openings can be connected with each connection path  42 . 
     Additionally, an ink chamber  3  according to this second modification is the same as the counterpart according to the first modification in that the recording heads  4 - 1  to  4 - 4  in a recording head group  4  are alternately provided at lengthwise positions in a carriage direction of a recording medium  21 , and that each ink supply opening  41  is provided in accordance with the two head-side ink supply openings  52   a  and  52   b  at the positions of the both end sections  51  in the nozzle line direction when providing the respective ink supply openings  41  on both sides in the vicinity of the recording heads  4 - 1  to  4 - 4  with a central line between the alternately arranged recording heads  4 - 1  to  4 - 4  at the center. 
     This second modification is different from the first modification in that a joint recording heads obtained by jointing a plurality of recording heads are arranged as the recording heads  4 - 1  to  4 - 4  which are alternately arranged at the lengthwise positions in the carriage direction of the recording medium  21  in the ink chamber  3  according to the first modification. In the joint recording heads, nozzles are shifted from each other in the nozzle line direction with a half of a nozzle pitch. 
     The joint recording heads are jointed and arranged back to back through a base plate  53 , thereby doubling a resolving power. 
     Therefore, this second modification is the same as the first modification except that each head-side ink supply opening  52   b  is adjacent to each head-side ink supply opening  52   a  by joint and each connection path  42  is connected with these openings. 
     As described above, according to the second modification, in addition to the same effect as that of the first modification, the present invention can be likewise applied to the joint recording heads in order to improve a resolving power. 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general invention concept as defined by the appended claims and their equivalents.