Patent Publication Number: US-11396179-B2

Title: Head unit

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims priority from Japanese Patent Application No. 2019-226447, filed on Dec. 16, 2019, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     Field of the Invention 
     The present disclosure relates to a head unit having a buffer chamber. 
     Description of the Related Art 
     There is a publicly known print head of a line type having a plurality of recording heads arranged in a row. In this print head, the plurality of recording heads are provided with tanks, respectively, each of which is called a head tank and each of which temporarily stores an ink. The head tanks are provided with discharge ports and supply ports, respectively. The discharge ports of head tanks, which are included in the head tanks and which are adjacent to each other are connected to each other, and the supply ports of the adjacent head tanks are connected to each other. 
     SUMMARY 
     In the above-described print head, since both of the discharge ports and the supply ports provided in the head tanks, respectively, extend vertically upward, tubes connected to the discharge ports and the supply ports are connected thereto vertically upward. This leads to an increase in the size in the vertical direction of the print head. 
     The present disclosure has been made in view of the circumstances described above, and one of the objects thereof is to provide a means for achieving a miniaturization of a head unit by improving the space-efficiency of tanks arranged inside the head unit and tubes connected to the tanks. 
     According to a first aspect of the present disclosure, there is provided a head unit including: a plurality of head modules each including: channel units each including a pressure chamber, a nozzle communicating with the pressure chamber, and a channel communicating with the pressure chamber; energy-applying mechanisms, each of the energy-applying mechanisms being configured to apply a discharge pressure to a liquid in the pressure chamber of one of the channel units; supply buffer chambers, each of the supply buffer chambers being configured to temporarily store the liquid which is to be supplied to one of the channel units, and each of the supply buffer chambers including two ports; and return buffer chambers, each of the return buffer chambers being configured to temporarily store the liquid which is discharged from one of the channel units, and each of the return buffer chambers including two ports; a plurality of first tubes connected to the ports of the supply buffer chambers, respectively; and a plurality of second tubes connected to the ports of the return buffer chambers, respectively. The supply buffer chambers of the plurality of head module are connected in series via the plurality of first tubes. The return buffer chambers of the plurality of head modules are connected in series via the plurality of second tubes. 
     According to a second aspect of the present disclosure, there is provided a head unit including: a plurality of head modules arranged side by side in a first direction orthogonal to a vertical direction, each of the plurality of head modules including: channel units each including a pressure chamber, a nozzle communicating with the pressure chamber, and a channel communicating with the pressure chamber; energy-applying mechanisms, each of the energy-applying mechanisms being configured to apply a discharge pressure to a liquid in the pressure chamber of one of the channel units; supply buffer chambers, each of the supply buffer chambers being configured to temporarily store a liquid which is to be supplied to one of the channel units, and each of the supply buffer chambers including two ports; and return buffer chambers, each of the return buffer chambers being configured to temporarily store the liquid which is discharged from one of the channel units, and each of the return buffer chambers including two ports; a plurality of first tubes connected to the ports of the supply buffer chambers, respectively; and a plurality of second tubes connected to the ports of the return buffer chambers, respectively. Each of the supply buffer chambers includes two side surfaces orthogonal to the first direction, and the two ports are arranged at upper parts in the vertical direction of the two side surfaces, respectively. Each of the return buffer chambers includes two side surfaces orthogonal to the first direction, and the two ports are arranged at upper parts in the vertical direction of the two side surfaces, respectively. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a printer  10  in a state that a cover  16  is opened. 
         FIG. 2  is a schematic view depicting the inner structure of the printer  10 . 
         FIG. 3  is a schematic view of a print head  24 . 
         FIG. 4  is a schematic view for explaining a circulation path or route of an ink. 
         FIG. 5  is a schematic view depicting a cross section of a joint  251   a.    
         FIG. 6  is a schematic view depicting a cross section of an ink-jet head  100 . 
         FIG. 7  is a perspective view of a head module  240 . 
         FIG. 8  is a schematic view depicting a cross section of the head module  240 . 
         FIG. 9  is a schematic view of a heat sink  360 . 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     In the following, a printer  10  according to an embodiment of the present disclosure will be described. Note that the embodiment which is to be explained below is merely an example of the present disclosure; it is needless to say that the embodiment can be appropriately changed without changing the gist of the present disclosure. Further, in the following explanation, advancement or movement (progress) directed from a starting point to an end point of an arrow is expressed as an “orientation”, and going forth and back on a line connecting the starting point and the end point of the arrow is expressed as a “direction”. Further, in the following explanation, the up-down direction is defined, with a state in which the printer  10  is installed usably (a state of  FIG. 1 ) as the reference; the front-rear direction is defined, with a side on which a discharge port  13  is provided is defined as a front side (front surface); and the left-right direction is defined, with the printer  10  as seen from the front side (front surface). 
     &lt;Outer Configuration of Printer  10 &gt; 
     As depicted in  FIG. 1 , the printer  10  records an image on a roll body  11  (see  FIG. 2 ), etc., in the ink-jet recording system. A casing  14  of the printer  10  has a substantially rectangular parallelepiped shape of which internal space is defined or partitioned by walls. The casing  14  has: a right wall  35  and a left wall  36  located apart from each other in the left-right direction; an upper wall  33  and a lower wall  34  located apart from each other in the up-down direction, and connecting the right wall  35  and the left wall  36  to each other; and a front wall  31  and a rear wall  32  located apart from each other in the front-rear direction, and connecting the upper wall  33  and the lower wall  34  to each other. 
     The casing  14  has a size placable or arrangable on a table or desk. That is, the printer  10  is suitable to be used by being placed on the table or desk. Of course, the printer  10  may be used while being placed on a floor surface. 
     The front wall  31  of the casing  14  has a discharge port  13  formed in the front wall  31 , penetrating through the front wall  31  and communicating with the inner space. The discharge port  13  is located at an upper right part of the front wall  31 . An operation panel  17  (an example of an “input part”) is located in the front wall  31  at a location left to the discharge port  13 . The operation panel  17  includes, for example, a display, an input key, etc. A user performs input, via the operation panel  17 , for operating the printer  10  or for confirming a variety of kinds of settings. 
     A cover  16  is provided in the front wall  31 , at a location below the operation panel  17 . As depicted in  FIG. 1 , the cover  16  is opened by rotating about a rotational axis along the left-right direction at a lower end of the cover  16 . In a case that the cover  16  is opened, the inner space of the casing  14  is exposed via an opening  12 . A main tank  70  is positioned at a location behind or on the rear side of the cover  16 . An ink is stored in the main tank  70 . The main tank  70  is of a cartridge type which is attachable and removable with respect to the casing  14 . The ink is supplied from the main tank  70  through a non-illustrated tube to the print head  24  (see  FIG. 2 ). 
     The ink is a liquid containing a pigment, etc. The ink has a viscosity suitable for uniformly dispersing the pigment. The pigment is a component which serves as the color of the ink. 
     As depicted in  FIG. 1 , a holder  90  which holds the roll body  11  is inserted into the front wall  31  at a location on the right side of the cover  16 . The holder  90  is provided with a handle  98 . For example, in a case of replacing the roll body  11 , etc., the user can grasp the handle  98  and pull the holder  90  frontward in the front-rear direction. 
     The right wall  35  is provided with a window  39 . The window  39  is a translucent member which closes a through hole penetrating through the right wall  35 . The window  39  is provided for visually observing the roll body  11  located in the inner space of the casing  14 , from the outside of the casing  14 . 
     &lt;Holder  90 &gt; 
     As depicted in  FIG. 2 , the holder  90  has a holder casing  91 , a spindle  92 , and nip rollers  93  and  94 . The holder casing  91  has a holder front wall  95 , a holder lower wall  96 , and a holder side wall  97 . The holder side wall  97  is provided with the spindle  92  extending along the left-right direction. The spindle  92  supports the roll body  11 . The spindle  92  is rotated by the rotation transmitted from a motor (not depicted in the drawings) located in the inner space of the casing  14 . Accompanying with the rotation of the spindle  92 , the roll body  11  supported by the spindle  92  also rotates. The nip roller  93  is provided on the holder lower wall  96 , and the nip roller  94  is provided at a location above the nip roller  93 . A sheet drawn from the roll body  11  supported by the spindle  92  passes between the nip rollers  93  and  94 . The nip roller  93  is subjected to the drive transmittance from the motor (not depicted in the drawings) located in the inner space of the casing  14 . In this situation, the sheet sandwiched between the nip rollers  93  and  94  is fed backward toward a conveyance path  22  (to be described later on). 
     &lt;Inner Configuration of Printer  10 &gt; 
     As depicted in  FIG. 2 , guide rollers  20  and  21 , a first conveying roller pair  54 , a second conveying roller pair  55 , the print head  24  (correspondence to a “head unit” of the present disclosure), a platen  25 , and the main tank  70  are arranged in the inner space of the casing  14 . Although not depicted in  FIG. 2 , it is allowable that other members such as: a maintenance unit such as a cap which covers a nozzle surface of the print head  24 , a wiper which wipes the nozzle surface, etc., a control board, a power source circuit, etc., may be arranged in the inner space of the casing  14 . 
     The print head  24  is provided with three head modules  240 A,  240 B and  240 C (see  FIG. 3 ). As will be described later, the three head modules  240 A,  240 B and  240 C have a same structure, and are collectively referred to as head modules  240 , in some cases. In each of the head modules  240 , a plurality of nozzles  30  are arranged side by side in the left-right direction. From the plurality of nozzles  30 , ink droplets of the ink are discharged or ejected downward toward the platen  25 . The configurations of the print head  24  and the head modules  240  will be described in detail later. 
     &lt;Conveyance Path  22 &gt; 
     As depicted in  FIG. 2 , a conveyance path  22  is formed to extend from a location in the vicinity of a rear end of the holder  90 , then to the guide roller  20 , the guide roller  21 , and up to the discharge port  13 . The conveyance path  22  is curved in a range or area from the location in the vicinity of the rear end of the holder  90  up to the guide roller  21 . Between the guide roller  21  and the discharge port  13 , the conveyance path  22  extends substantially linearly along the front-rear direction. The conveyance path  22  is defined by guide members which are located to be away from each other in the up-down direction, the guide roller  21 , the print head  24 , the platen  25 , etc. In the conveyance path  22  at a part thereof between the guide roller  21  and the discharge port  13 , the forward orientation is a conveyance orientation. 
     As depicted in  FIG. 2 , the first conveying roller pair  54  is provided on the conveyance path  22 , on the upstream side of the print head  24  in the conveyance orientation. The first conveying roller pair  54  includes a first conveying roller  60  and a pinch roller  61 . The second conveying roller pair  55  is provided on the conveyance path  22 , on the downstream side of the print head  24  in the conveyance orientation. The second conveying roller pair  55  has a second conveying roller  62  and a pinch roller  63 . The first conveying roller  60  and the second conveying roller  62  are rotated by the rotation transmitted thereto by the motor (not depicted in the drawings). The pinch roller  61  is urged toward the first conveying roller  60 . The pinch roller  63  is urged toward the second conveying roller  62 . The first conveying roller pair  54  and the second conveying roller pair  55  convey the sheet in the conveyance orientation by rotations of the first conveying roller  60  and the second conveying roller  62  in a state that the sheet extending from the roll body  11  is held or pinched between the respective rollers constructing the first and second conveying roller pairs  54  and  55 . 
     As depicted in  FIG. 2 , the print head  24  and the platen  25  are located in the conveyance path  22  at a part thereof between the first conveying roller pair  54  and the second conveying roller pair  55 . 
     As depicted in  FIG. 2 , the platen  25  is positioned at a location below the print head  24 . The upper surface of the platen  25  is parallel to a plane in which each of the plurality of nozzles  30  of the print head  24  are opened. The size along the left-right direction of the upper surface of the platen  25  is greater than the size along the left-right direction of the roll body  11 . The platen  25  supports, on the upper surface thereof, the sheet conveyed by the first conveying roller pair  54  and the second conveying roller pair  55 . Although not depicted in  FIG. 2 , it is allowable that the sheet is attracted to the upper surface of the platens  25  by negative pressure or static electricity. Since the platen  25  is not attached to the holder  90 , even if the holder  90  is pulled out from the casing  14 , the platen  25  is located in the inner space of the housing  14  without moving. 
     &lt;Operation of Printer  10 &gt; 
     In the following, an image recording operation by the printer  10  will be explained. The printer  10  which receives print data controls the motor (not depicted in the drawings) so as to rotate the spindle  92 , the nip roller  93 , the guide rollers  20  and  21 , the first conveying roller  60  and the second conveying roller  62 . As a result, a forward end of the sheet of the roll body  11  is fed out to a location below or under the print head  24 . The fed sheet of the roll body  11  faces or is opposite to the printer head  24  at a surface, of the sheet, which is oriented radially outward in the roll. Then, the printer  10  discharges the ink from the print head  24  toward the sheet based on the print data while rotating the respective rollers. The ink droplets of the ink discharged from the print head  24  adhere to the sheet supported by the platen  25 . 
     In a case that the printer  10  determines that the printing based on the print data has been completed, the printer, according to this determination, causes the sheet to be conveyed until a part, of the sheet pulled out from the roll body  11 , on which the printing has been performed is conveyed from the discharge port  13  to the outside of the casing  14 , and then controls the motor (not depicted in the drawings) so as to stop the rotations of the spindle  92 , the nip roller  93 , the guide rollers  20  and  21 , the first conveying roller  60  and the second conveying roller  62 . 
     &lt;Print Head  24 &gt; 
     In the following, the flow of the ink in the print head  24  will be firstly explained, with reference to  FIGS. 3 and 4 , and then the construction of the head modules  240  will be explained. 
     &lt;Flow of Ink in Print Head  24 &gt; 
     As depicted in  FIG. 3 , the print head  24  includes the three head modules  240 A,  240 B and  240 C, a joint unit  250 , and a support substrate  260 . Note that the three head modules  240 A to  240 C have the same configuration, and are collectively referred to as the head modules  240  unless the three head modules  240 A to  240 C are to be distinguished from one another. The support substrate  260  is a substantially rectangular plate-shaped member, and three opening are formed (not depicted in the drawings) therein. Each of the three head modules  240  is attached to one of the three openings (not depicted in the drawings). At a location on the front side of the support substrate  260 , the two head modules  240 A and  240 C are arranged in the left-right direction. The head module  240 B is arranged between the two head modules  240 A and  240 C in the left-right direction, at a location on the rear side of the support substrate  260 . 
     The joint unit  250  is arranged at a location which is on the rear side or behind the head module  240 A and on the right side of the head module  240 B. As described above, since the head module  240 B is arranged between the two head modules  240 A and  240 C in the left-right direction, at the location on the rear side of the support substrate  260 , a right end of the head module  240 B is positioned to be shifted to the left side from a right end of the head module  240 A. The joint unit  250  is arranged in a space or gap behind the right end of the head module  240 A. Although not depicted in  FIG. 3 , a sub tank SBT (see  FIG. 4 , correspondence to a “tank” of the present disclosure) is arranged at a location below the joint unit  250 . The sub tank SBT is connected to the main tank  70  via a non-illustrated tube and a non-illustrated pump, and temporarily stores the ink supplied from the main tank  70  to the print head  24 . 
     As depicted in  FIGS. 3 and 4 , the joint unit  250  has four joints  251   a  to  251   d . The four joints  251   a  to  251   d  have a same structure, but are arranged in different positions from one another. In a case that the positions at which the four joints  251   a  to  251   d  are arranged, respectively, are not an issue, the four joints  251   a  to  251   d  are collectively referred to as joints  251 . The joint  251   a  is arranged on the front side of the joint  251   b , and the joint  251   c  is arranged on the front side of the joint  251   d . Further, the two joints  251   a  and  251   b  are arranged on the left side of the two joints  251   c  and  251   d.    
     Next, the shapes of the joints  251   a  to  251   d  will be explained, with reference to  FIG. 5 . Note that since all of these four joints  251   a  to  251   d  have the same shape, the following explanation will be made with the joint  251   a  as an example. The joint  251   a  has a first cylindrical part  252  extending in the up-down direction and a second cylindrical part  253  branched in the horizontal direction from the first cylindrical part  252 . Openings  252 U and  252 D are formed at an upper end and a lower end, respectively, of the first cylindrical part  252 . The opening  252 U is opened upward and the opening  252 D is opened downward. That is, the normal directions of the opening  252 U and  252 D are both parallel to the up-down direction. An opening  253 H is formed at a forward end of the second cylindrical part  253 . The opening  253 H is oriented in the horizontal direction. That is, the normal direction of the opening  253 H is parallel to the horizontal direction. 
     A tube T is fitted into the opening  252 U located on the upper end of the first cylindrical part  252 , and is fixed thereto by a fixing connector C. Note that the tube T can be similarly fitted to each of the opening  252 D located on the lower end of the first cylindrical part  252  and to the opening  253 H located at the forward end of the second cylindrical part  253 , and can be fixed thereto by the fixing connector C. Note that in a case that the tube T is not connected, a plug P may be fitted to and may seal the opening  252 D or the opening  253 H as depicted in  FIG. 5 . Note that in each of the joint  251   b  and the joint  251   c , the opening  253 H at the forward end of the second cylindrical part  253  is sealed with the plug P, and the tube T is fitted to the opening  252 D at the lower end of the first cylindrical part  252 , and each of the joint  251   b  and the joint  251   c  is communicated with the sub tank SBT (see  FIG. 4 ) via the tube T. Note that in  FIG. 4 , for the purpose of simplifying the drawing, the sub tank SBT is arranged behind the joint unit  250  (joints  251   b  and  251   c ) and the tubes T extend rearwardly. Actually, however, the sub tank SBT is arranged below the joint unit  250  (joints  251   b  and  251   c ), and the tube T fitted to the opening  252 D at the lower end of the first cylindrical part  252  of each of the joints  251   b  and  251   c  extends downward. The tubes T connecting the joints  251   b  and  251   c  and the sub tank SBT correspond to “first tubes” of the present disclosure. Further, in each of the joint  251   a  and the joint  251   d , the opening  252 D at the lower end of the first cylindrical part  252  is sealed with the plug P, and the tube T is fitted into the opening  253 H at the forward end of the second cylindrical part  253 , and each of the joints  251   a  and  251   d  is communicated with a valve V (see  FIG. 4 ) via the tube T. That is, the joint  251   a  and the joint  251   d  communicate with each other via the valve V. The tube T connecting the joints  251   a  and  251   d  and the valve V corresponds to a “third tube” of the present disclosure. As will be described later, in all of the joints  251   a  to  251   d , the tube T is fitted to the opening  242 U at the upper end of the first cylindrical part  252 , and each of the joints  251   a  to  251   d  communicates with a supply buffer chamber  241  or a return buffer chamber  242  (which will be described later on), via the tube T. The tubes T connecting the joints  251   a  to  251   d  and the supply buffer chamber  241  (or the return buffer chamber  242 ) correspond to “second tubes” of the present disclosure. 
     As depicted in  FIGS. 3 and 4 , each of the head modules  240  includes a supply buffer chamber  241  and a return buffer chamber  242 . Each of the supply buffer chamber  241  and the return buffer chamber  242  has a substantially rectangular parallelepiped shape. Note that a top surface  241 U of the supply buffer chamber  241  and a top surface  242 U of the return buffer chamber  242  are formed of a member which is deformable by the dynamic pressure of the ink flowing in the supply buffer chamber  241  and the return buffer chamber  242 . For example, the top surface  241 U of the supply buffer chamber  241  and the top surface  242 U of the return buffer chamber  242  can be formed by attaching a resin film to each of the supply buffer chamber  241  and the return buffer chamber  242 . The supply buffer chamber  241  has two ports  241   a  for the ink; each of the two ports  241   a  is arranged on one of a left side surface  241 L and a right side surface  241 R of the supply buffer chamber  241 . The port  241   a  provided on the left side surface  241 L of the supply buffer chamber  241  is arranged at a location behind the center in the front-rear direction of the left side surface  241 L, and the port  241   a  provided on the right side surface  241 R of the supply buffer chamber  241  is arranged at a location in front of the center in the front-rear direction of the right side surface  241 R. That is, the two ports  241   a  are arranged at positions diagonal to each other in the left side surface  241 L and the right side surface  241 R. Similarly, the return buffer chamber  242  has two ports  242   a  for the ink; each of the two ports  242   a  is arranged on one of a left side surface  242 L and a right side surface  242 R of the return buffer chamber  242 . The port  242   a  provided on the left side surface  242 L of the return buffer chamber  242  is arranged at a location in front of the center in the front-rear direction of the left side surface  242 L, and the port  242   a  provided on the right side surface  242 R of the return buffer chamber  242  is arranged at a location behind the center in the front-rear direction of the right side surface  242 R. That is, the two ports  242   a  are arranged at positions diagonal to each other in the left side surface  242 L and the right side surface  242 R. 
     As depicted in  FIG. 4 , the joint  251   b  is connected to the sub tank SBT. Further, as depicted in  FIGS. 3 and 4 , the joint  251   b  and the port  241   a  arranged on the right side surfaces  241 R of the supply buffer chamber  241  of the head module  240 B are connected via the tube T. The port  241   a  arranged on the left side surface  241 L of the supply buffer chamber  241  of the head module  240 B and the port  241   a  arranged on the left side surface  241 L of the supply buffer chamber  241  of the head module  240 C are connected via the tube T. The port  241   a  arranged on the right side surface  241 R of the supply buffer chamber  241  of the head module  240 C and the port  241   a  arranged on the left side surface  241 L of the supply buffer chamber  241  of the head module  240 A are connected via the tube T. Further, the port  241   a  arranged on the right side surface  241 R of the supply buffer chamber  241  of the head module  240 A and the joint  251   a  are connected via the tube T. As described above, the sub tank SBT, the joint  251   b , the supply buffer chambers  241  of the three head modules  240 , and the joint  251   a  are connected via the tubes T. This is called as a supply ink path. 
     As depicted in  FIGS. 3 and 4 , the joint  251   d  and the port  242   a  arranged on the right side surfaces  242 R of the return buffer chamber  242  of the head module  240 A are connected via the tube T. The port  242   a  arranged on the left side surface  242 L of the return buffer chamber  242  of the head module  240 A and the port  242   a  arranged on the right side surface  242 R of the return buffer chamber  242  of the head module  240 C are connected via the tube T. The port  242   a  arranged on the left side surface  242 L of the return buffer chamber  242  of the head module  240 C and the port  242   a  arranged on the left side surface  242 L of the return buffer chamber  242  of the head module  240 B are connected via the tube T. Further, the port  242   a  arranged on the right side surface  242 R of the return buffer chamber  242  of the head module  240 B and the joint  251   c  are connected via the tube T. Furthermore, as depicted in  FIG. 4 , the joint  251   c  and the sub tank SBT are connected via the tube T. As described above, the joint  251   d , the return buffer chambers  242  of the three head modules  240 , the joint  251   c , and the sub tank SBT are connected via the tubes T. This is called as a return ink path. 
     Moreover, as described above, the joints  251   a  and  251   d  are connected by the tube T via the valve V arranged at the outside of the print head  24  (see  FIG. 4 ). This creates an ink circulation path via which the ink from the sub tank SBT passes the supply ink path, the valve V and the return ink path and returns to the sub tank SBT. 
     &lt;Structure of Head Module  240 &gt; 
     Next, the construction of each of the head modules  240  will be explained, with reference to  FIGS. 6 to 8 . As depicted in  FIGS. 7 and 8 , each of the head modules  240  mainly includes: the supply buffer chamber  241  and the return buffer chamber  242  as described above, the ink-jet head  300 , a holder  350 , a heat sink  360 , a fan  370 , a trace member  381  having a driver IC  380 , and an intermediate substrate  390 . 
     As depicted in  FIGS. 7 and 8 , the holder  350  has an accommodating part  351  having a shape of a rectangular parallelepiped box of which upper surface is opened, and a projecting part  352  extending on both sides in the left-right direction at the upper surface of the accommodating part  351 . The holder  350 , as a whole, has a shape of a substantially rectangular parallelepiped flattened in the up-down direction. An accommodation space is formed inside the accommodating part  351 . A plurality of screw holes are formed in the projecting part  352  of the holder  350 , and the projecting part  352  of the holder  350  is fixed by being screwed to the support substrate  260  (see  FIG. 3 ). 
     As depicted in  FIG. 8 , the supply buffer chamber  241  and the return buffer chamber  242 , the ink-jet head  300 , the holder  350 , the heat sink  360 , the fan  370 , and the trace member  381  having the driver IC  380  are arranged in the accommodating space of the holder  350 . An opening (not depicted in the drawings) is formed in the lower surface of the holder  350 . The ink-jet head  300  is arranged on the side of the lower surface of the holder  350  so as to be exposed from the opening of the lower surface of the holder  350 . The supply buffer chamber  241  and the return buffer chamber  242  are arranged on the left side of the ink-jet head  300 . The ports  241   a  of the supply buffer chamber  241  and the ports  242   a  of the return buffer chamber  242  both extend in the horizontal direction (the left-right direction). The trace member  381  is arranged on the upper surface of the ink-jet head  300 . The trace member  381  is electrically connected to a piezoelectric element  304  (to be described later on) of the ink-jet head  300 . The trace member  381  drawn from the upper surface of the ink-jet head  300  to the left-right direction is bent into a shape of letter “U” in the up-down direction so that the driver IC  380  is exposed upward. The heat sink  360  is arranged at a location above the trace member  381 . The heat sink  360  makes contact with the driver IC  380 . The fan  370  is provided at a location above the heat sink  360 . Further, the intermediate substrate  390  is arranged so as to cover an upper part of the fan  370 . A power connector  391  of the fan  370 , etc., is arranged in the intermediate substrate  390 . The intermediate substrate  390  is positioned above the ports  241   a  of the supply buffer chamber  241  and the ports  242   a  of the return buffer chamber  242 . Note that the ports  241   a  of the supply buffer chamber  241  and the ports  242   a  of the return buffer chamber  242  are located above the projecting part  352  of the holder  350 . A gap is defined between the fan  370  and the intermediate substrate  390  in the up-down direction. 
     &lt;Ink-Jet Head  300 &gt; 
     The ink-jet head  300  has a nozzle plate  301 , a channel member  302 , a vibration plate  303  and a piezoelectric element  304 , and has a structure in which the nozzle plate  301 , the channel member  302 , the vibration plate  303  and the piezoelectric element  304  are overlaid or stacked in the up-down direction. Note that the channel member  302  may be a stacked body (laminated body) obtained by stacking a plurality of plates in the up-down direction. A plurality of nozzles  305  are formed in the nozzle plate  301 . Note that a combination of the channel member  302  and the nozzle plate  301  corresponds to a “channel unit” of the present disclosure. A supply manifold  310 , a plurality of supply channels  311 , a return manifold  312 , a plurality of return channels  313 , a plurality of pressure chambers  320  and a plurality of descenders  321  are formed in the channel member  302 . The plurality of nozzles  305 , the plurality of descenders  321 , the plurality of pressure chambers  320 , the plurality of supply channels  311  and the plurality of return channels  313  are a plurality of individual channels provided corresponding to the plurality of nozzles  305 , respectively. Note that although the plurality of individual channels are arranged side by side in the left-right direction, only a certain individual channel among the plurality of individual channels is depicted in  FIG. 6 . The vibration plate  303  is stacked on the channel member  302 , and the vibration plate  303  covers the supply manifold  310 , the plurality of pressure chambers  320  and the return manifold  312 . A plurality of pieces of the piezoelectric element  304  are aligned on the vibration plate  303 . A combination of the plurality of piezoelectric elements  304  and the vibration plate  303  corresponds to an “energy-applying mechanism” of the present disclosure. 
     The supply manifold  310  and the return manifold  312  are a common channel commonly provided for the plurality of individual channels. The supply manifold  310  supplies the ink to each of the plurality of nozzles  305  via one of the plurality of supply channels  311  and one of the plurality of pressure chambers  320 . The return manifold  312  is a space communicating with a channel. The return manifold  312  communicates with each of the plurality of descenders  321  via one of the plurality of discharge channels  313 , and the ink which has not been ejected or discharged from the nozzle  305  flows into the return manifold  312 . The supply manifold  310  communicates with the supply buffer chamber  241 , and the ink is supplied from the supply buffer chamber  241  to the supply manifold  310 . The return manifold  312  communicates with the return buffer chamber  242 , and the ink is recovered to the return buffer chamber  242 . 
     &lt;Heat Sink  360 &gt; 
     As depicted in  FIG. 9 , the heat sink  360  is substantially box-shaped of which upper surface is opened, and has a base part  361  which is substantially rectangular plate-shaped and four fins  362  to  365  standing upward from end parts on the four sides, respectively, of the base part  360 . The fin  364  corresponds to a “first fin” of the present disclosure, the fin  362  corresponds to a “second fin” of the present disclosure, the fin  363  corresponds to a “third fin” of the present disclosure, and the fin  365  corresponds to a “fourth fin” of the present disclosure. The fin  362  is located at a left end of the base part  361 , and the fin  363  is located at a right end of the base part  361 . The fin  364  is located at a rear end of the base part  361 , and the fin  365  is located at a front end of the base part  361 . The lower ends of the fins  362  and  362  are connected to the base part  361  in their entirety. In contrast, a part of the lower end of each of the fin  364  and  365  is connected to the base part  361 . In other words, constricted parts or neck parts are provided on the both sides, respectively, in the left-right direction, of the part, of the lower end of each of the fins  364  and  365 , which is connected to the base part  361 . Further, cutouts (notches)  361   a  having a substantially semicircular shape are provided on both sides, respectively, in the left-right direction, of a part, of the base part  361 , connected to the lower end of each of the fins  364  and  365 . A front end of the fin  362  and a left end of the fin  365  are not connected, and a gap is defined between the fin  362  and the fin  365 . Similarly, gaps are defined between the fins  365  and  363 , between the fins  363  and  364 , and between the fins  364  and  362 . That is, the gaps are defined in the four corners, respectively, of the heat sink  360 . 
     As depicted in  FIG. 7 , openings  350   a  are formed in a front side surface and a rear side surface, respectively, of the holder  350 , at positions overlapping in the front-rear direction with four gaps, respectively, defined in the four corners of the heat sink  360 . Further, in a case that the head modules  240  are arranged in the support substrate  260  as depicted in  FIG. 3 , the head modules  240  are arranged such that the openings  350   a  of head modules  240  included in the head modules  240  and adjacent to each other in the front-rear direction do not overlap with each other in the left-right direction. 
     As depicted in  FIG. 8 , the base part  361  of the heat sink  360  makes contact with the driver IC  380 . Note that it is not necessarily indispensable that the base part  361  of the heat sink  360  and the driver IC  380  are in direct contact with each other; it is allowable, for example, that a thermal conductive material such as a thermal conductive grease may be interposed between the base part  361  of the heat sink  360  and the driver IC  380 . Further, a gap is defined between the fins  362  to  365  of the heat sink  360  and the holder  350 . The heat sink  360  is fixed to the ink-jet head  300  in a state that a gap is defined in the up-down direction between the base part  361  and the ink-jet head  300 . The heat of the heat sink  360  is dissipated through these gaps. Note that the fan  370  is fixed to the heat sink  360 , as will be described later on. The heat sink  360  is fixed to the ink-jet head  300  via a vibration absorber (for example, sponge, rubber, etc.,) which absorbs the vibration generated in a case that the fan  370  is energized so that the vibration is not transmitted to the ink-jet head  300 . Alternatively, it is allowable that the heat sink  360  is fixed to the ink-jet head  300  in a state that sufficient play between the heat sink  360  and the ink-jet head  300  is secured so as to prevent the vibration generated in a case that the fan  370  is energized from being transmitted to the ink-jet head  300 . 
     &lt;Fan  370 &gt; 
     As depicted in  FIGS. 7 and 8 , the fan  370  is arranged in an inner space, of the heat sink  360 , which is surrounded by the base part  361  and the fins  362  to  365 , and the fan  370  is secured to the base part  361 . Note that the fan  370  is fixed to the base part  361  in a state that a gap in the up-down direction is secured between the fan  370  and the base part  361 . A gap is also defined between the fan  370  and each of the fins  362  to  365 . 
     Since the air flow is generated by the rotation of the blades of the fan  370 , the air flow is not generated from a rotation shaft part  370   a  of the blades. Therefore, the fan  370  is arranged so that the rotating shaft part  370   a  of the blades of the fan  370  and the heat source do not overlap in the up-down direction. In this embodiment, since the driver IC  380  is the primary source of heat, the fan  370  is arranged such that the rotating shaft part  370   a  of the blades of the fan  370  does not overlap with the driver IC  380  in the up-down direction. Further, as depicted in  FIG. 8 , the top surface of the fan  370  is located above the upper surface of the projecting part  352  of the holder  350 . 
     Effects of Embodiment 
     In the above-described embodiment, in the plurality of head modules  240 , an odd-numbered head module  240  and an even-numbered head module  240  counted from one side in the left-right direction are aligned in a row in the left-right direction, and as a whole, the plurality of head modules  240  are arranged in a staggered manner. In the following explanation, “being Nth counted from the right” is simply referred to as “Nth”. Further, a row of an odd-numbered ((2N−1)th) head module  240  is called as an odd-numbered row, and a row of an even-numbered (2Nth) head module  240  is called as an even-numbered row. The supply buffer chambers  241  of the head modules  240  of the odd-numbered row are connected to each other by the tube. In this embodiment, although there is only one head module  240  in the even-numbered row, in a case that there are a plurality of head modules  240  in the even-numbered row, the supply buffer chambers  241  of the even-numbered head modules  240  can be similarly connected to each other by the tube. Further, the supply buffer chamber  241  of a head module  240  located closest to the other side in the left-right direction among the head modules  240  in the odd-numbered row, and the supply buffer chamber  241  of a head module  240  located closest to the other side in the left-right direction among the head modules  240  of the even-numbered row are connected by the tube. Regarding the return buffer chambers  242  are also similar to the supply buffer chambers  241 . 
     In this manner, by arranging the plurality of head modules  240  and connecting the supply buffer chambers  241  to each other by the tubes, and by connecting the return buffer chambers  242  to each other by the tubes, it is possible to make the size in the left-right direction of the print head  24  to be compact. Further, since the plurality of head modules  240  are arranged in the staggered manner as described above, it is possible to provide the space between the first head module  240 A and the second head module  240 B. Further, in this embodiment, the joint unit  250  is provided in the space between the first head module  240 A and the second head module  240 B. Each of the joints  251  provided in the joint unit  250  has the first cylindrical part  252  extending in the up-down direction. In the above-described embodiment, the upper end of the first cylindrical part  252  is connected to the supply buffer chamber  241  or the return buffer chamber  242  of the head module  240  via the tube, and the lower end of the first cylindrical part  252  is connected to the sub tank SBT. In this case, it is easy to arrange the sub tank SBT below the joint unit  250 , thereby making it possible to make the size in the horizontal direction (the left-right direction and the front-rear direction) of the print head  24  to be compact. Further, the opening  252 U at the upper end of the first cylindrical part  252  is opened upward, and the opening  252 U is positioned above the second cylindrical part  253 . Therefore, even in a case that the tube T fitted to the opening  252 U is removed, there is no such a fear that the ink might flow out from the opening  252 U, since the liquid level of the ink is located below the opening  252 U which is located at the upper end of the first cylindrical part  252 . 
     In the above-described embodiment, the joints  251   a  and  251   d  are connected by the tube via the valve V arranged at the outside of the print head  24 . Since the valve V is arranged at the outside of the print head  24 , the size in the horizontal direction of the print head  24  can be made compact as compared to a case wherein the valve V is arranged in the inside of the print head  24 . By driving the pump P in a state that the valve V is released so as to circulate the ink in the circulation path of the ink passing through the supply ink channel, the valve V and the return ink channel, it is possible to remove the air accumulated in the supply buffer chamber(s)  241  and the return buffer chamber(s)  242 . Further, in a case of performing the printing, by closing the valve V, it is possible to stop the circulation of the ink in the circulation path of the ink passing through the supply ink channel, the valve V and the return ink channel. In this case, it is possible to supply a sufficient amount of the ink to the ink circulation path from the supply ink channel and up to the return ink channel passing through the ink-jet head  300  of each of the head modules  240 . As a result, since the sufficient amount of the ink can be supplied to each of the ink-jet heads  300 , it is possible to suppress any lowering in the image quality due to any shortage of the ink in each of the ink-jet heads  300 . 
     In the above-described embodiment, the fan  370  is arranged in the space defined or formed by the base part  361  and the four fins  362  to  365  standing upward from the end parts on the four sides, respectively, of the base part  361  of the heat sink  360 . That is, the heat sink  360  and the fan  370  are stacked so as to overlap with each other in the up-down direction. By arranging the heat sink  360  and the fan  370  in this manner, the print head  24  can be made compact in the up-down direction. 
     In the above-described embodiment, the gap is defined between adjacent fins, which is included in the four fins  362  to  365  of the heat sink  360  and which are adjacent to each other. That is, the gaps are defined in the four corners, respectively, of the heat sink  360 . Since the air can move through these gaps, the air warmed by the heat sink  360  is allowed to escape to the outside of the heat sink  360 . Further, the openings  350   a  are formed in the front side surface and the rear side surface of the holder  350 , at the positions overlapping in the front-rear direction with the four gaps, respectively, defined in the four corners of the heat sink  360 . As a result, the air warmed by the heat sink  360  is allowed to escape to the outside of the head modules  240  via the opening  350   a . Further, in a case that the head modules  240  are arranged in the support substrate  260 , the openings  350   a  of the head modules  240 , which is included in the head modules  240  and which are adjacent to each other in the front-rear direction, are arranged so as not to overlap with each other in the left-right direction. With this, in a certain head module  240 , it is possible to suppress such a situation that the air warmed by the heat sink  360  might enter into another head module  240  adjacent to the certain head module  240 . 
     In the above-described embodiment, the fan  370  is fixed to the base part  361  in a state that the gap in the up-down direction is secured between the fan  370  and the base part  361 , and the gap is also defined between the fan  370  and each of the fins  362  to  365 . With this, since it is possible to move the air through these gaps, it is possible to increase the cooling performance of the fan  370 . Further, the constricted parts or neck parts are provided on the both sides, respectively, in the left-right direction, of the part, of the lower end of each of the fins  364  and  365 , which is connected to the base part  361 . With this, since the flow of air generated by the fan  370  can be guided to the lower side of the heat sink  360  via the constricted parts, it is possible to enhance the heat radiation effect of the lower surface of the base part  361 . 
     In the above-described embodiment, the heat sink  360  is fixed to the ink-jet head  300 , via the vibration absorber (for example, the sponge, the rubber, etc.,) which absorbs the vibration, or in a state that the sufficient play is secured between the heat sink  360  and the ink-jet head  300 . This reduce such a situation that the vibration generated in a case that the fan  370  is energized is transmitted to the ink-jet head  300 , thereby making it possible to enhance the landing accuracy at the time of performing printing by the ink-jet head  300 . 
     In the above-described embodiment, the fan  370  is arranged in the heat sink  360  so that the rotating shaft part of the blades of the fan  370  does not overlap, in the up-down direction, with the driver IC  380  as the heat source. With this, it is possible to utilize the flow of air, caused by the rotation of the blades of the fan  370 , efficiently for the heat radiation of the driver IC  380 . Further, the top surface of the fan  370  is located above the upper surface of the projecting part  352  of the holder  350 . With this, it is possible to suppress such a situation that the air flowing upward from the projecting part  352  of the holder  350  is sucked again into the fan  370 . That is, it is possible to suppress such a situation that the warmed air which should be exhausted is sucked again into the fan  370 . 
     In the above-described embodiment, the holder  350 , as a whole, has a shape of a substantially rectangular parallelepiped flattened in the up-down direction. Further, the ports  241   a  of the supply buffer chamber  241  and the ports  242   a  of the return buffer chamber  242  both extend in the horizontal direction (the left-right direction). Therefore, the tubes can be horizontally connected to the ports  241   a  of the supply buffer chamber  241  and the ports  242   a  of the return buffer chamber  242 , respectively. With this, the height in the up-down direction of the head module  240  can be made compact. 
     Further, the ports  241   a  of the supply buffer chamber  241  and the ports  242   a  of the return buffer chamber  242  are arranged above the projecting part  352  of the holder  350 . Therefore, in a case that the tubes are to be connected to the ports  241   a  of the supply buffer chamber  241  and the ports  242   a  of the return buffer chamber  242 , the projecting part  352  does not interfere with the tubes. Accordingly, since the tubes can be connected horizontally, the discharge resistances in the tubes can be suppressed. This is useful in discharging of the ink at a high frequency. 
     In this embodiment, the intermediate substrate  390  is arranged so as to extend or expand in the horizontal direction. With this, the height in the up-down direction of the head module  240  can be made compact. Further, the intermediate substrate  390  is arranged so as to be positioned above the ports  241   a  of the supply buffer chamber  241  and the ports  242   a  of the return buffer chamber  242 . Therefore, in a case that the tubes are to be connected to the ports  241   a  of the supply buffer chamber  241  and the ports  242   a  of the return buffer chamber  242 , the intermediate substrate  390  does not interfere with the tubes. Therefore, since the tube can be connected horizontally, discharge resistances in the tube can be suppressed. This is useful in discharging of the ink at a high frequency. Further, since the intermediate substrate  390  is positioned above the ports  241   a  of the supply buffer chamber  241  and the ports  242   a  of the return buffer chamber  242 , even if the ink leaks from the tubes extending horizontally from the ports  241   a  of the supply buffer chamber  241  and the ports  242   a  of the return buffer chamber  242 , there is no such a fear that the ink might adhere to the electrical component(s) arranged in the intermediate substrate  390 . Note that since the power connector  391  of the fan  370  is arranged in the intermediate substrate  390 , it is easy to route the trace from the fan  370 . 
     In the above-described embodiment, the plurality of supply buffer chambers  241  are connected in series with each other, and the plurality of return buffer chambers  242  are also connected in series with each other. Therefore, the number of the tubes can be reduced and the print head  24  can be made compact, as compared to such a case that the plurality of supply buffer chambers  241  are connected in parallel with each other or such a case that the plurality of return buffer chambers  242  are connected in parallel with each other. 
     In the above-described embodiment, the two ports  241   a  of each of the supply buffer chambers  241  are arranged at diagonal positions in the left side surface  241 L and the right side surface  241 R. Similarly, the two ports  242   a  of each of the return buffer chambers  242  are arranged at the positions diagonal to each other in the left side surface  241 L and the right side surface  241 R. As compared to such a case that the two ports  241   a  (two port  242   a ) are arranged at the same positions in the left-right direction, it is possible to stir the ink inside the supply buffer chamber  241  and the return buffer chamber  242 , thereby making it possible to reduce any stagnation of the ink inside the supply buffer chamber  241  and the return buffer chamber  242 , to prevent the ink from becoming viscous, and to prevent any setting or sedimentation of the particles (pigment, etc.,) in the ink. In a case that the stagnation of the inks is reduced, it is possible to easily discharge or exhaust the air inside the supply buffer chamber  241  and the return buffer chamber  242 . Further, in a case that the supply buffer chambers  241  are connected to each other by the tubes and that the return buffer chambers  242  are connected to each other by the tubes, a required length of the tube is longer than another case that the two ports  241   a  (two ports  242   a ) are arranged at the same position in the left-right direction. Therefore, since a margin can be provided in the length of the tube, it is possible to absorb any expansion or contraction which might occur in the tube caused due to, for example, any change in the temperature of the ink, etc. 
     In the above-described embodiment, the two ports  241   a  and the two ports  242   a  both extend in the left-right direction and are located at the upper parts of the side surfaces of the supply buffer chamber  241  and at the upper parts of the side surfaces of the return buffer chamber  242 , respectively. Note that in the above-described embodiment, the plurality of supply buffer chambers  241  are connected in series, and the plurality of return buffer chambers  242  are also connected in series. However, in a case that the two ports  241   a  and the two ports  242   a  both extend in the left-right direction and are located at the upper parts of the side surfaces of the supply buffer chamber  241  and at the upper parts of the side surfaces of the return buffer chamber  242 , respectively, it is not necessarily indispensable that the supply buffer chambers  241  are connected to each other in series and that the return buffer chambers  242  are connected to each other in series. For example, the supply buffer chambers  241  may be connected to each other in parallel, and/or the return buffer chambers  242  may be connected to each other in parallel. In a case that the two ports  241   a  and the two ports  242   a  both extend in the left-right direction, the tubes can be connected horizontally to the two ports  241   a  and the two ports  242   a . Therefore, the print head  24  can be made compact in the up-down direction. Further, in the case that the two ports  241   a  and the two ports  242   a  are located at the upper parts of the side surfaces of the supply buffer chamber  241  and at the upper parts of the side surfaces of the return buffer chamber  242 , respectively, it is possible to efficiently exhaust or discharge the air accumulated at the upper part of the supply buffer chamber  241  and at the upper part of the return buffer chamber  242 . 
     In the above-described embodiment, the top surfaces of the supply buffer chamber  241  and the return buffer chamber  242  are formed by the deformable member (elastic member). With this, it is possible to attenuate any fluctuation in the pressure of the ink in the supply buffer chamber  241  and the return buffer chamber  242 . Note that the fluctuation in the pressure of the ink can be exemplified, for example, by a pulsation in a case that the ink is circulated, an inertia pressure during the printing, etc. The pulsation in the case that the ink is circulated might be generated, for example, by the pump. Further, after a large amount of ink is ejected as in a case of performing solid printing, etc., a large inertial pressure might be applied when the discharge of the ink is stopped, in some cases. 
     In the above-described embodiment, the head module  240  located at the downstream-most side in the supply ink channel (namely, the head module  240 A) communicates with the sub tank SBT via the valve V and the return ink channel. With this, since the ink is circulated, it is possible to remove the air bubble in the ink while reducing a waste-liquid amount of the ink, to suppress the increase in the viscosity of the ink and to suppress any sedimentation of the pigment, etc., in the ink. Note that in the above-described embodiment, although the head module  240  located at the downstream-side of the supply ink channel (namely, the head module  240 A) communicates with the sub tank SBT via the valve V and the return ink channel, it is allowable that the head module  240  located at the downstream-side of the supply ink channel (namely, the head module  240 A) is directly connected to the sub tank SBT via the valve V. 
     Modified Embodiment 
     The embodiment as described above is merely an example, and may be changed as appropriate. For example, the number, arrangement, shape, pitch, etc., of the pressure chamber can be arbitrarily set. Further, the number of head module  240  is not limited to being three, and may be not less than four. 
     In the above-described embodiment, although the heat sink  360  has the four fins  362  to  365 , the present disclosure is not limited to or restricted by such a an aspect. It is allowable that the heat sink  360  has at least three fins, and that the plane direction of one of the fins is a direction crossing the plane directions of the other two fins. 
     In the above-described embodiment, the top surface of the fan  370  is located above the upper surface of the projecting part  352  of the holder  350 . However, the present disclosure is not limited to such an aspect, and it is allowable that the top surface of the fans  370  is positioned above at least one of the projecting part  352  of the holder  350  and the upper surfaces of the fins of the heat sink  360 . 
     Further, it is allowable to appropriately change the layout of the discharge port  13 , the cover  16 , the operation panel  17 , and the holder  90  in the front wall  31  of the printer  10 . Further, it is allowable to arrange the discharge port  13 , the cover  16 , or the operating panel  17  in a location which is different from the front wall  31 . 
     Furthermore, the main tank  70  is not limited to a tank which is configured to store an ink of only one color which is black; the main tank may be, for example, a tank which is configured to store inks of four colors which are black, yellow, cyan, and magenta, respectively. In order to accelerate drying of the ink, it is allowable to provide a heater, which is configured to heat at least one of the sheet and the ink, on the downstream side in the conveyance direction of the print head  24 . In this case, a so-called latex ink can also be used as the ink. The latex ink is an ink containing resin fine particles configured to cause a pigment to adhere to a sheet and another publicly known component. As the sheet to which the latex ink adheres passes a location below or under the heater, the resin fine particles undergoes the glass transition by being heated by the heater. Further, the sheet which has passed the location below the heater is cooled, whereby curing the resin which has undergone the glass transition. With this, the ink is fixed to the sheet. Further, as the ink, it is allowable to use an ink containing a ultraviolet-curable resin. In such a case, an ultraviolet irradiator is provided on the downstream side of the print head  24 . 
     Furthermore, the main tank  70  may also be secured to the casing  14 , rather than being of the cartridge-type. In such a case, an inlet port is formed in the main tank  70 , and the main tank  70  is replenished with the ink through the inlet port. 
     In the above-described embodiment, although the print head  24  which performs printing on the sheet by the ink-jet system using the piezoelectric element  304  and the vibration plate  303  as the piezoelectric actuator is used as the printing part, it is allowable to adopt, instead of this, an ink-jet system of applying a thermal energy the ink so as to eject or discharge the ink. In such a case, instead of the piezoelectric element  304  and the vibration plate  303  as the piezoelectric actuator, a heater configured to provide the thermal energy to the ink in the inside of the pressure chamber is arranged in the inside of the pressure chamber and is driven by the driver IC. In this case, the heater configured to provide the thermal energy to the ink in the pressure chamber corresponds to the “energy applying mechanism” of the present disclosure. 
     Further, the printer  10  as described above is used in the state that the front wall  31  and rear wall  32  of the casing  14  are along the up-down direction and the left-right direction, the usage posture of the printer  10  is not limited to this.