Patent Publication Number: US-2021178768-A1

Title: Liquid discharge apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims priority from Japanese Patent Application No. 2019-226773 filed on Dec. 16, 2019, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present disclosure relates to a liquid discharge apparatus having a waste liquid storage section for storing liquid which is discharged from a head to a maintenance unit. 
     Description of the Related Art 
     In the internal space of the conveying apparatus for conveying the sheet extending from the rolled paper, there is a rolled paper loading section for accommodating the rolled paper. The roll paper is loaded into the roll paper loading section through a supply port for the roll paper formed on a right side surface of the apparatus case. A replacement port for a waste ink tank is formed on the right side surface of the apparatus case (see Japanese Patent Laid-Open No. 2015-120578). When the opening/closing cover on a front surface of the apparatus case is pulled out, a platen unit is pulled out forward to open the conveyance path (Japanese Patent Laid-Open No. 2015-120586 corresponding to U.S. Patent Publication No. 2015/0197105). 
     In the conveying apparatus disclosed in Japanese Patent Laid-Open No. 2015-120578, the waste ink tank is replaced through the replacement port formed on the side surface of the apparatus case. For this purpose, space adjacent to the side surface (the replacement port) of the apparatus case is required for the work. Further, in the conveying device disclosed in Japanese Patent Laid-Open No. 2015-120578 and No. 2015-120586, a platen unit or the like is disposed in front of the roll paper in the apparatus case. By operating the opening/closing cover provided with the front of the device case, the platen unit can be pulled out. Therefore, the user cannot access the waste ink tank from the front surface of the apparatus case. 
     The present disclosure has been made in view of the above-mentioned circumstances, and an object thereof is to provide a liquid discharge apparatus in which a waste liquid storage section can be pulled out from a front surface of a casing of the apparatus. 
     SUMMARY 
     According to an aspect of the present disclosure, there is provided a liquid discharge apparatus, including: 
     a casing having a first surface and a second surface positioned apart from each other in a first direction, a third surface and a fourth surface positioned apart from each other in a second direction perpendicular to the first direction, and a fifth surface and a sixth surface positioned apart from each other in a third direction perpendicular to the first direction and the second direction, the first surface having a first opening and a discharge opening through which a continuous sheet is discharged; 
     a waste liquid storage section positioned in an internal space of the casing and configured to be pulled out from the casing through the first opening; 
     a sheet accommodating section positioned between the waste liquid storage section and the second surface in the first direction in the internal space of the casing and configured to accommodate the continuous sheet; 
     a conveyor configured to convey the continuous sheet that extends from the sheet accommodating section to the discharge opening; 
     a head positioned between the waste liquid storage section and the fifth surface in the third direction in the internal space of the casing and configured to discharge liquid droplets; and 
     a maintenance unit positioned between the waste liquid storage section and the fifth surface in the third direction in the internal space of the casing, configured to receive liquid discharged from the head, and connected to the waste liquid storage section so that the liquid flows to the waste liquid storage section. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an external appearance of an image recording apparatus according to an embodiment of the present disclosure. 
         FIG. 2  is a perspective view of an external appearance of the image recording apparatus with a front cover and a side cover opened. 
         FIG. 3  is a perspective view depicting side frames and a subframe attached to a base. 
         FIG. 4  is a cross-sectional view taken along a line IV-IV of  FIG. 1 , wherein a maintenance unit is in a standby position. 
         FIG. 5  is a cross-sectional view taken along a line V-V of  FIG. 4 . 
         FIG. 6  is a cross-sectional view taken along a line VI-VI of  FIG. 4 . 
         FIG. 7  depicts a schematic configuration of a circulation mechanism. 
         FIG. 8  is a cross-sectional view of a first support mechanism and the maintenance unit that have pivoted downward. 
         FIG. 9  is a cross-sectional view of the first support mechanism pivoting downward and the maintenance unit in a maintenance position. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     An image recording apparatus  100  according to an embodiment of the present disclosure is explained below. Note that the embodiment explained below is merely an example of the present disclosure, and it goes without saying that the embodiment can be appropriately changed in a range that does not alter the gist or essential characteristics of the present disclosure. In the following, movement directed from a start point to an end point of an arrow is expressed as an orientation, and reciprocating movement on a line connecting the start point and the end point of the arrow is expressed as a direction. Further, an up-down direction (a third direction)  7  is defined with reference to a state (the state of  FIG. 1 ) where the image recording apparatus  100  is usably disposed. A front-rear direction (a first direction)  8  is defined assuming a side provided with a discharge opening  33  to be a front side (a front surface). A left-right direction (a second direction)  9  is defined viewing the image recording apparatus  100  from the front side (front surface). 
     &lt;Configuration of External Appearance of Image Recording Apparatus  100 &gt; 
     The image recording apparatus  100  (an example of a liquid discharge apparatus) depicted in  FIG. 1  records an image on a sheet S (an example of a continuous sheet) formed in a roll body  37  (see  FIG. 4 ) in accordance with an ink-jet recording system. 
     As depicted in  FIG. 1 , the image recording apparatus  100  includes a casing  30 . The casing  30  includes an upper casing  31  (an upper unit or an example of a first unit) and a lower casing  32  (a lower unit or an example of a second unit). The upper casing  31  and the lower casing  32  have a substantially rectangular parallelepiped shape as a whole, and have a size that can be placed on a table. The following explanation of the casing  30  is made in a state where the upper casing  31  and the lower casing  32  have the rectangular parallelepiped shape as a whole. 
     The casing  30  has a right surface  30 R, a left surface  30 L, an upper surface  30 U, a lower surface  30 D, a front surface  30 F, and a rear surface  30 B. The right surface  30 R and the left surface  30 L are positioned apart in the left-right direction  9 . The upper surface  30 U and the lower surface  30 D are positioned apart in the up-down direction  7 . The front surface  30 F and the rear surface  30 B are positioned apart in the front-rear direction  8 . That is, the casing  30  has the front surface  30 F and the rear surface  30 B (an example of a first surface and an example of a second surface) positioned apart in the front-rear direction (the first direction)  8 , the left surface  30 L and the right surface  30 R (an example of a third surface and an example of a fourth surface) positioned apart in the left-right direction (the second direction)  9  perpendicular to the front-rear direction (the first direction)  8 , and the upper surface  30 U and the lower surface  30 D (an example of a fifth surface and an example of a sixth surface) positioned apart in the up-down direction (the third direction)  7  perpendicular to the front-rear direction (the first direction)  8  and the left-right direction (the second direction)  9 . 
     The rear surface  30 B of the upper casing  31  is connected to the lower casing  32  so that the upper casing  31  is pivotable around a pivot axis  31 A (see  FIG. 4 ) extending in the left-right direction  9 . The upper casing  31  pivotally moves from a closed position depicted in  FIG. 1  so that the front surface  30 F is lifted upward to an opened position depicted in  FIG. 2 . When the upper casing  31  is in the opened position, an internal space  30 A of the casing  30  (see  FIG. 4 ) is exposed to the outside. In  FIG. 2 , an internal structure of the casing  30  is omitted. 
     As depicted in  FIG. 1 , the front surface  30 F of the casing  30  is formed having the discharge opening  33  that is long in the left-right direction  9 . A center portion in the left-right direction  9  of the discharge opening  33  is positioned at the right of a center portion in the left-right direction  9  of the front surface  30 F. The discharge opening  33  causes the internal space  30 A of the casing  30  to communicate with the outside. The sheet S for which image recording has been performed in the internal space  30 A of the casing  30  is discharged to the outside of the casing  30  through the discharge opening  33 . 
     An operation panel  44  is provided on the front surface  30 F of the casing  30 . The operation panel  44  is positioned above the discharge opening  33 . A user inputs, to the operation panel  44 , instructions for operating the image recording apparatus  100  and confirming a variety of kinds of settings. 
     The front surface  30 F of the casing  30  is provided with a front cover (a first cover)  16 . The front cover  16  is positioned below the discharge opening  33 . The front cover  16  is pivotable around a pivot axis extending on the front surface  30 F in the left-right direction  9  with an upper end of the front cover  16  in the closed position depicted in  FIG. 1  as a pivot end. When the upper end of the front cover  16  in the closed position pivots to be pulled forward, the front cover  16  has the opened position depicted in  FIG. 2 . 
     As depicted in  FIG. 2 , when the front cover  16  is in the opened position, an opening (a first opening)  17  formed in the front surface  30 F is opened. The opening  17  allows the internal space  30 A of the casing  30  to communicate with the outside. A user is accessible to a tank  34  (see  FIG. 5 ) and a waste liquid tank  47  (see  FIG. 5 ) arranged in the internal space  30 A of the casing  30  through the opening  17  opened. The opening  17  is opened and closed by the front cover  16  as described above. 
     The front cover  16  is provided with a window  18 . The window  18  may be a through hole formed in the front cover  16 . The through hole as the window  18  may be sealed with a translucent member. A user can visually recognize the internal space  30 A from the outside of the casing  30  through the window  18  of the front cover  16  in the closed position. The window  18  of the front cover  16  in the closed position faces the tank  34 . The user can thus visually recognize the tank  34  from the outside of the casing  30  through the window  18 , even when the front cover  16  is in the closed position. The user can visually recognize a liquid level of ink stored in the tank  34  by forming at least part of the tank  34  by a translucent member. 
     As depicted in  FIGS. 1 and 2 , a side cover (a second cover)  19  is positioned in the right surface  30 R of the lower casing  32 . The side cover  19  is slidable with respect to the lower casing  32  along the front-rear direction  8 . An opening (a second opening)  15  is formed in the right surface  30 R. The opening  15  is opened and closed by sliding the side cover  19 . The opening  15  causes a sheet accommodating space  30 C to communicate with the outside. That is, the opening/closing of the side cover  19  causes the sheet accommodating space  30 C (see  FIG. 4 ) to be opened and closed with respect to the outside. Opening the side cover  19  exposes a holder  35  to the outside, which allows the roll body  37  to be installed to the holder  35 . 
     As depicted in  FIG. 3 , the internal space  30 A of the casing  30  is provided with two side frames  20  and  21  (an example of a first side frame and an example of a second side frame) and a subframe  22 . Each of the side frames  20  and  21  has a flat plate shape made from a steel plate. A cutout (notch) and/or a through hole is/are appropriately formed in each of the side frames  20  and  21 . The cutout and/or the through hole have a shape(s) depending on a member supported by each of the side frames  20  and  21 . Each of the side frames  20  and  21  may be bent to increase strength. The two side frames  20  and  21  are positioned apart in the left-right direction  9 . Although not depicted in  FIG. 3 , the side frames  20  and  21  form an integral frame structure by using any other frame coupling the side frames  20  and  21 . The side frames  20  and  21  are coupled to a base  23  that forms the lower surface  30 D of the casing  30 . The frames, including the side frames  20  and  21 , are coupled with each other by screws, welding, or the like. 
     Of the two side frames  20  and  21 , a front lower corner of the side frame  20  positioned at the left in the left-right direction  9  is formed having a cutout (notch)  20 A. A front end of the side frame  20  is thus not coupled to the base  23 , and the front end of the side frame  20  has a space corresponding to the cutout  20 A. The space corresponding to the cutout  20 A is provided with the subframe  22 . A rear lower corner of the side frame  21  is formed having a cutout (notch)  21 A. The cutout  21 A is an opening through which the roll body  37  is installed in the sheet accommodating space  30 C (see  FIG. 4 ). A user is accessible to the sheet accommodating space  30 C from the outside through the cutout  21 A and the opening (the second opening)  15  formed in the right surface  30 R of the casing  30 . 
     The subframe  22  has an upper wall  22 U and a left wall  22 L. The left wall  22 L and the side frame  21  are positioned apart in the left-right direction  9 . The upper wall  22 U couples an upper end of the left wall  22 L to the side frame  21 . A lower end of the left wall  22 L is coupled to the base  23 . The upper wall  22 U is coupled to the cutout  20 A of the side frame  20 . The subframe  22  is thus positioned below the front portion of the side frame  20  so that the subframe  22  and the two side frames  20 ,  21  form the integral frame. The tank  34  and the waste liquid tank  47  are positioned in a space surrounded by the subframe  22  (see  FIG. 5 ). 
     &lt;Internal Configuration of Image Recording Apparatus  100 &gt; 
     As depicted in  FIG. 4  and  FIG. 5 , the holder  35 , a tensioner  45 , a conveyance roller pair  36 , a discharge roller pair  40 , a head  38 , the first support mechanism  51 , a fixing unit  39 , a support member  46 , a second support mechanism  52 , a contact image sensor (CIS)  95 , a cutter unit  26 , the tank  34 , the waste liquid tank  47 , a maintenance unit  60 , and a wiper cleaning unit  80  are arranged in the internal space  30 A. 
     In the internal space  30 A, a partition wall  41  is provided between the side frames  20  and  21  in the left-right direction  9 . The partition wall  41  partitions a rear lower portion of the internal space  30 A to define the sheet accommodating space  30 C (an example of a sheet accommodating section). The sheet accommodating space  30 C is a space surrounded by the partition wall  41  and the lower casing  32  and separated or isolated from the head  38  and the like. 
     The roll body  37  is accommodated in the sheet accommodating space  30 C. The roll body  37  has a core tube and the long sheet S. The sheet S is wound around the core tube in a roll shape in a circumferential direction of an axial core of the core tube. The sheet S may have a width ranging from a minimum width to a maximum width in which the image recording apparatus  100  is capable of recording an image. That is, a plurality of types of the roll body  37  having different widths are accommodatable in the sheet accommodating space  30 C. The roll body  37  may not have the core tube, and the sheet S may be formed in a roll shape so that the sheet S is installable in the holder  35 . 
     The holder  35  extending in the left-right direction  9  is positioned in the sheet accommodating space  30 C. The roll body  37  can be installed in the holder  35 . When the roll body  37  is installed in the holder  35 , the holder  35  supports the roll body  37  so that the axial core of the core tube of the roll body  37  is along the left-right direction  9  and the roll body  37  is rotatable in the circumferential direction of the axial core. 
     As depicted in  FIG. 4  and  FIG. 6 , the holder  35  is provided with a pair of side guides  25  separated from each other in the left-right direction  9 . A distance between the side guides  25  in the left-right direction  9  is changeable. A user moves the pair of side guides  25  so that the side guides  25  come into contact with or abut against left and right ends of the roll body  37  according to the width of the roll body  37  to be installed to the holder  35  (the size along the left-right direction  9 ). The roll body  37 , of which left and right ends are brought into contact with the side guides  25 , is positioned so that a center portion in the width direction of the sheet S is coincident with a center portion in the left-right direction  9  of a conveyance route  43  through which the sheet S is conveyed. 
     The holder  35  rotates around an axis along the left-right direction  9  when a first driving transmission mechanism  57  transmits driving force of a first motor  55  described below to the holder  35 . Along with the rotation of the holder  35 , the roll body  37  supported by the holder  35  also rotates. 
     A rear portion of the sheet accommodating space  30 C is opened upward. Specifically, a gap  42  is formed between the partition wall  41  and the rear surface  30 B, that is, formed above a rear end of the roll body  37 . Rotating the conveyance roller pair  36  and the discharge roller pair  40  pulls out the sheet S upward from the rear end of the roll body  37 , and the sheet S pulled out is guided to the tensioner  45  via the gap  42 . 
     In the internal space  30 A, the tensioner  45  is positioned between the side frames  20  and  21  in the left-right direction  9 . At a rear portion of the internal space  30 A, the tensioner  45  is positioned above the partition wall  41 . The tensioner  45  is a roller that is supported by the side frames  20  and  21  so that the tensioner  45  is rotatable and movable in the front-rear direction  8 . Rearward urging force is applied to the tensioner  45  by an urging member such as a spring. 
     In the internal space  30 A, the conveyance roller pair  36  (an example of a conveyor) is positioned between the side frames  20  and  21  in the left-right direction  9 . The conveyance roller pair  36  is positioned at the front side of the tensioner  45 . The conveyance roller pair  36  has a conveyance roller  36 A and a pinch roller  36 B. The conveyance roller  36 A is rotatably supported by the side frames  20  and  21 . The conveyance roller  36 A rotates around an axis direction that is along the left-right direction  9 . The conveyance roller  36 A rotates when receiving driving force from a second motor  56  described below through a second driving transmission mechanism  58 , thus conveying the sheet S frontward (conveyance orientation  8 A) while nipping the sheet S between the conveyance roller  36 A and the pinch roller  36 B. 
     In the internal space  30 A, the discharge roller pair  40  (an example of the conveyor) is positioned between the side frames  20  and  21  in the left-right direction  9 . The discharge roller pair  40  is positioned at the front side of the conveyance roller pair  36 . The discharge roller pair  40  has a discharge roller  40 A and a pinch roller  40 B. The discharge roller  40 A is rotatably supported by the side frames  20  and  21 . The discharge roller  40 A rotates around an axis direction that is along the left-right direction  9 . The discharge roller  40 A rotates when receiving driving force from the second motor  56  described below through the second driving transmission mechanism  58 , thus conveying the sheet S frontward (conveyance orientation  8 A) while nipping the sheet S between the discharge roller  40 A and the pinch roller  40 B. 
     In the internal space  30 A, the head  38  is positioned between the side frames  20  and  21  in the left-right direction  9 . The head  38  is positioned downstream of the conveyance roller pair  36  in the conveyance orientation  8 A. The head  38  has nozzles  38 A. Ink is discharged downward, as liquid droplets, from the nozzles  38 A toward the sheet S supported by a conveyance belt  101 . Accordingly, an image is recorded on the sheet S. In this embodiment, ink contains a resin that is cured by ultraviolet light. 
     As depicted in  FIG. 4 , the head  38  is pivotable about a pivot axis  38 B positioned at a rear end of the head  38  and extending in the left-right direction  9 . The head  38  indicated by a solid line in  FIG. 4  is in a first position where liquid droplets are discharged toward the first support mechanism  51 . The head  38  indicated by a broken line in  FIG. 4  is in a second position where an upper portion of the first support mechanism  51  is opened. That is, the head  38  in the second position opens part of the conveyance route  43 . 
     In the internal space  30 A, the first support mechanism  51  is positioned between the side frames  20  and  21  in the left-right direction  9 . The first support mechanism  51  is positioned downstream of the conveyance roller pair  36  in the conveyance orientation  8 A. The first support mechanism  51 , which is positioned below the head  38 , faces the head  38 . The first support mechanism  51  has the conveyance belt  101  and a support portion  104 . The support portion  104  is capable of supporting the maintenance unit  60  in a maintenance position (see  FIG. 9 ). The support portion  104  includes a frame  104 A having a surface extending in the up-down direction  7  and the front-rear direction  8 . Part of the second driving transmission mechanism  58  is rotatably attached to the frame  104 A to support the second driving transmission mechanism  58 . The first support mechanism  51  and the conveyance belt  101  are an exemplary conveyance belt unit. 
     The conveyance belt  101  is formed as follows. That is, an endless belt is stretched between two pullies that are separated from each other in the front-rear direction  8  and rotate around an axis extending along the left-right direction  9 . An axis direction of the conveyance belt  101  is parallel to an axis direction of the holder  35 . When one of the two pullies of the conveyance belt  101  receives driving force of the second motor  56  through the second driving transmission mechanism  58 , rotary motion of the endless belt is caused to convey the sheet S in the conveyance orientation  8 A. The sheet S is supported by the endless belt during the conveyance. The two pullies are rotatably attached to the frame  104 A of the support portion  104 . That is, the support portion  104  supports the two pullies. 
     In the internal space  30 A, the fixing unit  39  is positioned between the side frames  20  and  21  in the left-right direction  9 . The fixing unit  39  is positioned downstream of the head  38  in the conveyance orientation  8 A and upstream of the discharge roller pair  40  in the conveyance orientation  8 A. The fixing unit  39  is an ultraviolet irradiator having a substantially rectangular parallelepiped shape that is long in the left-right direction  9 . The fixing unit  39  irradiates the sheet S passing directly below the fixing unit  39  and ink on the sheet S with ultraviolet light. The resin in the ink irradiated with ultraviolet light is cured, and a pigment in the ink is fixed to the sheet S. 
     The fixing unit  39  is not limited to the ultraviolet irradiator. For example, when ink contains thermoplastic resin fine particles, the fixing unit  39  may be a heater. In this case, the thermoplastic resin fine particles are melted by heating the sheet S and ink on the sheet S with the fixing unit  39 , and the melted resin is cured by cooling performed thereafter. Accordingly, the pigment in ink is fixed to the sheet S. 
     In the internal space  30 A, the support member  46  is positioned between the side frames  20  and  21  in the left-right direction  9 . The support member  46  is positioned downstream of the head  38  and the first support mechanism  51  in the conveyance orientation  8 A. A rear portion of the support member  46  faces the fixing unit  39 . A front portion of the support member  46  faces the discharge roller  40 A. The support member  46  supports the sheet S conveyed in the conveyance orientation  8 A by the conveyance belt  101  of the first support mechanism  51 . 
     The second support mechanism  52  is positioned below the support member  46 . The second support mechanism  52  can support the maintenance unit  60  in a standby position. 
     The CIS  95  is positioned downstream of the discharge roller pair  40  in the conveyance orientation  8 A. In the CIS  95 , light that is emitted from a light source such as an LED is reflected by a sheet. The reflection light is collected to a line sensor by a refractive index distribution type lens. The line sensor outputs an electric signal depending on intense of the reflection light received. The CIS  95  can read an image on a printing surface (upper surface) of the sheet S. The CIS  95  is disposed so that a reading line extends in the left-right direction  9 . 
     The cutter unit  26  is positioned downstream of the CIS  95  in the conveyance orientation  8 A. The cutter unit  26  is configured so that a cutter  28  is carried on a cutter carriage  27 . The cutter carriage  27  moves in the left-right direction  9  by a belt driving mechanism (not depicted). The cutter  28  moves in the left-right direction  9  along with movement of the cutter carriage  27 . The sheet S positioned between the discharge roller pair  40  and the discharge opening  33  is cut along the left-right direction  9  through movement of the cutter  28 . 
     As depicted in  FIG. 5 , the tank  34  is a container having a rectangular parallelepiped shape. The tank  34  stores ink in its internal space. The tank  34  is positioned in a space surrounded by the subframe  22  at the front lower side of the internal space  30 A. The tank  34  is surrounded by the subframe  22 , the side frame  21 , and the base  23 . The internal space of the tank  34  is connected to the head  38  via a tube (not depicted) so that ink is supplied to the head  38 . In this embodiment, the tank  34  is a cartridge-type that is removable with respect to the casing  30 . 
     As depicted in  FIG. 4  and  FIG. 5 , the waste liquid tank  47  (an example of a waste liquid storage section) is a container having a rectangular parallelepiped shape. The waste liquid tank  47  holds ink in its internal space. The waste liquid tank  47  is positioned between the subframe  22  and the side frame  21  at the lower front side of the internal space  30 A. The waste liquid tank  47  is surrounded by the subframe  22 , the side frame  21 , and the base  23 . The interior space of the waste liquid tank  47  is connected to the maintenance unit  60  via a tube (not depicted) so that ink discharged from the maintenance unit  60  flows therethrough. In this embodiment, the waste liquid tank  47  is a cartridge-type that is replaceable with respect to the casing  30 . 
     As depicted in  FIG. 6 , a circulation mechanism  81  (an example of a supply unit) is positioned in the internal space  30 A at the left of the side frame  20  in the left-right direction  9 . The circulation mechanism  81  is supported by the side frame  20 . As depicted in  FIG. 7 , the circulation mechanism  81  includes a subtank  83 , the first pump  85  (an example of a pump), and the second pump  87 . The subtank  83  and pumps  85  and  87  are connected to the tank  34  and the nozzles  38 A of the head  38  via channels  110  and  120 . Each of the channels  110  and  120  is provided with a valve as appropriate. In this embodiment, the valve is omitted. Each of the channels  110  and  120  may be configured by a tube or the like. 
     Specifically, the tank  34  is connected to the subtank  83  by the channel  110 , and ink can be supplied from the tank  34  to the subtank  83 . The subtank  83  is in atmospheric communication with the outside via the second pump  87 . When the second pump  87  is driven, pressure inside the subtank  83  becomes negative, and ink is supplied from the tank  34  to the subtank  83 . When ink is supplied from the tank  34  to the subtank  83 , the channel(s)  120  between the subtank  83  and the head  38  is/are closed. When the first pump  85  is driven, ink circulates through the channel(s)  120  between the subtank  83  and the nozzles  38 A of the head  38 . 
     The maintenance unit  60  performs maintenance of the head  38 . The maintenance unit  60  is movable between the side frames  20  and  21  in the up-down direction  7  and the front-rear direction  8 . The maintenance unit  60  is positioned directly below the head  38  when maintenance of the head  38  is performed (see  FIG. 9 , the maintenance position). 
     The maintenance of the head  38  includes a flushing process, a purge process, a wiping process, and the like. In the flushing process, ink is discharged toward the maintenance unit  60 . In the purge process, ink is sucked from the nozzles  38 A by a suction pump  74  in a state where the nozzles  38 A are covered with a cap  62  of the maintenance unit  60 . In the wiping process, a nozzle surface of the head  38  is wiped with a wiper  63  of the maintenance unit  60 . Ink discharged to the cap  62  through the flushing process and the purge process is discharged to the waste liquid tank  47  through a channel  125 . 
     The wiper cleaning unit  80  cleans the wiper  63  of the maintenance unit  60 . The wiper cleaning unit  80  faces downward by being supported by the support member  46 . The maintenance unit  60  moves to a position directly below the wiper cleaning unit  80  when cleaning of the wiper  63  is performed. 
     The maintenance unit  60  is movable in an inclination direction  6  by sliding with respect to the second support mechanism  52  in a state of being supported by the second support mechanism  52 . The maintenance unit  60  supported by the second support mechanism  52  moves along the inclination direction  6 , which allows the wiper  63  to move while being brought into contact with the wiper cleaning unit  80 . This wipes ink adhering to the wiper  63  off. 
     As depicted in  FIG. 4 , the maintenance unit  60  in the standby position is supported by the second support mechanisms  52 . When a motor (not depicted) is driven, as depicted in  FIG. 8 , a front portion of the first support mechanism  51  and the conveyance belt  101  pivot to move downward. This allows the maintenance unit  60  to move from the second support mechanism  52  to the first support mechanism  51 . When the second driving transmission mechanism  58  transmits driving force of the second motor  56  to the second driving transmission mechanism  58 , the maintenance unit  60  in the standby position moves in an orientation  4  in the inclination direction  6  while being guided by the second support mechanism  52  and the first support mechanism  51  and then the maintenance unit  60  is supported by the first support mechanism  51 . 
     Driving force is transmitted from the motor (not depicted) in a state where the maintenance unit  60  is supported only by the first support mechanism  51 . This causes the front portion of the first support mechanism  51  to pivot and move upward. Thus, the maintenance unit  60  is positioned in the maintenance position, as depicted in  FIG. 9 . The standby position is at the front side of the maintenance position and above the tank  34 . 
     As depicted in  FIG. 9 , the head  38  moves downward with respect to the maintenance unit  60  in the maintenance position, thus covering the nozzles  38 A with the cap  62  of the maintenance unit  60 . The purge process can be executed in this state. The wiping process is executed by moving the maintenance unit  60  positioned in the maintenance position along the first support mechanism  51  in the front-rear direction  8 . 
     When the maintenance unit  60  moves from the maintenance position to the standby position, an operation reverse to the above is executed. 
     &lt;Arrangement in Internal Space  30 A of Casing  30 &gt; 
     As depicted in  FIG. 4 , the sheet accommodating space  30 C is positioned in the internal space  30 A of the casing  30  at the rear side of the waste liquid tank  47  in the front-rear direction  8 . The head  38  and the maintenance unit  60  are positioned above the waste liquid tank  47  in the up-down direction  7 . Thus, in this embodiment, the sheet accommodating space  30 C, the head  38 , and the maintenance unit  60  are not arranged between the maintenance unit  60  and a wall (front wall) including the front surface  30 F of the casing  30 . That is, the maintenance unit  60  is adjacent to the wall (front wall) including the front surface  30 F of the casing  30 . In the state where the front cover  16  is in the closed position ( FIG. 1 ), the maintenance unit  60  faces the front cover  16 . In the state where the front cover  16  is in the opened position ( FIG. 2 ), the maintenance unit  60  is opened (exposed) to the outside through the opening (first opening)  17 . 
     As depicted in  FIGS. 5 and 6 , a right portion of the tank  34 , the head  38 , the maintenance unit  60 , and the waste liquid tank  47  are positioned, in the left-right direction  9 , in a range (a width in the left-right direction  9  of the conveyance route  43 ) P of the conveyance route  43  through which the sheet S passes. 
     The circulation mechanism  81  is positioned above the tank  34  in the up-down direction  7 . As depicted in  FIG. 6 , the head  38  is positioned at the right of the circulation mechanism  81  in the left-right direction  9 . As depicted in  FIGS. 5 and 6 , the maintenance unit  60  is positioned at the right of the circulation mechanism  81  in the left-right direction  9  below the head  38  in the up-down direction  7 . The waste liquid tank  47  is positioned at the right of the tank  34  in the left-right direction  9 . 
     As depicted in  FIG. 7 , a channel through which ink flows from the tank  34  to the circulation mechanism  81  is formed by a tube or the like. Similarly, a channel through which ink flows from the circulation mechanism  81  to the head  38  is formed by a tube or the like. The head  38  discharges ink to the maintenance unit  60  in the maintenance position. A channel through which ink flows from the maintenance unit  60  to the waste liquid tank  47  is formed by a tube or the like. 
     &lt;Working Effect of Embodiment&gt; 
     As depicted in  FIG. 4 , in the liquid discharge apparatus of this embodiment, the sheet accommodating space  30 C is positioned at the rear side of the waste liquid tank  47  in the front-rear direction  8  in the internal space  30 A of the casing  30 . That is, the sheet accommodating space  30 C is positioned between the waste liquid tank  47  and the rear surface  30 B in the front-rear direction  8 . The head  38  and the maintenance unit  60  are positioned above the waste liquid tank  47  in the up-down direction  7 . That is, the head  38  and the maintenance unit  60  are positioned between the waste liquid tank  47  and the upper surface  30 U in the up-down direction  7 . 
     According to the above configuration, the waste liquid tank  47  can be pulled out through the opening  17  of the front surface  30 F of the casing  30 , and thus operability is good. 
     The liquid discharge apparatus  100  of this embodiment further includes a side cover  15  with which the opening  15  of the right surface  30 R of the casing  30  is opened and closed. The side cover  15  is slidable with respect to the casing  30  along the front-rear direction  8 . The roll body  37  (sheet S) is installable in the sheet accommodating space  30 C through the opening of the right surface  30 R of the casing  30 . 
     According to the above configuration, the waste liquid tank  47  is pulled out frontward. Thus, the side cover  19  can slide in the front-rear direction  8  without interfering with a space at the front side of the casing  30  for pulling out the waste liquid tank  47 . 
     In the liquid discharge apparatus  100  of this embodiment, the waste liquid tank  47 , the sheet accommodating space  30 C, the conveyance roller pair  36 , the discharge roller pair  40 , the head  38 , and the maintenance unit  60  are positioned between the two side frames  20  and  21  in the left-right direction  9 . 
     According to the above configuration, the cutouts for pulling out the waste liquid tank  47  are not required in the side frames  20  and  21 , and thus strength of the side frames  20  and  21  is improved. 
     In the liquid discharge apparatus  100  of this embodiment, the internal space  30 A of the casing  30  is opened to the outside by moving the upper casing  31  with respect to the lower casing  32 . 
     According to the above configuration, the internal space  30 A of the casing  30  is opened to the outside by pivoting the upper casing  31  with respect to the lower casing  32 . A user is thus accessible to the internal space  30 A from above the casing  30 , for example, in order to get rid of paper jam. 
     In the liquid discharge apparatus  100  of this embodiment, the head  38  is pivotable between the first position where liquid droplets are discharged to the sheet S and the second position where the conveyance route  43  through which the sheet S passes is opened. 
     According to the above configuration, the conveyance route  43  through which the sheet S passes is opened to the outside in the state where the head  38  is in the second position. This allows a user to easily solve a trouble, such as paper jam. 
     In the liquid discharge apparatus  100  of this embodiment, the circulation mechanism  81  is positioned above the tank  34  in the up-down direction  7 . The head  38  is positioned at one side in the left-right direction  9  of the circulation mechanism  81 . The maintenance unit  60  is positioned at the one side in the left-right direction  9  of the circulation mechanism  81  and at the lower side in the up-down direction  7  of the head  38 . The waste liquid tank  47  is positioned at the one side in the left-right direction  9  of the tank  34 . That is, in the liquid discharge apparatus  100  of this embodiment, the tank  34  and the circulation mechanism  81  are arranged in this order from the bottom in the up-down direction  7 . The head  38 , the maintenance unit  60 , and the waste liquid tank  47  are arranged in this order from the top in the up-down direction  7 . The head  38 , the maintenance unit  60 , and the waste liquid tank  47  are positioned at the same side in the left-right direction  9  of the tank  34  and the circulation mechanism  81 . That is, all of the head  38 , the maintenance unit  60 , and the waste liquid tank  47  are positioned at the right or left of the tank  34  and the circulation mechanism  81 . 
     According to the above configuration, the channels of the tank  34 , the circulation mechanism  81 , the head  38 , the maintenance unit  60 , and the waste liquid tank  47 , through which ink flows in this order, can be arranged not to intersect with each other when seen from the front-rear direction  8 . 
     MODIFICATIONS 
     In the above embodiment, the tank  34  and the waste liquid tank  47  are replaceable independently. However, the tank  34  may be formed integrally with the waste liquid tank  47  so that the tank  34  and the waste liquid tank  47  is replaceable as one cartridge at the same time. 
     In the above embodiment, the waste liquid tank  47  is a cartridge-type that can be replaceable with respect to the casing  30 . The waste liquid tank  47  is not limited to one of which entirety is replaced. For example, a component forming the waste liquid tank  47 , such as a liquid absorber, may be replaceable by pulling out part of the waste liquid tank  47  through the opening  17  of the front surface  30 F of the casing  30 . 
     The upper casing  31  is not limited to the configuration that pivots with respect to the lower casing  32 . The internal space  30 A of the casing  30  may be exposed to the outside by allowing the upper casing  31  to slide with respect to the lower casing  32  or removing the upper casing  31  from the lower casing  32 .