Patent Publication Number: US-2021170767-A1

Title: Printing device

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application is a continuation of International Application No. PCT/JP2019/032660 filed on Aug. 21, 2019 which claims priority from Japanese Patent Application No. 2018-157812 filed on Aug. 24, 2018. The entire contents of the referenced applications are incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a printing apparatus which applies, to a sheet having an ink ejected from a printing head adhered thereon, an energy for fixing the ink to the sheet so as to fix the ink to the sheet, and which discharges the sheet from a discharge port of a casing. 
     BACKGROUND ART 
     There is known a printing apparatus provided with a fixing device capable of applying, to a sheet having an ink ejected from a nozzle of a printing head adhered thereon, an energy for fixing the ink to the sheet. As an example of the fixing device, there is known a heater which heats a sheet having an ink adhered thereon, and there is known a printing apparatus which executes printing by heating, with the heater, a sheet having an ink ejected from a printing head adhered thereon. There is a long sheet which is continuous in a conveyance direction as an example of a print medium. The long sheet after the printing performed thereon is discharged from a discharge port of a casing to the outside of the casing. 
     SUMMARY 
     Regarding the printing apparatus having the fixing device such as a heater, etc., installed in the inside of the casing, a part or component arranged in the vicinity of the discharge port of the casing receives the heat generated in the fixing device such as the heater, etc., and thus is adversely affected in a variety of manner, in some cases. In particular, in a case that the casing is miniaturized to be placeable on a tabletop (desktop), the internal space of the casing becomes small, which in turn causes the heat radiation of the fixing device such as the heater, etc., easily affects the above-described part or component. 
     The present disclosure has been made in view of the above-described situation, and an object of the present disclosure is to provide a means for causing any adverse effect of the heat radiated by the fixing device, such as the heater, etc., positioned in the internal space of the casing of the printing apparatus, to be less likely to occur. 
     According to an aspect of the present disclosure, there is provided a printing apparatus including a casing; a conveyance route formed in an internal space of the casing, wherein a sheet passes through the conveyance route in a conveyance direction toward a discharge port opened in an outer wall of the casing; a printing head positioned in the casing, and configured to eject an ink to the sheet passing through the conveyance route; and a fixing device positioned in the casing, at a location, of the conveyance route, at a downstream in the conveyance direction of the printing head, and configured to apply, to the sheet having the ink adhered thereon, an energy for fixing the ink so as to fix the ink to the sheet. A shortest distance A between the fixing device and the discharge port is longer than a shortest distance B between the printing head and the fixing device. 
     According to the above-described configuration, it is possible to reduce the size along the conveyance direction of the casing, while arranging the printing head and the heater such that any effect of the heat radiation from the heater is not generated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a printing apparatus  10 , on a side of a front surface  14 A. 
         FIG. 2  is a schematic view depicting the internal structure of the printing apparatus  10 . 
         FIG. 3  is a schematic view depicting the internal structure of the printing apparatus  10 , as seen from thereabove. 
         FIG. 4  is a schematic view depicting the internal structure of a printing head  24 . 
         FIG. 5  is a view corresponding to  FIG. 2 , and depicting a case that a heater  26  is arranged to be shifted upward in an up-down direction. 
         FIG. 6  is a schematic view depicting the internal structure of a printing apparatus  10  according to a modification having a cooling mechanism  48 . 
         FIG. 7  is a schematic view depicting the internal structure of a printing apparatus  10  according to a modification. 
         FIG. 8  is a schematic view depicting the internal structure of a printing apparatus  310 . 
         FIG. 9  is a schematic view depicting the internal structure of the printing apparatus  310 , as seen from thereabove. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     A printing apparatus  10  according to an embodiment of the present disclosure will be explained below. Note that an 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 within a range not changing the gist of the present disclosure. Further, in the following explanation, an up-down direction  7  is defined, with a state in which the printing apparatus  10  is usably or operably installed (the state of  FIG. 1 ) as the reference; a front-rear direction  8  is defined, with a side on which a discharge port  13  is provided is defined as a front side (front surface); and a left-right direction  9  is defined, with the printing apparatus  10  as seen from the front side (front surface). 
     &lt;Overall Configuration of Printing Apparatus  10 &gt; 
     As depicted in  FIG. 1 , the printing apparatus  10  records an image on roll paper  11  (see  FIG. 2 : an example of a “sheet”), etc., in the ink-jet recording system. A casing  14  has a substantially rectangular parallelepiped shape in which the discharge port  13  is formed in a front surface  14 A (an example of a “surface of an outer wall”) of the casing  14 . The discharge port  13  is positioned in the front surface  14 A on the right side in the left-right direction  9 . The casing  14  has a size placeable on the tabletop (desktop). Namely, the printing apparatus  10  is suitable for being used while being placed on the tabletop. Of course, the printing apparatus  10  may be used while being placed on a floor surface. 
     An operation panel  17  is positioned, in the front surface  14 A of the casing  14 , on the left side in the left-right direction  9  with respect to the discharge port  13 . The operation panel  17  has, for example, a display, an input key, etc. A user performs, in the operation panel  17 , an input for operating the printing apparatus  10  and/or an input for confirming a variety of settings. 
     As depicted in  FIGS. 2 and 3 , a circuit board  17 A in which an electronic part, etc., for controlling the display and the input key of the operation panel  17  is positioned at a location on the rear side of the operation panel  17  in the front-rear direction  8 . The circuit board  17 A is positioned at a location, on the left side in the left-right direction  7 , inside the casing  17 . The circuit board  17 A has a main surface orthogonal to the front-rear direction  8 . An input-output interface circuit with respect to the display and the input key is installed in the main surface of the circuit board  17 A. The circuit board  17 A is arranged at a position which is between an opening of the discharge port  13  and a CIS  27  in the front-rear direction  8 . 
     A cover  16  is provided at a location below the operation panel  17 . The cover  16  is opened to thereby expose an internal space of the casing  14 . A tank  70  (to be described later on) is positioned at the rear side of the cover  16 . The cover  16  in a closed state is a part of the front surface  14 A of the casing  14 . 
     &lt;Internal Structure of Printing Apparatus  10 &gt; 
     As depicted in  FIG. 2 , a sheet storing space  15  capable of storing the roll sheet  11  therein is formed in the internal space of the casing  14 , at the rear side in the front-rear direction  8 . The sheet storing space  15  is a space defined in the internal space of the casing  14  by a partition wall  18 . In the sheet storing space  15 , the roll paper  11  is stored, with the left-right direction  9  as a roll axis direction (roll shaft direction). The sheet storing space  15  is opened to orient upward, at the rear side in the front-rear direction  9 . Namely, a gap, through which a sheet pulled or drawn from the roll sheet  11  is passable, is defined between the partition wall  18  and a rear wall  14 B of the casing  14 . 
     Feeding rollers  20  and  21  are positioned in the sheet storing space  15  and at a location immediately above the sheet storing space  15 , respectively. The sheet drawn rearward from the roll paper  11  is wound on the feeding roller  20  and extends upward, and further is wound on the feeding roller  21  and extends frontward. An uppermost position in the circumferential surface of the feeding roller  21  is similar, in the up-down direction  7 , to the discharge port  13 . 
     A conveyance route  22  is formed to span between the feeding roller  21  and the discharge port  13 . The conveyance route  22  extends substantially linearly. Although not depicted in detail in the respective drawings, the conveyance route  22  is a space which is defined by guide members positioned away from each other in the up-down direction  7 , a printing head  24 , a platen  25 , a heater  26 , etc., and through which the sheet is passable. In the conveyance route  22 , the front side is the downstream side in the conveyance direction. 
     As depicted in  FIGS. 2 and 3 , a conveyance roller pair  54  is provided on the conveyance route  22  at the upstream in the conveyance direction of the printing head  24 . The conveyance roller pair  54  has a conveyance roller  60  and a pinch roller  61 . A conveyance roller pair  55  is provided on the conveyance route  22  at the downstream in the conveyance direction of the heater  26 . The conveyance roller pair  55  has a conveyance roller  62  and a pinch roller  63 . The conveyance roller  60  and the conveyance roller  62  are rotated by rotation of a motor (not depicted in the drawings) transmitted thereto. The conveyance roller  60  and the conveyance roller  62  rotate in a state that a sheet extending from the roll paper  11  is pinched or held between the respective rollers constructing the conveyance roller pairs  54  and  55 , and the conveyance roller pair  54  and the conveyance roller pair  55  thereby convey the sheet. 
     In the front-rear direction  8 , the printing head  24 , the platen  25  and the heater  26  are positioned between the conveyance roller pair  54  and the conveyance roller pair  55 . Further, any other conveyance roller is not positioned in a part, of the conveyance route  22 , between the conveyance roller pair  54  and the conveyance roller pair  55 . 
     As depicted in  FIGS. 2 and 3 , the printing head  24  is located above the conveyance route  22  and faces the platen  25 , at the downstream of the conveyance roller pair  54 . The printing head  24  is positioned above the sheet storing space  15 . The printing head  24  has a part overlapping with the sheet storing space  15  in the up-down direction  7 . 
     The printing head  24  of the present embodiment includes an ejecting module  242  provided with a plurality of nozzles  30 , and a carriage  241  to which the ejecting module  240  is attached. The carriage  241  is attached to a rail (not depicted in the drawings) extending along the left-right direction  9  so that the carriage  241  is slidably movable thereon. As depicted in  FIG. 4 , the plurality of nozzles  30  are formed while being aligned in the left-right direction  9  in a lower surface of the printing head  24 , namely a lower surface of the printing head  24 . The printing apparatus  10  of the present embodiment is an ink-jet printer of the line system which ejects an ink to a sheet which is being conveyed, in a state that the printing head  24  stands still at a printing position which is a position at which the printing head  24  faces the sheet passing on the platen  25  during a printing operation. The plurality of nozzles  30  of the ejecting module  242  are aligned over the entire length of the sheet which is being conveyed. In a case that the printing apparatus  10  is in a standby state, or that the printing apparatus  10  is switched OFF, the printing head  24  stands by at a standby position located on the left side with respect to the conveyance route  22 . 
     As depicted in  FIGS. 2 and 3 , the tank  70  is positioned in the internal space of the casing  14 , at a location on the rear side of the cover  16 . The tank  70  stores the ink. As depicted in  FIG. 4 , the ink is supplied to the printing head  24  from the tank  70  via a tube  71 . The tank  70  is of a cartridge type which is attachable/detachable with respect to the casing  14 ; in a case that the cover  16  is opened, the tank  70  is removable toward the front side from the casing  14 . 
     The ink is a liquid including a pigment, minute particles of a resin, etc., and is a so-called latex ink. The ink has a viscosity which is suitable for dispersing the pigment and/or the minute particles of the resin uniformly in the ink. The pigment serves as a color of the ink. The minute particles of the resin is for fixing the pigment to the sheet, and are, for example, minute particles of a synthetic resin which exceed the glass-transition temperature by being heated by the heater  26 . The latex ink includes another publicly known component(s), as the composition thereof. 
     As depicted in  FIG. 4 , the printing head  24  is connected to a sub tank  31  by two channels  32 A and  32 B. Each of the channels  32 A and  32 B is formed, for example, of a tube made of a synthetic resin. The channel  32 A via which the ink is supplied from the sub tank  31  to the printing head  24  is provided with a pump  34 . The pump  34  is driven to circulate the ink between the printing head  24  and the sub tank  31  while the printing head  24  is ejecting the ink. The sub tank  31  is connected to the tank  70  by the tube  71 . A pump  72  is provided on the tube  71 . In a case that a remaining amount of the ink inside the sub tank  31  becomes small, the pump  72  is driven to thereby supply the ink from the tank  70  to the sub tank  31 . The sub tank  31  is arranged on the left side with respect to the conveyance route  22 . 
     As depicted in  FIG. 4 , the ejecting module  242  has the plurality of nozzles  30 , a supplying manifold  33 , a plurality of supplying channels  331 , a plurality of piezoelectric elements  35 , a discharging manifold  36 , a plurality of discharging channels  361 , a plurality of pressure chambers  37  and a plurality of descenders  38 . The plurality of nozzles  30 , the plurality of descenders  38 , the plurality of pressure chambers  37 , the plurality of supplying channels  331  and the plurality of discharging channels  361  are a plurality of individual channels provided corresponding to the plurality of nozzles  30 , respectively. 
     Note that  FIG. 4  depicts a cross section, of the ejecting module  241 , which is orthogonal to the left-right direction  9 . On the other hand, the plurality of individual channels are arranged side by side in the left-right direction  9 . Accordingly,  FIG. 4  depicts a nozzle  30 , a descender  38 , a pressure chamber  37 , a supplying channel  331  and a discharging channel  361  constructing a certain individual channel among the plurality of individual channels. Further, the plurality of piezoelectric elements  35  are arranged side by side in the left-right direction  9  in a number which is same as the number of the plurality of nozzles  30 . The supplying manifold  36  is a common channel which is provided commonly to the plurality of individual channels. 
     The supplying manifold  33  is a space communicating with the channel  32 A. The supplying manifold  33  is communicated with the plurality of pressure chambers  37  via the plurality of supplying channels  331 , respectively. The supplying manifold  33  supplies the ink to each of the plurality of nozzles  30  via one of the plurality of pressure chambers  37 . The discharging manifold  36  is a space communicating with the channel  32 B. The discharging manifold  36  is communicated with the plurality of descenders  38  via the plurality of discharging channels  361 , respectively. The ink which is not ejected from the plurality of nozzles  30  flows into the discharging manifold  36 . 
     The plurality of pressure chambers  37  are spaces provided on the plurality of nozzles  30 , respectively. The plurality of descenders  38  are formed from the plurality of pressure chambers  37  toward the plurality of nozzles  30 , respectively. The ink in each of the plurality of nozzles  37  is allowed to pass through one of the plurality of descenders  38  and to flow into one of the plurality of nozzles  30 . 
     The ejecting modules  242  has a structure in which a nozzle plate  100 , a channel member  200 , a vibration plate  300 , and the plurality of piezoelectric elements  35  are overlaid in the up-down direction  7 . The plurality of nozzles  30  are formed in the nozzle plate  100 . The supplying manifold  33 , the plurality of supplying channels  331 , the discharging manifold  36 , the plurality of discharging channels  361 , the plurality of pressure chambers  37 , and the plurality of descenders  38  are formed in the channel member  200 . Note that the channel member  200  may be a stacked body in which a plurality of plates are stacked on each other in the up-down direction  7 . The vibration plate  300  is stacked on the channel member  200 , and the vibration plate  300  covers the supply manifold  33 , the plurality of pressure chambers  37  and the discharging manifold  366 . The plurality of piezoelectric elements  35  are arranged side by side on the vibration plate  200 . 
     The plurality of piezoelectric elements  35  are positioned on the plurality of pressure chambers  37 , respectively. Each of the plurality of piezoelectric elements  35  is deformed by being applied with a voltage so as to reduce the volume of one of the plurality of pressure chambers  37 . In a case that the volume of a pressure chamber  37 , among the plurality of pressure chambers  37 , is reduced accompanying with the deformation of a certain piezoelectric elements  35  among the plurality of piezoelectric elements  35 , the ink stored in the pressure chamber  37  flows into a nozzle  30 , among the plurality of nozzles  30  via a descender  38 , among the plurality of descenders  38 , and is ejected from the nozzle  30  to the outside as a fine or minute ink droplet. The ink droplets of the ink are selectively ejected from the plurality of nozzles  30  to thereby cause the ink to be adhered, in a shape of an image and/or letter, to the sheet passing below the printing head  24 . 
     The pump  34  is driven while the ink is being ejected from the nozzle(s)  30 , namely, while the printing is being performed, thereby circulating the ink from the sub tank  31 , via the two channels  32 A and  21 B, and through the supplying manifold  33 , the plurality of pressure chambers  37 , the plurality of descenders  38  and the discharging manifold  36 . 
     As depicted in  FIG. 2 , the platen  25  is located at a location below the printing head  24 . An upper surface of the platen  25  is a surface supporting the sheet. Although not depicted in the respective drawings, an opening in which suction pressure is generated is formed in the upper surface of the platen  25 . By the suction pressure generated on the upper surface of the platen  25 , the sheet makes tight contact with the upper surface of the platen  25 . 
     As depicted in  FIGS. 2 and 3 , the heater  26  is positioned at a location which is above the conveyance route  22  and which is at the downstream of the printing head  24  and at the upstream of the conveyance roller pair  55 . Namely, in the front-rear direction  8 , the heater  26  is positioned between the conveyance roller pair  55  and the head  24 . The heater  26  has a part which overlaps with the platen  25  in the up-down direction  7 . In the present embodiment, a downstream end in the conveyance direction of the platen  25  is positioned at the downstream of an upstream end in the conveyance direction of the heater  26 . 
     The heater  26  is a so-called halogen heater and has a halogen lamp  40  as a heating element, a reflective plate  41 , and a casing  42 . The casing  42  has a substantially rectangular parallelepiped shape. An opening  43  along the left-right direction  9  is formed at a lower wall of the casing  42 . The heat from the halogen lamp  40  and/or the reflective plate  41  is radiated to the outside, via the opening  43 . The halogen lamp  40  is positioned in an internal space of the casing  42 . The halogen lamp  40  has a slender cylindrical shape of which longitudinal direction is the left-right direction  9 . In the internal space of the casing  42 , the reflective plate  41  is positioned at a location above the halogen lamp  40 . The reflective plate  41  is a metallic plate on which a ceramic film, etc., is coated or applied, and is curved to have a circular-arc shape of which center axis is in the vicinity of the opening  43 . Note that it is allowable to use, instead of using the reflective plate  41 , a halogen lamp  40  on which a ceramic film, etc., is coated. The heater  26  heats the ink adhered to the sheet passing a location below the opening  43 . The ink is heated to thereby allow the minute particles of the resin to undergo the glass transition, which in turn melts the minute particles of the resin. After the sheet has passed the location below the heater  26 , the sheet is cooled to thereby cure the molten resin, and to fix the ink to the sheet. 
     As depicted in  FIGS. 2 and 3 , a CIS  27  (contact image sensor: an example of a “reading sensor”) is positioned at a location above the conveyance route  22 , and at the downstream in the conveyance direction of the heater  26 . In a case that a reflected light, of a light emitted from a light source such as an LED and reflected by the sheet, is collected to a line sensor by a SELFOC (trade name) lens, the CIS  27  is configured to output an electric signal corresponding to the intensity of the reflected light received by the line sensor. The CIS  27  is arranged so that the left-right direction  9  is a read-line. The CIS  27  is provided so as to detect whether or not there is any defect in an image formed on the sheet by the printing head  24 . 
     As depicted in  FIGS. 2 and 3 , a cutter unit  28  is positioned in the conveyance route  22  at the downstream in the conveyance direction of the CIS  27 . The cutter unit  28  is constructed such that a cutter  45  is installed in a carriage  46 . The carriage  46  moves in the conveyance route  22  in the left-right direction  9 , by a non-illustrated belt driving mechanism, etc. The cutter unit  45  is positioned to as to cross the conveyance route  22  in the up-down direction  7 , and moves in the conveyance route  22  in the left-right direction  9 , accompanying with the movement of the carriage  46 . The sheet positioned in the conveyance route  22  is cut along the left-right direction  9  (an example of a “direction crossing the conveyance direction”) by the movement of the cutter  45 . 
     &lt;Arrangement of Respective Members in Internal Space of Casing  14 &gt; 
     As depicted in  FIG. 2 , a shortest distance A between the heater  26  and the discharge port  13  is longer than a shortest distance B between the printing head  24  and the heater  26  (A&gt;B). Here, the term “shortest distance” is the shortest distance among distances connecting the end parts of the respective elements, respectively, such as the heater  26 , the printing head  24 , etc. In the present embodiment, a distance in the front-rear direction  8  from an end part on the front side of the casing  42  to an end part on the rear side of the discharge port  13  is the shortest distance A. Further, in the present embodiment, a distance in the front-rear direction  8  from an end part on the front side of the printing head  24  to an end part on the rear side of the casing  42  is the shortest distance B. Noter that it is not necessarily indispensable that the shortest distance is the distance along the front-rear direction  8 . For example, as depicted in  FIG. 5 , in a case that the heater  26  is arranged to be shifted to the upper side in the up-down direction  8 , a distance from a lower corner part on the front side of the casing  42  to an end part on the rear side of the discharge port  13  becomes a shorted distance A′. Further, a distance from an end part on the front side of the printing head  24  to a lower corner part on the rear side of the casing  42  becomes to be the shortest distance B′. 
     Further, as depicted in  FIG. 2 , in the present embodiment, a shortest distance C between the heater  26  and the cutter unit  28  is longer than the shortest distance B (C&gt;B). Furthermore, a shortest distance D between the heater  26  and the CIS  27  is longer than the shortest distance B (D&gt;B). Namely, the CIS  27  and the cutter unit  28  are positioned at positions, respectively, which are farther from the printing head  24 , with respect to the heater  26 . In the present embodiment, a distance in the front-rear direction  8  from the end part on the front side of the casing  42  to an end part on the rear side of the cutter unit  28  is the shortest distance C. Further, in the present embodiment, a distance in the front-rear direction  8  from the end part on the front side of the casing  42  to an end part on the rear side of the CIS  27  is the shortest distance D. Furthermore, in the present embodiment, the shortest distance D between the heater  26  and the CIS  27  is longer than a shortest distance E between the heater  26  and the plurality of nozzles  30  (D&gt;E). 
     &lt;Effects of Embodiment&gt; 
     In a case that the printing apparatus  10  performs the printing operation, the halogen lamp  40  radiates the heat, and the heat radiation is generated in the surrounding of the heater  26 . According to the configuration of the printing apparatus  10 , however, it is possible to make the size along the front-rear direction  8  of the casing  14  to be small, while arranging, with respect to the heater  26 , the printing head  24 , the CIS  27 , the cutter unit  28  and the discharge port  13  so that there is no effect of the heat radiation from the heater  26 . 
     Further, in the conveyance route  22 , the printing head  24  and the heater  26  are positioned between the conveyance roller pair  54  and the conveyance roller pair  55  and any other conveyance roller is not positioned between the conveyance roller pair  54  and the conveyance roller pair  55 . Therefore, it is possible to reduce the size along the front-rear direction  8  of the casing  14  to be small. 
     Furthermore, since the heater  26  has the part overlapping with the platen  26  in the up-down direction  7  in the conveyance route  22 , it is possible to reduce the size along the front-rear direction  8  of the casing  14  to be small. 
     Moreover, since the discharge port  13  and the operation panel  17  are positioned in the front surface  14 A of the casing  14 , it is possible for the user to receive the sheet after the printing and discharged from the discharge port  13 , and to operate the operation panel  17 , on the side of the front surface  14 A of the casing  14 . Thus, there is provided a satisfactory operability. 
     Further, since the printing head  24  has the part overlapping with the sheet storing space  15  in the up-down direction  7 , it is possible to reduce the size along the up-down direction  7  and the front-rear direction  8  of the casing  14  to be small. 
     Furthermore, the printing head  24  has the structure in which the ink is circulated. The sub tank  31  is arranged at the position further away from the heater  26  than the printing head  24 . Namely, the distance from the sub tank  31  to the heater  26  is greater than the distance from the printing head  24  to the heater  26 . Accordingly, the sub tank  31  is less likely to be affected by the heat radiation of the heater  26 , than the printing head  24 , and the sub tank  31  is a more cooled state than the printing head  24 . Accordingly, it is possible to adjust the temperature of the printing head  24  to be not more than a predetermined temperature, by the circulation of the ink. With this, the printing head  24  is less likely to adversely affected by the head radiation of the heater  26 . For example, it is possible to prevent such a situation that any distortion is generated in the printing head  24  due the heat received by the printing head  24  from the heater  26 , and that the ejection of the ink is adversely affected. Further, it is possible to prevent such a situation that adhesion between the constituent elements constructing the printing head  24  is disintegrated (peeled off from each other) due to, for example, any distortion generated in the printing head  24 , and that the printing head  24  is destroyed. 
     Furthermore, the ejecting module  242  has the configuration in which the ink in the vicinity of the nozzles  30  is circulated during the printing operation. Accordingly, any drying of the ink and/or any increase in the viscosity of the ink due to the heat received from the heater  26  are/is less likely to be generated. 
     &lt;Modifications&gt; 
     In the above-described explanation, each of the shortest distance A, the shortest distance B, the shortest distance C and the shortest distance D is explained as being defined as the shortest distance among the distances between the respective ends of the respective constituent elements such as the heater  26  and the printing head  24 , etc., for the purpose of explaining the arrangement relationship among the respective constituent elements. It is allowable, however, to define each of the shortest distance A, the shortest distance B, the shortest distance C and the shortest distance D as the shortest distance among the distances between the respective ends of the respective constituent elements such as the halogen lamp  40  and the printing head  24 , etc., instead of the heater  26 . 
     Namely, a shortest distance A between an end part on the front side of the halogen lamp  40  and the end part on the rear side of the discharge port  13  is longer than a shortest distance B between the end part on the front side of the printing head  24  and an end part on the rear side of the halogen lamp  40  (A&gt;B). Further, a shortest distance C between the end part on the front side of the halogen lamp  40  and the end part on the rear side of the cutter unit  28  is longer than the shortest distance B (C&gt;B). Furthermore, a shortest distance D between the end part on the front side of the halogen lamp  40  and the end part on the rear side of the CIS  27  is longer than the shortest distance B (D&gt;B). Namely, the CIS  27  and the cutter unit  28  are positioned at positions, respectively, which are farther from the printing head  24 , with respect to the halogen lamp  40 . 
     Moreover, it is allowable to define the arrangement of the respective members in the internal space of the casing  14  by a distance A, a distance B, a distance C and a distance D each of which is a direction along the conveyance direction (in the above-described embodiment, the front-rear direction  8 ), instead of the shortest distance A, the shortest distance B, the shortest distance C and the shortest distance D as described above. In this case, it is not necessary that each of the distance A, the distance B, the distance C and the distance D is the shortest distance. In the resent embodiment, the conveyance direction is a direction along a horizontal direction. Accordingly, it is allowable to define the arrangements of the respective members in the internal space of the casing  14  based on the distance A, the distance B, the distance C and the distance D each of which is the distance along the horizontal direction, instead of the shortest distance A, the shortest distance B, the shortest distance C and the shortest distance D as described above. 
     Namely, a distance A along the front-rear direction  8  between the end part on the front side of the heater  26  (namely, the end part on the front side of the casing  42 ) and the end part on the rear side of the discharge port  13  is longer than a distance B along the front-rear direction  8  between the end part on the front side of the printing head  24  and the end part on the rear side of the heater  26  (namely, the end part on the rear side of the casing  42 ) (A&gt;B). Further, a distance C along the front-rear direction  8  between the end part on the front side of the heater  26  and the end part on the rear side of the cutter unit  28  is longer than the distance B (C&gt;B). Furthermore, a distance D along the front-rear direction  8  between the end part on the front side of the heater  26  and the end part on the rear side of the CIS  27  is longer than the distance B (D&gt;B). 
     Moreover, as a modification of the above-described embodiment, it is allowable to provide a cooling mechanism  48  on the printing head  24 , as depicted in  FIG. 6 . In a case that the cooling mechanism  48  is a cooling mechanism by (based on) the air cooling, a heat sink made of a metal is provided on the printing head  24 . Alternatively, in a case that the cooling mechanism  48  is a cooling mechanism by the water cooling, a water cooling block which is connected to a pump and in which a refrigerant medium is allowed to circulate may be provided on the printing head  24 . It is allowable that the cooling mechanism  48  is configured to cool a non-illustrated driving IC configured to drive the piezoelectric elements  35 , or is provided to adjust the temperature of the ink inside the printing head  24 . 
     Further, in the embodiment as described above, the heater  26  has the halogen lamp  40  as the heating element. The present disclosure, however, is not limited to this. For example, it is allowable to use a carbon heater, a ceramic heater, etc., instead of using the heater  26 . 
     In the above-described embodiment, the printing apparatus  10  is provided with the heater  26 . The heater  26  heats the sheet to which the ink has been ejected so as to fix the ink to the sheet. As described above, the ink is heated directly or indirectly by the heater  26 , to thereby subject the minute particles of the resin included in the ink to the glass transition. Then, the sheet is cooled to thereby cure the resin which has undergone the glass transition. In such a manner, the heater  26  applies the energy for subjecting the minute particles of the resin included in the ink to the glass transition to thereby cure the ink and to fix the ink to the sheet. In other words, the heater  26  functions as a fixing device which applies the energy necessary for curing ink so as to fix the ink to the sheet. Note that in the above-described disclosure, the ink is explained as being exemplified by a latex ink. The present disclosure, however, is not limited to or restricted by a thermo-curable ink such as the latex ink. For example, it is allowable to use a water-based ink such as a dye ink, a pigment ink, etc., as the ink. In such a case also, the heater  26  functions as a fixing device which applies the energy required for drying the ink adhered to the sheet so as to fix the ink to the sheet. 
     In the present disclosure, the fixing device which applies the energy required for curing the ink so as to fix the ink to the sheet is not limited to the heater which applies a thermal energy to the ink. For example, as a printing apparatus  310  as depicted in  FIGS. 8 and 9 , it is allowable to use a UV light source  326  as the fixing device. The printing apparatus  310  as depicted in  FIG. 8  has a similar configuration as that of the printing apparatus  10  of the above-described embodiment, except that the printing apparatus  310  does not have the heater  26 , but instead has a UV light source  326 . Same reference numerals are affixed to configurations, of the printing apparatus  310 , which are similar to those of the printing apparatus  10 , and the explanation therefor will be omitted. 
     The UV light source  326  has a UV lamp  340  which radiates a UV light, a reflective plate  341  and a casing  342 . Since the outer shape of the casing  342  is substantially same as the outer shape of the casing  42  of the heater  26 , any explanation therefor will be omitted. An opening  343  along the left-right direction  9  is formed in a lower wall of the casing  342 . The UV light from the UV lamp  340  and/or the reflective plate  341  is radiated to the outside, via the opening  343 . In the internal space of the casing  342 , the reflective plate  341  is positioned at a location above the UV lamp  340 . The reflective plate  341  is formed of, for example, a surface-treated aluminum member in which an anodic oxide film is formed on a surface thereof, and is capable reflecting the UV light. Further, the reflective plate  341  is curved to have a circular-arc shape of which center axis is in the vicinity of the opening  343 . Note that it is allowable to arrange a condensing lens between the UV lamp  340  and the sheet passing at a location below the opening  343 . In such a case, it is possible to efficiently collect the UV light radiated from the UV lamp  240  and to irradiate the sheet with the UV light. 
     In this modification, a UV curable ink is used as the ink. Further, the UV light source  326  radiates the UV light to the UV curable ink adhered to the sheet passing the location below the opening  343 . By radiating the UV light to the UV curable ink, the UV curable ink is cured. With this, the UV curable ink is fixed to the sheet. 
     Further, in the above-described embodiment, the tank  70  is of the cartridge type which is attachable/detachable with respect to the casing  14 ; in a case that the cover  16  is opened, the tank  70  is removable toward the front side from the casing  14 . Instead of this, it is allowable that the tank  70  is fixed in the internal space of the casing  14 , and that the ink can be replenished in the storing space of the tank  70  via an inlet port. 
     Furthermore, the tank  70  is not limited to a tank storing the ink of one color which is black, and may be tanks which store, for example, four color inks which are black, yellow, cyan and magenta, respectively. 
     Moreover, it is not necessarily indispensable that the discharge port  13  is formed in the front surface  14 A of the casing  14 . For example, it is allowable that the discharge port  13  is provided on the upper surface of the casing  14 , and that a part of the roll paper  11  after the printing which pass through the discharge port  13  is discharged obliquely upward or upward. 
     Further, although the printing apparatus  10  as described above is capable of performing printing on the roll paper  11 , the present disclosure is not limited to this. It is allowable that the printing apparatus  10  is an apparatus which performs printing on the roll paper  11  and a cut paper sheet (cut paper), or may be an apparatus which performs printing only on the cut paper sheet. 
     Furthermore, in the above-described embodiment, the CIS  27  and the cutter unit  28  are positioned in the inside of the casing  14 . Instead of this, it is allowable that the CIS  27  and the cutter unit  28  are positioned, at the outside of the casing  14 , at the downstream in the conveyance direction of the discharge port  13 , as depicted in  FIG. 7 . Moreover, it is allowable that the CIS  28  is omitted. 
     Further, although the above-described printing apparatus  10  is used in a state that the front surface  14 A and the rear surface  14 B of the casing  14  are along the up-down direction  7  and the left-right direction  9 , a posture in which the printing apparatus  10  is used is not limited to this. 
     Further, although the ejecting module  242  of the above-described embodiment is explained while being exemplified by having one nozzle array (row) in which the plurality of nozzles  30  are aligned in the left-right direction  9 , the present embodiment is not limited to this. It is allowable that an ejecting module in which a plurality of nozzle rows are arranged side by side in the front-rear direction  9  is used for the printing apparatus  10 . 
     Furthermore, although the printing head  24  as described above is explained as having one ejecting module  242 , the present embodiment is not limited to this. The printing apparatus  10  may be a printing apparatus  10  provided with, as the printing head  24 , a line head in which a plurality of ejecting modules  242  are installed in one carriage  241 . 
     Moreover, in the above-described embodiment, although the printing head  24  ejects the ink in the state that the printing head  24  stands still at the predetermined printing position during the printing operation, the printing apparatus  10  may be a printing apparatus  10  of the serial system in which the printing head  24  ejects the ink while the printing head  24  moves in the left-right direction  9  during the printing operation. 
     Further, in the above-described embodiment, although the printing head  24  is explained as being provided with the ejecting module  242  of such a type wherein the pump  34  is driven to thereby circulate the ink in the vicinity of the nozzles  30  during the printing operation, it is allowable to use an ejecting module in which an ink circulating route is formed only for the manifold, without circulating the ink in the individual channels, as disclosed in Japanese Patent Application Laid-open No. 2016-190431. 
     Further, the above-described embodiment is explained as making the ink inside the ejecting module  242  to circulated by the pump  34  during the printing operation. It is allowable, however, that the ink inside the ejecting module  242  is not circulated during the printing operation. Also in this case, a new ink is always supplied from the tank  70  or the sub tank  31 , due to the ejection of the ink by the printing operation. Since the ink in a cooled state than the printing head  24  is supplied from the tank  70  and/or the sub tank  31 , it is possible to cool the printing head  24 . 
     Furthermore, in the above-described embodiment, although the route for circulating the ink is formed in the ejecting module  242 , it is allowable to use an ejecting module which does not have any route for circulating the ink. 
     The present disclosure can be applied to the following aspects. In the printing apparatus the fixing device may be a heater having a heating element, or may be a UV light source. Further, the printing apparatus may further include a cutter which is positioned in the casing, at a location, of the conveyance route, at the downstream in the conveyance direction of the heater, and which cuts the sheet in a direction crossing the conveyance direction, wherein a shortest distance C between the heater and the cutter may be longer than the shortest distance B. 
     According to the above-described configuration, it is possible to reduce the size along the conveyance direction of the casing, while arranging the cutter and the heater such that any effect of the heat radiation from the heater is not generated. 
     The printing apparatus may further include a cutter which is positioned at the downstream in the conveyance direction of the discharge port, and which cuts the sheet in a direction crossing the conveyance direction. 
     The printing apparatus may further include a reading sensor which is positioned in the casing, at a location, of the conveyance route, at the downstream in the conveyance direction of the heater, and which reads an image of a print surface of the sheet, wherein a shortest distance D between the fixing device and the reading sensor may be longer than the shortest distance B. 
     According to the above-described configuration, it is possible to reduce the size along the conveyance direction of the casing while arranging the reading sensor and the heater such that any effect due to the heat radiation of the fixing device such as the heater, etc., is not generated. 
     The printing apparatus may further include a reading sensor which is positioned at the downstream in the conveyance direction of the discharge port, and which reads an image of a print surface of the sheet. 
     The printing apparatus may further include: a first conveyance roller which is positioned in the casing at an upstream in the conveyance direction of the printing head, and which conveys the sheet in the conveyance direction; and a second conveyance roller which is positioned in the casing at the downstream in the conveyance direction of the heater, and which conveys the sheet in the conveyance direction. It is allowable that the printing head and the heater are positioned between the first conveyance roller and the second conveyance roller in the conveyance direction, and it is further allowable that another conveyance roller is not positioned between the first conveyance roller and the second conveyance roller in the conveyance direction. 
     According to the above-described configuration, it is possible to reduce the size along the conveyance direction of the casing while arranging the printing head and the heater in the range between the first conveyance roller and the second conveyance roller. 
     The printing apparatus may further include a platen which is positioned to face the printing head in the casing, and which supports the sheet. The platen may have a part overlapping with the fixing device in a direction orthogonal to the conveyance direction and orthogonal to a supporting surface of the platen. 
     According to the above-described configuration, it is possible to reduce the size along the conveyance direction of the casing while arranging the printing head, the platen and the fixing device in the range between the first conveyance roller and the second conveyance roller. 
     The printing apparatus may further include an operation panel which is positioned in a surface, of the outer wall of the casing, having the discharge port formed therein, and via which an input from a user is received. 
     According to the above-described configuration, it is possible to receive the sheet, after printing and discharged from the discharge port, on the surface, of the outer wall of the casing, in which the discharge port is formed and to operate the operation panel on the same surface. Thus, a satisfactory operability is provided. 
     The printing apparatus may further include a sheet storing space storing the sheet which is a roll-shaped sheet before printing, with a direction crossing the conveyance direction being a roll axis direction of the roll-shaped sheet. The printing head may have a part overlapping with the sheet storing space in a direction orthogonal to the conveyance direction and orthogonal to the roll axis direction. 
     According to the above-described configuration, a small-sized casing is realized by arranging the sheet storing space and the printing head efficiently in the casing. 
     The printing apparatus may further include: a tank configured to store the ink; a channel member defining a channel communicating the printing head and the tank with each other; and a pump which circulates the ink, via the channel, between the printing head and the tank. 
     According to the above-described configuration, since the printing head is cooled by the ink circulated in the printing head, the printing head is less likely to be affected by the heat radiation of the fixing device such as the heater, etc. 
     The printing head may have: a plurality of nozzles via which the ink to be ejected flows, and a manifold communicating with the plurality of nozzles; the channel may be communicated with the manifold; and the pump may be operated so as to circulate the ink between the manifold and the tank, via the channel. 
     The printing head may have a cooling mechanism by air coiling or water cooling. 
     The ink may be a liquid including minute particles of a resin, or may be a UV-curable ink. 
     The heating element may radiate an infrared ray. 
     According to a second aspect of the present disclosure, there is provided a printing apparatus including: a casing; a conveyance route which is formed in an internal space of the casing and through which a sheet passes in a conveyance direction toward a discharge port opened in an outer wall of the casing; a printing head which is positioned in the casing and which ejects an ink to the sheet passing through the conveyance route; and a heater which has a heating element, which is positioned in the casing, at a location, of the conveyance route, at a downstream in the conveyance direction of the printing head, and which heats the sheet having the ink adhered thereon. A shortest distance A between the heating element and the discharge port is longer than a shortest distance B between the printing head and the heating element. 
     The printing apparatus may further include cutter which is positioned in the casing, at a location, of the conveyance route, at the downstream in the conveyance direction of the heater, and which cuts the sheet in a direction crossing the conveyance direction. A shortest distance C between the heating element and the cutter may be longer than the shortest distance B. 
     The printing apparatus may further include a reading sensor which is positioned in the casing, at a location, of the conveyance route, at the downstream in the conveyance direction of the heater, and which reads an image of a print surface of the sheet. A shortest distance D between the heating element and the reading sensor may be longer than the shortest distance B. 
     According to a third aspect of the present disclosure, there is provided a printing apparatus including: a casing; a conveyance route which is formed in an internal space of the casing and through which a sheet passes in a conveyance direction toward a discharge port opened in an outer wall of the casing; a printing head which is positioned in the casing and which ejects an ink to the sheet passing through the conveyance route; and a fixing device which is positioned in the casing, at a location, of the conveyance route, at a downstream in the conveyance direction of the printing head, and which is configured to apply, to the sheet having the ink adhered thereon, an energy for fixing the ink so as to fix the ink to the sheet. A distance A along the conveyance direction between the fixing device and the discharge port is longer than a distance B along the conveyance direction between the printing head and the fixing device. 
     The printing apparatus may further include a cutter which is positioned in the casing, at a location, of the conveyance route, at the downstream in the conveyance direction of the heater, and which cuts the sheet in a direction crossing the conveyance direction. A distance C along the conveyance direction between the fixing device and the cutter may be longer than the distance B. 
     The printing apparatus may further include a reading sensor which is positioned in the casing, at a location, of the conveyance route, at the downstream in the conveyance direction of the fixing device, and which reads an image of a print surface of the sheet. A distance D along the conveyance direction between the fixing device and the reading sensor may be longer than the distance B. 
     According to the present disclosure, any adverse effect of the heat radiated by the fixing device, such as the heater, etc., positioned in the casing of the printing apparatus, is less likely to occur.