Patent Publication Number: US-9840101-B2

Title: Droplet ejection apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2016-021661 filed Feb. 8, 2016. 
     BACKGROUND 
     Technical Field 
     The present invention relates to a droplet ejection apparatus. 
     SUMMARY 
     According to an aspect of an exemplary embodiment of the invention, here is provided a droplet ejection apparatus including: 
     an ejecting mechanism in which plural ejection units which eject droplets from a nozzle to a transported recording medium are disposed in a zig-zag form in an intersection direction that intersects a transport direction of the recording medium; and 
     a release unit which releases humidified air from a release port which is open in the recording medium side between ejection units in the intersection direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present invention will be described in detail based on the following figures, wherein: 
         FIG. 1  is a schematic diagram illustrating a configuration of an image apparatus according to an exemplary embodiment; 
         FIG. 2  is a schematic diagram illustrating a configuration of a release unit and an ejection head according to an exemplary embodiment viewed from the upstream side in the transport direction of a continuous paper; 
         FIG. 3  is a bottom view illustrating the configuration of the release unit, and the ejection head according to an exemplary embodiment; 
         FIG. 4  is a bottom view illustrating the configuration of the release unit and the ejection head according to a first modification example; 
         FIG. 5  is a schematic diagram illustrating a configuration of the release unit and the ejection head according to a second modification example viewed from the upstream side in the transport direction of a continuous paper; 
         FIG. 6  is a bottom view illustrating the configuration of the release unit and the ejection head according to a second modification example; and 
         FIG. 7  is a bottom view illustrating the configuration of the release unit and the ejection head according to a third modification example. 
     
    
    
     DETAILED DESCRIPTION 
     Below, an example of the exemplary embodiments of the invention will be described with reference to the drawings. 
     Image Forming Apparatus  10   
     First, the is forming apparatus  10  as an example of a droplet ejection apparatus that ejects droplets will be described.  FIG. 1  is a schematic diagram illustrating the configuration of the image forming apparatus  10 . 
     As illustrated in  FIG. 1 , the image forming apparatus  10  is provided with a first image forming apparatus  11  that forms an image on the surface of a continuous paper P (example of a recording medium), a second image forming apparatus  12  that forms an image on the rear surface of the continuous paper P, a transport mechanism  17  that transports the continuous paper P, and a controller  90  that controls each portion of the image forming apparatus  10 . 
     Transport Mechanism  17   
     The transport mechanism  17  includes a reel-out roll  72  that reels out the continuous paper P, a winding roll  74  that winds up the continuous paper P, a reversing mechanism  80  that causes the front and rear of the continuous paper P to be reversed, and plural transport rolls  77  that transport the continuous paper P. The winding roll  74  is driven to rotate by a driving unit  78 . Accordingly, the winding roll  74  winds up the continuous paper P and the reel-out roll  72  reels out the continuous paper P. 
     The plural transport rollers  77  wound by the continuous paper P between the reel-out roll  72  and the winding roll  74 . Accordingly, the transport path of the continuous paper P from the reel-out roll  72  to the winding roll  74  is determined. The plural transport rollers  77  is driven to follow the continuous paper P that proceeds to the winding roll  74  side by the winding roll  74  winding up the continuous paper P. 
     In the exemplary embodiment, the first image forming apparatus  11  is disposed on the upstream side (reel-out roll  72  side) in the transport path from the reel-out roll  72  to the winding roll  74 , and the second imago forming apparatus  12  is disposed on the downstream side (winding roll  74  side). 
     The reversing mechanism  80  is disposed between the first image forming apparatus  11  and the second image forming apparatus  12  on the transport path from the reel-out roll  72  to the winding roll  74 . Accordingly, after the reversing mechanism  89  causes the front and rear of the continuous paper P passing through the first image forming apparatus  11  while borne reeled out by the reel-out, roll  72  to be reversed, and the continuous paper P for which the front and rear are reversed passes through the second image firming apparatus  12 , the continuous paper P is wound up by the winding roll  74 . In each drawing, the transport direction of the continuous paper P (below, may also be simply referred to as, “transport direction”) is indicated, as appropriate, by the arrow A. 
     First Image Forming Apparatus  11   
     The first image forming apparatus  11  is provided with an image forming apparatus main body  13  (housing), a first ejection unit  30  that ejects ink droplets (example of droplets) on the continuous paper P, a first drying unit  50  which causes the ink droplets ejected on the continuous paper P to dry, and a cooling roll  79  that cools the continuous paper P. 
     The first ejection unit  30 , the first drying unit  50 , and the cooling roll  79  are disposed in this order from the upstream side in the transport direction of the continuous paper P toward the downstream side. Accordingly, the ejecting operation, the heating operation, and the cooling operation are executed in this order with respect to each portion of the continuous paper P transported by the transport mechanism  17 . 
     First Ejection Unit  30   
     The first ejection unit  30  includes first ejection heads  32 Y,  32 M,  32 C, and  32 K that eject each of yellow (Y), magenta (M), cyan (C), and black (K) ink droplets on the continuous paper P. An image is formed on the continuous paper P by each color of ink droplet being ejected on the continuous paper P from the first ejection heads  32 Y,  32 M,  32 C, and  32 K (below, referred to as  32 Y to  32 K). 
     First Drying Unit  50   
     The first drying unit  50  includes a housing  52  and an infrared ray heater (not shown) as a heat source disposed in the interior of the housing  52 . Plural infrared ray heaters (not shown) are disposed along the vertical direction facing the image forming surface (surface on which ink droplets are ejected from the first ejection unit  30 ) of the continuous paper P transported in the interior of the housing  52 . In the first drying unit  50 , the ink on the image forming surface is dried by the plural infrared ray beaters (not shown) heating the image forming surface of the continuous paper P. 
     Cooling Roll  79   
     The image forming surface of the continuous paper P is wound on the outer peripheral surface of the cooling roll  79  as illustrated in  FIG. 1 . Accordingly, the outer peripheral surface of the cooling roll  79  cools the continuous paper P through contact with the image-forming surface of the continuous paper P. The cooling roll  79  is driven to follow the continuous paper P that proceeds to the winding roll  74  side, and functions as a transport roller. 
     Second Image Forming Apparatus  12   
     The second image forming apparatus  12  is provided with an image forming apparatus main body  14  (housing), a second ejection unit  40  that ejects ink droplets (example of droplets) on the continuous paper P, a second drying unit  60  which causes the ink droplets ejected on the continuous paper P to dry, and a release unit  100  (refer to  FIG. 2 ) that releases humidified air. 
     Second Drying Unit  60   
     The second drying unit  60  includes a housing  62  and an infrared ray heater (not shown) as a heat source disposed in the interior of the housing  62 . Plural infrared ray beaters (not shown) are disposed along the vertical direction facing the image forming surface (surface on which ink droplets are ejected from the second ejection unit  40 ) of the continuous paper P transported in the interior of the housing  62 . In the second drying unit  60 , the ink on the image thrilling surface is dried by the plural infrared ray heaters (not shown) heating the image forming surface of the continuous paper P. 
     Second Ejection Unit  40   
     The second ejection unit  40  includes second ejection heads  42 Y,  42 M,  42 C, and  42 K (example of an ejecting mechanism) that eject each of yellow (Y), magenta (M), cyan (C), and black (K) ink droplets on the continuous paper P. An image is thrilled on the continuous paper P by each color of ink droplet being ejected on the continuous paper P from the second ejection heads  42 Y,  42 M,  42 C, and  42 K (below, referred to as  42 Y to  42 K). 
     The second ejection heads  42 Y to  42 K are in this order toward the upstream side in the transport direction of the continuous paper P. That is, the second ejection head  42 K from the second ejection heads  42 Y to  42 K is disposed further to the upstream side in the transport direction, and the second ejection head  42 Y is disposed further to the downstream side in the transport direction. Each of the second ejection beads  42 Y and  42 K has a length in the width direction (intersection direction that intersects the transport direction of the continuous paper P) of the continuous paper P. 
     Each second ejection head  42 Y to  42 K flintier includes plural unit heads  20  that eject ink droplets from the nozzles  46  to the transported continuous paper P and a support member  28  that supports the plural unit heads  20 , as illustrated in  FIGS. 2 and 3 . The support member  28  has a length along the width direction of the continuous paper P. Only a portion of the nozzles  46  is depicted in  FIG. 3 . 
     In the exemplary embodiment, each second ejection head.  42 Y to  42 K includes an odd number of five unit heads  20 A,  20 B,  20 C,  20 D, and  20 E (below, referred to as  20 A to  20 E). The five unit beads  20 A to  20 E are disposed in a zig-zag pattern in the width direction (below, may be referred to simply as the width direction) of the continuous paper P. The width direction of the continuous paper P in each drawing is indicated, as appropriate, by the arrow B. 
     Specifically, the five unit heads  20 A to  20 E are disposed in a zig-zag pattern as outlined below. That is, the unit heads  20 B and  20 D from the five unit heads  20 A to  20 E are disposed with a gap S 2  along the width direction of the continuous paper P, thereby forming a first row  91 . The unit heads  20 A,  20 C and  20 E are disposed with gaps S 1  and S 3  along the width direction of the continuous paper P, thereby forming the second row  92 . 
     The first row  91  is disposed to the upstream side in the transport direction of the continuous paper P with respect to the second row  92 . That is, the number of unit heads  20  disposed in the width direction of the continuous paper P on the upstream side in the transport direction is lower than the number of unit heads  20  disposed in the width direction of the continuous paper P on the downstream side in the transport direction. 
     The gap S 2  of the first row  91  and the gaps S 1  and S 3  of the second row  92  are shifted in the width direction of the continuous paper P. The end portion in the longitudinal direction (end portion an the B direction side) of the n-th (except for the final number) unit head  20  and the end portion in the longitudinal direction of the n+1th (end portion on the −B direction side) unit head  20  are disposed overlapping viewed from the transport direction counting in the longitudinal direction (direction of arrow B) from one end portion (end portion in −B direction) in the longitudinal direction of each of the second ejection heads  42 Y to  42 K. 
     In this way, each of the second ejection heads  42 Y to  42 K have plural unit heads  20  disposed in a zig-zag pattern, and form a head unit (head module) with the plural unit heads  20 . 
     Release Unit  100   
     The release unit  100  includes a humidifying device  102 , an air blower  104 , plural ducts  110 , a humidity sensor  120  (hydroscope) as illustrated  FIG. 2 . Specifically, the release unit  100  includes five ducts  111 ,  112 ,  113 ,  114 ,  115  (below, referred to as  111  to  115 ) that is the same number as that of the unit heads  20  in each second ejection head  42 Y to  42 K, as illustrated in  FIG. 3 . 
     In  FIG. 3 , although the second ejection beads  42 Y and  42 M are not depicted, the second ejection heads  42 Y and  42 M are also formed similarly to the second ejection heads  42 C and  42 K in  FIG. 3 . 
     Each duct  111  to  115  is a formation member that forms a through path  108  (refer to  FIG. 2 ). The ducts  111  to  115  each include release ports  121 ,  122 ,  123 ,  124 , and  125  (below, referred to as  121  to  125 ) that are disposed adjacent to the unit heads  20 , and that are open to the continuous paper P side. 
     The release ports  121  and  125  are each open in the upstream side in the transport direction with respect to unit heads  20 A and  20 E, and are disposed on the row of the first row  91 . 
     The release ports  122  and  124  are respectively disposed in the gap S 1  between the unit head  20 A and  20 C and the gap S 3  between the unit head  20 C and  20 E in each second ejection head  42 Y to  42 K, when viewed from below as illustrated in  FIG. 3  (seen from the nozzle  46  side). 
     The release port  123  is disposed in the gap S 2  between the unit heads  20 B and  20 D in each second ejection head  42 Y to  42 K when viewed from below (seen from the nozzle  46  side). 
     In this way, the release ports  122 ,  123 , and  124  are open to the continuous paper P side between the plural unit heads  20  in the width direction (longitudinal direction of the second ejection heads  42 Y to  42 K) of the continuous paper P. The release ports  121  to  125  are disposed in a zig-zag pattern in the width direction of the continuous paper P by being disposed as described above. 
     The humidity sensor  120  is disposed on the end portion in the longitudinal direction of any of the second ejection heads  42 Y to  42 K. In the example illustrated in  FIG. 3 , the humidity sensor  120  is disposed on the end portion in the longitudinal direction of the second ejection head  42 K. The humidity sensor  120  measures the humidity at the end portion of the longitudinal direction of the second ejection head  42 K, and transmits the measurement results (humidity information) to the controller  90 . The controller  90  drives the humidifying device  102  and the air blower  104  in a case where the humidity measured by the humidity sensor  120  is lower than a predetermined reference humidity. The reference humidity is set to a range of 30% or more to 40% or less at 25° C. 
     When the humidifying device  102  is driven by the controller  90 , water is evaporated due to heating and water vapor is generated. When the air blower  104  is driven by the controller  90 , the water vapor generated by the humidifying device  102  passes through the through path  108  of each duct  111  to  115  along with air and is sent to the release ports  121  to  125 . Accordingly, humidified air is released from the release ports  121  to  125 . 
     The humidified air released from the release ports  121  to  125  is diffused in the periphery of the release ports  121  to  125  between the release ports  121  to  125  and the continuous paper P, and supplied to the space under the nozzle  46  of the unit head  20  in the periphery of the release ports  121  to  125 . In particular, the humidified air released from the release ports  121  to  125  is carried to the downstream side in the transport direction by the air flow generated by the continuous paper P being transported. Therefore, much of the humidified air released from the release ports  121  to  125  is easily supplied to the space below the nozzle  46  of the unit head  20  on the downstream side in the transport direction with respect to the release ports  121  to  125 . 
     It should be noted that it is desirable that gap between each of the second ejection heads  42 Y to  42 K be made smaller or embedded by an elastic body so that the humidified air does not escape. 
     Actions According to Exemplary Embodiment 
     Next the action according to the exemplary embodiment will be described. 
     In the exemplary embodiment, the humidifying device  102  and the air blower  104  are driven by the controller  90  in a case where the humidity measured by the humidity sensor  120  is lower than a predetermined reference humidity. Accordingly, the humidifying device  102  causes the water to be evaporated due to heating, thereby generating water vapor. The water vapor generated by the humidifying device  102  passes through the through path  108  of each duct  111  to  115  along with air and is sent to the release ports  121  to  125  by the air blower  104 . 
     In this way, the humidified air is released from the release ports  121  to  125  by the water vapor and air being sent to the release ports  121  to  125 . The humidified air released from the release ports  121  to  125  is diffused in the periphery of the release ports  121  to  125  between the release ports  121  to  125  and the continuous paper P, and supplied to the space under the nozzle  46  of the unit head  20  in the periphery of the release ports  121  to  125 . 
     In the exemplary embodiment, the release ports  122 ,  123 , and  124  are disposed between the unit heads  20  in the width direction (longitudinal direction of the second ejection heads  42 Y to  42 K) of the continuous paper P. Therefore, the release ports  122 ,  123 , and  124  are closer with respect to the unit heads  20  disposed on both sides in the width direction with respect to the release ports  122 ,  123 , and  124  than a configuration (comparative example) where the release ports  122 ,  123 , and  124  are open at a position separated from the space between the unit heads  20  in the width direction of the continuous paper P. 
     Therefore, when the humidified air released from the release ports  122 ,  123 , and  124  is diffused, the humidified air is more effectively supplied to the space below the nozzles  46  of the unit heads  20  disposed on both sides than the comparative examples, and drying of the nozzles  46  is suppressed. 
     In the exemplary embodiment, the release ports  122 ,  123 , and  124  in the gaps S 1 , S 2 , and S 3  between the unit heads  20  in the width direction (longitudinal direction of the second ejection heads  42 Y to  42 K) of the continuous paper P. That is, the release ports  122 ,  123 , and  124  are disposed using the dead space of each second ejection head  42 Y to  42 K. Therefore, drying of the nozzles  46  is suppressed while maintaining sire reductions of each second ejection head  42 Y to  42 K. 
     In the exemplary embodiment, the number of unit heads disposed in the width direction of the continuous paper P on the upstream side in the transport direction is lower than the number of unit heads  20  disposed in the width direction of the continuous paper P on the downstream side in the transport direction. 
     Here, the humidified air released from the release ports  121  to  125  is carried to the downstream side in the transport direction by the air flow generated by the continuous paper P being transported. Accordingly, the humidified air is not easily supplied to the unit head  20  disposed on the upstream side in the transport direction. 
     In the exemplary embodiment, because there are few unit heads  20  on the upstream side in the transport direction which are not easily supplied with humidified air, the humidified air is more easily supplied to the unit head  20  and drying of the nozzles  46  is effectively suppressed compared to a case where the number of unit heads  20  on the upstream side in the transport direction is greater than the number of unit heads  20  on the downstream side in the transport direction. 
     The release unit  100  may have a configuration which does not include the ducts  111  and  115  (release ports  121  and  125 ). At least one of the ducts  112 ,  113 , and  114  (release ports  122 ,  123 , and  124 ) may be disposed in the release unit  100 . 
     In the exemplary embodiment, although the release unit  100  is provided with respect to the second ejection heads  42 Y to  42 K, the release unit  100  instead or in addition may be provided with respect to the first ejection heads  32 Y to  32 K. 
     In the exemplary embodiment, although a continuous paper P is used as the recording medium, a cut sheet or the like in which the length in the transport direction is made a predetermined length may be used. 
     Release Unit  150  According to First Modification Example 
     Next, the release unit  150  according to the first modification example will be described. Below, the portions differing from the release unit  100  will be described, and description of the same parts as the release unit  100  will not be provided, as appropriate. 
     The release unit  150  includes the ducts  162  and  163 , as illustrated in  FIG. 4 , in addition to the humidifying device  102 , air blower  104 , humidity sensor  120 , and the ducts  111  to  115  provided in second ejection head  42 Y to  42 K. The release unit  150  differs from the release unit  100  on the feature of having the ducts  162  and  163  in addition to the ducts  111  to  115 . 
     The ducts  162  and  163  include release ports  172  and  173  that are disposed adjacent on the upstream side in the transport direction with respect to the unit heads  20 B and  20 D in the second ejection head  42 K that is furthest to the upstream side in the transport direction, respectively. The release ports  172  and  173  are open to the continuous paper P side, similarly to the release ports  121  to  125 . 
     Accordingly, the humidified air is released from the release ports  172  and  173 , in addition to the release ports  121  to  125 , in the release unit  150 . 
     The humidified air released from the release ports  172  and  173  is transported to the downstream side in the transport direction by the air flow arising by the continuous paper P being transported, and is supplied to the space below the nozzles  46  of the unit heads  20 B and  20 D in the second ejection head  42 K. Accordingly, drying of the nozzles  46  of the unit heads  20 B and  20 D is suppressed compared to a configuration not having the release ports  172  and  173 . 
     It should be noted that the ducts  162  and  163  may be applied to the release unit  200  and the release unit  300 , described later. 
     Release Unit  200  According to Second Modification Example 
     Next, the release unit  200  according to second modification example will be described. Below, the portions differing from the release unit  100  will be described, and description of the same parts as the release unit  100  will not be provided, as appropriate. 
     The release unit  200  includes the ducts  211  to  212  in place of the duct  111  in the second ejection head  42 K, includes the duets  231 ,  232 , and  233  (below, referred to  231  to  233 ) in place of the duct  113 , and includes the ducts  251  and  252 , in place of the duct  115 , as illustrated in  FIG. 5 . 
     The release unit  200  includes the ducts  221 ,  222 ,  223 , and  224  (below, referred to as  221  to  224 ) in addition to the duct  112  in the second ejection head  42 K, and includes the duets  241 ,  242 ,  243 , and  244  (below, referred to  241  to  244 ) in place of the duct  114  as illustrated in  FIG. 6 . 
     The release unit  200  includes a pair of overhang portions  280  that are disposed on both end portions in the longitudinal direction of each second ejection head  42 Y to  42 K, and that overhang further to the lower side than the upper surface of the transported continuous paper P as illustrated in  FIGS. 5 and 6 . The pair of overhang portions  280  are, specifically, disposed on the outside in the longitudinal direction with respect to the unit heads  20 A and  20 E, adjacent to the unit heads  20 A and  20 E. 
     In the release units  200 , the second ejection heads  42 M and  42 C are configured similarly to the second ejection head  42 K, except for the feature of not including the ducts  222  and  242 . The second ejection head  42 Y is configured similarly to the second ejection head  42 K, except for the feature of not including the ducts  222 ,  224 ,  242 , and  244 . 
     The ducts  221  to  224  are disposed on the unit head  20 A side, on the upstream side in the transport direction, on the unit head  20 C side, and on the downstream side in the transport direction spaced, respectively, with a gap S 1 . The ducts  221  to  224  respectively include the release ports  321 ,  322 ,  323 , and  324  (below, referred to  321  to  324 ) facing the unit head  20 A side, the upstream side in the transport direction, the unit head  20 C, and the downstream side in the transport direction, when viewed from the nozzle  46  side of the unit head  20 . 
     The release port  322 , specifically, faces the unit head  20 B side disposed an the upstream side in the transport direction with respect to the release port  322 , viewed from the nozzle side of the unit head  20 . The wind speed of the humidified air released from the release port  322  is made a speed exceeding ½ of the transport speed of the continuous paper P. The wind speed is set to a speed exceeding ½ of the transport speed of the continuous paper P by adjusting the cross-sectional area or the like of the duct  222  in advance. 
     The release port  324  of the second ejection heads  42 K,  42 C, and  42 M, specifically, face the unit head  20 B side in the second ejection heads  42 C,  42 M, and  42 Y disposed on the downstream side in the transport direction, respectively. 
     The ducts  241  to  244  are disposed on the unit head  20 C side, on the upstream side in the transport direction, on the unit bead  20 E side, and on the downstream side in the transport direction spaced, respectively, with a gap S 3 . The ducts  241  to  244  respectively include the release ports  341 ,  342 ,  343 , and  344  (below, referred to  341  to  344 ) facing the unit head  20 C side, the upstream side in the transport direction, the unit bead  20 E side, and the downstream side in the transport direction, when viewed from the nozzle  46  side of the unit head  20 . 
     The release port  342 , specifically, faces the unit head  20 D side disposed on the upstream side in the transport direction with respect to the release port  342 , viewed from the nozzle side of the unit head  20 . The wind speed of the humidified air released from the release port  342  is made a speed exceeding ½ of the transport speed of the continuous paper P. The wind speed is set to a speed exceeding ½ of the transport speed of the continuous paper P by adjusting the cross-sectional area or the like of the duct  242  in advance. 
     The release port  344  of the second ejection heads  42 K,  42 C, and  42 M, specifically, face the unit head  20 D side in the second ejection heads  42 C,  42 M,  42 Y disposed on the downstream side in the transport direction, respectively. 
     The ducts  211  and  212  are disposed adjacent to the unit head  20 A and the unit head  20 B, respectively. The ducts  211  and  212  include the release ports  311  and  312  that, face the unit head  20 A side and the unit head  20 B side, respectively, when viewed from the nozzle  46  side of the unit head  20 . 
     The ducts  231  to  233  are disposed on the unit head  20 B side, the unit head  20 C side and the unit head  20 D side, respectively, spaced with the gap S 2 . The ducts  231  to  233  respectively include the release ports  331 ,  332 , and  333  (below, referred to  331  to  333 ) lacing the unit head  20 B side, the unit head  20 C side, and the unit head  20 D side, when viewed from the nozzle  46  side of the unit head  20 . 
     The ducts  251  and  252  are disposed adjacent to the unit head  20 E and the unit head  20 D, respectively. The ducts  251  and  252  include the release ports  351  and  352  that face the unit head  20 E side and the unit head  20 D side, respectively, when viewed from the nozzle  46  side of the unit bead  20 . 
     In this way, in the release units  200 , the respective release ports  321  to  324 ,  341  to  344 ,  311 ,  312 ,  331  to  333 ,  351 , and  352  face their respective unit head  20  side. Therefore, the humidified air is more efficiently supplied to the space below the nozzle  46  of each unit head  20  than in a configuration (comparative example) in which each release port faces in the ejecting direction (downwards) of the nozzle  46 . Accordingly, according to the release unit  200 , drying of the nozzles  46  of each unit head  20  is better suppressed compared to the comparative examples. 
     The wind speed of the humidified air released from the release ports  322  and  324  in the release unit  200  is made a speed exceeding  112  of the transport speed of the continuous paper P. Here, an air flow arises by the continuous paper P being transported in the release unit  200 , in a case where the air current is seen to be a Couette flow (flow within a gap when a gas fills a space between parallel plates placed in parallel having narrow gap therebetween and the parallel plate on one side moves in parallel at a constant speed), the average flow rate of the air current becomes approximately ½ of the transport speed of the continuous paper P. 
     Accordingly, because the wind speed of the humidified air released front the release ports  322  and  324  in the release unit  200  exceeds the average flow rate of the air current, the humidified air is more effectively supplied to the space below the nozzles  46  of the unit heads  20 B and  20 D in the second ejection head  42  that in a configuration in which the wind, speed of the humidified air released from the release port is a speed of  112  or lower of the transport speed of the continuous paper P. Accordingly, drying of the nozzles  46  of the unit beads  20 B and  20 D in the second ejection head  42  is better suppressed than in the comparative examples. 
     Since a pair of overhang portions  280  is included in the release unit  200 , it difficult for the humidified air to escape to the outside in the longitudinal direction of each of the second ejection heads  42 Y to  42 K, and drying of the nozzle  45  of each unit head  20  is suppressed. In particular, since the pair of overhang portions  280  overhang further to the lower side than the upper surface of the continuous paper P, the humidified air does not escape to the outside and drying of the nozzle  46  of each unit head  20  is more effectively suppressed when compared to a configuration only overhanging further to the upper side than the upper surface of the continuous paper P. 
     It should be noted that the pair of overhang portions  280  may be provided in the above-described release units  100  and  200 . 
     Release Unit  300  According to Third Modification Example 
     Next, the release unit  300  according to third modification example will be described. Below, the portions differing from the release unit  200  according to the second modification example will be described, and description of the same parts as the release unit  200  will not be provided, as appropriate. 
     The release unit  300  includes the ducts  360  and  362  in place of the duct  222  in the second ejection head  42 K, and includes the ducts  365  and  367  in place of the duct  242 , as illustrated in  FIG. 7 . 
     The ducts  360  and  362  are disposed on both sides in the longitudinal direction with respect to the unit head  20 B. Specifically, the duet  360  is disposed on the side opposite (left side in  FIG. 7 ) to the unit head  20 B with respect to the duct  212 . The duct  362  is disposed on the side opposite fright side in  FIG. 7 ) to the unit head  20 B with respect to the duct  231 . 
     The duct  360  includes a release port  370  facing the upstream side in the transport direction with respect to the unit head  20 B obliquely to the transport direction. That is, the release port  370  faces the upper side obliquely to the right in  FIG. 7 . 
     The duct  362  includes a release port  372  facing the upstream side in the transport direction with respect to the unit head  20 B obliquely to the transport direction. That is, the release port  372  faces the upper side obliquely to the left in  FIG. 7 . 
     The ducts  365  and  367  are disposed on both sides in the longitudinal direction with respect to the unit head  20 D. Specifically, the duct  365  is disposed on the side opposite (left side in  FIG. 7 ) to the unit head  20 D with respect to the duct  233 . The duct  367  is disposed on the side opposite (right side in  FIG. 7 ) to the unit head  20 D with respect to the duct  252 . 
     The duct  365  includes a release port  375  lacing the upstream side in the transport direction with respect to the unit head  20 D obliquely to the transport direction. That is, the release port  375  races the upper side obliquely to the right in  FIG. 7 . 
     The duct  367  includes a release port  377  facing the upstream side in the transport direction with respect to the unit head  20 D obliquely to the transport direction. That is, the release port  377  faces the upper side obliquely to the tell in  FIG. 7 . 
     In this way, the release ports  370 ,  372 ,  375 , and  377  disposed on the end portion in the longitudinal direction with respect to the unit heads  20 B,  20 D in the release unit  300  face the upstream side in the transport direction with respect to the unit head  20 B and  20 D obliquely to the transport direction. Therefore, the humidified air released from the release ports  370 ,  372 ,  375  and  377  is sent to, the upstream side in the transport direction of the unit heads  20 B and  20 D. The humidified air released send to the upstream side in the transport direction of the unit heads  20 B and  20 D is transported to the downstream side in the transport direction by the air flow arising by the Continuous paper P being transported, and is supplied to the space below the nozzles  46  of the unit heads  20 B and  20 D in the second ejection head  42 K. Accordingly, drying of the nozzle  46  of the unit heads  20 B and  20 D is better suppressed than a configuration in which the release ports  370 ,  372 ,  375 , and  377  faces the unit-heads  20 B and  20 D alone the width direction of the continuous paper P. 
     It should be noted that although the release unit  300  includes the ducts  360  and  362  in place of the duet  222  in the second ejection head  42 K, and includes the ducts  365 , and  367  in place of the duct  242 , the ducts  360 ,  362 ,  365 , and  367  may be included in addition to the duets  222  and  242 . 
     The foregoing description of the exemplary embodiments ref the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.