Patent Publication Number: US-9403388-B2

Title: Recording medium transporting device and inkjet recording device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of PCT International Application No. PCT/JP2014/054646 filed on Feb. 26, 2014, which claims priority under 35 U.S.C §119(a) to Japanese Patent Application No. 2013-044311 filed on Mar. 6, 2013. Each of the above applications is hereby expressly incorporated by reference, in their entirety, into the present application. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a recording medium transporting device and an inkjet recording device, and particularly to a multistage drum type (tandem type) recording medium transporting device and inkjet recording device. 
     2. Description of the Related Art 
     In an inkjet printing device, a distance between an inkjet head and a surface to be printed (through distance) is set to be small as much as possible in order to stably maintain a jetted ink landing position. In general, the distance between the inkjet head and the surface to be printed is often set to be about several millimeters or less, or 1 mm or less if possible. 
     On the other hand, in a printing machine, a multistage drum type (tandem type) sheet-of-paper transporting technology has been established in which a sheet of paper is transported with a leading end thereof being held by a grasping claw and passed from a drum to a drum. In the sheet-of-paper transporting technology used for the printing machine, a surface of the grasping claw supporting the paper sheet is configured to be protruded from a surface of the drum. 
     In order to achieve inkjet printing by use of this sheet-of-paper transporting device, a protruding amount of the grasping claw of a drum having the inkjet head mounted thereon (hereinafter, referred to as a printing drum) needs to be small. 
     Japanese Patent Application Laid-Open No. 2011-173279 (PTL 1), dealing with such a problem, describes a technology in which a grasping claw is arranged to be housed in a recessed part so as not to be protruded from a peripheral surface of the printing drum. 
     SUMMARY OF THE INVENTION 
     The multistage drum type sheet-of-paper transporting device has a configuration in which, in passing the paper sheet from an upstream drum to a downstream drum, the leading end portions of the paper sheet are simultaneously held by a grasping unit of the upstream drum and a grasping unit of the downstream drum. In the PTL 1, a grasping unit of a drum of a stage prior to the printing drum is arranged on an outer peripheral surface, and a grasping unit of the printing drum is arranged on an inner side on the drum. Therefore, in passing the paper sheet between these two drums, the paper sheet may be sometimes passed with the leading end portion thereof being in a wavy state caused by the grasping unit s of both drums. This may leave deformation or creases on the paper sheet. 
     The present invention has been made in consideration of such a circumstance, and has an object to provide a recording medium transporting device and inkjet recording device capable of suppressing distortion of a recording medium caused by a grasping unit and stably transporting the recording medium. 
     In order to achieve the above object, an aspect of a recording medium transporting device includes a printing barrel that rotates and transports with gripping an end portion of a recording medium inwardly from an outer peripheral surface thereof, an inkjet head for ejecting and depositing ink onto the recording medium being arranged on the outer peripheral surface so as to face the printing barrel, and a first transporting barrel that rotates and transports with gripping the end portion of the recording medium on an outer peripheral surface thereof for passing to the printing barrel and a second transporting barrel that rotates and transports with gripping the end portion of the recording medium on an outer peripheral surface thereof for passing to the first transporting barrel, or a first transporting barrel that rotates and transports with gripping the end portion of the recording medium received from the printing barrel and a second transporting barrel that rotates and transports with gripping the end portion of the recording medium received from the first transporting barrel on an outer peripheral surface thereof, wherein an inter-shaft distance between the printing barrel and the first transporting barrel is set to be a distance shorter than a sum of a radius of the printing barrel and a radius of the first transporting barrel, and an inter-shaft distance between the first transporting barrel and the second transporting barrel is set to be a sum of the radius of the first transporting barrel and a radius of the second transporting barrel. 
     According to this aspect, the inter-shaft distance between the printing barrel that rotates and transports with gripping the end portion of the recording medium inwardly from the outer peripheral surface thereof and the first transporting barrel juncturally connected with the printing barrel is set to be the distance shorter than the sum of the radius of the printing barrel and the radius of the first transporting barrel, and the inter-shaft distance between the first transporting barrel and the second transporting barrel juncturally connected with the first transporting barrel is set to be the sum of the radius of the first transporting barrel and the radius of the second transporting barrel, which can suppress distortion of the recording medium, and enables the first transporting barrel and the second transporting barrel to grip the end portion of the recording medium on the outer peripheral surface thereof, allowing stable transportation. 
     It is preferable that the printing barrel grips the end portion of the recording medium inwardly by a distance d from the outer peripheral surface, and the inter-shaft distance between the printing barrel and the first transporting barrel is set to be a distance shorter by a distance d than the sum of the radius of the printing barrel and the radius of the first transporting barrel. This allows the distortion of the recording medium to be suppressed. 
     It is preferable that each of the printing barrel, the first transporting barrel, and the second transporting barrel has a gear coupled to a rotation shaft thereof, and the gear of the printing barrel and the gear of the first transporting barrel directly engage with each other, and the gears of the first transporting barrel and the second transporting barrel directly engage with each other, and the inter-shaft distance is set by shifting the gear of the printing barrel. This allows the inter-shaft distance to be appropriately set. 
     It is preferable to include a motor for driving the gear of the printing barrel, the gear of the first transporting barrel and the gear of the second transporting barrel. This allows the recording medium to be appropriately transported. 
     It is preferable that diameters of the printing barrel, the first transporting barrel, and the second transporting barrel have an integral multiple relationship with each other. In addition, the respective barrels may have the same diameter. This allows the recording medium to be appropriately passed. 
     It is preferable that the printing barrel and the first transporting barrel have plural grasping units for gripping by grasping the end portion of the recording medium along rotation shaft directions respectively, and the plural grasping units of the printing barrel and the plural grasping units of the first transporting barrel are alternately arranged along the rotation shaft directions respectively. This allows the recording medium to be appropriately gripped. 
     It is preferable that when the recording medium is passed from the first transporting barrel to the printing barrel or from the printing barrel to the first transporting barrel, the plural grasping units of the first transporting barrel and the plural grasping units of the printing barrel simultaneously grasp the end portion of the recording medium. This allows the recording medium to be appropriately passed. In addition, the plural grasping units of the printing barrel may be arranged on the outer peripheral surface at two locations that are symmetric positions about the rotation shaft of the printing barrel. 
     It is preferable that the end portion of the recording medium is a leading end portion. This allows the recording medium to be appropriately gripped to be transported. 
     In order to achieve the above object, an aspect of an inkjet recording device includes recording medium transporting device including a printing barrel that rotates and transports with gripping an end portion of a recording medium inwardly from an outer peripheral surface thereof, an inkjet head for ejecting and depositing ink onto the recording medium being arranged on the outer peripheral surface so as to face the printing barrel, and a first transporting barrel that rotates and transports with gripping the end portion of the recording medium on an outer peripheral surface thereof for passing to the printing barrel and a second transporting barrel that rotates and transports with gripping the end portion of the recording medium on an outer peripheral surface thereof for passing to the first transporting barrel, or a first transporting barrel that rotates and transports with gripping the end portion of the recording medium received from the printing barrel on the outer peripheral surface thereof and a second transporting barrel that rotates and transports with gripping the end portion of the recording medium received from the first transporting barrel on an outer peripheral surface thereof, wherein an inter-shaft distance between the printing barrel and the first transporting barrel is set to be a distance shorter than a sum of a radius of the printing barrel and a radius of the first transporting barrel, and an inter-shaft distance between the first transporting barrel and the second transporting barrel is set to be a sum of the radius of the first transporting barrel and a radius of second transporting barrel, and an inkjet head arranged so as to face the outer peripheral surface of the printing barrel. 
     According to this aspect, high-definition inkjet printing by the inkjet head arranged facing the printing barrel is enabled. Moreover, distortion of the recording medium can be suppressed to be small and a degree of contact of the paper sheet with the printing barrel can be increased, which enables the high-definition inkjet printing. Further, the inter-shaft distance between the printing barrel and the first transporting barrel is set to be a distance shorter than a sum of the radius of the printing barrel and the radius of the first transporting barrel, which enables the first transporting barrel and the second transporting barrel to grip the end portion of the recording medium on the outer peripheral surface thereof, allowing the stable transportation. 
     According to the present invention, the distortion of the recording medium can be suppressed, and the recording medium can be stably transported. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a lateral view illustrating a paper sheet transporting device. 
         FIG. 2  is a configuration diagram of a rotary drive mechanism of the paper sheet transporting device. 
         FIG. 3  is a perspective view of a transporting barrel. 
         FIG. 4  is an overview illustration of the transporting barrel. 
         FIGS. 5A and 5B  are schematic views of the transporting barrel and a gripper. 
         FIGS. 6A and 6B  are schematic views of the transporting barrel and the gripper. 
         FIG. 7  is a diagram illustrating transportation of a paper sheet in the paper sheet transporting device. 
         FIGS. 8A and 8B  are diagrams explaining waving of the paper sheet. 
         FIGS. 9A and 9B  are schematic views of the transporting barrel and the gripper. 
         FIG. 10  is a diagram illustrating transportation of the paper sheet in the paper sheet transporting device. 
         FIGS. 11A and 11B  are diagrams explaining passing of the paper sheet. 
         FIG. 12  is a lateral view illustrating the paper sheet transporting device according to the embodiment. 
         FIG. 13  is a configuration diagram of the rotary drive mechanism of the paper sheet transporting device according to the embodiment. 
         FIG. 14  is a diagram illustrating transportation of the paper sheet by the paper sheet transporting device according to the embodiment. 
         FIGS. 15A and 15  B are diagrams explaining passing of the paper sheet according to the embodiment. 
         FIG. 16  a lateral view illustrating a modification example of the paper sheet transporting device according to the embodiment. 
         FIG. 17  is a general configuration diagram illustrating an embodiment of an inkjet recording device according to the embodiment. 
         FIG. 18  is a configuration diagram of a rotary drive mechanism of the inkjet recording device according to the embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereinafter, a description is given of preferred embodiments of the present invention with reference to the drawings. 
     &lt;Outline of Paper Sheet Transporting Device&gt; 
       FIG. 1  is a lateral view illustrating a paper sheet transporting device. A paper sheet transporting device  200 , which is a device for transporting a paper sheet P fed from a paper feed unit (not illustrated) to a paper discharge unit (not illustrated), includes transporting barrels  202 ,  204 ,  206 ,  208 , and  210  each of which rotates with gripping a leading end of the paper sheet P passed from an upstream side and transports the paper sheet P in a state of being held on an outer peripheral surface to pass to a downstream side. 
     The transporting barrel  202  receives the paper sheet P from the paper feed unit (not illustrated) and transports the paper sheet P to the transporting barrel  204 . The transporting barrel  202  includes a frame member assembled in a cylindrical shape and has a gripper  202 A on the outer peripheral surface thereof. The transporting barrel  202  rotates with gripping by the gripper  202 A the leading end of the paper sheet P to transport the paper sheet P to the transporting barrel  204 . Note that the transporting barrel  202  has the gripper  202 A arranged on the outer peripheral surface thereof at each of two locations (symmetric positions about a rotation shaft) to be configured such that two paper sheets P can be transported per one rotation. The transporting barrel  202  and the transporting barrel  204  are driven such that their timings of receiving and passing the paper sheet P coincide with each other and such that positions of their grippers match each other. 
     The transporting barrel  204  receives the paper sheet P from the transporting barrel  202  to transport the paper sheet P to the transporting barrel  206 . The transporting barrel  204  is formed into a cylindrical shape and has a gripper  204 A on the outer peripheral surface thereof. The transporting barrel  204  rotates with gripping by the gripper  204 A the leading end of the paper sheet P to wind the paper sheet P on the peripheral surface while transporting the paper sheet P to the transporting barrel  206 . The transporting barrel  204  has a plenty of sucking holes (not illustrated) formed on the peripheral surface thereof in a predetermined pattern. The paper sheet P wound on the peripheral surface of the transporting barrel  204  is sucked from the sucking holes to be held by suction on the peripheral surface of the transporting barrel  204  while being transported. This allows the paper sheet P to be transported with flatness being highly kept. 
     The transporting barrel  206  is configured similar to the transporting barrel  202 . The transporting barrel  206  includes a frame member assembled in a cylindrical shape and has a gripper  206 A on the outer peripheral surface thereof. The transporting barrel  206  grips by the gripper  206 A the leading end of the paper sheet P received from the transporting barrel  204  and rotates to transport the paper sheet P to the transporting barrel  208 . 
     The transporting barrel  208  is configured similar to the transporting barrel  204 . In other words, the transporting barrel  208  is formed into a cylindrical shape and has a gripper  208 A on the outer peripheral surface thereof. The transporting barrel  208  grips by the gripper  208 A the leading end of the paper sheet P received from the transporting barrel  206  and rotates to transport the paper sheet P to the transporting barrel  210 . 
     The transporting barrel  210  is also configured similar to the transporting barrel  202 . The transporting barrels  202 ,  204 ,  206 ,  208 , and  210  are each configured to have the same diameter (diameter of a rotation trajectory of the gripper). 
       FIG. 2  is a configuration diagram of a rotary drive mechanism provided on a lateral side opposite to that illustrated in  FIG. 1 . As illustrated in the figure, the paper sheet transporting device  200  has a motor  212  (hereinafter, referred to as “motor for rotation”) provided as a motive power source for a paper sheet transporting system. Motive power from the motor  212  for rotation is transmitted via a timing belt (toothed belt having no ends)  214  to a pulley  216 . 
     The pulley  216  is integrally coupled in a concentric manner with a toothed wheel  218 , and thus, the pulley  216  and the toothed wheel  218  rotate together. The toothed wheel  218  engages with a toothed wheel  220  which is provided at the upper left of the toothed wheel  218  in  FIG. 2 , and the toothed wheel  220  engages with a toothed wheel (gear)  222  directly coupled to an end portion of the transporting barrel  202 . 
     The toothed wheel  222  of the transporting barrel  202  engages with a toothed wheel  224  provided at an end portion of the transporting barrel  204 , and the toothed wheel  224  engages with a toothed wheel  226  provided at an end portion of the transporting barrel  206 . Subsequently, the toothed wheel  226  engages with a toothed wheel  228  of the transporting barrel  208 , and the toothed wheel  228  engages with a toothed wheel  230  of the transporting barrel  210 . 
     The respective toothed wheels  222  to  230 , each of which is a toothed wheel for rotation of the transporting barrel and between which inter-shaft distances are identical, are configured to be interlocked with one another. The motive power from the motor  212  for rotation is transmitted via the timing belt  214 , the pulley  216 , and the toothed wheels  218  and  220  to the respective toothed wheels  222  to  230 , and these toothed wheels  222  to  230  work in conjunction with one another to rotate all of the transporting barrels  202 ,  204 ,  206 ,  208 , and  210 . In the case of this example, a diameter of each of the transporting barrels  202 ,  204 ,  206 ,  208 , and  210  matches a diameter of each of the toothed wheels  222  to  230  (pitch circle diameter), and thus, when the toothed wheel  222  rotates one revolution, the transporting barrels  204 ,  206 ,  208 , and  210  also rotate one revolution. 
       FIG. 3  and  FIG. 4  are each an enlarged view illustrating the transporting barrel  206  and the transporting barrel  208 , and  FIG. 3  is a perspective view and  FIG. 4  is an overview illustration. As illustrated in  FIG. 3  and  FIG. 4 , the gripper  206 A of the transporting barrel  206  has a claw like shape, and is provided in plural number across a length corresponding to a maximum width of the paper sheet P at certain intervals in a rotation shaft direction of the transporting barrel  206  (a direction perpendicular to a transporting direction of the paper sheet P). Similarly, the gripper  208 A of the transporting barrel  208  has a claw like shape, and is provided in plural number across the length corresponding to the maximum width of the paper sheet P at certain intervals in a rotation shaft direction of the transporting barrel  208 . 
     These plural grippers  206 A and plural grippers  208 A are arranged alternately in a direction perpendicular to the transporting direction of the paper sheet P. This allows the paper sheet P to be received and passed between the grippers  206 A and  208 A without interference therebetween. 
     Here, the transporting barrel  206  and the transporting barrel  208  are described, but the grippers of other transporting barrels are similarly arranged. 
     In  FIG. 5A , a schematic view is illustrated of the transporting barrel  208  and the gripper  208 A, and in  FIG. 5B , an enlarged view is illustrated of a portion of the gripper  208 A. As illustrated in the figures, the leading end of the paper sheet P is pinched between the gripper  208 A and the outer peripheral surface of the transporting barrel  208 . Therefore, a surface of the gripper  208 A is protruded from the outer peripheral surface of the transporting barrel  208  by a thickness h of a pinching portion. The gripper  204 A is configured to be similar to the gripper  208 A. Further, the grippers  202 A,  206 A, and  210 A are oriented inversely to an orientation of the gripper  208 A because rotational directions of the transporting barrels  202 ,  206 , and  210  are different from that of the transporting barrel  208 , but other configurations thereof are similar to those of the gripper  208 A. Therefore, each of the grippers  202 A,  204 A,  206 A, and  210 A has a configuration similar to the gripper  208 A in which a surface thereof is protruded from the outer peripheral surface of each of the transporting barrels  202 ,  204 ,  206 , and  210 , respectively. 
     However, in a case where an ink is deposited from an inkjet head on the paper sheet P being transported by the transporting barrel  208  for recording an image, a distance TD (Through Distance) between a record surface of the paper sheet P and a nozzle face of the inkjet head is controversial. In other words, the TD is required to be set to be small as much as possible in order to stabilize an ink landing position, but the inkjet head and the gripper may problematically collide against each other. 
     &lt;Problem Point 1 of Paper Sheet Transporting Device (Generation of Waving of Paper Sheet)&gt; 
     As a measure for this problem, a configuration is required in which the leading end portion of the paper sheet P is sunk down inwardly from the outer peripheral surface of the transporting barrel  208 . In of  FIG. 6A , a schematic view is illustrated of a transporting barrel  238  and a gripper  238 A configured in this way, and in  FIG. 6B , an enlarged view is illustrated of a portion of the gripper  238 A. Reference sign  238 B designates the inkjet head in the figure. The transporting barrel  238  has a configuration in which the leading end portion of the paper sheet P is sunk down inwardly by d from the outer peripheral surface, and the leading end of the paper sheet P is pinched between the gripper  238 A and transporting barrel  238  at a position sunk down inwardly like this. Therefore, a protruding amount of the gripper  238 A from the outer peripheral surface of the transporting barrel  238  is smaller by d than that of the example illustrated in  FIG. 5 . This allows the distance TD between the record surface of the paper sheet P and the inkjet head  238 B to be set to be small. 
       FIG. 7  is a diagram illustrating transportation of the paper sheet P in a paper sheet transporting device  240  using the transporting barrel  238 . The paper sheet transporting device  240  includes the transporting barrels  202 ,  204 ,  206 ,  238 , and  210 , and the transporting barrel  238  illustrated in  FIG. 6  is used in place of the transporting barrel  208  of the paper sheet transporting device  200  illustrated in  FIG. 1 . Reference sign  238 B designates the inkjet head in the figure. 
     In  FIG. 7 , a solid line represents of a trajectory of the leading end portion of the paper sheet P, and a chain line represents a drive pitch circle of the toothed wheel of each transporting barrel. Similarly to paper sheet transporting device  200 , the inter-shaft distances are all set to be identical between the toothed wheels. 
     The trajectory of the leading end portion of the paper sheet P is continuous from the transporting barrel  202  to the transporting barrel  204  and from the transporting barrel  204  to the transporting barrel  206 . Therefore, the passing of the paper sheet P via the grippers is carried out with no paper sheet deformation being generated. 
     In contrast, from the transporting barrel  206  to the transporting barrel  238 , the gripper  206 A of the transporting barrel  206  grips the paper sheet P on the outer peripheral surface of the transporting barrel  206 , whereas the gripper  238 A of the transporting barrel  238  grips the paper sheet P on an inner side of the outer peripheral surface of the transporting barrel  238 , which causes the trajectory of the leading end portion of the paper sheet P to be discontinuous. 
     Similarly, also in passing from the transporting barrel  238  to the transporting barrel  210 , the trajectory of the leading end portion of the paper sheet P is discontinuous. 
     Specifically, as illustrated in  FIG. 8A , at a position where the paper sheet P is passed from the transporting barrel  206  to the transporting barrel  238 , a row of the plural grippers  206 A and a row of the plural grippers  238 A are apart from each other by the distance d, and do not align on the same line. Therefore, if the respective grippers grasp the leading end of the paper sheet P, waving is generated at the leading end portion of the paper sheet P as illustrated in  FIG. 8B . In passing the paper sheet P from the transporting barrel  238  to the transporting barrel  210  also, waving is generated similarly. This waving is notably generated particularly when a thickness of the paper sheet P is large. 
     &lt;Problem Point 2 of Paper Sheet Transporting Device (Positional Accuracy Degradation of Paper Sheet Transporting)&gt; 
     In order to prevent this waving of the paper sheet P, it may be considered that a transporting barrel, in place of the transporting barrel  206 , is used in which the leading end portion of the paper sheet P is griped on an outer side by d from the outer peripheral surface. In  FIG. 9A , a schematic view is illustrated of a transporting barrel  252  and a gripper  252 A configured in this way and in  FIG. 9B , an enlarged view is illustrated of a portion of the gripper  252 A. The transporting barrel  252  has a configuration in which the leading end portion of the paper sheet P is protruded outwardly by d from the outer peripheral surface, and the leading end of the paper sheet P is pinched between the gripper  252 A and the transporting barrel  252  at a position protruded outwardly like this. 
       FIG. 10  is a diagram illustrating transportation of the paper sheet P in a paper sheet transporting device  260  using the transporting barrel  238  and the transporting barrel  252 . The paper sheet transporting device  260  includes transporting barrels  262 ,  264 ,  266 ,  268 , and  270  each having the same diameter, and the transporting barrel  238  illustrated in  FIG. 6  is applied to the transporting barrels  264  and  268  and the transporting barrel  252  illustrated in  FIG. 9  is applied to the transporting barrels  262 ,  266 , and  270 . Here, grippers of the transporting barrels  262 ,  264 ,  266 ,  268 , and  270  are designated by reference signs  262 A,  264 A,  266 A,  268 A, and  270 A, respectively. 
     A rotary drive mechanism of the paper sheet transporting device  260  is similar to that of the paper sheet transporting device  200  illustrated in  FIG. 2 , and the inter-shaft distances are all set to be identical between the toothed wheels. Reference sign  268 B designates the inkjet head in the figure. 
     In  FIG. 10 , a solid line represents a trajectory of the leading end portion of the paper sheet P, and a chain line represents a drive pitch circle of toothed wheel of each transporting barrel. As illustrated in the figure, the trajectory of the leading end portion of the paper sheet P is continuous in the respective transporting barrels  262  to  270 , and the passing of the paper sheet P via the grippers is carried out with no paper sheet deformation being generated. 
     Specifically, as illustrated in  FIG. 11A , in passing the paper sheet P from the transporting barrel  266  to the transporting barrel  268 , the passing of the paper sheet P is carried out at a position being protruded outwardly by the distance d from the outer peripheral surface of the transporting barrel  266  and being sunk down inwardly by the distance d from the outer peripheral surface of the transporting barrel  268 . The passing from the transporting barrel  262  to the transporting barrel  264  is also similarly carried out. 
     In passing the paper sheet P from the transporting barrel  268  to the transporting barrel  270 , the passing of the paper sheet P is carried out at a position being sunk down inwardly by the distance d from the outer peripheral surface of the transporting barrel  268  and being protruded outwardly by the distance d from the outer peripheral surface of the transporting barrel  270 . The passing from the transporting barrel  264  to the transporting barrel  266  is also similarly carried out. 
     The passing of the paper sheet P is carried out in this way, which allows the leading end portion of the paper sheet P to be continuous. 
     However, the paper sheet transporting device  260  configured in this way is required to achieve simultaneously two functions of positioning and leading end deformation in passing the paper sheet P from the paper feed unit (not illustrated) to the transporting barrel  262 . Specifically, as illustrated in  FIG. 11B , since the gripper  262 A of the transporting barrel  262  is protruded outwardly by the distance d from the outer peripheral surface of the transporting barrel  262 , it is required that the leading end of the paper sheet P is accurately positioned at a position of the gripper  262 A as well as the leading end of the paper sheet P is formed into a bent shape in order to make the protruded gripper  262 A grip the leading end. Therefore, repeatability of positional accuracy of the paper sheet transportation may be problematically degraded. 
     &lt;Embodiment&gt; 
     [Outline of Paper Sheet Transporting Device] 
       FIG. 12  is a lateral view illustrating a paper sheet transporting device according to the embodiment. A paper sheet transporting device  100  (an example of the recording medium transporting device), which is a device for transporting a paper sheet P (an example of the recording medium) fed from a paper feed unit (not illustrated) to a paper discharge unit (not illustrated), includes transfer barrels  102 ,  106  (examples of a first transporting barrel) and,  110  (an example of a first transporting barrel), a treatment barrel  104  (an example of a second transporting barrel), and a printing barrel  108 . 
     The transfer barrel  102  receives the paper sheet P from the paper feed unit (not illustrated) and transports the paper sheet P to the treatment barrel  104 . The transfer barrel  102  includes a frame member assembled in a cylindrical shape having a radius r and has a gripper  102 A on the outer peripheral surface thereof (on a trajectory plane tracked by the radius r) (see  FIG. 5 ). The transfer barrel  102  rotates with gripping by the gripper  102 A the leading end of the paper sheet P on the outer peripheral surface thereof to transport the paper sheet P to the treatment barrel  104 . 
     The treatment barrel  104  receives the paper sheet P from the transfer barrel  102  and transports the paper sheet P to the transfer barrel  106 . The treatment barrel  104  is formed into a cylindrical shape having the radius r and has a gripper  104 A on the outer peripheral surface thereto (see  FIG. 5 ). The treatment barrel  104  rotates with gripping by the gripper  104 A the leading end of the paper sheet P on the outer peripheral surface thereof to wind the paper sheet P on the peripheral surface while transporting the paper sheet P to the transfer barrel  106 . 
     The treatment barrel  104  has a plenty of sucking holes (not illustrated) formed on the peripheral surface thereof in a predetermined pattern. The paper sheet P wound on the peripheral surface of the treatment barrel  104  is sucked from the sucking holes to be held by suction on the peripheral surface of the treatment barrel  104  while being transported. This allows the paper sheet P to be transported with flatness being highly kept. 
     Provided at a position facing a transporting path of the paper sheet P for the treatment barrel  104  is a treatment unit (not illustrated) for subjecting the paper sheet P to various treatments. For example, there is provided a treatment liquid application device for applying the treatment liquid onto the surface to be printed of the paper sheet P or the like. As described above, the treatment barrel  104  transports the paper sheet P with flatness being highly kept, which makes it possible to subject the paper sheet P to a desired treatment. 
     The transfer barrel  106 , similarly to the transfer barrel  102 , includes a frame member assembled in a cylindrical shape having the radius r and has a gripper  106 A (an example of a grasping unit) on the outer peripheral surface thereof (see  FIG. 5 ). The transfer barrel  106  grips by the gripper  106 A the leading end of the paper sheet P received from the treatment barrel  104  to be held on the outer peripheral surface thereof and rotates to transport the paper sheet P to the printing barrel  108 . 
     The printing barrel  108  receives the paper sheet P from the transfer barrel  106  and transports the paper sheet P to the transfer barrel  110 . The printing barrel  108  is formed into a cylindrical shape having the radius r, and configured to have a concave so as to sink down the leading end portion of the paper sheet P inwardly by d from the outer peripheral surface and have a gripper  108 A (an example of the grasping unit) arranged at a position sunk down inwardly like this (see  FIG. 6 ). The printing barrel  108  rotates with gripping by the gripper  108 A the leading end of the paper sheet P on the outer peripheral surface thereof to wind the paper sheet P on the peripheral surface while transporting the paper sheet P to the transfer barrel  110 . 
     The printing barrel  108  has a plenty of sucking holes (not illustrated) formed on the peripheral surface thereof in a predetermined pattern. The paper sheet P wound on the peripheral surface of the printing barrel  108  is sucked from the sucking holes to be held by suction on the peripheral surface of the printing barrel  108  while being transported. This allows the paper sheet P to be transported with flatness being highly kept. 
     Arranged at a position facing the transporting path of the paper sheet P for printing barrel  108  is an inkjet head  108 B for depositing the ink to form an image onto the record surface of the paper sheet P. The printing barrel  108  has the gripper  108 A arranged at a position sunk down inwardly, which makes it possible to set the distance TD between the record surface of the paper sheet P and the inkjet head  108 B to be small. Since the printing barrel  108  transports the paper sheet P with flatness being highly kept, a high quality image can be formed. 
     The transfer barrel  110 , similarly to the transfer barrel  102 , includes a frame member assembled in a cylindrical shape having the radius r and has a gripper  110 A (an example of the grasping unit) on the outer peripheral surface thereof (see  FIG. 5 ). The transfer barrel  110  grips by the gripper  110 A the leading end of the paper sheet P received from the printing barrel  108  on the outer peripheral surface thereof and rotates to transport the paper sheet P to the paper discharge unit (not illustrated). 
     The grippers  102 A,  104 A,  106 A,  108 A, and  110 A, each gripper provided in plural number, of the transfer barrel  102 , treatment barrel  104 , the transfer barrel  106 , the printing barrel  108 , and the transfer barrel  110 , respectively, are provided across the length corresponding to the maximum width of the paper sheet P at certain intervals in a direction perpendicular to the transporting direction of the paper sheet P (see  FIG. 3  and  FIG. 4 ). Each barrel has rows of the grippers each of which row is arranged on the outer peripheral surface of the barrel at two locations symmetric about the rotation shaft, and is configured such that two paper sheets P can be transported per one rotation. 
     The plural grippers of each barrel and the plural grippers passing the paper sheet P to the relevant barrel are arranged alternately in a direction perpendicular to the transporting direction of the paper sheet P (see  FIG. 3  and  FIG. 4 ). These two barrels are driven such that their timings of receiving and passing the paper sheet P coincide with each other and such that positions of their gripper rows match each other. In passing the paper sheet P, the grippers of two barrels are both (simultaneously) brought into a state of grasping the leading end portion of the paper sheet P. 
     The inter-shaft distance between the transfer barrel  102  and the treatment barrel  104 , and the inter-shaft distance between the treatment barrel  104  and the transfer barrel  106  are set to be 2×r (corresponding to a sum of a radius of the transfer barrel  102  and a radius of the treatment barrel  104 , and a sum of a radius of the treatment barrel  104  and a radius of the transfer barrel  106 , respectively), as well as the inter-shaft distance between the transfer barrel  106  and the printing barrel  108 , and the inter-shaft distance between the printing barrel  108  and the transfer barrel  110  are set to be 2×r−d (corresponding to a distance shorter by the distance d than a sum of a radius of the transfer barrel  106  and a radius of the printing barrel  108 , and a distance shorter by the distance d than a sum of a radius of the printing barrel  108  and a radius of the transfer barrel  110 , respectively). 
     [Outline of Rotary Drive Mechanism] 
       FIG. 13  is a configuration diagram of a rotary drive mechanism provided on a lateral side portion opposite to that illustrated in  FIG. 12 . As illustrated in the figure, the paper sheet transporting device  100  has a motor  112  for rotation provided as a motive power source for the paper sheet transporting system. Motive power from the motor  112  for rotation is transmitted via a timing belt  114  to a pulley  116 . 
     The pulley  116  is integrally coupled in a concentric manner with a toothed wheel  118 , and thus, the pulley  116  and the toothed wheel  118  rotate together. The toothed wheel  118  engages with a toothed wheel  120  which is provided at the upper left of the toothed wheel  118  in  FIG. 13 , and the toothed wheel  120  engages with a toothed wheel  122  directly coupled in a concentric manner with a rotation shaft of the transfer barrel  102 . 
     The toothed wheel  122  of the transfer barrel  102  engages with a toothed wheel  124  which is directly coupled in a concentric manner with a rotation shaft of the treatment barrel  104 , and the toothed wheel  124  engages with a toothed wheel  126  which is directly coupled in a concentric manner with a rotation shaft of the transfer barrel  106 . Subsequently, the toothed wheel  126  engages with a toothed wheel  128  which is directly coupled in a concentric manner with a rotation shaft of the printing barrel  108 , and the toothed wheel  128  engages with a toothed wheel  130  which is directly coupled in a concentric manner with a rotation shaft of the transfer barrel  110 . 
     The respective toothed wheels  122  to  130 , each of which is a toothed wheel for rotation of the each barrel, are configured to be interlocked (directly engaged) with one another. The motive power from the motor  112  for rotation is transmitted via the timing belt  114 , the pulley  116 , and the toothed wheels  118  and  120  to the respective toothed wheels  122  to  130 , and these toothed wheels  122  to  130  work in conjunction with one another to rotate the transfer barrel  102 , the treatment barrel  104 , the transfer barrel  106 , the printing barrel  108 , and the transfer barrel  110 . 
     The respective toothed wheels  122  to  130  are each configured to have the radius r. The inter-shaft distance between the transfer barrel  102  and the treatment barrel  104 , and the inter-shaft distance between the treatment barrel  104  and the transfer barrel  106  are set to be 2×r. Further, the inter-shaft distance between the transfer barrel  106  and the printing barrel  108 , and the inter-shaft distance between the printing barrel  108  and the transfer barrel  110  are set to be 2×r−d with a drive ratio being maintained by shifting the toothed wheel  128 . 
     In this way, a diameter of each of the transfer barrel  102 , the treatment barrel  104 , the transfer barrel  106 , the printing barrel  108 , and the transfer barrel  110  matches a diameter of each of the toothed wheels  122  to  130  (pitch circle diameter), and thus, when the transfer barrel  102  rotates one revolution, the treatment barrel  104 , the transfer barrel  106 , the printing barrel  108 , the transfer barrel  110  also rotate one revolution. 
     Note that a helical toothed wheel is used as a toothed wheel of a motive power transmission member for rotating the transfer barrel  102 , the treatment barrel  104 , the transfer barrel  106 , the printing barrel  108 , and the transfer barrel  110 . A spur toothed wheel can be used as a toothed wheel, but it is preferable to employ a helical toothed wheel and a double helical toothed wheel in order to carry out smooth motive power transmission. The helical toothed wheel, which has a teeth portion formed to be oblique, can achieve the smooth motive power transmission. The double helical toothed wheel has an advantage in that a force in a thrust direction can be reduced as compared with the helical toothed wheel, but requires higher costs than the helical toothed wheel. Therefore, in this example, the helical toothed wheel is employed in view of satisfying both the smooth motive power transmission and lower costs. 
     [Trajectory of Leading End Portion of Paper Sheet] 
       FIG. 14  is a diagram illustrating transportation of the paper sheet P in the paper sheet transporting device  100 . In the figure, a solid line represents a trajectory of the leading end portion of the paper sheet P, and a chain line represents a drive pitch circle of the toothed wheel of each barrel. 
     From the transfer barrel  102  to the treatment barrel  104 , the leading end of the paper sheet P is passed from the outer peripheral surface of the transfer barrel  102  to the outer peripheral surface of the treatment barrel  104  by way of a row of the plural grippers  102 A and a row of the plural grippers  104 A, the rows aligning on the same line. Therefore, the trajectory of the leading end portion of the paper sheet P is continuous, and the passing of the paper sheet P is carried out with no paper sheet deformation (waving) being generated. 
     Similarly, from the treatment barrel  104  to the transfer barrel  106  also, the leading end of the paper sheet P is passed from the outer peripheral surface of the treatment barrel  104  to the outer peripheral surface of the transfer barrel  106  by way of a row of the plural grippers  104 A and a row of the plural grippers  106 A, the rows aligning on the same line. Therefore, the trajectory of the leading end portion of the paper sheet P is continuous, and the passing of the paper sheet P is carried out with no paper sheet deformation being generated. 
     From the transfer barrel  106  to the printing barrel  108 , the leading end of the paper sheet P is passed from the outer peripheral surface of the transfer barrel  106  to an inner side that is inward by d from the outer peripheral surface of the printing barrel  108  by way of the grippers  106 A and the grippers  108 A. 
     Here, since the inter-shaft distance between the transfer barrel  106  and the printing barrel  108  is set to be 2×r−d, a row of the plural grippers  106 A and a row of the plural grippers  108 A align on the same line at a position that is inward by d from the outer peripheral surface of the printing barrel  108  as illustrated in  FIG. 15A , and thus, the trajectory of the leading end portion of the paper sheet P is continuous and the passing of the paper sheet P is carried out with no paper sheet deformation being generated. 
     Further, from the printing barrel  108  to the transfer barrel  110  also, the leading end of the paper sheet P is passed from the inner side that is inward by d from the outer peripheral surface of printing barrel  108  to the outer peripheral surface of the transfer barrel  110  by way of the grippers  108 A and the grippers  110 A. 
     Here, since the inter-shaft distance between the printing barrel  108  and the transfer barrel  110  is set to be 2×r−d, a row of the plural grippers  108 A and a row of the plural grippers  110 A align on the same line at a position that is inward by d from the outer peripheral surface of the printing barrel  108  as illustrated in  FIG. 15A , and thus, the trajectory of the leading end portion of the paper sheet P is continuous and the passing of the paper sheet P is carried out with no paper sheet deformation being generated. 
     Since the paper sheet P is pinched between the gripper  102 A of the transfer barrel  102  and the outer peripheral surface of the transfer barrel  102 , the paper sheet leading end is not required to be deformed, and thus, the passing may be carried out by way of positioning in passing the paper sheet P from the paper feed unit (not illustrated) to the transfer barrel  102  as illustrated in  FIG. 15B . 
     In this way, according to the paper sheet transporting device  100 , the arrangement of the grippers of the printing barrel sunk down inwardly from the outer peripheral surface of the printing barrel enables high-definition inkjet printing by the inkjet head arranged facing the printing barrel. Moreover, paper sheet distortion can be suppressed to be small and a degree of contact of the paper sheet with the barrel can be increased, which enables the high-definition inkjet printing. Further, the inter-shaft distances between the printing barrel and the barrels at stages prior to and subsequent to the printing barrel are set to be shorter by an amount involved by arranging inwardly the grippers of the printing barrel with the drive ratio being maintained by shifting the toothed wheel of the printing barrel, and other inter-shaft distances between the transporting barrels than those described above are set to be a sum of the radiuses of these transporting barrels, which makes it possible to arrange the grippers of the barrels other than the printing barrel on the outer peripheral surfaces of the respective barrels, allowing the stable transportation. 
     Here, the paper sheet P is passed from the transfer barrel  110  to the paper discharge unit (not illustrated), but in a case where a transfer barrel  111  gripping the paper sheet P on the outer peripheral surface (an example of the second transporting barrel) is arranged at a stage subsequent to the transfer barrel  110  as in a modification example illustrated in  FIG. 16 , the inter-shaft distance between the transfer barrel  111  and the transfer barrel  110  may be set to be a sum of a radius of the transfer barrel  111  and a radius of the transfer barrel  110 . A gripper  111 A of the transfer barrel  111 , similarly to the transfer barrel  102 , the treatment barrel  104 , the transfer barrel  106 , the printing barrel  108 , and the transfer barrel  110 , is provided in plural number across the length corresponding to the maximum width of the paper sheet P at certain intervals in a direction perpendicular to the transporting direction of the paper sheet P. The transfer barrel  111  has rows of the grippers  111 A each of which row is arranged on the outer peripheral surface of the barrel at two locations symmetric about the rotation shaft, and is configured such that two paper sheets P can be transported per one rotation. 
     &lt;Application to Inkjet Recording Device&gt; 
       FIG. 17  is a general configuration diagram illustrating an embodiment of an inkjet recording device according to the embodiment. 
     The inkjet recording device  10 , which is an inkjet recording device using an aqueous UV ink (UV (ultraviolet) curable ink using an aqueous vehicle) to record an image on a printer sheet of paper sheet P (recording medium) by inkjet printing, is configured to mainly include a paper feed unit  12  for feeding a paper sheet P, a treatment liquid application unit  14  for applying a predetermined treatment liquid onto a surface (image record surface) of the paper sheet P fed from the paper feed unit  12 , a treatment liquid drying treatment unit  16  for subjecting the paper sheet P applied with the treatment liquid by the treatment liquid application unit  14 , an image recording unit  18  for recording an image by inkjet printing using the aqueous UV ink onto the surface of the paper sheet P having undergone a drying treatment by the treatment liquid drying treatment unit  16 , an ink drying treatment unit  20  for subjecting the paper sheet P having the image recorded thereon by the image recording unit  18  to the drying treatment, a UV irradiating treatment unit  22  for subjecting the paper sheet P having undergone the drying treatment by the ink drying treatment unit  20  to a UV irradiation treatment (fixing treatment) to fix the image, and a paper discharge unit  24  for discharging the paper sheet P having undergone the UV irradiation treatment by the UV irradiating treatment unit  22 . 
     &lt;Paper Feed Unit&gt; 
     The paper feed unit  12  feeds the paper sheet P stacked on a paper feed platform  30  one by one to the treatment liquid application unit  14 . The paper feed unit  12  is configured to mainly include the paper feed platform  30 , a sucking device (sucker)  32 , a paper feed roller pair  34 , a feeder board  36 , a front stop  38 , and a paper feed drum  40 . 
     The paper sheet P is placed on the paper feed platform  30  in a state of a stack in which plenty of sheets are piled up. The paper feed platform  30  is provided so as to be capable of being lifted and lowered by a paper feed platform lifting and lowering device (not illustrated). The paper feed platform lifting and lowering device is controlled to be driven in conjunction with increase and decrease of the paper sheets P stacked on the paper feed platform  30  to lift and lower the paper feed platform  30  such that the paper sheet P placed on the top of the stack is always positioned at a certain height. 
     The paper sheet P as the recording medium is not specifically limited, but a general purpose printing sheet used for general offset printing (paper sheet mainly made from cellulose such as so-called high-quality paper, coat paper, and art paper) can be used. In this example, coated paper is used. The coated paper is generally made by applying coating materials to give a coat layer onto a surface of high-quality paper, neutralized paper or the like not having undergone a surface treatment. Concretely, the art paper, coat paper, light weight coat paper, ultra-light weight coated paper and the like are preferably used. 
     The sucking device (sucker)  32  takes the paper sheets P stacked on the paper feed platform  30  sequentially from the top one by one to feed to the paper feed roller pair  34 . The sucking device (sucker)  32 , which includes a suction foot  32 A provided liftably and swingably, holds a top surface of the paper sheet P by suction by the suction foot  32 A to transport the paper sheet P from the paper feed platform  30  to the paper feed roller pair  34 . At this time, the suction foot  32 A holds a leading end side of the top surface of the paper sheet P placed on the top of the stack by suction to lift the paper sheet P and insert a leading end of the lifted paper sheet P between a pair of rollers  34 A and  34 B included in the paper feed roller pair  34 . 
     The paper feed roller pair  34  includes the vertical pair of rollers  34 A and  34 B which are pressed and abutted against each other. The vertical pair of rollers  34 A and  34 B has a driving roller (roller  34 A) as one of the pair and a driven roller (roller  34 B) as the other. The driving roller (roller  34 A) is driven by a motor (not illustrated) to be rotated. The motor is driven in conjunction of feeding of the paper sheet P so as to rotate the driving roller (roller  34 A) at a timing when the paper sheet P is fed from the sucking device (sucker)  32 . The paper sheet P inserted between the vertical pair of rollers  34 A and  34 B is nipped by the rollers  34 A and  34 B to be fed in a rotation direction of the rollers  34 A and  34 B (direction in which the feeder board  36  is arranged). 
     The feeder board  36 , which is formed corresponding to a paper width, receives the paper sheet P fed from the paper feed roller pair  34  and guides to the front stop  38 . The feeder board  36  is arranged so that the leading end side thereof is inclined downward, and slides the paper sheet P placed on a transporting surface of the feeder board  36  to guide to the front stop  38  along the transporting surface. 
     The feeder board  36  is provided with a plurality of tape feeders  36 A arranged at intervals in a width direction for transporting the paper sheet P. The tape feeder  36 A is formed to have no ends and driven by a motor (not illustrated) to be rotated. The paper sheet P placed on the transporting surface of the feeder board  36  is given a feed by the tape feeder  36 A to be transported on the feeder board  36 . 
     On the feeder board  36 , a retainer  36 B and a rolling member  36 C are arranged. 
     A plurality of retainers  36 B (two in the example) are arranged in tandem, front and back, along a transporting surface of the paper sheet P. The retainer  36 B includes a leaf spring having a width corresponding to the paper width, and arranged to be pressed and abutted against the transporting surface. The paper sheet P being transported on the feeder board  36  by the tape feeder  36 A is passed through the retainer  36 B to correct irregularity thereof. The retainer  36 B is formed to have a trailing end curled in order to easily insert the paper sheet P between the feeder board  36  and the retainer  36 B. 
     The rolling member  36 C is arranged between the front and back retainers  36 B. The rolling member  36 C is arranged so as to be pressed and abutted against the transporting surface of the paper sheet P. The paper sheet P being transported between the front and back retainers  36 B is transported with the top surface being held by the rolling member  36 C. 
     The front stop  38  corrects an attitude of the paper sheet P. The front stop  38  is formed into a plate-shape and arranged perpendicularly to a transporting direction of the paper sheet P. The front stop  38  is arranged swingably to be driven by a motor (not illustrated). The paper sheet P transported on the feeder board  36 , whose leading end is abutted against the front stop  38 , is corrected in attitude (so-called skew prevention). The front stop  38  swings in conjunction with feeding the paper sheet to the paper feed drum  40  to pass the paper sheet P corrected in attitude to the paper feed drum  40 . 
     The paper feed drum  40  receives the paper sheet P fed from the feeder board  36  via the front stop  38  to transport to the treatment liquid application unit  14 . The paper feed drum  40  is formed into a cylindrical shape and is rotated by a rotary drive mechanism described later (see  FIG. 18 ). The paper feed drum  40  has a gripper  40 A provided on an outer peripheral surface thereof, and the gripper  40 A grips the leading end of the paper sheet P. The paper feed drum  40  rotates with gripping by the gripper  40 A the leading end of the paper sheet P to wind the paper sheet P on the peripheral surface while transporting the paper sheet P to the treatment liquid application unit  14 . 
     The paper feed unit  12  is configured as described above. The paper sheets P stacked on the paper feed platform  30  are lifted by the sucking device (sucker)  32  sequentially from the top one by one to be fed to the paper feed roller pair  34 . The paper sheet P fed to the paper feed roller pair  34  is fed forward by the vertical pair of rollers  34 A and  34 B included in the paper feed roller pair  34  to be placed on the feeder board  36 . The paper sheet P placed on the feeder board  36  is transported by the tape feeder  36 A provided on the transporting surface of feeder board  36 . In this transporting course, the paper sheet P is pressed against the transporting surface of the feeder board  36  by the retainer  36 B to correct irregularity. The paper sheet P transported by the feeder board  36  abuts on the front stop  38  at the leading end thereof to be corrected in inclination, and thereafter, passed to the paper feed drum  40 . Then, the paper feed drum  40  transports the paper sheet P to the treatment liquid application unit  14 . 
     &lt;Treatment Liquid Application Unit&gt; 
     The treatment liquid application unit  14  deposits the predetermined treatment liquid onto a surface of the paper sheet P (image record surface). The treatment liquid application unit  14  is configured to mainly include a treatment liquid deposition drum  42  for transporting the paper sheet P and a treatment liquid deposition unit  44  for depositing a predetermined treatment liquid onto a printing surface of the paper sheet P being transported by the treatment liquid deposition drum  42 . 
     The treatment liquid deposition drum  42  receives the paper sheet P from the paper feed drum  40  in the paper feed unit  12  to transport the paper sheet P to the treatment liquid drying treatment unit  16 . The treatment liquid deposition drum  42  is formed into a cylindrical shape and is rotated by the rotary drive mechanism described later (see  FIG. 18 ). The treatment liquid deposition drum  42  has a gripper  42 A on an outer peripheral surface thereof, and the gripper  42 A grips the leading end of the paper sheet P. The treatment liquid deposition drum  42  rotates with gripping the leading end of the paper sheet P by the gripper  42 A to wind the paper sheet P on the peripheral surface while transporting the paper sheet P to the treatment liquid drying treatment unit  16  (one paper sheet P is transported per one rotation). The treatment liquid deposition drum  42  and the paper feed drum  40  are controlled to be rotated such that their timings of receiving and passing the paper sheet P coincide with each other. In other words, these drums are driven to have the same circumferential speed and driven such that positions of their grippers match each other. 
     The treatment liquid deposition unit  44  applies the treatment liquid by roller onto the surface of the paper sheet P being transported by the treatment liquid deposition drum  42 . The treatment liquid deposition unit  44  is configured to mainly include an application roller  44 A for applying the treatment liquid onto the paper sheet P, a treatment liquid tank  44 B for reserving the treatment liquid, and a drawing roller  44 C for drawing the treatment liquid reserved in the treatment liquid tank  44 B to supply to the application roller  44 A. The drawing roller  44 C is arranged to be pressed and abutted against the application roller  44 A and arranged to have a part thereof immersed in the treatment liquid reserved in the treatment liquid tank  44 B. The drawing roller  44 C measures and draws the treatment liquid to deposit the treatment liquid of a certain thickness onto a peripheral surface of application roller  44 A. The application roller  44 A is provided corresponding to the paper width, and pressed and abutted against the paper sheet P to apply the treatment liquid deposited onto the peripheral surface thereof onto the paper sheet P. The application roller  44 A is driven by an abutting and separation mechanism (not illustrated) to be moved between an abutting position where to abut the peripheral surface of the treatment liquid deposition drum  42  and a separating position where to separate from the peripheral surface of the treatment liquid deposition drum  42 . The abutting and separation mechanism moves the application roller  44 A at a timing when the paper sheet P is passing and applies the treatment liquid onto the surface of the paper sheet P being transported by the treatment liquid deposition drum  42 . 
     Note that in this example, the configuration is such that the treatment liquid is applied by roller, but a method for depositing the treatment liquid is not limited thereto. Other than this configuration, a configuration in which deposition is carried out by use of an inkjet head or a configuration in which deposition is carried out by spraying may be also employed. 
     The treatment liquid application unit  14  is configured as described above. The paper sheet P passed from the paper feed drum  40  in the paper feed unit  12  is received by the treatment liquid deposition drum  42 . The treatment liquid deposition drum  42  rotates with gripping the leading end of the paper sheet P by the gripper  42 A to wind the paper sheet P on the peripheral surface for transporting. In this transporting course, the application roller  44 A is pressed and abutted against the surface of the paper sheet P to apply the treatment liquid onto the surface of the paper sheet P. 
     Here, as the treatment liquid applied onto the surface of the paper sheet P, a treatment liquid is used which has a function to aggregate coloring materials in the aqueous UV ink whose droplets is to be deposited onto the paper sheet P in the image recording unit  18  at a subsequent stage. Application of such a treatment liquid onto the surface of the paper sheet P and deposition of the ink droplets of the aqueous UV ink allow an image of high quality to be printed without occurrence of landed ink droplets interference or the like even in a case where the general purpose printing sheet is used. 
     &lt;Treatment Liquid Drying Treatment Unit&gt; 
     The treatment liquid drying treatment unit  16  subjects the paper sheet P having the surface applied with treatment liquid to the drying treatment. This treatment liquid drying treatment unit  16  is configured to mainly include a treatment liquid drying treatment drum  46  for transporting the paper sheet P, a paper transporting guide  48 , and a treatment liquid drying treatment unit  50  for blowing hot air to the printing surface, so as to be dried, of the paper sheet P being transported by the treatment liquid drying treatment drum  46 . 
     The treatment liquid drying treatment drum  46  receives the paper sheet P from the treatment liquid deposition drum  42  in the treatment liquid application unit  14  to transport the paper sheet P to the image recording unit  18 . The treatment liquid drying treatment drum  46  includes a frame member assembled in a cylindrical shape and is rotated by a rotary drive mechanism described later (see  FIG. 17 ). The treatment liquid drying treatment drum  46  has a gripper  46 A on an outer peripheral surface thereof, and the gripper  46 A grips the leading end of the paper sheet P. The treatment liquid drying treatment drum  46  rotates with gripping the leading end of the paper sheet P by the gripper  46 A to wind the paper sheet P on the peripheral surface while transporting the image recording unit  18  and the paper sheet P. Note that the treatment liquid drying treatment drum  46  in this example has the gripper  46 A arranged at each of two points on the outer peripheral surface thereof to be configured such that two paper sheets P can be transported per one rotation. The treatment liquid drying treatment drum  46  and the treatment liquid deposition drum  42  are controlled to be rotated such that their timings of receiving and passing the paper sheet P coincide with each other. In other words, these drums are driven to have the same circumferential speed and driven such that positions of their grippers match each other. 
     The paper transporting guide  48  is arranged along a transporting path of the paper sheet P relating to the treatment liquid drying treatment drum  46  to guide the paper sheet P being transported. 
     The treatment liquid drying treatment unit  50 , which is arranged inside the treatment liquid drying treatment drum  46 , blows the hot air to the surface of the paper sheet P being transported by the treatment liquid drying treatment drum  46  to carry out the drying treatment. This example has a configuration in which two treatment liquid drying treatment units  50  are arranged inside the treatment liquid drying treatment drum and blow the hot air to the surface of the paper sheet P being transported by the treatment liquid drying treatment drum  46 . 
     The treatment liquid drying treatment unit  16  is configured as described above. The paper sheet P passed from the treatment liquid deposition drum  42  in the treatment liquid application unit  14  is received by the treatment liquid drying treatment drum  46 . The treatment liquid drying treatment drum  46  rotates with gripping the leading end of the paper sheet P by the gripper  46 A to transport the paper sheet P. At this time, the treatment liquid drying treatment drum  46  carries out transporting with the surface of the paper sheet P (surface applied with the treatment liquid) facing the inner side. The paper sheet P, in a course of being transported by the treatment liquid drying treatment drum  46 , is subjected to the drying treatment in which the surface thereof receives the hot air blown from the treatment liquid drying treatment unit  50  arranged inside the treatment liquid drying treatment drum  46 . In other words, solvent components in the treatment liquid are removed. This forms an ink aggregation layer on the surface of the paper sheet P. 
     &lt;Image Recording Unit&gt; 
     The image recording unit  18  deposits liquid droplets of ink (aqueous UV ink) of each of colors C, M, Y, and K onto the printing surface of the paper sheet P to render a color image on the printing surface of the paper sheet P. The image recording unit  18  is configured to include an image recording drum  52  for transporting the paper sheet P, a paper pressing roller  54  for pressing the paper sheet P being transported by the image recording drum  52  to bring the paper sheet P into tight contact with a peripheral surface of the image recording drum  52  (medium-holding device, medium-transporting device), inkjet heads  56 C,  56 M,  56 Y, and  56 K for ejecting and depositing ink droplets of each of colors C, M, Y, and K onto the paper sheet P, an inline sensor  58  for reading out the image recorded on the paper sheet P, a mist filter  60  for catching ink mist, and a drum cooling unit  62 . 
     The image recording drum  52  (an example of the printing barrel) receives the paper sheet P from the treatment liquid drying treatment drum  46  in the treatment liquid drying treatment unit  16  to transport the paper sheet P to the ink drying treatment unit  20 . The image recording drum  52  is formed into a cylindrical shape and is rotated by the rotary drive mechanism described later (see  FIG. 18 ). The image recording drum  52  has a gripper  52 A provided at a position sunk down inwardly from an outer peripheral surface thereof. The gripper  52 A grips the leading end of the paper sheet P inwardly by the distance d from the outer peripheral surface of the image recording drum  52 . The image recording drum  52  rotates with gripping by the gripper  52 A the leading end of the paper sheet P to wind the paper sheet P on the peripheral surface while transporting the paper sheet P to the ink drying treatment unit  20 . The image recording drum  52  has a plenty of sucking holes (not illustrated) formed on the peripheral surface thereof in a predetermined pattern. The paper sheet P wound on the peripheral surface of the image recording drum  52  is sucked from the sucking holes to be held by suction on the peripheral surface of the image recording drum  52  while being transported. This allows the paper sheet P to be transported with flatness being highly kept. 
     Sucking from the sucking holes works only in a certain range, that is, works between a predetermined sucking start position and a predetermined sucking end position. The sucking start position is set to an arrangement position of the paper pressing roller  54 , and the sucking end position is set on the downstream side of an arrangement position of the inline sensor  58  (e.g., set to a position where the paper sheet is passed to the ink drying treatment unit  20 ). In other words, the setting is made such that the paper sheet P is held by suction on the peripheral surface of the image recording drum  52  at least at the arrangement positions of the inkjet heads  56 C,  56 M,  56 Y, and  56 K (image record position), and the arrangement position of the inline sensor  58  (image readout position). 
     A mechanism for holding the paper sheet P by suction on the peripheral surface of the image recording drum  52  is not limited to a suction method owing to a negative pressure described above, but a method owing to electrostatic suction may be employed. 
     The image recording drum  52  in this example has the gripper  52 A arranged on the outer peripheral surface thereof at each of two locations to be configured such that two paper sheets P can be transported per one rotation. The image recording drum  52  and the treatment liquid drying treatment drum  46  are controlled to be rotated such that their timings of receiving and passing the paper sheet P coincide with each other. In other words, these drums are driven to have the same circumferential speed and driven such that positions of their grippers match each other. 
     The paper pressing roller  54  is arranged in the vicinity of a paper receiving position of the image recording drum  52  (position at which the paper sheet P is received from the treatment liquid drying treatment drum  46 ). The paper pressing roller  54 , which is formed of a rubber roller, is arranged to be pressed and abutted against the peripheral surface of the image recording drum  52 . The paper sheet P passed from the treatment liquid drying treatment drum  46  to the image recording drum  52  is passed through the paper pressing roller  54  to be nipped and then brought into tight contact with the peripheral surface of the image recording drum  52 . 
     Four inkjet heads  56 C,  56 M,  56 Y, and  56 K are arranged at certain intervals along the transporting path of the paper sheet P relating to the image recording drum  52 . Each of the inkjet heads  56 C,  56 M,  56 Y, and  56 K is formed of a line head corresponding to the paper width, and is arranged such that a nozzle face faces the peripheral surface of the image recording drum  52 . Each of inkjet heads  56 C,  56 M,  56 Y, and  56 K ejects liquid droplets of ink from a nozzle array formed at the nozzle face toward the image recording drum  52  to record an image on the paper sheet P being transported by the image recording drum  52 . 
     The aqueous UV ink is used for the ink ejected from each of the inkjet heads  56 C,  56 M,  56 Y, and  56 K as described above. The aqueous UV ink can be cured by being irradiated with ultraviolet (UV) rays after ink droplets deposition. 
     The inline sensor  58  is arranged on the downstream side of the tail end inkjet head  56 K with respect to the transporting direction of the paper sheet P by the image recording drum  52  to read out the image recorded by the inkjet heads  56 C,  56 M,  56 Y, and  56 K. The inline sensor  58 , which is formed of a line scanner, for example, reads out the image recorded by the inkjet heads  56 C,  56 M,  56 Y, and  56 K from the paper sheet P being transported by the image recording drum  52 . 
     Note that a contact prevention plate  59  is arranged on the downstream side of the inline sensor  58  in the vicinity of the inline sensor  58 . The contact prevention plate  59  prevents the paper sheet P from being brought into contact with the inline sensor  58  in a case of coming-off of the paper sheet P due to transporting failure or the like. 
     The mist filter  60  is arranged between the tail end inkjet head  56 K and the inline sensor  58  to suck an air around the image recording drum  52  for catching the ink mist. In this way, sucking the air around the image recording drum  52  for catching the ink mist can prevent the ink mist from entering the inline sensor  58  and can prevent read-out failure or the like from occurring. 
     The drum cooling unit  62  blows a cold air to the image recording drum  52  to cool the image recording drum  52 . The drum cooling unit  62  is configured to mainly include an air-conditioner (not illustrated), and a duct  62 A for blowing a cool air supplied from the air-conditioner to the peripheral surface of the image recording drum  52 . The duct  62 A blows the cool air to the area of the image recording drum  52  except for an area through which the paper sheet P is transported to cool the image recording drum  52 . The configuration in this example is such that since the paper sheet P is transported along a surface of an arc of an approximately upper half of the image recording drum  52 , the duct  62 A blows the cool air to an area of an approximately lower half of the image recording drum  52  to cool the image recording drum  52 . Specifically, a blowing-out opening of the duct  62 A is formed into an arc-shape so as to cover an approximately lower half of the image recording drum  52  to be configured such that the cool air is blown to the area of an approximately lower half of the image recording drum  52 . 
     Here, a temperature for cooling the image recording drum  52  is set in relation to a temperature of the inkjet heads  56 C,  56 M,  56 Y, and  56 K (particularly, temperature of the nozzle face), and the image recording drum is cooled to have a temperature lower than that of inkjet heads  56 C,  56 M,  56 Y, and  56 K. This can prevent dew condensation from occurring on the inkjet heads  56 C,  56 M,  56 Y, and  56 K. In other words, setting the temperature of the image recording drum  52  to be lower than that of the inkjet heads  56 C,  56 M,  56 Y, and  56 K can induce the dew condensation on the image recording drum side and can prevent the dew condensation from occurring on the inkjet heads  56 C,  56 M,  56 Y, and  56 K (particularly, dew condensation occurring on the nozzle face). 
     The image recording unit  18  is configured as described above. The paper sheet P passed from the treatment liquid drying treatment drum  46  in the treatment liquid drying treatment unit  16  is received by the image recording drum  52 . The image recording drum  52  rotates with gripping the leading end of the paper sheet P by the gripper  52 A to transport the paper sheet P. The paper sheet P passed to the image recording drum  52  firstly passes through the paper pressing roller  54  to be brought into tight contact with the peripheral surface of the image recording drum  52 . At the same time as this, the paper sheet P is sucked from the suction apertures of the image recording drum  52  to be held by suction on the outer peripheral surface of the image recording drum  52 . The paper sheet P is transported in this state while passing through each of the inkjet heads  56 C,  56 M,  56 Y, and  56 K. Then, in passing through the inkjet heads, the surface of the paper sheet P undergoes deposition of the liquid droplets of ink each of colors C, M, Y, and K from each of the inkjet heads  56 C,  56 M,  56 Y, and  56 K, respectively to render a color image on the relevant surface. The ink aggregation layer formed on the surface of the paper sheet P allows an image of high quality to be recorded without occurring feathering, bleeding and the like. 
     The paper sheet P having the image recorded thereon by the inkjet heads  56 C,  56 M,  56 Y, and  56 K is next to pass through the inline sensor  58 . In passing through the inline sensor  58 , the image recorded on the surface is read out. This reading out of the recorded image is carried out as needed such that the read out image is checked for deposition failure and the like. In carrying out of the reading out, the reading out is carried out in a state of being held by the image recording drum  52  by suction, allowing highly accurate reading out. Additionally, since the reading out is carried out immediately after recording the image, abnormity such as the deposition failure and the like can be immediately detected, for example, a measure against which can be rapidly taken. This can prevent recording in vain and can minimize occurrence of waste sheets. 
     After that, the paper sheet P is released from the suction, and thereafter, is passed to the ink drying treatment unit  20 . 
     &lt;Ink Drying Treatment Unit&gt; 
     The ink drying treatment unit  20  subjects the paper sheet P after image recording to the drying treatment to remove liquid components remained on the surface of the paper sheet P. The ink drying treatment unit  20  is configured to include a chain gripper  64  for transporting the paper sheet P having the image recorded thereon, a back tension giving mechanism  66  for giving a back tension to the paper sheet P being transported by the chain gripper  64 , an ink drying treatment unit  68  for subjecting the paper sheet P being transported by the chain gripper  64  to the drying treatment. 
     The chain gripper  64 , which is a paper transporting mechanism used in common by the ink drying treatment unit  20 , the UV irradiating treatment unit  22 , and the paper discharge unit  24 , receives the paper sheet P passed from the image recording unit  18  to transport to the paper discharge unit  24 . 
     The chain gripper  64  includes a first sprocket  64 A arranged in the vicinity of the image recording drum  52 , a second sprocket  64 B arranged in the paper discharge unit  24 , a chain  64 C, with no ends, wound around across the first sprocket  64 A and the second sprocket  64 B, a plurality of chain guides (not illustrated) for guiding run of the chain  64 C, and a plurality of grippers  64 D attached to the chain  64 C at certain intervals. The first sprockets  64 A, the second sprockets  64 B, the chains  64 C, and the chain guides are respectively formed into a pair to be arranged on both ends in the width direction of the paper sheet P. Each gripper  64 D is arranged to be put across the chains  64 C provided in a pair. 
     The first sprocket  64 A is arranged in the vicinity of the image recording drum  52  such that the paper sheet P passed from the image recording drum  52  is received by the gripper  64 D. The first sprocket  64 A is rotatably arranged by being journaled by a bearing (not illustrated) and is connected with a motor (not illustrated). The chain  64 C wound around across the first sprocket  64 A and the second sprocket  64 B runs by driving this motor. 
     The second sprocket  64 B is arranged in the paper discharge unit  24  such that the paper sheet P received from the image recording drum  52  is collected in the paper discharge unit  24 . In other words, the arrangement position of the second sprocket  64 B is a terminal of the transporting path of the paper sheet P relating to the chain gripper  64 . The second sprocket  64 B is rotatably arranged by being journaled by the bearing (not illustrated). 
     The chain  64 C is formed to have no ends and wound around across the first sprocket  64 A and the second sprocket  64 B. 
     The chain guides are arranged at predetermined positions to guide such that the chain  64 C runs a predetermined course (i.e., to guide such that the paper sheet P is transported while running a predetermined transporting path). In the inkjet recording device  10  in this example, the second sprocket  64 B is arranged at a position higher than the first sprocket  64 A. This forms a running course in which the chain  64 C becomes inclined in an intermediate portion. Specifically, the chain  64 C includes a first horizontal transporting path  70 A, an inclined transporting path  70 B, and a second horizontal transporting path  70 C. 
     The first horizontal transporting path  70 A is set to be at the same height as the first sprocket  64 A to set such that chain  64 C wound across the first sprocket  64 A horizontally runs. 
     The second horizontal transporting path  70 C is set to be at the same height as the second sprocket  64 B to set such that the chain  64 C wound across the second sprocket  64 B horizontally runs. 
     The inclined transporting path  70 B is set between the first horizontal transporting path  70 A and the second horizontal transporting path  70 C to set so as to link between the first horizontal transporting path  70 A and the second horizontal transporting path  70 C. 
     The chain guides are arranged to form the first horizontal transporting path  70 A, the inclined transporting path  70 B, and the second horizontal transporting path  70 C. Specifically, the chain guides are arranged at least at a joining point between the first horizontal transporting path  70 A and the inclined transporting path  70 B and at a joining point between the inclined transporting path  70 B and the second horizontal transporting path  70 C. 
     The plurality of grippers  64 D are attached to the chain  64 C at certain intervals. The attachment interval for the gripper  64 D is set corresponding to a reception interval at which the paper sheet P is received from the image recording drum  52 . In other words, the attachment interval is set to correspond to the reception interval of the paper sheet P from the image recording drum  52  such that the paper sheet P sequentially passed from the image recording drum  52  can be received from the image recording drum  52  at a timing of the paper sheet being passed. 
     The chain gripper  64  is configured as described above. As described above, when the motor (not illustrated) connected to the first sprocket  64 A is driven, the chain  64 C runs. The chain  64 C runs at the same speed as the circumferential speed of the image recording drum  52 . The timing is adjusted such that the paper sheet P passed from the image recording drum  52  can be received by each gripper  64 D. 
     The back tension giving mechanism  66  gives back tension to the paper sheet P which is transported while the leading end being gripped by the chain gripper  64 . The back tension giving mechanism  66  mainly includes a guide plate  72  and a sucking mechanism (not illustrated) for sucking an air from sucking holes (not illustrated) formed on the guide plate  72 . 
     The guide plate  72  includes a hollow box plate having a width corresponding to the paper width. The guide plate  72  is arranged along the transporting path of the paper sheet P relating to the chain gripper  64  (i.e., running course of the chain). Specifically, the guide plate  72  is arranged along the chain  64 C running the first horizontal transporting path  70 A and the inclined transporting path  70 B, and arranged to be separated from the chain  64 C by a predetermined distance. The paper sheet P being transported by the chain gripper  64  is transported with a back surface thereof (surface having no image recorded thereon) being slidably in contact with on a top surface of the guide plate  72  (surface facing the chain  64 C: slidable contact surface). 
     The slidable contact surface (top surface) of the guide plate  72  has plenty of sucking holes formed (not illustrated) in a predetermined pattern. As described above, the guide plate  72  is formed of the hollow box plate. The sucking mechanism (not illustrated) sucks a hollow portion (inside) of the guide plate  72 . This allows the air to be sucked from the sucking holes formed on the slidable contact surface. 
     Sucking the air from the sucking holes of the guide plate  72  causes the back surface of the paper sheet P being transported by the chain gripper  64  to be sucked to the sucking holes. This gives the back tension to the paper sheet P being transported by the chain gripper  64 . 
     As described above, since the guide plate  72  is arranged along the chain  64 C running the first horizontal transporting path  70 A and the inclined transporting path  70 B, the paper sheet P is given the back tension while being transported on the first horizontal transporting path  70 A and the inclined transporting path  70 B. 
     The ink drying treatment unit  68  is arranged inside the chain gripper  64  (particularly, a portion constituting first horizontal transporting path  70 A) to subject the paper sheet P being transported on the first horizontal transporting path  70 A to the drying treatment. The ink drying treatment unit  68  blows a hot air to the surface of the paper sheet P being transported on the first horizontal transporting path  70 A to be subjected to the drying treatment. A plurality of ink drying treatment units  68  are arranged along the first horizontal transporting path  70 A. The number of the ink drying treatment units  68  arranged is set depending on a capacity of the ink drying treatment unit  68 , a transporting speed of the paper sheet P (equal to the printing speed) or the like. In other words, the number is set such that the paper sheet P received from the image recording unit  18  can be dried while being transported on the first horizontal transporting path  70 A. Therefore, a length of the first horizontal transporting path  70 A is also set in consideration of the capacity of the ink drying treatment unit  68 . 
     Note that the drying treatment causes a humidity of the ink drying treatment unit  20  to be risen. Since rising of the humidity makes the efficient drying treatment difficult, it is preferable that the ink drying treatment unit  20  is provided with exhaust means together with the ink drying treatment unit  68  to forcibly exhaust humid air generated due to the drying treatment. The exhaust means may have a configuration in which, for example, an exhaust duct is arranged at the ink drying treatment unit  20  to exhaust the air in the ink drying treatment unit  20  by the exhaust duct. 
     The ink drying treatment unit  20  is configured as described above. The paper sheet P passed from the image recording drum  52  in the image recording unit  18  is received by the chain gripper  64 . The chain gripper  64  transports the paper sheet P along the planar guide plate  72  with gripping the leading end of the paper sheet P by the gripper  64 D. The paper sheet P passed to the chain gripper  64  is firstly transported on the first horizontal transporting path  70 A. In the course of being transported on the first horizontal transporting path  70 A, the paper sheet P is subjected to the drying treatment by the ink drying treatment unit  68  arranged inside the chain gripper  64 . In other words, the hot air is blown to the surface (image record surface) to be subjected to the drying treatment. At this time, the paper sheet P is given the back tension by the back tension giving mechanism  66  while being subjected to the drying treatment. By doing so, the paper sheet P can be prevented from being deformed while being subjected to the drying treatment. 
     &lt;UV Irradiating Treatment Unit&gt; 
     The UV irradiating treatment unit  22  irradiates the image recorded by use of the aqueous UV ink with ultraviolet (UV) rays to fix the image. The UV irradiating treatment unit  22  includes the chain gripper  64  for transporting the paper sheet P subjected to the drying treatment, the back tension giving mechanism  66  for giving the back tension to the paper sheet P being transported by the chain gripper  64 , and a UV irradiation unit  74  for irradiating the paper sheet P being transported by the chain gripper  64  with the ultraviolet rays. 
     As described above, the chain gripper  64  and the back tension giving mechanism  66  are used together in common by the ink drying treatment unit  20  and the paper discharge unit  24 . 
     The UV irradiation unit  74  is arranged inside the chain gripper  64  (particularly, a portion constituting the inclined transporting path  70 B) to irradiate with the ultraviolet rays the surface of the paper sheet P being transported on the inclined transporting path  70 B. A plurality of UV irradiation units  74 , each including the ultraviolet rays lamp (UV lamp), are arranged along the inclined transporting path  70 B. Then, the ultraviolet irradiation units  74  irradiate the ultraviolet rays toward the surface of the paper sheet P being transported on the inclined transporting path  70 B. The arranged number of the UV irradiation unit  74  is set depending on the transporting speed of the paper sheet P (equal to the printing speed) or the like. In other words, the configuration is such that the image can be fixed by the ultraviolet rays irradiated while the paper sheet P is transported on the inclined transporting path  70 B. Therefore, a length of the inclined transporting path  70 B is also set in consideration of the transporting speed of the paper sheet P or the like. 
     The UV irradiating treatment unit  22  is configured as described above. The paper sheet P transported by the chain gripper  64  to be subjected to the drying treatment by the ink drying treatment unit  20  is next transported on the inclined transporting path  70 B. In the course of being transported on the inclined transporting path  70 B, the paper sheet P is subjected to the UV irradiation treatment by the UV irradiation unit  74  arranged inside the chain gripper  64 . In other words, the ultraviolet rays are irradiated from the UV irradiation unit  74  toward the surface. At this time, the paper sheet P is given the back tension by the back tension giving mechanism  66  while being subjected to the UV irradiation treatment. By doing so, the paper sheet P can be prevented from being deformed while being subjected to the UV irradiation treatment. Since the UV irradiating treatment unit  22  is arranged on the inclined transporting path  70 B and the inclined transporting path  70 B is provided with the inclined guide plate  72 , even if the paper sheet P falls off the gripper  64 D in the middle of transportation, the paper sheet can be slid on the guide plate  72  to be taken out. 
     &lt;Paper Discharge Unit&gt; 
     The paper discharge unit  24  collects the paper sheet P having been subjected to a series of image recording processes. The paper discharge unit  24  is configured to mainly include the chain gripper  64  for transporting the paper sheet P having undergone UV irradiation, and a paper discharge platform  76  collecting the paper sheet P to be stacked thereon. 
     As described above, the chain gripper  64  is used together in common by the ink drying treatment unit  20  and the UV irradiating treatment unit  22 . The chain gripper  64  releases the paper sheet P on the paper discharge platform  76  to stack the paper sheet P on the paper discharge platform  76 . 
     The paper discharge platform  76  collects the paper sheet P released by the chain gripper  64  to be stacked thereon. The paper discharge platform  76  is provided with paper stops (front paper stop, rear paper stop, side paper stop or the like) (not illustrated) so as to neatly stack the paper sheet P. 
     The paper discharge platform  76  is provided so as to be capable of being lifted and lowered by a paper discharge platform lifting and lowering device (not illustrated). The paper discharge platform lifting and lowering device is controlled to be driven in conjunction with increase and decrease of the paper sheets P stacked on the paper discharge platform  76  to lift and lower the paper discharge platform  76  such that the paper sheet P placed on the top is always is positioned at a certain height. 
     &lt;Configuration of Paper Sheet Transporting Device&gt; 
     In the inkjet recording device  10  configured as described above, the transporting path including at least the treatment liquid deposition drum  42 , the treatment liquid drying treatment drum  46 , and the image recording drum  52  corresponds to the paper sheet transporting device. 
       FIG. 18  is a configuration diagram illustrating a lateral side opposite to that illustrated in  FIG. 17 , and illustrates the rotary drive mechanism for the paper feed drum  40 , treatment liquid deposition drum  42 , treatment liquid drying treatment drum  46 , and image recording drum  52  (an example of the plural transporting barrels). As illustrated in the figure, the inkjet recording device  10  includes a toothed wheel (gear)  90  directly coupled in a concentric manner with a rotation shaft of the paper feed drum  40 , a toothed wheel  92  directly coupled in a concentric manner with a rotation shaft of the treatment liquid deposition drum  42 , a toothed wheel  94  directly coupled in a concentric manner with a rotation shaft of the treatment liquid drying treatment drum  46 , and a toothed wheel  96  directly coupled in a concentric manner with a rotation shaft of the image recording drum  52 . 
     The respective toothed wheels  90  to  96  are formed to have the same diameters as the paper feed drum  40 , the treatment liquid deposition drum  42 , the treatment liquid drying treatment drum  46 , and the image recording drum  52 , respectively, to which the respective toothed wheels are directly coupled. In this example, radiuses of the paper feed drum  40  and the treatment liquid deposition drum  42  are r 1 , and radiuses of the treatment liquid drying treatment drum  46  and the image recording drum  52  are r 2 . r 1  and r 2  have a relationship of r 2 =2×r 1  (an example of integral multiple relationship with each other). 
     The toothed wheel  90  and the toothed wheel  92  engage with each other. The toothed wheel  92  and the toothed wheel  94  engage with other, and the toothed wheel  94  and the toothed wheel  96  engage with each other. The inter-shaft distance between the paper feed drum  40  and the treatment liquid deposition drum  42  is set to be 2×r 1 , and the inter-shaft distance between the treatment liquid deposition drum  42  and the treatment liquid drying treatment drum  46  is set to be r 1 +r 2 . The inter-shaft distance between the treatment liquid drying treatment drum  46  and the image recording drum  52  is set to be r 1 +r 2 −d with the drive ratio being maintained by shifting the toothed wheel  96 . 
     The inkjet recording device  10  has a motor for rotation (not illustrated) provided thereto as a motive power source for the paper sheet transporting system. The motive power from the motor for rotation is transmitted to the toothed wheels  90 ,  92 ,  94 , and  96  in this order, and these toothed wheels  90 ,  92 ,  94 , and  96  work in conjunction with each other to rotate the paper feed drum  40 , the treatment liquid deposition drum  42 , the treatment liquid drying treatment drum  46 , and the image recording drum  52 . In the case of this example, when the paper feed drum  40  rotates two revolutions, the treatment liquid deposition drum  42  rotates two revolution, and the treatment liquid drying treatment drum  46  and the image recording drum  52  rotate one revolution. 
     In the paper sheet transporting path configured in this way, the gripper  40 A of the paper feed drum  40 , the gripper  42 A of the treatment liquid deposition drum  42 , and the gripper  46 A of the treatment liquid drying treatment drum  46  are each arranged on outer peripheral surface thereof, and thus, the trajectory of the leading end portion of the paper sheet P is continuous, and the passing of the paper sheet P via the grippers is carried out with no paper sheet deformation being generated. 
     The gripper  52 A of the image recording drum  52  is arranged inwardly by the distance d from the outer peripheral surface of the image recording drum  52 , but the inter-shaft distance between the treatment liquid drying treatment drum  46  and the image recording drum  52  is set to be r 1 +r 2 −d, and thus, the gripper  46 A of the treatment liquid drying treatment drum  46  and the gripper  52 A of the image recording drum  52  align on the same line at a position where the paper sheet P is passed. Therefore, the trajectory of the leading end portion of the paper sheet P is continuous, and the passing of the paper sheet P via the grippers is carried out with no paper sheet deformation being generated. 
     In this way, according to the inkjet recording device  10 , the arrangement of the grippers of the image recording drum sunk down inwardly of the image recording drum enables the high-definition inkjet printing. Moreover, the paper sheet distortion can be suppressed to be small and a degree of contact of the paper sheet with the image recording drum can be increased, which enables the high-definition inkjet printing. Further, the inter-shaft distance between the image recording drum and the drum at the prior stage of image recording drum is set to be shorter by an amount involved by arranging the grippers of the image recording drum inwardly from the outer peripheral surface with the drive ratio being maintained by shifting the toothed wheel of the image recording drum, and other inter-shaft distances between the drums than those described above are set to be a sum of the radiuses of these drums, which makes it possible to arrange the grippers of the drums other than the image recording drum on the outer peripheral surfaces of the respective drums, allowing the stable transportation. 
     The technical scope of the present invention is not limited to a scope described in the above embodiments. The configuration or the like in the embodiments may be appropriately combined between the respective embodiments without departing from the gist of the present invention.