Patent Publication Number: US-10328721-B2

Title: Printing apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a National Stage of International Application No. PCT/JP2016/070169 filed Jul. 7, 2016, claiming priority based on Japanese Patent Application Nos. 2015-155075 filed Aug. 5, 2015, 2015-155076 filed Aug. 5, 2015, 2015-155077 filed Aug. 5, 2015 and 2015-197368 filed Oct. 5, 2015, the contents of all of which are incorporated herein by reference in their entirety. 
     TECHNICAL FIELD 
     The present invention relates to a printing apparatus. 
     BACKGROUND ART 
     In Patent Document 1, there is disclosed a printer including: a mandrel wheel; plural automatically-rotatable mandrels provided in the mandrel wheel; and plural ink jet printing stations for forming print images onto an outer surface of a cylindrical container installed in the mandrel. 
     CITATION LIST 
     Patent Literature 
     Patent Document 1: Japanese Patent Application Laid-Open Publication No. 2014-50786 
     SUMMARY OF INVENTION 
     Technical Problem 
     To form an image onto a can body, for example, an image forming unit that performs image formation onto the can body by ejecting ink to be cured by irradiation of light is provided, and the ink is ejected from the image forming unit toward the can body. Then, the can body is irradiated with light, such as ultraviolet light, to cure the ink on the can body. 
     Here, when the light irradiated onto the can body heads for the image forming unit, curing of ink occurs at the image forming unit, and therefore, it becomes difficult to form an image, or quality of an image to be formed is deteriorated. 
     An object of the present invention is to prevent light for curing an image on a can body from reaching an image forming unit. 
     Moreover, in a printing apparatus performing printing onto a can body, for example, a can body support member is rotated, to thereby rotate the can body in a circumferential direction, and ink is caused to adhere to an outer circumferential surface of the rotating can body to perform printing. 
     Here, in a configuration providing plural can body support members and also providing plural driving sources corresponding to the respective can body support members, manufacturing costs are increased. Moreover, to perform printing, printing is performed per each color in some cases, and in these cases, alignment among images of respective colors is required. In such cases, if a driving source is provided per each can body support member, a process of aligning the images is apt to be complicated. 
     Another object of the present invention is to reduce the driving sources for rotating the respective plural can body support members. 
     Moreover, in image formation onto a can body, image formation is performed by plural image forming units in some cases, and in these cases, alignment among images formed by the respective image forming units is required. 
     Alignment of images can be performed by, for example, detecting a status of the can body by a sensor and performing image formation based on the detection result; however, if the sensor is used in this manner, the process is apt to be complicated. 
     Another object of the present invention is to perform alignment among images formed on a can body by respective plural image forming units easier. 
     Moreover, to form an image on a can body, for example, plural image forming units that perform image formation onto the can body by ejecting ink are provided, the can body is moved among the plural image forming units in order, and the can body is stopped at positions facing the respective image forming units, to thereby perform image formation. 
     Here, even in a case in which movement of the can body is stopped at the positions facing the respective image forming units, the can body vibrates in some cases when image formation is started at the image forming units. Then, when the can body vibrates, there is a possibility that positions of ink ejection by the image forming units are varied and the quality of images formed by the image forming units is deteriorated. 
     Another object of the present invention is, when the can body is moved to the plural image forming units in order to form the images, to reduce vibration of the can body in starting image formation at each image forming unit. 
     Solution to Problem 
     A printing apparatus to which the present invention is applied includes: a can body conveyance unit that sequentially conveys can bodies and, every time each of the can bodies reaches each of predetermined plural can body stop locations, temporarily stops the can body; an image forming unit that is installed at any of the plural can body stop locations and performs image formation onto the can body positioned at the can body stop location; and a light irradiation unit that is installed at another can body stop location positioned on a downstream side of the can body stop location, where the image forming unit is installed, in a conveyance direction of the can bodies, and performs light irradiation to an image formed onto the can body by the image forming unit, wherein one or more other can body stop locations are provided between an image formation stop location, which is the can body stop location where the image forming unit is installed, and a light irradiation stop location, which is the can body stop location where the light irradiation unit is installed. 
     Here, a restricting wall that restricts light emitted from the light irradiation unit from heading toward the image forming unit is further included. 
     Moreover, the restricting walls are plurally provided to correspond to the respective can bodies conveyed by the can body conveyance unit, and move in association with the respective can bodies conveyed by the can body conveyance unit, and the plural restricting walls are provided, when one of the can bodies is stopped at the light irradiation stop location, to cause one of the plural restricting walls corresponding to the can body to be positioned on an upstream side of the can body in the can body conveyance direction. 
     Moreover, two or more of the restricting walls are provided for each of the can bodies, and, when the each can body is stopped at the light irradiation stop location, one of the restricting walls corresponding to the can body is positioned on an upstream side of the can body in the can body conveyance direction, and the other of the restricting walls corresponding to the can body is positioned on a downstream side of the can body in the can body conveyance direction. 
     Moreover, the image forming unit performs image formation on the can body by ejecting ink onto the can body, and an ink ejection direction when the image forming unit ejects the ink and a light emitting direction in light emission by the light irradiation unit are the same. 
     Moreover, the image forming units are plurally provided, the light irradiation unit is positioned on a downstream side of the plural image forming units in a moving direction of the can body, and light irradiation by the light irradiation unit is performed after image formation onto the can body by the plural image forming units is performed. 
     From another standpoint, a printing apparatus to which the present invention is applied includes: plural can body support members that are provided rotatably to support can bodies; an image forming unit that performs image formation onto the can bodies supported by the can body support members; and a transmission member that performs circulating movement through each of the plural can body support members to transmit a rotational driving force to each of the plural can body support members. 
     Here, the plural can body support members are radially disposed around a predetermined disposition center, the transmission member is formed into an annular shape to perform circulating movement assuming a center in a radial direction as a movement center, and the plural can body support members and the transmission member are provided to cause the disposition center and the movement center to coincide with each other. 
     Moreover, the transmission member is installed closer to the disposition center side than the plural can body support members that are radially disposed. 
     Moreover, a receiving member that receives a driving force from the transmission member is provided to each of the can body support members, and the receiving member is formed into a helical shape. 
     Moreover, a receiving member that receives a driving force from the transmission member is provided to each of the can body support members, and the receiving member is more likely to wear than the transmission member. 
     Moreover, the image forming units are plurally provided, and a moving unit that moves the can body support members through each of the plural image forming units is further included. 
     From another standpoint, a printing apparatus to which the present invention is applied includes: plural image forming units, each of which ejects ink onto an outer circumferential surface of a rotating can body to form an image on the outer circumferential surface; and a moving unit that moves a can body through each of the plural image forming units while rotating the can body, wherein a number of rotations of the can body during a period from starting moving of the can body from one of two of the image forming units adjacent to each other in a moving direction of the can body to reaching the other of the two image forming units becomes an integer. 
     Here, when image formation onto the can body is performed at each of the plural image forming units, the can body is rotated for a predetermined number of rotations, and, when the can body is moved from one of the two image forming units to the other thereof, the can body is rotated for a number of rotations larger than the predetermined number of rotations. 
     Moreover, when image formation onto the can body is performed at each of the plural image forming units, the can body is rotated for a predetermined number of rotations, and, when the can body is moved from one of the two image forming units to the other thereof, the can body is rotated for a number of rotations smaller than the predetermined number of rotations. 
     Moreover, the printing apparatus further includes: an inspection unit that performs inspection of a can body before image formation onto the can body by the plural image forming units is performed; and a discharge unit that discharges a can body, which is determined not to satisfy a predetermined condition by the inspection unit, before image formation onto the can body by the plural image forming units is performed. 
     Moreover, the can body is supported by a cylindrical member inserted into the can body, and the cylindrical member is formed with a diameter of one end portion side in a lead when being inserted into the can body to be smaller than a diameter of the other end portion side. 
     From another standpoint, a printing apparatus to which the present invention is applied includes: plural image forming units, each of which ejects ink onto an outer circumferential surface of a rotating can body to form an image on the outer circumferential surface; a moving unit that moves and stops a can body to and at each of the plural image forming units to cause the can body to pass through each of the plural image forming units; and a rotating unit that rotates a can body after the can body is stopped at each of the plural image forming units by the moving unit, wherein each of the plural image forming units starts image formation onto the can body after the can body is rotated a predetermined number of times by the rotating unit. 
     Here, each of the image forming units starts image formation onto the can body after the can body is rotated an integer number of times by the rotating unit. In this case, it becomes possible to perform alignment among the images formed on the can body by the respective plural image forming units easier. 
     Moreover, the rotating unit rotates the can body to cause image formation starting positions by the respective image forming units to coincide with one another. 
     Further, the rotating unit rotates the can body to cause image formation starting positions by the respective image forming units to be shifted in a circumferential direction of the can body. 
     Still further, the rotating unit rotates the can body to cause a moving direction of the can body by the moving unit and a rotation direction of the can body at a portion facing each of the image forming units to coincide with each other. 
     Moreover, there is further included a light irradiation unit that is provided on a downstream side of the plural image forming units in a moving direction of the can body and performs light irradiation onto the image formed on the can body by the plural image forming units, wherein the rotating unit rotates a can body after the can body is stopped at the light irradiation unit by the moving unit, and the light irradiation unit starts light irradiation onto the can body when the can body is rotated by the rotating unit. 
     Advantageous Effects of Invention 
     According to the present invention, it is possible to prevent light for curing the image on the can body from reaching the image forming unit. 
     Moreover, according to the present invention, it is possible to reduce the driving sources for rotating the respective plural can body support members. 
     Moreover, according to the present invention, it is possible to perform alignment among the images formed on the can body by the respective plural image forming units easier. 
     Moreover, according to the present invention, it is possible to, when the can body is moved to the plural image forming units in order to form the images, reduce vibration of the can body in starting image formation at each image forming unit. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram in which a printing apparatus is viewed from above; 
         FIG. 2  is a diagram in which an ink jet head and a can body are viewed from a direction of arrow II in  FIG. 1 ; 
         FIG. 3  is a diagram in which an inspection mechanism is viewed from a direction of arrow III in  FIG. 1 ; 
         FIG. 4  is a schematic view in which two ink jet heads adjacent to each other are viewed from a direction of arrow IV in  FIG. 1 ; 
         FIG. 5  is a diagram in which a lamp container box and mandrels are viewed from a direction of arrow V in  FIG. 1 ; and 
         FIG. 6  is a diagram illustrating the mandrel. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, an exemplary embodiment according to the present invention will be described in detail with reference to attached drawings. 
       FIG. 1  is a diagram in which a printing apparatus  100  related to the exemplary embodiment is viewed from above. 
     The printing apparatus  100  shown in  FIG. 1  forms an image onto a can body  10  used as a beverage can or the like based on digital image information. Moreover, the printing apparatus  100  forms an image on the can body  10  by use of an ink jet method. 
     The printing apparatus  100  is provided with a control part (not shown) that controls respective devices and respective mechanisms provided to the printing apparatus  100 . The control part is composed of a program-controlled CPU. 
     Moreover, the printing apparatus  100  is provided with a rotation member  210  that is driven by a not-shown motor and rotates intermittently in a direction indicated by arrow  1 A in the figure. The rotation member  210  is formed into a columnar shape to rotate around a rotation axis  1 B indicated by a reference sign  1 B in the figure. The rotation axis  1 B extends in the vertical direction. 
     Moreover, the printing apparatus  100  is provided with plural (in the exemplary embodiment, 16) holding mechanisms  230  that are provided to protrude from an outer circumferential surface of the rotation member  210  and hold the can bodies  10 . 
     As indicated by the reference sign  1 X, each of the holding mechanisms  230  is provided with a shaft  230 S protruding from the outer circumferential surface of the rotation member  210 . The shaft  230 S is rotatable in the circumferential direction. 
     Moreover, as indicated by the reference sign  1 X, each of the holding mechanisms  230  is provided with a mandrel  230 M as an example of a can body support member that supports the can body  10 . The mandrel  230 M is attached to a tip end of the shaft  230 S. 
     Further, between the mandrel  230 M and the rotation member  210 , a receiving gear  230 G as an example of a receiving member that receives a rotational driving force is provided. 
     The receiving gear  230 G is attached to an outer circumferential surface of the shaft  230 S. 
     Moreover, the receiving gear  230 G is composed of a helical gear. Further, the receiving gear  230 G is engaged with a transmission gear  50  in an annular shape (to be described in detail later) and receives the rotational driving force from the transmission gear  50 . 
     The plural shafts  230 S and the plural mandrels  230 M are provided, and these shafts  230 S and mandrels  230 M are disposed radially around a disposition center  1 C indicated by the reference sign  1 C in the figure. Note that the disposition center  1 C coincides with the rotation axis  1 B of the rotation member  210 . 
     The can body  10  is formed into a cylindrical shape. Moreover, a bottom portion is formed at an end portion in the longitudinal direction of the can body  10  to close the end portion. On the other hand, the other end portion of the can body  10  is not closed and left opened. 
     As indicated by arrow  1 G in  FIG. 1 , the mandrel  230 M is inserted into the can body  10  from the open side, and thereby the can body  10  is supported by the mandrel  230 M. 
     Further, below the plural holding mechanisms  230  that are radially disposed and on the outside of the rotation member  210  in the radial direction, the annular-shaped transmission gear  50  that functions as a transmission member or a rotation member is provided. The transmission gear  50  is engaged with the receiving gears  230 G provided to the respective holding mechanisms  230 , and thereby the rotational driving force is transmitted to the receiving gears  230 G to rotate the mandrels  230 M. 
     More specifically, the transmission gear  50  is formed into an annular shape and circularly moves (orbitally moves) in the direction indicated by arrow  1 D in the figure. Then, in the exemplary embodiment, the receiving gears  230 G are engaged with the transmission gear  50  that is circularly moving, and thereby the receiving gears  230 G are rotated to rotate the mandrels  230 M (the can bodies  10 ) in the direction indicated by the arrow  1 E. 
     Here, the transmission gear  50  circularly moves around the center in the radial direction that is assumed to be a movement center  1 F; however, in the exemplary embodiment, the movement center  1 F and the disposition center  1 C of the mandrels  230 M radially disposed coincide with each other. 
     To additionally describe, when the printing apparatus  100  is viewed from above, the movement center  1 F and the disposition center  1 C are positioned at the same location. Further, at the location where the movement center  1 F and the disposition center  1 C are positioned, the rotation axis  1 B of the rotation member  210  is also positioned. 
     Further, in the exemplary embodiment, the transmission gear  50  is positioned closer to the disposition center  1 C side than the radially-disposed mandrels  230 M. 
     Consequently, in the exemplary embodiment, the printing apparatus  100  can be maintained with ease as compared to a case in which the transmission gear  50  is provided to an opposite side of the disposition center  1 C (to an outer side than the mandrels  230 M in the radial direction of the rotation member  210 ). 
     In doing maintenance, the mandrels  230 M are attached or detached in some cases, and in these cases, if the transmission gear  50  is provided to the disposition center  1 C side, the mandrels  230 M can be accessed with ease as compared to the case in which the transmission gear  50  is provided to the opposite side of the disposition center  1 C. This makes it possible to attach or detach the mandrels  230 M easier and to enhance ease of maintenance. 
     Further, in the exemplary embodiment, the transmission gear  50  is formed of a metallic material, and the receiving gear  230 G is formed of a resin material. Consequently, the receiving gear  230 G is more likely wear than the transmission gear  50 . This also makes it easier to do maintenance. 
     If the transmission gear  50  is more likely to wear, when the gears are replaced, it becomes necessary to attach and detach the transmission gear  50 , which is larger than the receiving gear  230 G; therefore, a lot of trouble is taken. 
     Moreover, the printing apparatus  100  is provided with 6 ink jet heads  240  that function as image forming units. 
     The 6 ink jet heads  240  are arranged along the moving direction of the can body  10 . Further, the 6 ink jet heads  240  are disposed radially, too. Further, the ink jet heads  240  are disposed above the can body  10 , to thereby eject ink toward the can body  10  positioned below. 
       FIG. 2  is a diagram in which the ink jet head  240  and the can body  10  (the can body  10  supported by the mandrel  230 M) are viewed from the direction of arrow II in  FIG. 1 . 
     As shown in  FIG. 2 , the ink jet head  240  is disposed above the can body  10 . Further, the ink jet head  240  includes a lower surface  241  that faces the can body  10 , and the lower surface  241  is provided with plural ink ejection ports (not shown) that eject ink. 
     The ink jet head  240  in the exemplary embodiment ejects ultraviolet cure ink to form an image onto the outer circumferential surface of the can body  10 . 
     Further, the 6 ink jet heads  240  are provided in the exemplary embodiment, and the respective ink jet heads  240  eject ink of different colors, such as yellow, magenta, cyan, black, white or a special color, from one another onto the can body  10 . 
     Moreover, as shown in  FIG. 1 , in the exemplary embodiment, in the rotation direction of the rotation member  210  (the conveyance direction of the can body  10 ), a UVLED (Ultraviolet Light Emitting Diode) lamp  250  that functions as a light irradiation unit is provided on a downstream side of the 6 ink jet heads  240 . The outer circumferential surface of the can body  10  is irradiated with ultraviolet light from the UVLED lamp  250 , and thereby the ultraviolet cure ink constituting an image on the outer circumferential surface of the can body  10  is cured. 
     Further, a lamp container box  70  for containing the UVLED lamp  250  is provided. By providing the lamp container box  70 , the ultraviolet light is prevented from heading toward anything other than the can body  10 . 
     The lamp container box  70  is provided with an inlet portion  71 , through which the mandrel  230 M (the can body  10 ) passes when entering the lamp container box  70 , and an outlet portion  72 , through which the mandrel  230 M passes when exiting from the lamp container box  70 . 
     The rotation member  210 , which functions as a can body conveyance unit and a moving unit, causes the mandrel  230 M (the can body  10 ) to pass through the respective plural ink jet heads  240  to move thereof. Further, the rotation member  210  temporarily stops rotation per every rotation of 22.5 degrees. 
     Consequently, the exemplary embodiment has a configuration providing 16 mandrel stop locations (can body stop locations)  801  to  816  in total. 
     In the exemplary embodiment, the rotation member  210  is rotated to sequentially convey the can bodies  10  along a predetermined orbital route, and the can body  10  is temporarily stopped every time the can body  10  reaches each of the 16 mandrel stop locations. 
     In the exemplary embodiment, the ink jet heads  240  are provided to 6 mandrel stop locations  804  to  809 , of the 16 mandrel stop locations  801  to  816 ; further, to another one mandrel stop location  811 , a UVLED lamp  250  is provided. 
     Further, the exemplary embodiment includes a configuration in which one other mandrel stop location (the mandrel stop location indicated by the reference sign  810 ) is provided between the mandrel stop locations  804  to  809  provided with the ink jet heads  240  (hereinafter, referred to as “image formation stop locations  804  to  809 ” in some cases) and the mandrel stop location  811  provided with the UVLED lamp  250  (hereinafter, referred to as “light irradiation stop location  811 ” in some cases). 
     Here, in the exemplary embodiment, ultraviolet light is emitted from the UVLED lamp  250 , and when the ultraviolet light reaches the ink jet head  240  positioned on the upstream side, there occurs a possibility that the ink is cured to cause ink clogging in the ink jet head  240 , and thereby quality of an image to be formed is deteriorated. 
     Therefore, in the exemplary embodiment, as described above, by providing one mandrel stop location  810  between the image formation stop locations  804  to  809  and the light irradiation stop location  811  to increase a separation distance between the UVLED lamp  250  and the ink jet heads  240 , to thereby reduce ultraviolet light that reaches the ink jet heads  240 . 
     Note that, in the exemplary embodiment, there is provided one mandrel stop location  810  between the image formation stop locations  804  to  809  and the light irradiation stop location  811 ; however, two or more mandrel stop locations may be provided. 
     Further, in the exemplary embodiment, an ink ejection direction when the ink jet head  240  ejects ink toward the can body  10  and a light emitting direction when the UVLED lamp  250  emits light toward the can body  10  are the same. 
     Specifically, the ink ejection direction when the ink jet head  240  ejects ink toward the can body  10  is a downward direction, and the light emitting direction when the UVLED lamp  250  emits light toward the can body  10  is also a downward direction. This also reduces the ultraviolet light that reaches the ink jet heads  240 . 
     Here, for example, in a configuration in which the UVLED lamp  250  is disposed below the can body  10 , the ultraviolet light is emitted upwardly. On the other hand, in the ink jet head  240 , the ink ejection ports are provided to the lower surface  241  (refer to  FIG. 2 ). 
     In this case, as compared to the case in which the ink ejection direction and the light emitting direction are the same as in the exemplary embodiment, the ultraviolet light is likely to reach the ink ejection ports, and therefore, curing of ink easily occurs in the ink jet heads  240 . 
     Further, in the printing apparatus  100  of the exemplary embodiment, as shown in  FIG. 1 , a can body loading portion  91  is provided on an upstream side of the plural ink jet heads  240 . 
     At the can body loading portion  91 , inside of the mandrel  230 M formed into a cylindrical shape is caused to have negative pressure, and the mandrel  230 M sucks the can body  10  to insert the mandrel  230 M into the inside of the can body  10 . Consequently, support of the can body  10  by the mandrel  230 M is started. 
     Between the can body loading portion  91  and the ink jet heads  240 , an inspection mechanism  92  as an example of an inspection unit that investigates the loaded can body  10  is provided. 
     In the exemplary embodiment, the inspection mechanism  92  is provided on the upstream side of the ink jet heads  240 ; thereby, inspection of the can body  10  is performed prior to image formation by the ink jet heads  240 . 
     Specifically, the inspection mechanism  92  inspects whether or not the can body  10  is deformed. 
     More specifically, the inspection mechanism  92  is, as shown in  FIG. 3  (a diagram in which the inspection mechanism  92  is viewed from the direction of arrow III in  FIG. 1 ), provided with a light source  92 A on one end portion side of the can body  10 , the light source  92 A emitting laser light that proceeds in the axial direction of the can body  10  along the outer circumferential surface of the can body  10 . Further, on the other end portion side of the can body  10 , there is provided a light receiving portion  92 B that receives laser light from the light source  92 A. 
     When part of the can body  10  is deformed as indicated by the reference sign  3 A, the laser light is cut off and the light receiving portion  92 B cannot receive the laser light. Consequently, deformation of the can body  10  is detected. 
     Moreover, it is possible to provide a reflective laser detection device  92 C that includes both of a light projecting portion with a light source for emitting laser light and a light receiving portion for receiving laser light to the inspection mechanism  92 . The reflective laser detection device  92 C emits laser light from the light projecting portion toward the bottom of the can, the emitted laser light is reflected off the bottom of the can, the reflected laser light is received by the light receiving portion, and thereby the distance to the bottom of the can be detected based on the time from light emitting to light receiving. Consequently, it is possible to detect whether the can body  10  is perfectly mounted to the mandrel  230 M. Moreover, by forming a groove as shown in the figure onto the mandrel  230 M, it is possible to detect presence or absence of the can body  10 . 
     Then, in the exemplary embodiment, when it is determined by the inspection mechanism  92  that the can body  10  does not satisfy predetermined conditions (it is determined that the can body  10  is deformed), a discharge mechanism  93  (refer to  FIG. 1 ) as an example of a discharge unit discharges the can body  10  to the outside of the printing apparatus  100 . 
     Here, the discharge mechanism  93  is, as shown in  FIG. 1 , disposed between the inspection mechanism  92  and the ink jet heads  240  (disposed on the upstream side of the ink jet heads  240 ), and therefore, in the exemplary embodiment, the can body  10  is discharged before image formation by the ink jet heads  240  is performed. 
     In the discharge mechanism  93 , compressed air is supplied to the inside of the mandrel  230 M, to move the can body  10  in the direction indicated by arrow  1 H in the figure. Further, the bottom portion (the closed end portion) of the can body  10  is sucked by a not-shown suction member. Then, by the suction member, the can body  10  is conveyed to the outside of the printing apparatus  100 , and the can body  10  is discharged to the outside of the printing apparatus  100 . 
     Here, if the deformed can body  10  reaches the ink jet head  240 , there is a possibility that the can body  10  comes into contact with the ink jet head  240 , and thereby the ink jet head  240  is damaged. In the exemplary embodiment, the deformed can body  10  is discharged to the outside of the printing apparatus  100  before reaching the ink jet head  240 , to suppress damage to the ink jet head  240 . 
     With reference to  FIG. 1 , the printing apparatus  100  will be further described. 
     On the downstream side of the UVLED lamp  250  (at the mandrel stop location  813 ), a paint application device  94  is provided. 
     The paint application device  94  includes a rotation body (not shown) capable of putting paint on an outer circumferential surface thereof, and brings the outer circumferential surface thereof into contact with the outer circumferential surface of the can body  10 , to thereby apply the paint to the outer circumference of the can body  10 . By applying the paint, a protection layer is formed on the outer circumferential surface of the can body  10 . 
     Thereafter, in the exemplary embodiment, at a can body discharge portion  95  (at the mandrel stop location  815 ) on the downstream side of the paint application device  94 , the can body  10  is discharged. 
     Specifically, by supplying the compressed air to the inside of the mandrel  230 M, the can body  10  is detached from the mandrel  230 M, and further, the can body  10  is conveyed to the outside of the printing apparatus  100  by a not-shown conveyance mechanism. Note that the can body  10  conveyed to the outside of the printing apparatus  100  is conveyed to a not-shown baking operation and subjected to heating processing. 
     Note that the above-described rotation body provided to the paint application device  94  has a large diameter. 
     Therefore, in the exemplary embodiment, a single mandrel stop location (the mandrel stop locations  812  and  814 ) is provided between the paint application device  94  and the can body discharge portion  95 , and between the paint application device  94  and the UVLED lamp  250 , to thereby prevent interference between the rotation body provided to the paint application device  94  and the can body discharge portion  95  and interference between the rotation body and the UVLED lamp  250 . 
     With reference to  FIG. 1 , a series of operations of the printing apparatus  100  will be described. 
     To perform printing by the printing apparatus  100 , first, rotation of the transmission gear  50  in the direction indicated by arrow  1 D is started, and rotation of the mandrel  230 M in the direction indicated by arrow  1 E is started. In the exemplary embodiment, in printing, the transmission gear  50  is always rotated for a constant number of rotations. 
     Next, in the exemplary embodiment, at the can body loading portion  91 , the can body  10  having been conveyed from the upstream side is mounted to the mandrel  230 M. 
     Specifically, in the exemplary embodiment, the can body  10  is conveyed from the upstream side to the can body loading portion  91 ; on this occasion, at the can body loading portion  91 , the empty mandrel  230 M is on standby. Further, the inside of the mandrel  230 M is caused to have a negative pressure, and, inside the mandrel  230 M, a ventilation hole (not shown) communicating with the outside is laid, to thereby suck the can body  10  through the ventilation hole. 
     Consequently, the mandrel  230 M is inserted into the inside of the can body  10 , and thereby support of the can body  10  by the mandrel  230 M is started. 
     After the support of the can body  10  by the mandrel  230 M has been started, the rotation member  210  having been in a stopped state rotates 22.5 degrees in the direction indicated by arrow  1 A in the figure, and is stopped again. Consequently, the can body  10  reaches the inspection mechanism  92 . Thereafter, the rotation member  210  rotates 22.5 degrees again. Consequently, the can body  10  reaches the discharge mechanism  93 . Thereafter, the rotation member  210  rotates 22.5 degrees again. Consequently, the can body  10  reaches below the first ink jet head  240 . 
     Then, in the exemplary embodiment, from the first ink jet head  240 , ink is ejected toward the can body  10  that is positioned below and rotating, and thereby an image by ink of a first color is formed onto the outer circumferential surface of the can body  10 . 
     In the exemplary embodiment, in this manner, ink is ejected toward the can body  10  from above the can body  10 . In this case, the acting direction of gravity and the ink ejection direction coincide with each other; accordingly, behavior of ejected ink becomes stable, and therefore, the ejection position of ink can be controlled with more accuracy. 
     Thereafter, in the exemplary embodiment, rotation of the rotation member  210  is restarted, and the can body  10  reaches below the second ink jet head  240 . Then, an image by ink of a second color is formed by the second ink jet head  240 . 
     Thereafter, in the exemplary embodiment, movement of the can body  10  to the third ink jet head  240 , image formation by the third ink jet head  240 , movement of the can body  10  to the fourth ink jet head  240  and image formation by the fourth ink jet head  240  are performed. Further, in the fifth ink jet head  240  and the sixth ink jet head  240 , images are formed similarly. 
     Note that, in the exemplary embodiment, description has been given by taking the case in which all of the 6 ink jet heads  240  are used to form the images as an example; however, of the 6 ink jet heads  240 , partial ink jet heads  240  may be used to form images. 
     Here, in the exemplary embodiment, the can body  10  is rotating while moving between the ink jet heads  240 . Consequently, unevenness in adhered ink hardly occurs. 
     When the can body  10  is moved in a state where rotation of the can body  10  is stopped, there is a possibility that the ink adhered to the can body  10  moves downward by gravity and unevenness in adhered ink occurs. 
     Further, in the exemplary embodiment, the number of rotations of the can body  10  is increased while the can body  10  moves between the ink jet heads  240 . Specifically, in the exemplary embodiment, when an image is formed onto the can body  10  in each ink jet head  240 , the can body  10  is rotated for a predetermined number of rotations, whereas, when the can body  10  moves between the ink jet heads  240 , the number of rotations of the can body  10  becomes larger than the predetermined number of rotations. 
     More specifically, in the exemplary embodiment, when an image is formed onto the can body  10  in each ink jet head  240 , each of the mandrels  230 M is rotated in the direction indicated by arrow  1 E in the figure by rotation of the transmission gear  50 . 
     When the mandrel  230 M moves to the downstream side from this state, the receiving gear  230 G moves, and by the movement, the receiving gear  230 G rotates with respect to the transmission gear  50 . Consequently, the number of rotations of the receiving gear  230 G is increased, and the number of rotations of the can body  10  is increased in accordance with this. 
     Here, when the number of rotations is increased like this, the ink on the outer circumferential surface of the can body  10  is likely to be cured. More specifically, when thermosetting ink, not the ultraviolet cure ink as in the exemplary embodiment, is used for example, the ink is likely to be dried as the number of rotations is increased, and thereby, the ink is cured more quickly as compared to a case in which the number of rotations is not increased. 
     To additionally describe, in the above, the case in which the ultraviolet cure ink is used is described; however, in the printing apparatus  100  of the exemplary embodiment, thermosetting ink can also be used, and in this case, when the number of rotations of the can body  10  is increased, the ink is cured more quickly as compared to a case in which the number of rotations is not increased. 
     Note that, when the can body  10  moves between the ink jet heads  240 , the number of rotations of the can body  10  may be reduced. Here, reduction of the number of rotations can be performed by rotating the transmission gear  50  not in the direction indicated by arrow  1 D, but in the opposite direction indicated by arrow  1 D. 
     When the can body  10  is going to move to the downstream side in the state where the transmission gear  50  is rotating in the opposite direction indicated by arrow  1 D, the receiving gear  230 G comes to rotate in the direction that reduces the number of rotations of the can body  10 , and in accordance with this, the number of rotations of the can body  10  is reduced. 
     When the number of rotations of the can body  10  is reduced in this manner, the total number of rotations of the receiving gear  230 G or the shaft  230 S is reduced, and thereby wear in the receiving gear  230 G or the shaft  230 S can be suppressed as compared to a case in which the number of rotations is constant or is increased as described above. 
     Further, in the exemplary embodiment, the number of teeth of the transmission gear  50 , the number of rotations of the transmission gear  50 , the number of teeth of the receiving gear  230 G, the number of rotations of the receiving gear  230 G and the like are set so that the number of rotations of the can body  10  in moving between the ink jet heads  240  becomes an integer. 
     To put it another way, in the printing apparatus  100  of the exemplary embodiment, the number of rotations of the can body  10  during a period from starting to move the can body  10  from one of the two ink jet heads  240  adjacent to each other in the moving direction of the can body  10  to reaching the other thereof becomes an integer. 
     To describe further, during the period from starting to move the can body  10  from one of the two ink jet heads  240  adjacent to each other in the moving direction of the can body  10  to reaching the other thereof, the can body  10  moves while rotating around the axis of the can, and the number of the rotation becomes an integer multiple of a single rotation. 
       FIG. 4  is a schematic view in which two ink jet heads  240  adjacent to each other are viewed from the direction indicated by arrow IV in  FIG. 1 . 
     In the exemplary embodiment, the can body  10  is always rotating, and the can body  10  moves from one of the ink jet heads  240  positioned on the upstream side (the ink jet head  240  on the right side in the figure, which is hereinafter referred to as “upstream-side ink jet head  240 A”) to the other of the ink jet heads  240  positioned on the downstream side (the ink jet head  240  on the left side in the figure, which is hereinafter referred to as “downstream-side ink jet head  240 B”) while rotating. 
     Then, in the exemplary embodiment, the number of rotations of the can body  10  during the period from starting to move the can body  10  from the upstream-side ink jet head  240 A to reaching the downstream-side ink jet head  240 B is an integer. 
     Consequently, in the exemplary embodiment, when the can body  10  reaches the downstream-side ink jet head  240 B, an adhesion starting position P 1  of the can body  10 , where the ink ejected from the upstream-side ink jet head  240 A is adhered first, is positioned at a position facing the downstream-side ink jet head  240 B. 
     Accordingly, in the exemplary embodiment, a sensor or controlling for alignment becomes unnecessary. 
     Here, in the upstream-side ink jet head  240 A, a strip-shaped image extending from the adhesion starting position P 1  (the position indicated by the reference sign  3 A) where the ink is first adhered to an adhesion finishing position P 2  (the position similarly indicated by the reference sign  3 A) where the ink is finally adhered is formed on the outer circumferential surface of the can body  10 . 
     Then, in the exemplary embodiment, the can body  10  moves while rotating, and when the can body  10  reaches below the downstream-side ink jet head  240 B, the adhesion starting position P 1  is located at the position facing the lower surface  241  of the downstream-side ink jet head  240 B. 
     Then, in the exemplary embodiment, ink is ejected at the same time when the can body  10  reaches below the downstream-side ink jet head  240 B, to thereby perform image formation. 
     More specifically, in the exemplary embodiment, movement of the can body  10  is started at the same time when image formation is finished at the upstream-side ink jet head  240 A (at the same time when the adhesion starting position P 1  faces the upstream-side ink jet head  240 A again after the single rotation of the can body  10 ). 
     Then, at the same time when the can body  10  reaches below the downstream-side ink jet head  240 B (at the same time when the adhesion starting position P 1  faces the downstream-side ink jet head  240 B), ejection of ink from the downstream-side ink jet head  240 B is started, to thereby start image formation. 
     Here, in the exemplary embodiment, when image formation at the downstream-side ink jet head  240 B is started, the adhesion starting position P 1  is positioned directly below the downstream-side ink jet head  240 B. 
     Consequently, in the exemplary embodiment, an image formation starting position when image formation at the upstream-side ink jet head  240 A is started and an image formation starting position when image formation at the downstream-side ink jet head  240 B is started coincide with each other. 
     Then, in this case, control for aligning the image formation starting positions becomes unnecessary. 
     Here, if the adhesion starting position P 1  does not face the downstream-side ink jet head  240 B when the can body  10  reaches the downstream-side ink jet head  240 B, control for causing the adhesion starting position P 1  to face the downstream-side ink jet head  240 B is required. 
     Specifically, it becomes necessary to, for example, detect the state of the can body  10  by a rotary encoder or the like, and rotate the can body  10  based on the detection result. In contrast to this, in the exemplary embodiment, such control is unnecessary and the image formation starting positions can be aligned easier. 
     Here, if the image formation starting positions are aligned, deterioration of image quality due to misalignment of the image formation starting positions can be suppressed. 
     At the location of the image formation starting positions, a starting point and an end of the image formed in the strip shape overlap or a gap is formed between the starting point and the end, and accordingly, the image quality is likely to be deteriorated. 
     As in the exemplary embodiment, if the image formation starting positions are aligned, the portions where the image quality is likely to be deteriorated can be concentrated to one location. In contrast to this, if the image formation starting positions are not aligned, the portions where the image quality is deteriorated are apt to be scattered all over the can body  10 . 
     Note that the number of rotations of the can body  10  during the period from starting to move the can body  10  from the upstream-side ink jet head  240 A to reaching the downstream-side ink jet head  240 B may be any value as long as being an integer, which may be 1 or 2 or more. 
     Note that, depending on the type of the image to be formed onto the can body  10 , the image formation starting positions for forming images at the respective ink jet heads  240  may be shifted. For example, when images consecutive in the circumferential direction are to be formed onto the outer circumferential surface of the can body  10 , it is preferable to shift the image formation starting positions in the respective ink jet heads  240 . 
     As described above, when the image formation starting positions are aligned, the portions where the image quality is likely to be deteriorated are concentrated to one location. For this reason, in the case of images consecutive in the circumferential direction of the can body  10 , if the image formation starting positions are aligned, there is a possibility that the deterioration of image quality is easily noticeable. In contrast to this, by shifting the image formation starting positions, concentration of low image quality portions on consecutive images can be suppressed. 
     As a method of shifting the image formation starting positions by the respective ink jet heads  240 , though not particularly limited, for example, shifting the ink ejection timing by the respective ink jet heads  240  or differentiating the number of rotations of the can body  10  by the transmission gear  50  can be provided. 
     Moreover, in the exemplary embodiment, after the can body  10  has reached below each ink jet head  240 , the can body  10  may be rotated before starting image formation at each ink jet head  240 . To put it another way, after the can body  10  has moved between the ink jet heads  240  by rotation of the rotation member  210  and has reached below the ink jet head  240 , the transmission gear  50  is moved in the state where the rotation of the rotation member  210  (movement of the can body  10 ) is stopped. Consequently, it may be possible that, after rotating the can body  10  (the mandrel  230 M) the predetermined number of times, image formation by the ink jet head  240  is started. 
     When rotation of the rotation member  210  is stopped after the can body  10  is moved to the location below each ink jet head  240  by the rotation of the rotation member  210 , the mandrel  230 M does not absolutely stop and vibrates in some cases. Particularly, in a case where the shaft  230 S extending from the rotation member  210  is long or the rotation speed of the rotation member  210  is high, vibration of the mandrel  230 M attached to a circumferential end of the shaft  230 S is apt to be increased. 
     Then, when the mandrel  230 M vibrates, the can body  10  supported by the mandrel  230 M also vibrates, and thereby, deterioration of image quality occurs in the image formed onto the surface of the can body  10  by the ink jet heads  240  in some cases. 
     In contrast to this, after the can body  10  has reached below the ink jet head  240 , the can body  10  is rotated and image formation by the ink jet head  240  is started. More specifically, after the can body  10  reached below the ink jet head  240  and a certain period of time has passed since rotation of the can body  10 , image formation by the ink jet head  240  is started. This suppresses vibration of the can body  10  when image formation is started, to thereby suppress deterioration of image quality in the image formed onto the can body  10 . 
     Other than this, it may be possible to stop the rotation of the can body  10  or reduce the rotation speed of the can body  10  while the can body  10  reaches below the ink jet head  240  and is rotated for a certain period of time. However, in this case, when image formation by the ink jet head  240  is started, it is necessary to accelerate the can body  10 , which has been stopped or decelerated, to the rotation speed required to perform image formation, and vibration sometimes occurs in the can body  10  on this occasion. Consequently, it is preferable that the rotation speed of the can body  10  is at the same degree as the rotation speed in image formation. 
     Moreover, by providing a configuration in which, below each ink jet head  240 , the can body  10  is rotated an integer number of times in the state where rotation of the rotation member  210  (movement of the can body  10 ) is stopped, it becomes easy to align the image formation starting positions with respect to the respective ink jet heads  240 . This further suppresses deterioration of image quality due to misalignment of the image formation starting positions. 
     Still further, in the exemplary embodiment, the moving direction of the can body  10  by the rotation member  210  and the rotation direction of the can body  10  at the position facing the ink jet head  240  coincide with each other. By adopting such a configuration, the moving direction of the surface of the can body  10  as viewed from the ink jet head  240  side is constant (always the same direction). Consequently, as compared to a case in which, for example, the moving direction of the can body  10  by the rotation member  210  and the rotation direction of the can body  10  at the position facing the ink jet head  240  do not coincide with each other, occurrence of air turbulence is suppressed. 
     As a result, behavior of ink ejected from the ink jet head  240  becomes stable, and it is possible to control the ink ejection position with respect to the can body  10  with more accuracy. As a result, deterioration of image quality formed onto the can body  10  is further suppressed. 
     With reference to  FIG. 1 , operations after the can body  10  has passed through the ink jet heads  240  will be described. 
     The can body  10  passed through the ink jet heads  240  moves to the location below the UVLED lamp  250 , and the outer circumferential surface of the can body  10  is irradiated with ultraviolet light. Specifically, the can body  10  is rotated below the UVLED lamp  250 , and thereby the outer circumferential surface of the can body  10  is irradiated with the ultraviolet light. Consequently, the ink on the outer circumferential surface of the can body  10  is cured. 
     Here, as described above, in the case where the can body  10  is rotated before starting image formation at the ink jet head  240 , the can body  10  conveyed to the location below the UVLED lamp  250  is rotated similarly. 
     In this case, at the UVLED lamp  250 , different from the ink jet head  240 , irradiation of the ultraviolet light may be started in time with starting the rotation of the can body  10 . Consequently, as compared to a case in which, for example, irradiation of the ultraviolet light is started after the can body  10  is rotated a predetermined number of times, irradiation time of the ultraviolet light against the can body  10  becomes longer. Therefore, the ink on the outer circumferential surface of the can body  10  is more likely to be cured. 
     Moreover, the ultraviolet cure ink is cured by a certain amount of light. Therefore, since the irradiation time of the ultraviolet light against the can body  10  can be made longer, it becomes possible to reduce illumination of the UVLED lamp  250 , which is the light source. Consequently, it becomes possible to extend the life of the UVLED lamp  250 . 
     Thereafter, in the exemplary embodiment, a paint is applied onto the outer circumferential surface of the can body  10  by the paint application device  94 . 
     Next, at the can body discharge portion  95 , the compressed air is supplied to the inside of the mandrel  230 M, the compressed air supplied to the inside of the mandrel  230 M is then supplied to the outside of the mandrel  230 M via the laid ventilation hole (not shown), and the compressed air supplied to the outside of the mandrel  230 M presses the inner surface of the can body  10  mounted to the mandrel  230 M, to thereby detach the can body  10  from the mandrel  230 M. The can body  10  detached from the mandrel  230 M is conveyed to a not-shown baking operation and heating processing is performed. Consequently, the paint applied to the can body  10  is cured. 
       FIG. 5  is a diagram in which a lamp container box  70  and the mandrels  230 M are viewed from a direction of arrow V in  FIG. 1 . Note that, in  FIG. 5 , illustration of the can body  10  is omitted. 
     Though the description is omitted in the above, in the exemplary embodiment, as shown in  FIG. 5 , an upstream-side restricting wall  31  and a downstream-side restricting wall  32  are provided beside each mandrel  230 M (each can body  10 ). 
     The upstream-side restricting wall  31  is positioned on the upstream side of the mandrel  230 M in the rotation direction of the rotation member  210 , and the downstream-side restricting wall  32  is positioned on the downstream side of the mandrel  230 M in the rotation direction of the rotation member  210 . 
     Moreover, the upstream-side restricting wall  31  and the downstream-side restricting wall  32  are provided along the axial direction of the mandrel  230 M and also along the vertical direction. 
     Moreover, the plural (plural sets of) upstream-side restricting wall  31  and downstream-side restricting wall  32  are provided to correspond to the respective plural mandrels  230 M (can bodies  10 ), and move in association with the respective mandrels  230 M. 
     In the exemplary embodiment, a support shaft  33  protruding from the outer circumferential surface of the rotation member  210  is provided, and the upstream-side restricting wall  31  and the downstream-side restricting wall  32  are supported by the support shaft  33 . 
     The support shaft  33  is disposed between two mandrels  230 M adjacent to each other in the rotation direction of the rotation member  210 , and a plate material  34  extending along the horizontal direction is attached to the support shaft  33 . The upstream-side restricting wall  31  and the downstream-side restricting wall  32  are supported by the plate material  34 . 
     As shown in  FIG. 1 , the upstream-side restricting wall  31  is positioned on the upstream side (the side on which an ink jet head  240  is provided) of the can body  10  when the can body  10  is stopped at a mandrel stop location  811  (light irradiation stop location  811 ). The upstream-side restricting wall  31  is thereby positioned between the can body  10  and the ink jet head  240 , and ultraviolet light is restricted from heading toward the ink jet head  240 . 
     Further, as shown in  FIG. 1 , when the can body  10  stops at the mandrel stop location  811 , the upstream-side restricting wall  31  closes the inlet portion  71  (also refer to  FIG. 5 ) of the lamp container box  70 . Consequently, the ultraviolet light is prevented from heading toward the ink jet head  240  through the inlet portion  71 . 
     On the other hand, as shown in  FIG. 1 , when the can body  10  stops at the mandrel stop location  811 , the downstream-side restricting wall  32  is positioned on the downstream side of the can body  10 . Consequently, leakage of the ultraviolet light from the outlet portion  72  of the lamp container box  70  can be suppressed. 
     Here, it is possible to provide shatters that are moved by a driving source, such as a solenoid, to the inlet portion  71  and the outlet portion  72 , to thereby close the inlet portion  71  and the outlet portion  72  by the shatters. 
     However, in this case, when the can body  10  passes through the inlet portion  71  and the outlet portion  72 , the shatters are required to be retracted, and thereby the configuration is complicated. In the exemplary embodiment, without causing such complication of the configuration, the inlet portion  71  and the outlet portion  72  can be closed. 
       FIG. 6  is a diagram illustrating the mandrel  230 M. 
     The mandrel  230 M in the exemplary embodiment as an example of a cylindrical member is formed of a member in a cylindrical shape. Further, in the exemplary embodiment, the diameter of one end portion  237  is smaller than the diameter of the other end portion  238 . 
     More specifically, in the exemplary embodiment, when the mandrel  230 M is inserted into the can body  10  with the one end portion  237  in the lead, and the diameter of the one end portion  237  side is smaller than the diameter of the other end portion  238  side. To describe further, in the exemplary embodiment, the outer circumferential surface and the one end portion  237  of the mandrel  230 M are tapered in such a way that the outer diameter of the mandrel  230 M is reduced with a move from the other end portion  238  side toward the one end portion  237  side. 
     Here, when the diameter of the one end portion  237  side is made smaller than the diameter of the other end portion  238  side as in the exemplary embodiment, wear of the mandrel  230 M is suppressed. 
     More specifically, when the mandrel  230 M is inserted into the can body  10 , a tip end of the mandrel  230 M is less likely to contact the can body  10 , and therefore, wear of the mandrel  230 M is suppressed. 
     Particularly, in the exemplary embodiment, since the mandrel  230 M is inserted into the can body  10  in the state where the mandrel  230 M is rotating (since, in the can body loading portion  91  (refer to  FIG. 1 ), the can body  10  is mounted to the mandrel  230 M that is rotating), wear of the mandrel  230 M is apt to occur. If the diameter of the one end portion  237  side is made smaller as in the exemplary embodiment, the wear is less likely to occur. 
     Note that, in the exemplary embodiment, as a result of the diameter of the one end portion  237  side being made smaller, a gap is formed between the outer circumferential surface of the one end portion  237  and the inner circumferential surface of the can body  10 . In the exemplary embodiment, even though such a gap exists, since printing is performed by the ink jet method (since printing is performed by adhering ink changed into minute ink droplets, and no external force is generated in the can body  10  during printing), image formation onto the can body  10  can be performed without deforming the can body  10  by printing. Here, in a plate processing method, not in the ink jet method, that transfers an image by pressing a plate against the outer circumferential surface of the can body  10 , the can body  10  is dented inward at the portion where the gap is formed, and thereby the can body  10  is deformed. 
     (Others) 
     In the exemplary embodiment, as described above, the UVLED lamp  250  is installed on the downstream side of the plural ink jet heads  240 , and after the image formation onto the can body  10  by the plural ink jet heads  240  is performed, light irradiation by the UVLED lamp  250  is carried out. 
     To put it another way, irradiation of ultraviolet light is not performed every time the image formation by a single ink jet head  240  is conducted, but is performed after images are formed by 6 ink jet heads  240 . 
     In this case, the number of UVLED lamps  250  can be reduced as compared to the case in which irradiation of ultraviolet light is performed every time the image formation by a single ink jet head  240  is carried out. Moreover, if the number of UVLED lamps  250  is reduced, the printing apparatus  100  can be downsized. 
     Note that irradiation of ultraviolet light may be performed every time the image formation by a single ink jet head  240  is carried out; in this case, each new mandrel stop locations is provided between two ink jet heads  240  that are adjacent to each other in the moving direction of the can body  10 , and the UVLED lamp  250  is installed to the mandrel stop location. 
     Note that, in this case also, it is preferable to provide one or more other mandrel stop locations are provided between the new mandrel stop location where the UVLED lamp  250  is installed and the mandrel stop location where the ink jet head  240  is installed. 
     More specifically, in this case, the ink jet head  240  is provided on each of the upstream side and downstream side of a single UVLED lamp  250 , and it is preferable to provide the one or more mandrel stop locations between the single UVLED lamp  250  and the upstream-side ink jet head  240  and between the single UVLED lamp  250  and the downstream-side ink jet head  240 . 
     Moreover, when irradiation of ultraviolet light is performed every time the image formation by the ink jet head  240  is carried out, it may be possible that the ink jet head  240  and the UVLED lamp  250  are provided to a single mandrel stop location and image formation and irradiation of ultraviolet light are performed at each single mandrel stop location. 
     More specifically, the ink jet head  240  is provided to one of the two locations at positions different from each other in the rotation direction of the can body  10  and the UVLED lamp  250  is provided to the other location (to the location on the downstream side of the ink jet head  240 ), and the ultraviolet light is irradiated after image formation by the ink jet head  240 . 
     Note that, in this case also, it is preferable to provide the restricting wall that restricts the ultraviolet light from reaching the ink jet head  240  between the UVLED lamp  250  and the ink jet head  240 . 
     REFERENCE SIGNS LIST 
     
         
           10  Can body 
           31  Upstream-side restricting wall 
           32  Downstream-side restricting wall 
           50  Transmission gear 
           92  Inspection mechanism 
           93  Discharge mechanism 
           210  Rotation member 
           230 G Receiving gear 
           230 M Mandrel 
           237  One end portion 
           238  The other end portion 
           240  Ink jet head 
           250  UVLED lamp 
           801  to  816  Mandrel stop location (Can body stop location)