Patent Publication Number: US-9902170-B2

Title: Irradiation device and droplets ejecting device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2016-125255 filed on Jun. 24, 2016. 
     BACKGROUND 
     Technical Field 
     The present invention relates to an irradiation device and a droplets ejecting device. 
     SUMMARY 
     According to an aspect of the invention, there is provided an irradiation device comprising: an irradiation unit that is disposed downstream of an election unit that ejects droplets, in a movement direction of a medium that is moved relative to the ejection unit so as to form a gap between itself and the medium, and that irradiates, with light, droplets that have been ejected from the ejection unit and landed on the medium; and a transparent member that is shaped like a belt, transmits light, and is moved through the gap relative to the irradiation unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present invention will be described in detail based on the following figures, wherein: 
         FIG. 1  is a front view outlining a droplets ejecting device according to a first exemplary embodiment of the present invention; 
         FIG. 2  is a front view outlining a droplets ejecting device according to a second exemplary embodiment of the invention; 
         FIG. 3  is a front view outlining a droplets ejecting device according to a first modification; 
         FIG. 4  is a front view outlining a droplets ejecting device according to a second modification; 
         FIG. 5  is a front view outlining a droplets electing device according to a third modification; and 
         FIG. 6  is a front view outlining a droplets ejecting device according to a fourth modification. 
     
    
    
     DESCRIPTION OF SYMBOLS 
     
         
           10 : Droplets ejecting device 
           10 A: Droplets electing device 
           10 B: Droplets ejecting device 
           10 C: Droplets ejecting device 
           10 D: Droplets ejecting device 
           10 E: Droplets ejecting device 
           32 : Election unit 
           32 Y: Ejection unit 
           32 M: Ejection unit 
           32 C: Ejection unit 
           32 K: Ejection unit 
           34 : Irradiation device 
           34 Y: Irradiation device 
           34 M: Irradiation device 
           34 C: Irradiation device 
           34 K: Irradiation device 
           36 : Irradiation unit 
           36 Y: Irradiation unit 
           36 M: Irradiation unit 
           36 C: Irradiation Unit 
           36 K: Irradiation unit 
           50 : First roll (example of first rotary body) 
           56 : Second roll (example of second rotary body) 
           56 A: Drive roll 
         A: Movement direction 
         B: Movement direction 
         BL: Blade (example of removing member) 
         BT: Transparent belt (example of transparent member) 
         BT 1 : Transparent belt (example of transparent member) 
         G: Gap 
         P: Medium 
       
    
     DETAILED DESCRIPTION 
     Modes for carrying out the present invention will hereinafter described as two (first and second) exemplary embodiments. 
     Exemplary Embodiment 1 
     The configuration, an image forming operation, and advantages of a droplets ejecting device  10  according to a first exemplary embodiment will be described below in order with reference to  FIG. 1 .  FIG. 1  is a front view of the droplets ejecting device  10  according to the first exemplary embodiment. 
     &lt;Configuration&gt; 
     The droplets electing device  10  according to this exemplary embodiment is an inkjet device which forms a final image on a medium P by forming an image of ink droplets (hereinafter referred to as an ink image) on the medium P and irradiating the ink image (i.e., ink droplets that have landed on the medium P) with light while conveying the medium P. The droplets ejecting device  10  includes a conveying unit  20 , an image forming device  30 , and a controller  40 . 
     [Conveying Unit  20 ] 
     The conveying unit  20  has a function of conveying a medium P along a conveyance path. Arrow A in  FIG. 1  indicates a feeding direction (movement direction) of a medium P being conveyed by the conveying unit  20  (this also applies to  FIGS. 2-5 ). In the exemplary embodiment, the conveying unit  20  conveys a medium P in the device width direction of the droplets ejecting device  10 . While a medium P is being conveyed by the conveying unit  20 , it is moved relative to ejection units  32 Y,  32 M,  32 C, and  32 K (described later). 
     [Image Forming Device  30 ] 
     The image forming device  30  has a function of forming a final image by forming an ink image (i.e., an image composed of ink droplets) on a medium P and irradiating the ink image (i.e., ink droplets that have landed on the medium P) with light. To this end, the image forming device  30  is disposed so as to be opposed to (the front surface of) a medium P being conveyed. The image forming device  30  is equipped with image forming units  30 Y,  30 M,  30 C, and  30 K, which are the same in configuration except what relate to formation of ink images of different colors (e.g., Y (yellow), M (magenta), C (cyan), and K (black). The image forming units  30 Y,  30 M,  30 C, and  30 K are arranged in this order upstream in the medium movement direction. 
     The image forming units  30 Y,  30 M,  30 C, and  30 K include ejection units  32 Y,  32 M,  32 C, and  32 K and irradiation devices  34 Y,  34 M,  34 C, and  34 K, respectively. In the following description, as for the image forming units  30 Y,  30 M,  30 C, and  30 K, the ejection units  32 Y,  32 M,  32 C, and  32 K, and the irradiation devices  34 Y,  34 M,  34 C, and  34 K, the alphabetical characters Y, M, C, and K indicating the colors will be omitted if it is not necessary to discriminate between the units  30 Y,  30 M,  30 C, and  30 K, the units  32 Y,  32 M,  32 C, and  32 K, or the devices  34 Y,  34 M,  34 C, and  34 K. 
     [Ejection Unit  32 ] 
     Each ejection unit  32  has a function of forming an ink image of the associated color on a medium P being conveyed by the conveying unit  20  by electing ink droplets of the associated color toward the medium P. From another point of view, each ejection unit  32  has a function of ejecting ink droplets of the associated color toward a medium P being moved relative to the ejection unit  32  so that the droplets to constitute an ink image will land on the medium P. 
     Each ejection unit  32  is a member that is rectangular when viewed from the front side and extends a long distance in the device depth direction. Each ejection unit  32  is a line head (i.e., a head in which plural nozzles for ejecting droplets are arranged in the width direction of a medium P being conveved). For example, ink of the associated color of droplets to be ejected from each ejection unit  32  contains a solvent including water and a pigment (or dye) for producing the ink color. 
     [Irradiation Device  34 ] 
     Each irradiation device  34  has a function of irradiating, with light, an ink image that has been formed on a medium P by the corresponding ejection unit  32 . From another point of view, each irradiation device  34  has a function of irradiating, with light, droplets that have been ejected from the corresponding ejection unit  32  and have landed on a medium P. The irradiation devices  34 Y,  34 M,  34 C, and  34 K include irradiation units  36 Y,  36 M,  36 C, and  36 K and cover units  38 Y,  38 M,  38 C, and  38 K, respectively. In the following description, as for the irradiation units  36 Y,  36 M,  36 C, and  36 K and the corner units  38 Y,  38 M,  38 C, and  38 K, the alphabetical characters Y, M, C and K indicating the colors will be omitted if it is not necessary to discriminate between the units  36 Y,  36 M,  36 C, and  36 K or the units  38 Y,  38 M,  38 C, and  38 K. 
     In the exemplary embodiment, the irradiation device  34 Y is disposed downstream of the ejection unit  32 Y in the medium movement direction. The irradiation device  34 M is disposed downstream of the ejection unit  32 M and upstream of the ejection unit  32 Y in the medium movement direction. The irradiation device  34 C is disposed downstream of the ejection unit  32 C and upstream of the election unit  32 M in the medium movement direction. The irradiation device  34 K is disposed downstream of the ejection unit  32 K and upstream of the ejection unit  32 C in the medium movement direction. 
     (Irradiation Unit  36 ) 
     Each irradiation unit  36  is a member that is rectangular when viewed from the front side and extends a long distance in the device depth direction. Each irradiation unit  36  is configured so as to irradiate, with light, a medium P in the entire range in its width direction in which droplets ejected from the corresponding ejection unit  32  can land. More specifically, each irradiation unit  36  is disposed so as to form a gap G between itself and a medium P being conveyed (i.e., the movement path plane of a medium P) and to irradiate (the front surface of) a medium P with a rectangular light beam that is emitted from a light source (not shown) installed on a surface  36 A opposed to the medium P and is long in the medium width direction. 
     When droplets that have landed on a medium P are irradiated with light emitted from each irradiation unit  36 , the solvent contained in the droplets evaporates and the pigment (or dye) also contained in the droplets is fixed onto the medium P (i.e., an ink image is formed on the medium P). 
     (Cover Unit  38 ) 
     Each cover unit  38  has a function of suppressing a phenomenon that floating substances that flow into the gap G between the corresponding irradiation unit  36  and a medium P as the medium P is moved stick to the light source of the irradiation unit  36 . The term “floating substances” means foreign substances such as an ink mist that is produced when the ejection units  32  eject droplets and a paper powder produced from media P. 
     Each corner unit  38  includes a transparent belt BT, a first roll  50 , driven rolls  52  and  54 , a second roll  56 , and a drive source  58 . The transparent belt BT is an example of a transparent member, the first roll  50  is an example of a first rotary body, and the second roll  56  is an example of a second rotary body. The first roll  50 , the driven rolls  52  and  54 , and the second roll  56  are positioned with respect to the body of the droplets ejecting device  10  in a state that their axial directions are set parallel with the width direction of a medium P to be conveyed. 
     The lengths of the first roll  50 , the driven rolls  52  and  54 , and the second roll  56  and the width of the transparent belt BT are greater than the width (longitudinal length) of the irradiation unit  36  and stick out of both ends of the irradiation unit  36  in its longitudinal direction. In  FIG. 1 , the components of each of the cover units  38  other than the cover unit  38 K which is part the image forming unit  30 K are not given reference symbols. 
     The first roll  50  is disposed upstream, in the medium movement direction, of and above the corresponding irradiation unit  36 . The outer circumferential surface of the first roll  50  is wound with the transparent belt BT. The first roll  50  is rotatable about its axis. 
     The driven roll  52  is disposed upstream, in the medium movement direction, and below the corresponding irradiation unit  36  and above a medium P being conveyed. The driven roll  54  is disposed downstream, in the medium movement direction, of and below the corresponding irradiation unit  36  and above a medium P being conveyed. The outer circumferential surfaces of the driven rolls  52  and  54  are wound with the transparent belt BT. 
     The second roll  56  is disposed downstream, in the medium movement direction, of and above the corresponding irradiation unit  36 . One end of the transparent belt BT is fixe to the outer circumferential surface of the second roll  56 . The second roll  56  is rotated by the corresponding drive source  58  about its axis. 
     In each cover unit  38  having the above configuration, when the second roll  56  is rotated by the drive source  58 , the transparent belt BT is moved while it maintains a U shape that surrounds the corresponding irradiation unit  36  when viewed from the front side of the droplets ejecting device  10 . More specifically, a portion, paid out of the first roll  50 , of the transparent belt BT is moved through the gap G while being wound on the driven rolls  52  and  54  and opposed to the corresponding irradiation unit  36 , and is then taken up by the second roll  56 . In the exemplary embodiment each cover unit  38  is a replaceable component. 
     As described above, each irradiation unit  36  has a function of irradiating, with light, droplets that have been ejected from the corresponding ejection unit  32  and landed on a medium P. And each cover unit  38  has a function of suppressing a phenomenon that floating substances that flow into the gap G as a medium P is moved stick to the right source of the irradiation unit  36 . 
     [Controller  40 ] 
     The controller  40  has a function of controlling the devices and units (other than itself) that constitute the droplets ejecting device  10 . The function of the controller  40  will be described later in describing an image forming operation of the droplets ejecting device  10 . 
     &lt;Image Forming Operation&gt; 
     Next, an image forming operation of the droplets ejecting device  10  will be described with reference to  FIG. 1 . 
     Upon receiving job data from an external apparatus (not shown), the controller  40  puts the conveying unit  20  and the image forming device  30  into operation. More specifically, the controller  40  causes the conveying unit  20  to convey a medium P at a prescribed speed in the feeding direction. The controller  40  causes each ejection unit  32  to eject droplets of the associated color with timing to form an ink image of that color on the medium P by the ejection unit  32 . The controller  40  causes each irradiation unit  36  to irradiate, with light, the droplets that have been ejected from the corresponding ejection unit  32  and landed on the medium P. And the controller  40  causes the drive source  58  of each cover unit  38  to rotate the second roll  56  so that a portion of the transparent belt BT is paid out of the first roll  50  and then taken up by the second  56 . Thus, while each irradiation unit  36  is irradiating the droplets that have landed on the medium P with light, a portion of the corresponding transparent belt BT is moved through the gap G. 
     The image forming operation of the droplets ejecting device  10  according to the exemplary embodiment is finished after the medium P has passed the image forming unit  30 Y and the pigment (or dye) contained in the droplets of each color has been fixed on the medium P. 
     &lt;Advantages&gt; 
     Next, advantages of the exemplary embodiment, which are obtained because the irradiation unit  36  of each irradiation device  34  is equipped with the transparent belt BT which is moved through the gap G between the irradiation unit  36  and a medium P being conveyed, will be described by comparing the exemplary embodiment with a comparative mode. The comparative mode will be described using components etc. (i.e., their names and reference symbols) of the exemplary embodiment though no drawings will be used for the description of the comparative mode. 
     In the comparative mode, each irradiation device (not shown) is equipped with a transparent plate (transparent member) in place of the cover unit  38 . The transparent plate is disposed in the gap G and occupies the entire range of the irradiation unit  36  in a top view, and fixed to the irradiation unit  36 . The comparative mode is the same as the exemplary embodiment in configuration except for the above. 
     If an image forming operation is performed using the droplets electing device of the comparative mode, floating substances that flow into the gap G as a medium P is moved stick to the transparent plate. Light that is emitted from the irradiation unit  36  and reaches floating-substance-stuck portions of the transparent plate are scattered, reflected, or influenced otherwise by the floating substances. As a result, variations occur in the quantity of light that reaches the irradiation area of the medium P (i.e., the entire range in which droplets elected from the ejection unit  32  can land) due to the floating substances stuck to the transparent plate (occurrence of a light transmission failure). As a result, the amount of evaporation of the solvent, contained in part of the droplets that have landed on the medium P is decreased to produce image specks (image formation failure). The image formation failure becomes more noticeable as the period of use of the droplets ejecting device becomes longer. 
     In contrast, in the exemplary embodiment, since each irradiation device  34  is equipped with the transparent belt BT which is moved through the gap G between the irradiation unit  36  and a medium P being conveyed, a new portion (i.e., a portion that has not been moved through the gap G) of the transparent belt BT is paid out of the first roll  50  and placed in the gap G. Floating substances that have stuck to a portion the transparent belt BT in the gap G are moved together with that portion of the trans parent belt BT and put into the second roll  56 . 
     As described above, in each irradiation device  34  according to the exemplary embodiment, a new portion of the transparent belt BT is placed in the gap G because of a movement of the transparent belt BT. As a result, in each irradiation device  34  according to the exemplary embodiment, the amount of substances that stick to a portion, placed in the gap G between the irradiation unit  36  and a medium P, of the transparent belt BT is smaller than in the comparative mode in which the transparent member disposed in the gap G is not moved. Thus, in the droplets ejecting device  10  according to the exemplary embodiment, the probability of occurrence of a light transmission failure is much lower than in the comparative mode in which the transparent member placed the gap G is not moved. 
     Exemplary Embodiment 2 
     A second exemplary embodiment of the invention will described below with reference to  FIG. 2 . Only differences from the first exemplary embodiment will be described below. The second exemplary embodiment will be described using components etc. (i.e., their names and reference symbols) of the first exemplary embodiment. 
     &lt;Configuration&gt; 
     A droplets ejecting device  10 A shown in  FIG. 2  according to the second exemplary embodiment is different from the droplets ejecting device  10  according to the first exemplary embodiment in the configuration of cover units  38 Y 1 ,  38 M 1 ,  38 C 1 , and  38 K 1 . More specifically, in this exemplary embodiment, a transparent belt BT 1 , which is an example of the transparent member, is an endless belt. In the exemplary embodiment, a driven roll  50 A is provided in place of the first roll  50  and a drive roll  56 A is provided in place of the second roll  56 . The transparent belt BT 1  is wound on the driven rolls  50 A,  52 ,  54 , and the drive roll  56 A, and circulates counterclockwise (when the droplets ejecting vice  10 A is viewed from the front side) as the drive roll  56 A is rotated by the drive source  58 . The drive roll  56 A is an example of a circulation causing member. 
     Each irradiation device  34  (the droplets ejecting device  10 A) according to the exemplary embodiment is equipped with a blade BL which is in contact with the outer circumferential surface of the transparent belt BT 1  on the opposite side of the transparent belt BT 1  to the drive roll  56 A and thereby removes substances sticking to the outer circumferential surface of the transparent belt BT 1 . The blade BL is an example of a removing member. The second exemplary embodiment is the same in configuration as the first exemplary embodiment except for the above. 
     &lt;Image Forming Operation&gt; 
     In the exemplary embodiment, in an image forming operation, as the drive source  58  rotates the drive roll  56 A, the transparent belt BT 1  circulates while floating substances sticking to the outer circumferential surface of the transparent belt BT 1  are raked up by the blade BL. As a result, a portion, having been moved through the gap G (i.e., passed the irradiation unit  36 ), of the transparent belt BT 1  is subjected to removal of floating substances by the blade BL (resetting of the state that floating substances are stuck to its outer circumferential surface is reset), and is then moved through the gap G again. The image forming operation of the second exemplary embodiment is the same as that of the first exemplary embodiment except for the above. 
     &lt;Advantages&gt; 
     The second exemplary embodiment is different from the first exemplary embodiment in that the transparent belt BT 1  circulates while floating substances that have been stuck to it in the gap G are raked up by the blade BL. The cover units  38 Y 1 ,  38 M 1 ,  38 C 1 , and  38 K 1  (irradiation devices  34 Y,  34 M,  34 C, and  34 K) are longer in device life (i.e., replacement interval) than in the case that a portion, having been moved through the gap G between the irradiation unit  36  and a medium P, of the transparent belt BT is taken up rather than circulated. Furthermore, it can be said that in each irradiation device  34  according to the second exemplary embodiment, the amount of substances sticking to a portion, placed in the gap G, of the transparent belt BT 1  is smaller than in a case that a transparent member that is disposed in the gap G as in the above-described comparator mode is not moved relative to the irradiation unit  36 . 
     Although the invention has been described above in the form of the particular exemplary embodiments, the invention is not limited to those exemplary embodiments. For example, the technical scope of the inventions encompasses the following modes. 
     In the first exemplary embodiment, the transparent belt BT is paid out of the first roll  50  and taken up by the second roll  56 , the first roll  50  is disposed upstream of the irradiation unit  36  in the medium movement direction, and the second roll  56  is disposed downstream of the irradiation unit  36  in the medium movement direction. However, the positions of the first roll  50  and the second roll  56  may be interchanged. In this case, the first roll  50  is an example of the second rotary body and the second roll  56  is an example of the first rotary body. 
     In each exemplary embodiment, as shown in  FIGS. 1 and 2 , each irradiation device  34  for irradiating, with light, droplets that have been ejected from the corresponding ejection unit  32  and landed on a medium P is disposed downstream of the election unit  32  in the medium movement direction. However, as in a droplets ejecting device  10 B according to a first modification shown in  FIG. 3 , a final image may be formed in such a manner that a single irradiation device  34  that is disposed downstream of all of the ejection units  32  in the medium movement direction irradiates, with light, sets of droplets of the respective colors that have been ejected from the plural ejection units  32 . 
     Although the irradiation device  34  according to the first modification corresponds to each irradiation device  34  according to the first exemplary embodiment (see  FIG. 1 ), another irradiation device  34  according to the first modification is possible that corresponds to each irradiation device  34  according to the second exemplary embodiment (see  FIG. 2 ). Furthermore, a droplets ejecting device having only one ejection unit  32  (e.g., monochrome machine) is possible. 
     In each exemplary embodiment, as shown in  FIGS. 1 and 2 , each irradiation device  34  for irradiating, with light, droplets that have been ejected from the corresponding ejection unit  32  and landed on a medium P is disposed downstream of the ejection unit  32  in the medium movement direction and the cover unit  38  is driven by the drive source  58 . However, as shown in  FIG. 4 , a droplets ejecting device  10 C according to a second modification is possible in which a transparent belt BT is paid out of a first roll  50  is moved through the gaps G adjacent to all of the irradiation units  36  and then taken up by a second roll  56 . 
     More specifically, one of the first roll  50  and the second roll  56  disposed upstream of the irradiation unit  36 K which is located most upstream in the medium movement direction among all of the irradiation units  36  and the other is disposed downstream of the irradiation unit  36 Y which is located motif downstream in the medium movement direction. The second roll  56  takes up a portion, having been moved through the respective gaps G adjacent to call of the irradiation units  36 , of the transparent belt BT. 
     In the second modification, a blade BL for removing substances sticking to the outer circumferential surface of the transparent belt BT is disposed between the image forming units  30 Y and  30 M, between the image forming units  30 M and  30 C, and between the image forming units  30 C and  30 K. 
     In the second modification, the number of components is smaller (one drive source  58 ) than in the case that one cover unit  38  is provided for each ejection unit  32  (e.g., four drive sources  58 ). 
     Another configuration is possible in which one irradiation device  34  is provided for the ejection units  32 Y,  32 M, and  32 C each of which ejects color droplets and another irradiation device  34  is provided for the ejection units  32 K which ejects black droplets. 
       FIG. 5  shows a droplets ejecting device  100  according to a third modification which is a combination of the concept of the second exemplary embodiment that the endless transparent belt BT 1  is circulated (see  FIG. 2 ) and the concept of the second modification that the transparent belt BT is moved by the single drive source  58  (see  FIG. 4 ). More specifically, a drive roll  56 A circulates a transparent belt BT 1  along a circulation path including, as its portions, the respective gaps G adjacent to all of the irradiation units  36 . In the third modification, the number of components is smaller than in the case that the transparent belt BT 1  is a circulated for each irradiation unit  36 . 
     The droplets ejecting device  10  and  10 A according to the exemplary embodiments (see  FIGS. 1 and 2 ) and the droplets ejecting device  10 B,  10 C, and  10 D according to the modifications (see  FIGS. 3, 4, and 5 ) are line head type inkjet devices in which each ejection unit  32  is a line head. On the other hand,  FIG. 6  shows a droplets ejecting device  10 E according to a fourth modification which is what is called a serial head type inkjet device and in which a final image is formed by reciprocating a serial head type image forming device  30  (ejection units  32  and an irradiation device  34 ) in the direction (indicated by arrow B in  FIG. 6 ) that is perpendicular to the medium movement direction. 
     Each exemplary embodiment employs inks each of which contains, for example, a solvent including water and a pigment (or dye) for producing an ink color. However, an ink jet device is possible that employs different kinds of inks than employed in the exemplary embodiments as long as each ejection unit  32  forms a final image by ejecting droplets toward a medium P being moved relative to the ejection unit  32  and irradiating, with light, droplets that are stuck to the medium P. For example, the inks may be what is called ultraviolet-curing inks. 
     The type of light with which to irradiate droplets that are stuck to a medium P may be selected (or set) according to an ink used. For example, infrared light is suitable for droplets of a water-based ink and ultraviolet light is suitable for droplets of an ultraviolet-curing ink.