Patent Publication Number: US-2015077494-A1

Title: Image forming apparatus and separation member

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application is based on and claims priority pursuant to 35 U.S.C. §119(a) to Japanese Patent Application Nos. 2013-190720, filed on Sep. 13, 2013, and 2014-115199, filed on Jun. 3, 2014, in the Japan Patent Office, the entire disclosure of each of which is incorporated by reference herein. 
     BACKGROUND 
     1. Technical Field 
     Embodiments of the present disclosure relate to an image forming apparatus and a separation member. 
     2. Description of the Related Art 
     Image forming apparatuses are used as printers, facsimile machines, copiers, plotters, or multi-functional devices having, e.g., two or more of the foregoing capabilities. As one type of image forming apparatuses, for example, an image forming apparatus, such as a label printer, is known that prints a rolled printing medium having an adhesive face on which a separation sheet is attached (hereinafter, also referred to as “linerless label sheet”), such as a label sheet having no tape or mount sheet, and cuts the printing medium to a desired length after printing to form a printing medium piece (hereinafter, “label piece”). 
     In such an image forming apparatus, for example, the printing medium is conveyed with the adhesive face of the printing medium protected by a belt member. In such a case, the printing medium needs to be reliably separated from the belt member. 
     The printing medium is separated from the belt member by, typically, curvature separation or a separation member, such as a separation claw. For example, such a belt member may include multiple belt segments and separation assist members between the multiple belt segments. 
     As described above, for a configuration in which a printing medium is separated with a separation member, there is a demand for stably and reliably separating the printing medium even if the printing medium is, e.g., a linerless label sheet having low stiffness. 
     BRIEF SUMMARY 
     In at least one embodiment of this disclosure, there is provided an image forming apparatus including an image forming device, a conveyor, and a separation unit. The image forming device forms an image on a printing medium. The conveyor includes a belt to convey the printing medium. The separation unit separates the printing medium from the belt. The separation unit includes a claw portion and a first wing and a second wing. The claw portion contacts the belt. The first wing and the second wing are disposed at both sides of the claw portion in a direction perpendicular to a conveyance direction of the printing medium. Each of the first wing and the second wing has a guide face to guide the printing medium. The guide face is a sloped face that slopes downward in a direction away from the claw portion with respect to the direction perpendicular to the conveyance direction of the printing medium. Each of the first wing and the second wing has an upstream end in the conveyance direction that recedes toward a downstream side in the conveyance direction. 
     In at least one embodiment of this disclosure, there is provided a separation member for separating a printing medium from a belt. The separation member includes a claw portion and a first wing and a second wing. The claw portion contacts the belt. The first wing and the second wing are disposed at both sides of the claw portion in a direction perpendicular to a conveyance direction of the printing medium. Each of the first wing and the second wing has a guide face to guide the printing medium. The guide face is a sloped face that slopes downward in a direction away from the claw portion with respect to the direction perpendicular to the conveyance direction of the printing medium. Each of the first wing and the second wing has an upstream end in the conveyance direction that recedes toward a downstream side in the conveyance direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The aforementioned and other aspects, features, and advantages of the present disclosure would be better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
         FIG. 1  is a front view of a mechanical section of an image forming apparatus according to an embodiment of this disclosure. 
         FIG. 2  is a partial front view of the mechanical section of  FIG. 1  with a printing medium; 
         FIG. 3  is a partial perspective view of a separation unit serving as a separation assembly of the image forming apparatus illustrated in  FIG. 1 ; 
         FIG. 4  is a front view of the separation unit illustrated in  FIG. 3 ; 
         FIG. 5  is a perspective view of a separation member according to an embodiment of this disclosure; 
         FIG. 6  is an enlarged perspective view of a part of the separation member illustrated in  FIG. 5 ; 
         FIG. 7  is a plan view of the separation member illustrated in  FIG. 5 ; 
         FIG. 8A  is a partial sectional view of the separation member cut along line A-A in  FIG. 7 . 
         FIG. 8B  is a partial sectional view of the separation member cut along line B-B in  FIG. 7 ; 
         FIG. 8C  is a partial sectional view of the separation member cut along line C-C in  FIG. 7 ; 
         FIGS. 9A and 9B  are plan views of a separation member according to an embodiment of this disclosure; 
         FIGS. 10A and 10B  are plan views of a separation member according to an embodiment of this disclosure; 
         FIG. 11  is a partial plan view of a separation unit according to an embodiment of this disclosure; 
         FIG. 12  is a partial plan view of a separation unit according to an embodiment of this disclosure; 
         FIG. 13  is a partial plan view of a separation unit according to an embodiment of this disclosure; 
         FIG. 14  is a partial perspective view of the separation unit illustrated in  FIG. 13 ; 
         FIG. 15  is a partial plan view of a separation unit according to an embodiment of this disclosure; and 
         FIG. 16  is a partial plan view of a separation unit according to an embodiment of this disclosure. 
     
    
    
     The accompanying drawings are intended to depict embodiments of the present disclosure and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. 
     DETAILED DESCRIPTION OF EMBODIMENTS 
     In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this patent specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner and achieve similar results. 
     For example, in this disclosure, the term “image formation” used herein includes providing not only meaningful images, such as characters and figures, but meaningless images, such as patterns, to e (in other words, the term “image formation” also includes causing liquid droplets to land on printing media). 
     The term “ink” is not limited to “ink” in a narrow sense, unless specified, but is used as a generic term for any types of liquid usable as targets of image formation. For example, the term “ink” includes recording liquid, fixing solution, liquid, and so on. 
     The term “image forming apparatus”, unless specified, also includes both serial-type image forming apparatus and line-type image forming apparatus. 
     Although the embodiments are described with technical limitations with reference to the attached drawings, such description is not intended to limit the scope of the disclosure and all of the components or elements described in the embodiments of this disclosure are not necessarily indispensable. 
     Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, embodiments of the present disclosure are described below. 
     First, an image forming apparatus according to an embodiment of this disclosure is described with reference to  FIGS. 1 and 2 . 
       FIG. 1  is a front view of a mechanical section of an image forming apparatus according to an embodiment of this disclosure.  FIG. 2  is a partial front view of the mechanical section with a printing medium. 
     As illustrated in  FIG. 1 , an image forming apparatus  1000  according to this embodiment has a sheet feeding unit  101  serving as a sheet feeder, an image forming unit  102  as an image forming device, a conveyance unit  103  as a conveyor, and a discharge conveyance unit  104  as a discharge conveyor within an apparatus body  100 . The image forming apparatus  1000  also has a discharge port  105  and a guide unit  106 . The discharge port  105  serves as a discharge port part to discharge a printing medium  2  having an image formed thereof to the outside of the apparatus body  100 . The guide unit  106  guides a rolled printing medium  2  during conveyance and pull-back of the printing medium  2 . 
     A media roll  4  formed of the rolled printing medium  2  is loaded on the sheet feeding unit  101 . 
     As illustrated in  FIG. 2 , the printing medium  2  is a continuum having an image-formable medium (hereinafter, also referred to as “printing face”)  2   a  and an adhesive layer (hereinafter, referred to as “adhesive face”)  2   b  formed on a surface of the image-formable medium  2   a . The printing medium  2  is a linerless label sheet rolled around in a state in which a mount sheet (separation sheet or separator) is not adhered to the adhesive face  2   b.    
     The media roll  4  is engaged with a spool  5 . Each of opposed ends of the spool  5  is rotatably held at three points, i.e., by a first roller  111 , a second roller  112 , and a third roller  113  serving as a first rotary body, a second rotary body, and a third rotary body, respectively. 
     The term “spool” used herein is not limited to a member that is provided separately from a core member and engaged with the core member for use. The spool may be held by roll holder members  6  as an integral part of the core member of the media roll  4 . In a case in which the core member of the media roll  4  is directly held, the term “spool” includes the core member. 
     The image forming unit  102  includes a recording head  11  and a carriage  12 . The recording head  11  is a liquid ejection head mounted on the carriage  12  to eject droplets onto a printing medium  2 . The carriage  12  is supported by guide members  13  and  14  so as to be reciprocally movable along a direction (main scanning direction) perpendicular to a conveyance direction of the printing medium  2  indicated by arrow D in  FIG. 1 . 
     For this embodiment, a liquid ejection head having two nozzle rows is used as the recording head  11 , and the carriage  12  mounts two recording heads  11 . The two recording heads  11  eject ink droplets of, for example, black (K), cyan (C), magenta (M), and yellow (Y) from four nozzle rows. It is to be noted that the configuration of the recording head is not limited to the above-described configuration but may be other type of recording head, for example, a line-type recording head. 
     Ink cartridges  15  storing respective color inks are mounted to the apparatus body  100  in a replaceable manner. The color inks are supplied from the ink cartridges  15  to via supply tubes  16  to head tanks mounted on the carriage  12 , and further supplied from the head tanks to the recording heads  11 . 
     The image forming apparatus  1000  also has a waste liquid tank  17  mounted to the apparatus body  100  in a replaceable manner. For example, in a maintenance operation for maintaining and recovering the performance of the recording heads  11 , waste ink is discharged into and stored in the waste liquid tank  17 . 
     The image forming unit  102  is not limited to the above-described liquid ejection head but may be any other type of image forming unit to form an image in a contact or non-contact manner. 
     The conveyance unit  103  includes a protection belt  21  serving as an endless conveyance belt. The protection belt  21  is dispose below the recording heads  11 . The protection belt  21  is looped around a conveyance roller  22  and a tensioned driven roller  23  so as to circulate. 
     The protection belt  21  preferably has no adhesion to the adhesive face  2   b . However, to prevent the printing medium  21  from floating up from the protection belt  21  during conveyance, the protection belt  21  may have such low adhesion to the adhesive face  2   b  that the protection belt  21  is separatable from the adhesive face  2   b . Pressing the protection belt  21  against the adhesive face  2   b  allows protection of the adhesive face  2   b  and prevents the adhesive face  2   b  from contacting components inside the image forming apparatus to allow stable conveyance of the printing medium  2 . In addition, since the protection belt  21  is separatable from the adhesive face  2   b , the printing medium  2  separated from the protection belt  21  is discharged from the discharge port  105 . 
     In other words, in this embodiment, the protection belt  21  protects the adhesive face  2   b  of the printing medium  2  and is transported together with the printing medium  2 . 
     An opposing roller  24  is disposed opposing the conveyance roller  22 . A conveyance roller pair (in this embodiment, pair of rotary bodies) of the conveyance roller  22  and the opposing roller  24  constitutes a conveyor to sandwich the printing medium  2  and the protection belt  21  together and convey the printing medium  2  to an image forming region of the recording heads  11 . 
     The protection belt  21  has multiple holes. Within a loop formed by the protection belt  21 , a suction fan  27  is disposed opposing the recording heads  11  of the image forming unit  102 . The suction fan  27  sucks the printing medium  2  toward a surface of the protection belt  21  via the suction holes. 
     In this embodiment, the printing medium  2  is adhered to the protection belt  21  by suction. However, it is to be noted that the force for adhering the printing medium  2  onto the protection belt  21  is not limited to suction force and may be, for example, electrostatic force. Alternatively, the printing medium  2  may be secured by adhesiveness of the adhesive face  2   b  so as not to float from the protection belt  21 . 
     In addition, spur roller units  28   a ,  28   b , and  28   c  are disposed near the driven roller  23 . Each of the spur roller units  28   a ,  28   b , and  28   c  has multiple spur rollers arranged in the direction perpendicular to the conveyance direction D. The upstream spur roller units  28   a  and  28   b  are disposed opposing the protection belt  21 , and the most downstream spur roller unit  28   c  is disposed opposing a receive member  30  of the discharge conveyance unit  104 . 
     A separation unit  71  is disposed downstream from the driven roller  23  to separate the printing medium  2  from the protection belt  21 . The separation unit  71  includes a plurality of separation members  72  arranged side by side in an axial direction thereof. 
     The receive member  30  guides the printing medium  2  fed from between the protection belt  21  and the spur roller unit  28   b . The discharge conveyance unit  104  has a cutter unit  31  serving as a cutting device to cut a printing medium  2  into a desired length to form a printing medium piece (label piece)  200 . The discharge conveyance unit  104  is disposed downstream from the receive member  30  in the conveyance direction D of the printing medium  2 . 
     The cutter unit  31  includes a lower blade  31   b  and a cutting blade (upper blade or cutter)  31   a . The lower blade  31   b  is formed at a downstream edge surface of the receive member  30 . The cutter  31   a  cuts the printing medium  2  between the lower blade  31   b  and the cutter  31   a . The cutter  31   a  is moved in the direction perpendicular to the conveyance direction D to cut the printing medium  2 . 
     A discharge roller  32  is disposed downstream from the cutter unit  31 . A spur roller  33  is disposed opposing the discharge roller  32 . The discharge roller  32  and the spur roller  33  hold the label piece  200 , which is cut by the cutter unit  31 , in a state in which a leading end of the label piece  200  is sent out to the discharge port  105  serving as a discharge port part of the apparatus body  100 . 
     In this embodiment, a surface of the discharge roller  32  to hold the label piece  200  is, for example, non-adherence processed (processed so that the adhesive surface  2   b  does not adhere to the surface of the discharge roller  32 ), thus allowing separation of the adhesive surface  2   b  of the label piece  200 . In some embodiments, the discharge roller  32  itself may be made of a material allowing separation of the adhesive surface  2   b  of the label piece  200 . 
     A sheet sensor  34  is disposed to detect presence or absence of a printing medium  2 . The sheet sensor  34  is constituted of, for example, a photosensor or a combination of a mechanical lever and a photosensor. 
     On a downstream side of the opposing roller  24  also serving as the first roller constituting the conveyance unit  103 , the guide unit  106  has a second roller  42  serving as a separation roller disposed upstream from the image forming unit  102  and a third roller  43  disposed opposing the second roller  42  via the opposing roller  24 . An endless guide belt  44  is looped around the opposing roller  24 , the second roller  42 , and the third roller  43 . 
     The guide belt  44  is a belt member having a base member made of, e.g., polyimide and a release layer (e.g., silicone coating) as a surface layer to enhance the release performance of the guide belt  44 . 
     The opposing roller  24 , the second roller  42 , and the third roller  43  are rotatably held by a holder member  45 . The holder member  45  is rotatable around a shaft  46  and is displaceable between at a position at the opposing roller  24  opposes the conveyance roller  22  and a position at which the opposing roller  24  separates from the conveyance roller  22  to open a space between the opposing roller  24  and the conveyance roller  22 . 
     When the media roll  4  is loaded and the printing medium  2  is set on the protection belt  21 , the space between the opposing roller  24  and the conveyance roller  22  is opened. When the printing medium  2  is conveyed, the opposing roller  24  is pressed toward the conveyance roller  22 . Accordingly, the opposing roller  24  is pressed toward the conveyance roller  22  by a pressing unit, such as a spring. In addition, the second roller  42  is pressed toward the protection belt  21  by a pressing unit, such as a spring. 
     In this embodiment, as described above, the printing medium  2  is placed on the protection belt  21  with the adhesive face  2   b  facing the protection belt  21 , to perform image formation. Alternatively, a configuration may be employed in which an image is formed on the adhesive face  2   b  of the printing medium  2 . In such a case, a surface of the guide belt  44  is preferably non-adherence processed (to prevent the adhesive face  2   b  from adhering thereto). 
     For the image forming apparatus  1000  having such a configuration, the protection belt  21  and the printing medium  2  pulled out from the media roll  4  loaded on the sheet feeding unit  101  are sandwiched together between the conveyance roller  22  and the opposing roller  24 . 
     When the conveyance roller  22  is rotated, the printing medium  2   b  and the protection belt  21  are conveyed together in a state in which the adhesive face  2   b  is protected by the protection belt  21 . A desired image is formed on the printing medium  2  by the recording heads  11  of the image forming unit  102 . 
     When the protection belt  21  is separated from the printing medium  2  having the image formed thereon, the printing medium  2  is conveyed to the discharge conveyance unit  104  and cut at a desired position by the cutter unit  31  to form a label piece  200 . The label piece  200  is held between the discharge roller  32  and the spur rollers  33  in a state in which the label piece  200  is extractable from the discharge port  105  of the apparatus body  100 . 
     The guide unit  106  also prevents the printing medium  2  from being reeled by the opposing roller  24  during conveyance and pull-back of the printing medium  2 , in particular, when an image is formed on the adhesive face  2   b  of the printing medium  2 . 
     In other words, even if the surface of the opposing roller  24  is non-adherence processed, the adhesive face  2   b  of the printing medium  2  might adhere to the circumferential surface of the opposing roller  24  and be reeled by the opposing roller  24  due to a small curvature of the opposing roller  24 . In such a case, it is conceivable to use a larger curvature of the opposing roller  24 . However, a larger curvature of the opposing roller  24  reduces the size of a nip area between the opposing roller  24  and the conveyance roller  22 , thus preventing obtainment of stable conveyance force. 
     Hence, during conveyance, the printing medium  2  is conveyed while being pressed by the guide belt  44 , and the guide belt  44  is reliably separated from the printing medium  2  by the second roller  42  serving as a separation roller having a large curvature, thus preventing the printing medium  2  from being reeled by the opposing roller  24  during conveyance. 
     When the printing medium  2  is pulled back, the guide belt  44  receives the adhesive face  2   b  of the printing medium  2 , thus preventing the printing medium  2  from being reeled by the opposing roller  24 . 
     When image formation is finished and the printing medium  2  is cut by the cutter unit  31 , the leading end of the printing medium  2  is at the position of the cutter unit  31  and an area of the printing medium  2  opposite the image forming unit  102  is an unused area. In such a state, if the next image forming operation is resumed, the unused area of the printing medium  2  is wasted. Hence, in this embodiment, the printing medium  2  is pulled back in a pull-back direction (opposite the conveyance direction of the printing medium  2 ) to a position at which the leading end of the printing medium  2  is placed upstream from the image forming unit  102  in the conveyance direction. 
     Next, a separation unit serving as a separation assembly of the image forming apparatus according to an embodiment of this disclosure is described with reference to  FIGS. 3 and 4 . 
       FIG. 3  is a partial perspective view of the separation unit according to this embodiment.  FIG. 4  is a front view of the separation unit according to this embodiment. 
     The separation unit (separation assembly)  71  includes a plurality of separation members  72  and a shaft  73  to support the separation members  72 . The separation members  72  separate a printing medium  2  from the protection belt  21  and guide the printing medium  2  in an area downstream from the driven roller  23  in the medium conveyance direction D. The separation members  72  are arranged side by side in a direction perpendicular to the medium conveyance direction D. 
     Here, separation members according to an embodiment of this disclosure is described with reference to  FIGS. 5 to 7 . 
       FIG. 5  is a perspective view of a separation member according to this embodiment  FIG. 6  is an enlarged perspective view of a part of the separation member illustrated in  FIG. 5 .  FIG. 7  is a plan view of the separation member illustrated in  FIG. 5 .  FIG. 8A  is a partial sectional view of the separation member cut along line A-A in  FIG. 7 .  FIG. 8B  is a partial sectional view of the separation member cut along line B-B in  FIG. 7 .  FIG. 8C  is a partial sectional view of the separation member cut along line C-C in  FIG. 7 . 
     It is to be noted that Y direction represents a direction parallel to the medium conveyance direction, X direction represents a direction perpendicular to the medium conveyance direction, and Z direction represents a height direction. 
     The separation member  72  includes a claw portion  170  to contact the protection belt  21 , and a first wing  171  and a second wing  172  disposed at both sides of the claw portion  170  in the X direction perpendicular to the medium conveyance direction. The first wing  171  and the second wing  172  have a guide face  171   a  and a guide face  172   a , respectively, to guide the printing medium  2 . Each of the guide face  171   a  and the guide face  172   a  has a sloped shape. The claw portion  170 , the first wing  171 , and the second wing  172  are integrally molded as a single member. 
     Here, each of the guide face  171   a  and the guide face  172   a  is a sloped face that slopes downward in a direction away from the claw portion  170  in the X direction perpendicular to the medium conveyance direction. 
     Each of the guide face  171   a  and the guide face  172   a  is also a sloped face that slopes upward in a downstream direction from a tip  170   a  of the claw portion  170  so as to approach an upper surface of the claw portion  170 . 
     In a plan view, as illustrated in  FIG. 7 , each of the guide face  171   a  and the guide face  172   a  is a sloped face in which upstream ends  171   b  and  172   b  in the medium conveyance direction recede toward a downstream side in the medium conveyance direction (Y direction), in other words, go farther away from the tip  170   a  of the claw portion  170  in the medium conveyance direction. 
     In  FIG. 6 , each of the guide face  171   a  and the guide face  171   a  slopes downward in X-Z plane in a direction away from the claw portion  170 . 
     Since the upstream ends  171   b  and  172   b  recede toward the downstream side in the medium conveyance direction (Y direction), each of the guide face  171   a  and the guide face  172   a  slopes downward along a circumferential surface of the protection belt  21  (a circumferential surface of the driven roller  23 ). 
     In Y-Z plane, each of the guide face  171   a  and the guide face  172   a  also slopes upward in a downstream direction in the medium conveyance direction so as to approach the upper surface of the claw portion  170 . 
     By contrast, the claw portion  170  has such a shape that only the tip  170   a  contacts the surface of the protection belt  21 . 
     For the separation member  72  having the above-described configuration, immediately after the printing medium  2  is separated from the protection belt  21  by the tip  170   a  of the claw portion  170 , slopes of the guide face  171   a  and the guide face  172   a  relative to the X-Z plane allow the back face (adhesive face  2   b ) of the printing medium  2  to be gradually supported outward from the vicinity of the claw portion  170 . Such a configuration allows even the printing medium  2  having the adhesive face  2   b  to be separated from the protection belt  21 . 
     For a configuration without the first wing  171  and the second wing  172 , a portion of the printing medium  2  corresponding to the claw portion  170  is separated from the protection belt  21  at an exit of the protection belt  21 . However, because of adhesiveness of the adhesive face  2   b , areas of the printing medium  2  at both sides of the portion corresponding the claw portion  170  may be conveyed in a state in which the areas of the printing medium  2  adhere to the protection belt  21 . As a result, the printing medium  2  may not be separated from the protection belt  21 , thus causing a conveyance failure. Such a failure is likely to occur in, for example, a mountless label having low stiffness (linerless label sheet). 
     In addition, for the configuration without the first wing  171  and the second wing  172 , the printing medium  2  is not gradually separated from the protection belt  21  at both sides of the claw portion  170 . As a result, when the printing medium  2  adhering to the protection belt  21  arrives at the first wing  171  and the second wing  172 , conveyance load rapidly may increase, thus hampering uniform feeding of the printing medium  2 . In addition, the printing medium  2  contacts the protection belt  21  at an increased width, thus hampering smooth separation. 
     In addition, slopes of the guide face  171   a  and the guide face  172   a  (increasing in height toward the downstream side) relative to the Y-Z plane can suppress waving of the printing medium  2  separated from the protection belt  21  and feed the printing medium  2  to downstream processes (e.g., cutting process and discharge process) with a surface of the printing medium  2  maintained substantially flat. In other words, when the printing medium  2  is separated from the protection belt  21 , slopes of the guide face  171   a  and the guide face  172   a  relative to the X-Z plane allow gradual separation of the printing medium  2  from the protection belt  21  with time lags. After the printing medium  2  passes the separation member  72 , the slopes relative to the Y-Z plane allow the printing medium  2  to be conveyed in a substantially flat state. 
     By contrast, for a configuration without the slopes relative to the Y-Z plane, when the printing medium  2  is separated from the tip  170   a  of the claw portion  170 , the guide face  171   a , and the guide face  172   a , waving of the printing medium  2  may occur (since the printing medium  2  is gradually separated with time lags by the slopes relative to the X-Z plane. As a result, when the printing medium  2  is relayed to downstream processes (e.g., cutting process and discharge process), a conveyance failure, such as a sheet jam, may occur. In particular, for a mountless label having low stiffness (linerless label sheet), such waving is likely to occur, thus causing a sheet jam. 
     In this embodiment, a step  173  is disposed between the claw portion  170  and each of the first wing  171  and the second wing  172 . For such a configuration, immediately after the printing medium  2  is separated from the protection belt  21 , the adhesive face  2   b  of the printing medium  2  contacts only the surface of the claw portion  170 . As a result, a contact area of the printing medium  2  with the separation member  72  decreases, thus reducing conveyance load. 
     The step  173  decreases in height toward the downstream side in the medium conveyance direction. For such a configuration, after the printing medium  2  passes the separation member  72 , the printing medium  2  is conveyed in a substantially flat state. 
     Hence, as described above, for the separation unit  71 , the separation members  72  are arranged side by side in the direction perpendicular to the medium conveyance direction. Such a configuration allows the printing medium  2  to be reliably separated from the protection belt  21  and fed to the downstream side in a less wavy state. 
     Contact faces of the separation member  72  with the printing medium  2 , for example, the surface of the claw portion  170 , the guide face  171   a  of the first wing  171 , and the guide face  172   a  of the second wing  172  are preferably non-adherence or unevenness processed. 
     Such a configuration reduces conveyance resistance of the printing medium  2 , thus allowing the printing medium  2  to be stably fed to the downstream side. 
     Next, separation members according to an embodiment of this disclosure is described with reference to  FIGS. 9A and 9B . 
       FIGS. 9A and 9B  are plan views of a separation member  72  according to this embodiment. 
     In this embodiment, as illustrated in  FIG. 9A , the separation member  72  includes three members: a member having a claw portion  170 , a member having a first wing  171 , and a member having a second wing  172 . 
     The three members are held by a shaft  73  equivalent to the shaft  73  illustrated in  FIG. 3  to have an arrangement illustrated in  FIG. 9B . Similarly with the above-described embodiment of  FIG. 3 , the arrangement illustrated in  FIG. 9B  is repeatedly arranged in the direction perpendicular to the medium conveyance direction. 
     Such a configuration can obtain operation effects equivalent to those of the above-described embodiment illustrated in  FIG. 3 . In addition, for this embodiment, each of the claw portion  170 , the first wing  171 , and the second wing  172  has a simple shape, thus facilitating highly precise processing. 
     Next, separation members according to an embodiment of this disclosure is described with reference to  FIGS. 10A and 10B . 
       FIGS. 10A and 10B  are plan views of separation members  72  according to this embodiment. 
     In this embodiment, as illustrated in  FIG. 10A , the separation member  72  is constituted of a single member in which a first wing  171  and a second wing  172  are arranged in this order from an end of the claw portion  170  in a direction perpendicular to the medium conveyance direction. 
     Multiple separation members  72  are repeatedly arranged and held by a shaft similar to the shaft  73  illustrated in  FIG. 3  so as to have an arrangement illustrated in  FIG. 10B . Thus, the first wing  171  and the second wing  172  are disposed at both sides of the claw portion  170 . 
     Such a configuration can obtain operation effects equivalent to those of the above-described embodiment illustrated in  FIG. 3 . 
     It is to be noted that the configuration of the separation member is not limited to the above-described embodiments. For example, the separation member may be a single member in which a second wing  172  and a first wing  171  may be arranged in this order from an end of the claw portion  170  in the direction perpendicular to the medium conveyance direction. 
     Alternatively, in an embodiment, a separation member may be constituted of two members: a single member including a claw portion  170  and a first wing  171  integrally molded and a member forming a second wing  172 . Alternatively, in an embodiment, a separation member may be constituted of two members: a single member including a claw portion  170  and a second wing  172  integrally molded and a member forming a first wing  171 . 
     Next, a separation unit according to an embodiment of this disclosure is described with reference to  FIG. 11 . 
       FIG. 11  is a partial plan view of a separation unit  71  according to this embodiment. 
     In this embodiment, the separation unit  71  includes two types of separation members  72 A and  72 B. Hereinafter, separation members  72 A and  72 B are collectively referred to as separation members  72  unless distinguished. In this embodiment, an end of the printing medium  2  is used as a reference position RP to convey the printing medium  2 . Hence, one of the separation members  72  closest to the reference position RP of the printing medium  2  is the separation member  72 A. Two or more of the separation members  72  arranged side by side in the direction perpendicular to the medium conveyance direction are the separation members  72 B. 
     The separation member  72 A includes a claw portion  170 A formed along a direction (indicated by arrow Y) parallel to the medium conveyance direction D in a plan view illustrated in  FIG. 11 . The claw portion  170 A has a rib shape and includes a tip  170   a  to contact a protection belt  21  and a downstream portion  170   b  from the tip  170   a  in the medium conveyance direction D to support conveyance of the printing medium  2  separated from the protection belt  21 . 
     Each of the separation members  72 B includes a claw portion  170 B in a direction (indicated by arrow S) tilted relative to the medium conveyance direction D in the plan view illustrated in  FIG. 11 . The claw portion  170 B has a rib shape and includes a tip  170   a  to contact the protection belt  21  and a downstream portion  170   b  from the tip  170   a  in the medium conveyance direction D to support conveyance of the printing medium  2  separated from the protection belt  21 . In other words, the claw portions  170  ( 170 B in this embodiment) in at least a part of the separation members  72  are tilted relative to the medium conveyance direction in the plan view. 
     In this embodiment, toward a downstream side in the medium conveyance direction D in the plan view, the claw portion  170 B of the separation member  72 B is tilted in a direction away from the reference position RP of the printing medium. 
     For such a configuration, when the printing medium  2  passes the separation members  72 A and  72 B, force acts on the printing medium  2  in the direction S from the claw portions  170 B of the separation members  72 B. In other words, the printing medium  2  receives spreading force from the tilt of the rib-shaped claw portions  170 B in the direction S relative to the medium conveyance direction D. 
     Such a configuration prevents occurrences of bending or paper wrinkles of the printing medium  2 , thus allowing stable conveyance. 
     Next, a separation unit according to an embodiment of this disclosure is described with reference to  FIG. 12 . 
       FIG. 12  is a partial plan view of a separation unit  71  according to this embodiment. 
     In this embodiment, the separation unit  71  includes three types of separation members  72 A,  72 B, and  72 C. Hereinafter, separation members  72 A,  72 B, and  72 C are collectively referred to as separation members  72  unless distinguished. In this embodiment, a middle portion of a printing medium  2  is used as a reference position RP to convey the printing medium  2 . Hence, one of the separation members  72  corresponding to the reference position RP of the printing medium  2  is the separation member  72 A. 
     Two or more of the separation members  72  arranged at the right side of the separation member  72 A in the direction perpendicular to the medium conveyance direction are the separation members  72 B. Two or more of the separation members  72  arranged at the left side of the separation member  72 A in the direction perpendicular to the medium conveyance direction are the separation members  72 C. 
     Similarly with the above-described embodiment illustrated in  FIG. 11 , the separation member  72 A includes a claw portion  170 A formed along a direction (indicated by arrow Y) parallel to the medium conveyance direction D in a plan view illustrated in  FIG. 12 . The claw portion  170 A has a rib shape and includes a tip  170   a  to contact a protection belt  21  and a downstream portion  170   b  from the tip  170   a  in the medium conveyance direction D to support conveyance of the printing medium  2  separated from the protection belt  21 . 
     Similarly with the above-described embodiment illustrated in  FIG. 11 , each of the separation members  72 B includes a claw portion  170 B in a direction (indicated by arrow T) tilted relative to the medium conveyance direction D in the plan view illustrated in  FIG. 12 . The claw portion  170 B has a rib shape and includes a tip  170   a  to contact the protection belt  21  and a downstream portion  170   b  from the tip  170   a  in the medium conveyance direction D to support conveyance of the printing medium  2  separated from the protection belt  21 . In this embodiment, toward a downstream side in the medium conveyance direction D in the plan view, the claw portion  170 B of the separation member  72 B is tilted in a rightward direction away from the reference position RP of the printing medium. 
     Each of the separation members  72 C includes a claw portion  170 C in a direction (indicated by arrow U) tilted relative to the medium conveyance direction D in the plan view illustrated in  FIG. 12 . The claw portion  170 C has a rib shape and includes a tip  170   a  to contact the protection belt  21  and a downstream portion  170   b  from the tip  170   a  in the medium conveyance direction D to support conveyance of the printing medium  2  separated from the protection belt  21 . In this embodiment, toward a downstream side in the medium conveyance direction D in the plan view, the claw portion  170 C of the separation member  72 C is tilted in a leftward direction away from the reference position RP of the printing medium. 
     For such a configuration, when the printing medium  2  passes the separation members  72 A,  72 B, and  72 C, force acts on the printing medium  2  in the direction T and the direction U from the claw portions  72 B and the claw portions  170 C, respectively. In other words, from the tilt of the rib-shaped claw portions  170 B and  170 C in the medium conveyance direction D, the printing medium  2  receives forces spreading leftward and rightward from the reference position RP. 
     Such a configuration prevents occurrences of bending or paper wrinkles of the printing medium  2 , thus allowing stable conveyance. 
     Next, a separation unit according to an embodiment of this disclosure is described with reference to  FIGS. 13 and 14 . 
       FIG. 13  is a partial plan view of a separation unit  71  according to this embodiment.  FIG. 14  is a partial perspective view of the separation unit  71  according to this embodiment. 
     In this embodiment, similarly with the above-described embodiment illustrated in  FIG. 11 , the separation unit  71  includes a separation member  72 A and two or more separation members  72 B. The separation member  72 A has a claw portion  170 A formed along the medium conveyance direction D. Each of the separation members  72 B has a claw portion  170 B tilted relative to the medium conveyance direction D in a plan view of  FIG. 13 . The separation member  72 A and the separation members  72 B are arranged side by side on a holder  203 . 
     Here, the separation members  72 B are rotatably arranged on the holder  203  in the plan view of  FIG. 13 . In the plan view, each of the rotatable separation members  72 B has a configuration (outer circumferential shape) in which an inscribed circle  300  around a rotation center RC thereof does not interfere with an inscribed circle of an adjacent separation member  72 B. 
     Thus, when the separation members  72 B are rotated, adjacent ones of the separation members  72 B do not interfere with each other, thus allowing the direction of the claw portion  170 B. 
     A rack  202  is disposed on the holder  203  so as to be reciprocally movable in a direction indicated by arrow M (in which the separation members  72 B are arranged side by side). The separation members  72 B are coupled to the rack  202 . The rack  202  is reciprocally moved by a motor  201  along the direction M. In this embodiment, all of the separation members  72 B are coupled to the rack  202  so as to be collectively rotated. 
     For such a configuration, in an initial state, as illustrated in  FIG. 13 , the separation members  72 B are arranged so that the claw portions  170 B are tilted in such a direction as to spread downward relative to the medium conveyance direction D. 
     Similarly with the above-described embodiment illustrated in  FIG. 12 , such a configuration prevents occurrences of bending or paper wrinkles of the printing medium  2 , thus allowing stable conveyance. 
     By contrast, when the printing medium  2  is wound back, the motor  201  moves the rack  202  to invert the tilt direction of the claw portion  170 B of each separation member  72 B. Thus, the claw portion  170 B is tilted in such a direction as to spread toward the upstream side with respect to the medium conveyance direction D. 
     Even when the printing medium  2  is wound back, such a configuration prevents occurrences of bending or paper wrinkles of the printing medium  2  passing on the separation members  72 , thus allowing stable conveyance. 
     In addition, in this embodiment, an elastic member  204 , such as a spring, is mounted on the holder  203  to apply force in a direction in which the holder  203  rotates around a rotation axis RA (a shaft  73 ). 
     Such a configuration allows the separation members  72  to be pressed against (contact) the conveyance belt  21  at a constant pressure (abutting pressure or contact pressure) regardless of a change in the axial position of the tension roller  23  due to, e.g., expansion and contraction of the conveyance belt  21 . 
     In this embodiment, as described above, the separation members  72 B having the tilted claw portion  170 B are rotatable. However, the configuration of the separation members  72  is not limited to the configuration of this embodiment. For example, instead of the separation members  72 B, separation members  72  having non-tilted claw portions  170  may be employed. (However, similarly with the separation members  72 B, the separation members  72  have such an outer circumferential shape that adjacent ones of the separation members  72  do not interfere with each other.) 
     In such a case, for rotatable ones of the separation members  72 , the separation members  72  are rotatable between a position at which the claw portions  170  are parallel to the medium conveyance direction D and a position at which the claw portions  170  are tilted relative to the medium conveyance direction D. Not only when the printing medium  2  is wound back but also when the printing medium  2  is fed, the direction of the claw portions  170  is adjustable in accordance with the printing medium  2  conveyed. 
     Next, a separation unit according to an embodiment of this disclosure is described with reference to  FIG. 1S . 
       FIG. 15  is a partial plan view of a separation unit  71  according to this embodiment. 
     In this embodiment, multiple separation members  72 B are divided to two groups: a first group  72 Ba and a second group  72 Bb. Separation members  72 B of the first group  72 Ba are coupled to a rack  202   a  and reciprocally moved by a motor  201   a . Separation members  72 B of the second group  72 Bb are coupled to a rack  202   b  and moved by a motor  201   b.    
     For such a configuration, the multiple separations members  72 B are divided into groups, and the direction of the claw portions  170 B is adjustable for each group. 
     Next, a separation unit according to an embodiment of this disclosure is described with reference to  FIG. 16 . 
       FIG. 16  is a partial plan view of a separation unit  71  according to this embodiment. 
     In this embodiment, the separation unit  71  includes a separation member  72 A and separation members  72 D. The separation members  72 D have a circular outer circumference in a plan view. As illustrated in  FIG. 16 , two or more of the separation members  72 D are arranged at each of the left side and the right side of the separation member  72 A disposed at a middle portion of the separation unit  71 . 
     Each of the separation members  72 D arranged at the right side of the separation member  72 A in a direction perpendicular to the medium conveyance direction D has a rib-shaped claw portion  170 D. The claw portion  170 D is coupled to a rack  202   c  in a state in which, toward a downstream side in the medium conveyance direction D, the claw portion  170 D is sloped in a rightward direction away from a reference position RP of the printing medium. 
     Each of the separation members  72 D arranged at the left side of the separation member  72 A in a direction perpendicular to the medium conveyance direction D has a rib-shaped claw portion  170 D. The claw portion  170 D is coupled to a rack  202   d  in a state in which, toward a downstream side in the medium conveyance direction D, the claw portion  170 D is sloped in a leftward direction away from the reference position RP of the printing medium. 
     The rack  202   c  and the rack  202   d  are reciprocally moved by a motor  201   c  and a motor  201   d  along a direction M1 and a direction M2, respectively. 
     Accordingly, when a printing medium conveyed based on a central reference position is wound back, the separation members  72 D can have different tilt directions between the left side and the right side of the separation member  72 A. Such a configuration prevents occurrences of bending or paper wrinkles of the printing medium  2 , thus allowing stable conveyance. 
     Numerous additional modifications and variations are possible in light of the above teachings. It is therefore to be understood that, within the scope of the above teachings, the present disclosure may be practiced otherwise than as specifically described herein. With some embodiments having thus been described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the scope of the present disclosure and appended claims, and all such modifications are intended to be included within the scope of the present disclosure and appended claims.