Patent Document

Priority is claimed under 35 U.S.C. §120 to U.S. patent application Ser. No. 13/541,953, which was filed on Jul. 5, 2012, which claims priority under 35 U.S.C. §120 to U.S. patent application Ser. No. 12/080,330, which was filed on Apr. 2, 2008, which claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2007-099886 filed Apr. 5, 2007, which are hereby incorporated herein by reference in their entireties. 
     BACKGROUND 
     The present invention relates to a medium transporting unit that transports a plate-like medium such as a CD or a DVD and a medium processing apparatus having the medium transporting unit. 
     BACKGROUND ART 
     In recent years, medium processing apparatuses such as disc dubbing apparatuses that record data on mediums such as plural blank CDs or DVDs and CD/DVD publishers that can produce and publish a medium by performing a data recording operation and a label printing operation were used. Such a kind of medium processing apparatus was known which has a drive for driving data on a medium, a printer for performing a printing operation on a label surface of the medium, and a medium transporting unit for holding and transporting the medium to the drive or the printer (for example, see Patent Document 1).
     Patent Document 1: Japanese Patent Publication No. 2006-202379A   

     However, blank mediums that have not been subjected to a recording process and the like are stacked in the medium stacker and a slight clearance in the radius direction of the mediums is generated between the mediums received in the stacker and the stacker. Accordingly, since the mediums stacked in the stacker are randomly received in the stacker, the center positions of the mediums may slightly differ from the pickup center of the mediums with the medium transporting unit. In this case, at the time of holding the inner surface of the center hole of the medium by the use of claws of a holding portion of the medium transporting unit, the holding force moves in the circumferential direction and thus the medium may not be satisfactorily held with good balance, thereby causing the holding failure. 
     The upper and lower mediums may be adhered to each other in the stacker so as to cause an adhesive force therebetween. In this case, when the holding force runs off in the circumferential direction, it is difficult to satisfactorily lift up only the uppermost medium. 
     For example, even when the medium transporting unit is provided with a positioning guide having a cone shape directed downward and the guide is inserted into the center hole of the medium, the medium does not slide in horizontal direction and thus it is difficult to position the center of the medium with respect to the pickup center. Accordingly, at the time of holding the inner circumferential surface of the center hole of the medium, the holding force moves in the circumferential direction so that the medium is not held satisfactorily with good balance, thereby causing the holding failure. 
     In this case, the insertion force of the positioning guide can be enhanced by increasing the pressing force of the holding portion on the medium. However, in a tray of a drive in which a single medium is received, a great load is applied to the tray which should move with high precision due to the pressing force of the holding portion, thereby affecting the movement precision and damaging a moving mechanism of the tray. 
     SUMMARY 
     An object of at least on embodiment of the invention is to provide a medium transporting unit that can satisfactorily position and hold a medium as a holding target with an appropriate force, regardless of a reception state of the medium to be held, and a medium processing apparatus having the medium transporting unit. 
     In order to accomplish the above-mentioned objects, according to an aspect of at least on embodiment of the invention, there is provided a medium transporting unit for transporting a top medium from a plurality of plate-shaped media accommodated in a stacker in a stacked manner, the medium transporting unit comprising: a holding mechanism operable to hold the top medium; and a transport arm provided with the holding mechanism; wherein when the holding mechanism holds the top medium, one of a first pressing force and a second pressing force greater than the first pressing force is selectively applied from the holding mechanism to an upper surface of the top medium. 
     The second pressing force may be applied to the upper surface of the top medium when a plurality of media is accommodated in the stacker. 
     The first pressing force is applied to the upper surface of the top medium when a single medium is accommodated in the stacker. 
     According to the above-mentioned configuration of the medium transporting unit, since the holding mechanism comes in contact with the medium with one of the first pressing force and the second pressing force greater than the first pressing force at the time of lifting down the transport arm, it is possible to position the medium with the medium guide and to hold the medium with the holding mechanism with the proper pressing force depending on the reception state of the medium. 
     For example, when a single medium received in a drive or a tray of a printer which hardly requires the pressing force for positioning the medium is positioned and held, the holding portion can be pressed with the relatively small first pressing force. When a large positional difference occurs and the uppermost medium of the mediums stacked in the stacker, in which the adjacent mediums are adhered to each other to generate an adhesive force, is positioned and held, the holding mechanism can be pressed against the medium with the second pressing force greater than the first pressing force. Accordingly, in the drive or the tray of the printer, it is possible to hold the medium without causing any problem with an excessive pressing force. 
     The medium transporting unit may further comprise and a lift mechanism operable to lift the transport arm up and down. The transport arm may include: a lifted member fixed to the lift mechanism to be lifted up and down; a first urging member operable to urge the lifted member upward with a first urging force so that the holding mechanism applies the first pressing force to the top medium; and a second urging member operable to urge the lifted member upward with a second urging force greater than the first urging force so that the holding mechanism applies the second pressing force to the top medium; and the second urging member may apply the second urging force to the lifted member when the lifted member is lifted down by a predetermined distance. 
     According to this configuration, when the lifted member is lifted down by the predetermined distance against the first urging member, the second urging member is operated by the lifted member. Accordingly, it is possible to easily and properly set the urging force of the first urging member as the first elastic pressing force and to set the urging force of the first urging member, the bending force of the transport arm, and the urging force of the second urging member as the second elastic pressing force. 
     The transport arm may further include an arm body and a pressing lever, one end of which is swingably supported in the arm body; the first urging member may include a first tension spring, one end of which is fixed to the arm body and the other end of which is fixed to the lifted member; the second urging member may include a second tension spring, one end of which is fixed to the arm body and the other end of which is fixed to the other end of the pressing lever; and the pressing lever may swing against the second urging force of the second tension spring after the lifted member comes in contact with the pressing lever and is lifted down. 
     According to this configuration, the urging force of the first tension spring can be used as the first elastic pressing force until the lifted member comes in contact with the pressing lever. When the lifted member comes in contact with the pressing lever and thus the pressing lever swings, the urging force of the first tension spring, the bending force of the transport arm, and the urging force of the second tension spring can be used as the second elastic pressing force. 
     The lift mechanism may include a timing belt; and the lifted member may include a belt clip fixed to the timing belt. 
     According to this configuration, the transport arm can be fixed to the lift mechanism with a simple structure. 
     The holding mechanism may include a contact portion adapted to come in contact with the upper surface of the top medium in the vicinity of a center hole formed on the top medium. 
     According to this configuration, a problem with the adhesion between the mediums can be easily solved. 
     The holding mechanism may include a pressing member operable to press an inner peripheral surface of a center hole formed on the top medium. 
     According to this configuration, the holding mechanism can hold the medium with a simple structure. 
     The holding mechanism may include a medium guide having a circular truncated cone shape directed downward and adapted to be inserted into a center hole formed on the top medium. 
     According to this configuration, the uppermost medium can slide horizontally for positioning by the use of the medium guide against the adhesive force between the uppermost medium and the right below medium and can be held by the use of the holding mechanism. 
     The first pressing force may be generated by the first urging force of the first urging member; and the second pressing force may be generated by the first urging force of the first urging member and the second urging force of the second urging member. 
     According to the other aspect of at least on embodiment of the invention, there is provided a medium processing apparatus comprising: the above stacker; the medium transporting unit; and a media drive having at least one of a function for writing data on the transported medium which is transported by the medium transporting unit and a function for reading data on the transported medium. 
     According to the medium processing apparatus having the Above-mentioned configuration, since it includes the medium transporting unit that can satisfactorily position and hold the medium, it is possible to provide a medium processing apparatus with high reliability. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above objects and advantages of the present invention will become more apparent by describing in detail preferred exemplary embodiments thereof with reference to the accompanying drawings, wherein: 
         FIG. 1  is a perspective view illustrating an appearance of a publisher (medium processing apparatus); 
         FIG. 2  is a perspective view illustrating the front side of the publisher with a case removed from the publisher; 
         FIG. 3  is a perspective view illustrating the rear side of the publisher with the case removed from the publisher; 
         FIG. 4  is a perspective view illustrating a recording unit of the publisher; 
         FIG. 5  is a perspective view illustrating a medium transporting unit; 
         FIG. 6  is a perspective view illustrating a part of the medium transporting unit; 
         FIG. 7  is a perspective view illustrating a connection mechanism between a transport arm and a timing belt; 
         FIG. 8  is an enlarged perspective view illustrating the connection mechanism between the transport arm and the timing belt as viewed from the bottom; 
         FIG. 9  is a perspective view illustrating an internal structure of the transport arm; 
         FIG. 10  is a plan view illustrating the transport arm having held a medium as viewed from the bottom; 
         FIG. 11  is a sectional view illustrating a holding portion of the transport arm; 
         FIG. 12  is a perspective view illustrating a medium guide disposed in the holding portion of the transport arm; 
         FIG. 13  is a plan view illustrating the medium guide disposed in the holding portion of the transport arm; 
         FIG. 14  is a plan view of an arm base which is intended to explain a holding mechanism; 
         FIG. 15  is a perspective view illustrating holding claws of the holding mechanism; 
         FIG. 16  is an enlarged plan view illustrating the holding claws; 
         FIG. 17  is a plan view illustrating movements of swinging plates and the holding claws; 
         FIG. 18  is a plan view illustrating movements of the swinging plates and the holding claws; 
         FIG. 19  is a plan view illustrating movements of the swinging plates and the holding claws; 
         FIG. 20  is a sectional view illustrating the holding claws; 
         FIG. 21  is a plan view of an arm base which is intended to explain a separation mechanism; 
         FIG. 22  is a front view illustrating the transport arm when the holding portion is viewed in a section; 
         FIG. 23  is a perspective view illustrating the separation mechanism; 
         FIG. 24  is a sectional view illustrating a swinging mechanism disposed in the separation mechanism; 
         FIG. 25  is a plan view illustrating the swinging mechanism disposed in the separation mechanism; 
         FIG. 26  is a plan view schematically illustrating the movement of the separation mechanism; 
         FIG. 27  is a plan view schematically illustrating the movement of the separation mechanism; 
         FIG. 28  is a graph illustrating a relation between a down stroke of a belt clip of the transport arm and a load acting on a medium; and 
         FIG. 29  is a flowchart illustrating a process of controlling a driving motor for lifting up and down the transport arm. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, a medium transporting unit according to an embodiment of the invention and a medium processing apparatus having the medium transporting unit will be described with reference to the drawings. 
     In this embodiment, the invention is applied to a medium processing apparatus including a publisher. 
     As shown in  FIG. 1 , the publisher  1  is a medium processing apparatus for recording data on a disc-like medium such as CD or DVD or printing an image on a label surface of the medium and has a case  2  having a substantially rectangular hexahedral shape. Shutters  3  and  4  which can be opened and closed slidably in the lateral direction are attached to the front surface of the case  2 . An operation surface  5  having display lamps, operation buttons, and the like arranged thereon is disposed at the left-upper end portion of the case  2  and a medium discharge port  6  is disposed at the lower end of the case  2 . 
     The right shutter  3  as viewed from the front side is a door which is opened and closed at the time of setting a blank medium MA not used or taking out the completed medium MB (see  FIG. 2 ). 
     The left shutter  4  as viewed from the front side is opened and closed at the time of replacing an ink cartridge  12  of a label printer  11  (see  FIG. 2 ). By opening the shutter  4 , a cartridge mounting section  14  (see  FIG. 2 ) having plural cartridge holders  13  arranged in the vertical direction is exposed. 
     As shown in  FIG. 2 , in the case  2  of the medium processing apparatus  1 , a blank medium stacker  21  as a medium storage unit in which plural blank mediums MA not yet used and not yet subjected to a data recording process can be stacked and a completed medium stacker  22  as a medium storage unit in which completed mediums MB are disposed vertically so that the center lines of the stored mediums are aligned with each other. The blank medium stacker  21  and the completed medium stacker  22  can be attached to and detached from predetermined positions shown in  FIG. 2 . 
     The blank medium stacker  21  has a pair of arc-shaped frames  24  and  25 . Accordingly, the blank mediums MA can be received from the top and can be stacked coaxially in the stacker. The operation of receiving or replenishing the blank mediums MA in the blank medium stacker  21  can be simply performed by opening the shutter  3  and taking out the stacker. 
     The completed medium stacker  22  has the same structure and includes a pair of arc-shaped frames  27  and  28 . Accordingly, the completed mediums MB can be received from the top and can be stacked coaxially in the stacker. 
     The completed mediums MB (that is, mediums having been completely subjected to a data recording process and a label-surface printing process) may be taken out through the shutter  3 . 
     A medium transporting unit  31  is disposed in the back of the blank medium stacker  21  and the completed medium stacker  22 . In the medium transporting unit  31 , a chassis  32  is swingably attached to a vertical guide shaft  35  vertically suspended between a base  72  and the top plate of the case  2  (see  FIG. 5 ). A fan-shaped final-stage gear  109  is fixed to a horizontal supporting plate  34  of the chassis  32  (see  FIG. 5 ). The transport arm  36  is supported by the chassis  32  so as to freely go up and down. The transport arm  36  can be lifted up and down along the vertical guide shaft  35  by a driving motor  37  which can be a step motor and can horizontally swing about the vertical guide shaft  35 . A medium transported to the medium discharge port  6  by the medium transporting unit  31  can be taken out of the medium discharge port  6 . 
     Two medium drives  41  vertically stacked are disposed on a side of the upper and lower stackers  21  and  22  and the medium transporting unit  31 . A carriage  62  (see  FIG. 4 ) of a label printer  11  is movably disposed below the medium drives  41 . 
     The medium drives  41  have medium trays  41   a  that can move between a data recording position where data is recorded on a medium and a medium transferring position where the medium is transferred, respectively. 
     The label printer  11  has a medium tray  51  that can move between a printing position where an image is printed on a label surface of the medium and a medium transferring position where the medium is transferred (see  FIG. 3 ). 
     In  FIGS. 2 and 3 , a state where the medium tray  41   a  of the upper medium drive  41  is drawn forward and located at the medium transferring position and a state where the medium tray  51  of the lower label printer  11  is located at the label printing position are shown. The label printer  11  is an ink jet printer and employs ink cartridges  12  of various colors (6 colors of black, cyan, magenta, yellow, light cyan, and light magenta in this embodiment) as the ink supply mechanism  71 . The ink cartridges  12  are mounted on the cartridge holders  13  of the cartridge mounting section  14  from the front side. 
     Here, a gap through which the transport arm  36  of the medium transporting unit  31  can be lifted up and down is formed between the pair of frames  24  and  25  of the blank medium stacker  21  and between the pair of frames  27  and  28  of the completed mediums stacker  22 . A clearance allowing the transport arm  36  of the medium transporting unit  31  to horizontally swing and to be located just above the completed medium stacker  22  is opened between the blank medium stacker  21  and the completed medium stacker  22 . When the medium tray  41   a  is pushed into the medium drive  41 , the transport arm  36  of the medium transporting unit  31  can be lifted down to access the medium tray  51  located at the medium transfer position. Accordingly, it is possible to transport the mediums to the individual elements by combination of the lifting operation and the swinging operation of the transport arm  36 . 
     A waste stacker  52  for storing waste mediums MD is disposed below the medium transfer position of the medium tray  51 . For example, about 30 waste mediums MD can be stored in the waste stacker  52 . In a state where the medium tray  51  retreats from the medium transfer position above the waste stacker  52  to the data recording position, the waste mediums MD can be supplied to the waste stacker  52  by the use of the transport arm  36  of the medium transporting unit  31 . 
     Due to the above-mentioned configuration, the transport arm  36  of the medium transporting unit  31  can transport a medium such as a CD or DVD among the blank medium stacker  21 , the completed medium stacker  22 , the waste stacker  52 , the medium tray  41   a  of the medium drive  41 , and the medium tray  51  of the label printer  11 . 
     As shown in  FIG. 4 , the label printer  11  includes a carriage  62  having an ink jet head  61  with ink ejecting nozzles (not shown). The carriage  62  horizontally reciprocates along a carriage guide shaft  63  by means of the driving force of a carriage motor  65  (see  FIG. 3 ). 
     The label printer  11  includes an ink supply mechanism  71  having a cartridge mounting section  14  to be mounted with ink cartridges  12  (see  FIG. 2 ). The ink supply mechanism  71  has a vertical structure and is formed upright in the vertical direction on a base  72  of the publisher  1 . An end of a flexible ink supply tube  73  is connected to the ink supply mechanism  71  and the other end of the ink supply tube  73  is connected to the carriage  62  (see  FIG. 4 ). 
     The ink of the ink cartridges  12  mounted on the ink supply mechanism  71  is supplied to the carriage  62  through the ink supply tube  73 , is supplied to the ink jet head  61  through a damper unit and a pressure distribution control unit (not shown) disposed in the carriage  62 , and then is ejected from the ink nozzles (not shown). 
     A pressurizing mechanism  74  is disposed in the ink supply mechanism  71  so as to put the main portion is above the ink supply mechanism The pressurizing mechanism  74  pressurizes the ink cartridges  12  by blowing out compressed air, thereby sending out the ink stored in ink packs of the ink cartridges  12 . 
     A head maintenance mechanism  81  is disposed below the home position (position shown in  FIG. 4 ) of the carriage  62 . 
     The head maintenance mechanism  81  includes a head cap  82  covering the ink nozzles of the ink jet head  61  exposed from the bottom surface of the carriage  62  located at the home position and a waste ink suction pump  83  sucking the ink discharged to the head cap  82  due to a head cleaning operation or an ink filling operation of the ink jet head  61 . 
     The ink sucked by the waste ink suction pump  83  of the head maintenance mechanism  81  is sent to a waste ink tank  85  through a tube  84 . 
     In the waste ink tank  85 , an absorbing material is disposed in a case  86  and the top surface is covered with a cover  88  having plural ventholes  87 . 
     A waste ink receiver  89  as a part of the waste ink tank  85  is disposed below the head maintenance mechanism  81  and receives the ink from the head maintenance mechanism  81 . Then, the ink is absorbed by the absorbing material. 
     As shown in  FIG. 5 , in the medium transporting unit  31 , the horizontal supporting plate  34  and the top plate  33  of the cassis  32  is supported by the vertical guide shaft  35  disposed in the vertical direction. Here, the chassis  32  is swingable. The transport arm  36  is supported by the chassis  32  so as to be lifted up and down. 
     As shown in  FIG. 6 , the lift mechanism of the transport arm  36  includes a lifting driving motor (lift mechanism)  37  as a driving source, which employs a pulse motor in this embodiment. The rotation of the driving motor  37  is transmitted to a driving pulley  101  through a pinion  97  and a transmission gear  98  fitted to an output shaft of the driving motor  37 . The driving pulley  101  is supported to be rotatable about a horizontal rotation shaft in the vicinity of the top end of the chassis  32 . A driven pulley  103  is supported to be rotatable about the horizontal rotation shaft in the vicinity of the bottom end of the chassis  32 . A timing belt (lift mechanism)  104  is suspended on the driving pulley  101  and the driven pulley  103 . As shown in  FIG. 7 , a base  110  of the transport arm  36  is connected to one horizontal end of the timing belt  104  through a belt clip (lift member)  112 . 
     Accordingly, when the driving motor  37  is activated, the timing belt  104  moves in the vertical direction and the transport arm  36  attached thereto is thus lifted up and down along the vertical guide shaft  35 . A sensor not shown for detecting the home position of the timing belt  104  is attached to the chassis  32 . 
     As shown in  FIG. 5 , a rotation mechanism of the transport arm  36  includes a rotational driving motor  105  as a driving source and a pinion (not shown) is fitted to the output shaft of the driving motor  105 . The rotation of the pinion is transmitted to the fan-shaped final-stage gear  109  through a reduction gear train having a transmission gear  107 . The fan-shaped final-stage gear  109  can rotate horizontally about the vertical guide shaft  35 . The final-stage gear  109  is mounted to the chassis  32  having constituent elements of the lift mechanism for the transport arm  36 . When the driving motor  105  is activated, the fan-shaped final-stage gear  109  rotates horizontally and thus the chassis  32  mounted thereon monolithically rotates horizontally about the vertical guide shaft  35 . As a result, the transport arm  36  retained by the lift mechanism mounted on the chassis  32  rotates horizontally about the vertical guide shaft  35 . A sensor not shown for detecting the home position (a position just above the medium trays  41   a  and  51  where the transport arm  36  is located at the medium transfer position) of the final-stage gear  109  and positions just above the blank medium stacker  21  and the completed medium stacker  22  is fitted to the base  72 . 
     Next, a supporting structure of the transport arm  36  will be described. 
     As shown in  FIGS. 7 and 8 , a sliding shaft (support portion)  111  is vertically disposed on the base  110  of the transport arm  36 . The sliding shaft  111  is inserted through a shaft hole  112   a  of the belt clip  112  fixed by holding the timing belt  104  (see  FIG. 7 ) so as to be slidable from the upside. In  FIG. 8 , the timing belt  104  is omitted. 
     A locking piece  112   b  is formed in the belt clip  112 . An end of a first tension spring (first elastic urging means  113 ) which is a coil spring is connected to the locking piece  112   b . The other end of the first tension spring  113  is connected to a fixed piece  115  formed in the base  110  of the transport arm  36  and disposed above the locking piece  112   b . Accordingly, the base  110  of the transport arm  36  is urged downward by the first tension spring  113 . 
     A fixing portion  112   c  for fixing the timing belt  104  therebetween is formed in the belt clip  112 . 
     A pressing lever  116  attached to the base  110  of the transport arm  36  is disposed below the belt clip  112 . The pressing lever  116  is laterally inserted through an insertion hole  118  formed in a supporting plate  117  disposed on the bottom of the base  110  of the transport arm  36  and is swingable about a supporting point in the supporting plate  117 . An end of a second tension spring (second elastic urging means)  119  formed of a coil spring having an urging force greater than that of the first tension spring  113  is connected to an end of the pressing lever  116  and the other end of the second tension spring  119  is connected to a fixed piece  120  that is formed in the base and disposed above the end of the pressing lever  116 . Accordingly, the end of the pressing lever  116  is urged upward by the second tension spring  119 . A swing regulating piece  121  formed on the base  110  is disposed above the vicinity of the end of the pressing lever  116  and the swing of the pressing lever  116  urged upward by the second tension spring  119  is regulated to a predetermined position. The belt clip  112  is disposed at a position apart from the pressing lever  116  regulated by the swing regulating piece  121 , by clearance S. 
     In the above-mentioned supporting structure, when the timing belt  104  is driven by the lifting driving motor  37  (see  FIG. 5 ), the transport arm  36  is lifted up and down monolithically with the belt clip  112  fixed to the timing belt  104 . When a medium guide  133  to be described later or a holding mechanism  130  comes in contact with the medium and a down load of the transport arm  36  increases, only the belt clip  112  moves down against the urging force of the first tension spring  113  relative to the transport arm  36 . When the belt clip  112  further moves down by means of the timing belt  104 , the belt clip  112  comes in contact with the pressing lever  116 , the transport arm  36  is slightly bent, and then the pressing lever  116  swings about a support point in the supporting plate  117  against the urging force of the second tension spring  119 . 
     Next, inner mechanisms of the transport arm  36  will be described. 
     As shown in  FIG. 9 , the transport arm  36  includes a longitudinal arm base  125   a  having a rectangular shape in the plan view and an arm case  125   b  having the same profile as the arm base  125   a  so as to cover the arm base. The arm base  125   a  is provided with a holding mechanism  130  for holding a medium M, a separation mechanism  131 , and a medium detecting mechanism  200 . The holding mechanism  130 , the separation mechanism  131 , and the medium detecting mechanism  200  are covered with the arm case  125   b.    
     As shown in  FIGS. 10 and 11 , a bottom portion in the vicinity of the end of the arm base  125   a  serves as the holding portion  132  for holding a medium M. The medium guide  133  is disposed in the holding portion  132 . 
     As shown in  FIGS. 12 and 13 , the center of the medium guide  133  corresponds to the pickup center of the medium M and the medium guide has a guide portion  135  protruding downward at the center of a fixed portion  134  fixed to the bottom surface of the arm base  125   a . The guide portion  135  has a cylindrical base end  135   a  formed with a diameter slightly smaller than that of the center hole Ma of the medium M and a guide surface  135   b  formed in a cone shape that points downward from the base end  135   a . The medium guide  133  is inserted into the center hole Ma of the medium M by approaching the medium M, the inner circumferential surface Mb of the center hole Ma of the medium m is guided by the guide surface  135   b , the center position of the medium M is aligned with the center position of the medium guide  133  by the guide surface  135   b , and then the center hole Ma of the medium M is guided by the base end  135   a , whereby the base end  135   a  is inserted through the center hole of the medium M. 
     Three window portions  133   a  are formed in the medium guide  133 . Three holding claws  141  to  143  of the holding mechanism  130  and an operation piece  183  of the pressing lever  182  of the separation mechanism  131  can protrude and retreat into and from the window portions  133   a.    
     As shown in  FIGS. 12 and 13 , the holding mechanism  130  has three cylindrical holding claws  141  to  143  which are disposed at an approximate equiangular interval (120°) on the same circle. The holding claws  141  to  143  protrudes vertically downward from circular hole  125   c  formed in the arm base  125   a  and are disposed inside the window portions  133   a  of the medium guide  133 . The three holding claws  141  to  143  are inserted into the center hole Ma of the medium, guided to the base end  135   a  of the medium guide  133 , then are made to move outward, and are made to protrude from the window portions  133   a  of the medium guide  133 , thereby pressing the inner circumferential surface Mb of the center hole Ma of the medium M to hold the medium M. 
     As shown in  FIG. 20 , the holding claws  141  to  143  are attached to lower ends of supporting pins  151  to  153  having a diameter greater than the holding claws. The supporting pins  151  to  153  extend upwardly through the circular hole  125   c  of the arm base  125   a  and three swinging plates  161  to  163  disposed on the top surface of the arm base  125   a . Swinging center axes  171  to  173  are vertically fixed to the arm base  125   a  at the equiangular interval on the same circle so as to surround the circular hole  125   c . The swinging plates  161  to  163  are supported to be swingable about the swinging center axes  171  to  173 , respectively. 
     As shown in  FIGS. 14 to 16 , each swinging plate  161  to  163  includes a front arm portion  161   a  to  163   a  extending counterclockwise in the top view, a rear arm portion  161   b  to  163   b  extending clockwise in the top view, and supporting arms  161   c  to  163   c  protruding inside the center hole  125   c  from the swinging center, along the arm base  125   a  from the swinging center axis  171  to  173 . The supporting pins  151  to  153  are vertically formed on the rear surface of the ends of the supporting arms  161   c  to  163   c , respectively. 
     A longitudinal hole  161   d  in a direction substantially perpendicular to the circular hole  125   c  is formed in the rear arm portion  161   b  of the swinging plate  161 . A slide pin  163   f  protruding downward from the rear end of the front arm portion  163   a  of the swinging plate  163  is slidably inserted through the longitudinal hole  161   d.    
     A slide surface  163   e  (see  FIG. 16 ) in a direction substantially perpendicular to the circular hole  125   c  is formed at the end of the rear arm portion  163   b  of the swinging plate  163  and the front end of the front arm portion  162   a  of the swinging plate  162  is established so as not to come in contact with the slide surface  163   e . A slide surface  162   e  in the direction substantially perpendicular to the circular hole  125   c  is formed at the end of the rear arm portion  162   b  of the swinging plate  162  and the front end of the front arm portion  161   a  of the swinging plate  161  is in sliding contact with the slide surface  162   e . Here, the longitudinal hole  161   d  of the swinging plate  161  and the slide surfaces  162   e  and  163   e  of the swinging plates  162  and  163  are formed in a concave curved shape set to allow the swinging plates  161  to  163  to swing the in same direction. 
     Tension coil springs (urging members)  174  are suspended between the rear arm portion  161   b  of the swinging plate  161  and the rear arm portion  162   b  of the swinging plate  162 , between the rear arm portion  162   b  of the swinging plate  162  and the rear arm portion  163   b  of the swinging plate  163 , and between the rear arm portion  163   b  of the swinging plate  163  and the rear arm portion  161   b  of the swinging plate  161 . By means of the tension of the tension coil springs  174 , the swinging plates  161  to  163  are supported without swinging independently and the urging force, in the direction indicated by arrow R 1  in  FIG. 16 , that is, in the direction in which the holding claws  141  to  143  move outward, is applied to the swinging plates  161  to  163 . 
     In the state shown in  FIG. 16 , the circumscribed circle of the holding claws  141  to  143  attached to the ends of the supporting arms  161   c  to  163   c  of the swinging arms  161  to  163  has a diameter greater than the inner diameter of the center hole Ma of the medium M. In this state, when swinging plate  161  is made to swing in the direction indicated by arrow R 2 , the other swinging plates  162  and  163  accordingly swing in the same direction as indicated by arrow R 2 . As a result, the supporting arms  161   c  to  163   c  of the swinging plates  161  to  163  move to the center of the circular hole  125   c  and the holding claws  141  to  143  attached to the ends move inward so that they can be inserted into the center hole Ma of the medium M. 
     In this state, when the holding claws  141  to  143  are inserted into the center hole Ma of the Medium and then the swinging plates  161  to  163  are made to swing in the opposite direction R 1 , the holding claws  141  to  143  move outward in the radius direction. As a result, the holding claws  141  to  143  are pressed on the inner circumferential surface Mb of the center hole of the medium M, thereby holding the medium M. 
     As shown in  FIG. 14 , an operation arm  161   g  extending to the opposite side of the supporting arm  161   c  is formed in the swinging plate  161 . The end of one arm portion  175   a  of a link  175  is rotatably connected to the end of the operation arm  161   g . The link  175  is supported by the arm base  125   a  so as to be rotatable about a middle portion thereof and the end of the opposite arm portion  175   b  is connected to an operation rod  176   a  of an electromagnetic solenoid  176 . When the electromagnetic solenoid  176  is turned off, the operation rod  176   a  protrudes by action of the spring force of a built-in spring. 
     In this state, where the electromagnetic solenoid  176  is turned on, the operation rod  176   a  is reversely inserted against the spring force in the electromagnetic solenoid, the link  175  swings clockwise, and the swinging plate  161  thus swings in the direction of R 2 . Then, as shown in  FIG. 17 , the slide surface  162   e  of the rear arm portion  162   b  of the swinging plate  162  comes in sliding contact with the end of the front arm portion  161   a  of the swinging plate  161  and the inner surface of the longitudinal hole  161   d  of the rear arm portion  161   b  of the swinging plate  161  comes in sliding contact with the slide pin  163   f  of the front arm portion  163   a  of the swinging plate  163 . Accordingly, the slide surface  162   e  of the swinging plate  162  comes in sliding contact with the end of the front arm portion  161   a  of the swinging plate  161  and slides outward in the diameter direction of the circular hole  125   c , whereby the swinging plate  162  swings in the direction of R 2 . The inner surface of the longitudinal hole  161   d  of the rear arm portion  161   b  of the swinging plate  161  comes in sliding contact with the slide pin  163   f  of the front arm portion  163   a  of the swinging plate  163  and thus the front arm portion  163   a  of the swinging plate  163  slides toward the center of the circular hole  125   c , whereby the swinging plate  163  also swings in the direction of R 2 . 
     In this way, when the swinging plate  161  swings in the direction of R 2 , the swinging force in the direction of R 2  of the swinging plate  161  is transmitted to the other swinging plates  162  and  163  and thus the swinging plates  162  and  163  also swing in the direction of R 2 , as shown in  FIG. 18 . The holding claws  141  to  143  disposed in the supporting arms  161   c  to  163   c  of the swinging plates  161  to  163  are disposed in the circumscribed circle sufficiently smaller than the center hole Ma of the medium M and move inward until it can be inserted into the center hole Ma of the medium M. 
     In this state, when the electromagnetic solenoid  176  is turned off, the operation rod  176   a  is made to protrude by means of the spring force of the spring in the electromagnetic solenoid and the tension coil spring  174  and the link  175  thus swings. Then, the swinging motion of the link  175  is transmitted to the swinging plate  161  and thus the swinging plate  161  swings in the direction of R 1 . Accordingly, in the other swinging plates  162  and  163 , the rear arm portions  162   b  and  163   b  move toward the center of the circular hole  125   c  by means of the tension of the tension coil spring  174  and thus the swinging plates  162  and  163  also swing in the direction of R 1  like the swinging plate  161 . As a result, as shown in  FIG. 19 , the holding claws  141  to  143  move outward and the holding claws  141  to  143  are pressed on the inner circumferential surface Mb of the center hole Ma of the medium M, thereby holding the medium M. 
     At this time, since the swinging plates  162  and  163  swing in the direction of R 1  by means of the tension of the tension coil spring  174  independently of the swinging plate  161 , the holding claws  141  to  143  move outward in the radius direction independently of each other and thus are pressed on the inner circumferential surface Mb of the center hole Ma of the medium M. 
     As shown in  FIG. 20 , each of three holding claws  141  to  143  includes a cylindrical pin  141   a  to  143   a  protruding form the bottom end of the supporting pin  151  to  153  and an elastic cylinder  141   b  to  143   b  made of rubber to surround the pin  141   a  to  143   a  concentrically. Here, although the cylindrical pin  142   a  and the elastic cylinder  142   b  are not shown in  FIG. 20 , these components are provided with the holding claw  142  in a similar configuration as the holding claws  141  and  143 . In the holding claws  141  to  143 , the downward protruding length l is equal to or smaller than the thickness t1 of the medium M to be held. It is preferable that the producing length l is equal to or greater than the thickness t2 of the inner circumferential surface Mb of the center hole Ma of the medium M and equal to or smaller than the thickness t1 of the medium M including the height of a ring-shaped protrusion Mc. Accordingly, when the mediums M stacked in the thickness direction are held, the holding claws  141  to  143  hold only the uppermost medium M without coming in contact with the inner circumferential surface Mb of the second medium M. The portions of the supporting pins  151  to  153  close to the holding claws  141  to  143  are contact surfaces  151   a  to  151   b  with the medium Mm to be held. 
     As shown in  FIGS. 21 to 23 , the separation mechanism  131  disposed in the arm base  125   a  of the transport arm  36  includes a pressing lever  182  that is rotatably supported by a support shaft  181  formed in the arm base  125   a . The pressing lever  182  includes two components of a front lever portion  182   a  on the holding side and a rear lever portion  182   b  on the rotation side. In the front lever portion  182   a , a cylindrical bearing portion  184  inserted through the support shaft  181  formed in the arm base  125   a  is made to protrude upward and the rear lever portion  182   b  is swingably supported by the bearing portion  184 . The front lever portion  182   a  and the rear lever portion  182   b  are swingable in a predetermined range by a locking portion  185  which is prevented from being separated from the front lever portion  182   a  and an opening  186  having a width greater than the width of the locking portion  185  and being disposed in the rear lever portion  182   b . As shown in  FIGS. 23 and 26 , the front lever portion  182   a  and the rear lever portion  182   b  are urged in a direction by a buffer spring  187  which is a twist coil spring. Specifically speaking, in the buffer spring  187  attached to the outer circumference of the swinging portion of the rear lever portion  182   b , one arm portion  187   a  urges a receiving portion  182   d  of the front lever portion  182   a  and the other arm portion  187   b  urges a receiving portion  182   e  of the rear lever portion  182   b  so as to be apart from each other. Accordingly, in the pressing lever  182 , a great load is applied to an operation piece  183  to be described later when the rear lever portion  182   b  allows the front lever portion  182   a  to swing, and the buffer spring  187  is bent when the front lever portion  182   a  cannot swing, thereby preventing the damage of the operation piece  183 . The front lever portion  182   a  has the operation piece  183  bent from the front end to the down side and laterally bent in an L shape. The operation piece  183  is disposed in the medium guide  133  of the holding portion  132 . 
     In a state where the holding claws  141  to  143  of the holding portion  132  hold the medium M, the operation piece  183  of the pressing lever  182  is disposed horizontal below the medium M. Specifically, the operation piece is disposed at a position corresponding to the second medium M of the mediums stacked in the thickness direction. 
     When the pressing lever  182  swings at the connection point  181  in the direction of R 3  in  FIG. 21 , the operation piece  183  protrudes laterally from the window portion  133   a  of the medium guide  133  and comes in pressing contact with the inner circumferential surface Mb of the center hole Ma of the second medium M just below the uppermost medium M held by the holding claws  141  to  143 . When the pressing lever  182  swings in the opposite direction of R 4  in this state, the operation piece  183  is inserted into the medium guide  133 . 
     A swing mechanism  190  for allowing the pressing lever  182  to swing is disposed in the rear lever portion  182   b  of the pressing lever  182 . The swing mechanism  190  includes a complex clutch gear  191 , a vertical complex transmission gear  192 , a horizontal complex transmission gear  193 , and a lock  194 . 
     As shown in  FIG. 5 , the lock  194  is vertically supported by the chassis  32  constituting the medium transporting unit  31  so as to be parallel to the vertical guide shaft  35 . The lock  194  engages with a pinion  193   b  of the horizontal complex transmission gear  193  supported by the arm base  125   a  so as to be rotatable about a horizontal shaft  193   a  (see  FIG. 23 ). By lifting up and down the transport arm  36 , the horizontal complex transmission gear  193 , which has the pinion  193   b  that engages with the lock  194 , rotates. 
     A screw gear  193   c  is disposed in the horizontal complex transmission gear  193 . The screw gear  193   c  engages with a screw gear  192   b  of the vertical complex transmission gear  192  supported by the arm base  125   a  so as to be rotatable about a vertical shaft  192   a . Accordingly, when the horizontal complex transmission gear  193  rotates, the rotation of the horizontal complex transmission gear  193  having the horizontal shaft  193   a  is transmitted to the vertical complex transmission gear  192  having the vertical shaft  192   a  through the screw gears  192   b  and  193   c  engaging with each other, thereby allowing the vertical complex transmission gear  192  to rotate. 
     The vertical complex transmission gear  192  includes a horizontal gear  192   c . The horizontal gear  192   c  engages with a horizontal gear  191   b  of the complex clutch gear  191  supported by the arm base  125   a  so as to be rotatable about the vertical shaft  191   a . Accordingly, when the vertical complex transmission gear  192  rotates, the rotating force of the vertical complex transmission gear  192  is transmitted to the complex clutch gear  191  through the horizontal gears  191   b  and  192   c  engaging with each other, thereby allowing the complex clutch gear  191  to rotate. 
     As shown in  FIGS. 24 and 25 , the complex clutch gear  191  includes an intermittent gear  191   c  that is rotatable relative to the horizontal gear  191   b . A clutch mechanism  195  is disposed between the horizontal gear  191   b  and the intermittent gear  191   c . The horizontal gear  191   b  has a cylinder shaft  191   d  through which the shaft  191   a  is inserted. The cylinder shaft  191   d  is inserted through a cylinder shaft  191   e  formed in the intermittent gear  191   c.    
     As shown in  FIG. 25 , the intermittent gear  191   c  has a gear train  196  including plural gears  196   a  on a part of the circumferential surface. The gear train  196  can engage with the horizontal gear  192   c  of the vertical complex transmission gear  192 . 
     The clutch mechanism  195  disposed in the complex clutch gear  191  has a twist coil spring  197  wound on the cylinder shaft  191   e  of the intermittent gear  191   c . When the horizontal gear  191   b  is made to rotate in the counterclockwise direction of R 5  as viewed from the upside in  FIG. 25  by the horizontal gear  192   c  of the vertical complex transmission gear  192 , the intermittent gear  191   c  is made to rotate with the horizontal gear  191   b  by the frictional force generated from the twist coil spring  197 . Accordingly, the gear train  196  engages with the horizontal gear  192   c  of the vertical complex transmission gear  192  and thus the intermittent gear  191   c  rotates in the direction of R 5  along with the horizontal gear  191   b . On the contrary, when the horizontal gear  191   b  is made to rotate in the clockwise direction of R 6  as viewed from the upside in  FIG. 25  by the horizontal gear  192   c  of the vertical complex transmission gear  192 , the intermittent gear  191   c  is made to rotate along with the horizontal gear  191   b  by means of the frictional force generated from the twist coil spring  197 . Accordingly, the gear train  196  engages with the horizontal gear  192   c  of the vertical complex transmission gear  192  and thus the intermittent gear  191   c  rotates in the direction of R 6  along with the horizontal gear  191   b.    
     A cam hole  198  is formed in the intermittent gear  191   c . A cam pin  182   c  protruding downward from the vicinity of the rear end of the rear lever portion  182   b  of the pressing lever  182  is slidably disposed in the cam hole  198 . The cam hole  198  has a path changing from the center to the outer circumference in the clockwise direction in the top view. Accordingly, when the intermittent gear  191   c  rotates in the counterclockwise direction of R 5  in the top view in the state shown in  FIG. 26 , the cam pin  182   c  in the cam hole  198  is displaced to the outer circumference. Accordingly, as shown in  FIG. 27 , the pressing lever  182  swings in the direction of R 3  about a connection point  181  and thus the operation piece  183  protrudes to the outside of the medium guide  133 . In this state, when the intermittent gear  191   c  rotates in the clockwise direction of R 6  in the top view, the cam pin  182   c  in the cam hole  198  is displaced to the inner circumference. Accordingly, as shown in  FIG. 26 , the pressing lever  182  swings about the connection point  181  in the direction of R 4  and thus the operation piece  183  is inserted into the medium guide  133 . 
     In the separation mechanism  131  having the above-mentioned configuration, when the transport arm  36  starts going up, the complex clutch gear  191  starts rotating in the direction of R 5 . When the transport arm  36  further goes up and the complex clutch gear  191  rotates by a predetermined angle (about 45°) from the state shown in  FIG. 26  to the state shown in  FIG. 27 , the pressing lever  182  swings in the direction of R 3  (see  FIG. 21 ) and thus the operation piece  183  of the pressing lever  182  separates the second medium M in the meantime. When the transport arm  36  goes down, the complex clutch gear  191  rotates in the direction of R 6 . Accordingly, the pressing lever  182  rotates in the direction of R 4  (see  FIG. 21 ) and the operation piece  183  is inserted into the medium guide  133  as shown in  FIG. 26 . Even when the transport arm  36  goes down in this state, the gear train  196  runs off from the horizontal gear  192   c  after the intermittent gear  191   c  of the complex clutch gear  191  rotates by a predetermined angle (about 45°) in the direction of R 6  (see  FIG. 26 ) by the horizontal gear  192   c  of the vertical complex transmission gear  192  and thus the intermittent gear idly rotates relative to the horizontal gear  191   b.    
     As shown in  FIG. 9 , the medium detecting mechanism  200  includes a detection lever  201  of which the rear end is swingably supported and the front end is bent downward to protrude toward the bottom surface of the arm base  125   a  and a detector  202  disposed aside the detection lever  201 . In the medium detecting mechanism  200 , when the transport arm  36  goes down to bring the top surface of the medium M into contact with the detection lever  201  and thus the detection lever  201  swings upward to allow the detection lever  201  to depart from the detection area of the detector  202 , the detector  202  is turned on and thus it is possible to detect an approaching state to the medium M from the detection signal output from the detector  202 . 
     Next, an operation of picking up a medium M in the medium transporting unit  31  having the above-mentioned configuration will be described. 
     An example where the uppermost medium M of the mediums M stacked is held and picked up from the blank medium stacker  21  will be described with reference to the flowchart of controlling the lifting driving motor of the transport arm, which is shown in  FIG. 29 . 
     First, in a state where the transport arm  36  is located at a predetermined height position just above the blank medium stacker  21 , the electromagnetic solenoid  176  of the holding mechanism  130  is turned on. In this state, the operation rod  176   a  of the electromagnetic solenoid  176  is inserted against the built-in spring, this movement is transmitted to the swinging plate  161  through the link  175 , and the swinging plate  161  swings in the direction of R 2  in  FIG. 16 . Accordingly, the other swinging plates  162  and  163  swing in the same direction and the holding claws  141  to  143  attached to the ends of the supporting arms  161   c  to  163   c  of three swinging plates  161  to  163  moves close to each other, whereby it gets pointed so as to be inserted into the center hole Ma of the medium M. 
     Thereafter, the lifting driving motor  37  of the transport arm  36  is driven (ST 1 ) and the belt clip  112  fixed to the timing belt  104  goes down (ST 2 ), thereby starting the lift-down operation of the transport arm  36 . When the transport arm  36  is lifted down and gets close to the uppermost medium M, the medium guide  133  of the holding portion  132  is inserted into the center hole Ma of the medium M. Here, even when the center of the medium M in the blank medium stacker  21  runs off from the center of the holding portion  132 , the inner circumferential surface Mb of the center hole Ma of the medium M comes in contact with the conical guide surface  135   b , the center position of the medium M is thus aligned with the center position of the medium guide  133  by the guide surface  135   b , the center hole Ma of the medium M is guided to the base end  135   a , and thus the base end  135   a  is inserted through the center hole Ma of the medium M. That is, the center of the medium M to be held is positioned at the center of the holding portion  132  which is the pickup center. 
     At this time, when the end of the detection lever  201  of the medium detecting mechanism  200  mounted on the transport arm  36  comes in contact with the surface of the medium M, the detection lever  201  swings upward with the lift-down of the transport arm  36  and the detection lever  201  runs off from the detection area of the detector  202 , thereby turning on the detector  202  (ST 3 ) to detect the access state to the medium M. It is determined whether the destination of the transport arm  36  is the blank medium stacker  21  receiving plural mediums stacked therein or the medium tray  51  or the medium tray  41   a  receiving a single medium (ST 4 ). When the destination is the medium trays  41   a  and  51  of the drive and the printer, the driving motor is driven separately (ST 5 ) by adding pulse T2 to pulse T1 applied to the driving motor  37 , the driving motor is stopped (ST 7 ) by lifting down the transport arm  36  by a predetermined distance, and the holding claws  141  to  143  of the holding mechanism  130  mounted on the transport arm  36  are inserted into the center hole Ma of the medium M. 
     The mediums M are stacked in the blank medium stacker  21 . Since the stacked mediums M are in close contact with each other, an adhesive force may occur between the mediums M. 
     Accordingly, when the second medium M is adhered to the uppermost medium M, it is difficult to horizontally position the uppermost medium only by bringing the holding claws  141  to  143  into contact with the inner circumferential surface Mb of the center hole Ma of the medium. 
     Accordingly, in the medium transporting unit  31 , by applying a predetermined pressing force to the uppermost medium M from the top, the pressing force toward the lateral end of the medium M is applied by the guide surface  135   b  of the medium guide  133 , thereby satisfactorily moving and positioning the medium M laterally. 
     A relation between a position of the belt clip  112  of the transport arm  36  and a load on the medium M will be described. 
       FIG. 28  is a graph illustrating a relation between a down stroke of the belt clip of the transport arm and a load on the medium. 
     First, in a state where the holding portion of the transport arm  36  is in contact with the uppermost medium M (a state between A and B in  FIG. 28 ), when the driving motor  37  continues driving by further applying pulse T2 (ST 5 ), the belt clip  112  fixed to the timing belt  104  is lifted down against the urging force of the first tension spring  113  having a small spring force, the belt clip  112  goes down by a distance corresponding to the clearance S, and then the belt clip  112  comes in contact with the pressing lever  116  (state B in  FIG. 28 ). Accordingly, until the belt clip  112  comes in contact with the pressing lever  116  after the holding portion  132  comes in contact with the uppermost medium, the first elastic pressing force including the urging force of the first tension spring  113  having the small spring force is applied to the uppermost medium M (state between A and B in  FIG. 28 ). 
     When the driving motor  37  is further driven, the belt clip  112  further goes down. At this time, since the belt clip  112  is in contact with the pressing lever  116 , the lift-down force of the belt clip  112  is transmitted to the transport arm  36  to bend the transporting arm  36  and the bending force is applied as a pressing force to the uppermost medium M (state between B and C in  FIG. 28 ). 
     When the driving motor  37  is further driven (ST 5 ), the belt clip  112  goes down and stops (ST 7  and ST 8 ), and thus the bending force of the transport arm  36  is greater than the urging force of the second tension spring  119  having a great spring force (state C in  FIG. 28 ), the pressing lever  116  swings about a supporting point on the supporting plate  117  against the urging force of the second tension spring  119 . Accordingly, the second elastic pressing force obtained by adding the urging force of the second tension spring  119  to the urging force of the first tension spring  113  and the bending force of the transport arm  36  is applied to the uppermost medium M (states between C and E in  FIG. 28 ). 
     In the medium transporting unit  31  having the above-mentioned load characteristic, the driving motor  37  is stopped at a proper position (for example, position of D in  FIG. 28 ) in the state where the pressing force obtained by adding the urging force of the second tension spring  119  to the urging force of the first tension spring  113  and the bending force of the transport arm  36  is applied to the medium M (state between C and E in  FIG. 28 ). 
     As a result, among the stacked mediums M in the blank medium stacker  21 , a proper load (about 10 N) can be applied to the uppermost medium M. Accordingly, regardless of the adhesion to the second medium M, it is possible to satisfactorily move laterally and position the medium M by the use of the guide surface  135   b  of the medium guide  133 . 
     Even when the center position of the medium M runs off, it is possible to satisfactorily insert the medium guide  133  into the center hole Ma of the medium and to position the medium, by applying a load. 
     When the rigidity of the transport arm  36  is enhanced and the spring constant of the second tension spring  119  is increased, it is possible to obtain a necessary load by reducing the stroke of the belt clip  112  for generating the bending force of the transport arm  36  (state between B and C in  FIG. 28 ). 
     When the medium M is lifted up from the medium trays  41   a  and  51  of the medium drive  41  and the label printer  11  including only a single medium M, ST 6  is performed as the determination result whether the destination of the transport arm  36  is the blank medium stacker  21  or the medium tray  51  of the medium tray  41   a  receiving a single medium (ST 4 ) and only pulse T1 is thus applied to the driving motor  37  (ST 6 ). 
     In this case, the driving motor is stopped in the region (clearance S in  FIG. 7 ) where the belt clip  112  fixed to the timing belt  104  is lifted down against the urging force of the first tension spring  113  having a small spring force. The medium M can be held by the use of the holding mechanism  130  in the state (state between A and B in  FIG. 28 ) where the first elastic pressing force including the urging force of the first tension spring  113  having a small spring force is applied until the belt clip  112  comes in contact with the pressing lever  116  after the holding portion of the transport arm  36  comes in contact with the medium M. As a result, since the load applied on the medium trays  41   a  and  51  at the time of tacking out the medium M can be reduced, it is possible to suppress the overload due to the load on the medium trays  41   a  and  51 . 
     In this way, in a state where the second elastic pressing force is applied to the uppermost medium M in the blank medium stacker  21 , the holding claws  141  to  143  inserted into the center hole Ma of the medium M are made to move outward and are pressed on the inner circumferential surface Mb of the center hole Ma. 
     Specifically, first, when the electromagnetic solenoid  176  is turned off and the operation rod  176   a  thereof is made to protrude by action of the spring force, the swinging plate  161  connected to the operation rod  176   a  through the link  175  swings in the direction of R 1 . Accordingly, the other swinging plates  162  and  163  swing in the direction of R 1  by means of the tension of the tension coil spring  174 , similarly to the swinging plate  161 . As a result, the holding claws  141  to  143  move outward and the holding claws  141  to  143  are pressed on the inner circumferential surface Mb of the center hole of the medium M, thereby holding the medium M. 
     At this time, since the swinging plates  162  and  163  swing in the direction of R 1  by means of the tension of the tension coil spring  174  independently of the swinging plate  161 , the holding claws  141  to  143  also move outward in the radius direction independently of each other and are pressed on the inner circumferential surface Mb of the center hole Ma of the medium M. 
     Therefore, even when the center position of the uppermost medium M runs off from the pickup center, the holding claws  141  to  143  move outward independently and thus all the holding claws  141  to  143  come in contact with the inner circumferential surface Mb of the center hole Ma of the medium M, thereby satisfactorily preventing holding failure and the like. 
     In addition, the downward protruding length of the holding claws  141  to  143  is equal to or less than the thickness of the medium to be held. Accordingly, even when the center position of the second medium M runs off from that of the uppermost medium M, it is possible to prevent such a problem that the holding claws  141  to  143  come in contact with the edge of the center hole Ma of the second medium M to cause the holding failure. 
     When the medium M is held in this way, the held medium M is lifted up by lifting up the transport arm  36  in the state where the holding claws  141  to  143  move outward in the diameter direction. At this time, since the held uppermost medium M is satisfactorily held by all the holding claws  141  to  143 , it is possible to smoothly pick up the medium without any holding failure. 
     When the transport arm  36  moves up to pick up the medium M, the pressing lever  182  of the separation mechanism  131  swings in the direction of arrow R 3  in  FIG. 21  about the connection point  181  and thus the operation piece  183  protrudes to the outside of the medium guide  133 . 
     Therefore, even if the second medium M is lifted up by adhesion to the lifted uppermost medium M, the operation piece  183  of the pressing lever  182  comes in contact with the inner circumferential surface Mb of the center hole Ma of the second medium M to satisfactorily separate the second medium, thereby lifting up only the uppermost medium M. 
     As described above, in the medium transporting unit  31  according to the embodiment, the holding portion  132  of the transport arm  36  comes in contact with the medium M by selectively applying one of the first elastic pressing force and the second elastic pressing force greater than the first elastic pressing force to the medium M at the time of lifting down the transport arm  36 . As a result, it is possible to position the medium M by the use of the medium guide  133  with a proper pressing force depending on the receiving state of the medium M and to then hold the medium by the use of the holding mechanism  130 . 
     For example, when the pressing force is hardly necessary at the time of positioning and the single medium M received in the medium trays  41   a  and  51  of the drive  41  and the printer  11  which should be picked up with a small pressing force is positioned and held, the holding portion  132  can be pressed with the first elastic pressing force relatively small. When a positional error may be greatly caused and the uppermost medium M of the stacked mediums M in the medium stacker  21  and  22  which are closely adhered to the just-below medium M to generate an adhesive force is positioned and held, the holding portion  132  can be pressed on the medium M with the second elastic pressing force greater than the first elastic pressing force. Accordingly, it is possible to hold the medium M in the medium trays  41   a  and  51  of the drive  41  and the printer  11 , without causing any problem with the medium dray  41   a  and  51  due to the excessive pressing force. 
     Until the belt clip  112  as the lift member that is lifted up and down by the timing belt  104  comes in contact with the pressing lever  116 , the urging force of the first tension spring  113  can be used as the first elastic pressing force. From the state where the belt clip  112  comes in contact with the pressing lever  116  and the pressing lever  116  swings, the urging force of the first tension spring  113 , the bending force of the transport arm  36 , and the urging force of the second tension spring  119  can be easily and properly set as the second elastic pressing force. 
     By providing the second tension spring  119 , it is possible to prevent an excessive load from being applied to the medium in the state between C and E in  FIG. 28 . It is also possible to prevent an excessive load from being applied to the driving motor  37  and thus to employ a cheaper motor. 
     Since the contact surfaces  151   a  to  153   a  of the supporting pins  151  to  153  can urge using the stronger urging force of the second tension spring  119 , it is possible to improve the satisfactory holding by means of the satisfactory contact with the medium M. 
     In the medium stackers  21  and  22 , the uppermost medium M can be made to laterally slide and positioned by the use of the medium guide  133  against the adhesive force to the just-below medium M, thereby satisfactorily holding the medium by the use of the holding mechanism  130 . 
     Since the publisher  1  has the medium transporting unit  31  which can satisfactorily position and hold the medium M, it is possible to provide a processing apparatus with high reliability. 
     The invention may be modified in various forms without being limited to the above-mentioned embodiments. For example, the control of the driving motor  37  having a lift function in the medium transporting unit  31  is selected, after the detector  22  is turned on in  FIG. 29  to detect whether the stacker is a single tray. It may be determined that it is a tray when the transport arm is located at the home position and that it is the stacker when the transport arm  36  moves to the medium stackers  21  and  22 . Alternatively, the determination may be performed when the medium to be held is instructed before the transport arm  36  moves. 
     Although the timing belt has been used as the lift member, a lifting configuration using a rotating shaft on which a spiral groove is formed may be used. Although the holding mechanism has pressed the inner circumferential surface of the medium, a claw shape engaging with the rear surface or the edge portion of the rear surface through the center hole may be used, or the top surface of the medium may be held by suction. 
     Although the tension spring has been used to urge the transport arm  36 , a compression spring or a twisted coil spring may be used, but the tension spring is advantageous for management and assembly.

Technology Category: g