Patent Publication Number: US-8537415-B2

Title: Inkjet printer

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a 371 of international application of PCT application serial no. PCT/JP2009/051660, filed on Jan. 30, 2009. The entirety of each of the Above-mentioned patent applications is hereby incorporated by reference herein and made a part of this specification. 
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to an inkjet printer which performs printing on a printing medium in an elongated sheet shape. 
     2. Background Art 
     Conventionally, as an inkjet printer performing printing on a printing medium in an elongated sheet shape, an inkjet printer has been known which is structured so that a printing medium before printing is fed out by a feeding mechanism disposed on a rear side of a printer main body, ink is ejected while an inkjet head is relatively moved with respect to the printing medium to perform printing in the printer main body, and the printing medium on which printing has finished is wound by a winding mechanism disposed on a front side of the printer main body (see, for example, Patent Literature 1). In the inkjet printer described above, in order to appropriately feed out or wind up a printing medium without cockles and slackness, a tension applying mechanism which applies a predetermined tension to the printing medium may be provided on a feeding mechanism side or a winding mechanism side (see, for example, Patent Literatures 2 and 3). 
     A schematic structure of a conventional tension applying mechanism  200  is shown in  FIG. 8(   a ). The tension applying mechanism  200  is structured of a medium arm  203 , which is vertically swingable around a rotation shaft  204  that is perpendicular to a feeding direction of a printing medium “M”, and a tension bar  201  which is supported by a tip end part of the medium arm  203  and extended in the perpendicular direction. The medium arm  203  is swung downward depending on its own weight and slackness of the printing medium “M” and thus the tension bar  201  is abutted with the printing medium so that the printing medium is bent and a tension is applied to the printing medium “M”. Further, the tension applying mechanism  200  is arranged with a tension adjustment mechanism  300  which is structured of a ballast arm  301 , which is vertically swingable around the rotation shaft  204  and extended in a direction on an opposite side to the tension applying mechanism, and a ballast member  302  which is attached to a tip end of the ballast arm  301 . A tension which is applied to the printing medium “M” by the tension applying mechanism  200  is capable of being adjusted by a torque acting on the ballast arm  301  by the ballast member  302 . 
     [Patent Literature 1] Japanese Patent Laid-Open No. 2007-302468 
     [Patent Literature 2] Japanese Patent Laid-Open No. 2008-279621 
     [Patent Literature 3] Japanese Patent Laid-Open No. 2003-252501 
     SUMMARY OF THE INVENTION 
     Technical Problem 
     As shown in  FIG. 8(   a ), when the tension applying mechanism  200  and the tension adjustment mechanism  300  are disposed on both sides, i.e., on a feeding side and a winding side, the feeding side tension applying mechanism and the winding side tension applying mechanism are required to be largely separated from each other (with the distance “E”) in the front and rear direction so that both of the tension adjustment mechanisms  300  are not interfered with each other. Therefore, the feeding side tension applying mechanism and the winding side tension applying mechanism are projected in the front and rear direction and thus the size of the inkjet printer is increased. In order to prevent this problem, as shown in  FIG. 8(   b ), it is conceivable that the tension adjustment mechanism  300  is structured so that the ballast arm  301  is extended obliquely above. In this case, a distance between two tension applying mechanisms  200  can be narrowed to some extent in comparison with the above-mentioned case (distance “F” &lt; distance “E”). However, further space saving (compacting) of the tension applying mechanism  200  and the tension adjustment mechanism  300  is required. 
     Further, in the inkjet printer, printing is performed on various types of printing medium and thus the tension applying mechanism  200  is required to apply a tension which is suitable for each of the printing media. Therefore, the tension adjustment mechanism  300  is provided and the tension applying mechanism  200  is structured so that a tension applied to a printing medium is adjustable by changing a weight of the ballast member  302 . However, in order to cope with various types of printing medium, a structure is required in which a tension is capable of being adjusted in a further wider range. 
     In view of the problems described above, an objective of the present invention is to provide an inkjet printer in which, when a tension applying mechanism and a tension adjustment mechanism are provided on both sides, i.e., on a feeding side and a winding side, large space saving of the tension applying mechanism and the tension adjustment mechanism can be attained. Further, another objective of the present invention is to provide an inkjet printer in which a tension applied by a tension applying mechanism is adjustable in a further wider range. 
     Solution to Problem 
     In order to attain the above-mentioned objective, the present invention provides an inkjet printer including a printer main body which performs printing on a printing medium, a support body (for example, the support part  2  in the embodiment) which supports the printer main body, a medium feeding means for feeding out the printing medium in an elongated sheet shape toward the printer main body, a medium winding means for winding the printing medium which has been fed out by the medium feeding means and has been printed in the printer main body, a feeding side tension applying means which applies a tension to the printing medium which has been fed out by the medium feeding means and before reaching to the printer main body, and a winding side tension applying means which applies a tension to the printing medium which is fed out from the printer main body and before being wound by the medium winding means. The medium feeding means and the feeding side tension applying means are mounted on the support body on one side in a feeding direction of the printing medium with respect to the printer main body, and the medium winding means and the winding side tension applying means are mounted on the support body on the other side with respect to the printer main body. In addition, the feeding side tension applying means is provided with a feeding side tension adjustment mechanism which is structured of a feeding side ballast arm, which is extended toward the winding side tension applying means and mounted on the support body (for example, the rotation shaft support part  92  in the embodiment) so as to be vertically swingable around a rotation shaft perpendicular to the feeding direction of the printing medium, and a feeding side ballast member which is attached to a tip end of the feeding side ballast arm. The tension applied to the printing medium by the feeding side tension applying means can be adjusted by using a torque acting on the feeding side ballast arm by the feeding side ballast member. The winding side tension applying means is provided with a winding side tension adjustment mechanism which is structured of a winding side ballast arm, which is extended toward the feeding side tension applying means and mounted on the support body (for example, the rotation shaft support part  122  in the embodiment) so as to be vertically swingable around a rotation shaft perpendicular to the feeding direction of the printing medium, and a winding side ballast member which is attached to a tip end of the winding side ballast arm. The tension applied to the printing medium by the winding side tension applying means can be adjusted by using a torque acting on the winding side ballast arm by the winding side ballast member. The feeding side tension adjustment mechanism and the winding side tension adjustment mechanism are provided so as to displace from each other in the direction perpendicular to the feeding direction of the printing medium and are partly overlapped with each other in a side view where the feeding direction is a front direction. 
     Further, in order to attain the above-mentioned another objective, the present invention provides an inkjet printer including a printer main body which performs printing on a printing medium, a medium feeding means for feeding out the printing medium in an elongated sheet shape toward the printer main body, a medium winding means for winding the printing medium which has been fed out by the medium feeding means and has been printed in the printer main body, and a tension applying means which applies a tension to the printing medium which has been fed out by the medium feeding means and before being wound by the medium winding means. In addition, the tension applying means includes a tension applying mechanism which is provided with a tension arm (for example, the medium arms  93  and  123  in the embodiment) that is vertically swingable around a rotation shaft perpendicular to a feeding direction of the printing medium and in which a tip end of the tension arm swung downward by the own weight of the tension arm is abutted with the printing medium to apply the tension to the printing medium, a tension adjustment mechanism which is provided with a ballast arm that is vertically swingable around a rotation shaft perpendicular to the feeding direction and a ballast member that is attached to the ballast arm and in which the tension applied to the printing medium by the tension applying mechanism can be adjusted by using a torque acting on the ballast arm by the ballast member, and a switching mechanism (for example, the fixed rings  97  and  127 , and the arm side protruded parts  98   a  and  128   a  of the ballast arms  98  and  28  in the embodiment) which is capable of switching between a first state in which, when the tension arm is swung to one side from a predetermined swing angle, the tension arm is engaged with the ballast arm for being capable of adjusting the tension by the tension adjustment mechanism, and a second state in which, when the tension arm is swung to the other side from the predetermined swing angle, the tension arm is separated from the ballast arm so that the torque by the tension adjustment mechanism is not operated. 
     Advantageous Effects Of Invention 
     In the inkjet printer in accordance with the present invention, the feeding side tension applying means is provided with a feeding side tension adjustment mechanism which is structured of a feeding side ballast arm, which is extended toward the winding side tension applying means and mounted on the support body so as to be vertically swingable around a rotation shaft perpendicular to the feeding direction of the printing medium, and a feeding side ballast member which is attached to a tip end of the feeding side ballast arm. Further, the winding side tension applying means is provided with a winding side tension adjustment mechanism which is structured of a winding side ballast arm, which is extended toward the feeding side tension applying means and mounted on the support body so as to be vertically swingable around a rotation shaft perpendicular to the feeding direction of the printing medium, and a winding side ballast member which is attached to a tip end of the winding side ballast arm. In addition, the feeding side tension adjustment mechanism and the winding side tension adjustment mechanism are provided so as to displace from each other in the direction perpendicular to the feeding direction of the printing medium and are partly overlapped with each other in a side view where the feeding direction is a front direction. Therefore, in comparison with the conventional case shown in  FIGS. 8(   a ) and  8 ( b ), remarkable space saving (compacting) of the feeding side tension applying means and the winding side tension applying means can be attained. 
     Further, in the inkjet printer in accordance with another present invention, the tension applying means includes a tension applying mechanism in which a tip end of the tension arm swung downward by the own weight of the tension arm is abutted with the printing medium to apply the tension to the printing medium, a tension adjustment mechanism in which the tension applied to the printing medium by the tension applying mechanism can be adjusted by using a torque acting on the ballast arm by the ballast member, and a switching mechanism which is capable of switching between a first state in which, when the tension arm is swung to one side from a predetermined swing angle, the tension arm is engaged with the ballast arm for being capable of adjusting the tension by the tension adjustment mechanism, and a second state in which, when the tension arm is swung to the other side from the predetermined swing angle, the tension arm is separated from the ballast arm so that the torque by the tension adjustment mechanism is not operated. According to this structure, a first state where the tension is capable of being adjusted by utilizing a torque acting on the ballast arm by the ballast member and a second state where the tension arm is separated from the ballast arm so that the tension is applied by the own weight of the tension arm can be switched to each other. Therefore, the tension can be adjusted in further wider range in comparison with the conventional tension applying means. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       [ FIG. 1 ] 
         FIG. 1  is a side view showing an inkjet printer in accordance with the present invention. 
       [ FIG. 2 ] 
         FIG. 2  is a perspective view showing the inkjet printer which is viewed from a front side. 
       [ FIG. 3 ] 
         FIG. 3  is a front view showing a main structure of a printer main body which structures the inkjet printer. 
       [ FIG. 4 ] 
         FIG. 4  is a plan view showing structures of a feeding side tension applying means and a winding side tension applying means. 
       [ FIG. 5 ] 
         FIGS. 5(   a ) and  5 ( b ) are side views showing an operation of a feeding side tension applying means on an upper side with respect to an engagement start angle. 
       [ FIG. 6 ] 
         FIGS. 6(   a ) and  6 ( b ) are side views showing an operation of a feeding side tension applying means on a lower side with respect to an engagement start angle. 
       [ FIG. 7 ] 
         FIG. 7  is a schematic view showing swing ranges of medium arms which are engaged with the feeding side tension adjustment mechanism and the winding side tension adjustment mechanism. 
       [ FIG. 8 ] 
         FIGS. 8(   a ) and  8 ( b ) are side views showing structures of conventional tension applying means. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     A preferred embodiment of the present invention will be described below with reference to the accompanying drawings. As shown in  FIGS. 1 and 2 , an inkjet printer “P” in accordance with the present invention is structured of a printer main body  1  which performs printing on a printing medium “M”, a support part  2  which supports the printer main body  1  at a height position where working is easily performed, a feeding device  3  for feeding out the printing medium “M” in an unprinted state to the printer main body  1 , and a winding device  4  for winding the printing medium “M” on which printing has been finished. In the following description, directions in the drawings indicated by the arrows of front and rear, right and left, upper and lower are receptively referred to as a front and rear direction, a right and left direction and an upper and lower direction for convenience of description. 
     First, the printer main body  1  will be briefly described below with reference to  FIG. 3  which shows a main structure of the printer main body  1 . The printer main body  1  is mainly structured of a body  10  which is a mounting base for respective units, a platen  20  which supports a printing medium “M”, a medium moving mechanism  30  which moves the printing medium “M” supported on the platen  20  in a front and rear direction, a carriage  40  which is located above the platen  20  and is movably supported in a right and left direction, a carriage moving mechanism  50  which relatively moves the carriage  40  in the right and left direction with respect to the printing medium “M” that is supported by the platen  20 , a plurality of inkjet heads  60  which are fixed to and supported by the carriage  40 , and a printing controller  70  which controls the drives of the respective moving mechanisms  30  and  50 , ink ejection from the inkjet heads  60  and the like. 
     The body  10  is provided with a main body frame  11  comprised of a lower frame  11 L, which is supported by right and left supporting legs  2   a  structuring the support part  2  and on which the platen  20  is mounted, and an upper frame  11 U on which a support structure for the carriage  40  is mounted. A medium passing part  15  formed in a laterally long window shape is formed between the upper frame  11 U and the lower frame  11 L so that a printing medium “M” is capable of passing through in the front and rear direction. The body  10  is surrounded by a front cover  13   a  which covers a center part of the main body frame  11  and side covers  13   b  which cover the right and left sides and is structured in a laterally long rectangular box-like shape as a whole. 
     The platen  20  is located at a center part in the right and left direction of the body  10  and provided over the front and rear sides of the medium passing part  15 . The platen  20  is structured of a main platen  22 , which is formed with a support face for horizontally supporting the printing medium “M” at a printing part (printing region) where the inkjet heads  60  are moved in the right and left direction to perform printing, a rear platen  21  which is extended backward from the main platen  22  and provided on a rear face side of the body  10 , and a front platen  23  which is extended forward from the main platen  22  and provided on a front face side of the body  10 . A rear end side of the rear platen  21  and a front end side of the front platen  23  are respectively extended downward in a smooth curved shape. A printing medium “M” which is fed out from the feeding device  3  and fed into the platen  20  is smoothly moved through respective upper faces of the rear platen  21 , the main platen  22  and the front platen  23  in this order and then, the printing medium “M” is fed out from the front platen  23  and wound by the winding device  4 . 
     The support face of the main platen  22  is formed with a large number of suction holes whose diameter is around several millimeters and a decompression chamber  25  which is capable of being set in a negative pressure is provided on a lower side of the support face. The printing medium “M” is sucked and held at the printing part by setting the decompression chamber  25  in a negative pressure and the position of the printing medium “M” is not displaced during printing. 
     The medium moving mechanism  30  is structured of a feed roller  31  formed in a cylindrical tube shape, which is rotatably provided around a rotation shaft extended in the right and left direction and disposed so that its upper peripheral face is exposed from the support face of the main platen  22 , a roller drive motor  33  for rotatably driving the feed roller  31 , a timing belt  32  which is stretched over a driven pulley coupled to a shaft end of the feed roller  31  and a drive pulley coupled to a shaft end of the roller drive motor  33 , and a plurality of roller assemblies  35  which are provided with a pinch roller  36  that is rotatable in the front and rear direction and are disposed on an upper side of the feed roller  31  with a predetermined interval in the right and left direction. 
     The roller assembly  35  is structured so that the pinch roller  36  is capable of being displaced between a clamp position where the pinch roller  36  is elastically engaged with the feed roller  31  and an unclamp position where the pinch roller  36  is separated to an upper side of the feed roller  31 . When the feed roller  31  is turned in a state that the roller assemblies  35  are set in the clamp position and a printing medium “M” is sandwiched between the upper and lower rollers  36  and  31 , the printing medium “M” is carried in the front and rear direction by a feeding amount corresponding to a turning angle of the feed roller  31 , in other words, by a feeding amount corresponding to a drive control signal which is outputted from the printing controller  70  to the roller drive motor  33 . 
     The carriage  40  is supported to be movable in the right and left direction by the guide rail  45 , which is attached to the upper frame  11 U and extended in the right and left direction in parallel to the feed roller  31 . The guide rail  45  is a support rail of a linear bearing. The carriage  40  is fixed to a slide block which is fitted to the guide rail  45  so as to be slidably supported in the right and left direction and the carriage  40  is moved in the right and left direction by the carriage moving mechanism  50 . 
     The carriage moving mechanism  50  is comprised of a drive pulley  51  and a driven pulley  52  which are provided in the vicinities of right and left side ends of the guide rail  45 , a carriage drive motor  53  for rotationally driving the drive pulley  51 , and a timing belt  55  which is stretched over the drive pulley  51  and the driven pulley  52 . The carriage  40  is connected and fixed to the timing belt  55 . Rotation of the carriage drive motor  53  is controlled by the printing controller  70  and the carriage  40  is slidably moved (moved in a reciprocated manner) in the right and left direction by a feeding amount corresponding to a drive control signal which is outputted from the printing controller  70  to the carriage drive motor  53 . 
     The inkjet head  60  is formed on its under face with a large number of nozzles for ejecting ink droplets and the inkjet head  60  is fixed and supported by the carriage  40  so that its under face (nozzle face) is separated from a printing medium “M” with a predetermined gap space (distance). Various types of arrangement structure of the inkjet head  60  have been proposed and an appropriate structure may be utilized. In this embodiment, a head structure is adopted in which inkjet heads  60  for four colors (for example, black, cyan, magenta and yellow) are juxtaposeqlly disposed in the right and left direction. Further, the carriage  40  is capable of moving upward and downward by a carriage up-and-down mechanism not shown and a gap between the nozzle face of the inkjet heads  60  and a printing medium “M” can be adjusted depending on a surface condition of the printing medium “M” or the like by utilizing the carriage up-and-down mechanism. 
     The printing controller  70  controls the drive of the roller drive motor  33  in the medium moving mechanism  30  to intermittently feed forward and position a printing medium “M” which is supported on the platen  20  and, in addition, synchronously controls the drive of the carriage drive motor  53  in the carriage moving mechanism  50  and ink ejection from the nozzles of the respective inkjet heads  60  to form image such as a character or a pattern corresponding to a printing program on the printing medium “M”. In this case, a printing medium “M” in an unprinted state is fed out to the platen  20  by the feeding device  3  depending on a feeding amount of the printing medium “M” on the platen  20  by the medium moving mechanism  30 , and the printing medium “M” that printing has finished and fed out from the platen  20  is wound by the winding device  4 . 
     Next, the feeding device  3  and the winding device  4  will be described below. The feeding device  3  is, as shown in  FIG. 1 , provided on the rear side of the supporting part  2 . The feeding device  3  is structured of a medium feeding means  80 , which supports a feeding shaft  6  in a tube-like shape (see  FIG. 2 ) around which a printing medium “M” in an unprinted state is wound and rotates the feeding shaft  6  for feeding out the printing medium “M”, a feeding side tension applying mechanism  90  which applies a tension to the printing medium “M” which is fed out by the medium feeding means  80  and before being fed into the platen  20 , and a feeding controller  100  which controls a feeding amount of the printing medium “M” by the medium feeding means  80 . 
     The medium feeding means  80  is structured of a bar-shaped support shaft  81 , which is inserted into the feeding shaft  6  and integrally rotatable together with the feeding shaft  6 , shaft support parts  82  which are disposed at intermediate parts on the rear sides of the right and left supporting legs  2   a  for rotationally and detachably supporting the support shaft  81 , and a shaft drive mechanism  85  which is provided in the inside of the left side shaft support part  82  for rotationally driving the support shaft  81 . The shaft drive mechanism  85  is, for example, structured of a drive motor, a timing belt which is stretched over an output shaft of the drive motor and an end part of the support shaft  81 , and the like. The shaft drive mechanism  85  rotationally drives the support shaft  81  depending on a drive control signal inputted from the feeding controller  100 . A printing medium “M” in an unprinted state which is supported between the right and left shaft support parts  82  by the support shaft  81  is fed out toward the platen  20  (rear platen  21 ) with a feeding amount (at a feeding speed) corresponding to a rotation amount (rotation speed) of the support shaft  81 . 
     The feeding side tension applying means  90  is, as shown in  FIGS. 1 and 4 , structured of a feeding side tension applying mechanism  95 , a feeding side tension adjustment mechanism  96  and a fixed ring  97 . The feeding side tension applying mechanism  95  is structured of a cylindrical bar-shaped tension bar  91 , which is transversely abutted with the printing medium “M” in the right and left direction, rotation shaft support parts  92  which are disposed on bottom parts  2   b  of the right and left supporting legs  2   a , a feeding side rotation shaft  94  which is rotationally supported by the right and left rotation shaft support parts  92 , and a pair of right and left medium arms  93  whose base end parts are fixed to end parts of the feeding side rotation shaft  94  and whose tip end parts rotationally support end parts of the tension bar  91 . The feeding side tension adjustment mechanism  96  is structured of a feeding side ballast arm  98  whose base end part is rotationally supported by the feeding side rotation shaft  94  and whose tip end part is detachably mounted with a feeding side ballast member  99 . The fixed ring  97  is fixed to the feeding side rotation shaft  94  and integrally turned with the feeding side rotation shaft  94 . 
     As described above, the base end parts of the medium arms  93  are respectively fixed to the right and left end parts of the feeding side rotation shaft  94  and the medium arms  93  are vertically swingable together with turning of the feeding side rotation shaft  94  with their base end parts as a center side. Further, the medium arms  93  are structured to be swung downward by their own weights so that the tension bar  91  supported at their tip end parts is abutted with a printing medium “M” which is fed out from the feeding shaft  6  and before reaching to the platen  20 . In this embodiment, a swing angle detecting part (not shown) for detecting a swing angle of the medium arm  93 , i.e., a height position of the tension bar  91  is disposed in the vicinity of the base end part of the medium arm  93 . A detection signal which is detected by the swing angle detecting part is outputted to the feeding controller  100 . 
     The fixed ring  97  is integrally turned with the feeding side rotation shaft  94  extended in the right and left direction, in other words, turned depending on swinging of the medium arm  93  which is fixed to the feeding side rotation shaft  94 . The fixed ring  97  is formed with a ring side protruded part  97   a  which is protruded in a direction perpendicular to the feeding side rotation shaft  94 . The ring side protruded part  97   a  is turned in a clockwise direction in a side view from the left side depending on a downward swing of the medium arm  93 . When the medium arm  93  is reached to a predetermined swing angle (hereinafter, referred to as an engagement start angle), the ring side protruded part  97   a  begins to abut with an under face of an arm side protruded part  98   a  of the feeding side ballast arm  98  described below (see  FIG. 5(   b )). A state where the ring side protruded part  97   a  is abutted with the arm side protruded part  98   a  is referred to as an engagement state of the fixed ring  97  with the feeding side ballast arm  98 , which will be described below. 
     A base end part of the feeding side ballast arm  98  is turnably supported by the feeding side rotation shaft  94  so as to be adjacent to the fixed ring  97  and the feeding side ballast arm  98  is formed to extend from the base end part to the front side so as to straddle and across the winding side rotation shaft  124  described below from the underside. The feeding side ballast arm  98  is provided so as to displace in the right and left direction (direction perpendicular to the feeding direction of a printing medium “M”) from the winding side ballast arm  128  described below (see  FIG. 4 ) and a part of the feeding side ballast arm  98  is disposed so as to overlap with the winding side ballast arm  128  when viewed from the side face (see  FIG. 1 ). The feeding side ballast member  99  which is attached to the tip end part of the feeding side ballast arm  98  is located on a straight extended line which is connected between the feeding side rotation shaft  94  and the tension bar  91  in the side view when the fixed ring  97  and the feeding side ballast arm  98  are engaged with each other. The feeding side ballast member  99  is structured of a plurality of weight members which are respectively detachable at the tip end part of the feeding side ballast arm  98 . The weight of the feeding side ballast member  99  can be changed by changing the number of the weight members. 
     An arm side protruded part  98   a  which is protruded to the fixed ring  97  side is formed in the vicinity of the base end part of the feeding side ballast arm  98 . When the medium arm  93  becomes to be located at the engagement start angle as described above, the ring side protruded part  97   a  of the fixed ring  97  is abutted with the arm side protruded part  98   a  and the fixed ring  97  and the feeding side ballast arm  98  become in an engaging state. In the engaging state, in other words, when the medium arm  93  is swung on a lower side relative to the engagement start angle, the feeding side ballast arm  98  is vertically swung with its base end part (feeding side rotation shaft  94 ) as a center depending on swinging of the medium arm  93  (in conjunction with the medium arm  93 ) (see  FIG. 6(   a )). On the other hand, in a non-engaging state, in other words, when the medium arm  93  is swung on an upper side relative to the engagement start angle, the feeding side ballast arm  98  is abutted with a bottom part  2   b  of the supporting leg  2   a  to be in a stationary state (see  FIGS. 5(   a ) and  5 ( b )). 
     When the medium arm  93  is swung to a lower position than the engagement start angle to reach to a predetermined swing angle (hereinafter, referred to as a lower limit swing angle), a tip end of the medium arm  93  is abutted with a stopper member  2   c  provided in the bottom part  2   b  and a further downward swing of the medium arm  93  is restricted (see  FIG. 6(   b )). At this time, the feeding side ballast arm  98  and the winding side rotation shaft  124  are not abutted with each other. 
     In the feeding side tension applying means  90  which is structured as described above, the medium arm  93  is swung downward by the own weights of the tension bar  91  and the right and left medium arms  93  depending on a length of the printing medium “M” from the feeding shaft  6  before reaching to the platen  20  (hereinafter, referred to as slackness on the feeding side of the printing medium “M”) and the tension bar  91  is abutted with an inner side of the printing medium “M” to bend the printing medium “M”. In this manner, a tension corresponding to a height position of the tension bar  91 , i.e., a swing angle of the medium arm  93  is applied to the printing medium “M” in a direction opposite to the feeding direction. 
     In this case, when the medium arm  93  is swung on a lower side relative to the engagement swing angle (swing range “B” shown in  FIG. 7 ), the fixed ring  97  and the feeding side ballast arm  98  are engaged with each other and the feeding side ballast arm  98  is interlocked with the medium arm  93 . Therefore, a tension applied to the printing medium “M” can be adjusted by using a torque acting on the feeding side ballast arm  98  by the feeding side ballast member  99  (tension is reduced in comparison with the above-mentioned case). In this case, a tension suitable for the printing medium “M” to be printed can be applied to the printing medium “M” by changing the weight of the feeding side ballast member  99  depending on characteristics of the printing medium “M” (hardness and the like). Further, the feeding side ballast member  99  is disposed on one straight line formed with the tension bar  91  and the feeding side rotation shaft  94  in the side view through the feeding side ballast arm  98  and thus the weight of the feeding side ballast member  99  can be efficiently acted on the tension which is applied to the printing medium “M”. 
     On the other hand, when the medium arm  93  is swung on an upper side relative to the engagement start angle (swing range “A” shown in  FIG. 7 ), the fixed ring  97  and the feeding side ballast arm  98  are not engaged with each other. Therefore, the medium arm  93  is separated from the feeding side ballast arm  98  and thus a tension by the own weights of the tension bar  91  and the medium arms  93  is applied to the printing medium “M”. 
     The feeding controller  100  is, as shown in  FIGS. 1 and 4 , disposed in the inside of the left side rotation shaft support part  92 . The feeding controller  100  controls the drive of the shaft drive mechanism  85  in the medium feeding means  80  to feed out a printing medium “M” supported by the support shaft  81  with a predetermined feeding amount based on a feeding amount of the printing medium “M” on the platen  20  by the medium moving mechanism  30  (see  FIG. 3 ). Further, the feeding controller  100  controls the feeding amount so that a swing angle of the medium arm  93  is maintained in a predetermined swing range. The predetermined swing range is capable of being set arbitrarily and, for example, when the swing range is set in the swing range “B”, a tension applied to the printing medium “M” can be always set in an adjustable state by the feeding side tension adjustment mechanism  96 . 
     The winding device  4  is, as shown in  FIG. 1 , provided on the front side of the supporting part  2 . The winding device  4  is structured of a medium winding means  110 , which supports a winding shaft  8  in a tube-like shape (see  FIG. 2 ) around which the printing medium “M” after having been printed is wound and rotates the winding shaft  8  for winding the printing medium “M”, a winding side tension applying means  120  which applies a tension to the printing medium “M” which is fed out from the platen  20  and before being wound by the medium winding means  110 , and a winding controller  130  which controls a winding amount of the printing medium “M” by the medium winding means  110 . In this embodiment, the winding device  4  is basically structured to be similar to the feeding device  3 . 
     The medium winding means  110  is structured of a bar-shaped support shaft  111 , which is inserted into the winding shaft  8  and integrally rotatable together with the winding shaft  8 , shaft support parts  112  which are disposed at intermediate parts on the front sides of the right and left supporting legs  2   a  for rotationally and detachably supporting the support shaft  111 , and a shaft drive mechanism  115  which is provided in the inside of the left side shaft support part  112  for rotationally driving the support shaft  111 . The shaft drive mechanism  115  is, for example, structured of a drive motor, a timing belt which is stretched over an output shaft of the drive motor and an end part of the support shaft  111 , and the like. The shaft drive mechanism  115  rotationally drives the support shaft  111  depending on a drive control signal inputted from the winding controller  130 . The printing medium “M” having been printed which is fed out from the platen  20  (front platen  23 ) is wound around the winding shaft  8  that is supported between the right and left shaft support parts  112  through the support shaft  111  with a winding amount (at a winding speed) corresponding to a rotation amount (rotation speed) of the support shaft  111 . 
     The winding side tension applying means  120  is, as shown in  FIGS. 1 and 4 , structured of a winding side tension applying mechanism  125 , a winding side tension adjustment mechanism  126  and a fixed ring  127 . The winding side tension applying mechanism  125  is structured of a cylindrical bar-shaped tension bar  121 , which is transversely abutted with the printing medium “M” in the right and left direction, rotation shaft support parts  122  which are disposed on bottom parts  2   b  of the right and left supporting legs  2   a , a winding side rotation shaft  124  which is rotationally supported by the right and left rotation shaft support parts  122 , and a pair of right and left medium arms  123  whose base end parts are fixed to end parts of the winding side rotation shaft  124  and whose tip end parts rotationally support end parts of the tension bar  121 . The winding side tension adjustment mechanism  126  is structured of a winding side ballast arm  128  whose base end part is rotationally supported by the winding side rotation shaft  124  and whose tip end part is detachably mounted with a winding side ballast member  129 . The fixed ring  127  is fixed to the winding side rotation shaft  124  and integrally turned with the winding side rotation shaft  124 . 
     As described above, the base end parts of the medium arms  123  are respectively fixed to the right and left end parts of the winding side rotation shaft  124  and the medium arms  123  are vertically swingable together with turning of the winding side rotation shaft  124  with their base end parts as a center side. Further, the medium arms  123  are structured to be swung downward by their own weights so that the tension bar  121  supported at their tip end parts is abutted with the printing medium “M” which is fed out from the platen  20  and before being wound by the winding shaft  8 . In this embodiment, a swing angle detecting part (not shown) for detecting a swing angle of the medium arm  123 , i.e., a height position of the tension bar  121  is disposed in the vicinity of the base end part of the medium arm  123 . A detection signal which is detected by the swing angle detecting part is outputted to the winding controller  130 . 
     The fixed ring  127  is integrally turned with the winding side rotation shaft  124  extended in the right and left direction, in other words, turned depending on swinging of the medium arm  123  which is fixed to the winding side rotation shaft  124 . The fixed ring  127  is formed with a ring side protruded part (not shown) which is protruded in a direction perpendicular to the winding side rotation shaft  124 . The ring side protruded part is turned in a counterclockwise direction in a side view from the left side depending on a downward swing of the medium arm  123 . When the medium arm  123  is reached to a predetermined swing angle (hereinafter, referred to as an engagement start angle), the ring side protruded part begins to abut with an under face of an arm side protruded part  128   a  of the winding side ballast arm  128  described below. A state where the ring side protruded part is abutted with the arm side protruded part  128   a  is referred to as an engagement state of the fixed ring  127  with the winding side ballast arm  128 , which will be described below. 
     A base end part of the winding side ballast arm  128  is turnably supported by the winding side rotation shaft  124  so as to be adjacent to the fixed ring  127  and the winding side ballast arm  128  is formed to extend from the base end part to the rear side so as to straddle and across the feeding side rotation shaft  94  from the underside. The winding side ballast arm  128  is provided so as to displace in the right and left direction (direction perpendicular to the feeding direction of the printing medium “M”) from the feeding side ballast arm  98  (see  FIG. 4 ) and a part of the winding side ballast arm  128  is disposed so as to overlap with the feeding side ballast arm  98  when viewed from the side face (see  FIG. 1 ). The winding side ballast member  129  which is attached to the tip end part of the winding side ballast arm  128  is located on a straight extended line which is connected between the tension bar  121  and the winding side rotation shaft  124  in the side view when the fixed ring  127  and the winding side ballast arm  128  are engaged with each other. The winding side ballast member  129  is, similarly to the feeding side ballast member  99 , structured of a plurality of weight members which are respectively detachable at the tip end part of the winding side ballast arm  128 . The weight of the winding side ballast member  129  can be changed by changing the number of the weight members. 
     An arm side protruded part  128   a  which is protruded to the fixed ring  127  side is formed in the vicinity of the base end part of the winding side ballast arm  128 . When the medium arm  123  becomes to be located at the engagement start angle as described above, the ring side protruded part of the fixed ring  127  is abutted with the arm side protruded part  128   a  and the fixed ring  127  and the winding side ballast arm  128  become in an engaging state. In the engaging state, in other words, when the medium arm  123  is swung on a lower side relative to the engagement start angle, the winding side ballast arm  128  is vertically swung with its base end part (winding side rotation shaft  124 ) as a center depending on swinging of the medium arm  123  (in conjunction with the medium arm  123 ). On the other hand, in a non-engaging state, in other words, when the medium arm  123  is swung on an upper side relative to the engagement start angle, the winding side ballast arm  128  is abutted with a bottom part  2   b  of the supporting leg  2   a  to be in a stationary state. 
     When the medium arm  123  is swung to a lower position than the engagement start angle to reach to a predetermined swing angle (hereinafter, referred to as a lower limit swing angle), a tip end of the medium arm  123  is abutted with a stopper member  2   c  provided in the bottom part  2   b  and a further downward swing of the medium arm  123  is restricted. At this time, the winding side ballast arm  128  and the feeding side rotation shaft  94  are not abutted with each other. 
     In the winding side tension applying means  120  which is structured as described above, the medium arm  123  is swung downward by the own weights of the tension bar  121  and the right and left medium arms  123  depending on a length of the printing medium “M” from the platen  20  before being wound by the winding shaft  8  (hereinafter, referred to as slackness on the winding side of the printing medium “M”) and the tension bar  121  is abutted with an inner side of the printing medium “M” to bend the printing medium “M”. In this manner, a tension corresponding to a height position of the tension bar  121 , i.e., a swing angle of the medium arm  123  is applied to the printing medium “M” in the feeding direction. 
     In this case, when the medium arm  123  is swung on a lower side relative to the engagement swing angle (swing range “D” shown in  FIG. 7 ), the fixed ring  127  and the winding side ballast arm  128  are engaged with each other and the winding side ballast arm  128  is interlocked with the medium arm  123 . Therefore, a tension applied to the printing medium “M” can be adjusted by using a torque acting on the winding side ballast arm  128  by the winding side ballast member  129  (tension is reduced in comparison with the above-mentioned case). In this case, a tension suitable for the printing medium “M” to be printed can be applied to the printing medium “M” by changing the weight of the winding side ballast member  129  depending on types of the printing medium “M”. Further, the winding side ballast member  129  is disposed on one straight line formed with the tension bar  121  and the winding side rotation shaft  124  in the side view through the winding side ballast arm  128  and thus the weight of the winding side ballast member  129  can be efficiently acted on the tension which is applied to the printing medium “M”. 
     On the other hand, when the medium arm  123  is swung on an upper side relative to the engagement start angle (swing range “C” shown in  FIG. 7 ), the fixed ring  127  and the winding side ballast arm  128  are not engaged with each other. Therefore, the medium arm  123  is separated from the winding side ballast arm  128  and thus a tension by the own weights of the tension bar  121  and the medium arms  123  is applied to the printing medium “M”. 
     The winding controller  130  is, as shown in  FIGS. 1 and 4 , disposed in the inside of the left side rotation shaft support part  122 . The winding controller  100  controls the drive of the shaft drive mechanism  115  in the medium winding means  110  to wind the printing medium “M” supported by the support shaft  111  with a predetermined winding amount based on a feeding amount of the printing medium “M” on the platen  20  by the medium moving mechanism  30  (see  FIG. 3 ). Further, the winding controller  130  controls the winding amount so that a swing angle of the medium arm  123  is maintained in a predetermined swing range. The predetermined swing range is capable of being set arbitrarily and, for example, when the swing range is set in the swing range “D”, a tension applied to the printing medium “M” can be always set in an adjustable state by the winding side tension adjustment mechanism  126 . 
     In the feeding side tension applying means  90  and the winding side tension applying means  120  which are structured as described above, the feeding side tension adjustment mechanism  96  (feeding side ballast arm  98 ) and the winding side tension adjustment mechanism  126  (winding side ballast arm  128 ) are provided so as to be displaced from each other in the direction (right and left direction) perpendicular to the feeding direction of the printing medium “M” and disposed so as to be partly overlapped with each other in the side view. Therefore, in comparison with the conventional feeding side and winding side tension applying means shown in  FIGS. 8(   a ) and  8 ( b ), the spaces for the feeding side tension applying means  90  and the winding side tension applying means  120  are largely reduced (their sizes can be remarkably reduced). 
     Further, depending on the swing angles of the medium arms  93  and  123 , a state where the medium arms  93  and  123  are separated from the ballast arms  98  and  128  and tensions are applied to the printing medium “M” by the own weights of the tension bars  91  and  121  and the medium arms  93  and  123  can be switched to another state where the ballast arms  98  and  128  are moved in conjunction with the medium arms  93  and  123  so that tensions applied to the printing medium “M” are capable of being adjusted by utilizing torques acting on the ballast arms  98  and  128  through the ballast members  99  and  129 , and vice versa. Accordingly, the tension can be adjusted in further wider range in comparison with the conventional tension applying means.