Patent Publication Number: US-2022234370-A1

Title: Recording apparatus capable of printing elastic medium

Description:
INCORPORATION BY REFERENCE 
     This application is based upon and claims the benefit of priority from the corresponding Japanese Patent Application No. 2021-011684 filed on Jan. 28, 2021, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     The present disclosure relates to a recording apparatus that prints elastic medium by an inkjet method. 
     There is known an inkjet textile printing apparatus that prints fabric by an inkjet method. The inkjet textile printing apparatus includes a sheet conveying portion that conveys a long recording sheet, an inkjet recording portion that ejects ink to the recording sheet conveyed by the sheet conveying portion to form an image, and a sheet collecting portion that collects the recording sheet on which the image is formed by the inkjet recording portion. 
     SUMMARY 
     A recording apparatus of the present disclosure includes a printing portion and a first conveying portion. The printing portion ejects liquid to print a medium having elasticity. The first conveying portion is disposed upstream of the printing portion in a conveying direction along which the medium is conveyed to the printing portion. The first conveying portion includes at least two conveying bodies disposed in the conveying direction and around which the medium is alternately wound. The conveying bodies each include a shaft extending in a width direction orthogonal to the conveying direction and a plurality of rollers rotatably supported by the shaft. The plurality of rollers are supported to be inclined outward with respect to the conveying direction from upstream to downstream in the conveying direction. 
     This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description with reference where appropriate to the accompanying drawings. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic side view of a recording apparatus according to an embodiment of the present disclosure. 
         FIG. 2  is a side view of a first conveying portion in the recording apparatus according to the embodiment of the present disclosure. 
         FIG. 3  is a perspective view of the first conveying portion in the recording apparatus according to the embodiment of the present disclosure. 
         FIG. 4  is a front view of first to third conveying bodies in the recording apparatus according to the embodiment of the present disclosure. 
         FIG. 5  is a partial front view of the first conveying body in the recording apparatus according to the embodiment of the present disclosure. 
         FIG. 6A  is a perspective view of a roller in the recording apparatus according to the embodiment of the present disclosure. 
         FIG. 6B  is a cross-sectional view of the roller in the recording apparatus according to the embodiment of the present disclosure. 
         FIG. 7  is a schematic front view of a medium conveyed in the first conveying portion in the recording apparatus according to the embodiment of the present disclosure. 
         FIG. 8A  is a perspective view of a modification of the roller in the recording apparatus according to the embodiment of the present disclosure. 
         FIG. 8B  is a cross-sectional view of the modification of the roller in the recording apparatus according to the embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The following describes a recording apparatus according to an embodiment of the present disclosure with reference to the accompanying drawings. 
     The overall configuration of a recording apparatus  1  will now be described with reference to  FIG. 1 .  FIG. 1  is a schematic side view of the recording apparatus  1 . The recording apparatus  1  prints a medium M such as fabric that stretches in longitudinal and transverse directions by an inkjet method. In  FIG. 1 , the left side on the page corresponds to the front side of the recording apparatus  1 . Fr, Rr, L, and R in the drawings respectively denote the front side, rear side, left side, and right side of the recording apparatus  1 . 
     The recording apparatus  1  includes a supply roller  3  around which the long medium M is wound, a printing portion  5  that prints the medium M supplied from the supply roller  3  by an inkjet method, a drying portion  7  that dries the medium M printed by the printing portion  5 , and a winding roller  9  that winds the medium M dried by the drying portion  7 . Furthermore, the recording apparatus  1  includes a first conveying portion  11  that conveys the medium M in a conveying direction from the supply roller  3  to the printing portion  5  and a second conveying portion  13  that conveys the medium M conveyed by the first conveying portion  11  to the drying portion  7  while keeping the medium M facing the printing portion  5 . 
     The supply roller  3  includes a rotation shaft  21  around which the medium M is wound to be attached and a motor (not shown) that rotates the rotation shaft  21  in a predetermined rotation direction. The motor rotates the rotation shaft  21  in the predetermined direction at a predetermined rotational speed to unwind the medium M from the rotation shaft  21  downstream in the conveying direction. 
     The printing portion  5  includes four recording heads  23 C,  23 M,  23 Y, and  23 K. The four recording heads  23 C,  23 M,  23 Y, and  23 K are supplied with ink of cyan, magenta, yellow, and black, respectively. The four recording heads  23 C,  23 M,  23 Y, and  23 K are aligned in the conveying direction and supported by a head housing  25  with their ejection ports facing downward. 
     The drying portion  7  includes a fan  27  and a belt conveying portion  29 . The fan  27  is disposed with its air outlet facing downward. The belt conveying portion  29  includes an endless belt wound around a drive roller and a driven roller. The belt conveying portion  29  is disposed such that the upper path of the endless belt faces the air outlet of the fan  27  with a predetermined space therebetween. 
     The winding roller  9  includes a rotation shaft  31  around which the medium M is wound to be collected and a motor (not shown) that rotates the rotation shaft  31  in a predetermined rotation direction. The motor rotates the rotation shaft  31  in the predetermined direction at a predetermined rotational speed to wind the medium M around the rotation shaft  31 . 
     It is difficult for a known textile printing apparatus to stably convey an elastic recording sheet such as fabric. Forming an image on an unstable recording sheet prevents a desired drawing performance from being achieved. By contrast, the recording apparatus  1  according to the embodiment of the present disclosure can perform textile printing while stably conveying an elastic medium as described below. 
     The following describes the first conveying portion  11  with reference to  FIGS. 2 and 3 .  FIG. 2  is a side view of the first conveying portion  11 , and  FIG. 3  is a perspective view of the first conveying portion  11 . 
     The first conveying portion  11  includes first to third conveying bodies  41 ,  42 , and  43 ; first to fourth tension rollers  51 ,  52 ,  53 , and  54 ; and a first conveying roller pair  57 . The medium M is wound around the first tension roller  51 , the second tension roller  52 , the third tension roller  53 , the first conveying body  41 , the second conveying body  42 , the third conveying body  43 , and the fourth tension roller  54  in this order from upstream to downstream in the conveying direction. 
     As shown in  FIG. 3 , the first and third tension rollers  51  and  53  and the first to third conveying bodies  41 ,  42 , and  43  are supported by a pair of left and right side plates  61 L and  61 R at both respective ends thereof. The pair of side plates  61 L and  61 R are connected by two stays  63  and supported by the housing (not shown) of the recording apparatus  1 . Both ends of the second tension roller  52  are supported by the housing. One end of the fourth tension roller  54  is supported by the right side plate  61 R, and another end is supported by the housing. 
     The following describes the first to third conveying bodies  41 ,  42 , and  43  with reference to  FIGS. 4 and 5  in addition to  FIGS. 2 and 3 .  FIG. 4  is a front view of the first to third conveying bodies  41 ,  42 , and  43 , and  FIG. 5  is a partial front view of the first conveying body  41 . 
     As shown in  FIG. 4 , the first to third conveying bodies  41 ,  42 , and  43  include first to third shafts  71 ,  72 , and  73 , respectively, extending in a width direction W (left-right direction) orthogonal to a conveying direction X (indicated as a direction parallel to the up-down direction in  FIG. 4  for convenience), and include first to third rollers  81 ,  82 , and  83  rotatably supported by the first to third shafts  71 ,  72 , and  73 , respectively. 
     The first to third rollers  81 ,  82 , and  83  respectively include five rollers. The five rollers of the first to third rollers  81 ,  82 , and  83  respectively include middle rollers  81 C,  82 C, and  83 C disposed in the middle in the width direction W; first left rollers  81 L 1 ,  82 L 1 , and  83 L 1  disposed to the left of the middle in the width direction W (on the outer side in the width direction W); second left rollers  81 L 2 ,  82 L 2 , and  83 L 2  disposed to the left of the first left rollers  81 L 1 ,  82 L 1 , and  83 L 1  (on the outer side in the width direction W); first right rollers  81 R 1 ,  82 R 1 , and  83 R 1  disposed to the right of the middle in the width direction W (on the outer side in the width direction W); and second right rollers  81 R 2 ,  82 R 2 , and  83 R 2  disposed to the right of the first right rollers  81 R 1 ,  82 R 1 , and  83 R 1  (on the outer side in the width direction W). Hereafter, for convenience, the first left rollers  81 L 1 ,  82 L 1 , and  83 L 1  may also be collectively referred to as first left rollers L 1 ; the second left rollers  81 L 2 ,  82 L 2 , and  83 L 2  may also be collectively referred to as second left rollers L 2 ; the first right rollers  81 R 1 ,  82 R 1 , and  83 R 1  may also be collectively referred to as first right rollers R 1 ; and the second right rollers  81 R 2 ,  82 R 2 , and  83 R 2  may also be collectively referred to as second right rollers R 2 . 
     The first left rollers L 1  and the first right rollers R 1  are symmetric to each other about the middle (middle rollers  81 C,  82 C, and  83 C) in the width direction W. Similarly, the second left rollers L 2  and the second right rollers R 2  are symmetric to each other about the middle in the width direction W. 
     In addition, the first and second left rollers L 1  and L 2  and the first and second right rollers R 1  and R 2  are supported to be inclined outward with respect to the conveying direction X from upstream to downstream in the conveying direction X. That is, the first and second left rollers L 1  and L 2  are inclined from the middle to the left in the width direction W from upstream to downstream in the conveying direction X, and the first and second right rollers R 1  and R 2  are inclined from the middle to the right in the width direction W from upstream to downstream in the conveying direction X. It is noted that the middle rollers  81 C,  82 C, and  83 C are supported to align in the conveying direction X. 
     Furthermore, the inclination angles of the first and second left rollers L 1  and L 2  and those of the first and second right rollers R 1  and R 2  relative to the conveying direction X (hereinafter simply referred to as “inclination angles”) increase as the rollers are located outward from the middle in the width direction W. That is, the inclination angle of the second left rollers L 2  is larger than the inclination angle of the first left rollers L 1 , and the inclination angle of the second right rollers R 2  is larger than the inclination angle of the first right rollers R 1 . As an example, as shown  FIG. 5 , the inclination angle α (absolute value) of the first left roller  81 L 1  adjacent to the middle in the width direction W is 8°, whereas the inclination angle β (absolute value) of the second left roller  81 L 2  on the outer side in the width direction W is 16°. Similarly, the inclination angle α (absolute value) of the first right roller  81 R 1  adjacent to the middle in the width direction W is 8°, whereas the inclination angle β (absolute value) of the second right roller  81 R 2  on the outer side in the width direction W is 16°. 
     Furthermore, as shown in  FIG. 4 , in each conveying body, the rollers are disposed at regular intervals in the width direction W, and the distances between two adjacent rollers gradually increase from upstream to downstream in the conveying direction X. That is, the distance between two adjacent first rollers  81  of the first conveying body  41  is the shortest, whereas the distance between two adjacent third rollers  83  of the third conveying body  43  is the longest. 
     As shown in  FIGS. 2 and 4 , the first to third conveying bodies  41 ,  42 , and  43  are disposed in the up-down direction with a predetermined space therebetween. In addition, as shown in  FIG. 2 , the first and third conveying bodies  41  and  43  are disposed at the same position in the front-rear direction, whereas the second conveying body  42  is disposed behind the first and third conveying bodies  41  and  43 . 
     In addition, as shown in  FIG. 2 , the top of the first conveying body  41  and the bottom of the second conveying body  42  are located at substantially the same height, and the top of the second conveying body  42  and the bottom of the third conveying body  43  are located at substantially the same height. Since the first to third conveying bodies  41 ,  42 , and  43  are disposed in this manner, when viewed from the front as shown in  FIG. 4 , the middle rollers  81 C,  82 C, and  83 C of the first to third conveying bodies  41 ,  42 , and  43 , respectively, are aligned in the conveying direction X. In addition, the first left rollers  81 L 1 ,  82 L 1 , and  83 L 1  are substantially aligned in a direction inclined at 8° to the left with respect to the conveying direction X, and the second left rollers  81 L 2 ,  82 L 2 , and  83 L 2  are substantially aligned in a direction inclined at 16° to the left with respect to the conveying direction X. In addition, the first right rollers  81 R 1 ,  82 R 1 , and  83 R 1  are substantially aligned in a direction inclined at 8° to the right with respect to the conveying direction X, and the second right rollers  81 R 2 ,  82 R 2 , and  83 R 2  are substantially aligned in a direction inclined at 16° to the right with respect to the conveying direction X. 
     Furthermore, as shown in  FIG. 2 , the third tension roller  53  is disposed behind the first conveying body  41  such that the top of the third tension roller  53  and the bottom of the first conveying body  41  are located at substantially the same height. In addition, the fourth tension roller  54  is disposed behind the third conveying body  43  such that the top of the fourth tension roller  54  is located slightly higher than the top of the third conveying body  43 . 
     The following describes the rollers with reference to  FIGS. 6A and 6B .  FIG. 6A  is a perspective view of the second left roller  81 L 2 , and  FIG. 6B  is a cross-sectional view of the second left roller  81 L 2 . Here, the second left roller  81 L 2  of the first conveying body  41  will be described. 
     The second left roller  81 L 2  includes a fixed member  91  fixed to the first shaft  71  and a rotating member  93  fitted on the fixed member  91 . The fixed member  91  includes a base portion  91   a  having a short columnar shape and a flange portion  91   b  extending radially from an edge of the outer peripheral surface of the base portion  91   a . The base portion  91   a  has a through-hole  91   c  through which the first shaft  71  is fitted. The axial direction A of the through-hole  91   c  is inclined at 16° in a predetermined direction with respect to the axial direction B of the base portion  91   a.    
     The rotating member  93  is an annular member having a predetermined width. The rotating member  93  is rotatably fitted on the base portion  91   a  so as to abut on the flange portion  91   b  at one face and to be retained to the fixed member  91  with a screw  51  at another face. 
     The axial direction A of the through-hole  91   c  is inclined at 16° with respect to the axial direction B of the base portion  91   a . Accordingly, when the first shaft  71  is fitted in the through-hole  91   c , the rotating member  93  is inclined at 16° with respect to the conveying direction X. That is, the second left roller  81 L 2  is inclined at 16° with respect to the conveying direction X. As described above, in the fixed member  91  of each second left roller L 2 , the axial direction A of the through-hole  91   c  is inclined at 16° in the predetermined direction with respect to the axial direction B of the base portion  91   a . In addition, in the fixed member  91  of each first left roller L 1 , the axial direction A of the through-hole  91   c  is inclined at 8° in the predetermined direction with respect to the axial direction B of the base portion  91   a . On the other hand, in the fixed member  91  of each first right roller R 1 , the axial direction A of the through-hole  91   c  is inclined at 8° in a direction opposite the predetermined direction with respect to the axial direction B of the base portion  91   a . In addition, in the fixed member  91  of each second right roller R 2 , the axial direction A of the through-hole  91   c  is inclined at 16° in the direction opposite the predetermined direction with respect to the axial direction B of the base portion  91   a . In the fixed member  91  of each of the middle rollers  81 C,  82 C, and  83 C, the axial direction A of the through-hole  91   c  is parallel to the axial direction B of the base portion  91   a.    
     The first to third rollers  81 ,  82 , and  83  of the first to third conveying bodies  41 ,  42 , and  43 , respectively, are disposed at predetermined positions along the first to third shafts  71 ,  72 , and  73 , respectively, such that the flange portions  91   b  are located inward in the width direction W. The base portions  91   a  are fixed to the first to third shafts  71 ,  72 , and  73  with fixing screws S 2 . 
     Returning to  FIG. 1 , the first conveying roller pair  57  includes a drive roller and a driven roller pressed against the drive roller. The drive roller is driven by a motor (not shown) to rotate in a predetermined direction, and the driven roller is rotated by the rotation of the drive roller. The drive roller is driven such that the speed at which the medium M is conveyed is slightly higher than the speed at which the medium M is unwound from the supply roller  3 . 
     The following describes the second conveying portion  13  with reference to  FIG. 1 . The second conveying portion  13  includes a conveyor belt  97  and a suction device  99 . The conveyor belt  97  is an endless belt having a large number of air intakes. The conveyor belt  97  is wound around a drive roller and a driven roller such that the upper path thereof faces the ejection ports of the four recording heads  23 C,  23 M,  23 Y, and  23 K with a predetermined space between. The suction device  99  is disposed in a hollow portion inside the conveyor belt  97  to face the printing portion  5  with the upper path of the conveyor belt  97  therebetween. The suction device  99  generates an air current flowing from above the conveyor belt  97  to the inside of the conveyor belt  97  through the air intakes to cause the medium M conveyed along the upper path of the conveyor belt  97  to adhere to the conveyor belt  97 . When the drive roller is driven to circulate the conveyor belt  97  in a predetermined direction (clockwise in  FIG. 1 ), the medium M adhering to the upper path of the conveyor belt  97  is conveyed downstream while facing the printing portion  5 . 
     Furthermore, as shown in  FIG. 1 , a second conveying roller pair  15  is disposed between the printing portion  5  and the drying portion  7 . The second conveying roller pair  15  includes a drive roller and a driven roller pressed against the drive roller. The drive roller is driven by a motor (not shown) to rotate, and the driven roller is rotated by the rotation of the drive roller. The drive roller rotates in synchronization with the drive roller of the first conveying roller pair  57  in the first conveying portion  11 . 
     The following describes a printing operation of the recording apparatus  1  having the above-described configuration with reference to  FIGS. 1 and 7 .  FIG. 7  is a schematic front view of the medium M conveyed in the first conveying portion  11 . 
     Upon the start of the printing operation, the supply roller  3 , the first conveying roller pair  57 , the winding roller  9 , and the like are driven by the motors to rotate, and the medium M is unwound from the supply roller  3  toward the first conveying portion  11  downstream in the conveying direction. The unwound medium M is wound around the first to third conveying bodies  41 ,  42 , and  43  via the first to third tension rollers  51 ,  52 , and  53 . 
     More specifically, as shown in  FIG. 2 , the medium M extends forward from the third tension roller  53  substantially in the horizontal direction. The medium M is then wound approximately halfway around the first conveying body  41  from the underside of the first conveying body  41  and extends backward substantially in the horizontal direction. The medium M is then wound approximately halfway around the second conveying body  42  from the underside of the second conveying body  42  and extends forward substantially in the horizontal direction. Finally, the medium M is wound approximately halfway around the third conveying body  43  from the underside of the third conveying body  43  and extends obliquely upward to the fourth tension roller  54 . 
     While the medium M is conveyed in the first conveying portion  11 , the medium M is in contact with the outer peripheral surfaces of the rollers (the outer peripheral surfaces of the rotating members  93 ) of the first to third conveying bodies  41 ,  42 , and  43 , and the rollers rotate relative to the corresponding shafts. As described above, the rollers are supported to be inclined outward from upstream to downstream in the conveying direction X. Accordingly, the medium M is guided outward from the middle in the width direction W along the outer peripheral surfaces of the rollers. That is, as shown in  FIG. 7 , the medium M is pulled outward in the width direction W and stretched in the width direction. It is noted that “stretching the medium M” refers not to smoothing down the medium M, but to extending the elastic medium M. That is, the medium M has a width greater than that in its natural state without wrinkles. When the medium M is pulled outward in the width direction W, the medium M tries to contract inward in the width direction W due to its elasticity. The force in a direction of contraction is applied to the flange portions  91   b  of the fixed members  91 . 
     Furthermore, the first conveying roller pair  57  is driven such that the speed at which the medium M is conveyed is slightly higher than the speed at which the medium M is unwound from the supply roller  3 . Accordingly, the medium M unwound from the supply roller  3  is also stretched in the conveying direction X between the supply roller  3  and the first conveying roller pair  57 . 
     The medium M is conveyed by the first conveying roller pair  57  to the second conveying portion  13  while being stretched in the width direction W and in the conveying direction X as described above. The medium M is conveyed downstream in the second conveying portion  13  while adhering to the upper path of the conveyor belt  97  by the suction device  99  as described above. While the medium M is conveyed, the recording heads  23 C,  23 M,  23 Y, and  23 K eject ink of respective colors corresponding to an image to be printed to record the image on the medium M. The medium M on which the image is recorded is dried in the drying portion  7  and then wound around the winding roller  9 . 
     As described above, according to the recording apparatus  1  of the present disclosure, the medium M is conveyed while being stretched in the conveying direction X and in the width direction W. Accordingly, the medium M such as elastic fabric can be printed (subjected to textile printing) in the printing portion  5  while being stably conveyed. Thus, the performance in printing elastic fabric can be enhanced. 
     Specifically, in the first conveying portion  11 , the first and second left rollers L 1  and L 2  and the first and second right rollers R 1  and R 2  of the conveying bodies are supported to be inclined outward with respect to the conveying direction X from upstream to downstream in the conveying direction X. Accordingly, the medium M is pulled outward in the width direction W and stretched in the width direction W. 
     Furthermore, the rollers on the outer side in the width direction W (the second left rollers L 2  and the second right rollers R 2 ) have a larger inclination angle than the rollers adjacent to the middle (the first left rollers L 1  and the first right rollers R 1 ). Accordingly, the medium M can be stretched evenly in the width direction W. Furthermore, the distances between two adjacent rollers increase downstream in the conveying direction X. Accordingly, the medium M can be stretched gradually and efficiently. It is noted that the distances between two adjacent rollers do not necessarily need to increase downstream in the conveying direction X. The distances between the rollers of the first to third conveying bodies  41 ,  42 , and  43  may be the same. 
     Furthermore, as shown in  FIG. 2 , the medium M is wound approximately halfway around the first to third conveying bodies  41 ,  42 , and  43 . Accordingly, the central angles θ of the contact surfaces between the medium M and the first to third conveying bodies  41 ,  42 , and  43  around the first to third shafts  71 ,  72 , and  73  respectively corresponding to the first to third conveying bodies  41 ,  42 , and  43  range from 170° to 180°. Increasing the areas of the contact surfaces between the medium M and the first to third conveying bodies  41 ,  42 , and  43  as much as possible in this manner enables stable conveyance of the medium M while the medium M is being stretched. It is noted that the number of conveying bodies is not limited to three and may be any number greater than or equal to two. However, as the number of conveying bodies increases, the medium M can be stretched in smaller increments and thus stretched more stably. In addition, the number of rollers of the conveying bodies is not limited to five. However, it is preferable that, in a case where the number is small, the width of the rollers be increased to increase the areas of the contact surfaces with the medium M. 
     The following describes a modification of the rollers with reference to  FIGS. 8A and 8B .  FIG. 8A  is a perspective view of the second left roller  81 L 2 , and  FIG. 8B  is a cross-sectional view of the second left roller  81 L 2 . Here, the second left roller  81 L 2  of the first conveying body  41  will be described. The other rollers have the same configuration. 
     The second left roller  81 L 2  includes a spherical bearing  101 , a rotating member  103 , a pair of washers  105 , a pair of supporting members  107 , and a plurality of (four in this example) ball plungers  109 . 
     The inner ring of the spherical bearing  101  is fitted on the first shaft  71 . The rotating member  103  is an annular member having a predetermined width and rotatably engages with the outer ring of the spherical bearing  101 . The pair of washers  105  are fixed to the outer ring of the spherical bearing  101  while holding the rotating member  103  from both sides in the width direction W. 
     The pair of supporting members  107  are disk-shaped members each having a shaft hole through which the first shaft  71  is placed. Each of the supporting members  107  has four screw holes  107   a  formed at the same central angle (90°) around the shaft hole to be parallel to the shaft hole. The pair of supporting members  107  are fixed to the first shaft  71  with fixing screws on both sides of the spherical bearing  101 . The pair of supporting members  107  are positioned such that the four screw holes  107   a  are symmetric about the first shaft  71  in the up-down direction and in the front-rear direction. 
     Two of the ball plungers  109  are respectively screwed into two (upper and lower) of the screw holes  107   a  in a supporting member  107 A (one of the supporting members  107  on the outer side in the width direction W) to be reciprocable in a direction from the supporting member  107 A to the rotating member  103  (inward in the width direction W). The distal ends of the ball plungers  109  abut on the corresponding washer  105 . The other two ball plungers  109  are respectively screwed into two (front and rear) of the screw holes  107   a  in a supporting member  107 B (the other supporting member  107  on the inner side in the width direction W) to be reciprocable in a direction from the supporting member  107 B to the rotating member  103  (outward in the width direction W). The distal ends of the ball plungers  109  abut on the corresponding washer  105 . 
     The two ball plungers  109  on the outer side are disposed such that the protruding length of the upper ball plunger  109  from the supporting member  107 A to the distal end thereof is shorter than the protruding length of the lower ball plunger  109  from the supporting member  107 A to the distal end thereof. In addition, the protruding lengths of the two inner ball plungers  109  from the supporting member  107 B to the distal ends thereof are equal and are approximately intermediate between the protruding lengths of the two outer ball plungers  109 . By setting the protruding lengths of the ball plungers  109  to their distal ends in this manner, the inclination angle of the rotating member  103  is set to a predetermined angle (for example, 16°) by the two outer ball plungers  109 , and the rotating member  103  is prevented from falling over by the two inner ball plungers  109 . 
     According to the modification, the inclination angle of the rotating member  103  (the inclination angle of the roller) can be adjusted by adjusting the protruding lengths of the two outer ball plungers  109  to their distal ends. Thus, the extensity of the medium M in the width direction W can be adjusted according to the elasticity and printing characteristics of the medium M. Specifically, the amount of extension can be increased by increasing the inclination angle. The ball plungers can be moved back and forth manually or automatically using motors. 
     Furthermore, the positions of the rollers in the width direction W can also be adjusted according to the width of the medium M by loosening the fixing screws and moving the pair of supporting members  107  and the spherical bearing  101  in the axial direction of the first shaft  71 . Even with the medium M of the same type, the medium M differs in the amount of expansion and contraction depending on the width thereof. Accordingly, it is preferable that the positions and the inclination angles of the rollers be adjusted according to the width of the medium M. 
     In addition, in the above-described embodiment, as shown in  FIGS. 6A and 6B , a friction member  95  may be affixed to the outer peripheral surface of each roller. The friction coefficient between the friction members  95  and the medium M is greater than the friction coefficient between the outer peripheral surfaces of the rollers and the medium M. As an example, the friction members  95  are abrasive paper with grid sizes between 40 and 100. In this case, the frictional force between the medium M and the rollers can be increased, and thus the medium M can be conveyed more stably. The friction members  95  may be formed from rubber or the like. Alternatively, the outer peripheral surfaces of the rollers may be roughened. 
     The present disclosure has been described by taking a specific embodiment as an example. However, the present disclosure is not limited in particular to the above-described embodiment. Various modifications can be made to the above-described embodiment by those skilled in the art within the scope and spirit of the present disclosure. 
     It is to be understood that the embodiments herein are illustrative and not restrictive, since the scope of the disclosure is defined by the appended claims rather than by the description preceding them, and all changes that fall within metes and bounds of the claims, or equivalence of such metes and bounds thereof are therefore intended to be embraced by the claims.