Patent Publication Number: US-6981766-B2

Title: Ink-jet printer

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an ink-jet printer that ejects ink onto a printing medium to perform printing. 
     2. Description of Related Art 
     Some ink-jet printers perform printing by ejecting ink onto a paper as a printing medium from a printing head that reciprocates perpendicularly to a paper conveyance direction. It is important, from the viewpoint of printing quality, to ensure flatness of the paper in a print region confronting the printing head. Thus, particularly when a long paper is used as the printing medium, there may be adopted an approach in which many holes are formed in a platen that supports the paper in the print region and a suction fan disposed under the platen generates suction force through the holes to thereby bring the paper into close contact with a surface of the platen. The holes formed in the platen are, in general, arranged on an entire surface of the platen in a substantially uniform pattern. 
     In such a printer, in association with a conveyance of the paper on the platen, the paper closes the holes sequentially from upstream in the paper conveyance direction with holes disposed in an area to which the paper has not yet reached open. That is, holes disposed downstream of a downstream edge of the paper in the paper conveyance direction (hereinafter, simply referred to as “leading edge”) remain open. When the suction fan drives in this condition, a large amount of air flows into the holes that remain open. Therefore, there is a problem that, when such a printer performs printing onto the vicinity of the leading edge of the paper, airflow generated by the suction force of the suction fan leads away ink that is ejected by the printing head toward the vicinity of the leading edge of the paper, to result in decreased ink-landing accuracy and thus deterioration in printing quality. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an ink-jet printer capable of ensuring flatness of a printing medium and at the same time restraining decrease in ink-landing accuracy, even when, in particular, printing is performed onto the vicinity of a leading edge of the printing medium. 
     According to an aspect of the present invention, there is provided an ink-jet printer comprising: a conveyance mechanism that conveys a printing medium; an ink ejecting member capable of ejecting ink to the printing medium; a supporting member having plural holes formed therein and supporting the printing medium in a region confronting the ink ejecting member; a suction member capable of sucking air through the holes from a printing medium supporting side of the supporting member to an opposite side thereof; and an airflow restriction member that, in a conveyance of the printing medium on the supporting member by the conveyance mechanism, reduces at least one of an amount and a speed of air flowing into, among holes located downstream of a downstream edge of the printing medium in its conveyance direction, at least a hole closest to the edge of the printing medium. 
     According to the aforementioned aspect, the supporting member has holes formed therein, and the suction member generates suction force through the holes so as to bring a printing medium into close contact with a surface of the supporting member to thereby ensure flatness of the printing medium. Further, the airflow restriction member reduces at least one of an amount and a speed of air flowing into, among holes located downstream of a downstream edge, i.e., leading edge, of a printing medium in its conveyance direction, at least a hole closest to the edge of the printing medium. This can prevent airflow generated by suction force of the suction member from leading away ink that is ejected by the ink ejecting member toward the vicinity of a leading edge of a printing medium. That is, according to the aforementioned aspect, flatness of a printing medium can be ensured and at the same time decrease in ink-landing accuracy can be restrained, even when printing is performed onto the vicinity of a leading edge of a printing medium. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other and further objects, features and advantages of the invention will appear more fully from the following description taken in connection with the accompanying drawings in which: 
         FIG. 1  schematically illustrates a construction of an ink-jet printer according to an embodiment of the present invention; 
         FIG. 2  is a view showing a schematic construction around a platen included in the ink-jet printer of  FIG. 1 ; 
         FIG. 3  is a view showing a schematic construction of an airflow restriction plate included in the ink-jet printer of  FIG. 1 ; 
         FIG. 4  is a partial view showing a state where an upstream end, in a paper conveyance direction, of the airflow restriction plate is in contact with a stopper; and 
         FIGS. 5 to 13  are partial views showing changes in positional relationship between holes in the platen and openings in the airflow restriction plate in association with a movement of a leading edge of a paper. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An ink-jet printer  1  illustrated in  FIG. 1  has a substantially rectangular parallelepiped casing  30 . The casing  30  includes therein a conveyance roller unit  5 , an ink-jet printing unit  6 , a press roller unit  7 , a cutting unit  8 , and a discharge roller unit  9  in this order from upstream in a paper conveyance direction. In the casing  30 , additionally, two roll portions  2   a  and  3   a  each formed by rolling a long paper  2  or  3  as a printing medium are arranged adjacently to each other in a horizontal direction, i.e. a direction perpendicular to the drawing sheet of  FIG. 1 , with a predetermined distance therebetween. The roll portions  2   a  and  3   a  are supported on drums  2   b  and  3   b , respectively, so as to rotate around their axes. The conveyance roller unit  5 , the press roller unit  7 , and the discharge roller unit  9  constitute a conveyance mechanism that conveys the papers  2  and  3 . A controller (not illustrated) disposed within the casing  30  controls an operation of each part of the ink-jet printer  1 . 
     The conveyance roller unit  5  unwinds the papers  2  and  3  from the roll portions  2   a  and  3   a  to convey them downstream in the conveyance direction, then passes the papers through the ink-jet printing unit  6 , and then supplies the papers to the press roller unit  7 . Further, as illustrated in  FIG. 2 , the conveyance roller unit  5  includes two pairs of conveyance rollers  5   a  and  5   b  that rotate by driving of motors  21   a  and  21   b  and are disposed coaxially and adjacently to each other so as to correspond to the respective papers  2  and  3  to be conveyed in parallel. The controller controls the motors  21   a  and  21   b . The two papers  2  and  3  are independently conveyed by the corresponding pairs of conveyance rollers  5   a  and  5   b,  respectively. As illustrated in  FIG. 1 , each of the pairs of conveyance rollers  5   a  and  5   b  includes a drive roller disposed under a paper conveyance path and a press roller disposed over the paper conveyance path to press against the drive roller. These rollers are all disposed with their axes being perpendicular to the paper conveyance direction. Each of the two papers  2  and  3  is, as pinched with the drive roller and the press roller of each pair of conveyance rollers  5   a  or  5   b,  conveyed in accordance with rotation of the drive roller. 
     As illustrated in  FIGS. 1 and 2 , the ink-jet printing unit  6  includes two printing heads  11  each as an ink ejecting member, a carriage  12 , a platen  13  as a supporting member, a suction fan  14  as a suction member, and an airflow restriction plate  40  as an airflow restriction member. 
     The two printing heads  11  are spaced apart from each other by a predetermined distance along the conveyance direction of the papers  2  and  3 , i.e., an upward direction in  FIG. 2 . Each of the printing heads  11  has, on its lower face or on its face confronting the papers  2  and  3 , a large number of ejection nozzles  11   a  for ejecting color inks such as yellow, magenta (purplish red), cyan (bluish green), and black. The printing heads  11  can, based on a signal from the controller, eject the color inks through the large number of ejection nozzles  11   a  onto surfaces or upper faces in  FIG. 1  of the papers  2  and  3  being conveyed, to thereby print a desired color image on the papers. 
     The ejection nozzles  11   a  in the printing heads  11  may arbitrarily be changed in number and arrangement. The printing heads  11  may have ejection nozzles that eject plural color inks, color combination of which is other than the aforementioned, or may have a large number of ejection nozzles for only black ink to print monochrome images. The ink-jet printing unit  6  may be a piezo-jet type, a thermal-jet type, or any other types, as long as ejecting liquid ink through nozzles dot by dot to perform printing on the papers  2  and  3 . 
     The carriage  12  holds the two printing heads  11  on its lower face such that the printing heads  11  may confront the papers. The carriage  12  is, together with the printing heads  11 , reciprocatable perpendicularly to the paper conveyance direction, i.e., horizontal direction in  FIG. 2 . The printing heads  11  held by the carriage  12  eject ink onto the surfaces of the papers  2  and  3  while reciprocating with the carriage  12  perpendicularly to the paper conveyance direction. 
     The platen  13  supports the papers  2  and  3  in a region confronting the printing heads  11 . A surface, an upper face in  FIG. 1 , of the platen  13  serves as a paper supporting side as a printing medium supporting side that is disposed on substantially the same plane as a conveyance surface for the papers  2  and  3 . Thus, the printing heads  11  perform printing on the papers  2  and  3  disposed on the platen  13  while, in a state of confronting the surface of the platen  13 , reciprocating along a widthwise direction of the platen  13 . As illustrated in  FIG. 1 , the platen  13  slopes upward from upstream to downstream in the paper conveyance direction. 
     The printing heads  11  respectively pass over two print regions  60  (illustrated with alternate long and short dash lines in  FIG. 2 ) on the platen  13 . Each of the two print regions  60  is a band region with its length in the paper conveyance direction being equal to that of the printing head  11  and its length in the direction perpendicular to the paper conveyance direction being substantially equal to an entire width of the platen  13 . The two print regions  60  are, similarly to the two printing heads  11 , spaced apart from each other by a predetermined distance along the paper conveyance direction. 
     As illustrated in  FIG. 2 , the platen  13  has many holes  31 , three pairs of ink receiving portions  32  arranged symmetrically with respect to a widthwise center of the platen  13 , two flushing receiving portions  33  arranged at the widthwise center of the platen  13  adjacently to each other along the paper conveyance direction, and a pair of sensor openings  34  arranged on the upstream side in the paper conveyance direction symmetrically with respect to the widthwise center of the platen  13 , which are formed in the platen  13 . 
     The holes  31  are substantially circular holes all having the same size. The holes  31  are uniformly arranged in a staggered pattern in most areas of the platen  13  including the two print regions  60 , an area between the two print regions  60  and areas either upstream or downstream of the print regions  60  in the paper conveyance direction. 
     Between the flushing receiving portions  33  and the pair of ink receiving portions  32  nearest the center of the platen  13 , a plurality of first hole lines and a plurality of second hole lines are alternately arranged in the direction perpendicular to the paper conveyance direction. Each of the first hole lines is made up of eight holes  31  that form a line along the paper conveyance direction with their centers arranged at regular intervals. Each of the plurality of second hole lines is made up of seven holes  31  that form a line along the paper conveyance direction with their centers arranged at regular intervals. The holes  31  in the second hole lines are arranged intermediate between the respective holes  31  in the first hole lines that all the holes  31  have their center substantially equally spaced apart from each other. Between the ink receiving portions  32  in the platen  13 , formed are the holes  31  that are the same as the eight holes  31  constituting the first hole line. 
     Each of the ink receiving portions  32  is an elongated recess extending across the two print regions  60  in the paper conveyance direction. The ink receiving portions  32  receive ink ejected outside widthwise edges of the papers  2  and  3  in margin-free printing. Accordingly, the each ink receiving portion  32  is formed so as to correspond to an edge, of two edges of the each paper  2  and  3  to be conveyed on the platen  13 , nearer either widthwise end of the platen  13 . In this embodiment, the ink receiving portions  32  are provided in three pairs so that they may cope with the papers  2  and  3  having three different width sizes.  FIG. 2  illustrates that the papers  2  and  3 , with their width size corresponding to the pair of ink receiving portions  32  nearest the widthwise ends of the platen  13  among the three pairs, are parallelly conveyed in two lines. An ink absorbing member (not illustrated) capable of absorbing ink is preferably arranged within each of the ink receiving portions  32 . In addition, a discharge mechanism (not illustrated) for automatically discharging ink collected within the ink receiving portions  32  may be connected to the ink receiving portions  32 . 
     The flushing receiving portions  33  are substantially rectangular openings. The flushing receiving portions  33  receive ink ejected upon a flushing operation, i.e., an operation of forcibly ejecting ink through the respective ejection nozzles  11   a  during a non-printing period, for preventing the ejection nozzles  11   a  of the printing heads  11  from being clogged. Thus, the flushing receiving portions  33  are so formed as to include the print regions  60 , respectively. An ink absorbing means (not illustrated) capable of absorbing ink is preferably arranged within each of the flushing receiving portions  33 . The flushing receiving portions  33  also serve as ink receiving portions for, in performing margin-free printing on the papers  2  and  3 , receiving ink ejected outside the edges of the papers  2  and  3  nearer the widthwise center of the platen  13  among the both widthwise edges of the respective two papers  2  and  3 . 
     The sensor openings  34  are so formed as to correspond to respective conveyance areas of the papers  2  and  3 . A reflective photosensor (not illustrated) is disposed above the platen  13  at a position confronting the each sensor opening  34 . The reflective photosensor includes a light-emitting element such as LED and a light-receiving element such as photodiode capable of receiving light emitted from the light-emitting element. The light-emitting element and the light-receiving element make a pair. The photosensor can detect the paper  2  or  3 . The sensor opening  34  is formed in order that the photosensor may properly detect the paper  2  or  3 . 
     The suction fan  14  is, as illustrated in  FIG. 1 , disposed at a position confronting the printing heads  11  with the conveyance paths of the papers  2  and  3  and the platen  13  sandwiched therebetween, i.e., a position on the back face side, i.e., lower face side in  FIG. 1 , of the papers  2  and  3 . The suction fan  14  can suck air, through the holes  31 , from the top face side to the back face side of the platen  13 . The papers  2  and  3  having reached the ink-jet printing unit  6  are brought into close contact with the surface of the platen  13  by means of suction force of the suction fan  14 , and are conveyed with a distance from the printing heads  11  fixed. This can prevent deterioration in printing quality caused by change in distance between the papers and the printing heads  11  when the papers  2  and  3  are curled to thereby partially get apart from the platen  13  to a large extent. 
     As illustrated in  FIG. 1 , the airflow restriction plate  40  (a large part thereof is illustrated with a broken line in  FIG. 2 ) is disposed under the platen  13 . The airflow restriction plate  40  is movable along the paper conveyance direction on substantially the same plane as the platen  13 . As illustrated in  FIG. 1 , stoppers  57  and  58  are disposed downstream and upstream, in the paper conveyance direction, in a movable region of the airflow restriction plate  40 . The airflow restriction plate  40  is movable between the stoppers  57  and  58 . More specifically, the stopper  57  is in contact with a downstream end, in the paper conveyance direction, of the airflow restriction plate  40  when the airflow restriction plate  40  is in its most downstream position, and the stopper  58  is in contact with an upstream end of the airflow restriction plate  40 , in the paper conveyance direction, when the airflow restriction plate  40  is in its most upstream position. 
     As seen from.  FIG. 2 , the airflow restriction plate  40  is a substantially rectangular plate-like member having almost the same width as that of the platen  13 . A length of the airflow restriction plate  40  in the paper conveyance direction is shorter than that of the platen  13  such as to cover downstream five holes  31  in the paper conveyance direction in each of the first and second hole lines that are formed in the platen  13  along the paper conveyance direction. 
     As seen from  FIG. 3 , moreover, many openings  41  and openings  43  are formed in the airflow restriction plate  40 . The openings  41  correspond to a part of the holes  31  formed in the platen  13 , more specifically, to the downstream five holes  31  in the paper conveyance direction in each of the first and second hole lines. The openings  43  correspond to the flushing receiving portions  33  formed in the platen  13 . The openings  41  are, similarly to the holes  31  formed in the platen  13 , uniformly arranged in a staggered pattern in the airflow restriction plate  40 . 
     In the airflow restriction plate  40 , on both sides of the openings  43  that correspond to the flushing receiving portions  33 , a plurality of first opening lines and a plurality of second opening lines are alternately arranged in the direction perpendicular to the paper conveyance direction. Each of the first opening lines is made up of five openings  41  that form a line along the paper conveyance direction to correspond to a part of the each first hole line in the platen  13 . Each of the second opening lines is made up of five openings  41  that form a line along the paper conveyance direction to correspond to a part of the each second hole line in the platen  13 . The openings  41  in the second opening lines are arranged substantially intermediate between the respective openings  41  in the first opening lines. Among the five openings  41  constituting each of the first and second opening lines, the most downstream one in the paper conveyance direction is substantially circular, and the other four are substantially oval shapes elongated in the paper conveyance direction. 
     The openings  41  similar to the five openings  41  constituting the first opening line are formed near both widthwise ends of the airflow restriction plate  40 . 
     Shapes of the openings included in the first and second opening lines will here be described in more detail with reference to  FIG. 4 . In  FIG. 4 , the five openings  41  constituting the first opening line are illustrated with broken lines and designated as openings  121  to  125  sequentially from upstream to downstream in the paper conveyance direction, i.e., an upward direction in  FIG. 4 . The five openings  41  constituting the second opening line are illustrated with broken lines and designated as openings  131  to  135  sequentially from upstream to downstream in the paper conveyance direction. In  FIG. 4 , moreover, the eight holes  31  constituting the first hole line formed in the platen  13  are illustrated with solid lines and designated as holes  101  to  108  sequentially from upstream to downstream in the paper conveyance direction. The seven holes  31  constituting the second hole line formed in the platen  13  are illustrated with solid lines and designated as holes  111  to  117  sequentially from upstream to downstream in the paper conveyance direction. 
     Referring to  FIG. 4 , the most downstream openings  125  and  135  in the paper conveyance direction are substantially circular holes having almost the same size as that of the holes  101  to  108  and  111  to  117 . As mentioned above, all the other openings  121  to  124  and  131  to  134  are substantially oval shapes elongated in the paper conveyance direction, so that areas of the openings  121  to  124  and  131  to  134  may include areas of the holes  101  to  108  and  111  to  117 , respectively. Among the openings  121  to  124  constituting the first opening line, the opening  121  on the most upstream in the paper conveyance direction is longest in the paper conveyance direction. A length of the opening in the paper conveyance direction decreases in the order of openings  122 ,  123 , and  124 . Among the openings  131  to  134  constituting the second opening line, likewise, the opening  131  on the most upstream in the paper conveyance direction is longest in the paper conveyance direction. A length of the opening in the paper conveyance direction decreases in the order of openings  132 ,  133 , and  134 . The openings  121  to  125  constituting the first opening line and the openings  131  to  135  constituting the second opening line are slightly different from each other in their length in the paper conveyance direction. Each of the openings  131  to  135  constituting the second opening line has a larger length than that of the corresponding one of the openings  121  to  125  constituting the first opening line. 
     Shapes, sizes, and positions of the openings  121  to  125  and  131  to  135  are appropriately set such that, in association with a movement of the airflow restriction plate  40  from upstream to downstream in the paper conveyance direction, holes  104  to  108  and holes  113  to  117  may sequentially change from a closed state into an open state, as will be detailed later. 
     As illustrated in  FIG. 1 , the press roller unit  7  has a pair of press rollers comprising a roller  50  that is rotated by means of driving of a motor  22  (see  FIG. 2 ). The press roller unit  7  pinches and conveys the paper  2  that is conveyed from the ink-jet printing unit  6  to the cutting unit  8 . The press roller unit  7  is disposed between the ink-jet printing unit  6  and the cutting unit  8 , so that printing by the ink-jet printing unit  6  and cutting of the paper  2  by the cutting unit  8  can properly be performed. The motor  22  (see  FIG. 2 ) is a stepping motor and has its drive pulses controlled by the controller. 
     As shown in  FIGS. 1 and 2 , a shaft  51  is fitted into the roller  50  of the pair of press rollers in the press roller unit  7 , which is disposed under the conveyance surface for the papers  2  and  3 . The motor  22  rotates the shaft  51 . The shaft  51  is also fitted into a gear  52  on one side of the roller  50 . The gear  52  is a circular flat-plate-like member with teeth on its entire outer circumferential surface. 
     A friction member  53  is disposed between the shaft  51  and the gear  52 . As will be detailed later, until a torque acting between the shaft  51  and the gear  52  reaches a predetermined holding torque threshold, the friction member  53  transmits rotations of one member to the other. When the torque reaches the predetermined holding torque threshold, the friction member  53  no longer transmits rotations. 
     As illustrated in  FIGS. 1 to 3 , a pair of gear portions  40   a  with back faces thereof formed with plural teeth protruding downward are provided at both widthwise ends of the airflow restriction plate  40  on the downstream side in the paper conveyance direction. Under each gear portion  40   a,  disposed is a gear  55  that is a circular flat-plate-like member with its outer circumferential surface throughout formed with teeth, as illustrated in  FIGS. 1 and 2 . Each gear portion  40   a  and each gear  55  are engaged with each other. 
     Between the gear  52  and the gear  55  disposed under one widthwise end of the airflow restriction plate  40 , disposed is a gear  54  that is, similarly to the gears  52  and  55 , a circular flat-plate-like member with teeth on its entire outer circumferential surface. The gear  54  is engaged with the gear  52  and with one of the pair of gears  55 . The gear  54  is rotatable together with a shaft  54   a  (see  FIG. 1 ) fitted therein around an axis of the shaft  54   a . The pair of gears  55  is both rotatable together with a shaft  55   a  (see  FIGS. 1 and 2 ) fitted therein around an axis of the shaft  55   a.    
     When the motor  22  drives to rotate the shaft  51  in a regular direction, i.e., in such a direction as to convey the papers  2  and  3  along the paper conveyance direction, rotations of the shaft  51  is transmitted to the gear  52 , the gear  54 , the gears  55 , and the gear portions  40   a  of the airflow restriction plate  40  in this order until a torque acting between the shaft  51  and the gear  52  reaches the predetermined holding torque threshold of the friction member  53 . In association with rotations, i.e., clockwise rotations in  FIG. 1 , of the gears  55 , the airflow restriction plate  40  with its gear portions  40   a  engaged with the gears  55  moves downstream in the paper conveyance direction. When the downstream end of the airflow restriction plate  40  in the paper conveyance direction is brought into contact with the stopper  57 , a torque acting between the shaft  51  and the gear  52  reaches the predetermined holding torque threshold of the friction member  53 . Then, the shaft  51  becomes slipping on the gear  52 , and therefore rotations of the shaft  51  are no longer transmitted to the gear  52 . Consequently, the gear  52 , the gear  54 , and the gears  55  stop their rotations, so that the downstream end of the airflow restriction plate  40  in the paper conveyance direction is kept in contact with the stopper  57 . 
     When the motor  22  drives to rotate the shaft  51  in a reverse direction, i.e., in such a direction as to convey the papers  2  and  3  against the paper conveyance direction, rotations of the shaft  51  is, similarly to the case where the shaft  51  is rotated in a regular direction, transmitted to the gear  52 , the gear  54 , the gears  55 , and the gear portions  40   a  of the airflow restriction plate  40  in this order until a torque acting between the shaft  51  and the gear  52  reaches the predetermined holding torque threshold of the friction member  53 . In association with rotations of the gears  55 , i.e., counterclockwise rotations in  FIG. 1 , the airflow restriction plate  40  with its gear portions  40   a  engaged with the gears  55  moves upstream in the paper conveyance direction. When the upstream end of the airflow restriction plate  40  in the paper conveyance direction is brought into contact with the stopper  58 , a torque acting between the shaft  51  and the gear  52  reaches the predetermined holding torque threshold of the friction member  53 . Then, the shaft  51  becomes slipping on the gear  52 , and therefore rotations of the shaft  51  are no longer transmitted to the gear  52 . Consequently, the gear  52 , the gear  54 , and the gears  55  stop their rotations, so that the upstream end of the airflow restriction plate  40  in the paper conveyance direction is kept in contact with the stopper  58 . 
     The cutting unit  8  has a movable cutting blade  8   a  disposed on the same side of the papers  2  and  3  as the printing heads  11 , and a fixed cutting blade  8   b  disposed on the opposite side of the papers  2  and  3  to the movable cutting blade  8   a . Each of the movable cutting blade  8   a  and the fixed cutting blade  8   b  is a rectangular-shaped blade having a width extending over the two papers  2  and  3  in order to cut, at one time, the two papers  2  and  3  arranged in parallel. The controller controls the movable cutting blade  8   a  to move it in such a direction as to approach to or separate from the fixed cutting blade  8   b . The movable cutting blade  8   a  cooperates with the fixed cutting blade  8   b  to cut the printed papers  2  and  3 , which have been conveyed to the cutting unit  8 , along a widthwise direction of the papers  2  and  3 . The printed papers  2  and  3  are thus cut into predetermined lengths. 
     The discharge roller unit  9  includes a pair of drive rollers driven by the controller, and conveys the papers  2  and  3  having cut by the cutting unit  8  to discharge them through a discharge port  30   a.    
     The controller subjects an image signal supplied from a non-illustrated input interface to a predetermined process, and then supplies, to the ink-jet printing unit  6 , a print signal including image data corresponding to an image to be printed. The controller also controls timings for conveying the papers  2  and  3  at the conveyance roller unit  5  and at the discharge roller unit  9 , a timing for moving the carriage  12 , a timing for ejecting ink from the printing heads  11 , a timing for moving the airflow restriction plate  40 , and a timing for cutting the papers  2  and  3  at the cutting unit  8 , etc. 
     Next, a description will be given to operations of the respective parts of the ink-jet printer  1  when printing is performed on the papers  2  and  3 . 
     When the ink-jet printer  1  performs printing on the papers  2  and  3 , firstly the motors  21   a  and  21   b  illustrated in  FIG. 2  rotate the pairs of drive rollers  5   a  and  5   b,  and the papers  2  and  3  are unwound from the roll portions  2   a  and  3   a  (see  FIG. 1 ), respectively, and conveyed onto the platen  13 . When leading edges of the papers  2  and  3  arrive at the print region  60  (see  FIG. 2 ) in the platen  13 , the printing heads  11  start reciprocating perpendicularly to the paper conveyance direction. The papers  2  and  3  are kept stopping during a reciprocation of the printing heads  11 , and conveyed in the paper conveyance direction by a predetermined feeding amount when the printing heads are temporarily stopping before every forward or backward movement thereof That is, a forward or backward movement of the printing heads  11  and a conveyance of the paper  2  by the predetermined feeding amount are alternately repeated. The printing heads  11  eject ink onto the papers  2  and  3  during their reciprocations to thereby perform printing. 
     Here will be explained, with reference to  FIGS. 5 to 13 , changes in positional relationship between the holes  31  in the platen  13  and the openings  41  in the airflow restriction plate  40  in association with a movement of the leading edge of the paper  2 . The same process as in the conveyance of the paper  2  is performed in conveying the other paper  3  as well, and therefore an explanation of the case is omitted. 
     Positions A to G of the leading edge of the paper are shown in  FIG. 2 .  FIG. 5  illustrates a case where the leading edge of the paper  2  is in the position A.  FIG. 6  illustrates a case where the leading edge of the paper  2  is between the positions A and B.  FIG. 7  illustrates a case where the leading edge of the paper  2  is in the position B.  FIG. 8  illustrates a case where the leading edge of the paper  2  is between the positions B and C.  FIGS. 9 to 13  illustrate cases where the leading edge of the paper  2  is in the positions C to G, respectively. In  FIGS. 5 to 13 , only one paper  2  of the papers  2  and  3  is shown. Also shown are the holes  31  in the platen  13  and the openings  41  in the airflow restriction plate  40  both formed within the conveyance area of the paper  2 . The holes  31  and the openings  41  are the same as those in  FIG. 4 . More specifically, regarding the holes in the platen  13 , only a set of first and second hole lines made up of eight holes  101  to  108  and seven holes  111  to  117 , respectively, are shown. Regarding the openings in the airflow restriction plate  40 , only a set of first and second opening lines made up of five openings  121  to  125  and five openings  131  to  135 , respectively, are shown. The set of first and second opening lines corresponds to the set of first and second hole lines. 
     The end of the airflow restriction plate  40  on the upstream side in the paper conveyance direction is in contact with the stopper  58  (see  FIG. 1 ) until the leading edge of the paper  2  reaches the position A on the platen  13 . In this state, as described above with reference to  FIG. 4 , the holes  104  to  108  and  113  to  117  are closed, and the holes  101  to  103 ,  111 , and  112  as patterned with oblique lines are open. A position of the airflow restriction plate  40  in this state is referred to as a first position. 
     When the leading edge of the paper  2  reaches the position A, the airflow restriction plate  40  moves downstream in the paper conveyance direction by a predetermined distance from the first position and then comes into a second position as shown in  FIG. 5 . A movement of the airflow restriction plate  40  is carried out by driving the motor  22  (see  FIG. 2 ) of the press roller unit  7  by an amount corresponding to a predetermined number of pulses. This is because, as described above, the motor  22  drives to rotate the gear  52  as well as the shaft  51  and this rotation is transmitted to the gear  54 , the gears  55 , and the gear portions  40   a  of the airflow restriction plate  40  in this order. 
     The motor  22 , which serves to rotate the roller  50  of the press roller unit  7  after the leading edge of the paper  2  arrives at the press roller unit  7 , is also used to move the airflow restriction plate  40  before the leading edge of the paper  2  arrives at the press roller unit  7 , that is, before the leading edge of the paper  2  becomes pinched with the pair of press rollers including the roller  50 . 
     The airflow restriction plate  40  moves from the first position to the second position, so that the hole  113  and the opening  131  become partially overlapping each other to open the hole  113  in part. The holes  104  to  108  and  114  to  117  that are located downstream, in the paper conveyance direction, of the leading edge of the paper  2  are kept closed with the airflow restriction plate  40 . The holes  101  to  103 ,  111 , and  112  are kept open. At this time, the vicinity of the leading edge of the paper  2  is brought into close contact with the surface of the platen  13  by means of the suction force of the suction fan  14  through a part of the hole  113  in addition to the holes  101  to  103 ,  111 , and  112 . 
     Then, the paper  2  is conveyed with the airflow restriction plate  40  stopped in the second position.  FIG. 6  illustrates a state where the leading edge of the paper  2  is between the positions A and B. 
     When the paper  2  is further conveyed and the leading edge thereof reaches the position B, the motor  22  of the press roller unit  7  drives again by an amount corresponding to a predetermined number of pulses. The airflow restriction plate  40  thereby moves downstream in the paper conveyance direction by a predetermined distance from the second position and then comes into a third position as shown in  FIG. 7 . 
     The airflow restriction plate  40  moves from the second position to the third position, so that the holes  104  and  114  partially overlap the openings  121  and  132 , respectively, and at the same time an overlap area of the hole  113  with the opening  131  is increased. Thus, the holes  104  and  114  are partially opened to the same extent as the hole  113  illustrated in  FIGS. 5 and 6 . The hole  113  is, though still partially, opened larger than in  FIGS. 5 and 6 . The holes  105  to  108  and  115  to  117  that are located downstream, in the paper conveyance direction, of the leading edge of the paper  2  are kept closed with the airflow restriction plate  40 . The holes  101  to  103 ,  111 , and  112  are kept open. At this time, the vicinity of the leading edge of the paper  2  is brought into close contact with the surface of the platen  13  by means of the suction force of the suction fan  14  through a part of the holes  104  and  114  in addition to the holes  101  to  103 ,  111 ,  112 , and a part of the hole  113 . 
     Then the paper  2  is conveyed with the airflow restriction plate  40  stopped in the third position.  FIG. 8  illustrates a state where the leading edge of the paper  2  is between the positions B and C. 
     When the paper  2  is further conveyed and the leading edge thereof reaches the position C, the motor  22  of the press roller unit  7  drives again by an amount corresponding to a predetermined number of pulses. The airflow restriction plate  40  thereby moves downstream in the paper conveyance direction by a predetermined distance from the third position and then comes into a fourth position as shown in  FIG. 9 . 
     The airflow restriction plate  40  moves from the third position to the fourth position, so that the holes  105  and  115  partially overlap the openings  122  and  133 , respectively, and at the same time overlap areas of the holes  104 ,  113 , and  114  with the openings  121 ,  131 , and  132 , respectively, are increased. Thus, the holes  105  and  115  are partially opened to the same extent as the holes  104  and  114  in  FIGS. 7 and 8 . The holes  104 ,  113 , and  114  are, though still partially, opened larger than in  FIGS. 7 and 8 . The holes  106  to  108 ,  116  and  117  that are located downstream, in the paper conveyance direction, of the leading edge of the paper  2  are kept closed with the airflow restriction plate  40 . The holes  101  to  103 ,  111 , and  112  are kept open. At this time, the vicinity of the leading edge of the paper  2  is brought into close contact with the surface of the platen  13  by means of the suction force of the suction fan  14  through the holes  105  and  115  in addition to the holes  101  to  103 ,  111 ,  112 , and a part of the holes  104 ,  113 , and  114 . 
     Thereafter, in the same manner as described above, every time the leading edge of the paper  2  reaches the positions D, E, F, and G, the motor  22  of the press roller unit  7  drives by an amount corresponding to a predetermined number of pulses. The airflow restriction plate  40  thereby moves downstream in the paper conveyance direction by a predetermined distance and moves from the fourth position as shown in  FIG. 9  into fifth, sixth, seventh, and eighth positions as shown in  FIGS. 10 ,  11 ,  12 , and  13 , respectively. 
     The airflow restriction plate  40  moves from the fourth position as shown in  FIG. 9  into the fifth position as shown in  FIG. 10 , so that the holes  106  and  116  partially overlap the openings  123  and  134 , respectively, and at the same time overlap areas of the holes  104 ,  105 ,  113 ,  114  and  115  with the openings  121 ,  122 ,  131 ,  132 , and  133 , respectively, are increased. Subsequently, the airflow restriction plate  40  moves from the fifth position as shown in  FIG. 10  into the sixth position as shown in  FIG. 11 , so that the holes  107  and  117  partially overlap the openings  124  and  135 , respectively, and at the same time overlap areas of the holes  104 ,  105 ,  106 ,  113 ,  114 ,  115 , and  116  with the openings  121 ,  122 ,  123 ,  131 ,  132 ,  133 , and  134 , respectively, are increased. Further subsequently, the airflow restriction plate  40  moves from the sixth position as shown in  FIG. 11  into the seventh position as shown in  FIG. 12 , so that the hole  108  partially overlaps the opening  125 , and at the same time overlap areas of the holes  104 ,  105 ,  106 ,  107 ,  113 ,  114 ,  115 ,  116 , and  117  with the openings  121 ,  122 ,  123 ,  124 ,  131 ,  132 ,  133 ,  134 , and  135 , respectively, are increased. Finally, the airflow restriction plate  40  moves from the seventh position as shown in  FIG. 12  into the eighth position as shown in  FIG. 13 , so that the hole  108  and the opening  125 , both of which are substantially circular, almost entirely overlap each other, and the hole  117  and the opening  135 , both of which are substantially circular, almost entirely overlap each other. At the same time, the airflow restriction plate  40  is arranged such that the holes  104  to  107  may be within areas of the substantially oval openings  121  to  124 , respectively, with an upstream end thereof, in the paper conveyance direction, aligned with each other. That is, all the holes formed in the platen  13  are opened. Thus, when the airflow restriction plate  40  is in the eighth position, the vicinity of the leading edge of the paper  2  is brought into close contact with the surface of the platen  13  by means of the suction force of the suction fan  14  through the holes  101  to  108  and  111  to  117 . 
     As thus described, in the course of the movement of the airflow restriction plate  40  from the first to eighth positions, the holes  101  to  103 ,  111 , and  112  are always kept open, while the holes  104  to  108  and  113  to  117  become opened sequentially from upstream in the paper conveyance direction. Then, when the leading edge of the paper  2  reaches the position G and the airflow restriction plate  40  is arranged at the eighth position, all of the holes  104  to  108  and  113  to  117  become opened (see  FIG. 13 ). 
     That is, during the conveyance of the paper  2  on the platen  13 , the holes located downstream, in the paper conveyance direction, of the leading edge of the paper  2  are always kept closed with the airflow restriction plate  40 . 
     When the airflow restriction plate  40  is arranged in the eighth position, the end of the airflow restriction plate  40  on the downstream side in the paper conveyance direction is brought into contact with the stopper  57  (see  FIG. 1 ). At this time, as described above, a torque acting between the shaft  51  and the gear  52  reaches the predetermined holding torque threshold of the friction member  53 . Therefore, rotations of the shaft  51  are no longer transmitted to the gear  52 . Accordingly, although the motor  22  hereafter drives for conveying the paper  2  further downstream in the paper conveyance direction, no rotation is transmitted to the gear portions  40   a  of the airflow restriction plate  40 , so that the airflow restriction plate  40  is kept stopped and only the shaft  51  and the roller  50  of the press roller unit  7  with the shaft  51  fitted therein are rotated. 
     When printing is completed to a rear end of the long paper  2 , the motor  22  drives in a direction reverse to the previous driving direction before a leading edge of a new paper is supplied onto the platen  13 . The airflow restriction plate  40  thereby moves upstream in the paper conveyance direction, i.e., from the eighth position as shown in  FIG. 13  to the first position as shown in  FIG. 4 . 
     As described above, according to the ink-jet printer  1 , the holes  31  are formed in the platen  13 , and the suction fan  14  generates suction force through the holes  31  so as to bring the papers  2  and  3  into close contact with a surface of the platen  13  to thereby ensure flatness of the papers  2  and  3 . Moreover, the airflow restriction plate  40  closes the holes  31  that are located downstream of leading edges of the papers  2  and  3 , to shut off inflow of air into those holes  31 . This can surely prevent airflow generated by the suction force of the suction fan  14  from leading away ink that is ejected by the printing heads  11  toward the vicinity of leading edges of the papers  2  and  3 . That is, according to this embodiment, even when printing is performed onto the vicinity of leading edges of the papers  2  and  3 , flatness of the papers  2  and  3  can be ensured and, at the same time, decrease in ink-landing accuracy can effectively be restrained. As a result, an image with high picture quality can be printed on the vicinity of leading edges of the papers  2  and  3 . 
     In order to solve the problem of decrease in ink-landing accuracy caused by inflow of air into the holes  31  not closed with the papers  2  and  3 , it is also conceivable that the papers are in advance conveyed to such an extent that the papers may close all the holes  31  in the platen  13  before the printing heads  11  start their ink ejection operations. In this case, however, the leading edge of the paper serves only to close the holes  31  and cannot be printed thereon. This wastes a part of the paper. Particularly when the platen  13  has a large length in the paper conveyance direction, a large blank margin appears in the vicinity of the leading edge of the paper. Accordingly, a waste part of the paper without printing thereon, i.e., loss of paper, significantly increases. According to this embodiment, on the other hand, since printing can be performed onto the vicinity of a leading edge of a paper without forming a long blank margin thereat, a waste of the paper may be reduced. 
     In this embodiment, additionally, the airflow restriction plate  40  is adopted as an airflow restriction member for restricting inflow of air into the holes  31 . The airflow restriction plate  40  confronts a surface of the platen  13  opposite to the paper supporting side thereof and, in this condition, is movable along the paper conveyance direction. In association with the movement of the leading edges of the papers  2  and  3  on the platen  13  toward downstream in the paper conveyance direction, the airflow restriction plate  40  is also moved downstream in the paper conveyance direction and, with this movement, opens the previously-closed holes  31  sequentially from upstream in the paper conveyance direction. That is, the aforementioned effects may be obtained with the airflow restriction plate  40  having such a relatively simple structure. 
     Moreover, the airflow restriction plate  40  has the openings  41  formed therein that correspond to a part of the many holes  31  formed in the platen  13 . The openings  41  have larger lengths in the paper conveyance direction at upperstream positions in the paper conveyance direction. In this case, a movement distance of the airflow restriction plate  40  toward downstream in the paper conveyance direction for sequentially opening the holes  31  formed in the platen  13  becomes relatively small. This may restrain a printer from increasing in size. 
     Further, the airflow restriction plate  40  can be moved by driving force of the motor  22  that is provided basically for the purpose of driving the roller  50  of the press roller unit  7 . More specifically, the driving force of the motor  22  rotates the shaft  51 , and the rotations of the shaft  51  are transmitted to the gear  52 , the gear  54 , the gears  55 , and the gear portions  40   a,  so that the airflow restriction plate  40  moves. Like this, since the motor  22  for driving the press roller unit  7  is used also as a drive source of the airflow restriction plate  40 , there is no need to individually provide a drive source dedicated to the airflow restriction plate  40 . Thus, a manufacturing cost of the printer may be reduced. 
     Still further, provided is the stopper  57  that stops the airflow restriction plate  40  from moving downstream in the paper conveyance direction beyond the position G. The press roller unit  7  conveys the papers  2  and  3  even while the airflow restriction plate  40  is being stopped by the stopper  57 . More specifically, the friction member  53  is disposed between the shaft  51  and the gear  52 , and, when the airflow restriction plate  40  is in contact with neither the stopper  57  nor the stopper  58 , rotations of the shaft  51  are transmitted to the gear  52  to thereby move the airflow restriction plate  40 . On the other hand, when the airflow restriction plate  40  is in contact with either the stopper  57  or the stopper  58 , rotations of the shaft  51  are not transmitted to the gear  52 , so that the airflow restriction plate  40  is kept stopping without moving and only the roller  50  of the press roller unit  7  with the shaft  51  fitted therein is rotated. Consequently, even after the airflow restriction plate  40  becomes in contact with the stopper  57 , the papers  2  and  3  can properly be conveyed by the press roller unit  7 . 
     In the aforementioned embodiment, when the papers  2  and  3  are conveyed on the platen  13 , the airflow restriction plate  40  closes all the holes  31  located downstream, in the paper conveyance direction, of the leading edges of the papers  2  and  3 . However, this is not limitative. For example, the effect of the restrained decrease in ink-landing accuracy can be obtained also by closing, among all the holes  31  located downstream, in the paper conveyance direction, of the leading edges of the papers  2  and  3 , only the holes  31  closest to the leading edges or only the holes  31  located within the widths of the papers  2  and  3 . 
     In addition, instead of closing the holes  31  located downstream, in the paper conveyance direction, of the leading edges of the papers  2  and  3  to thereby completely shut off airflow into those holes, air flowing into those holes may be reduced in at least one of an amount and a speed. In this case, some air flows into the holes  31  located around the leading edges of the papers  2  and  3 , and this airflow into those holes  31  leads away ink that is ejected by the printing heads  11  toward the vicinity of the leading edge of the papers  2  and  3 . However, this is acceptable as long as the airflow is in such a degree as to cause no decrease in ink-landing accuracy. 
     In the aforementioned embodiment, airflow into the holes  31  located downstream, in the paper conveyance direction, of the leading edges of the papers  2  and  3  is constantly restricted during the conveyance of the papers  2  and  3  on the platen  13 . However, this is not limitative, and airflow into those holes  31  may be restricted intermittently. 
     The airflow restriction member is not limited to the airflow restriction plate  40  as in the aforementioned embodiment. Members having various constructions may be adopted as long as the members can restrict air flowing into the holes  31 . For example, a plate member having no openings  41  shown in the aforementioned embodiment may be used as the airflow restriction member. Even though openings are to be formed, it is not always necessary that the openings have larger lengths in the paper conveyance direction at upperstream positions in the paper conveyance direction. A shape of the openings may arbitrarily be changed. Moreover, the airflow restriction member is not limited to a plate member. 
     Further, a shape and an arrangement of the holes  31  formed in the platen  13  are not limited to a substantial circle and a staggered pattern, respectively. The holes  31  formed in the platen  13  may arbitrarily be changed in number, size or opening area per one hole, shape, and arrangement. 
     Still further, although, in the aforementioned embodiment, the airflow restriction plate  40  acting as the airflow restriction member can be moved by the driving force of the motor  22  of the press roller unit  7 , this is not limitative and the airflow restriction plate  40  may be moved by driving force of the motors  21   a  and  21   b  of the conveyance roller unit  5 . In this case, it is necessary to provide a transmission mechanism for transmitting the driving force of the motors  21   a  and  21   b  to the airflow restriction plate  40 . Alternatively, the airflow restriction plate  40  may be moved by a drive source, e.g., motor or solenoid, etc, dedicated thereto. 
     Still further, although the aforementioned embodiment illustrates that printing is performed onto the long papers  2  and  3  that have been unwound from the respective roll portions  2   a  and  3   a  and then conveyed, cut papers with a predetermined length may be conveyed to be printed thereon. 
     Still further, an application of the present invention is not limited to a so-called serial-type printer in which, as in the aforementioned embodiment, printing is performed with the printing heads  11  that reciprocate perpendicularly to the paper conveyance direction. The present invention is applicable also to a line-type printer that performs printing with a fixed printing head. 
     While this invention has been described in conjunction with the specific embodiments outlined above, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the preferred embodiments of the invention as set forth above are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the invention as defined in the following claims.