Patent Publication Number: US-2022234853-A1

Title: Medium feeding mechanism

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2021-008833, filed on Jan. 22, 2021 and the prior Japanese Patent Application No. 2021-160677 filed on Sep. 30, 2021, the entire contents of which are incorporated herein by reference. 
     FIELD 
     The embodiments discussed herein are related to a medium feeding mechanism. 
     BACKGROUND 
     In a proposed conventional paper feeding apparatus for an image formation apparatus, when a detection switch determines that a non-paper-feed jam has occurred, a drive control unit performs control such that a paper feeding roller stops rotating, a sheet is returned into a sheet accommodation part by means of a return roller, and then the paper feeding roller starts to rotate again (see, for example, Japanese Laid-open Patent Publication No. 2004-51347). 
     SUMMARY 
     In an aspect, a medium feeding mechanism includes: a feeder that feeds a medium; a transport path that is coupled to the feeder; a transporter that transports the medium through the transport path; a transport drive that drives the transporter; an entry detection sensor that detects when the medium fed from the feeder has entered the transport path; a take-in transporter that takes in the medium transported by the transporter; and a controller that controls the feeder and the take-in transporter, wherein when the entry detection sensor detects entry of the medium at a time that falls within a first range set in advance, the controller controls the take-in transporter so as to take in the medium, and when the entry detection sensor detects entry of the medium at a time that falls within a second range following the first range, the controller controls the feeder so as to delay feeding of a medium to be transported next, and controls the take-in transporter so as to delay a take-in time for the medium. 
     The object and advantages of the present invention will be realized by the elements set forth in the claims or combinations thereof. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  illustrates the internal configuration of a printing system in one embodiment; 
         FIG. 2  illustrates the control configurations of a medium feeding apparatus and a printing apparatus in one embodiment; 
         FIG. 3  illustrates the internal configuration of a first feeder (second feeder) in one embodiment; 
         FIG. 4  is a flowchart for illustrating a medium feeding operation in one embodiment; 
         FIG. 5  is a timing chart for illustrating a retry mode  2  in one embodiment; 
         FIG. 6  is a timing chart for illustrating a retry mode  1  in one embodiment; 
         FIG. 7  is a timing chart for illustrating a comparative example; 
         FIG. 8  depicts a relationship between a transport velocity and an elapsed time so as to illustrate a correction of the transport velocity in one embodiment (example 1); 
         FIG. 9  depicts a relationship between a transport velocity and an elapsed time so as to illustrate a correction of the transport velocity in one embodiment (example 2); 
         FIG. 10A  depicts the internal configuration of a first feeder (second feeder) so as to illustrate the blocking of blowout of floating air in one embodiment (example 1); 
         FIG. 10B  depicts the internal configuration of a first feeder (second feeder) so as to illustrate the blocking of blowout of floating air in one embodiment (example 2); 
         FIG. 11  illustrates a positional relationship between media during transport in one embodiment; 
         FIG. 12A  is a table for illustrating the rescheduling of permissible times for sensors in one embodiment (example 1); 
         FIG. 12B  is a table for illustrating the rescheduling of permissible times for sensors in one embodiment (example 2); 
         FIG. 12C  is a table for illustrating the rescheduling of permissible times for sensors in one embodiment (example 3); 
         FIG. 12D  is a table for illustrating the rescheduling of permissible times for sensors in one embodiment (example 4); 
         FIG. 13  illustrates a relationship between a transport velocity and an elapsed time achieved when a correction is not made in a case where an entry detection time falls within a second range; 
         FIG. 14  depicts a relationship between a transport velocity and an elapsed time so as to illustrate the stopping of transport in another embodiment; and 
         FIG. 15  is a table for illustrating the rescheduling of permissible times for sensors in another embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     In the meantime, a medium feeder that blows out air to float a plurality of media placed on a placement mount, including an uppermost medium, and transports the floating uppermost medium by means of a transport belt may have a bad attraction state when causing a medium to be attracted to the transport belt; and when, for example, media are transported with a low attraction force, one attracted medium, although advancing to some degree, may not arrive, within a specified time, at an entrance passage detection sensor disposed at a transport path, and it may be determined that free spinning has occurred. It may also be determined like this that free spinning has occurred in other feeding techniques such as a feeding technique in which media are fed using a roller as described above. 
     In a case where it is determined that free spinning has occurred while a medium has been transported up to a position very close to the entrance passage detection sensor, even if the transport belt is stopped soon, the medium may be transported by some distance before the transport completely stops, and thus could arrive at a transport roller provided at the transport path before being stopped. In this case, the medium, which should have been stopped due to the determination that free spinning has occurred, continues to be transported. 
     When a medium is detected by the entrance passage detection sensor at a time that follows a reference passage time, the transport velocity may be increased such that media arrive at a take-in transporter such as a paper-stop-roller pair at more constant times. 
     However, when a medium is detected at a time that is far behind a reference passage time, the transport velocity will need to be increased accordingly, and a motor may be required to provide performance exceeding the upper limit. Even if transporting is performed with the upper limit of the permissible transport velocity of the motor, the transport velocity will be less than a transport velocity that would be required to compensate for the delay, so the time of passing a passage detection sensor positioned downstream in the transport direction from the entrance passage detection sensor will also be delayed, resulting in the determination that a jam has occurred. Moreover, the intervals between times at which media arrive at the take-in transporter cannot be made constant. 
     The following describes a medium feeding mechanism in accordance with one embodiment of the present invention and a medium feeding mechanism in accordance with another embodiment of the present invention by referring to the drawings. 
     One Embodiment 
       FIG. 1  illustrates the internal configuration of a printing system  100 . 
       FIG. 2  illustrates the control configurations of a medium feeding apparatus  1  and a printing apparatus  101 . 
       FIG. 3  illustrates the internal configuration of a first feeder  11  (second feeder  12 ). 
     The front-rear direction, up-down direction, and left-right direction indicated in  FIGS. 1 and 3  and  FIGS. 10A and 10B  (described hereinafter) are merely directions for descriptive purposes. For example, the front-rear direction and the left-right direction may each be a horizontal direction, and the up-down direction may be a vertical direction. 
     The printing system  100  depicted in  FIG. 1  includes the medium feeding apparatus  1  and the printing apparatus  101 . As will be described hereinafter in detail, the medium feeding mechanism in the present embodiment includes the medium feeding apparatus  1 , components on a transport route extending to a paper-stop-roller pair  131  in the printing apparatus  101  (a reception roller pair  132 , the paper-stop-roller pair  131 , a paper stop sensor S 30 , and a joining transport path P 3 ), and a controller  151  for the printing apparatus  101 . 
     The medium feeding mechanism feeds a medium M toward the downstream side in the transport direction with reference to the paper-stop-roller pair  131  in the printing apparatus  101  (the downstream side is an example of a destination to which the medium M is fed). The destination apparatus for media M is not limited to the printing apparatus  101  and may be another apparatus such as a transport apparatus or a post-processing apparatus. The medium feeding apparatus  1  may be integral with a destination apparatus such as the printing apparatus  101 . Media M are, for example, sheets (flat paper) but may be other sheet-like media such as films. 
     As depicted in  FIG. 1 , the medium feeding apparatus  1  includes a first feeder  11 , a second feeder  12 , a first individual transport path P 1 , a second individual transport path P 2 , a joining transport path P 3 , first to ninth transport roller pairs  21 - 29 , first to fourth transport drives D 1 -D 4 , a first entrance passage detection sensor S 11 , first midstream passage detection sensors S 12 -S 14 , a first exit passage detection sensor S 15 , a second entrance passage detection sensor S 21 , second midstream passage detection sensors S 22  and S 23 , and a second exit passage detection sensor S 24 . As depicted in  FIG. 2 , the medium feeding apparatus  1  also includes a controller  31 , a storage unit  32 , and an interface unit  33 . 
     The medium feeding apparatus  1  is divided into an upper stage  1   a  and a lower stage  1   b.  The first feeder  11  is disposed in the upper stage  1   a.  The second feeder  12  is disposed in the lower stage  1   b.  Thus, the first feeder  11  and the second feeder  12  are vertically arranged. The first feeder  11  and the second feeder  12  are examples of a feeder that feeds a medium M. The feeders may each be constituted by a single feeder or three or more feeders. 
     As depicted in  FIG. 3 , the first feeder  11  and the second feeder  12  respectively include placement mounts  11   a  and  12   a,  transport belts  11   b  and  12   b,  suction units  11   c  and  12   c,  floating-air blowout mechanisms  11   d  and  12   d,  floating air shutters  11   e  and  12   e,  separation-air blowout mechanisms  11   f  and  12   f,  medium detection sensors  11   g  and  12   g,  and end fences  11   h  and  12   h.  The first feeder  11  and the second feeder  12  may have similar configurations, and in  FIG. 3 , reference symbols for the second feeder  12  are provided in parenthesis next to reference symbols for the first feeder  11 . Similarly, in  FIG. 3 , reference symbols for the sixth transport roller pair  26  and the second entrance passage detection sensor S 21  are provided in parenthesis next to reference symbols for the first transport roller pair  21  and the first entrance passage detection sensor S 11 . 
     A plurality of media M are placed on each of the placement mounts  11   a  and  12   a.  The placement mount  11   a  of the first feeder  11  and the placement mount  12   a  of the second feeder  12  may each have a different type (e.g., size, material, color) of media M placed thereon. In this case, when changing the type of media M on which printing is to be performed, the feeder for feeding the media M is switched between the first feeder  11  and the second feeder  12 . The placement mounts  11   a  and  12   a  are lifted or lowered by being driven by a placement-mount lifting-and-lowering drive (not illustrated). As an example, when the number of media M placed on the placement mount  11   a ( 12   a ) decreases, a controller (not illustrated) for the first feeder  11  (second feeder  12 ) (or the controller  31  depicted in  FIG. 2 ) may control the placement-mount lifting-and-lowering drive so as to lift the placement mount  11   a ( 12   a ) on the basis of the amount of reflection of light emitted by the medium detection sensor  11   g ( 12   g ) (described hereinafter) in the horizontal direction at a predetermined placement-surface height. 
     For example, the transport belt  11   b ( 12   b ) may be shaped like a looped strip and cover two pulleys. The transport belt  11   b ( 12   b ) includes a plurality of through holes through which suction air A 1  sucked by the suction unit  11   c ( 12   c ) (described hereinafter) passes. The transport belt  11   b ( 12   b ) rotates counterclockwise with reference to  FIG. 3 , so as to draw out, one by one, media M attracted thereto by the suction unit  11   c ( 12   c ) sucking suction air A 1 . The transport belt  11   b ( 12   b ) is an example of a drawing-out unit that draws out media M one by one from the first feeder  11  (second feeder  12 ). Note that another transport member such as a transport roller may be replaced with the transport belt  11   b ( 12   b ) so as to be used as the drawing-out unit. 
     The suction unit  11   c ( 12   c ) sucks suction air A 1  through the plurality of through holes provided through the transport belts  11   b  and  12   b  by being driven by a sucker (e.g., a suction fan) (not illustrated). In this way, the suction unit  11   c ( 12   c ) causes a floating uppermost media M 1 , among a plurality of media M placed on the placement mount  11   a  ( 12   a ), to be attracted to the transport belt  11   b ( 12   b ). 
     The floating-air blowout mechanism  11   d ( 12   d ) floats at least the uppermost medium M 1  of the plurality of media M placed on the placement mount  11   a ( 12   a ) by blowing out floating air A 2  by means of, for example, a blowout fan. The floating-air blowout mechanisms  11   d  and  12   d  may each blow out floating air A 2  obliquely upward so as to float, for example, about  10  media M, including the uppermost medium M 1 . Although  FIG. 3  depicts the floating-air blowout mechanisms  11   d  and  12   d  disposed on the downstream side in the direction in which media M are transported (disposed on the right side), floating-air blowout mechanisms may also be disposed on both sides of the media M in a width direction (front-rear direction) orthogonal to the direction in which the media M are transported. 
     The floating air shutter  11   e ( 12   e ) is an example of a blocking part that blocks blowout of floating air A 2  by the floating-air blowout mechanism  11   d ( 12   d ), and is closed to be positioned at a close position where the floating air shutter blocks the blowout and is opened to be positioned at an open position at which the floating air shutter does not block the blowout. The blocking part may be a controller for stopping the blowout of floating air A 2  by the floating-air blowout mechanism  11   d ( 12   d ), and the blowout of floating air A 2  can be immediately blocked using the floating air shutter  11   e ( 12   e ). The floating air shutter  11   e ( 12   e ) can be situated at one or more positions between the close position and the open position so that the quantity of floating air A 2  can be adjusted. 
     The separation-air blowout mechanism  11   f ( 12   f ) blows out separation air A 3  by means of, for example, a blowout fan so as to separate the uppermost medium M 1  from a second medium M 2  located under the uppermost medium M 1 . As with the floating-air blowout mechanisms  11   d ( 12   d ), the separation-air blowout mechanisms  11   f ( 12   f ) may include a separation air shutter, i.e., an example of a blocking part, such that the entirety of or a portion of separation air A 3  can be blocked. Although  FIG. 3  depicts the separation-air blowout mechanisms  11   f  and  12   f  disposed on the downstream side in the direction in which media M are transported (disposed on the right side), separation-air blowout mechanisms may also be disposed on both sides of the media M in the width direction of the media M (front-rear direction). 
     The medium detection sensor  11   g ( 12   g ) detects a medium M placed on the placement mount  11   a ( 12   a ). For example, the medium detection sensor  11   g ( 12   g ) may detect the presence/absence of a medium M at a detection height on the basis of reflected light resulting from detection light emitted in the horizontal direction. The medium detection sensor  11   g ( 12   g ) detects the presence/absence of a medium M, thereby allowing a controller for the first feeder  11  (second feeder  12 ) (not illustrated) (or the controller  31  depicted in  FIG. 2 ) to detect the height of the uppermost medium M 1  placed on the placement mount  11   a ( 12   a ). The medium detection sensor  11   g ( 12   g ) may emit detection light toward floating media M and, on the basis of the quantity of resultant reflected light, detect the floating state of the media M (e.g., the number of media M falling within a detectable range in the height direction). 
     The end fence  11   h ( 12   h ) restricts the position of the upstream-side edge portion of a floating medium M in the transport direction. Although not illustrated, a pair of side fences for restricting the positions of the edge portions, in the width direction, of media M placed on the placement mount  11   a ( 12   a ) may also be disposed. 
     As described above, the first feeder  11  (second feeder  12 ) includes the floating-air blowout mechanism  11   d ( 12   d ) and blows out floating air A 2  to float a medium M, thereby feeding the medium M. However, the first feeder  11  and the second feeder  12  may also be feeders that feed a medium M without floating the same. 
     Although not illustrated, the first feeder  11  (second feeder  12 ) may include a placement-mount lifting-and-lowering drive such as a motor (an example of an actuator) for moving up or down the placement mount  11   a ( 12   a ), and a drawing-out drive such as a motor (an example of an actuator) for rotating a drive pulley constituting one of the two pulleys covered by the transport belt  11   b ( 12   b ). 
     Referring to  FIG. 1  again, the first individual transport path P 1  is coupled to the first feeder  11 . The second individual transport path P 2  is coupled to the second feeder  12 . The joining transport path P 3  joins the first individual transport path P 1  and the second individual transport path P 2  together and extends to the paper-stop-roller pair  131  in the printing apparatus  101 . The first individual transport path P 1  and the second individual transport path P 2  are different in terms of the route lengths of the transport routes for a medium M. For example, the route length of the second individual transport path is half or less of that of the first individual transport path P 1 . 
     A large proportion of the first individual transport path P 1  is disposed within the upper stage  1   a  of the medium feeding apparatus  1 . The second individual transport path P 2  is disposed within the lower stage  1   b  of the medium feeding apparatus  1 . The first individual transport path P 1  joins the second individual transport path P 2  on a portion of the joining transport path P 3  that is disposed within the lower stage  1   b.    
     The first to ninth transport roller pairs  21 - 29  each include a driving roller and a driven roller that are disposed facing each other, and each transport a medium M in a nipping manner. 
     The first to fifth transport roller pairs  21 - 25  transport a medium M on the first individual transport path P 1  within the upper stage  1   a  of the medium feeding apparatus  1 . The sixth and seventh transport roller pairs  26  and  27  transport a medium M on the second individual transport path P 2  within the lower stage  1   b  of the medium feeding apparatus  1 . The eighth and ninth transport roller pairs  28  and  29  transport a medium M on a portion of the joining transport path P 3  that is located within the lower stage  1   b  of the medium feeding apparatus  1 . The reception roller pair  132  in the printing apparatus  101  (described hereinafter) transport a medium M on the portion of the joining transport path P 3  that is located within the printing apparatus  101 . The first to fifth transport roller pairs  21 - 25  and the sixth and seventh transport roller pairs  26  and  27  are examples of a plurality of individual transporters that transport a medium M on the first individual transport path P 1  or the second individual transport path P 2  (a plurality of individual transport paths). The eighth and ninth transport roller pairs  28  and  29  and the reception roller pair  132  are examples of a joining transporter that transports a medium M on the joining transport path P 3 . The first individual transport path P 1 , the second individual transport path P 2 , and the joining transport path P 3  are examples of a transport path coupled to a feeder (first feeder  11  or second feeder  12 ). The first to ninth transport roller pairs  21 - 29  and the reception roller pair  132  are also examples of a transporter (first conveyor) that transports a medium M on a transport path. 
     The first to fourth transport drives D 1 -D 4  are motors (examples of an actuator) for rotating the driving rollers of the first to ninth transport roller pairs  21 - 29 . The first transport drive D 1  rotates the driving rollers of the first and second transport roller pairs  21  and  22 . The second transport drive D 2  rotates the driving rollers of the third to fifth transport roller pairs  23 - 25 . The third transport drive D 3  rotates the driving rollers of the sixth and seventh transport roller pairs  26  and  27 . The fourth transport driver D 4  rotates the driving rollers of the eighth and ninth transport roller pairs  28  and  29 . The first and second transport drives D 1  and D 2  and the third transport drive D 3  are examples of individual transport drives for driving a plurality of individual transporters (first to seventh transport roller pairs  21 - 27 ). The fourth transport drive D 4  and a transport drive (not illustrated) for driving the reception roller pair  132  are examples of joining transport drives for driving joining transporters (eighth and ninth transport roller pairs  28  and  29  and reception roller pair  132 ). The first to fourth transport drives D 1 -D 4  and the transport drive (not illustrated) for driving the reception roller pair  132  are examples of transport drives for driving transporters (first to ninth transport roller pairs  21 - 29  and reception roller pair  132 ). For example, media M may be transported by the first to ninth transport roller pairs  21 - 29  at a constant transport velocity. However, the first individual transport path P 1 , the second individual transport path P 2 , and the joining transport path P 3  may each attain a different transport velocity. Alternatively, the transport velocity of the inside of at least one of the first individual transport path P 1 , the second individual transport path P 2 , and the joining transport path P 3  may be different from the transport velocity of the inside of the other paths. 
     For example, the first entrance passage detection sensor S 11 , the first midstream passage detection sensors S 12 -S 14 , the first exit passage detection sensor S 15 , the second entrance passage detection sensor S 21 , the second midstream passage detection sensors S 22  and S 23 , and the second exit passage detection sensor S 24  may be reflecting or transmitting photoelectric sensors that detect passage of a medium M. 
     The first entrance passage detection sensor S 11  is disposed adjacent to the first transport roller pair  21  at a position downstream from the first transport roller pair  21  in the transport direction. The first midstream passage detection sensor S 12  is disposed adjacent to the second transport roller pair  22  at a position downstream from the second transport roller pair  22  in the transport direction. The first midstream passage detection sensor S 13  is disposed adjacent to the third transport roller pair  23  at a position downstream from the third transport roller pair  23  in the transport direction. The first midstream passage detection sensor S 14  is disposed adjacent to the fourth transport roller pair  24  at a position downstream from the fourth transport roller pair  24  in the transport direction. The first exit passage detection sensor S 15  is disposed adjacent to the fifth transport roller pair  25  at a position downstream from the fifth transport roller pair  25  in the transport direction. 
     It can be said that the first entrance passage detection sensor S 11  detects passage of a medium M in the vicinity of the entrance to the first individual transport path P 1  and that the first exit passage detection sensor S 15  detects passage of a medium M in the vicinity of the exit from the first individual transport path P 1 . 
     The second entrance passage detection sensor S 21  is disposed adjacent to the sixth transport roller pair  26  at a position downstream from the sixth transport roller pair  26  in the transport direction. The second midstream passage detection sensor S 22  is disposed adjacent to the seventh transport roller pair  27  at a position downstream from the seventh transport roller pair  27  in the transport direction. The second midstream passage detection sensor S 23  is disposed adjacent to the eighth transport roller pair  28  at a position downstream from the eighth transport roller pair  28  in the transport direction. The second exit passage detection sensor S 24  is disposed adjacent to the ninth transport roller pair  29  at a position downstream from the ninth transport roller pair  29  in the transport direction. 
     It can be said that the second entrance passage detection sensor S 21  detects passage of a medium M in the vicinity of the entrance to the second individual transport path P 2 , and that the second exit passage detection sensor S 24  detects passage of a medium M at a portion of the joining transport path P 3  in the vicinity of the exit of the medium feeding apparatus  1 . 
     The first entrance passage detection sensor S 11  and the second entrance passage detection sensor S 21  are each an example of an entry detection sensor that detects when a medium M fed from a feeder (first feeder  11  or second feeder  12 ) has entered a transport path (first individual transport path P 1  or second individual transport path P 2 ). The entry detection sensor is not particularly limited in terms of the detection position at a transport path (first individual transport path P 1  or second individual transport path P 2 ), and thus may be the first midstream passage detection sensor S 12  or the second midstream passage detection sensor S 22 . However, the entry detection sensor should be used to determine whether free spinning has occurred for a medium M, and is thus desirably disposed close to the first feeder  11  or the second feeder  12 . 
     The first midstream passage detection sensors S 12 -S 14 , the first exit passage detection sensor S 15 , the second midstream passage detection sensors S 22  and S 23 , the second exit passage detection sensor S 24 , and the paper stop sensor S 30  are each an example of a passage detection sensor that detects passage of a medium M at a position downstream from an entry detection sensor (first entrance passage detection sensor S 11  or second entrance passage detection sensor S 21 ) in the transport direction of the medium M and upstream from a take-in transporter (paper-stop-roller pair  131 ) in the transport direction. 
     The controller  31  depicted in  FIG. 2 , which is an example of a transport controller, includes a processor (e.g., central processing unit (CPU)) for functioning as an arithmetic processing apparatus for controlling the operations of the entirety of the medium feeding apparatus  1  and controls the components of the medium feeding apparatus  1 . For example, the controller  31  may control the first feeder  11 , the second feeder  12 , and the first to fourth transport drives D 1 -D 4  on the basis of a feed signal for a medium M that is received by the interface unit  33  (described hereinafter) from the interface unit  153  (controller  151 ) of the printing apparatus  101 . When a feed signal from the printing apparatus  101  is received by controllers disposed for the first feeder  11  and the second feeder  12 , these controllers may control the first feeder  11  and the second feeder  12 . When the medium feeding apparatus  1  is integral with a destination apparatus such as the printing apparatus  101 , the controller of the destination apparatus (e.g., the control unit  151  of the printing apparatus  101  (described hereinafter)) may function as the controller  31 . 
     For example, the storage unit  32  may include a memory such as a read only memory (ROM) consisting of a read-only semiconductor memory having a predetermined control program recorded therein in advance, or a random access memory (RAM) consisting of a randomly writable/readable semiconductor memory used as a working storage region on an as-needed basis when a processor executes various control programs. When the medium feeding apparatus  1  is integral with a destination apparatus such as the printing apparatus  101 , the storage unit of the destination apparatus (e.g., the storage unit  152  of the printing apparatus  101  (described hereinafter)) may function as the storage unit  32 . 
     The interface unit  33  communicates various information with external devices such as the printing apparatus  101 . For example, the interface unit  33  may receive, from the interface unit  153  of the printing apparatus  101 , information such as a feed signal for a medium M or a detection result provided by the paper stop sensor S 30 , and the controller  31  may control the operations of various components of the medium feeding apparatus  1  on the basis of the information. The interface unit  33  sends information such as a report pertaining to a retry mode  1  or  2  (described hereinafter) to the interface unit  153  of the printing apparatus  101 . 
     Next, descriptions are given of the printing apparatus  101 . 
     As depicted in  FIGS. 1 and 2 , the printing apparatus  101  includes a printing unit  110 , an attraction transporter  120 , a transporter  130 , the paper stop sensor S 30 , a destination transport path P 11 , a circulation inverting transport path P 12 , an inverting unit  140 , the controller  151 , the storage unit  152 , and the interface unit  153 . Note that  FIG. 1  depicts the joining transport path P 3  and the destination transport path P 11  by using a solid line and depicts the circulation inverting transport path P 12  by using a dashed line. 
     For example, the printing unit  110  may include line-head-type inkjet heads (not illustrated) for various colors to be used in printing. The printing unit  110  may use a printing scheme other than the inkjet printing scheme. 
     As depicted in  FIG. 1 , the attraction transporter  120  is disposed facing the printing unit  110 . The attraction transporter  120  transports a medium M by means of a transport belt while attracting the medium M. 
     The transporter  130  includes: the paper-stop-roller pair  131 , which corrects skew of a medium M transported toward the printing unit  110  upon the medium M abutting the paper-stop-roller pair  131 ; the reception roller pair  132 , which transports a medium M on the joining transport path P 3  continuous from the medium feeding apparatus  1 ; and a plurality of transport roller pairs  133  that transport a medium Mon the destination transport path P 11  or the circulation inverting transport path P 12 . The paper-stop-roller pair  131 , the reception roller pair  132 , and the plurality of transport roller pairs  133  transport a medium M in a nipping manner. 
     The paper-stop-roller pair  131  is an example of a take-in transporter (second conveyor) that takes media M transported by the above-described transporters (first to ninth transport roller pairs  21 - 29  and reception roller pair  132 ) onto, for example, the destination transport path P 11  in the printing apparatus  101 . The paper-stop-roller pair  131  is an example of a reference arrival position at the joining transport path P 3 . For example, media M may arrive at the paper-stop-roller pair  131  at reference arrival times having certain intervals therebetween. For example, media M may be taken in by the paper-stop-roller pair  131  at take-in times having certain intervals therebetween. A reference arrival time and a take-in time may be times with a duration. For each medium M, a reference arrival time and a take-in time may be set on the basis of, for example, a printing time of the printing unit  110  that corresponds to the size of the medium M or details of printing on the medium M, or the spaces between media M successively transported. The fact that a medium M arrives at the paper-stop-roller pair  131  after a reference arrival time can be used as information for deciding that a jam has occurred. When a medium M arrives at the paper-stop-roller pair  131  after a reference arrival time, the time at which the printing unit  110  starts printing will be delayed, or the accuracy in correction of skew will vary. Note that the reference arrival position may also be any position other than the paper-stop-roller pair  131 . 
     The paper stop sensor S 30  is disposed in the vicinity of the paper-stop-roller pair  131  at a portion of the joining transport path P 3  upstream from the paper-stop-roller pair  131  in the transport direction. The paper stop sensor S 30  is an example of an arrival detection sensor that is disposed at the joining transport path P 3  and detects an arrival time of a medium M. The arrival detection sensor may also be the second exit passage detection sensor S 24  disposed at the portion of the joining transport path P 3  within the medium feeding apparatus  1 . As described above, the medium feeding mechanism in the present embodiment includes the medium feeding apparatus  1 , the components on the transport route extending to the paper-stop-roller pair  131  in the printing apparatus  101  (the reception roller pair  132 , the paper-stop-roller pair  131 , the paper stop sensor S 10 , and the joining transport path P 3 ), and the controller  151  of the printing apparatus  101 . Hence, the reception roller pair  132  and the paper stop sensor S 30  can be said to be portions of the medium feeding mechanism. 
     The paper-stop-roller pair  131 , i.e., an example of the reference arrival position, is not provided with a sensor for detecting a medium M. Accordingly, it can be determined whether a medium M has arrived at the paper stop sensor  131  on the basis of a detection result provided by the paper stop sensor S 30 . 
     The destination transport path P 11  is coupled to the joining transport path P 3  continuous from the medium feeding apparatus  1  and extends downstream in the transport direction with reference the paper-stop-roller pair  131 . When the printing system  100  depicted in  FIG. 1  has disposed therewithin another printing apparatus and a medium ejection apparatus positioned downstream in the transport direction from the printing apparatus  101 , the destination transport path P 11  will be coupled to the transport paths within these apparatuses. 
     A medium M with one surface having undergone printing by the printing unit  110  is transported to the circulation inverting transport path P 12  so as to have the other surface thereof undergo printing. 
     The inverting unit  140  includes an inverting path for inverting the front and back sides of a medium M transported on the circulation inverting transport path R 12 , and a switchback roller pair. 
     The controller  151  depicted in  FIG. 2  includes a processor (e.g., CPU) that functions as an arithmetic processing apparatus for controlling the operations of the entirety of the printing apparatus  101 , and controls the components of the printing apparatus  101 . As will be described hereinafter in detail, on the basis of a report pertaining to the retry mode  1  or  2  received from the controller  31  of the medium feeding apparatus  1 , the controller  151  controls the paper-stop-roller pair  131  such that the take-in time for a medium M is delayed. Thus, it can be said that the controller  31  of the medium feeding apparatus  1  indirectly controls the paper-stop-roller pair  131  by using the controller  151  of the printing apparatus  101 . 
     For example, the storage unit  152  may include a memory such as a ROM consisting of a read-only semiconductor memory having a predetermined control program recorded therein in advance, or a RAM consisting of a randomly writable/readable semiconductor memory used as a working storage region on an as-needed basis when a processor executes various control programs. 
     The interface unit  153  communicates various information with the medium feeding apparatus  1  and external devices such as user terminals that transmit print data. For example, as described above, the interface unit  153  may send information such as a feed signal for a medium M or a detection result provided by the paper stop sensor S 30  to the interface unit  33  of the medium feeding apparatus  1 , and receive information such as a report pertaining to the retry mode  1  or  2  from the interface unit  33 . 
     The following describes an overview of operations of the printing system  100  while omitting, as appropriate, descriptions of matters that have already been given hereinbefore. 
     First, on the basis of a feed signal for media M received by the interface unit  33  from the printing apparatus  101  (interface unit  153 ), the controller  31  illustrated in  FIG. 2  controls the first feeder  11  and the second feeder  12  such that the media M are fed while switching between the first feeder  11  and the second feeder  12  depicted in  FIG. 1  or such that the media M are fed from only either of the first feeder  11  and the second feeder  12 . 
     The controller  31  controls the first to fifth transport roller pairs  21 - 25  by using the first transport drive D 1  and the second transport drive D 2  so as to transport, on the first individual transport path P 1 , a medium M fed from the first feeder  11 . Passage of the medium M being transported on the first individual transport path P 1  is detected by the first entrance passage detection sensor S 11 , the first midstream passage detection sensors S 12 -S 14 , and the first exit passage detection sensor S 15 . 
     The controller  31  also controls the sixth and seventh transport roller pairs  26  and  27  by using the third transport drive D 3  so as to transport, on the second individual transport path P 2 , a medium M fed from the second feeder  12 . Passage of a medium M being transported on the second individual transport path P 2  is detected by the second entrance passage detection sensor S 21  and the second midstream passage detection sensor S 22 . 
     The control unit  31  also controls the eighth and ninth transport roller pairs  28  and  29  by using the fourth transport drive D 4  so as to transport, on the joining transport path P 3 , a medium M transported from the first individual transport path P 1  or the second individual transport path P 2 . Passage of a medium M being transported on the joining transport path P 3  is detected by the second midstream passage detection sensor S 23  and the second exit passage detection sensor S 4 . 
     Accordingly, a medium M is fed to the printing apparatus  101  by being transported on the joining transport path P 3  continuous from the medium feeding apparatus  1 , and the passage (arrival) of the medium M is detected by the paper stop sensor S 30 . Subsequently, the medium M abuts the paper-stop-roller pair  131  and thus has skew thereof corrected, and then undergoes printing by the printing unit  110 . 
     The following describes details of an operation of feeding media M in the present embodiment by referring to  FIG. 4 . 
       FIG. 4  is a flowchart for illustrating an operation of feeding media M. 
     For example, the processes of the flowchart indicated in  FIG. 4  may start upon the controller  31  of the medium feeding apparatus  1  depicted in  FIG. 2  receiving a feed signal for media M from the controller  151  of the printing apparatus  101 . 
     The controller  31  of the medium feeding apparatus  1  determines whether a feed end instruction, which is sent from the controller  151  of the printing apparatus  101  in association with an end or suspension of printing, has been received (step S 41 ). 
     When a feed end instruction is received (step S 41 : YES), the controller  31  causes the first feeder  11 , the second feeder  12 , and the first to ninth transport roller pairs  21 - 29  to stop transporting media M (step S 42 ) and ends the feeding operation indicated in  FIG. 4 . 
     When a feed end instruction is not received (step S 41 : NO) but a feed signal is received (step S 43 ), the controller  31  determines whether a medium M will be transported (taken in) in the retry mode  2  (described hereinafter) (step S 44 ). When it is determined that a medium M will be transported in the retry mode  2  (step S 44 : YES), a new medium M will not be fed, so the controller  31  performs the processes again starting from step S 41 . 
     When determining that a medium M will not be transported in the retry mode  2  (step S 44 : NO), the controller  31  activates the transport belt  11   b  of the first feeder  11   b  or the transport belt  12   b  of the second feeder  12  (step S 45 ; e.g., times t 10  and t 13  in  FIG. 5 ). 
     The controller  31  updates an elapsed time T since the activation of the transport belt  11   b  or  12   b  (step S 46 ) and determines whether a medium M has passed an entry detection sensor (first entrance passage detection sensor S 11  or second entrance passage detection sensor S 21 ) (step S 47 ). 
     When a medium M has passed the entry detection sensor (step S 47 : YES; e.g., times t 11  and t 15  in  FIG. 5 ), the controller  31  determines whether the elapsed time T has exceeded a time T 2 , i.e., the end of a correction range (step S 48 ). In this example, the correction range, which is equal to or greater than T 1  and is equal to or less than T 2  (T 1 ≤T≤T 2 ), is a first range R 1  indicated in  FIG. 5 . The first range R 1  and a second range R 2  (described hereinafter) are not limited to the elapsed time T since the activation of the transport belt  11   b  or  12   b,  and may each be a time range that starts under another condition, e.g., a time range that starts at a time point at which the transport belt  11   b  or  12   b  reaches a predetermined rotation speed when the transport belt  11   b  or  12   b  is controlled to be activated. 
     When the elapsed time T is equal to or less than T 2  (step S 48 : NO), the controller  31  determines whether the elapsed time T precedes the time T 1 , i.e., the beginning of the first range R 1  (step S 49 ). 
     When the controller  31  determines that the elapsed time T is equal to or greater than the time T 1 , i.e., the beginning of the first range R 1  (step S 49 : NO), the first range R 1  satisfies the relationship of T 1 ≤T≤T 2  (e.g., time t 11  in  FIG. 5 ), so the controller  31  corrects the transport velocity of media M by controlling the first to fourth transport drives D 1 -D 4  such that the arrival times at which the media M arrive at the paper-stop-roller pair  131  become more constant (step S 50 ). The controller  151  of the printing apparatus  101  controls the paper-stop-roller pair  131  (a paper-stop drive for driving the paper-stop-roller pair  131 ) so as to take in a medium M at, for example, a time t 12  in  FIG. 5 , i.e., a take-in time set in advance. The controller  31  of the medium feeding apparatus  1  performs the processes again starting from step S 41 . 
     The following describes a correction of the transport velocity of media M by referring to  FIGS. 8 and 9 . 
       FIGS. 8 and 9  depict a relationship between a transport velocity and an elapsed time so as to illustrate a correction of the transport velocity. With respect to  FIGS. 8 and 9 , descriptions are given of examples pertaining to media M fed from the second feeder  12 . 
     In the example in  FIG. 8 , a passage timing (time t 41   a ) at which a medium M passes the second entrance passage detection sensor S 21  follows a reference passage time (time t 41 ), which is a theoretical value determined in advance, due to a low transport rate resulting from strong slippage between the medium M and the transport belt  12   b.  Thus, in order to make up for the delay of the medium M and thus make more constant the abutment times (arrival times) at which media M abut the paper-stop-roller pair  131  (reference abutment time (reference arrival time)), the controller  31  determines, for the section between the second entrance passage detection sensor S 21  and the second exit passage detection sensor S 24  (the second individual transport path P 2  and the joining transport path P 3 ), a transport velocity v 1  that is higher than a transport velocity v 0  for the section between the second exit passage detection sensor S 24  and the paper stop sensor S 30 . Note that the bold line in  FIG. 8  indicates a situation in which the transport velocity is not corrected, as will be described hereinafter. 
     In the example in  FIG. 9 , a medium M and the transport belt  12   b  have weak slippage therebetween and thus the transport rate is high, with the result that the passage time at which the medium M passes the second entrance passage detection sensor S 2  (time t 41   b ) precedes the reference passage time (time t 41 ), i.e., a theoretical value determined in advance. In this case, in order to make more constant the abutment times (arrival times) at which media M abut the paper-stop-roller pair  131  (reference abutment time (reference arrival time)), the controller  31  determines, for the section between the second entrance passage detection sensor S 21  and the second exit passage detection sensor S 24  (the second individual transport path P 2  and the joining transport path P 3 ), a transport velocity v 2  that is lower than the transport velocity v 0  for the section between the second exit passage detection sensor S 24  and the paper stop sensor S 30 . 
     The deviation of the passage time at which a medium M passes the second entrance passage detection sensor S 3  (time t 41   a  or t 41   b ) from the reference passage time (time t 41 ) may occur not only when an uppermost medium M floated by floating air and then separated from a medium M thereunder by separation air is attraction-transported by the transport belt  12   b,  but also may occur due to friction between a handling plate and an upper most medium M when separating the uppermost medium M from a medium M thereunder by using the handling plate. 
     Referring to  FIG. 4  again, when it is determined that the elapsed time T precedes the time T 1  (step S 49 : YES), it can be said that a medium M has arrived at the entry detection sensor before the first range R 1 , so the controller  31  reports a jam error to the controller  151  of the printing apparatus  101  (step S 51 ). Then, the controller  31  of the medium feeding apparatus  1  performs the processes again starting from step S 41 . For example, the controller  151  of the printing apparatus  101 , upon receipt of a jam error report, may send a feed end instruction to the controller  31  so as to stop the feeding of media M. 
     Referring to step S 48  again, it is determined that the elapsed time T has exceeded T 2  (step S 48 : YES) only when it is determined that the elapsed time T is equal to or less than a time T 3 , i.e., the end of the second range R 2 , through steps S 54 -S 56  (described hereinafter) before the medium M passages the entry detection sensor in step S 47 . Since the elapsed time falls within the second range R 2 , which satisfies the relationship of T 2 &lt;T≤T 3  (e.g., time t 15  in  FIG. 5 ), the controller  31  reports the retry mode  2  to the controller  151  of the printing apparatus  101  (step S 52 ). In this case, the controller  31  does not correct the velocity of media M (step S 53 ) and performs the processes again starting from step S 41 . 
     When the controller  31  of the medium feeding apparatus  1  reports the retry mode  2  to the controller  151  of the printing apparatus  101 , the controller  31  delays the feeding of a medium M to be transported next from the feeder (e.g., one feeding operation is canceled as indicated by time t 17  in  FIG. 5 ). As a result, the transport velocity is not corrected (a correction for increasing the transport velocity is not made); and, as indicated by a thick solid line in  FIG. 8 , the medium M continues to be transported at the transport velocity v 0 , with a passage time t 42   a  of arrival at the second exit passage detection sensor S 24  following a reference passage time t 42 , an arrival time t 43   a  of arrival at the paper stop sensor S 30  following a reference arrival time t 43 , and an abutment time t 44   a  (arrival time) of abutting the paper stop sensor  131  following a reference abutment time t 44 . However, as indicated in  FIG. 11 , a n-th medium M transported behind schedule (behind the schedule indicated by a dashed line) is not contacted by the next (n+1)-th medium M (medium M transported next) when the n-th medium M abuts the paper-stop-roller pair  131 , because the feeding of the (n+1)-th medium M is delayed by, for example, one feeding operation as described above. 
     When the controller  31  of the medium feeding apparatus  1  reports the retry mode  2  to the controller  151  of the printing apparatus  101 , the controller  151  of the printing apparatus  101  controls the paper-stop-roller pair  131  such that a take-in time for a medium M is delayed (e.g., cancel the take-in operation as indicated by time t 16  in  FIG. 5 ). For example, the controller  151  may control the paper-stop-roller pair  131  such that the medium M for which the take-in time has been delayed is taken in at a take-in time at which a medium M transported next was scheduled to be taken in (e.g., time  18  in  FIG. 5 ). 
     When reporting the retry mode  2 , the controller  31  may block the blowout of floating air A 2  by means of the floating air shutter  11   e  or  12   e  depicted in  FIG. 3  (e.g., time t 15  in  FIG. 5 ). In this way, a medium M that has been floating, as depicted in  FIG. 10A , over the placement mount  11   a ( 12   a ) by the floating-air blowout mechanism  11   d ( 12   d ) blowing out floating air A 2  falls because the blowout of floating air A 2  is blocked as depicted in  FIG. 10B  when the entry detection sensor (first entrance passage detection sensor S 11  or second entrance passage detection sensor S 21 ) detects a preceding medium M. Hence, multi-feeding with overlapped printing on multiple sheets can be suppressed. In a case where, as depicted in  FIG. 10B , the floating air shutter  11   e ( 12   e ) has been closed and thus blowout of floating air A 2  has been blocked, when reporting the retry mode  2 , the controller  31  may keep the floating air shutter  11   e ( 12   e ) closed until, for example, the next medium M is fed. 
     When reporting the retry mode  2 , the controller  31  may reschedule permissible times for each sensor, as indicated in  FIGS. 12A-12D . With respect to  FIGS. 12A-12D , descriptions are given of examples pertaining to media M fed from the first feeder  11 , with time measured in milliseconds. 
     As indicated in  FIG. 12A , with respect to an elapsed time T since the activation of the transport belt  11   b,  the first entrance passage detection sensor S 11  has a theoretical passage time of 100 and a permissible passage time of 80-120. For example, when the elapsed time T does not fall within the range of the permissible passage time, a nonarrival jam, i.e., an error indicating that a medium M has not been transported normally, may be reported to the controller  151 . The first entrance passage detection sensor S 11  has a permissible stagnation-jam time of  380 . When the elapsed time T has exceeded the stagnation jam, the stagnation jam, which is an error indicating that a medium M has been stagnating in the transport route, is reported to the controller  151 . 
     The first midstream passage detection sensor S 12  (first midstream passage detection sensor  1 ), which has a required time (required time for transport) of 50 with reference to the first entrance passage detection sensor S 11 , has a theoretical passage time of 150, a permissible passage time of 135-165, and a permissible jam time of 435. The range of the permissible passage time of the first midstream passage detection sensor S 12  is narrower than the range of the permissible passage time of the first entrance passage detection sensor S 11  because the times of arrival at the paper-stop-roller pair  131  are made more constant when the transport velocity is corrected as described above. 
     The first midstream passage detection sensor S 13  (first midstream passage detection sensor  2 ), which has a required time of 100 with reference to the first entrance passage detection sensor S 11 , has a theoretical passage time of 200, a permissible passage time of 190-210, and a permissible jam time of 490. 
     The first midstream passage detection sensor S 14  (first midstream passage detection sensor  3 ), which has a required time of 150 with reference to the first entrance passage detection sensor S 11 , has a theoretical passage time of 250, a permissible passage time of 245-255, and a permissible jam time of 545. 
     The first exit passage detection sensor S 15 , which has a required time of 200 with reference to the first entrance passage detection sensor S 11 , has a theoretical passage time of 300, a permissible passage time of 300, and a permissible jam time of 600. 
     The paper stop sensor S 30 , which has a required time of 250 with reference to the first entrance passage detection sensor S 11 , has a theoretical passage time of 350, a permissible passage time of 350, and a permissible jam time of 650. 
     As indicated above, when the elapsed time T falls within the second range R 2  that follows the first range R 1  (permissible passage time), the actual passage time of the first entrance passage detection sensor S 11  is a value exceeding the permissible passage time of 80-120 of the first entrance passage detection sensor S 11 , e.g., 140. Thus, the actual passage times of the other sensors are also expected to follow permissible passage times. 
     Accordingly, as indicated in  FIG. 12B , for example, the controller  31  may set, as expected passage time for each sensor, the sum of the actual passage time of the first entrance passage detection sensor S 11  ( 140 ) and the required time obtained with reference to the first entrance passage detection sensor S 11 . 
     As indicated in  FIG. 12C , the controller  31  updates the end of the permissible passage time of each sensor to a time that follows an expected passage time. The controller  31  also voids permissible stagnation-jam times or changes the same to moderately long times. 
     When the take-in time for a medium M is settled (e.g., time t 18  in  FIG. 5 ), the controller  31  updates, as indicated in  FIG. 12D , the permissible stagnation-jam times in accordance with the settled take-in time. 
     Referring again to the flowchart in  FIG. 4 , when a medium M does not pass the entry detection sensor (step S 47 : NO), the controller  31  determines, as in step S 48 , whether the elapsed time T has exceeded the time T 2 , i.e., the end of the first range R 1  (step S 54 ). When the elapsed time T is equal to or less than T 2  (step S 54 : NO), the controller  31  returns to step S 46 . 
     When the elapsed time T has exceeded the time T 2 , i.e., the end of the first range R 1  (step S 54 : YES), the controller  31  stops the transport belt  11   b ( 12   b ) (step S 55 ; e.g., time t 14  in  FIG. 5 ). 
     The controller  31  determines whether the elapsed time T has exceeded T 3 , i.e., the end of the second range R 2  (extended range) (step S 56 ). When the elapsed time T is equal to or less than T 3  (step S 56 : NO), the controller  31  returns to step S 46 . 
     When the elapsed time T has exceeded T 3  (step S 56 : YES; e.g., when the second range R 2  that starts at time t 24  in  FIG. 6  is exceeded), the controller  31  reports the retry mode  1  to the controller  151  of the printing apparatus  101  (step S 57 ) and performs the processes again starting from step S 41 . 
     When the controller  31  of the medium feeding apparatus  1  reports the retry mode  1  to the controller  151  of the printing apparatus  101 , the controller  151  controls the paper-stop-roller pair  131  so as to cancel the take-in operation for the medium M (e.g., time t 25  in  FIG. 6 ). Meanwhile, the controller  31  of the medium feeding apparatus  1  activates the transport belt  11   b ( 12   b ) of the feeder (first feeder  11  or second feeder  12 ) so as to feed a next medium M normally (e.g., time t 26  in  FIG. 6 , step S 45  in  FIG. 4 ). The controller  151  also controls the paper-stop-roller pair  131  so as to take in the next medium M at a take-in time set in advance (e.g., time  27  in  FIG. 6 ). 
     In the described embodiment, the medium feeding mechanism includes: the feeder (e.g., first feeder  11 , second feeder  12 ), i.e., an example of a feeder that feeds a medium M; the transport path (e.g., first individual transport path P 1 , second individual transport path P 2 , joining transport path P 3 ) coupled to the feeder; the transporter (e.g., first to ninth transport roller pairs  21 - 29 , reception roller pair  132 ), i.e., an example of a first conveyor that transports a medium M on the transport path; the transport drive (e.g., first to fourth transport drives D 1 -D 4 , the transport drive for the transporter  130 ) that drives the transporter; the entry detection sensor (e.g., first entrance passage detection sensor S 11 , second entrance passage detection sensor S 12 ) that detects when a medium M fed from the feeder has entered the transport path; the take-in transporter (e.g., paper-stop-roller pair  131 ), i.e., an example of a second conveyor that takes in a medium M transported by the transporter; and the controller (e.g., controllers  31  and  151 ), i.e., an example of a transport controller that controls the feeder and the take-in transporter. When the entry detection sensor detects entry of a medium M at a time that falls within a first range R 1  set in advance (e.g., time t 11  in  FIG. 5 ), the controller controls the take-in transporter so as to take in the medium M (e.g., time t 12  in  FIG. 5 ). When the entry detection sensor detects entry of a medium M at a time that falls within a second range R 2  that follows the first range R 1  (e.g., time t 15  in  FIG. 5 ), the controller controls the take-in transporter such that the take-in time for the medium M is delayed (e.g., set time t 18  in place of time t 16 ), and controls the feeder such that the feeding of a medium M to be transported next is delayed. 
     In the meantime, when a medium M has not arrived at the entry detection sensor (entrance passage detection sensor) yet at a predetermined time (e.g., time t 34 , i.e., the end of the first range R 1 ), even if the transport belt  11   b ( 12   b ) is stopped as indicated in  FIG. 7  (comparative example), the medium M may arrive at the entry detection sensor after the predetermined time (e.g., at time t 35 ) because the transport belt  11   b ( 12   b ) may not be capable of being stopped immediately. In this case, the feeding of the medium M is determined as being erroneous, so media M stop being fed, or the paper-stop-roller pair  31  (paper-stop drive) stops taking in a medium M (times t 37  and t 38 ). In the present embodiment, by contrast, when the entry detection sensor detects entry of a medium M at a time that falls within the second range R 2  following the first range R 1 , the time at which the medium M is taken in by the take-in transporter and the feeding of a medium M to be transported next are delayed, and thus when the entry detection sensor detects a medium M at a time that follows a reference passage time, the medium M can be transported without the need to correct the transport velocity. Accordingly, complicated components such as a high-performance motor for increasing the transport velocity do not need to be provided, and an error, such as a jam that could occur when the transport of a medium M is delayed even after the transport velocity is increased, can be prevented from occurring. 
     Therefore, the present embodiment allows a medium M transported in a delayed fashion to be reliably transported with the simple configuration. 
     In the present embodiment, when the entry detection sensor detects entry of a medium M at a time that falls within the second range (e.g., time t 15  in  FIG. 5 ), the controller controls the take-in transporter such that the medium M, for which a take-in time (e.g., time t 16 ) is delayed, is taken in at a take-in time at which a medium M to be transported next was scheduled to be taken in (e.g., time t 18 ). 
     Thus, the medium M can be continuously transported by merely skipping one take-in action by the take-in transporter for the medium M (e.g., time t 16  in  FIG. 5 ). Hence, the medium M can be transported through the simple control. 
     In the present embodiment, when the entry detection sensor detects entry of a medium M at a time that falls within the first range R 1 , the controller corrects the transport velocity of media M by controlling the transport drive such that the media M arrive at the take-in transporter at more constant arrival times (e.g., transport velocity v 1  in  FIG. 8 , transport velocity v 2  in  FIG. 9 ). When the entry detection sensor detects entry of a medium M at a time that falls within the second range R 2 , the controller does not make the correction of the transport velocity that is intended to make arrival times at which media M arrive at the take-in transporter more constant. 
     Accordingly, when the entry detection sensor detects a medium M at a time that falls within the first range R 1 , times at which media M arrive at the take-in transporter are made more constant, thereby, for example, preventing a time at which the printing unit  110  starts printing from being delayed and preventing the accuracy in correction of skew from varying. When the entry detection sensor detects a medium M at a time that falls within the second range R 2 , the controller delays a time at which the medium M is taken in by the take-in transporter (e.g., skip one take-in action), so that the medium M can be transported through the simple control in which the transport velocity is not corrected (correction for increasing the transport velocity is not made). 
     In the present embodiment, the medium feeding mechanism also includes the passage detection sensor that is positioned downstream from the entry detection sensor in the transport direction of a medium M and upstream from the take-in transporter in the transport direction and detects passage of the medium M (e.g., first midstream passage detection sensors S 12 -S 14 , first exit passage detection sensor S 15 , second midstream passage detection sensors S 22  and S 23 , second exit passage detection sensor S 24 , paper stop sensor S 30 ). When the entry detection sensor detects entry of a medium M at a time that falls within the second range R 2 , the controller reschedules the permissible times for detection of passage of a medium M by the passage detection sensor (e.g., the permissible passage times or permissible jam times in  FIGS. 12A-12D ). 
     Accordingly, when the transport velocity of a medium M fed in a delayed fashion and detected by the entry detection sensor at a time that falls within the second range R 2  is not corrected, an error, such as a jam resulting from the delayed transport of the medium M, can be suppressed from occurring. 
     In the present embodiment, the feeder includes: the placement mount  11   a ( 12   a ) on which media M are placed; the floating-air blowout mechanism  11   d ( 12   d ) that blows out floating air A 2  for floating at least an uppermost medium M 1  among the plurality of media M placed on the placement mount  11   a ( 12   a ); and the blocking part (e.g., the floating air shutters  11   e  and  12   e ) that blocks the blowout of floating air A 2  by the floating-air blowout mechanism  11   d ( 12   d ). When the entry detection sensor detects entry of a medium M at a time that falls within the second range R 2 , the controller causes the blocking part to block blowout of floating air A 2  (e.g., time t 15  in  FIG. 5 ). 
     In this way, multi-feeding of media M, which could occur when a medium M to be transported next to a medium M that has been fed at a delayed time is floated by floating air A 2 , can be suppressed from occurring. 
     Another Embodiment 
     In the one embodiment described above, when the first entrance passage detection sensor S 11  (second entrance passage detection sensor S 21 ) (an example of an entry detection sensor) detects entry of a medium M at a time that falls within the second range R 2  following the first range R 1  (e.g., time t 15  in  FIG. 5 ), the controller  31 ( 151 ) controls the paper-stop-roller pair  131  such that the take-in time of the paper-stop-roller pair  131  (an example of a take-in transporter (second conveyor)) is delayed to, for example, a time at which a medium M to be transported next is scheduled to be taken in (e.g., time t 18  is set in place of time t 16 ). 
     For example, a correction for increasing the transport velocity will not be made for a medium M of which entry has been detected by the second entrance passage detection sensor S 21  at a time that falls within the second range R 2 , although the medium M will be taken in by the paper-stop-roller pair  131  at a delayed time. Thus, the medium M is transported, as indicated in  FIG. 13 , at a prescribed transport velocity v 0  indicated by a one-dot chain line that is equal to the transport velocity of a medium M transported normally. As a result, the medium M is transported such that the passage time t 42   c  of passing the second exit passage detection sensor S 24  follows the reference passage time t 42 , the arrival time t 43   c  of arriving at the paper stop sensor S 30  follows the reference arrival time t 43 , and the abutment time t 44   c  (arrival time) of abutting the paper stop sensor  131  follows the reference abutment time t 44 . 
     However, when the abutment time t 44   c  of abutting the paper-stop-roller pair  131  is delayed as described above, e.g., when the take-in time for the medium M is delayed to a time at which a medium M to be transported next is scheduled to be taken in, the medium M will continue to abut the paper-stop-roller pair  131  until the take-in time. Hence, the accuracy in correction of skew of the medium M will be reduced. 
     In the present embodiment, accordingly, when a time at which entry is detected falls within the second range R 2 , the transport drive (e.g., fourth transport drive D 4 ) is controlled such that the transport of the medium M is temporarily stopped (or the transport velocity of the medium M is decreased) such that the medium M arrives at the paper-stop-roller pair  13  at a delayed time. The configuration of the printing system  100  in the present embodiment may be similar to that in the one embodiment described above, and the present embodiment is described herein only in terms of differences from the one embodiment described above. 
       FIG. 14  depicts a relationship between a transport velocity and an elapsed time so as to illustrate the stopping of transport. With respect to  FIG. 14 , descriptions are given of examples pertaining to media M fed from the second feeder  12 , as in the case of  FIG. 13 . 
     When a medium M and the transport belt  12   b  have strong slippage therebetween and thus the transport rate is low and the medium M passes the second entrance passage detection sensor S 21  at a passage time (time t 41   c ) that falls within the second range R 2  (e.g. , time t 15  in  FIG. 5 ), the passage time (time t 41   c ) follows the reference passage time (time t 41 ), i.e., a theoretical value determined in advance. 
     After the medium M passes the second entrance passage detection sensor S 21 , the controller  31  controls the third transport drive D 3  such that the transport velocity of the medium M increases to the transport velocity v 0 , as with the transport velocity of a medium M transported normally that is indicated by the one-dot chain line. The controller  31  temporarily stops the transport of the medium M while the leading edge of the medium M is situated between the second exit passage detection sensor S 24  and the paper-stop-roller pair  131 . 
     Before the medium M arrives at the paper-stop-roller pair  131 , the controller  31  controls the fourth transport drive D 4  such that the transport velocity of the medium M returns to the prescribed transport velocity v 0 . The timing at which the transport velocity of a medium M that was stopped by the controller  31  returns to the transport velocity v 0  like this may be adjusted by controlling the fourth transport drive D 4  and the transport drive for the transporter  130  such that the medium M arrives at the paper-stop-roller pair  131  at an arrival time at which a medium M to be transported next was scheduled to arrive at the paper-stop-roller pair  131  (reference abutment time t 52 ). In this case, the medium M arrives at the paper stop sensor S 30  at the time that is the same as the arrival time at which the medium M to be transported next was scheduled to arrive at the paper stop sensor S 30  (reference arrival time t 51 ). However, when the medium M arrives at the paper stop sensor S 30  before the arrival time at which the medium M to be transported next was scheduled to arrive at the paper stop sensor S 30  (reference arrival time t 51 ), the transport of the medium M may be temporarily stopped or the transport velocity of the medium M may be decreased, so as to shorten, to some degree, the period of time during which the medium M abuts the paper-stop-roller pair  131 . 
     In the example depicted in  FIG. 14 , the transport of the medium M is temporarily stopped. However, the period of time during which the medium M abuts the paper-stop-roller pair  131  may also be shortened by decreasing the transport velocity of the medium M to such a degree that the transport velocity does not decrease to 0. 
     In the present embodiment, the transport of the medium M may be temporarily stopped such that the medium M arrives at the paper-stop-roller pair  131  at a delayed time. This may be attained by performing temporal rescheduling such that the expected passage time and the end of the permissible passage time in the table in  FIG. 12D  for rescheduling the permissible times for the sensors (which are respectively 390 msec and 395 msec) are delayed to the expected passage time and the end of the permissible passage time in  FIG. 15  (which are respectively 705 msec and 710 msec). 
     In the meantime, the reception roller pair  132  depicted in  FIG. 1  nips a medium M that is relatively short in the transport direction but does not nip a medium M that is relatively long in the transport direction. This is intended to decrease the influence of the difference between the transport velocity attained by the first to fourth transport drives D 1 -D 4  on the medium-feeding-apparatus- 1  side and the transport velocity attained by the transport drives on the printing-apparatus- 10  side because a long medium M can be transported by the eighth transport roller pair  28 , the ninth transport roller pair  29 , and the paper-stop-roller pair  131 . Accordingly, when a long medium M is stopped or decelerated as described above, the leading edge thereof may be positioned between the reception roller pair  132  and the paper-stop-roller pair  131 ; and when a short medium M is stopped or decelerated as described above, the leading edge thereof may be positioned upstream from the reception roller pair  132 , and more desirably, the leading edge of the short medium M passes the reception roller pair  132  after being accelerated again (after returning to the transport velocity v 0 ). Meanwhile, when a medium M is stopped or decelerated as described above, control may be simply performed by the fourth transport drive D 4  alone without using the second transport drive D 2  and the third transport drive D 3  (in particular, the second transport drive D 2  disposed within the upper stage  1   a  of the medium feeding apparatus  1 , unlike the fourth transport drive D 4 ). 
     The other embodiment described so far can exhibit similar effects to the one embodiment in terms of similar matters, i.e., can exhibit the effect wherein a medium M fed in a delayed fashion can be reliably transported by means of the simple configuration. 
     In the present embodiment, when the entry detection sensor (e.g., first entry detection sensor S 11 , second entry detection sensor S 21 ) detects entry of a medium M at a time that falls within the second range R 2 , the controller (e.g., controller  31  or  151 ) controls the transport drive (e.g., fourth transport drive D 4 ) such that the transport of the medium M is temporarily stopped or the transport velocity of the medium M is decreased, such that the medium M arrives at the take-in transporter (e.g., paper-stop-roller pair  131 ) at a delayed time. 
     Accordingly, a medium M for which the take-in time has been delayed as described above due to the entry detection time falling within the second range R 2  (e.g., time t 18  is set in place of time t 16  in  FIG. 5 ) can be suppressed from abutting the take-in transporter for a long time. 
     In the present embodiment, after temporarily stopping the transport of a medium M or decreasing the transport velocity of the medium M, the controller controls the transport drive such that the transport velocity of the medium M returns to the prescribed transport velocity v 0  before the medium M arrives at the take-in transporter. 
     In this way, for the medium M for which the transport is temporarily stopped or the transport velocity is decreased, the transport control immediately before arrival at the take-in transporter can be performed, as in the case of a normally transported medium M for which the transport is not temporarily stopped and the transport velocity is not decreased. Hence, skew of the medium M for which the transport is temporarily stopped or the transport velocity is decreased can be corrected by performing control similar to the control for the normally transported medium M. 
     In the present embodiment, after temporarily stopping the transport of a medium M or decreasing the transport velocity of the medium M, the controller controls the transport drive such that the medium M arrives at the take-in transporter at an arrival time at which a medium M to be transported next was scheduled to arrive at the take-in transporter (e.g., reference abutment time  52  in  FIG. 14 ). 
     In this way, the medium M can be taken in by the take-in transporter soon, so that the medium M can be prevented from abutting the take-in transporter for a long time. 
     The present invention is not simply limited to the embodiments described herein. Components of the embodiments may be embodied in a varied manner in an implementation phase without departing from the gist of the invention. A plurality of components disclosed with reference to the described embodiments maybe combined, as appropriate, to achieve various inventions. For example, all of the components indicated with reference to embodiments may be combined as appropriate. Accordingly, various variations and applications can be provided, as a matter of course, without departing from the gist of the invention. The following indicates, as appendixes, the invention set forth in the claims of the corresponding Japanese application as originally filed. 
     In one aspect, the present application pertains to the following. 
     A medium feeding mechanism comprising: 
     a feeder that feeds a medium; 
     a transport path that is coupled to the feeder; 
     a transporter that transports the medium through the transport path; 
     a transport drive that drives the transporter; 
     an entry detection sensor that detects when the medium fed from the feeder has entered the transport path; 
     a take-in transporter that takes in the medium transported by the transporter; and 
     a controller that controls the feeder and the take-in transporter, wherein 
     when the entry detection sensor detects entry of the medium at a time that falls within a first range set in advance, the controller controls the take-in transporter so as to take in the medium, and 
     when the entry detection sensor detects entry of the medium at a time that falls within a second range following the first range, the controller controls the feeder so as to delay feeding of a medium to be transported next, and controls the take-in transporter so as to delay a take-in time for the medium. 
     In another aspect, when the entry detection sensor detects entry of the medium at a time that falls within the second range, the controller controls the take-in transporter such that the medium for which the take-in time has been delayed is taken in at a take-in time at which the medium to be transported next was scheduled to be taken in. 
     In another aspect, when the entry detection sensor detects entry of the medium at a time that falls within the first range, the controller corrects a transport velocity of the medium by controlling the transport drive such that media arrive at the take-in transporter at more constant arrival times, and 
     when the entry detection sensor detects entry of the medium at a time that falls within the second range, the controller does not make the correction of the transport velocity that is intended to make arrival times at which media arrive at the take-in transporter more constant. 
     In another aspect, the medium feeding mechanism further comprises a passage detection sensor that is positioned downstream from the entry detection sensor in a transport direction of the medium and upstream from the take-in transporter in the transport direction and detects passage of the medium, and 
     when the entry detection sensor detects entry of the medium at a time that falls within the second range, the controller reschedules a permissible time for detection of passage of the medium by the passage detection sensor. 
     In another aspect, the feeder includes a placement mount on which media are placed, a floating-air blowout mechanism that blows out floating air for floating at least an uppermost medium among the plurality of media placed on the placement mount, and a blocking part that blocks the blowout of the floating air by the floating-air blowout mechanism, and 
     when the entry detection sensor detects entry of the medium at a time that falls within the second range, the controller causes the blocking part to block the blowout of the floating air. 
     In another aspect, when the entry detection sensor detects entry of the medium at a time that falls within the second range, the controller controls the transport drive such that the transport of the medium is temporarily stopped or a transport velocity of the medium is decreased, so as to cause the medium to arrive at the take-in transporter at a delayed time. 
     In another aspect, after temporarily stopping the transport of the medium or decreasing the transport velocity of the medium, the controller controls the transport drive such that the transport velocity of the medium returns to a prescribed transport velocity before the medium arrives at the take-in transporter. 
     In another aspect, after temporarily stopping the transport of the medium or decreasing the transport velocity of the medium, the controller controls the transport drive such that the medium arrives at the take-in transporter at an arrival time at which the medium to be transported next was scheduled to arrive at the take-in transporter.