Patent Publication Number: US-9417584-B2

Title: Printer

Description:
TECHNICAL FIELD 
     The present invention relates to a printer that can perform double-sided printing. 
     BACKGROUND ART 
     In printers that can print on both sides of a printer paper, depending on the print unit, the paper is turned over and sent into the print unit again after printing on one side of the paper. In this manner, printing is performed by the print unit on the other side of the paper, and double-sided printing is realized. 
     The turning over of the paper is, for example, performed in the following manner. First, a paper that has been printed on one side is fed in a forward direction along the discharge route. Then, while the paper is being fed in a forward direction along the discharge route, the direction of movement of the paper is reversed and the paper is fed in the reverse direction. The paper fed in the reverse direction is then sent into the turnover route for turning over the paper. 
     When reversing the direction of movement for turning over the paper, there are cases when the paper cants diagonally relative to the direction of movement. When the paper cants diagonally, it becomes difficult to print the image appropriately. At this point, it is desirable to detect that the paper has canted diagonally. 
     For example, in Patent Literature 1, the degree to which the paper is diagonal is detected by detecting the edge face position of the feed direction of the paper using two sensors in different positions in the width direction and orthogonal to the feed direction of the paper. 
     PRIOR ART DOCUMENTS 
     Patent Literature 
     [Patent Literature 1] Japanese Unexamined Patent Application Publication No. 2003-155162 
     However, in the conventional technique, a plurality of sensors is required for detecting the end surface position of the paper. Further, high precision in the attachment position of the plurality of sensors is required because the difference in end surface position is used when the paper passes through diagonally. In this manner, in the conventional technique, a plurality of sensors is required and the man-hours for building the printer increases. 
     SUMMARY OF THE INVENTION 
     One or more embodiments of the present invention provide a printer that can reduce the number of sensors for determining abnormalities in the feed condition of sheet-shaped recording media. 
     In one or more embodiments of the present invention, a printer performs double-sided printing by turning over a recording medium (or “medium”) by reversing the direction of movement while the recording medium is being fed in the forward direction along a discharge route for discharging a printed sheet-shaped recording medium and feeding the recording medium in a reverse direction, including a displacement member (or “detection member”) disposed on the discharge route that displaces by contacting the recording medium, a detector for detecting the passage of an end edge of the recording medium as it is fed in the forward direction over the discharge route and the passage of the end edge of the recording medium as it is fed in the reverse direction over the discharge route by detecting the displacement of the displacement member, and a determining part for determining that the feed condition of the recording medium is abnormal when the value showing the difference between a forward feed amount of the recording medium from when the passage of the end edge of the recording medium during feeding in the forward direction is detected until the direction of movement of the recording medium is reversed and a reverse feed amount of the recording medium from when the direction of movement of the recording medium is reversed until the passage of the end edge of the recording medium during feeding in the reverse direction is detected is above a threshold. 
     According to one or more embodiments of the present invention, the passage of the end edge of the recording medium during feeding in the forward direction and the passage of the end edge of the recording medium during feeding in the reverse direction can be detected by detecting the displacement of the displacement member. Further, abnormalities in the feed condition of a sheet-shaped recording medium can be determined by using a forward feed amount and a reverse feed amount based on the passage of the end edge of the recording medium during feeding in the forward direction and the passage of the end edge of the recording medium during feeding in the reverse direction that are detected in this manner. In other words, if the displacement of the displacement member can be detected, abnormalities in the feed condition can be determined The displacement of the displacement member can be detected without using a plurality of sensors. Thus, the number of sensors for determining abnormalities in the feed condition of a recording medium can be reduced. 
     Further, according to one or more embodiments of the present invention, abnormalities in the feed condition can be determined by comparing the forward feed amount and the reverse feed amount. Thus, even when using recording mediums of a plurality of sizes, abnormalities in the feed conditions of the recording medium can be determined appropriately. In other words, abnormalities in the feed conditions can be determined more adaptively relative to the size of the recording medium than when comparing the reverse feed amount to a predetermined feed amount. 
     For example, the displacement member may be equipped with a long shaft supported to allow rotation around a width direction orthogonal to the direction of movement of the recording medium and extending in the width direction, and a plurality of levers, each extending to the route surface of the discharge route from the shaft, disposed apart from each other in the width direction; and the detector may detect the passage of the end edge of the recording medium during feeding in the forward direction over the discharge route and the passage of the end edge of the recording medium during feeding in the reverse direction over the discharge route by detecting the rotation of the shaft due to the contact of at least one of the plurality of levers contacting the recording medium. 
     According to one or more embodiments of the present invention, the passage of the end edge of the recording medium can be detected by detecting the rotation of the shaft due to the contact of the recording medium with at least one of the plurality of levers. Because the plurality of levers are disposed apart from each other in the width direction, the change in the reverse feed amount relative to the forward feed amount due to a slant in the recording medium relative to the direction of movement can be detected more accurately. In other words abnormalities in the feed condition of the recording medium can be determined more accurately. 
     For example, the printer may be able to perform double-sided printing on a recording medium of a first size and a recording medium of a second size that is smaller than the first size, and the plurality of levers may include a first lever and a second lever disposed in a position corresponding to both end parts in the width direction of the recording medium of the first size, and a third lever disposed in a position corresponding to one end part in the width direction of the recording medium of the second size. 
     According to one or more embodiments of the present invention, the third lever is disposed in a position corresponding to the end part of one side in the width direction of the recording medium of the second size, in a position between the first lever and the second lever. Thus, the change in the reverse feed amount relative to the forward feed amount due to the slant in the recording medium of the second size can be detected more accurately. In other words, in addition to the recording medium of the first size, abnormalities in the feed condition of the recording medium of the second size can be detected more accurately. 
     For example, each of the plurality of levers may have a slanted part that is disposed canting in the reverse direction relative to the route surface of the discharge route and that collides with the end edge of the recording medium being fed in the forward direction over the discharge route. 
     According to one or more embodiments of the present invention, in each lever, a slanted part is formed on the part colliding with the end edge of the recording medium fed in the forward direction over the discharge route disposed canted in the reverse direction relative to the route surface of the discharge route. Thus, the force placed on the recording medium when colliding can be suppressed, allowing for a more stable feed of the recording medium. According to one or more embodiments of the present invention, a printer that reverses a direction of movement of the recording medium, comprises a detection member that detects a slant in the recording medium relative to the direction of movement of the recording medium, based on at least two contact points between the detection member and the recording medium. 
     In one or more embodiments of the present invention, a printer can determine abnormalities in the feed condition of a sheet-shaped recording medium and suppress the increase of man-hours for building. 
     According to one or more embodiments of the present invention, a method for detecting an abnormal feed condition of a recording medium in a printer that reverses a direction of movement of the recording medium, comprises: detecting a forward passage of an end edge of the recording medium fed in a forward direction and a reverse passage of the end edge of the recording medium fed in a reverse direction; and determining whether a difference between a forward feed amount of the recording medium fed in the forward direction and a reverse feed amount of the recording medium fed in the reverse direction is above a threshold. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view illustrating the exterior appearance of a printer according to one or more embodiments of the present invention. 
         FIG. 2  is a drawing illustrating the feed route of the paper inside a printer according to one or more embodiments of the present invention. 
         FIG. 3is  a perspective view of the displacement member of a printer according to one or more embodiments of the present invention. 
         FIG. 4  (a) is a drawing for describing the displacement member of a printer according to one or more embodiments of the present invention. 
         FIG. 4  (b) is a drawing for describing the displacement member of a printer according to one or more embodiments of the present invention. 
         FIG. 5  is a block drawing illustrating the function configuration of a printer according to one or more embodiments of the present invention. 
         FIG. 6  is a flow chart showing the processes of a printer according to one or more embodiments of the present invention. 
         FIG. 7  (a) is a drawing for describing the processes of a printer according to one or more embodiments of the present invention. 
         FIG. 7  (b) is a drawing for describing the processes of a printer according to one or more embodiments of the present invention. 
         FIG. 7  (c) is a drawing for describing the processes of a printer according to one or more embodiments of the present invention. 
         FIG. 8  (a) is a drawing for describing the processes of a printer according to one or more embodiments of the present invention when the feed condition is normal. 
         FIG. 8  (b) is a drawing for describing the processes of a printer according to one or more embodiments of the present invention when the feed condition is normal. 
         FIG. 8  (c) is a drawing for describing the processes of a printer according to one or more embodiments of the present invention when the feed condition is normal. 
         FIG. 9(a)  is a drawing for describing the processes of a printer according to one or more embodiments of the present invention when the feed condition is abnormal. 
         FIG. 9(b)  is a drawing for describing the processes of a printer according to one or more embodiments of the present invention when the feed condition is abnormal. 
         FIG. 9(c)  is a drawing for describing the processes of a printer according to one or more embodiments of the present invention when the feed condition is abnormal. 
         FIG. 10  is a drawing illustrating the difference between the forward feed amount and the reverse feed amount of a printer according to one or more embodiments of the present invention. 
         FIG. 11  is a perspective view of the displacement member of a printer of modification 1 according to one or more embodiments of the present invention. 
         FIG. 12  is a perspective view of the displacement member of a printer of modification 2 according to one or more embodiments of the present invention. 
         FIG. 13  is a perspective view of the displacement member of a printer of modification 3 according to one or more embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the present invention are described in detail below with reference to drawings. 
     Embodiments described below show an exhaustive and specific example. The numerical values, materials, configuration elements, the arrangement position of the configuration elements, and connection configuration and the like shown in the embodiments below are one example, and are not meant to limit the scope of the claims. Further, among the configuration elements of the embodiments below, configuration elements not stated in an independent claim are described as arbitrary configuration elements. 
     (Embodiments) 
     [Physical Configuration of the Printer] 
     A physical configuration of a printer  100  in accordance with one or more embodiments of the present invention is described first.  FIG. 1  is a perspective view showing an exterior view of the printer  100  according to one or more embodiments of the present invention. 
     The printer  100  performs double-sided printing by turning over the paper by feeding the paper in a reverse direction by reversing the direction of movement while the paper is fed in the forward direction along the discharge route for discharging the printed paper. In one or more embodiments of the present invention, the printer  100  is a laser printer. 
     As illustrated in  FIG. 1 , the printer  100  is equipped with a chassis  101 , a discharge port  102  formed on the chassis  101 , a catch tray  103 , and a paper cassette  104 . 
     The discharge port  102  is an aperture through which printed paper is discharged from the interior of the chassis  101 . When double-sided printing is performed, the direction of movement of a paper printed on one side (first side) is reversed while it is being discharged from the discharge port  102 , and returns to the interior of the chassis  101 . 
     The catch tray  103  is formed on the upper surface of the chassis  101 . The paper discharged from the discharge port  102  sits on the catch tray  103 . 
     The paper cassette  104  is provided on the lower part of the chassis  101 , and is stored in the chassis  101  such that it can be drawn out. Printing paper is stacked in the paper cassette  104 . 
     The feed route of the paper within the printer  100  is described next.  FIG. 2  is a drawing that illustrates the feed route within the printer  100  in accordance with one or more embodiments of the present invention. The printer  100  is equipped with a feed roller  110 , a print unit  120 , and a displacement member  130 . Also, on the interior of the printer  100 , a supply route  111 , a discharge route  112 , and a reverse route  113  are formed. 
     The feed roller  110  feeds a paper  200  along the supply route  111 , the discharge route  112 , and the reverse route  113 . The feed roller  110  feeds the paper  200  by rotating via a drive source (not pictured). 
     The supply route  111  is a route for supplying the paper  200  placed in the paper cassette  104  to the print unit  120 . The paper  200  is fed along the supply route  111  by the feed roller  110 , and is supplied from the paper cassette  104  to the print unit  120 . 
     The print unit  120  prints an image on the upper side of the paper  200 . In other words, an image is printed on one side (first side) of the paper  200  arriving at the print unit  120  from the supply cassette  104 . 
     Specifically, the print unit  120  contains a photoreceptor drum  121 , a transcription roller  122 , and a fixing roller  123 . A toner image is formed on the surface of the photoreceptor drum  121 . The toner image formed on the surface of the photoreceptor drum  121  is transcribed onto the upper surface of the paper  200  by the transcription roller  122 . Then, the fixing roller  123 , by adding heat and pressure to the toner image transcribed onto the upper surface of the paper  200 , fixes the toner image onto the paper  200 . 
     The discharge route  112  is a route for discharging the paper  200  that has been printed by the print unit  120  to the catch tray  103 . The printed paper  200  is fed along the discharge route  112  by the feed roller  110 , and is discharged to the exterior of the chassis  101  from the discharge port  102 . The direction in which the paper  200  is discharged to the exterior of the chassis  101  is called the forward direction. 
     When double-sided printing is performed, the paper  200  on which an image has been printed on only one side reverses its direction of movement while being discharged from the discharge port  102 , and returns to the interior of the chassis  101 . The direction in which the paper  200  returns to the interior of the chassis  101  is called the reverse direction. 
     The reverse route  113  is a route for turning over the paper  200 . The paper  200  fed in the reverse direction along the discharge route  112  enters the reverse route  113 . Then, the paper  200  fed along the reverse direction  113  by the feed roller  110  is supplied again to the print unit  120 . 
     At this point, the bottom side of the paper  200  supplied again to the print unit  120  is the first side onto which an image has already been printed. In other words, the upper side of the paper  200  is a second side opposite the first side. Thus, an image is printed onto the second side of the paper  200  supplied again to the print unit  120 . In other words, an image is printed onto both sides of the paper  200 . p The paper  200  onto which an image has been printed on both the first side and the second side is fed along the discharge route  112 , discharged to the exterior of the chassis  101  from the discharge port  102 , and is placed in the catch tray  103 . 
     The displacement member  130  is installed on the discharge route  112 , and is displaced by contacting the paper  200 . Details of the displacement member  130  are described below using  FIG. 3  and  FIG. 4 . 
       FIG. 3  is a perspective view of the displacement member  130  of the printer  100  in one or more embodiments of the invention.  FIG. 4  is a drawing for describing the displacement of the displacement member  130  of the printer  100  according to one or more embodiments of the present invention. 
     The displacement member  130  is equipped with a shaft  131  and a plurality of levers  132 , as illustrated in  FIG. 3 . 
     The shaft  131  is a long member extending in the width direction (Y-axis direction) orthogonal to the direction of movement of the paper  200  (X-axis direction). Here, the shaft  131  is disposed above the route surface  112   a  of the discharge route  112 . 
     The plurality of levers  132  each extend from the shaft  131  to the route surface  112   a  of the discharge route  112 , and are disposed apart from each other in the width direction (Y-axis direction). In other words, the plurality of levers  132  are provided on the shaft  131  and are disposed such that they protrude toward the route surface  112   a  of the discharge route  112 . 
     As illustrated in  FIG. 4  (a), each of the plurality of levers  132  are disposed crossing the route surface  112   a  of the discharge route  112  when not in contact with the paper  200 . Thus, as illustrated in  FIG. 4  (b), the paper  200  fed over the discharge route  112  contacts the plurality of levers  132 , and push up on the plurality of levers  132 . As a result, the shaft  131  rotates. 
     Further, as illustrated in  FIG. 3  and  FIG. 4 , each of the plurality of levers  132  has a slanted part  136  disposed leaning in a reverse direction relative to the route surface  112   a  of the discharge route  112 . In other words, an acute angle is formed by the slanted part  136  and the route surface  112   a  positioned in the reverse direction (the negative X-axis side) from the slanted part  136 . The slanted part  136  collides with the end edge of the direction of movement of the paper  200  fed in the forward direction over the discharge route  112 . 
     In one or more embodiments of the present invention, the plurality of levers  132  contains a first lever  133 , a second lever  134 , and a third lever  135 . 
     The first lever  133  and the second lever  134  are disposed in a position corresponding to both end parts in the width direction (Y-axis direction) of the paper  200 . In other words, the first lever  133  is disposed in a position that one end part in the width direction of the paper  200  passes through. The second lever  134  is disposed in a position that the other end part in the width direction of the paper  200  passes through. Here, the first lever  133  and the second lever  134  are each provided on the end portions in the longitudinal direction (Y-axis direction) of the shaft  131 . 
     The third lever  135  is disposed between the first lever  133  and the second lever  134 . Here, the third lever  135  is provided at the center point of the first lever  133  and the second lever  134  in the longitudinal direction of the shaft  131 . 
     [Function Configuration of the Printer] 
     The function configuration of the printer  100  in accordance with one or more embodiments of the present invention is described next.  FIG. 5  is a block drawing illustrating the function configuration of the printer  100  according to one or more embodiments of the present invention. 
     As illustrated in  FIG. 5 , the printer  100  is equipped with a detector  141 , determining part  142 , and a controller  143 . 
     The detector  141 , by detecting the displacement of the displacement member  130 , detects the passage of the end edge of the paper  200  while being fed in the forward direction over the discharge route  112 , and the passage of the end edge of the paper  200  while it is being fed in the reverse direction over the discharge route  112 . 
     In other words, when the paper  200  is fed in the forward direction, the detector  141  detects that the front side end edge of the paper  200  in the direction of movement (forward direction) has contacted one of the plurality of levers  132 . Said differently, when the paper  200  is fed in the forward direction, the detector  141  detects the passage of the front end edge of the paper  200 . 
     When the paper  200  is fed in the reverse direction, the detector  141  detects that the back end edge of the paper  200  in the direction of movement (reverse direction) has passed the plurality of levers  132 . Said differently, when the paper  200  is fed in the reverse direction, the detector  141  detects the passage of the back end edge of the paper  200 . 
     Specifically, the detector  141 , for example, detects the displacement of the displacement member  130  by detecting the rotation conditions of the shaft  131 . More specifically, the detector  141 , for example, detects the displacement of the displacement member  130  by detecting the front end portion of the L-shaped protrusion protruding from the longitudinal end portion of the shaft  131  using a photointerruptor. In this case, for example when the signal from the photointerruptor switches from “ON” to “OFF”, the detector  141  detects the passage of the end edge of the paper  200  while it feeds in the forward direction over the discharge route  112 . Meanwhile, for example when the signal from the photointerruptor switches from “OFF” to “ON”, the detector  141  detects the passage of the end edge of the paper  200  in the reverse direction over the discharge route  112 . 
     The determining part  142  determines the feed condition of the paper  200  as abnormal when the value showing the difference between the forward feed amount of the paper  200  and the reverse feed amount of the paper  200  is above threshold. Here, the forward feed amount is the feed amount of the paper  200  from when the passage of the end edge of the paper  200  being fed in the forward direction is detected until the direction of movement of the paper  200  is reversed. The reverse feed amount is the feed amount from when the direction of movement of the paper  200  is reversed until the passage of the end edge of the paper  200  being fed in the reverse direction is detected. 
     Feed amount corresponds to the distance the paper  200  is fed. Specifically, feed amount is, for example, the number of rotations of the feed roller  110 . As another example, when the absolute value of the acceleration of the paper  200  in the forward direction and in the reverse direction is equal, the feed amount may be the time required for feeding. 
     The value showing the difference between the forward feed amount and the reverse feed amount is, for example, the absolute value of the difference between the forward feed amount and the reverse feed amount, the difference between the forward feed amount and the reverse feed amount squared, or a ratio of the forward feed amount relative to the reverse feed amount. The value showing the difference between the forward feed amount and the reverse feed amount need not be limited to these. 
     The threshold is experientially or experimentally determined beforehand. The smaller the threshold is, the more likely it becomes that the feed condition is determined to be abnormal. For example, when the threshold is “ 0 ”, the determining part  142  determines the feed condition to be abnormal if the forward feed amount and reverse feed are not equal. 
     The controller  143  controls various operations of the printer  100 . For example, the controller  143  controls the feed of the paper  200  by controlling the rotation of the feed roller  110 . Also, the controller  143  may alert the user of an abnormality in the feed condition by igniting a lamp (not pictured). 
     [Operation of the Printer] 
     The operation of the printer  100  configured as above is described.  FIG. 6  is a flow chart illustrating the processes of the printer  100  in accordance with one or more embodiments of the invention.  FIG. 7  is a drawing for describing the processes of the printer  100  according to one or more embodiments of the present invention.  FIG. 8  is a drawing for describing the processes when the feed condition of the printer  100  according to one or more embodiments of the present invention is normal.  FIG. 9  is a drawing for describing the processes when the feed condition of the printer  100  according to one or more embodiments of the present invention is abnormal. 
     First, the controller  143  performs printing on the first side of the paper  200  by controlling the print unit  120  (S 101 ). Continuing, the controller  143  feeds the paper  200  in the forward direction along the discharge route  112  by controlling the rotation of the feed roller  110  (S 102 ). As a result, the paper  200  is fed in the forward direction as illustrated in  FIG. 7  (a). 
     The detector  141  detects the passage of the front-side end edge  201  of the paper  200  as it is fed in the forward direction (S 103 ). As illustrated in  FIG. 7  (b), when the front-side end edge  201  in the direction of movement of the paper  200  passes under the displacement member  130 , the passage of the front end portion of the end edge  201  of the paper  200  is detected by the displacement of the displacement member  130  when it contacts the paper  200 . 
     The controller  143  reverses the direction of movement of the paper  200  (S 104 ). In other words, the controller  143  feeds the paper  200  in the reverse direction be reversing the direction of rotation of the feed roller  110 . In the positions illustrated in  FIG. 7  (c),  FIG. 8  (a), and  FIG. 9  (a), the direction of movement of the paper  200  is reversed. Then, as illustrated in  FIG. 8  (b) and  FIG. 9  (b), the paper  200  is fed in the reverse direction. 
     Next, the detector  141  detects the passage of the rear-side end edge  201  of the paper  200  as it is fed in the reverse direction (S 105 ). As illustrated in  FIG. 8  (c) and  FIG. 9  (c), when the rear-side end edge  201  in the direction of movement of the paper  200  passes under the displacement member  130 , the passage of the rear end portion of the end edge  201  of the paper  200  is detected by the displacement member  130  returning to its original position, being no longer in contact with the paper  200 . 
     Next, the determining part  142  determines whether the value showing the difference between the forward feed amount and the reverse feed amount is below threshold (S 106 ). Here, the value showing the difference between the forward feed amount and the reverse feed amount is the absolute value of the difference between the forward feed amount and the reverse feed amount. 
     Here, when the value showing the difference between the forward feed amount and the reverse feed amount is below threshold (Yes of S 106 ), the determining part  142  determines the feed condition of the paper  200  as normal (S 107 ). As a result, the feeding of the paper  200  continues. Then, the paper  200  is fed along the reverse route  113 , and is supplied to the print unit  120  in a state of having been turned over. The reason it is determined in this manner is described later using  FIG. 10 . 
     Further, the controller  143  performs printing on the second side of the paper  200  by controlling the print unit  120  (S 108 ). The paper  200  with a printed image on both the first side and the second side is fed along the discharge route  112  and discharged into the catch tray  103 . 
     Meanwhile, if the value showing the difference between the forward feed amount and the reverse feed amount is above threshold (Yes of S 106 ), the determining part  142  determines the feed condition of the paper  200  as abnormal (S 109 ). The reason it is determined in this manner is described later using  FIG. 10 . 
     Then, the controller  143  stops the feed of the paper  200  (S 110 ). Further, the controller  143  alerts the user that the feed condition of the paper  200  is abnormal. 
     Here, the reason for determining the feed condition of the paper  200  as normal/abnormal in step S 107  and step S 109  of  FIG. 6  is described.  FIG. 10  is a chart showing the difference between the forward feed amount and the reverse feed amount of the printer  100  according to one or more embodiments of the present invention. In  FIG. 10 , a paper  200   a  and a paper  200   b  are both shown in the position where the passage of the end edge is detected as they are fed in the reverse direction over the discharge route  112 . 
     When the feed condition is normal, the paper  200   a  is fed in a condition such that it is not canted relative to the direction of movement, as illustrated in  FIG. 10  with a dotted line. That is, the end edge  201   a  of the paper  200   a  is perpendicular to the movement direction. In this case, the forward feed amount and the reverse feed amount of the paper  200   a  are substantially equal. Thus, when the value showing the difference between the forward feed amount and the reverse feed amount is below threshold, the determining part  142  determines the feed condition of the paper  200   a  as being normal. 
     Meanwhile, when the feed condition is abnormal, the paper  200   b  is fed in a condition such that it is canted relative to the direction of movement, as illustrated in  FIG. 10  with a solid line. That is, the end edge  201   b  of the paper  200   b  is not perpendicular to the movement direction. In this case, the reverse feed amount of the paper  200   b  is larger than the reverse feed amount of the paper  200   a  by distance D. In other words, the forward feed amount and the reverse feed amount of the paper  200   b  are not equal. Thus, when the value showing the difference between the forward feed amount and the reverse feed amount is above threshold, the determining part  142  determines the feed condition of the paper  200   b  as being abnormal. 
     [Effects of One or More Embodiments of the Invention] 
     According to one or more embodiments of the printer  100  of the present invention, the passage of the end edge  201  of the paper  200  as it is fed in the forward direction and the passage of the end edge  201  of the paper  200  as it is fed in the reverse direction can be detected by the displacement of the displacement member  130 . Further, abnormalities in the feed conditions of the paper  200  can be determined by using the forward feed amount and the reverse feed amount based on the detection of the passage of the end edge  201  of the paper  200  as it is fed in the forward direction and the passage of the end edge  201  of the paper  200  as it is fed in the reverse direction. In other words, if the displacement of the displacement member  130  can be detected, abnormalities in feed condition can be determined. The displacement of the displacement member  130  can be detected without using a plurality of sensors. Thus, the number of sensors for determining abnormalities in the feed condition of the paper  200  can be reduced. 
     Also, according to one or more embodiments of the printer  100  of the present invention, abnormalities in feed condition can be determined by comparing the forward feed amount and the reverse feed amount. Thus, even when the paper  200  is used in a plurality of sizes, abnormalities in the feed condition of the paper  200  can be appropriately determined. In other words, abnormalities in the feed condition can be more adaptively determined relating to the size of the paper  200  than when comparing the reverse feed amount to a feed amount determined beforehand. 
     Also, according to one or more embodiments of the printer  100  of the present invention, by detecting the rotation of the shaft  131  due to the contact of the paper  200  with at least one from among the plurality of levers  132 , the passage of the end edge  201  of the paper  200  can be detected. Because the plurality of levers  132  are disposed apart from each other in the width direction, the change in the reverse feed amount relative to the forward feed amount due to a slant in the paper  200  relative to the direction of movement can be detected more accurately. In other words, abnormalities in the feed condition of the paper  200  can be determined more accurately. 
     Also, according to one or more embodiments of the printer  100  of the present invention, within each of the plurality of levers  132 , a slanted part  136  is formed on the portion colliding with the end edge  201  of the paper  200  that is fed in the forward direction over the discharge route  112  disposed canted in the reverse direction relative to the route surface  112   a  of the discharge route  112 . Thus, the force placed on the paper  200  when colliding can be suppressed, allowing for a more stable feed of the paper  200 . 
     (Modification 1) 
     Next, a modification 1 of the embodiments is described. In one or more embodiments of the present modification, the number of levers contained in the displacement member is different than in the above embodiments. The displacement member is described below centered on points that differ from the above embodiments. 
       FIG. 11  is a perspective view of a displacement member  130 A of the printer according to one or more embodiments of the modification 1. In  FIG. 11 , identical symbols are used for configuration elements identical to  FIG. 3 , and their description is omitted. 
     The displacement member  130 A has two levers  132 A. The two levers  132 A contain a first lever  133  and a second lever  134 . In other words, in the displacement member  130 A of the present modification, the third lever  135  contained in the displacement member  130  of the above embodiments is missing. However, because the first lever  133  and the second lever  134  are provided, the displacement member  130 A can accurately detect the passage of the end edge  201  of the paper  200  if, for example, the size of the paper  200  is constant. 
     As above, even with the displacement member  130 A of the present modification, if, for example, the size of the paper  200  is constant, an abnormality in the feed condition of the paper  200  can be detected. 
     (Modification 2) 
     A modification 2 of the embodiments is described next. In one or more embodiments of the present modification, the shape and number of the lever contained in the displacement member is different than the above embodiments. The displacement member is described below centered on points that differ from the above embodiments. 
       FIG. 12  is a perspective view of the displacement member  130 B of the printer according to one or more embodiments of the modification 2. In  FIG. 12 , identical symbols are used for configuration elements identical to  FIG. 3 , and their description is omitted. 
     The displacement member  130 B is equipped with a shaft  131  and a lever  132 B. The lever  132 B is provided longitudinally over the shaft  131 , and is a plate-shaped member disposed so it protrudes facing the route surface  112   a  of the discharge route  112 . Even when the lever  132 B is shaped in this manner, the displacement member  130 B can accurately detect the passage of the paper  200 . 
     As above, even with the displacement member  130 B of the present modification, abnormalities in the feed condition of the paper  200  can be detected. 
     (Modification 3) 
     A modification 3 of the embodiments is described next. In one or more embodiments of the present modification, the position of the lever contained in the displacement member is different than the above embodiments. The displacement member is described below centered on points that differ from the above embodiments. 
       FIG. 13  is a drawing illustrating the relationship between the displacement member  130 C of the printer according to one or more embodiments of the modification 3 and a paper. In  FIG. 13 , identical symbols are used for configuration elements identical to  FIG. 3 , and their description is omitted. 
     The printer  100  of the present modification can perform double-sided printing on a paper  200  of a first size, and a paper  202  of a second size that is smaller than the first size. 
     The displacement member  130 C is equipped with a shaft  131  and a plurality of levers  132 C. The plurality of levers  132 C contains a first lever  133 C, a second lever  134 C, and a third lever  135 C. In the present modification, the shape and size of the first lever  133 C, the second lever  134 C, and the third lever  135 C are the same shape and size as the first lever  133 , the second lever  134 , and the third lever  135  of the embodiments. 
     The first lever  133 C and the second lever  134 C are disposed in position corresponding to both end parts of the paper  200  of the first size. In other words, the first lever  133 C and the second lever  134 C are disposed at the passing position of both end parts of the paper  200  of the first size. 
     The third lever  135 C is disposed in a position between the first lever  133 C and the second lever  134 C, in the position corresponding to the end part of one end of the paper  202  of the second size. The second lever  134 C is disposed in the position corresponding to the other end part of the paper  202  of the second size. In other words, the second lever  134 C and the third lever  135 C are disposed at the passing position of both end parts of the paper  202  of the second size. 
     As above, according to the displacement member  130 C of the present modification, the third lever  135 C is disposed in a position corresponding to one end part in the width direction of the paper  202  of the second size, in a position that is between the first lever  133 C and the second lever  134 C. Thus, the change in the reverse feed amount relative to the forward feed amount due to a slant in the paper  202  of the second size can be detected more accurately. In other words, in addition to the paper  200  of the first size, abnormalities in the feed condition of the paper  202  of the second size can be more accurately determined. 
     (Other Modifications) 
     Embodiments of the present invention were described above, but the present invention is not limited to these embodiments. To the extent that it does not deviate from the meaning of the present invention, a variety of modifications as conceived by a person ordinary skill in the art applied to one or more embodiments of the present invention are included in the scope of the present invention. 
     For example, in the above embodiments, the printer was a laser printer, but it is not limited to this. For example, the printer may be an inkjet printer. 
     In the above embodiments, double-sided printing was performed on a paper, but is not limited to this. The printer may, for example, perform double-sided printing on a sheet-shaped polymer, metal, cloth, or the like. In other words, the object of printing and feeding is a sheet-shaped recording medium. 
     In the above embodiments, an example wherein the detector detected the rotation of the shaft of the displacement member using a photointerrupter, but it is not necessary to use a photointerrupter. For example, the detector may detect the rotation of the shaft of the displacement member using a photoreflector. In other words, the detector may detect in any manner if it can detect the displacement of the displacement member due to the paper passing through. 
     In the above embodiments, the number of levers was three or fewer, but it may be four or more. Also, the shape and size of the lever need not be limited to the size and shape of the lever of the above embodiments. For example, the lever may be pole-shaped. 
     In the above embodiments, the displacement member was supported to allow rotation around the width direction, but it does not need to rotate. For example, the displacement member may be supported to allow movement in the direction of the intersection with the route surface of the discharge route. In this case, the displacement member moves, for example, in a vertical direction when it contacts the paper. The detector should then detect the movement of the displacement member. 
     One or more embodiments of the present invention may, for example, be applied to a laser printer and an inkjet printer that can perform double-sided printing. 
     DESCRIPTION OF SYMBOLS 
     
         
           100  Printer 
           101  Chassis 
           102  Discharge port 
           103  Catch tray 
           104  Paper cassette 
           110  Feed roller 
           111  Supply route 
           112  Discharge route 
           113  Reverse route 
           120  Print unit 
           121  Photoreceptor drum 
           122  Transcription roller 
           123  Fixing roller 
           130 ,  130 A,  130 B,  130 C Displacement member (or “detection member”) 
           131  Shaft 
           132 ,  132 A,  132 B,  132 C Lever 
           133 ,  133 C First lever 
           134 ,  134 C Second lever 
           135 ,  135 C Third lever 
           136  Slanted part (or “slant”) 
           141  Detector 
           142  Determining part 
           143  Controller