Patent Publication Number: US-2021188579-A1

Title: Medium conveying apparatus including pair of guides movably located according to conveyance of medium

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority of prior Japanese Patent Application No. 2019-229591, filed on Dec. 19, 2019, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     Embodiments discussed in the present specification relate to medium conveyance. 
     BACKGROUND 
     Recently, a medium conveying apparatus, such as a scanner, is required to convey media having various thicknesses, such as a thin paper, a plastic card or a passport. In such a medium conveying apparatus, a jam of a medium is likely to occur when a thin medium such as a thin paper is conveyed, whereas a slip between a conveyance roller and a medium is likely to occur when a thick medium such as a plastic card or a passport is conveyed. 
     A paper guide plate of an electrophotographic copying machine to feed various types of copying sheets to a nip of a pair of rollers that constitute a fixing device is disclosed (Japanese Unexamined Patent Publication (Kokai) No. 60-180247). A step portion having a width substantially equal to a width of a small-size thick paper is provided at a front end of the paper guide plate. 
     A medium conveyance path having a conveyance roller, a pressure roller facing the conveyance roller, and an upper guide plate and a lower guide plate to guide a conveyed medium is disclosed (Japanese Unexamined Patent Publication (Kokai) No. 2004-189371). In this medium conveyance path, a medium guide body having a slope to guide a front end of the medium towards a clamping portion of the conveyance roller and the pressure roller is provided on the upstream side of the pressure roller a the conveying direction, and at least a position of a downstream side of the medium guide body is changeable. 
     SUMMARY 
     According to some embodiments, a medium conveying apparatus includes a pair of conveyance rollers including a first roller and a second roller facing the first roller on an upward side of the first roller, to convey a medium between the first roller and the second roller, and a pair of guides including a lower guide located on an upstream side of the pair of conveyance rollers in a medium conveying direction and an upper guide facing the lower guide, to guide the medium to the pair of conveyance rollers. The upper guide is movably located upwardly according to a conveyance of the medium and the lower guide is movably located downwardly according to the conveyance of the medium so that a space between the pair of guides is changed according to the medium. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view illustrating a medium conveying apparatus  100  according to an embodiment. 
         FIG. 2  is a diagram for illustrating a conveyance path inside the medium conveying apparatus  100 . 
         FIG. 3A  is a schematic diagram for illustrating a first lower guide  121 , etc. 
         FIG. 3B  is a schematic diagram for illustrating the first lower guide  121 , etc. 
         FIG. 4  is a schematic diagram for illustrating a first moving portion  121   a.    
         FIG. 5A  is a schematic diagram for illustrating operations of the first moving portion  121   a , etc. 
         FIG. 5B  is a schematic diagram for illustrating operations of the first moving portion  121   a , etc. 
         FIG. 6A  is a schematic diagram for illustrating operations of the first moving portion  121   a , etc. 
         FIG. 6B  is a schematic diagram for illustrating operations of the first moving portion  121   a , etc. 
         FIG. 7A  is a schematic diagram for illustrating a relation between a conveying force and a conveying load of a medium. 
         FIG. 7B  is a graph  700  illustrating a relation between a force applied to a medium and an outer diameter of a roller. 
         FIG. 8  is a schematic diagram for illustrating other first lower guide  221 . 
         FIG. 9A  is a schematic diagram for illustrating other second conveyance roller  215 . 
         FIG. 9B  is a schematic view for diagram for illustrating other second conveyance roller  215 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory, and are not restrictive of the invention, as claimed. 
     Hereinafter, a medium conveying apparatus according to an embodiment, will be described with reference to the drawings. However, it should be noted that the technical scope of the invention is not limited to these embodiments, and extends to the inventions described in the claims and their equivalents. 
       FIG. 1  is a perspective view illustrating a medium conveying apparatus  100  configured as an image scanner. The medium conveying apparatus  100  conveys and images a medium being a document. The medium is a paper, such as thin paper, or a thick medium, such as a thick paper, a plastic card, a booklet or a passport (for example, a medium having a thickness larger than 2 mm). In other words, the medium supported by the medium conveying apparatus  100  includes a plurality of media each having a different thickness. The medium conveying apparatus  100  may be a fax machine, a copying machine, a multifunctional peripheral (MFP), etc. A conveyed medium may not be a document but may be an object being printed on etc., and the medium conveying apparatus  100  may be a printer etc. 
     The medium conveying apparatus  100  includes a lower housing  101 , an upper housing  102 , a medium tray  103 , and an ejection tray  104 , etc. 
     The upper housing  102  is located at a position covering the upper surface of the medium conveying apparatus  100  and is engaged with the lower housing  101  by hinges so as to be opened and closed at a time of medium jam, during cleaning the inside of the medium conveying apparatus  100 , etc. 
     The medium tray  103  is engaged with the lower housing  101  in such away as to be able to place a medium to be conveyed. The ejection tray  104  is engaged with the lower housing  101  in such a way as to be able to hold an ejected medium. 
       FIG. 2  is a diagram for illustrating a conveyance path inside the medium conveying apparatus  100 . 
     The conveyance path inside the medium conveying apparatus  100  includes a feed roller  111 , a brake roller  112 , a sensor  113 , a first conveyance roller  114 , a second conveyance roller  115 , a first imaging device  116   a , a second imaging device  116   b , a third conveyance roller  117  and a fourth conveyance roller  118 , etc. The numbers of each roller is not limited to one, and may be plural. An arrow A in  FIG. 2  indicates a medium conveying direction. An upstream hereinafter refers to an upstream in the medium conveying direction A 1 , and a downstream refers to a downstream in the medium conveying direction A 1 . 
     An upper surface of the lower housing  101  forms a first lower guide  121 , a second lower guide  122  and a third lower guide  123  to form a lower surface of the conveyance path of the medium. On the other hand, a lower surface of the upper housing  102  forms a first upper guide  124 , a second upper guide  125  and a third upper guide  126  to form an upper surface of the conveyance path of the medium. 
     The first lower guide  121  is an example of a lower guide, and is located on the upstream side of the first conveyance roller  114  and the second conveyance roller  115  in the medium conveying direction A 1 , to guide the medium to the first conveyance roller  114  and the second conveyance roller  115 . The second lower guide  122  includes an area corresponding to the first conveyance roller  114  and the second conveyance roller  115  in the medium conveying direction A 1 , and is located on the downstream side of the first lower guide  121  and on the upstream side of the first imaging device  116   a  and the second imaging device  116   b . The second lower guide  122  guides the medium to the first imaging device  116   a  and the second imaging device  116   b . The third lower guide  123  is located on the downstream side of the first imaging device  116   a  and the second imaging device  116   b , to guide the medium to the ejection tray  104 . The first lower guide  121 , the second lower guide  122  and the third lower guide  123  are formed of separate members. The first lower guide  121 , the second lower guide  122  and the third lower guide  123  may be formed of a single member. 
     The first upper guide  124  is an example of an upper guide, and is located at a position facing the first lower guide  121 , to guide the medium to the first conveyance roller  114  and the second conveyance roller  115 . The second upper guide  125  is located at a position facing the second lower guide  122 , to guide the medium to the first imaging device  116   a  and the second imaging device  116   b . The third upper guide  126  is located at a position facing the third lower guide  123 , to guide the medium to the ejection tray  104 . The first upper guide  124 , the second upper guide  125  and the third upper guide  126  are formed of separate members. The first upper guide  124 , the second upper guide  125  and the third upper guide  126  may be formed of a single member. 
     The feed roller  111  is provided on the lower housing  101  and sequentially feed media placed on the medium tray  103  from the lower side. The brake roller  112  is provided in the upper housing  102  and is located to face the feed roller  111 . 
     The sensor  113  is located downstream of the feed roller  111  and the brake roller  112  and upstream of the first conveyance roller  114  and the second conveyance roller  115  in the medium conveying direction A. The sensor  113  detects whether or not a medium exists at the position, and detects a medium passing through between the feed roller  111  and the brake roller  112 , and the first conveyance roller  114  and the second conveyance roller  115 . The sensor  113  includes a light emitter and a light receiver provided on one side with respect to the conveyance path of the medium, and a reflection member such as a mirror provided at a position facing the light emitter and the light receiver with the conveyance path in between. The light emitter emits light toward the conveyance path. On the other hand, the light receiver receives light projected by the light emitter and reflected by the reflection and outputs a medium signal being an electric signal based on intensity of the received light. Since the light emitted by the light emitter is shielded by the medium when the medium is present at the position of the sensor  113 , the signal value of the medium signal is changed in a state where the medium is present at the position of the sensor  113  and a state where the medium is not present. The light emitter and the light receiver may be provided at positions facing one another with the conveyance path in between, and the reflection member may be omitted. 
     The first conveyance roller  114  is an example of a first roller, and is provided on the lower housing  101 . The second conveyance roller  115  is an example of a second roller, is provided on the upper housing  102 , and is located to face the first conveyance roller  114  on an upward side of the first conveyance roller  114 . The first conveyance roller  114  and the second conveyance roller  115  are located on the downstream side of the medium conveying direction A 1  with respect to the feed roller  111  and the brake roller  112 . The first conveyance roller  114  and the second conveyance roller  115  are examples of a pair of conveyance rollers, and convey the medium fed by the feed roller  111  and the brake roller  112  to the downstream side between the first conveyance roller  114  and the second conveyance roller  115 . 
     The first imaging device  116   a  includes a line sensor based on a unity-magnification optical system type contact image sensor (CIS) including an imaging element based on a complementary metal oxide semiconductor (CMOS) linearly located in a main scanning direction. Further, the first imaging device  116   a  includes a lens for forming an image on the imaging element, and an A/D converter for amplifying and analog-digital (A/D) converting an electric signal output from the imaging element. The first imaging device  16   a  generates and outputs an input image imaging a front surface of a conveyed medium, in accordance with control from a processing circuit (not shown). 
     Similarly, the second imaging device  116   b  includes a line sensor based on a unity-magnification optical system type CIS including an imaging element based on a CMOS linearly located in a main scanning direction. Further, the secondary imaging device  16   b  includes a lens for forming an image on the imaging element, and an A/D converter for amplifying and A/D converting an electric signal output from the imaging element. The secondary imaging device  116   b  generates and outputs an input image imaging a back surface of a conveyed medium, in accordance with control from the processing circuit. 
     Only either of the first imaging device  116   a  and the second imaging device  116   b  may be located in the medium conveying apparatus  100  and only one side of a medium may be read. Further, a line sensor based on a unity-magnification optical system type CIS including an imaging element based on charge coupled devices (CCDs) may be used in place of the line sensor based on a unity-magnification optical system type CIS including an imaging element based on a CMOS. Further, a line sensor based on a reduction optical system type line sensor including an imaging element based on CMOS or CCDs. 
     The third conveyance roller  117  is provided on the lower housing  101 . The fourth conveyance roller  118  is provided on the upper housing  102 , and is located to face the third conveyance roller  117  on the upward side of the third conveyance roller  117 . The third conveyance roller  117  and the fourth conveyance roller  118  are located on the downstream side of the first conveyance roller  114  and the second conveyance roller  115  in the medium conveying direction A 1 . The third conveyance roller  117  and the fourth conveyance roller  118  further conveys the medium conveyed by the first conveyance roller  114  and the second conveyance roller  115  to the downstream side, between the third conveyance roller  117  and the fourth conveyance roller  118 . 
     A medium placed on the mounting table  103  is conveyed between the first lower guide  121  and the first upper guide  124  in the medium conveying direction A 1  by the feed roller  111  rotating in a direction of an arrow A 2  in  FIG. 2 , that is, the medium feeding direction. When the medium is conveyed, the brake rollers  112  rotate in a direction of an arrow A 3 , that is, a direction opposite to the medium feeding direction. By the workings of the feed roller  111  and the brake roller  112 , when a plurality of media are placed on the medium tray  103 , only a medium in contact with the feed roller  111 , out of the media placed on the medium tray  103 , is separated. Consequently, the medium conveying apparatus  100  operates in such a way that conveyance of a medium other than the separated medium is restricted (prevention of multi-feed). 
     The medium is fed between the first conveyance roller  114  and the second conveyance roller  115  while being guided by the first lower guide  121  and the second upper guide  124 . The medium is fed between the first imaging device  116   a  and the second imaging device  116   b  by the first conveyance roller  114  and the second conveyance roller  115  rotating in directions of an arrow A 4  and an arrow A 5 , respectively, while being guided by the second lower guide  122  and the second upper guide  125 . The medium is read by the first imaging device  116   a  and the second imaging device  116   b . Thereafter, the medium is ejected onto the ejection tray  104  by the third conveyance roller  117  and the fourth conveyance roller  118  rotating in directions of an arrow A 6  and an arrow A 7 , respectively, while being guided by the third lower guide  123  and the third upper guide  126 . 
       FIGS. 3A and 3B  are a schematic diagrams for illustrating the first lower guide  121  and the first upper guide  124 .  FIG. 3A  is a schematic diagram showing a state where the first lower guide  121  and the first upper guide  124  are located at a first position which is an initial position.  FIG. 3B  is a schematic diagram showing a state where the first lower guide  121  and the first upper guide  124  are located at a second position in which the first lower guide  121  is moved to the lowermost end side and the first upper guide  124  is moved to the uppermost end side. 
     As shown in  FIGS. 3A and 3B , a compression-coil spring  115   a  is provided between the upper housing  102  and a shaft which is a rotational axis of the second conveyance roller  115 . The second conveyance roller  115  is movably provided upwardly by the conveyed medium, and the compression coil spring  115   a  is provided to apply a force to the second conveyance roller  115  downwardly, that is, toward the first conveyance roller  114 . 
     The first lower guide  121  includes a first moving portion  121   a , a first supporting portion  121   b  and a recess  121   c . The first moving portion  121   a  is an example of a moving portion and is formed of a flexible member. The first supporting portion  121   b  is an example of a supporting portion, and supports the upstream end of the first moving portion  121   a  at the downstream end. The concave portion  121   c  is provided at a position facing the first moving portion  121   a  and on the lower side of the first moving portion  121   a . The first moving portion  121   a  is provided so as to be movable (swingable) downward (in a direction of an arrow A 8 ), by the first supporting portion  121   b  and the concave portion  121   c . The first moving portion  121   a  and the first supporting part  121   b  are formed of separate members. The first moving portion  121   a  and the first supporting part  121   b  may be formed of a single member. 
     The first upper guide  124  includes a second moving portion  124   a  and a second supporting portion  124   b . The second moving portion  124   a  has a protrusion  124   c  at the upstream end, and the second supporting part  124   b  has a recess at the downstream end. The front end of the protrusion  124   c  of the second moving portion  124   a  is engaged with the recess of the second supporting part  124   b  so that the second supporting part  124   b  rotatably (swingably) supports the second moving portion  124   a  at the downstream end. A torsion coil spring  124   d  is provided between the second moving portion  124   a  and the second supporting portion  124   b . The torsion coil spring  124   d  is provided around the protrusion  124   c  so that a force is applied to the second moving portion  124   a  downwardly (in a direction opposite to an arrow A 9 ). The second moving portion  124   a  is stopped by a stopper (not shown) so as not to move downward with respect to the first position shown in  FIG. 3A . The second moving portion  124   a  is provided so as to be movable (swingable) upward (in a direction of the arrow A 9 ) by the second supporting portion  124   b  and the torsion coil spring  124   d.    
     The second moving portion  124   a  and the second supporting part  124   b  are formed of separate members. The second moving portion  124   a  and the second supporting part  124   b  may be formed of a single member. Instead of the torsion coil spring  124   d , a compression coil spring, or a rubber member, etc., which presses the second moving portion  124   a  downward may be used. 
     As shown in the  FIG. 3A , in a height direction A 10  perpendicular to the first lower guide  121  and the first upper guide  124 , the first conveyance roller  114  is provided so as to project upward with respect to the first moving portion  121   a  located at the first position. Thus, the first lower guide  121  can convey the medium so as to reliably contact the first conveyance roller  114 , and the first conveyance roller  114  can suitably convey the medium. However, when a protruding amount Y 1  of the first conveyance roller  114  is too large, the front end of the medium may collide with the first conveyance roller  114  substantially at a right angle, and a jam of the medium may occur. Therefore, the protruding amount Y 1  of the first conveyance roller  114  is preferably as small as possible. 
     The protruding amount Y 1  of the first conveyance roller  114  is set, for example, in a range of 0.5 mm or more and 1.0 mm or less. The protrusion amount Y 1  is a distance in the height direction A 10  from the downstream end of the first moving portion  121   a  located at the first position to the upper end of the first conveyance roller  114 , i.e., a nip portion between the first conveyance roller  114  and the second conveyance roller  115 . 
     Similarly, in the height direction A 10 , the second conveyance roller  115  is provided so as to project downward with respect to the second moving portion  124   a  located at the first position. Thus, even when the medium is deflected and floated upward, the first upper guide  124  can reliably convey the medium to the nip portion of the first conveyance roller  114  and the second conveyance roller  115 , and the first conveyance roller  114  and the second conveyance roller  115  can suitably convey the medium. However, when a protruding amount X 1  of the second conveyance roller  115  is too large, the front end of the medium deflected to float upward may collide with the second conveyance roller  115  substantially at a right angle, and a jam of the medium may occur. Therefore, the protruding amount X 1  of the second conveyance roller  115  is preferably as small as possible. 
     The protruding amount X 1  of the second conveyance roller  115  is set, for example, in a range of 0.1 mm or more and 1.0 mm or less. The protrusion amount X 1  is a distance in the height direction A 10  from the downstream end of the second moving portion  124   a  located at the first position to the upper end of the first conveyance roller  114 . 
     On the other hand, as shown in  FIG. 3B , in the height direction A 10 , the first conveyance roller  114  is provided so as to project upward with respect to the first moving portion  121   a  located at the second position, so as to be larger than when the first moving portion  121   a  is located at the first position. When a thick medium such as a plastic card or a passport is conveyed and an area in which the medium is in contact with the first transport roller  114  is too small, a conveying force of the medium by the first transport roller  114  may be small, and the medium may slip to be not suitably conveyed. Therefore, the protrusion amount Y 2  of the first conveyance roller  114  with respect to the first moving portion  121   a  located at the second position is preferably large to some extent. However, when the protruding amount Y 2  of the first conveyance roller  114  is too large, the front end of the medium may collide with the first conveyance roller  114  substantially at a right angle, and a jam of the medium may occur. 
     The protruding amount Y 2  of the first conveyance roller  114  is set within a range of, for example, ⅓ or more of the maximum thickness of the medium supported by the medium conveying apparatus  100  and ½ or less of the roller diameter of the first conveyance roller  114 . The protrusion amount Y 2  is more preferably set to ½ or more of the maximum thickness of the medium supported by the medium conveying apparatus  100 . For example, when the maximum thickness of the medium supported by the medium conveying apparatus  100  is 7 mm and the roller diameter of the first conveyance roller  114  is 16 mm, the protruding amount Y 2  is set in the range of 2.3 mm or more and 8 mm or less (more preferably 3.5 mm). The protrusion amount Y 2  is a distance in the height direction A 10  from the downstream end of the first moving portion  121   a  located at the second position to the upper end of the first conveyance roller  114 . In other words, the protrusion amount Y 1  and the protrusion amount Y 2  are distances in the height direction A 10  from a position at which a lower end of the conveyed medium is in contact with the first conveyance roller  114  to the upper end of the first conveyance roller  114 . 
     Further, in the height direction A 10 , the second conveyance roller  115  is provided so as to project downward with respect to the second moving portion  124   a  located at the second position, so as to be larger than when the second moving portion  124   a  is located at the first position. When a thick medium, such as a plastic card or a passport, is conveyed and an area where the medium is in contact with the second conveyance roller  115  is too small, a conveying force of the medium by the second conveyance roller  115  may be small, and the medium may slip to be not suitably conveyed. Therefore, the protrusion amount X 2  of the second conveyance roller  115  with respect to the second moving portion  124   a  located at the second position is preferably large to some extent. However, when the protruding amount X 2  of the second conveyance roller  115  is too large, the front end of the medium may collide with the second conveyance roller  115  substantially at a right angle, a jam of the medium may occur. 
     The protruding amount X 2  of the second conveyance roller  115  is set within a range of, for example, the maximum thickness of the medium supported by the medium conveying apparatus  100  or more and 3/2 of the maximum thickness or less. Further, the protruding amount X 2  is preferably set to ⅔ or less of the roller diameter of the second conveyance roller  115 . For example, when the maximum thickness of the medium supported by the medium conveying apparatus  100  is 7 mm, the protrusion amount X 2  is set in the range of 7 mm or more and 10.5 mm or less (e.g., 10 mm). The protrusion amount X 2  is a distance in the height direction A 10  from the downstream end of the second moving portion  124   a  located at the second position to the upper end of the first conveyance roller  114 . In other words, the protrusion amount X 1  and the protrusion amount X 2  are distances in the height direction A 10  from a position where the upper end of the medium guided by the first upper guide  124  is in contact with the second conveyance roller  115  to the upper end of the first conveyance roller  114 . 
     The distance H in the height direction A 10  between the first moving portion  121   a  and the second moving portion  124   a  located at the second position is a sum of the protrusion amount Y 2  and the protrusion amount X 2 , and is set within a range of 9.3 mm or more and 22 mm or less (more preferably 13.5 mm). 
     As described above, in the medium conveying apparatus  100 , the first upper guide  124  (the second moving portion  124   a ) is movably located upwardly according to a conveyance of the medium and the first lower guide  121  (the first moving portion  121   a ) is movably located downwardly according to the conveyance of the medium. Thus, a space between the first upper guide  124  and the first lower guide  121  can be changed according to the medium. Further, the space between the first upper guide  124  and the first lower guide  121  is changed so that the distance from the position at which the lower end of the medium is in contact with the first conveyance roller  114  to the upper end of the first conveyance roller  114  (the protrusion amount Y 1  and the protrusion amount Y 2 ) is changed. 
       FIG. 4  is a schematic diagram for illustrating the first moving portion  121   a .  FIG. 4  is a schematic diagram of the lower housing  101  in a state of removing the upper housing  102  viewed from above. 
     As shown in  FIG. 4 , the first lower guide  121  is located on the upstream side of the first conveyance roller  114  and the second conveyance roller  115  in the medium conveying direction A 1 . The first support portion  121   b  is formed on the downstream side of the feed roller  111  and the brake roller  112  in the medium conveying direction A 1 . The first moving section  121   a  is located between the first supporting section  121   b , and the first conveyance roller  114  and the second conveyance roller  115  in the medium conveying direction A 1 . 
     The first lower guide  121  is formed over both ends of the medium conveyance path in the width direction A 11  perpendicular to the medium conveying direction. The first moving portion  121   a  is located at a substantially central portion of the medium conveyance path in the width direction A 11 . Generally, a size in the width direction A 11  of the thick medium, such as a plastic card or a passport, conveyed by the medium conveying apparatus is small compared to a size in the width direction A 11  of a commonly used paper, such as A4 paper. Since the first moving portion  121   a  is located only at the center of the medium conveyance path, rather than over both ends, the first moving portion  121   a  moves when the thick medium is conveyed, the first moving portion  121   a  does not move when of the commonly used paper is conveyed. Thus, the medium conveying apparatus  100  can suppress an occurrence of a jam of the medium when the commonly used paper is conveyed. 
     In the first moving portion  121   a , two slits  121   d  are formed at a predetermined distance from both ends in the width direction A 11 , respectively. As a result, the first moving section  121   a  is more flexible when the thick medium passes through, so that the first moving section  121   a  can suitably convey the thick medium. In particular, the first moving portion  121   a  is more flexible when the medium passes between the two slits  121   d . Therefore, a distance between the two slits  121   d  is preferably set to a length acquired by adding a margin to a length of a plastic card or a passport in the width direction A 11 . 
     In the example shown in  FIG. 4 , a number of the sensors  113  is three. The medium conveying apparatus  100  determines whether or not a jam of the medium has occurred according to a timing at which the medium has passed through the sensor  113 . Further, the medium conveying apparatus  100  determines whether or not the skew of the medium has occurred by comparing the respective timings at which the medium has passed through the three sensors  113 . The first moving portion  121   a  is provided with an opening at a position facing the light emitter  113   a  and the light receiver  113   b  of each of the sensors  113 . Thus, the sensors  113  can suitably detect the medium. 
       FIGS. 5A, 5B, 6A and 6B  are schematic diagrams for illustrating operations of the first moving portion  121   a  and the second moving portion  124   a  when the medium is conveyed.  FIG. 5A  is a diagram showing the first moving portion  121   a  and the second moving portion  124   a  when a paper P is conveyed as the medium.  FIG. 5B  is a diagram showing the first moving portion  121   a  and the second moving portion  124   a  when the paper P is conveyed as the medium and the paper P is bent upward to float up.  FIG. 6A  is a diagram showing the first moving portion  121   a  and the second moving portion  124   a  when a plastic card C is conveyed as the medium.  FIG. 6B  is a diagram showing the first moving portion  121   a  and the second moving portion  124   a  when the plastic card C is conveyed as the medium and the card C is conveyed to the nip portion of the feed roller  111  and the braking roller  112 . 
     As shown in  FIG. 5A , when the paper P is conveyed as the medium, the first moving portion  121   a  and the second moving portion  124   a  do not move from the first position. Thus, the first moving portion  121   a  guides the medium to the nip portion between the first conveyance roller  114  and the second conveyance roller  115  by contacting the medium with the first conveyance roller  114 . Since the protruding amount Y 1  of the first conveyance roller  114  is sufficiently small, it is unlikely that the conveyed medium collides with the first conveyance roller  114  substantially at a right angle and a jam occurs. 
     As shown in  FIG. 5B , when the paper P is conveyed as the medium and the sheet P is bent upward to float up, the first moving portion  121   a  and the second moving portion  124   a  do not move from the first position. Thus, the second moving portion  124   a  contacts the medium floated upward with the second conveyance roller  115  or the first conveyance roller  114 , and guides the medium to the nip portion of the first conveyance roller  114  and the second conveyance roller  115 . Since the protruding amount X 1  of the second conveyance roller  115  is sufficiently small, it is unlikely that the conveyed medium collides with the second conveyance roller  115  substantially at a right angle and a jam occurs. 
     As shown in  FIG. 6A , when the card C is conveyed as the medium, the first moving portion  121   a  moves downward from the first position by a weight of the card C. Thus, the first moving portion  121   a  guides the medium to the first conveyance roller  114  so that the area in which the medium is contact with the first conveyance roller  114  is sufficiently large. Thus, a frictional force between the first conveyance roller  114  and the medium increases, and the first conveyance roller  114  can convey the medium with a sufficient conveying force. Further, since the first moving portion  121   a  moves downward, the card C is into contact with the second conveyance roller  115  from the lower side. Thus, the second conveyance roller  115  is suitably pushed up by the card C. 
     As shown in  FIG. 6B , when the upper portion of the card C conveyed by the first conveyance roller  114  contacts the second moving portion  124   a , the second moving portion  124   a  is pushed up by a thickness of the card C and moves upward from the first position. Thus, the second moving portion  124   a  guides the medium to the second conveyance roller  115  so that an area in which the medium is in contact with the second conveyance roller  115  is sufficiently large. Further, since the second moving portion  124   a  moves upward, the card C is sandwiched by the first moving portion  121   a  and the second moving portion  124   a  so as to be pressed, thereby, it is suppressed that the frictional force between the card C and the second moving portion  124   a  becomes too large. Thus, the frictional force between the second conveyance roller  115  and the medium increases and the frictional force between the medium and the second moving section  124   a  decreases, so that the medium is suitably conveyed. 
       FIG. 7A  is a schematic diagram for illustrating a relation between a conveying force and a conveying load of the medium. 
     As shown in  FIG. 7A , a first conveying force F 1  corresponding to a frictional force between the feed roller  111  and the brake roller  112 , and the medium M, and a pressing force by the compression coil spring  112   a  to press the brake roller  112  to the feed roller  111  side is applied to the medium M, to the medium conveying direction A 1 . Further, a second conveying force F 2  corresponding to a frictional force between the first conveyance roller  114  and the second conveyance roller  115 , and the medium M, and a pressing force by the compression coil spring  115   a  to press the second conveyance roller  115  to the first conveyance roller  114  side is applied to the medium M, to the medium conveying direction A 1 . 
     On the other hand, a first load L corresponding to a force for separating the medium by the brake roller  112  rotating in an opposite direction A 3  of the medium feeding direction is applied to the medium M to the opposite direction of the medium conveying direction A 1 . Further, a second load L 2  corresponding to a frictional force generated by the first lower guide  121  and the first upper guide  124  being in contact with the medium M is applied to the medium M, to the opposite direction of the medium conveying direction A 1 . Further, a third load L 3  received when pushing up the second conveyance roller  115  upward is applied to the medium M, to the opposite direction of the medium conveying direction A. 
     When a sum of the first conveying force F 1  and the second conveying force F 2  is larger than a sum of the first load L 1 , the second load L 2  and the third load L 3 , the medium is conveyed to the medium conveying direction A 1 . However, when the second conveying force F 2  is sufficiently small with respect to the first conveying force F 1 , or when the second load L 2  and/or the third load L 3  are sufficiently large with respect to the first conveying force F 1 , the medium M may buckle and a jam of the medium may occur. 
     As described above, the first moving portion  121   a  moves downward by the weight of the medium M, and the second moving portion  124   a  moves upward by the thickness of the medium M. Therefore, when the medium having a predetermined weight and thickness is conveyed, the area in which the medium M is into contact with the first conveyance roller  114  and the second conveyance roller  115  increases, and the second conveying force F 2  corresponding to the frictional force between the first conveyance roller  114  and the second conveyance roller  115  and the medium M increases. 
     In this case, the force of pressing the medium M by the first moving portion  121   a  and the second moving portion  124   a  is small, and the second load L 2  corresponding to the frictional force generated by the first lower guide  121  and the first upper guide  124  being into contact with the medium M is small. 
     Further, the medium M is in contact with the second conveyance roller  115  from side to push up the second conveyance roller  115 . As the position at which the medium M is in contact with the second conveyance roller  115  is lower, the medium M can push up the second conveyance roller  115  with a small force. The medium M can push up the second conveyance roller  115  from below by the first moving portion  121   a  moving downward by the weight of the medium M, and the third load L 3  received when the second conveyance roller  115  is pushed up becomes small. 
     Therefore, the medium conveying apparatus  100  can suitably convey the thick medium by the first moving portion  121   a  and the second moving portion  124   a  movably provided with the thick medium. 
       FIG. 7B  is a graph  700  illustrating a relation between a force applied to a medium by a roller and an outer diameter of the roller. 
     The horizontal axis of the graph  700  of  FIG. 7B  indicates a magnitude of the outer diameter of the roller, and the vertical axis indicates a ratio of a sum of the first conveying force F 1  and the second conveying force F 2  to a sum of the first load L 1 , the second load L 2  and the third load L 3 . The graph  701  shows a ratio when rotating both the first conveyance roller  114  and the second conveyance roller  115 , and the graph  702  shows a ratio when rotating only one of the first conveyance roller  114  and the second conveyance roller  115 . In the graph  700 , the medium is stably conveyed when the ratio is equal to or larger than a threshold T. On the other hand, the medium may not be stably conveyed when the ratio is less than the threshold T. Therefore, when rotating both the first conveyance roller  114  and the second conveyance roller  115 , the outer diameter of each conveyance roller is required to be D 1  or more. Further, when rotating only one of the first conveyance roller  114  and the second conveyance roller  115 , the outer diameter of each conveyance roller is required to be D 2  or more. 
     In other words, by increasing the outer diameter of the first conveyance roller  114  and the second conveyance roller  115 , the ratio of the conveying force to the load increases so that the medium is suitably conveyed. However, when increasing the outer diameter of the first conveyance roller  114  and the second conveyance roller  115 , the size and weight of the medium conveying apparatus  100  increases. The medium conveying apparatus  100  can suitably convey the medium without increasing the size and weight of the medium conveying apparatus  100  by the first moving portion  121   a  and the second moving portion  124   a  movably provided with a thick medium. 
     The ratio of the conveying force to the load by the roller is changed by not only the outer diameter of the roller, but also by a material of the roller (rubber hardness, frictional force between the roller and the medium, etc.). However, limiting the material of the roller may increase the device cost of the medium conveying apparatus  100 . The medium conveying apparatus  100  can suitably convey the medium even when the material of the roller is not optimal, by the first moving portion  121   a  and the second moving portion  124   a  movably provided by the thick medium. 
     As described in detail above, the medium conveying apparatus  100  controls the protruding amount of the conveyance roller by moving a pair of guides provided above and below the conveyance path in the vertical direction. Thus, the medium conveying apparatus  100  suitably guides the medium so as to acquire a sufficient conveying force when the thick medium is conveyed, and so as not to cause a jam when the thin paper is conveyed. Therefore, the medium conveying apparatus  100  can suitably convey a plurality of media having different thicknesses, respectively. 
     Further, when conveying the medium having a thickness, the user does not need to convey the medium stored in a special sheet, etc. Therefore, the medium conveying apparatus  100  can improve the convenience of the user. 
       FIG. 8  is a schematic diagram for illustrating a first lower guide  221  in a medium conveying apparatus according to another embodiment. 
     As shown in  FIG. 8 , the medium conveying apparatus according to the present embodiment, includes a first lower guide  221 , instead of the first lower guide  121 . The first lower guide  221  is an example of a lower guide, and includes a first moving portion  221   a , a first supporting portion  221   b  and a recess  221   c . The first moving portion  221   a  is an example of a moving portion, and is formed of a resin member or a metal member, and includes a protrusion  221   d  at the upstream end. The first support portion  221   b  is an example of a support portion, and includes a recess at the end of the downstream side. A tip of the protrusion  221   d  of the first moving portion  221   a  is engaged with the recess of the first supporting portion  221   b , so that the first supporting portion  221   b  rotatably (swingably) supports the first moving portion  221   a  at the downstream end. 
     A torsion coil spring  221   e  is provided between the first moving portion  221   a  and the first supporting portion  221   b . The torsion coil spring  221   e  is provided around the protrusion  221   d  so that a force is applied to the first moving portion  221   a  upwardly (in a direction opposite to the arrow A 8 ). The torsion coil spring  221   e  is an example of a pressing member, and presses the first lower guide  221  upward. The first moving portion  221   a  is stopped by a stopper (not shown) so as not to move upward from a first position shown in  FIG. 8 . The concave portion  221   c  is provided at a position facing the first moving portion  221   a  and below the first moving portion  221   a . The first moving portion  221   a  is movably (swingably) located downwardly (in the direction of the arrow A 8 ) by the first supporting portion  221   b , the recess  221   c  and the torsion coil spring  221   e.    
     As described in detail above, the medium conveying apparatus can suitably convey a plurality of media having different thicknesses, even when the first moving portion  221   a  is movably provided using the pressing member. 
     Instead of the torsion coil spring  221   e , a compression coil spring or a rubber member, etc., may be used as the pressing member. In this case, the compression coil spring or the rubber member is provided between the first moving portion  221   a  and the concave portion  221   c  so as to press the first moving portion  221   a  upward. Further, the pressing member is omitted, the first moving portion itself may be formed of an elastic member such as rubber. 
       FIGS. 9A and 9B  are schematic diagrams for illustrating the second conveyance roller  215  in a medium conveying apparatus according to still another embodiment. 
     As shown in  FIGS. 9A and 9B , the medium conveying apparatus according to the present embodiment has a second conveyance roller  215 , instead of the second conveyance roller  115 . The second conveyance roller  215  is located on the downstream side of the first conveyance roller  114  in the medium conveying direction A 1 , i.e., on the side of the first imaging device  116   a  and the second imaging device  116   b.    
     The protrusion amount Y 1 , the protrusion amount Y 2  and the protrusion amount X 1  of the medium conveying apparatus of the present embodiment are respectively set within the same ranges as the protrusion amount Y 1 , the protrusion amount Y 2  and the protrusion amount X 1  of the medium conveying apparatus  100 . The protrusion amount X 1  of the medium conveying apparatus of the present embodiment is, similarly to the protrusion amount X 1  of the medium conveying apparatus  100 , the distance in the height direction A 10  from the downstream end of the second moving portion  124   a  located at the first position to the upper end of the first conveyance roller  114 . 
     On the other hand, the protruding amount X 2 ′ of the medium conveying apparatus of the present embodiment is set to a value smaller than the protruding amount X 2  of the medium conveying apparatus  100 . The protrusion amount X 2 ′ of the medium conveying apparatus of the present embodiment is, similarly to the protrusion amount X 2  of the medium conveying apparatus  100 , the distance in the height direction A 10  from the downstream end of the second moving portion  124   a  located at the second position to the upper end of the first conveyance roller  114 . For example, when the second conveyance roller  215  is located to be shifted by 1 mm with respect to the first conveyance roller  114 , the protruding amount X 2 ′ is set within a range of ⅔ or more and 4/3 or less of the maximum thickness of the medium supported by the medium conveying apparatus. Further, the protruding amount X 2 ′ is preferably set to ⅔ or less of the roller diameter of the second conveyance roller  215 . For example, when the maximum thickness of the medium supported by the medium conveying apparatus  100  is 7 mm, the protrusion amount X 2 ′ is set in a range of 4.7 mm or more and 9.3 mm or less (e.g., 7 mm). 
     The distance H′ in the height direction A 10  between the first moving portion  121   a  and the second moving portion  124   a  located at the second position is a sum of the protrusion amount Y 2  and the protrusion amount X 2 ′, and is set within a range of 7.0 mm or more and 17.3 mm or less (more preferably, 10.5 mm). 
     When the second conveyance roller  215  is located to be shifted to the downstream side of the first conveyance roller  114  in the medium conveying direction A 1 , the medium is conveyed so as to ride on the first conveyance roller  114 , so that the area in which the medium is in contact with the first conveyance roller  114  increases. Therefore, the frictional force between the first conveyance roller  114  and the medium increases, so that the first conveyance roller  114  can convey the medium with a sufficient conveying force. Therefore, even when the protrusion amount X 2 ′ and the distance H′ is smaller than the protrusion amount X 2  and the distance H, the medium conveying apparatus can suitably convey the medium. 
     As described in detail above, the medium conveying apparatus can suitably convey a plurality of media having different thicknesses, respectively, even when the second conveyance roller  215  is located to be shifted to the downstream side of the first conveyance roller  114  in the medium conveying direction A 1 . 
     According to the embodiment, the medium conveying apparatus can suitably convey a plurality of media having different thicknesses, respectively. 
     All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiment(s) of the present inventions have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.