Abstract:
An image forming device includes a sheet conveyor, an image former that forms an image on a surface of a sheet conveyed by the sheet conveyor, and a re-conveyor that re-conveys the sheet to the image former which forms another image on an opposite surface of the sheet. The re-conveyor includes a guide member including upper and lower conveyance members, a regulation member that regulates a position of the sheet, a conveyer roller set that conveys the sheet therebetween, an urger that urges a pinch roller toward a driving roller, and a roller holder disposed above the upper conveyance member. The upper conveyance member has ends which are secured independently to the lower conveyance member. The roller holder secures the pinch roller overlaps the upper conveyance member in a vertical direction, and secures the pinch roller, such that the pinch roller contacts the sheet through the upper conveyance member.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to Japanese Patent Application No. 2010-243880, filed on Oct. 29, 2010, which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to an image forming device that performs single-sided and double-sided printing. 
         [0004]    2. Description of the Related Art 
         [0005]    A known image forming device includes a re-conveying unit for returning an inverted paper sheet with an image formed on a first surface thereof to an image forming unit. A known image forming device, e.g., the image forming device described in Japanese Unexamined Patent Application Publication No. 2002-104694, includes conveyor rollers for conveying the paper sheet obliquely toward a one-side regulation member provided at one width direction end of the paper sheet. In a known image forming device, conveyor rollers may have a rubber-made driving roller and a resin-made pinch roller which follows the driving roller. The pinch roller is disposed obliquely to the driving roller so as to obliquely convey the paper sheet. The pinch roller is disposed in contact with the first surface on which an image has been formed. 
         [0006]    In a known image forming device, however, if a resin-made pinch roller is disposed in contact with the printing surface of the paper sheet as described above, the pinch roller slips against the printing surface and, as a result, the oblique feeding capability may decrease. This problem is more likely to occur when glossy paper is used or when color printing is performed in which multiple colors are superimposed on top of one another. 
       SUMMARY OF THE INVENTION 
       [0007]    Therefore, a need has arisen for systems and methods for an image forming apparatus, and it is an object of the invention to overcome these and other deficiencies of the related art. Specifically, in an embodiment of the invention, the oblique feeding capability of conveyor rollers in a re-conveying unit may be increased and improved. In an embodiment of the invention, the second pinch roller may have a greater coefficient of friction, e.g., with respect to the recording sheet, than the first pinch roller. Thus, the recording sheet may be conveyed obliquely by the second pinch roller with a high coefficient of friction until the recording sheet comes into contact with the one-side regulation member even if the first pinch roller slips on a first surface on which an image has been formed. In an embodiment of the invention, the oblique feeding capability of the conveyor rollers of the re-conveying unit may be improved. 
         [0008]    In an embodiment of the invention, an image forming device comprising: a sheet conveying unit configured to convey a plurality of sheets; an image forming unit configured to form an image on a first surface of a sheet that is conveyed from the plurality of sheets by the sheet conveying unit; and a re-conveying unit configured to re-convey the sheet along a re-conveying path to the image forming unit such that the image forming unit is configured to form another image on a second surface of the sheet opposite the first surface. The re-conveying unit comprises: a guide member; a single side regulation member extending in a particular direction and configured to contact a particular end of the sheet to regulate a position of the sheet; a conveyer roller set configured to convey the sheet therebetween; an urging member configured to urge the pinch roller toward the driving roller; and a roller holder disposed above the upper conveyance member. The guide member comprises: a lower conveyance member disposed below the re-conveying path; and an upper conveyance member secured to the lower conveyance member and disposed above the re-conveying path. The conveyor roller set comprises: a driving roller configured to receive a driving force; and a pinch roller configured to contact the first surface of the sheet. The upper conveyance member has a first end and a second end opposite to the first end in a direction perpendicular to the particular direction, and the first end and the second end of the upper conveyance member are independently secured to the lower conveyance member. The roller holder is configured to secure the pinch roller to the upper conveyance member, disposed to overlap the upper conveyance member in a vertical direction, and configured to secure the pinch roller such that the pinch roller is configured to contact the sheet through an opening formed in the upper conveyance member. 
         [0009]    In another embodiment of the invention, an image forming device comprises: a sheet container unit configured to store a plurality of sheets therein and configured to slide in a particular direction; an image forming unit configured to form an image on a first surface of a sheet that is conveyed from the plurality of sheets in the sheet container unit; and a re-conveying unit configured to re-convey the sheet along a re-conveying path to the image forming unit such that the image forming unit is configured to form another image on a second surface of the sheet opposite the first surface. The re-conveying unit comprises: a guide member; a single side regulation member extending in a particular direction and configured to contact a particular end of the sheet to regulate a position of the sheet; a conveyer roller set configured to convey the sheet therebetween; an urging member configured to urge the pinch roller toward the driving roller; and a roller holder disposed to overlap the upper conveyance member in a vertical direction. The guide member comprises: a lower conveyance member disposed below the re-conveying path; and an upper conveyance member secured to the lower conveyance member and disposed above the re-conveying path. The conveyor roller set comprises: a driving roller configured to receive a driving force; and a pinch roller configured to contact the first surface of the sheet. The upper conveyance member has a first end and a second end opposite to the first end in a direction perpendicular to the particular direction, and the first end and the second end are independently secured to the lower conveyance member. The roller holder is configured to secure the pinch roller such that the pinch roller is configured to rotate in a hole formed in the upper conveyance member. 
         [0010]    In yet another embodiment of the invention, an image forming device comprises: a sheet container unit configured to store a plurality of sheets therein and configured to slide in a particular direction; an image forming unit configured to form an image on a first surface of a sheet that is conveyed from the plurality of sheets in the sheet container unit; and a re-conveying unit configured to re-convey the sheet along a re-conveying path to the image forming unit such that the image forming unit is configured to form another image on a second surface of the sheet opposite the first surface. The re-conveying unit comprises: a guide member; a single side regulation member extending in a particular direction and configured to contact a particular end of the sheet to regulate a position of the sheet; a conveyer roller set configured to convey the sheet therebetween; an urging member configured to urge the pinch roller toward the driving roller; and a roller holder disposed above the upper conveyance member. The guide member comprises a lower conveyance member disposed below the re-conveying path; and an upper conveyance member secured to the lower conveyance member and disposed above the re-conveying path. The conveyor roller set comprises: a driving roller configured to receive a driving force; and a pinch roller configured to contact the first surface of the sheet. The upper conveyance member has a first end and a second end opposite to the first end in a direction perpendicular to the particular direction, and the first end and the second end are independently secured to the lower conveyance member. The roller holder is configured to secure the pinch roller such that a central axis of the pinch roller is not aligned with the upper conveyance member in the vertical direction. 
         [0011]    Other objects, features, and advantages will be apparent to persons of ordinary skill in the art from the following detailed description of the invention and the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    For a more complete understanding of the present invention, needs satisfied thereby, and the objects, features, and advantages thereof, reference now is made to the following descriptions taken in connection with the accompanying drawings. 
           [0013]      FIG. 1  depicts a side cut-away view of an image forming device, e.g., a color printer, according to an embodiment of the invention. 
           [0014]      FIG. 2  is a perspective view of a re-conveying unit, according to an embodiment of the invention. 
           [0015]      FIG. 3  is an exploded, perspective view of a re-conveying unit, according to an embodiment of the invention. 
           [0016]      FIG. 4  is a top view of the re-conveying unit, according to an embodiment of the invention. 
           [0017]      FIG. 5  is a bottom, perspective view of a paper feed tray, according to an embodiment of the invention. 
           [0018]      FIG. 6  is a top view of the paper feed tray, according to an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0019]    Embodiments of the invention and their features and technical advantages may be understood by referring to  FIGS. 1-6 , like numerals being used for like corresponding portions in the various drawings. 
         [0020]    Hereinafter, an embodiment of the present invention is described in detail with reference to  FIG. 1  which depicts a structure of an image forming device, e.g., color printer  1 , according to an embodiment of the invention. Color printer  1  may comprise a re-conveying unit  100 , which will be described in more detail herein with respect to  FIGS. 2-4 . In the following descriptions, directions may be defined with reference to a user who is using the color printer  1 . Specifically, when oriented as depicted in  FIG. 1 , the left side of the page may be a “front side,” hereinafter interchangeably referred to as a “near side,” e.g., “nearer” to the user than the opposite side. The right side of the page may be a “rear side,” hereinafter interchangeably referred to as a “back side.” Similarly, the back side of the page, e.g., the unseen side, may be a “left side,” and the near, visible side of the page may be a “right side,” of the color printer  1 . The vertical direction of the page of  FIG. 1  may be referred to as a “vertical direction” with reference to the color printer  1 . 
         [0021]    As depicted in  FIG. 1 , the color printer  1  may be an apparatus that forms images on both surfaces of a recording sheet, e.g., a paper sheet S. The color printer  1  may comprise a paper feeding unit  3 , an image forming unit  4 , and a conveying unit  5 , which may be disposed in an apparatus main body  2 . The paper feeding unit  3 , which may be disposed at a lower portion of the apparatus main body  2 , may comprise a paper feed tray  31 , e.g., a sheet container unit configured to accommodate, e.g., to store, a plurality of sheets, including a paper sheet S, and a paper feeding mechanism  32 . The paper feeding mechanism  32  may feed the paper sheet S from the paper feed tray  31  to the image forming unit  4 . The paper feed tray  31  may be removed from the apparatus main body  2  by exerting a force pulling the paper feed tray  31  away from the apparatus main body  2 , and the paper feed tray  31  may be replaced into the apparatus main body by exerting a force pushing the paper feed tray  31  into the apparatus main body  31 . 
         [0022]    The image forming unit  4  for forming an image on the paper sheet S conveyed from the plurality of sheets in the paper feeding unit  3  may comprise an exposure unit  41 , four process units  42 , a transfer unit  43  and a fixing unit  44 . The exposure unit  41  may be disposed at an upper portion of the apparatus main body  2 . The exposure unit  41  may comprise a laser light source (not depicted), a polygon mirror, a plurality of lenses and a plurality of reflectors. With reference to  FIG. 1 , the polygon mirror, plurality of lenses, and plurality of reflectors are not assigned reference numerals. The laser light source may emit laser light that corresponds to image data. The emitted laser light may be reflected by the polygon mirrors and the reflectors, such that the laser light may pass through the lenses and then rapidly scan a surface of each of photosensitive drums  42 A. 
         [0023]    The process units  42  may be disposed serially in a direction from the front side of the color printer  1  to the rear side of the color printer  1 , hereinafter interchangeably referred to as a front-to-rear direction, and disposed between the paper feed tray  31  and the exposure unit  41 . Each process unit  42  may comprise a photosensitive drum  42 A, a charging unit  42 B, a developing roller, a supply roller, a layer-thickness regulating blade and a toner container unit which accommodates toner, e.g., a developing agent. With reference to  FIG. 1 , the developing roller, supply roller, layer-thickness regulating blade, and toner container unit are not assigned reference numerals. Each process unit  42  may be substantially the same in structure, except that, in an embodiment of the invention, each process unit  42  may accommodate a different color of toner in the toner container unit. 
         [0024]    The transfer unit  43  may be disposed between the paper feed tray  31  and the process units  42 . The transfer unit  43  may comprise an endless conveyor belt  43 A stretched between a driving roller and a driven roller, which are not assigned reference numerals in  FIG. 1 , and four transfer rollers  43 B. An outer surface of the conveyor belt  43 A may be in contact with the photosensitive drums  42 A. The conveyor belt  43 A may be held between each of the transfer rollers  43 B, which may be disposed inside the conveyor belt  43 A, and each of the photosensitive drums  42 A. 
         [0025]    The fixing unit  44  may be disposed behind the process units  42 . The fixing unit  44  may comprise a heat roller  44 A and a pressure roller  44 B disposed opposite to the heat roller  44 A to press the heat roller  44 A. In the image forming unit  4 , the charging unit  42 B may uniformly charge the surface of each of the photosensitive drums  42 A. Then, the exposure unit  41  may emit laser light that exposes each of the photosensitive drums  42 A to the emitted laser light. As a result, an electrostatic latent image corresponding to the image data may be formed on each of the photosensitive drums  42 A. A supply roller may supply the toner in the toner container unit to the developing roller. The supplied toner in the developing roller may enter between the developing roller and the layer-thickness regulating blade, and may form a thin toner layer of fixed thickness that is supported on the developing roller. 
         [0026]    The toner supported on the developing roller then may be supplied to each of the photosensitive drums  42 A on which the electrostatic latent image is formed. Then, the electrostatic latent image may be visualized and a toner image may be formed on each of the photosensitive drums  42 A. Then, the paper sheet S may be fed from the paper feeding unit  3  and may be conveyed between the photosensitive drums  42 A and the conveyor belt  43 A. After that, the toner images formed on the photosensitive drums  42 A may be sequentially transferred to the paper sheet S to be superimposed on top of one another. 
         [0027]    The paper sheet S on which the toner images have been transferred then may be conveyed between the heat roller  44 A and the pressure roller  44 B for the heat-fusing of the toner images. In this manner, an image may be formed on a first surface, e.g., a first side, of the paper sheet S. The paper sheet S on which the image has been formed may be output to a conveying path  51  from the fixing unit  44  by an output roller  45 . 
         [0028]    The conveying unit  5  may function as an output mechanism for outputting the paper sheet S from the image forming unit  4  to the outside of the apparatus main body  2  and, at the same time, may function as a re-conveying unit for re-conveying, to the image forming unit  4 , the inverted paper sheet S with the image formed on the first surface thereof by the image forming unit  4 . Specifically, the conveying unit  5  may comprise a conveying path  51 , an output roller  52 , a flapper  53  which may swing in the front-to-rear direction, a re-conveying path  54  and a plurality of conveyor rollers  55  that may convey the paper sheet S in the re-conveying path  54 . 
         [0029]    The conveying path  51  may be at the rear portion of the apparatus main body  2 . The conveying path  51  may extend upward from a portion near the front side of a backwardly swung flapper  53 , e.g., as depicted by the solid line in  FIG. 1 , and then may extend and curve to the front. 
         [0030]    The output roller  52  may selectively rotate in both a forward and a reverse direction. When the output roller  52  is rotating in a forward direction, the paper sheet S may be outputted from the image forming unit  4  to the outside of the apparatus main body  2 . When the output roller  52  is rotated in the reverse direction, the paper sheet S may be conveyed into the apparatus main body  2 . 
         [0031]    The re-conveying path  54  may extend from the rear portion of the apparatus main body  2  to the lower portion of the apparatus main body  2 , as depicted in  FIG. 1 . The re-conveying path  54  may extend downward from a portion near the rear side of the forwardly swung flapper  53 , e.g. as depicted by the dashed line in  FIG. 1 , and then may extend to the front below the paper feed tray  31  to curve to the front. The re-conveying path  54  then may extend to curve upward toward the paper feeding mechanism  32 . Re-conveying unit  100 , which will be described in more detail herein, may form at least a portion of the re-conveying path  54 . 
         [0032]    Upon completion of the image formation, the paper sheet S outputted from the image forming unit  4  may be conveyed along the conveying path  51 . Then, the paper sheet S may be outputted to the outside of the apparatus main body  2  by the forwardly rotating output roller  52 , and may be placed on the output tray  22 . If an image is to be formed on a second surface of the paper sheet S opposite to the first surface on which an image already has been formed, then the paper sheet may be is drawn into the apparatus main body  2 , conveyed along the conveying path  51 , and then conveyed along the re-conveying path  54 . The previous conveying may be performed by the output roller  52 , which may rotate in the reverse direction before the entire paper sheet S is completely outputted from the apparatus main body  2 . Then, the paper sheet S, as depicted by the dashed line in  FIG. 1 , may be conveyed on the re-conveying path  54  by the conveyor rollers  55 , and then again may be conveyed to the image forming unit  4  by the paper feeding mechanism  32 . After an image has been formed on the second surface of paper sheet S by the image forming unit  4 , paper sheet S may be outputted from the image forming unit  4  and conveyed along the conveying path  51 . Then, the paper sheet S may be outputted from the apparatus main body  2  by the forwardly rotating output roller  52 . Paper sheet S then may be placed on the output tray  22 . 
         [0033]      FIG. 2  depicts a re-conveying unit  100  according to an embodiment of the invention. Re-conveying unit  100  may be disposed below the paper feed tray  31 . Re-conveying unit  100  may form a portion extending in the front-to-rear direction, e.g., a rear portion, of the re-conveying path  54 . The re-conveying unit  100  may have a substantially flat plate shape, as depicted in  FIG. 2 . The re-conveying unit  100  may be fixed to the apparatus main body  2 , and the paper feed tray  31  may be removably mounted to the re-conveying unit  100 . The re-conveying unit  100  may comprise a guide member  110 , a single-side regulation member  120 , and two or more sets of conveyor rollers  55 , e.g., two or more pairs of conveyor rollers  55 , as illustrated in  FIG. 3 . The re-conveying unit  100  may re-convey the paper sheet S along the re-conveying path  54 , such that paper sheet S may again pass through the image forming unit  4 . The image forming unit  4  then may form another image on a second surface, e.g., a second side, of the paper sheet S. The second surface may be opposite to the first surface. 
         [0034]    The guide member  110  may comprise a lower conveyance member  130  and an upper conveyance member  140 . The lower conveyance member  130  may be disposed below the paper sheet S and the upper conveyance member  140  may be disposed above the paper sheet S, which may pass along the re-conveying path  54 . The lower conveyance member  130  may have a width greater than the width of the paper sheet S, e.g., the length of the paper sheet S in the left-to-right direction. The lower conveyance member  130  may comprise a bottom wall portion  131 , guide ribs  132 , pivotal support portions  133  and a downstream end portion  134 . 
         [0035]    The bottom wall portion  131  may be substantially plate-shaped in its entirety, and a rear end portion thereof may be formed in an arc shape when viewed in a sectional view. The guide ribs  132  may project inwardly from the bottom wall portion  131  and may extend along the conveying direction of the paper sheet S. Each of the guide ribs  132  may be spaced from each other along the width direction of the paper sheet S. The pivotal support portions  133  may rotatably support driving rollers  151  and  161 , which will be described later, and may be formed at the left portion of the bottom wall portion  131 . 
         [0036]    The downstream end portion  134  may have a shape of a rib projecting upward from the bottom wall portion  131 , and may be formed to incline toward the rear side, e.g., the upstream side of the conveying direction of the paper sheet S from the left side to the right side. Thus, the entire leading end of the paper sheet S may be prevented from being caught in a joint of the lower conveyance member  130  and a downstream path forming portion  311 , which will be described in more detail herein, with reference to  FIG. 5 . 
         [0037]    The upper conveyance member  140 , which may be formed from a metal sheet, may comprise an upper wall portion  141 , a first end  142 A and a second end  142 B opposite to the first end  142 A. The upper wall portion  141  may have a size that is greater than the width of the paper sheet S. Each of first end  142 A and second end  142 B may be bent downward at respective left-to-right direction ends of the upper wall portion  141 . Each of first end  142 A and second end  142 B may be secured to, e.g., fixed to, or supported by the lower conveyance member  130 . Thus, because the upper conveyance member  140  may be independently secured or supported by the lower conveyance member  130  at both first end  142 A and second end  142 B, deformation of the upper conveyance member  140  may be reduced or prevented, even if an urging force is applied to the upper conveyance member  140 . In an embodiment of the invention, first end  142 A may be secured to the lower conveyance member  130 , e.g., by using fasteners, e.g., screws, and second end  142 B may be supported by the lower conveyance member  130 , e.g., by fitting into one or more recesses of lower conveyance member  130 . 
         [0038]    Mounting holes  141 A and escape holes  141 B may be formed at a left side of upper wall portion  141  therein. Mounting holes  141 A may be configured to mount the roller holders  153  and  163 , which will be described later. Similarly, escape holes  141 B may be configured to let pinch rollers  152  and  162 , which will be described later, to contact with the driving rollers  151  and  161 . A downstream end portion  143  of the upper wall portion  141  may incline toward the rear side, e.g., the upstream side of the conveying direction of the paper sheet S, from the left side to the right side. 
         [0039]    With this configuration, in the event of a paper jam in second conveyance rollers  55 B, which may be disposed on the left side of the downstream end portion  143 , a right corner of the paper sheet S may project further forward than the downstream end portion  143  does because the right side may be opened by the inclination of the downstream end portion  143 . Thus, when the paper feed tray  31  is removed to expose the front end of the re-conveying unit  100 , the right corner of the paper sheet S projecting from the downstream end portion  143  may be located easily, and the paper sheet S may be easily drawn out by the right corner. 
         [0040]    Two reinforcing ribs  141 C and  141 D may be disposed in the upper wall portion  141  to extend from one end to the other end in the left-to-right direction, which may further reduce or prevent deformation of the upper conveyance member  140 . Specifically, the reinforcing rib  141 C may project upward at a position near the downstream end portion  143  of the upper wall portion  141 . The reinforcing rib  141  C may extend from a position slightly spaced to the right, apart from the escape holes  141 B at the left end of upper wall portion  141 , to a position near a right end of the upper wall portion  141 . The reinforcing rib  141 D may project upward at a substantially center position of the upper wall portion  141  in the front-to-rear direction. Reinforcing rib  141 D may extend from a position near the right end of the upper wall portion  141  to a position over the escape holes  141 B in the left-to-right direction. Thus, deformation of the upper conveyance member  140  may be further reduced or prevented by the reinforcing rib  141 D, which may be longer than the reinforcing rib  141 C. 
         [0041]    The reinforcing ribs  141 C and  141 D may incline toward the rear side, e.g. the reinforcing ribs  141 C and  141 D may extend at an angle relative to the left-to-right direction, e.g., the direction perpendicular to the particular direction. Thus, the entire leading end of the paper sheet S may be prevented from being caught by the reinforcing ribs  141 C and  141 D. Additionally, if the leading end of the paper sheet S comes into contact with each of the reinforcing ribs  141 C and  141 D formed in an inclined manner, the paper sheet S may be obliquely fed along the reinforcing ribs  141 C and  141 D. 
         [0042]    The single-side regulation member  120  may contact with the left end of the paper sheet S, and may regulate the width direction position of the paper sheet S. The single-side regulation member  120  may be formed in an elongated shape extending in the front-to-rear direction, e.g., a particular direction, and may be disposed on the left side of the lower conveyance member  130 . A guide  122  may be disposed at a rear end portion  121  of the single-side regulation member  120 . The guide  122  may guide a left end of the paper sheet S toward the right side surface, e.g., a guide surface of the single-side regulation member  120  when the paper sheet S is conveyed with the left end thereof protruding to the left across the right side surface of the single-side regulation member  120 . 
         [0043]    The conveyor rollers  55  may convey the paper sheet S obliquely in the conveying direction, such that the left end of the paper sheet S may be in contact with the single-side regulation member  120 . The conveyor rollers  55  may be disposed at positions closer to the single-side regulation member  120  in the left-to-right direction, that is, the conveyor rollers  55  may be disposed at positions closer to the first end  142 A of the upper conveyance member  140  than the second end  142 B of the upper conveyance member  140 . In particular, the conveyor rollers  55  may comprise two pairs of first conveyance rollers  55 A and one pair of second conveyance rollers  55 B disposed further downstream in the conveying direction than the first conveyance rollers  55 A. 
         [0044]    One of the two pairs of the first conveyance rollers  55 A may be disposed at the rear end portion of the upper conveyance member  140  and the other may be disposed at a position adjacent to the second conveyance rollers  55 B, spaced apart from the one of the two pairs of the first conveyance rollers  55 A in the front direction. Each of the first conveyance rollers  55 A may comprise a first driving roller  151  and a first pinch roller  152 . The first driving roller  151  may receive a driving force transmitted from a driving source (not depicted). The first pinch roller  152  may be rotated following the first driving roller  151 . The first pinch roller  152  may contact the first surface of the paper sheet S when the paper sheet S is conveyed by first conveyance rollers  55 A. The first driving roller  151  may comprise a rubber conveyance surface and may be rotatably supported by the pivotal support portions  133  of the lower conveyance member  130 . 
         [0045]    The first pinch roller  152  may comprise a plastic conveyance surface, e.g. a surface that is harder and has less adhesive properties than, e.g., rubber. The conveyance surface of the first driving roller  151  may have a greater coefficient of friction than the plastic conveyance surface of the first pinch roller  152 . The “coefficient of friction” referred to in this application may be understood as the coefficient of friction of the surface relative to the paper sheet S. 
         [0046]    The first pinch roller  152  may be supported by the upper conveyance member  140  and may be located above the first driving roller  151 . Specifically, as depicted in  FIG. 1 , the first pinch roller  152  may be in contact with the first surface of paper sheet S, e.g., the surface on which an image has already been formed. The first pinch roller  152  may be supported by a roller holder  153 , such that the first pinch roller  152  may be rotatable and slidable in the vertical direction. Roller holder  153  may comprise a resin. First pinch roller  152  may be urged downward by a torsion spring  154 , e.g., an urging member. Torsion spring  154  may be fixed to or supported by the roller holder  153 . Thus, with this configuration, the first pinch roller  152  may be urged toward the first driving roller  151  by the torsion spring  154 , such that the first pinch roller  152  may be in contact with the first driving roller  151  when the re-conveying unit  100  is in an assembled state as depicted in  FIG. 2 . 
         [0047]    The first pinch roller  152  may incline with respect to the first driving roller  151  in the assembled state of the re-conveying unit  100 . Specifically, as depicted in  FIG. 4 , a central axis  152 A of the first pinch roller  152  may be inclined at a predetermined angle α. Specifically, the pinch roller  152  may be disposed at an angle, e.g., a first angle, relative to the first driving roller in the left-to-right direction, e.g., a direction perpendicular to the particular direction. Thus, the predetermined angle α may be an acute angle with respect to a central axis  151 A of the first driving roller  151  in the left-to-right direction. In an embodiment of the invention, the predetermined angle α may be 6 degrees, for example, but in other embodiments, the predetermined angle α may have other values. 
         [0048]    As depicted in  FIG. 3 , the second conveyance rollers  55 B may be disposed at the downstream end portion  143  of the upper conveyance member  140 . A distance between first conveyance rollers  55 A and second conveyance rollers  55 B may be greater than one half of a width of re-conveying unit  100  in the left-to-right direction, e.g., the direction perpendicular to the particular direction. The second conveyance rollers  55 B may comprise a second driving roller  161  and a second pinch roller  162 . The second driving roller  161  may receive a driving force transmitted from a driving source, e.g., a motor (not depicted). The second pinch roller  162  may rotate following the second driving roller  161 . The second pinch roller  162  may contact the first surface of the paper sheet S when the paper sheet S is conveyed by second conveyance rollers  55 B. The second driving roller  161  may comprise a rubber conveyance surface and may be rotatably supported by the pivotal support portions  133  of the lower conveyance member  130 . As depicted in  FIG. 3 , upper conveyance member  140  may have escape holes  141 B. Each of first pinch roller  152  and second pinch roller  162  may contact the sheet through one of escape holes  141 B. Each of first pinch roller  152  and pinch roller  162  may rotate in one of escape holes  141 B. As depicted in  FIG. 4 , the second pinch roller  162  may be disposed closer to the single side regulation member  120  than the first pinch roller  152 . 
         [0049]    The second driving roller  161  and the two first driving rollers  151  may be arranged in the front-to-rear direction, and may be connected by two driving force transmission members  171  and  172 . Each of transmission members  171  and  172  may comprise a shaft and a gear. A driving source of the apparatus main body  2  may be connected to the driving roller  151  of the middle position via a plurality of gears, or any other suitable connecting mechanism. After the driving force from the driving source of the apparatus main body  2  is transmitted to the driving roller  151  in the middle, the driving force may be transmitted to the front and rear driving rollers  161  and  151  via each of the driving force transmission members  171  and  172 . 
         [0050]    Similarly to the first pinch roller  152 , the second pinch roller  162 , which may be supported by the upper conveyance member  140 , also may be disposed in contact with the first surface of the paper sheet S. Also, similarly to the first pinch roller  152 , the second pinch roller  162  may be supported by the roller holder  163  to be rotatable and slidable in the vertical direction. Second pinch roller  162  may be urged downward by the torsion spring  164 , which may be fixed to the roller holder  163 . With this configuration, the second pinch roller  162  may be urged toward the second driving roller  161  by the torsion spring  164  to be in contact with the second driving roller  161  when the re-conveying unit  100  is in an assembled state as depicted in  FIG. 2 . As depicted in  FIGS. 2 and 4 , roller holder  163  may be disposed above the upper conveyance member  140 , and upper conveyance member  140  may secure or support roller holder  163 . Roller holder  163  may be disposed to overlap upper conveyance member  140  in the vertical direction. As set forth above, roller holder  163  may support second pinch roller  162  to be rotatable and slidable in the vertical direction. Roller holder  163  also may secure second pinch roller  162  such that second pinch roller  162  may contact the sheet through one of the plurality of holes  141 B in the upper conveyance member  140 . Roller holder  163  may secure second pinch roller  162  such that the central axis of the second pinch roller  162  is not aligned with the upper conveyance member  140  in the vertical direction. 
         [0051]    The second pinch roller  162  may comprise a rubber conveyance surface, which may have a greater coefficient of friction than the first pinch roller  152 . Thus, even if the first pinch roller  152  slides on the printing surface of the paper sheet S, sliding of the paper sheet S on the printing surface may be reduced, and paper sheet S may be reliably obliquely conveyed by the second pinch roller  162 , because the coefficient of friction of second pinch roller  162  may be greater than that of the first pinch roller  152 . 
         [0052]    The second driving roller  161  may have a greater coefficient of friction than the second pinch roller  162 . That is, the rubber which forms the conveyance surface of the second driving roller  161  may have a greater coefficient of friction than the rubber that forms the conveyance surface of the second pinch roller  162 . Thus, second pinch roller  162  may allow sliding on the printing surface and may feed the paper sheet S in a straight line in the conveying direction only by the second driving roller  161  after the paper sheet S comes into contact with the single-side regulation member  120 . Thus, folding of the end of the paper sheet S, which may be caused by conveying the paper sheet S too close to the single-side regulation member  120 , may be reduced or prevented. 
         [0053]    In the assembled state of the re-conveying unit  100 , the second pinch roller  162  may be inclined against the second driving roller  161  at an inclination angle β. Specifically, the pinch roller  162  may be disposed at an angle, e.g., a second angle, relative to the second driving roller in the left-to-right direction, e.g., the direction perpendicular to the particular direction. In an embodiment of the invention, inclination angle β may be, for example, 3 degrees, although in other embodiments of the invention, inclination angle β may have different values. In an embodiment of the invention, inclination angle β may be smaller than the inclination angle α of the first pinch roller  152  in the left-to-right direction, as illustrated in  FIG. 4 . That is, a central axis  162 A of the second pinch roller  162  may be inclined at an angle β, which may be less than the angle α, with respect to the central axis  161 A of the second driving roller  161  in the left-to-right direction. 
         [0054]    Thus, with the strong conveying force of the rubber conveying surface of second pinch roller  162 , folding of the end of the paper sheet S may be further reduced or prevented. Specifically, because a component of force applied to the paper sheet S in the direction perpendicular to the conveying direction by the first pinch roller  152  may be smaller than a component of force applied to the paper sheet S in the direction perpendicular to the conveying direction by the second pinch roller  162 , folding of the end of the paper sheet S may be reduced or prevented. 
         [0055]    The second conveyance rollers  55 B, which may be disposed the furthest downstream in the conveying direction, may be positioned within the inclination of the downstream end portion  143  of the upper conveyance member  140  described above, e.g., the position which overlaps the inclination of the downstream end portion  143  in the width direction. Thus, the paper sheet S may be easily drawn from the right side of the inclined portion even if, for example, a paper jam occurs in a state in which the paper sheet S is caught in the second conveyance rollers  55 B. The second conveyance rollers  55 B also may be positioned closer to the first end  142 A of the upper conveyance member  140  than the second end  142 B of the upper conveyance member  140 . 
         [0056]    The downstream end portion  143  of the upper conveyance member  140  may be shorter than the downstream end portion  134  of the lower conveyance member  130  in the sheet conveying direction. Thus, the downstream end portion  143  of the upper conveyance member  140  may be disposed further upstream than the downstream end portion  134  of the lower conveyance member  130  in the sheet conveying direction. The downstream end portion  143  may extend from the first end  142 A to the second end  142 B of the upper conveyance member  140  at an angle relative to the left-to-right direction, e.g., the direction perpendicular to the particular direction. An angle formed by the first end  142 A and the downstream end portion  143  may be less than 90 degrees. 
         [0057]    First end  142 A of upper conveyance member  140  may extend further than the second end  142 B of upper conveyance member  140  in the front-to-back direction, e.g., the particular direction. Because first end  142 A may extend further than second end  142 B in the particular direction, first end  142 A may be disposed closer to the image recording unit  4  in the conveyance direction than second end  142 B. 
         [0058]    Lower conveyance member  130  also may comprise a first end  135 A and a second end  135 B opposite to the first end  135 A in the left-to-right direction, wherein the first end  135 A of the lower conveyance member may be a left end, and the second end  135 B of the lower conveyance member may be a right end, when the re-conveying unit  100  is positioned as depicted in  FIG. 3 . Downstream end portion  134  of the lower conveyance member  130  may extend from the first end  135 A of lower conveyance member  130  to the second end  135 B of lower conveyance member  130  at an angle relative to the left-to-right direction, e.g., the direction perpendicular to the particular direction. An angle formed by the first end  135 A and the downstream end portion  134  may be less than 90 degrees. 
         [0059]    The first end  135 A of lower conveyance member  130  may extend further than the second end  135 B of lower conveyance member  140  in the front-to-back direction, e.g., the particular direction. Because the first end  135 A of lower conveyance member  130  may extend further than the second end  135 AB of lower conveyance member  130  in the particular direction, the first end  135 A of lower conveyance member  130  may be disposed closer to the image recording unit  4  in the conveyance direction than the second end  135 B of lower conveyance member  130 . 
         [0060]    The second conveyance rollers  55 B also may be positioned closer to the first end  135 A of the lower conveyance member  130  than the second end  135 B of the lower conveyance member  130 . The second conveyance rollers  55 B may convey the paper sheet S to first contact the downstream end portion  134  of the lower conveyance member  130  at a position closer to the second end  135 B of the lower conveyance member  130  than the first end  135 A of the lower conveyance member  130 . 
         [0061]    As depicted in  FIG. 5 , a downstream path forming portion  311  may be disposed in the lower front portion of the paper feed tray  31 . The downstream path forming portion  311  may comprise a path on which the paper sheet S fed from the guide member  110  of the re-conveying path  100  is conveyed. The downstream path forming portion  311  may be a portion of the conveying unit  5 , e.g., which may form a front portion of the section of the re-conveying path  54  extending in the front-rear direction, as depicted in  FIG. 1 . The downstream end portion  134  of the re-conveying unit  100  may be connected to the downstream path forming portion  311 . 
         [0062]    Specifically, an upstream end portion  313  of a lower forming portion  312  that forms a lower portion of the downstream path forming portion  311  may have a shape that conforms to the downstream end portion  134  of the lower conveyance member  130 . Because the paper feed tray  31  may be removably mounted to the apparatus main body  2 , the downstream path forming portion  311  may be removably mounted to the re-conveying unit  100  of the apparatus main body  2 . 
         [0063]    As depicted in  FIG. 6 , a pair of both-side regulation members  314  may be disposed in the paper feed tray  31 . Each of the pair of both-side regulation members  314  may contact with respective width direction ends of the paper sheet S, and may regulate the position of the paper sheet S in the width direction. With this configuration, for the printing on the first surface of the paper sheet S, both the right and left ends of the paper sheet S may contact with each both-side regulation members  314 . Thus, the paper sheet S may be positioned in the width direction; and, for the printing on the second surface of the paper sheet S, the left end of the paper sheet S may contact with the single-side regulation member  120 , which may position the paper sheet S in the width direction. 
         [0064]    In the configuration described above, the following advantageous effects may be provided in the present embodiment. Because the coefficient of friction of the second pinch roller  162  is greater than that of the first pinch roller  152 , frictional force with respect to the first surface of the paper sheet S may be provided by the second pinch roller  162  having high coefficient of friction even if the first pinch roller  152  slides on the first surface of the paper sheet S. As a result, oblique feeding capability of the conveyor rollers  55  may be improved. 
         [0065]    In an embodiment of the invention, because the downstream end portion  134  of the lower conveyance member  130  is formed to incline toward the rear side from the left to the right side, the entire leading end of the paper sheet S may be prevented from being caught by the joint of the lower conveyance member  130  and the downstream path forming portion  311 . Because the lower conveyance member  130  is formed to incline similarly to the upper conveyance member  140 , the right corner of the paper sheet S may project from each of the downstream end portions  143  and  134  when the paper feed tray  31  is removed, thus providing a space for a user&#39;s fingers above and below the corner of the paper sheet S, thereby allowing a user to hold the corner of the paper sheet S from above and below with the fingers to thereby clear the jammed paper sheet S. 
         [0066]    In another embodiment, the second end may be longer than the first end, and an angle formed by the first end and the downstream end may be greater than 90 degrees. In another embodiment, the downstream end may be curved. In another embodiment, the downstream end may have one or more straight portions and one or more angled portions. 
         [0067]    In an embodiment of the invention, the upper conveyance member  140  may be formed from a metal. In addition, the upper conveyance member  140  may have a reduced thickness in the vertical direction and increased rigidity. Thus, the apparatus main body  2  may be compact in the vertical direction and, at the same time, deformation of the upper conveyance member  140  may be further reduced or prevented. In addition, in an embodiment of the invention, pinch rollers  152  and  162  and the torsion springs  154  and  164  are supported by the resin-made roller holders  153  and  163 . In this embodiment, a holding configuration of the pinch rollers  152  and  162  may easily be formed. 
         [0068]    In the above-described embodiments of the invention, the first pinch roller  152  may comprise a resin and the driving rollers  151  and  161  and the second pinch roller  162  may comprise a rubber. Nevertheless, the invention is not limited to this configuration. In other embodiments of the invention, the rollers may be made of any materials and configured in any manner such that the first driving roller  151  has a coefficient of friction which is greater than that of the first pinch roller  152  and the second pinch roller has a coefficient of friction which is greater than that of the first pinch roller is satisfied. 
         [0069]    In the above-described embodiments of the invention, two pairs of the first conveyance rollers  55 A may be provided in the above-described embodiment. Nevertheless, in other embodiments of the invention, the number of the pairs of the first conveyance rollers  55 A may be one, or three or more. 
         [0070]    In the above-described embodiments of the invention, the paper feed tray  31  may be removably mounted to the apparatus main body  2 , and may be used as a recording sheet container unit. In other embodiments, however, the recording sheet container unit may be a paper feed tray which is merely movable with respect to the apparatus main body and thus is not removable from the apparatus main body. In still other embodiments, the recording sheet container unit may be removed from the apparatus main body  2  only by using a tool, e.g., a screwdriver. In yet other embodiments of the invention, the recording sheet container may be formed integrally with the apparatus main body at a lower portion of the apparatus main body. In further embodiments of the invention, the downstream path forming portion may be formed integrally with the apparatus main body, and the guide member may be removably mounted to the downstream path forming portion of the apparatus main body. 
         [0071]    In the above-described embodiments, the image forming unit  4  may comprise the exposure unit  41 . Nevertheless, in other embodiments, an LED head may be used instead of the exposure unit  41 , a belt-like photoconductor may be used instead of the photosensitive drum  42 A, and a cylindrical-shaped fixing film slidably supported by a guide may be used instead of the heat roller  44 A. Other components, e.g., a conductive brush and a conductive plate spring, to which transfer bias is applied may be used instead of the transfer roller  43 B. 
         [0072]    Although the above-described embodiments refer to a color printer  1  for convenience, the invention is not limited to the same. For example, embodiments of the invention may be applied to a monochrome printer and any other image forming device, e.g., a copying machine and a multi-function device. 
         [0073]    In the above-described embodiments of the invention, the re-conveyed paper sheet S is conveyed below the paper feed tray  31 . Nevertheless, in other embodiments, for example, the re-conveyed paper sheet may be conveyed above the paper feed tray. In the above-described embodiments of the invention, the torsion springs  154  and  164  may be urging members. Nevertheless, in other embodiments of the invention, any other type of urging member may be used, e.g., a flat spring and wire spring. 
         [0074]    In the above-described embodiments of the invention, the re-conveying unit  100  may be disposed below the paper feed tray  31 , however, in other embodiments, the re-conveying unit  100  may be disposed above the paper feed tray  31 . In addition, in the above-described embodiments, the upper conveyance member  140  may be formed from a metal sheet, however, in other embodiments, the upper conveyance member  140  may be formed of any other suitable material, e.g., a resin. In an embodiment of the invention, if the upper conveyance member  140  is formed of resin, the upper conveyance member  140  and the roller holder may be formed integrally with each other. 
         [0075]    While the invention has been described in connection with the above embodiments, it will be understood by those of ordinary skill in the art that other variations and modifications of the preferred embodiments described above may be made without departing from the scope of the invention. Other embodiments will be apparent to those of ordinary skill in the art from a consideration of the specification or practice of the invention disclosed herein. The specification and the described examples are considered as exemplary only, with the true scope and spirit of the invention indicated by the following claims.