Abstract:
An image forming apparatus, comprising: a housing having a sheet discharge tray, a first opening, and a second opening disposed on an upper side of the first opening; an image forming unit; a sheet discharge path communicating with the first opening; a re-conveying path communicating with the second opening; and a swinging member having a first surface facing the first opening and a second surface, wherein the swinging member has a first end area swingably supported by the housing, a second end area, and a rib; the swinging member is disposed to be movable between a first position and a second position at which the second end area gets higher; and the rib is formed on the second surface opposing the first surface facing the sheet discharge tray in a state where the swinging member is disposed at the second position.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority under 35 U.S.C. §119 from Japanese Patent Application No. 2015-070966, filed on Mar. 31, 2015. The entire subject matter of the application is incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    Aspects of the present disclosures relate to an electrophotographic type image forming apparatus. 
         [0004]    2. Related Art 
         [0005]    Printers configured to reversing front and back sides of a sheet being conveyed to form images on both sides of the sheet are known. 
         [0006]    One of the printers of this type includes an image forming unit configured to form an image on a sheet, a fixing unit configured to fix the image on the sheet, a sheet conveying path being a conveying path for discharging the sheet, a drawing path being a conveying path for reversing the sheet, a paper discharge tray disposed on an upper surface of a printer body, a guide which is disposed on an upper side of the paper discharge tray and is formed to continue the drawing path, and a reversing roller disposed on the drawing path. 
         [0007]    In the printer described above, the sheet for which image formation has been finished is discharged to the paper discharge tray after passing through the fixing unit and the sheet conveying path. Regarding the sheet for which an image has been formed on one side of the sheet and an image it to be formed on the other side of the sheet, the sheet is guided to the drawing path after passing through the fixing unit. Then, the sheet entered the drawing path is conveyed again to the image forming unit by causing the reversing roller to inversely rotate in a state where the sheet is placed on the upper side of the paper discharge tray to be along the guide. 
       SUMMARY 
       [0008]    In the above described printer, when the sheet enters the drawing path, the sheet being conveyed may contact the guide or the sheets placed on the paper discharge tray. When the sheet entering the drawing path contacts other components in this way, the conveying resistance of the sheet being re-conveyed may become large. 
         [0009]    In consideration of the above, aspects of the present disclosures provide an image forming apparatus capable of smoothly re-conveying a sheet. 
         [0010]    According to an aspect of the disclosures, there is provided an image forming apparatus, comprising: a housing having a sheet discharge tray, a first opening, and a second opening disposed on an upper side with respect to the first opening; an image forming unit configured to form an image on a sheet; a sheet discharge path configured to guide the sheet from the image forming unit to the sheet discharge tray, the sheet discharge path communicating with the first opening; a re-conveying path configured to be disposed side by side with the sheet discharge path in a horizontal direction and to guide the sheet to the image forming unit, the re-conveying path communicating with the second opening; and a swinging member disposed to face the first opening, the swinging member comprising a first surface disposed to face the first opening and a second surface opposite to the first surface. In this configuration, the swinging member further comprises a first end area at which the swinging member is swingably supported by the housing, a second end area opposing the first end area, and a rib formed to extend from the first end area to the second end area. The swinging member is disposed to be movable between a first position and a second position at which the second end area is disposed at a position higher than a position of the second end area defined when the swinging member is disposed at the first position. The rib is formed on the second surface of the swinging member opposing the first surface of the swinging member facing the sheet discharge tray in a state where the swinging member is disposed at the second position. 
     
    
     
       BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS 
         [0011]      FIG. 1  is a central cross sectional view of a printer according to a first embodiment. 
           [0012]      FIG. 2  is a plan view of the printer  1  shown in  FIG. 1 . 
           [0013]      FIG. 3  is an A-A cross section of the printer  1  shown in  FIG. 1 . 
           [0014]      FIG. 4  is a perspective view of a stack lever shown in  FIG. 1 , viewed from an upper front side. 
           [0015]      FIG. 5  is a plan view of a printer according to a second embodiment. 
           [0016]      FIG. 6  is an enlarged perspective view of a central portion of the printer  1  shown in  FIG. 5  viewed from an upper front side. 
       
    
    
     DETAILED DESCRIPTION 
     First Embodiment 
       [0017]    Hereafter, an image forming apparatus  1  according to a first embodiment will be explained. In the following explanation, directions are referred to with reference to direction arrows shown in the accompanying drawings. 
         [0018]    1. Overall Configuration of Image Forming Apparatus 
         [0019]    As shown in  FIG. 1 , the image forming apparatus  1  is a laser printer. The image forming apparatus  1  includes a housing  2  having a paper discharge opening  2 A, an image forming unit  3 , a paper supply unit  4  having a supply path  4 A, and a paper discharge unit  5  having a paper discharge path  5 A. 
         [0020]    The housing  2  forms an outer covering of the image forming apparatus  1 . The housing  2  has a box-shape. The housing  2  accommodates the image forming unit  3 , the paper supply unit  4  and the paper discharge unit  5 . The housing  2  includes a paper discharge tray  2 B. 
         [0021]    The paper discharge tray  2 B is disposed on an upper wall of the housing  2 . The paper discharge tray  2 B has a recessed shape which is recessed from an upper surface of the housing  2 . 
         [0022]    The paper discharge opening  2 A is disposed on an upper rear side of the paper discharge tray  2 B. The paper discharge opening  2 A is opened in the front and rear direction. With this configuration, the paper discharge opening  2 A lets the inside and the outside of the housing  2  communicate with each other. 
         [0023]    The image farming unit  3  is disposed in a central portion of the image forming apparatus  1 . The image forming unit  3  includes a plurality of (four in this embodiment) photosensitive drums  6 , a plurality of (four in this embodiment) developing devices  7 , an exposing device  8 , a transfer unit  9  and a fixing unit  10 . 
         [0024]    The four photosensitive drums  6  are disposed to be spaced from each other in the front and rear direction. Each photosensitive drum  6  has a cylindrical shape extending in the left and right direction. 
         [0025]    The four developing devices  7  are disposed to be spaced from each other in the front and rear direction. Each developing device  7  is disposed on the upper front side of the corresponding photosensitive drum  6 . The developing device accommodates toner. The developing device  7  includes a developing roller  7 A. 
         [0026]    The developing roller  7 A is disposed at a lower rear end part of the developing device  7 . The developing roller  7 A contacts the corresponding photosensitive drum  6 . The developing roller  7 A supplies toner to the corresponding photosensitive drum  6 . 
         [0027]    The exposing device  8  is disposed above the four developing devices  7 . The exposing device  8  is able to emit laser light L based on image data. The laser light L emitted from the exposing device  8  is incident on surfaces of the photosensitive drums  6  while passing through rear sides of the respective developing devices  7 . 
         [0028]    The transfer unit  9  is disposed under the four photosensitive drums  6 . The transfer unit  9  is disposed to be along the front and rear direction. The transfer unit  9  includes a belt  9 A and a plurality of (four in this embodiment) transfer rollers  9 B. 
         [0029]    The belt  9 A is an endless belt. The belt  9 A is disposed such that an upper surface of the belt  9 A contacts the four photosensitive drums  6 . The belt  9 A is able to circulate such that the upper surface of the belt  9 A moves from the front side to the rear side. 
         [0030]    The four transfer rollers  9 B are disposed to be spaced from each other in the front and rear direction. The transfer roller  9 B is disposed on the lower side of the corresponding photosensitive drum  6 . The transfer rollers  9 B are disposed to sandwich the belt  9 A between the transfer rollers  9 B and the photosensitive drums  6 . 
         [0031]    The fixing unit  10  is disposed on the rear side of the transfer unit  9 . The fixing unit  10  includes a heat roller  10 A and a pressure roller  10 B contacting the heat roller  10 A. 
         [0032]    The paper supply unit  4  is disposed in a lower end part of the image forming apparatus  1 . The paper supply unit  4  is configured to supply a sheet (a sheet of paper P in the embodiment) to the image forming unit  3 . The paper supply unit  4  includes a paper supply tray  11 . 
         [0033]    The supply path  4 A is formed to extend upward from an upper front end part of the paper supply tray  11 , to bend rearward, and to extend to the front side of the frontmost photosensitive drum  6 . 
         [0034]    The paper supply tray  11  is disposed under the transfer unit  9 . The paper supply tray  11  is a tray capable of accommodating sheets of paper P. 
         [0035]    The paper discharge unit  5  is disposed at a upper rear end part of the image forming apparatus  1 . The paper discharge unit  5  is configured to discharge the sheet of paper P which has passed through the fixing unit  10 , to the paper discharge tray  2 B. The paper discharge unit  5  includes a paper discharge roller  15  and an opposing roller  16 . 
         [0036]    The paper discharge path  5 A is formed to extend upward from an upper rear side of the fixing unit  10 , to bend frontward, and to communicate with the paper discharge opening  2 A. 
         [0037]    The paper discharge roller  15  is disposed at a front end part of the paper discharge path  5 A. The paper discharge roller  15  is able to rotate when a driving force from a driving source M 1  is inputted thereto. 
         [0038]    The opposing roller  16  is disposed at the front end part of the paper discharge path  5 A. The opposing roller  16  is disposed under the paper discharge roller  15 . The opposing roller  16  contacts the paper discharge roller  15 . The opposing roller  16  is able to rotate following rotation of the paper discharge roller  15 . 
         [0039]    When the image forming apparatus  1  starts image forming operation, the exposing device  8  emits the laser light L to expose the surfaces of the photosensitive drums  6 . As a result, an electrostatic latent image based on the image data is formed on each photosensitive drum  6 . 
         [0040]    Next, the toner is supplied to the electrostatic latent image on the surface of the photosensitive drum  6  by the development roller  7 A. As a result, a toner image is held on the surface of the photosensitive drum  6 . 
         [0041]    Then, the sheet of paper P in the paper supply tray  11  is supplied one by one to a position between the frontmost photosensitive drum  6  and the belt  9 A while passing through the supply path  4 A. The sheet of paper P is conveyed by the belt  9 A from the front side to the rear side to sequentially contact the four photosensitive drums  6 . The toner image on the surface of the photosensitive drum  6  is transferred to the sheet of paper when the sheet of paper P contacts the photosensitive drum  6 . 
         [0042]    Next, the sheet of paper P is heated and pressurized when the sheet of paper P passes through a position between the heat roller  10 A and the pressure roller  10 B. As a result, the toner image is fixed on the sheet of paper P. 
         [0043]    Next, the sheet of paper P is discharged to the outside of the housing  2  by passing through the paper discharge path  5 A and the paper discharge opening  2 A, and is stacked on the paper discharge tray  2 B. 
         [0044]    2. Configuration Relating to Re-Conveying of Sheet of Paper 
         [0045]    The image forming apparatus  1  includes a re-conveying unit  12  having a reversing path  12 A and a relay path  12 B, a flap  31 , a guide part  35 , a first stack lever  41 L, and a second stack lever  41 R. In the image forming apparatus  1 , the housing  2  includes a passing opening  2 C. 
         [0046]    (1) Passing Opening 
         [0047]    The passing opening  2 C is disposed on an upper rear end part of the housing  2 . The passing opening  2 C is opened in the front and rear direction. With this configuration, the passing opening  2 C lets the outside and the inside of the housing  2  communicate with each other. The passing opening  2 C is disposed on the upper rear side of the paper discharge opening  2 A. That is, the passing opening  2 C is disposed on the upper side of the paper discharge opening  2 A in the up and down direction, and is disposed on the rear side of the paper discharge opening  2 A in the front and rear direction. 
         [0048]    (2) Re-Conveying Unit 
         [0049]    The re-conveying unit  12  includes a first reversing roller  21 , a first opposing roller  22 , a second reversing roller  23  and a second opposing roller  24 . 
         [0050]    The re-conveying unit  12  is disposed in a rear end part and a lower end part of the image forming apparatus  1 . The re-conveying unit  12  is configured to convey the sheet of paper P which has passes through the fixing unit  10  to a midway position on the supply path  4 A. 
         [0051]    The reversing path  12 A is disposed on the rear side of the paper discharge path  5 A. The reversing path  12 A is formed to extend to the upper rear side from the fixing unit  10 , to bend upward after passing through the lower side of the flap  31 , and then to bend to the upper front side in a manner similar to the paper discharge path  5 A before communicating with the passing opening  2 C. 
         [0052]    The relay path  12 B is formed to extend to the lower front side from a part of the reversing path  12 A disposed on the lower side of the flap  31 , to extend frontward on the lower side of the paper supply tray  11  after being bent frontward, and further to bend to the upper front side before communicating with the supply path  4 A. 
         [0053]    The first reversing roller  21  is disposed on the reversing path  12 A. The first reversing roller  21  is disposed on the lower rear side of the passing opening  2 C to be spaced from the passing opening  2 C. The first reversing roller  21  can be rotated by a driving force applied from a driving source M 2 . The rotational direction of the first reversing roller  21  can be switched between a first rotational direction in which the sheet of paper P is conveyed upward and a second rotational direction which is opposite to the first rotational direction and in which the sheet of paper P is conveyed downward. 
         [0054]    The first opposing roller  22  is disposed on the reversing path  12 A. The first opposing roller  22  is disposed on the lower front side of the first reversing roller  22 . The first opposing roller  22  contacts the first reversing roller  22 . The first opposing roller  22  is rotatable by following the first reversing roller  21 . 
         [0055]    The second reversing roller  23  is disposed on the reversing path  12 A. The second reversing roller  23  is disposed oa the lower side of the first reversing roller  21  to be spaced from the first reversing roller  21 . The second reversing roller  23  can be rotated by a driving force applied from a driving source M 3 . The rotational direction of the second reversing roller  23  can be switched between a third rotational direction in which the sheet of paper P is conveyed upward and a fourth rotational direction which is opposite to the third rotational direction and in which the sheet of paper P is conveyed downward. 
         [0056]    The second opposing roller  24  is disposed on the reversing path  12 A. The second opposing roller  24  is disposed on the front side of the second reversing roller  23 . The second opposing roller  24  contacts the second reversing roller  23 . The second opposing roller  24  is rotatable by following the second reversing roller  23 . 
         [0057]    (3) Flap 
         [0058]    The flap  31  is disposed on the upper rear side of the fixing unit  10 . The flap  31  is disposed between the lower end part of the paper discharge path  5 A and the lower end part of the reversing path  12 A. The flap  31  has a plat-like shape extending in the up and down direction. The flap  31  is rotatable, about the upper end part of the flap  31 , between a discharging position illustrates by a solid line where the flap  31  closes the reversing path  12 A and releases the paper discharge path  5 A and a conveying position illustrated by a virtual line where the flap  31  releases the reversing path  12 A and closes the paper discharge path  5 A. 
         [0059]    (4) Guide Part 
         [0060]    The guide part  35  is a part of the upper surface of the housing  2 . Specifically, as shown in  FIG. 2 , the guide part  35  is a central portion of the upper surface of the housing  2  in the left and right direction and is a rear end part of the upper surface of the housing  2 . The guide part  35  is disposed between the paper discharge opening  2 A and the passing opening  2 C in the front and rear direction. As shown in  FIG. 1 , the guide part  35  is disposed between the paper discharge opening  2 A and the passing opening  2 C in the up and down direction. As shown in  FIG. 2 , the guide part  35  includes a flat surface  35 A and a plurality of ribs  35 B. 
         [0061]    The flat surface  35 A forms a lower end surface of the guide part  35 . The flat surface  35 A has a rectangular shape when viewed as a plan view. The flat surface  35 A is formed to extend in the horizontal direction. 
         [0062]    The rib  35 B projects upward from the flat surface  35 A. The rib  35 B extends in the front and rear direction. The plurality of ribs  35 B are disposed to have constant intervals therebetween in the left and right direction. When projected in the up and down direction, the front edges of the ribs  35  overlap with the paper discharge opening  2 A and the rear edges of the ribs  35 B overlap with the passing opening  2 C (see  FIG. 1 ). 
         [0063]    As shown in  FIG. 2 , the front end part the guide part  35  adjoins the rear end part of the paper discharge tray  2 B when viewed as a plan view. As shown in  FIG. 1 , the rear end part of the guide part  35  forms the lower edge of the passing opening  2 C. (5) First Stack Lever and Second Stack Lever 
         [0064]    As shown in  FIGS. 2 and 3 , the first stack lever  41 L is attached to the upper and left part of the housing  2 . As shown in  FIG. 4 , the first stack lever  41 L has a plate-like shape extending in the front and rear direction, and comprises a first surface  47 A facing the paper discharge opening  2 A when the first stack lever  41 L is disposed at a position indicated by a virtual line in  FIG. 1 , and a second surface  47 B opposite to the first surface  47 A. In the following explanation, the configuration of each of the first stack lever  41 L and the second stack lever  41 R is explained with reference to a state where each of the first stack lever  41 L and the second stack lever  41 R is disposed to be along a direction connecting the lower front side with the upper rear side as shown in  FIG. 1 . 
         [0065]    As shown in  FIG. 4 , the first stack lever  41 L includes an extending part  42 , a presser part  43  and a plurality of (four in this embodiment) ribs  44 . 
         [0066]    The extending part  42  is rectangular when viewed as a plan view, and has a plate-like shape extending in the front and rear direction. The extending part  42  has a substantially uniform thickness from the front end part to the rear end part. The extending part  42  includes a first shaft part  45  and a second shaft part  46 . 
         [0067]    The first shaft part  45  projects leftward from the left surface of the rear end part of the extending part  42 . The first shaft part  45  has a columnar shape extending in the left and right direction. 
         [0068]    The second shaft part  46  projects rightward from the right surface of the rear end part of the extending part  42 . The second shaft part  46  has a columnar shape extending in the left and right direction. When projected in the left and right direction, the second shaft part  46  coincides with the first shaft part  45 . 
         [0069]    The presser part  43  is formed to extend to the upper front side from the rear end part of the extending part  42 . That is, the first stack lever  41 L has a bent shape projecting to the lower side. The presser part  43  includes a continuing part  43 A and an expanded part  43 B. 
         [0070]    The continuing part  43 A is formed to extend to the upper front side from the front end part of the extending part  42 . The thickness of the continuing part  43 A gradually increases toward the upper front side. 
         [0071]    The expanded part  43 B is formed to expand from the front end part of the continuing part  43 A toward the upper front side. When viewed in the left and right direction, an outer circumferential surface of the expanded part  43 B is bent in a shape of an arc such that the upper front part of the expanded part  43 B is expanded. 
         [0072]    The rib  44  is formed to project upward from the upper surface of the extending part  42  and the upper surface of the presser part  43 . Specifically, the rib  44  linearly extends, in the front and rear direction, from the upper surface of the rear end part of the extending part  42  to the upper surface of the expanded part  43 B. A front edge  44 A of the upper surface of the rib  44  is disposed on the upper surface of the outer circumferential surface  43 C of the expanded part  43 B. A rear edge  44 B of the upper surface of the rib  44  is disposed on the upper surface of the rear end part of the extending part  42 . The plurality of ribs  44  are disposed to have constant intervals therebetween in the left and right direction. 
         [0073]    As shown in  FIG. 3 , the first stack lever  41 L is disposed close to the left end part of the paper discharge opening  2 A and is disposed on the lower front side of the left end part of the passing opening  2 C to be spaced from the left end part of the passing opening  2 C. The first stack lever  41 L is supported by the housing  2  such that the first shaft part  45  and the second shaft part  46  are rotatably supported by the housing  2 . Specifically, the first shaft part  45  and the second haft part  46  of the first stack lever  41 L are disposed on the lower side of the guide part  35  and upper side of the paper discharge tray  2 B. The first shaft par  45  and the second shaft part  46  of the first stack lever  41 L are rotatably supported by a part of the housing  2  close to the left end part of the paper discharge opening  2 A. 
         [0074]    With this configuration, the first stack lever  41 L is able to rotate about an axis extending, at the rear end part of the first stack lever  41 L, in the left and right direction. In this embodiment, each of the first stack lever  41 L and the second stack lever  41 R has the shaft parts  45  and  46  rotatably supported by the housing  2 . However, in another embodiment, the housing  2  may have shaft parts and each of the first stack lever  41 L and the second stack lever  41 R may have holes into which the shaft parts of the housing  2  are inserted so that each of the first stack lever  41 L and the second stack lever  41 R is rotatably supported by the housing  2 . 
         [0075]    The second stack lever  41 R is disposed close to the right end part of the paper discharge opening  2 A, and is disposed on the lower front side of the right end part of the passing opening  2 C to be spaced from the passing opening  2 C. The second stack lever  41 R is attached to the upper and right end part of the housing  2 . The second stack lever  41 R has substantially the same configuration as that of the first stack lever  41 L other than the fact that the second stack lever  41 R is attached to the upper and right end part of the housing  2 . 
         [0076]    Each of the first stack lever  41 L and the second stack lever  41 R is provided to be able to swing between a first position indicated by a virtual line in  FIG. 1  and a second position indicated by a solid line in  FIG. 1 . 
         [0077]    In a state where the first stack lever  41 L and the second stack lever  41 R are disposed at the first position, the presser part  43  is disposed on the lower front side of the first shaft part  45  and the second shaft part  46 . 
         [0078]    In a state where the first stack lever  41 L and the second stack lever  41 R are disposed at the second position, the extending part  42  of each of the first stack lever  41 L and the second stack lever  41 R is disposed to be along the front and rear direction. In this case, the presser part  43  of each of the first stack lever  41 L and the second stack lever  41 R disposed at the second position is disposed on the front side relative to the state where the first stack lever  41 L and the second stack lever  41 R are disposed at the first position. Each of the first stack lever  41 L and the second stack lever  41 R is bent to project toward the lower side, i.e., the paper discharge tray  2 B side. Furthermore, the ribs  44  of the first stack lever  41 L disposed at the second position are formed on a surface of the first stack lever  41 L opposed to a surface of the first stack lever  41 L facing the paper discharge tray  2 B, and are separated toward the front side farther from the passing opening  2 C relative to the guide part  35 . Similarly, the ribs  44  of the second stack lever  41 R disposed at the second position are formed on a surface of the second stack lever  41 R opposed to a surface of the second stack lever  41 R facing the paper discharge tray  2 B, and are separated toward the front side farther from the passing opening  2 C relative to the guide part  35 . 
         [0079]    3. Operation of First Stack Lever and Second Stack Lever 
         [0080]    In a state where no sheet of paper P is discharged to the paper discharge tray  2 B, each of the first stack lever  41 L and the second stack lever  41 R is disposed at the first position by its own weight. 
         [0081]    When the image formation operation is started and the sheet of paper P is stacked on the paper discharge tray  2 B, the upper surface of the sheet of paper P on the paper discharge tray  2 B contacts the presser part  43  of the first stack lever  41 L. Similarly, the upper surface of the sheet of paper P on the paper discharge tray  2 B contacts the presser part  43  of the second stack lever  41 R. 
         [0082]    Then, the sheet of paper P is further stacked on the paper discharge tray  2 B, and the upper surface of the sheet of paper P on the paper discharge tray  2 B pushes up the presser part  43  of the first stack lever  41 L. Similarly, the upper surface of the sheet of paper P on the paper discharge tray  2 B pushes up the presser part  43  of the second stack lever  41 R. As a result, the first stack lever  41 L and the second stack lever  41 R rotate in the clockwise direction about the first shaft part  45  and the second shaft part  46 , respectively, when viewed as a right side view. Then, each of the first stack lever  41 L and the second stack lever  41 R rotates toward the second position. 
         [0083]    Then, the sheets of paper P discharged to the paper discharge tray  2 B are pressed downward by the weights of the first stack lever  41 L and the second stack lever  41 R. 
         [0084]    When the sheets of paper P on the paper discharge tray  2 B are subsequently removed, each of the first stack lever  41 L and the second stack lever  41 R rotates to the first position by its own weight. 
         [0085]    4. Conveying of Sheet of Paper to Re-Conveying Path 
         [0086]    In the following, conveying of the sheet of paper P to the reversing path  12 A in a state where the sheets of paper P are stacked on the paper discharge tray  2 B is explained. 
         [0087]    When the sheet of paper P is to be conveyed to the reversing path  12 A, the flap  31  is disposed at the conveying position. 
         [0088]    Then, the sheet of paper P for which printing has been performed on one side of the sheet of paper P passes through the position between the heat roller  10 A and the presser roller  10 B, and then enters the reversing path  12 A while being guided by the flap  31 . 
         [0089]    Further, the second reversing roller  23  rotates in the third rotational direction, and the second opposing roller  24  rotates following the second reversing roller  23 . Further, the first reversing roller  21  rotates in the first rotational direction, and the first opposing roller  22  rotates following the first reversing roller  21 . 
         [0090]    As a result, the sheet of paper P is conveyed to the upper side. 
         [0091]    Then, the sheet of paper P passes through the passing opening  2 C, is discharged to the guide part  35 , and then is conveyed frontward along the ribs  35 B. With this configuration, the sheet of paper P is conveyed frontward in a state where a contact area of the sheet of paper P to the guide part  35  is reduced. In other words, the sheet of paper P is conveyed frontward in a state where the contact resistance is reduced in comparison with the case where the sheet of paper P contacts the entire upper surface of the flat surface  35 A. 
         [0092]    When the sheet of paper P is conveyed further, the downstream side edge of the sheet of paper P in the conveying direction is disposed on the front side of the rib  35  while crossing over the front edge of the rib  35 B. Further, the upstream side edge of the sheet of paper P in the conveying direction passes through the position between the second reversing roller  23  and the second opposing roller  24 . 
         [0093]    Then, the sheet of paper P is conveyed to the front side along the rib  44  of the first stack lever  41 L and the rib  44  of the second stack lever  41 R. As a result, the sheet of paper P is conveyed to the front side in a state where the contact resistance is reduced in comparison with the case where the sheet of paper P contacts the entire upper surface of the first stack lever  41 L and the entire upper surface of the second stack lever  41 R. 
         [0094]    Specifically, at this time, the sheet of paper P is conveyed along the upper surfaces of the ribs  44  of the first stack lever  41 L and the upper surfaces of the ribs  44  of the second stack lever  41 R. Therefore, the sheet of paper P is smoothly conveyed to cross over the expanded part  43 B toward the front side without causing a state where the downstream side edge of the sheet of paper P in the conveying direction is hooked to the expanded part  43 B of the rib  44  of the first stack lever  41 L and the expanded part  43 B of the rib  44  of the second stack lever  41 R. 
         [0095]    Then, the second reversing roller  23  rotates in the fourth rotational direction, and the second opposing roller  24  rotates following the second reversing roller  23 . Further, the first reversing roller  21  rotates in the second rotational direction, and the first opposing roller  22  rotates following the first reversing roller  21 . Further, the flap  31  is disposed at the discharging position. 
         [0096]    Then, the sheet of paper P is conveyed to the second reversing roller  23  and the second opposing roller  24  by rotations of the first reversing roller  21  and the first opposing roller  22 . 
         [0097]    Specifically, the sheet of paper P is conveyed rearward to the guide part  35  along the rib  44  of the first stack lever  41 L and the rib  44  of the second stack lever  41 R. 
         [0098]    Thereafter, the sheet of paper P is conveyed rearward to the passing opening  2 C along the rib  35 B of the guide part  35 . The sheet of paper P which has passed through the passing opening  2 C is conveyed to the second reversing roller  23  and the second opposing roller  24  while passing through the first reversing roller  21  and the first opposing roller  22 . 
         [0099]    Then, the sheet of paper P is conveyed downward by rotations of the second reversing roller  23  and the second opposing roller  24 . 
         [0100]    Then, the sheet of paper P enters the relay path  12 B. 
         [0101]    The sheet of paper P which has entered the relay path  12 B is supplied to a midway point on the supply path  4 A while passing through the relay path  12 B, and is guided to the image forming unit  3 . 
         [0102]    5. Advantageous Effects 
         [0000]    (1) As shown in  FIG. 1 , the image forming apparatus  1  includes the first stack lever  41 L and the second stack lever  41 R. Further, each of the first stack lever  41 L and the second stack lever  41 R is disposed at the first position by its own weight when no sheet of paper P is discharged to the paper discharge tray  2 B. When the sheet of paper P is discharged to the paper discharge tray  2 B and is stacked on the paper discharge tray  2 B, each of the first stack lever  41 L and the second stack lever  41 R is moves from the first position to the second position in a manner of being pushed up by the sheet of paper P, and presses the sheet of paper P by the presser part  43 . Furthermore, the ribs  44  are formed on the surface of the first stack lever  41 L opposing the surface of the first stack lever  41 L facing the paper discharge tray  2 B, and similarly the ribs  44  are formed on the surface of the second stack lever  41 R opposing the surface the second stack lever  41 R facing the paper discharge tray  2 B. 
         [0103]    Therefore, it becomes possible to convey the sheet of paper P passing through the reversing path  12 A and the passing opening  2 C to be along the ribs  44  of the first stack lever  41 L and the ribs  44  of the second stack lever  41 R while making it possible to press the sheets of paper P stacked on the paper discharge tray  2 B by the first stack lever  41 L and the second stack lever  41 R. 
         [0104]    As a result, it becomes possible to decrease the contact area of the sheet of paper P in comparison with the case where the sheet of paper P being re-conveyed contacts a surface. That is, it is possible to suppress increase of the conveying resistance of the sheet of paper P in comparison with the case where the sheet of paper P being re-conveyed contacts a surface. 
         [0105]    Accordingly, the sheet of paper P can be re-conveyed smoothly. 
         [0106]    When the sheet of paper P for which printing has been performed for the both sides thereof is discharged while the sheet of paper P for which printing has been performed only for one side thereof is re-conveyed, the discharged sheets of paper P are stacked on the paper discharge tray  2 B such that the discharged sheets of paper P push up the first stack lever  41 L and the second stack lever  41 R while the sheet of paper P being re-conveyed moves along the ribs  44  of the first stack lever  41 L and the ribs  44  of the second stack lever  41 R. 
         [0107]    Therefore, it becomes possible to prevent the sheet of paper P stacked on the paper discharge tray  2 B and the sheet of paper P being re-conveyed from contacting with each other. 
         [0108]    (2) As shown in  FIG. 1 , the image forming apparatus  1  includes the first reversing roller  21  and the second reversing roller  23 . 
         [0109]    Therefore, by rotating the first reversing roller  21  in the second rotational direction after rotating the first reversing roller  21  in the first rotational direction and by rotating the second reversing roller  23  in the fourth rotational direction after rotating the second reversing roller  23  in the third rotational direction, it is possible to convey the sheet of paper P in a direction departing from the passing opening  2 C after conveying the sheet of paper P toward the passing opening  2 C. 
         [0110]    Accordingly, it is possible to re-convey the sheet of paper P by switching the rotational direction of the first reversing roller  21  and the second reversing roller  23 . 
         [0111]    (3) As shown in  FIG. 1 , in the image forming apparatus  1 , each of the first stack lever  41 L and the second stack lever  41 R is bent such that each of the first stack lever  41 L and the second stack lever  41 R projects toward the lower side, i.e., toward the paper discharge tray  2 B side. 
         [0112]    Therefore, it is possible to securely press the sheets of paper P discharged to the paper discharge tray  2 B. 
         [0113]    (4) As shown in  FIG. 4 , in the image forming apparatus  1 , the rib  44  of each of the first stack lever  41 L and the second stack lever  41 R extends linearly between the rear end part of the extending part  42  and the front end part of the presser part  43 . 
         [0114]    Accordingly, it is possible to smoothly convey the sheet of paper P along the ribs  44 . 
         [0115]    (5) As shown in  FIG. 1 , in the image forming apparatus  1 , the passing opening  2 C is disposed on the rear side of the paper discharge opening  2 A. 
         [0116]    Therefore, in the case where the sheet of paper P which has passed though the passing opening  2 C is conveyed toward the paper discharge tray  2 B, the sheet of paper P being conveyed does not contact the sheet of paper P stacked on the paper discharge tray  2 B while the sheet of paper P is conveyed from the passing opening  2 C to the position close to the paper discharge opening  2 A. 
         [0117]    Therefore, it is possible to prevent the sheet of paper P being re-conveyed and the sheet of paper P stacked on the paper discharge tray  2 B from contacting with each other. 
         [0118]    As a result, it becomes possible to re-convey the sheet of paper P more smoothly. 
         [0119]    (6) As shown in  FIG. 1 , in the image forming apparatus  1 , the guide part  35  is disposed between the passing opening  2 C and the paper discharge tray  2 B in the up and down direction, and forms the lower periphery of the passing opening  2 C. 
         [0120]    Therefore, it is possible to convey the sheet of paper P passing through the reversing path  12 A and the passing opening  2 C to be along the guide part  35 . 
         [0121]    As a result, it becomes possible to more suitably prevent the conveying speed of the sheet of paper P passing through the reversing path  12 A and the passing opening  2 C from decreasing. 
         [0122]    (7) As shown in  FIG. 1 , in the image forming apparatus  1 , the guide part  35  is disposed on the upper side of the first shaft part  45  and the second shaft part  46  of the first stack lever  41 L and the first shaft part  45  and the second shaft part  41 R of the second stack lever  41 R. 
         [0123]    Therefore, it is possible to smoothly convey the sheet of paper P to be along the ribs  44  of the first stack lever  41 L and the ribs  44  of the second stack lever  41 R. 
         [0124]    (8) As shown in  FIG. 1 , in the image forming apparatus  1 , the guide part  35  is the upper surface of the housing  2 , and the paper discharge tray  2 B is formed to be recessed downward from the upper surface of the housing  2 . 
         [0125]    Therefore, the number of components in the image forming apparatus  1  is reduced. 
         [0126]    (9) As shown in  FIG. 1 , in the image forming apparatus  1 , the guide part  35  includes the ribs  44  configured to reduce the contact resistance with respect to the sheet of paper P. 
         [0127]    In this case, the sheet of paper P being conveyed contacts the ribs  44 . 
         [0128]    Therefore, the sheet of paper P can be smoothly re-conveyed. 
         [0129]    Furthermore, the guide part  35  can be formed easily. 
         [0130]    (10) As shown in  FIG. 4 , in the image forming apparatus  1 , the ribs  44  are arranged at constant intervals in the left and right direction. 
         [0131]    Therefore, it is possible to let the sheet of paper P contact the ribs  44 . 
         [0132]    As a result, it becomes possible to suppress decreasing of the conveying speed of the sheet of paper P. 
         [0133]    (11) As shown in  FIG. 1 , in the image forming apparatus  1 , the ribs  44  are disposed on the front side of the guide part  35  when the first stack lever  41 L and the second stack lever  41 R are disposed at the second position. 
         [0134]    Therefore, the sheet of paper P conveyed along the guide part  35  by passing through the passing opening  2 C is conveyed along the ribs  44  after being conveyed along the guide part  35 . 
         [0135]    Therefore, the sheet of paper P can be conveyed smoothly. 
         [0136]    (12) As shown in  FIG. 1 , the image forming apparatus  1  includes the supply path  4 A, the paper discharge path  5 A, the reversing path  12 A and the relay path  12 B. 
         [0137]    Therefore, it is possible to convey the sheet of paper P which has passed through the fixing unit  10  toward the image forming unit  3  again, by conveying the sheet of paper P in a direction of moving away from the passing opening  2 C after letting the sheet of paper P enter the reversing path  12 A, and then conveying the sheet of paper P on the relay path  12 B and letting the sheet of paper P enter the supply path  4 A. Then, an image can be formed, by the image forming unit  3 , on a side of the sheet of paper P on which an image has not been formed. 
         [0138]    (13) As shown in  FIG. 1 , the image forming apparatus  1  includes the flap  31  which is able to move between the first guide position and the second guide position. 
         [0139]    Therefore, it is possible to securely guide the sheet of paper P to the paper discharge path  5 A or the reversing path  12 A. 
       Second Embodiment 
       [0140]    Hereafter, an image forming apparatus  50  according to a second embodiment is explained. In the following explanation, to elements which are similar to those of the first embodiment, similar reference numbers are assigned, and explanations thereof will not be repeated. 
         [0141]    In the above described first embodiment, the ribs  35 B are formed to extend from the passing opening  2 C to the front edge of the guide part  35 . 
         [0142]    By contrast, according to the second embodiment, as shown in  FIGS. 5 and 6 , ribs  55   c  are formed on the front side of the passing opening  2 C to be spaced from the passing opening  2 C. 
         [0143]    Specifically, according to the second embodiment, the image forming apparatus  1  includes a guide part  55  in place of the guide part  35 . 
         [0144]    The guide part  55  is formed in a rear end part on the upper surface of the housing  2  and in a central part in the left and right direction. The guide part  55  includes a flat part  55 A, an inclined part  55 B, and the plurality of ribs  55 C. 
         [0145]    The flat surface  55 A is formed to extend in the horizontal direction. As shown in  FIG. 6 , a rear edge  55 D of the flat surface  55 A forms a lower periphery of the passing opening  2 C, and extends in the left and right direction. 
         [0146]    As shown in  FIGS. 5 and 6 , the inclined surface  55 B is formed to extend to the lower front side to be continued from the flat surface  55 A. A front edge  55 E of the inclined surface  55 B extends in the left and right direction to be along the paper discharge opening  2 A. A rear edge  55 F of the inclined surface  55 B extends in the left and right direction in parallel with the front edge  55 E, and is disposed on the upper rear side of the front edge  55 E. 
         [0147]    The rib  55 C projects upward from the inclined surface  55 B. The rib  55 C extends in the front and rear direction. The front edge of the rib  55 C coincides with the front edge  55 E of the inclined surface  55 B and a rear edge of the rib  55 C coincides with the rear edge  55 F of the inclined surface  55 B. That is, the rib  55 C is disposed to extend between the front edge  55 E of the inclined surface  55 B and the rear edge  55 F of the inclined surface  55 B. The rib  55 C is disposed in the front end part of the guide part  55 . The rib  55 C is disposed on the front side of the passing opening  2 C across the flat surface  55 A, and is spaced from the passing opening  2 C. 
         [0148]    The sheet of paper P being conveyed frontward by passing through the passing opening  2 C is conveyed frontward along the ribs  55 C, and is conveyed along the ribs  44  of the first stack lever  41 L and the ribs  44  of the second stack lever  41 L. 
         [0149]    According to the image forming apparatus  50  of the second embodiment, the same advantageous effects as those attained by the first embodiment can be attained. 
         [0150]    Furthermore, according to the image forming apparatus of the second embodiment, as shown in  FIGS. 5 and 6 , the ribs  55 C are disposed on the inclined surface  55 B. Further, the front edge of the rib  55 C coincides with the front edge  55 E of the inclined surface  55 B. 
         [0151]    In this configuration, the sheet of paper P which has passes through the passing opening  2 C hangs downward such that the front edge of the sheet of paper P contacts the first stack lever  41 L and the second stack lever  41 R. Then, the sheet of paper P contacts the front edge  55 E of the inclined surface  5 B. 
         [0152]    Therefore, the ribs  55 C are disposed at positions which the sheet of paper P likely contacts when the sheet of paper P disposed on the top surface of the paper discharge tray  2 B is re-conveyed. 
         [0153]    Therefore, it becomes possible to cause the sheet of paper P being re-conveyed to contact the ribs  55 C effectively. 
         [0154]    As a result, it becomes possible to more smoothly re-convey the sheet of paper P.