Patent Publication Number: US-7587155-B2

Title: Process cartridge and image forming apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application claims priority benefits on the basis of Japanese Patent Application No. 2006-85924 filed on Mar. 27, 2006 and Japanese Patent Application No. 2007-11596 filed on Jan. 22, 2007, the disclosures of which are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field 
   Aspects of the present invention relates to an image forming apparatus such as a laser printer ,and a process cartridge which is detachably mountable to the image forming apparatus. 
   2. Description of the Related Art 
   As a process cartridge of a laser printer, there has been proposed a developing apparatus in which a toner unit accommodating a toner is detachably attached to a developing unit of the process cartridge. 
   In some developing apparatus, a toner box is detachably attached to the case of the developing apparatus. Slip-off prevention guide grooves are formed in the both right and left side walls of the case of the developing apparatus. A lever is pivotably disposed at the spindle that protrudes transversely from the both right and left sides of the toner box and rotates the rotary vane stirring the toner in the toner box, and an engaging projection is disposed at the substrate of the lever through which the spindle is inserted. In the developing apparatus, by simple operations of attaching the toner box to the case of the developing apparatus and pivoting the lever about the spindle to fit the engaging projection into the slip-off prevention guide groove, the lever and the toner box can be prevented from coming off from the case of the developing apparatus and the toner box is fixed to the developing apparatus. 
   In the developing apparatus, only one engaging projection is disposed at each of the left and right sides of the toner box, and only one slip-off prevention guide groove is disposed at each of the left and right side walls of the case of the developing apparatus. In other words, in the rotation direction of the rotary vane, the toner box is fixed to the developing apparatus at only one position where the engaging projection engages with the slip-off prevention guide groove. 
   When rotational moment is generated along with the rotation of the rotary vane, the fitting status of the engaging projection in the slip-off prevention guide groove may become unstable under the influence of the rotational moment. In this case, it becomes difficult to fix the toner box stably to the developing apparatus and a gap may be generateds between the toner box and the developing apparatus, which may cause a toner leakage. 
   SUMMARY 
   One aspect of the present invention may provide a process cartridge which can fix the toner unit with stability to the developing unit while maintaining a simple operability, and an image forming apparatus which the process cartridge is detachably mountable to. 
   The same or different aspect of the present invention may provide a process cartridge including a developing unit having a developing roller and being detachably mountable to an image forming apparatus main body, and a toner unit accommodating a toner and being detachably mountable to the developing unit, wherein the developing unit includes a developer casing provided with an accommodating section for accommodating the toner unit and formed with a first opening for receiving a toner from the toner unit, the toner unit includes a toner casing for accommodating the toner, and an agitating member provided in the toner casing for agitating the toner in the toner casing by rotation, the developer casing includes a first fixing member for fixing the toner unit to the accommodating section, and a second fixing member disposed at the opposite side of the first fixing member in relation to the accommodating section and for fixing the toner unit to the accommodating section, and the toner casing is formed with a second opening opposed to the first opening and supplying the toner to the first opening when the toner unit is attached to the developing unit and the second opening is located at a downstream side of the agitating member in an attaching direction of the toner unit to the developing unit, and includes: a grasp portion disposed at the opposite side of the second opening in relation to a rotation shaft of the agitating member; a first fixed portion disposed between the second opening and the grasp portion in a rotation direction of the agitating member and received by and fixed to the first fixing member when the toner unit is attached to the developing unit; and a second fixed portion disposed at the opposite side of the first fixed portion in relation to the rotation shaft of the agitating member and fixed to the second fixing member when the toner unit is attached to the developing unit. 
   One or more aspects of the present invention provide an image forming apparatus including a developing unit having a developing roller, and a toner unit accommodating a toner and being detachably mountable to the developing unit, wherein the developing unit includes a developer casing provided with an accommodating section for accommodating the toner unit and formed with a first opening for receiving a toner from the toner unit, the toner unit includes a toner casing for accommodating the toner, and an agitating member provided in the toner casing for agitating the toner in the toner casing by rotation, the developer casing includes a first fixing member for fixing the toner unit to the accommodating section, and a second fixing member disposed at the opposite side of the first fixing member in relation to the accommodating section and for fixing the toner unit to the accommodating section, and the toner casing is formed with a second opening opposed to the first opening and supplying the toner to the first opening when the toner unit is attached to the developing unit and the second opening is located at a downstream side of the agitating member in an attaching direction of the toner unit to the developing unit, and includes: a grasp portion disposed at the opposite side of the second opening in relation to a rotation shaft of the agitating member; a first fixed portion disposed between the second opening and the grasp portion in a rotation direction of the agitating member and received by and fixed to the first fixing member when the toner unit is attached to the developing unit; and a second fixed portion disposed at the opposite side of the first fixed portion in relation to the rotation shaft of the agitating member and fixed to the second fixing member when the toner unit is attached to the developing unit. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a sectional side view showing an embodiment of a laser printer as an example of an image forming apparatus of one or more aspects of the present invention. 
       FIG. 2  is a right perspective view of a process unit in a laser printer shown in  FIG. 1  as viewed from above the front side. 
       FIG. 3  is a left sectional side view of a process unit in  FIG. 2 . 
       FIGS. 4(   a ) and  4 ( b ) show aspects where a toner box has been detached in  FIG. 2 , and  FIG. 4(   a ) shows an open/close lever being at a lever opening position to open a toner guiding port, and  FIG. 4(   b ) shows the open/close lever being at a lever closing position to close the toner guiding port. 
       FIGS. 5(   a ),  5 ( b ), and  5 ( c ) are left perspective views of a toner box in the process unit shown in  FIG. 2  as viewed from above the rear side,  FIG. 5(   a ) shows an aspect where a toner ejecting port is opened,  FIG. 5(   b ) shows an aspect where the toner ejecting port is closed, and  FIG. 5(   c ) shows an inner casing in the toner box. 
       FIG. 6  shows an aspect where the toner box has been detached and the open/close lever is at the lever closing position in  FIG. 2 , together with the toner box detached therefrom. 
       FIG. 7  shows an aspect where the open/close lever is at the lever closing position in  FIG. 2 . 
       FIG. 8  is a left sectional side view of the process unit in  FIG. 6 . 
       FIG. 9  is a left sectional side view of the process unit in  FIG. 7 . 
       FIG. 10(   a ) is a left perspective view of a toner box to which a third embodiment is applied as viewed from above the rear side, and  FIG. 10(   b ) is a left side view of the toner box in  FIG. 10(   a ) placed on a placement surface. 
   

   DETAILED DESCRIPTION OF THE EMBODIMENTS 
   Details of embodiments of one or more aspects of the present invention will be described hereinafter with reference to the drawings. 
   First Embodiment 
   1. Overall Configuration of Laser Printer 
     FIG. 1  is a sectional side view showing an embodiment of a laser printer as an example of an image forming apparatus of one or more aspects of the present invention. 
   The laser printer  1  includes a main body casing  2  as an example of image forming apparatus main body, a sheet feeding section  4  accommodated in the main body casing  2  for feeding a sheet  3 , and an image forming section  5  for forming an image on the fed sheet  3 , as shown in  FIG. 1 . 
   (1) Main Body Casing 
   On one side wall of the main body casing  2 , a mounting port  6  is formed for detachably attaching a later described process unit  20  as an example of process cartridge, and a front cover  7  is provided for opening and closing the mounting port  6 . The front cover  7  is pivotably supported by a cover shaft  8  which is inserted through the lower end portion thereof. Accordingly, when the front cover  7  is opened with the cover shaft  8  as a supporting point, the mounting port  6  is opened and the process unit  20  can be attached and detached via the mounting port  6  to and from the main body casing  2 , while the front cover  7  is closed with the cover shaft  8  as a supporting point, the front cover  7  closes the mounting port  6 . 
   In the following description, the side on which the front cover  7  is provided in a state where the process unit  20  is attached in the main body casing  2  will be described as a “front side” (front surface side), and the opposing side thereof will be described as a “rear side” (back surface side). The sheet thickness direction toward the near side in  FIG. 1  will be described as a “left side” and the sheet thickness direction toward the far side in  FIG. 1  will be described as a “right side”. In some cases, the left and right direction may be referred to as a “width direction”. 
   (2) Sheet Feeding Section 
   The sheet feeding section  4  is disposed at the bottom in the main body casing  2  and includes a sheet feeding tray  9 , a separation roller  10 , a separation pad  11 , a sheet feeding roller  12 , a sheet dust removing roller  13 , a pinch roller  14 , and a resist roller  15 . 
   The sheet feeding tray  9  includes a sheet pressing plate  16  therein and a lever  17  in the front end portion thereof. The lever  17  lifts up the front end portion of the sheet pressing plate  16 . 
   The sheets  3 , which are placed on the sheet pressing plate  16 , are transported to a separation position between the separation roller  10  and the separation pad  11  by the rotation of the sheet feeding roller  12  and separated one by one at the separation position, and then each sheet  3  passes a space between the sheet dust removing roller  13  and the pinch roller  14 , and is transported toward the resist roller  15 . 
   The sheet  3  transported to the resist roller  15  is then transported to a transfer position between a transfer roller  31  and a photosensitive drum  28  which will be described later. 
   (3) Image Forming Section 
   The image forming section  5  includes a scanning section  19 , a process unit  20  and a fixing section  21 . 
   (a) Scanning Section 
   The scanning section  19  is provided at an upper portion in the main body casing  2 , and includes a laser beam source (not shown), a rotatably driven polygonal mirror  22 , an fθ lens  23 , a reflecting mirror  24 , a lens  25  and a reflecting mirror  26 . The laser beam source emits laser beams based upon image data. The beams are deflected at the polygonal mirror  22  and pass the fθ lens  23 , as indicated by a chain line. The beam passage is then reflected by the reflecting mirror  24 , the beams pass the lens  25 , and further reflected downward by the reflecting mirror  26  to be irradiated on the surface of the photosensitive drum  28  in the process unit  20 . 
   (b) Process Unit 
     FIG. 2  is a right perspective view of a process unit in the laser printer shown in  FIG. 1  as viewed from above the front side, and  FIG. 3  is a left sectional side view of the process unit in  FIG. 2 . 
     FIG. 4(   a ) shows an aspect in which a toner box is detached, an open/close lever is at a lever opening position and a toner guiding port is opened, and  FIG. 4(   b ) shows an aspect in which the open/close lever is at a lever closing position and the toner guiding port is closed in  FIG. 4(   a ). 
     FIG. 5(   a ) is a left perspective view of a toner box in the process unit shown in  FIG. 2  as viewed from above the rear side, and shows an aspect where a toner ejecting port is opened;  FIG. 5(   b ) shows an aspect where the toner ejecting port is closed; and  FIG. 5(   c ) is a left perspective view of an inner casing in the toner box shown in  FIG. 5(   a ) as viewed from above the rear side. 
     FIG. 6  shows an aspect in which the toner box is detached and the open/close lever is at the lever closing position in  FIG. 2 , together with the toner box detached therefrom, while  FIG. 7  shows an aspect in which the open/close lever is at the lever closing position in  FIG. 2 . 
     FIG. 8  is a left sectional side view of the process unit in  FIG. 6 , while  FIG. 9  is a left sectional side view of the process unit in  FIG. 7 . 
   The process unit  20  is provided at a lower portion of the scanning section  19  in the main body casing  2  and is detachably mountable to the main body casing  2  via the mounting port  6 , as shown in  FIG. 1 . The attaching and detaching directions of the process unit  20  to and from the main body casing  2  are an obliquely downwardly rearward direction (attaching direction) and an obliquely upwardly forward direction (detaching direction), respectively, as indicated by arrows in the drawing. 
   The process unit  20  integrally includes a drum section  27  which forms the rear half portion of the process unit  20 , and a developing section  30  which forms the front half portion of the process unit  20  and serves as an example of developing unit, and further includes a toner box  40  which is detachably attached to the developing section  30  of the process unit  20  and serves as an example of toner unit, as shown in  FIG. 3 . 
   (b-1) Drum Section 
   The drum section  27  includes a drum casing  76 , and includes the photosensitive drum  28 , a scorotron charger  29 , a transfer roller  31  and a cleaning blush  32  which are provided in the drum casing  76 . 
   The drum casing  76  is in a box shape which is longitudinal in width direction and whose front portion is opened, and integrally includes a drum rear wall  77 , a drum right wall  79  (see  FIG. 2 ), a drum left wall  80  (see  FIG. 2 ), a drum top wall  81 , and a drum bottom wall  82 . 
   The drum right wall  79  and the drum left wall  80  are disposed in an opposed spaced relation with each other in the width direction as shown in  FIG. 2 . 
   The drum bottom wall  82  is extended between the lower end edges of the drum right wall  79  and the drum left wall  80 . The drum top wall  81  is extended between the upper end edges of the drum right wall  79  and the drum left wall  80 . The drum rear wall  77  is extended between the rear end edges of the drum right wall  79  and the drum left wall  80 , as shown in  FIG. 3 . 
   Midway in an anteroposterior direction of the drum top wall  81 , a laser entrance port  78  is formed for the irradiation of the laser beams from the scanning section  19  to the photosensitive drum  28 . A first passing port  84  is opened between the front end edge of the drum bottom wall  82  and the rear end edge of a developer rear bottom wall  68  of the developing section  30 , which will be described later. Midway in a vertical direction of the drum rear wall  77 , a second passing port  85  is opened. Both of the first passing port  84  and the second passing port  85  are formed in a longitudinal rectangular shape in the width direction. 
   In this drum casing  76 , the space defined by the drum rear wall  77 , and, the rear half portions of the drum right wall  79 , the drum left wall  80  and the drum bottom wall  82 , and the drum top wall  81 , forms a drum accommodation section  83  which accommodates the photosensitive drum  28 , the scorotron charger  29 , the transfer roller  31  and the cleaning blush  32 . The drum accommodation section  83  is formed in a cylindrical shape whose front side and rear side are opened. 
   On the other hand, the space defined by the front half portions of the drum right wall  79 , the drum left wall  80 , and the drum bottom wall  82  forms a developer arrangement section  86  where the developing section  30  is arranged. The developer arrangement section  86  is formed as a bottomed frame in a flat-bottomed U-shape, shaped as viewed in front cross section, whose upper side is opened. 
   The drum accommodation section  83  and the developer arrangement section  86  communicate with each other. 
   The photosensitive drum  28  is in a cylindrical shape and includes a drum body  33  whose outermost layer is formed by a positively chargeable photosensitive layer formed of polycarbonate or the like, and a metal drum shaft  34  extending through the shaft center of the drum body  33  along an axial direction of the drum body  33 . Both end portions of the drum shaft  34  in an axial direction are supported between the drum right wall  79  and the drum left wall  80  of the drum casing  76  (see  FIG. 2 ). The drum body  33  is rotatably supported with respect to the drum shaft  34 , and as a result, the photosensitive drum  28  is rotatable about the drum shaft  34  in the drum casing  76 . A driving force from a motor (not shown) rotationally drives the photosensitive drum  28 . 
   The scorotron charger  29  is supported on the drum top wall  81  of the drum casing  76  at the position obliquely rearward above the photosensitive drum  28  and disposed in opposed spaced relation with the photosensitive drum  28  so as not to contact to the photosensitive drum  28 . This scorotron charger  29  includes a discharge wire  35  which is disposed in an opposed spaced relation with the photosensitive drum  28 , and a grid  36  which is provided between the discharge wire  35  and the photosensitive drum  28  for controlling the amount of the charge from the discharge wire  35  to the photosensitive drum  28 . 
   In this scorotron charger  29 , a bias voltage is applied to the grid  36  and at the same time a high voltage is applied to the discharge wire  35  to generate corona discharge, thereby positively charging the surface of the photosensitive drum  28  uniformly. 
   The transfer roller  31  is provided below the photosensitive drum  28  in the drum casing  76 , opposingly contacts with the photosensitive drum  28  in the vertical direction so as to form a nip between itself and the photosensitive drum  28 , and the nip serves as the above described transfer position between the photosensitive drum  28  and the transfer roller  31 . 
   In addition, the transfer roller  31  includes a metal roller shaft which is rotatably supported between the drum right wall  79  and the drum left wall  80  of the drum casing  76 , and a rubber roller which is formed of a conductive rubber material and covers the roller shaft. The transfer roller  31  is applied with a transfer bias at the time of transfer. A driving force from a motor (not shown) rotationally drives the transfer roller  31 . 
   The cleaning blush  32  is assembled onto the drum rear wall  77  of the drum casing  76  and disposed so as to opposingly contact with the photosensitive drum  28  at the position obliquely rearward above the photosensitive drum  28  and obliquely rearward below the scorotron charger  29  (upstream side of the scorotron charger  29  in a rotational direction of the photosensitive drum  28  (see the arrow in  FIG. 3 )). 
   (b-2) Developing Section 
   The developing section  30  is integrally formed with the drum section  27  in the developer arrangement section  86  of the drum casing  76 . 
   This developing section  30  includes a developer casing  62 , a feed roller  101 , and a developing roller  104  and a layer-thickness regulating blade  107  provided in the developer casing  62 . 
   The developer casing  62  integrally includes a box-shaped rear-side casing  38  which is longitudinal in the width direction and whose rear side is opened, and a front-side casing  39  whose upper side and front side are opened and which has a width greater than the rear-side casing  38 . 
   The rear-side casing  38  integrally includes a developer front wall  64 , a developer right wall  65  (see  FIG. 2 ), a developer left wall  66  (see  FIG. 2 ), a developer top wall  67 , and the developer rear bottom wall  68 . 
   The developer right wall  65  and the developer left wall  66  are in a generally rectangular shape as viewed from side and disposed in an opposed spaced relation with each other in the width direction. 
   The developer rear bottom wall  68  is extended between the lower end edges of the developer right wall  65  and the developer left wall  66 , and integrally includes a first bottom wall  73  and a second bottom wall  74  in this sequence from the rear in the anteroposterior direction. 
   The first bottom wall  73  is disposed on the rear side of the developer rear bottom wall  68 , and formed in a tongue plate shape tilting downward from the front side toward the rear side. 
   The second bottom wall  74  is formed in generally semi-circular shape as viewed in side section and extends continuously from the front end edge of the first bottom wall  73  along the feed roller  101 . 
   The developer top wall  67  is extended between the upper end edges of the developer right wall  65  and the developer left wall  66  and integrally includes a first top wall  115  and a second top wall  116 . 
   The first top wall  115  is disposed in front of the developer top wall  67  and extends toward the obliquely upwardly forward. 
   The second top wall  116  is formed in generally reversed L-shape as viewed in left side section which extends downward from the rear end edge of the first top wall  115  and then bents to extend backward. 
   The developer front wall  64  is extended between the front end edges of the developer right wall  65  and the developer left wall  66 . The developer front wall  64  has an upper end edge connected to the above described bending portion of the second top wall  116  and a lower end edge connected to the front end edge of the second bottom wall  74 , and integrally includes a longitudinal wall  120  which extends upward from the front end edge of the second bottom wall  74  and a bending wall  121  which is bent backward from the upper end edge of the longitudinal wall  120 , then bent again and extends upward to be connected to the bending portion of the second top wall  116 , and is formed in generally L-shape as viewed in left side section. 
   Front end edges of the developer top wall  67 , the developer left wall  65 , the developer right wall  66  and the developer rear bottom wall  68  define an insertion hole  87  which is opened on the rear side of the rear-side casing  38 . The insertion hole  87  is formed in a rectangular shape longitudinal in the width direction. 
   In the rear-side casing  38 , the space defined by the developer front wall  64 , the developer right wall  65 , the developer left wall  66 , the developer top wall  67 , and the developer rear bottom wall  68  serves as a developing chamber  72  which accommodates the feed roller  101 , the developing roller  104  and the layer-thickness regulating blade  107 . 
   The front-side casing  39  is integrally formed with a right wall  69  (see  FIG. 2 ) and a left wall  70  (see  FIG. 2 ) and a developer front bottom wall  75 . 
   The developer front bottom wall  75  is formed in generally C-shape as viewed in side section and integrally includes a curved wall  122  which forms the rear half portion thereof and a L-shaped wall  123  which forms the front half portion thereof. 
   The curved wall  122  is formed in generally minor arc as viewed in side section and the front end edge thereof is connected to the rear end edge of the L-shaped wall  123 . 
   The L-shaped wall  123  is formed in generally L-shape as viewed in side section which extends forward from the rear end edge thereof and is bent to extend upward. In the laterally central portion of the front end portion and the upper end portion of the L-shaped wall  123 , an engagement portion  124  is integrally formed. The engagement portion  124  is an example of second fixing member and in a hook shape as viewed in side section which is bent at the upper end edge thereof and extends slightly forward. The engagement portion  124  is formed with a developer-side first surface  142  as an example of first-direction fixing portion and a developer-side second surface  143  as an example of second-direction fixing portion. The developer-side first surface  142  is a front end face of the engagement portion  124  and extends generally in an up-and-down direction. The developer-side second surface  143  extends rearward from the lower end edge of the developer-side first surface  142  (see the enlarged drawing of  FIG. 3 ). 
   As shown in  FIG. 6 , in the front end portion of the L-shaped wall  123 , a positioning groove  138  which is concaved downward from the upper end edge of the front end portion of the L-shaped wall  123 , is formed at each position outwardly from the center of the width direction spaced by a distance equivalent to approximately the one-quarter of the width size of the L-shaped wall  123 . 
   The right wall  69  and the left wall  70  are disposed in opposed relation with each other in the width direction so as to sandwich the developer front bottom wall  75  therebetween and are formed in generally rectangular shape as viewed from side, as shown in  FIG. 2 . The obliquely upper front portion of the right wall  69  is cut out for ease of description in  FIG. 2 . 
   In the right wall  69  and the left wall  70 , first insertion holes  97  which extend through the right wall  69  and the left wall  70  in the width direction are formed, respectively, at generally central positions thereof in the front-and-rear and up-and-down directions. The right wall  69  and the left wall  70  integrally include square columns  89  in the respective rear end portions of the laterally inner surfaces thereof, as shown in  FIG. 4(   a ). 
   The square column  89  is formed in generally rectangular parallelepiped shape which is longitudinal in the vertical direction, and a guide groove  119  is formed as an example of first fixing member in the upper end portion of the square column  89  with the front end surface thereof being concaved toward the rear side. The square column  89  integrally includes a rib  90  on the laterally internal surface thereof below the guide groove  119 . The rib  90  is formed to extend toward the laterally inner side so that the side section thereof forms generally a minor arc, and disposed so as to curve generally along the curved wall  122  of the developer front bottom wall  75  and to be in slightly spaced relation in the radial direction with respect to the curved wall  122 , as shown in  FIG. 8 . 
   In this front-side casing  39 , the portion defined by the right wall  69 , the left wall  70 , and the developer front bottom wall  75  forms a toner box accommodation chamber  71  as an example of accommodating section which accommodates the toner box  40 . The toner box accommodation chamber  71  is formed in a bottomed frame with the upper side and the front side thereof being opened. The above-mentioned engagement portion  124  is disposed at the opposite side of the guide groove  119  with respect to the toner box accommodation chamber  71 . 
   The rear-side casing  38  and the front-side casing  39  are connected through the front side surface of the longitudinal wall  120  of the developer front wall  64  and the rear side surface of the curved wall  122  of the developer front bottom wall  75 . A toner guiding port  88  as an example of first opening, which extends through the longitudinal wall  120  and the curved wall  122  in the thickness direction, is formed at the laterally central position of the connecting portion of the longitudinal wall  120  and the curved wall  122 . The toner guiding port  88  is in a rectangular shape longitudinal in the width direction, and the toner guiding port  88  communicates the toner box accommodation chamber  71  and the developing chamber  72 . 
   The toner box accommodation chamber  71  includes a shutter  111  and a open/close lever  113 . 
   The shutter  111  is a thin plate formed as a minor arc having a circumference slightly shorter than the curved wall  122  as viewed in section, as shown in  FIG. 3 . A penetration hole  112 , which is in a rectangular shape as viewed from front and extends through the shutter  111  in the thickness direction as shown in  FIG. 4(   b ), is formed at laterally center position of upper-half portion of the shutter  111 . In each of the upper end portions and the lower end portions of both lateral end portions of the shutter  111 , a notched portion  136  which is cut out in generally L-shape as viewed from front, is formed. In the upper end portions of the shutter  111  laterally inward from the respective notched portions  136 , engagement portions  139  are provided respectively. The engagement portions  139  are engaged by respective second radial projections  57  of the toner box  40  when the toner box  40  is in the attached state in the process unit  20 . 
   In the toner box accommodation chamber  71 , the both lateral end portions of the shutter  111  are interposed between the curved wall  122  and the rib  90  of the square column  89 , and thus the shutter  111  is pivotably supported along the side-sectional shape of the rib  90 , as shown in  FIG. 8   
   The shutter  111  can move between a developer closing position (see  FIG. 8 ) which closes the toner guiding port  88  at a portion where the penetration hole  112  is not formed, and a developer opening position (see  FIG. 3 ) where the penetration hole  112  and the toner guiding port  88  are disposed in opposed relation to allow the toner guiding port  88  to be released forward. 
   A seal member  125  is interposed between the curved wall  122  and the shutter  111 . The seal member  125  is formed in a sheet shape, for example, of felt and the like and attached on the front side surface of the curved wall  122  so as not to block the toner guiding port  88 . 
   The open/close lever  113  is formed in generally U-shape as viewed from top as shown in  FIG. 4(   a ) and integrally includes a right support portion  108 , a left support portion  109 , and a process grasp portion  110 . 
   The right support portion  108  and the left support portion  109  are formed in generally P-shaped thin plate as viewed from right side. In generally central position of the rear half portions of the right support portion  108  and the left support portion  109 , round holes  114  are formed respectively and penetrate the right support portion  108  and the left support portion  109  in the thickness direction. 
   In each of the laterally outside surface of the right support portion  108  and the left support portion  109 , a support cylinder  135  is provided in a position corresponding to the round hole  114 . The support cylinder  135  has an inner diameter identical to the diameter of the round hole  114  and extends outwardly in the width direction. The support cylinder  135  has an outer diameter slightly smaller than the inner diameters of the first insertion holes  97  of the right wall  69  and the left wall  70  described above. 
   In the upper portion of the round holes  114  in the right support portion  108  and the left support portion  109 , receiving portions  117  are formed respectively. Each of the receiving portions  117  has an upper end edge recessed toward the round hole  114  in generally U-shape as viewed from side. 
   The process grasp portion  110  is formed in generally rectangular shaped thin plate as viewed from front and extended between the front end portions of the right support portion  108  and the left support portion  109 . The process grasp portion  110  has a grip portion  118  whose the lower end edge recesses upward at the laterally central position thereof. 
   The respective support cylinders  135  of the right support portion  108  and the left support portion  109  are fitted into the first insertion holes  97  of the right wall  69  and the left wall  70 , so that the open/close lever  113  is pivotably supported on the right wall  69  and the left wall  70 . Accordingly, the open/close lever  113  is allowed to move between a lever closing position (see  FIG. 4(   b )) in which the process grasp portion  110  of the open/close lever  113  is positioned below the round hole  114 , and a lever opening position (see  FIG. 4(   a )) in which the process grasp portion  110  is arranged at the position identical to the round hole  114  in the vertical direction. The grip portion  118  is consistently exposed outward from the toner box accommodation chamber  71  as viewed from side irrespective of the position of the open/close lever  113 , as shown in  FIG. 3 . 
   In the developing chamber  72  of the rear-side casing  38 , the feed roller  101 , the developing roller  104 , and the layer-thickness regulating blade  107  are accommodated, as described above. 
   The feed roller  101  is disposed at obliquely rear side below the toner guiding port  88 . The feed roller  101  includes a metal feed roller shaft  102 , and a sponge roller  103  which is formed of a conductive foamed material and covers the feed roller shaft  102 . Both axial end portions of the feed roller shaft  102  are rotatably supported on the developer right wall  65  and the developer left wall  66  at the positions corresponding to the second bottom wall  74  in the anteroposterior direction. A driving force from a motor (not shown) is input to the feed roller shaft  102  to rotationally drive the feed roller  101 . 
   The developing roller  104  is disposed on the rear side of the feed roller  101  so as to be in contact with the feed roller  101  compressingly to each other. The developing roller  104  is longitudinal in the width direction and includes a metal developing roller shaft  105 , and a rubber roller  106  which is formed of a conductive rubber material and covers the developing roller shaft  105 . 
   Both axial end portions of the developing roller shaft  105  are rotatably supported on the developer right wall  65  and the developer left wall  66  at the positions corresponding to the first bottom wall  73  in the anteroposterior direction. The rubber roller  106  is formed of a conductive polyurethane rubber or a silicone rubber containing fine carbon particles and the like and the surface thereof is covered with a resin coating layer excellent in abrasion resistance such as polyurethane rubber or polyimide containing fluorine. A driving force from a motor (not shown) is input to the developing roller shaft  105  to rotationally drive the developing roller  104 . The developing roller  104  is applied with developing bias during developing process via one lateral end portion of the developing roller shaft  105  exposed from the developer right wall  65 , as shown in  FIG. 2 . 
   The layer-thickness regulating blade  107  is formed of a metal blade spring material and the free end thereof includes a pressing member  140  which is in a generally semicircular shape as viewed in section and formed of electrically insulative or conductive silicone rubber or polyurethane rubber, as shown in  FIG. 3 . In the layer-thickness regulating blade  107 , the proximal edge thereof is supported on the second top wall  116  of the developer top wall  67  above the developing roller  104 , whereby the pressing member  140  is in press contact to the developing roller  104  by the elastic force of the layer-thickness regulating blade  107 . 
   In the drum section  27  and the developing section  30 , the front end portion of the drum top wall  81  of the drum section  27  is fitted to the above described bending portion of the second top wall  116  of the developing section  30 , and, the respective rear end edges of the developer right wall  65  and the developer left wall  66  of the developing section  30  are brought into contact with the front end edges of the drum right wall  79  and the drum left wall  80  respectively, as shown in  FIG. 2 . Thus, the developing section  30  is assembled to the drum section  27 . In a state where the developing section  30  is assembled with the drum portion  27 , the first passing port  84  described above is formed between the developer rear bottom wall  68  and the drum bottom wall  82 , as shown in  FIG. 3 . 
   (b-3) Toner Box 
   The toner box  40  is detachably attached to the toner box accommodation chamber  71  of the developing section  30 , as described above. The toner box  40  can be attached to and removed from the main body casing  2  by attaching and detaching the process unit  20  to and from the main body casing  2  via the mounting port  6  while the toner box  40  is in the attached state in the process unit  20 . The attaching and detaching directions of the toner box  40  to and from the toner box accommodation chamber  71  of the process unit  20  are identical to the attaching and detaching directions of the process unit  20  to and from the main body casing  2 , that is, the obliquely downwardly rearward direction (attaching direction) and the obliquely upwardly forward direction (detaching direction), respectively. The direction orthogonal to the attaching and detaching directions of the toner box  40  to and from the toner box accommodation chamber  71  is the width direction. 
   Since the toner box accommodation chamber  71  is positioned in front of the process unit  20 , when the front cover  7  is opened and the mounting port  6  is released, the toner box  40  is exposed from the mounting port  6 , as shown in  FIG. 1 . 
   The toner box  40  is in generally a shape as viewed in left side section as shown in  FIG. 3 , and includes an outer casing  41  and an inner casing  42  which serve as examples of toner casing and are formed of resin and the like. Alternatively, only the outer casing  41  may serve as the toner casing. 
   (b-3-i) Outer Casing 
   The outer casing  41  is in generally a shape as viewed in section from the left side same as the toner box  40 , and integrally includes a cylinder  43  as an example of cylinder portion, and a guide lever  44  as an example of grasp portion. 
   As shown in  FIG. 5(   a ), the cylinder  43  is formed as a hollow cylinder which is generally in a rectangular shape as viewed from side and longitudinal in the width direction, and includes an outer round wall  45  as a round surface thereof, and a pair of outer side edge walls  46  formed as the both lateral side end faces of the outer round wall  45 . The cylinder  43  accommodates an agitator  56  described later and extends in the width direction along an agitator rotating shaft  53 . 
   In the central position of the rear side surface of the outer round wall  45  in the right-and-left and up-and-down directions, a first toner ejecting port  49  is formed as an example of second opening which extends through the outer round wall  45  in the thickness direction. The first toner ejecting port  49  is formed in a rectangular shape longitudinal in the width direction. 
   In both lateral end portions of the rear side surface of the outer round wall  45 , upper guide grooves  129  are formed respectively which extend through the outer round wall  45  in the thickness direction at the positions above the first toner ejecting port  49  and lower guide grooves  130  are formed respectively which extend through the outer round wall  45  in the thickness direction at the positions below the first toner ejecting port  49 . Each of the upper guide grooves  129  and the lower guide grooves  130  is in a rectangular shape as view from the rear and longitudinal in the circumferential direction, the circumferential length thereof is set approximately twice as long as that of the first toner ejecting port  49 , and the width length thereof is set approximately one-half of circumferential length of the first toner ejecting port  49 . 
   In the lower portion of the front side surface of the outer round wall  45 , positioning ribs  137  are formed respectively at positions which are spaced away by a distance equivalent to the one-quarter of the width size of the outer round wall  45  outwardly in the width direction from the center thereof, as shown in  FIG. 6 . The positioning rib  137  extends downwardly from the upper half portion of the front side surface of the outer round wall  45  in a continuous manner, and is bent to extend obliquely downwardly rearward, then is bent once again to extend rearward to continue to the rear half portion of the lower side surface of the outer round wall  45 , and is thus formed in a generally isosceles trapezoid shaped thin plate as viewed from side. The positioning rib  137  has a width size slightly narrower than the groove width of the positioning groove  138  described above. 
   Moreover, a projection exposing hole  149  is formed at the portion sandwiched in the width direction by the positioning ribs  137  at the lower part of the front side surface of the outer round wall  45 . The projection exposing hole  149  is formed in generally rectangular shape and extends through the outer round wall  45  in the thickness direction. 
   At a generally central position of each of the outer side edge walls  46  in anteroposterior and up-and-down directions, a second insertion hole  126  is formed which extends through each of the outer side edge walls  46  in the width direction, as shown in  FIG. 5(   a ). Further, in each of the outer side edge walls  46 , an insertion groove  127  is formed which extends through each of the outer side edge walls  46  in the width direction, and which is a minor arc concentric to the second insertion hole  126  at a radially outside position of the second insertion hole  126 , specifically, in a range from 12 o&#39;clock position to 2 o&#39;clock position as viewed from left side. 
   Further, each outer side edge wall  46  is formed integrally with an upper projection  144  at the position corresponding to the upper end edge of the upper side guide groove  129 . The upper projection  144  projects backward and is formed in generally reversed L-shaped thin plate as viewed from back in which the upper end thereof bends inward in the width direction. The outer side surface thereof in the width direction is provided integrally with a positioning projection  131  as an example of the first fixed portion. The positioning projection  131  projects outward in the width direction, and is formed in a column shape having an outer diameter smaller than the groove width of the guide groove  119  (see  FIG. 4(   a )) of the front-side casing  39  of the process unit  20  described above. The positioning projections  131  are provided at both lateral ends of the cylinder  43  so as to protrude outward from the cylinder  43 . 
   Further, each of the outer side edge walls  46  is formed integrally with a lower projection  145  at the position corresponding to the lower end edge of the lower guide groove  130 . The lower projection  145  projects backward, and is formed in generally reversed L-shaped thin plate as viewed from back in which the lower end thereof bends inward in the width direction. 
   The guide lever  44  is disposed at the upper end portion of the front side surface and the laterally central position of the outer round wall  45 , and includes a fixing member  91  and a swinging member  92 , as shown in  FIG. 6 . The positioning projection  131  described above is provided between the first toner ejecting port  49  and the guide lever  44  in the rotation direction (clockwise direction as viewed from left side in  FIG. 8 ) of the agitator  56  as an example of the agitating member to be described later. Specifically, the positioning projection  131  is disposed at the downstream side of the first toner ejecting port  49  and at the upstream side of the guide lever  44  in the rotation direction of the agitator  56 . 
   The fixing member  91  is formed in generally rectangular shape as viewed from top and is longitudinal in the width direction, and the rear end portion thereof is fixed to the outer round wall  45 , as shown in  FIG. 8 . 
   The swinging member  92  is formed in generally rectangular shape as viewed from top and generally T-shape as viewed in side section, and includes integrally a grip portion  93 , a first restricting portion  94 , and a second restricting portion  95 . 
   The grip portion  93  and the second restricting portion  95  are formed in generally rectangular shape as viewed from top. 
   The first restricting portion  94  is formed in rectangular shape as viewed from front and generally J-shape as viewed from left in section. The lower end portion of the first restricting portion  94  is formed with a first engaging portion  132  and a second engaging portion  133  as an example of the second fixed portion in this order from the top. The first engaging portion  132  is formed as a groove extending in the width direction so that the rear side surface of the lower end portion of the first restricting portion  94  recesses forward. The second engaging portion  133  is formed in generally hook shape as viewed from left in section in which the lowest end portion of the first restricting portion  94  slightly bends rearward below the first engaging portion  132 . Specifically, on the rear side surface of the second engaging portion  133 , a toner-side first surface  146  and a toner-side second surface  147  are formed (see the enlarged drawing of  FIG. 3 ). The toner-side first surface  146  extends generally in the up-and-down direction. The toner-side second surface  147  extends rearward from the lower end edge of the toner-side first surface  146 . The second engaging portion  133  is formed by the toner-side first surface  146  and the toner-side second surface  147  in the above-mentioned generally hook shape as viewed from left in section. Further, the second engaging portion  133  is provided so as to protrude outward from the cylinder  43  (see  FIG. 3 ). 
   Furthermore, the rear end portion of the grip portion  93 , the upper end portion of the first restricting portion  94 , and the front end portion of the second restricting portion  95  are connected with one another. In the connecting position between the rear end portion of the grip portion  93  and the upper end portion of the first restricting portion  94 , a shaft insertion hole  96  is formed to extend through the grip portion  93  and the first restricting portion  94  in the width direction. 
   On the front side surface of the outer round wall  45 , a pair of shaft support portions  98  are integrally formed so as to protrude forward and laterally sandwich the grip portion  93  of the swinging member  92  therebetween. An insertion shaft  37  extended between the pair of shaft support portions  98  is inserted through the shaft insertion hole  96  of the swinging member  92 , so that the swinging member  92  is swingably supported on the outer round wall  45 . 
   Further, the rear end portion of the fixing member  91  and the second restricting portion  95  of the swinging member  92  are connected by an elastic member  128 . Specifically, the elastic member  128  is, for example, a blade spring, and the one end portion thereof is threaded to the rear end portion of the fixing member  91  with a screw  134 , and the other end portion is engaged to the second restricting portion  95 . Thus, the swinging member  92  is continuously urged in a clockwise direction about the insertion shaft  37  so that the second restricting portion  95  comes close to the fixing member  91  by an urging force of the elastic member  128 . 
   (b-3-ii) Inner Casing 
   The inner casing  42  is longitudinal in the width direction, is formed in a hollow column having a size smaller than the cylinder  43  of the outer casing  41 , and integrally includes a cylindrical inner round wall  51  as an example of shutter member, and a pair of flat disc-like inner side edge walls  52  for blocking both lateral side surfaces of the inner round wall  51 , as shown in  FIG. 5(   c ). Between the centers of the circles of the respective inner side edge walls  52  which oppose to each other in the width direction, the agitator rotating shaft  53  is extended as an example of rotation shaft of the agitating member, as shown in  FIG. 3 . The agitator rotating shaft  53  is rotatably supported on the inner side edge walls  52 , and is provided with an agitator  56 . The agitator  56  is provided with wipers  50 . The wipers  50  are formed of, for example, a rubber and mounted to both axial (lateral) end portions of the agitator rotating shafts  53 . 
   The both lateral end portions of the agitator rotating shaft  53  protrude outward in the width direction from the respective inner side edge walls  52 , as shown in  FIG. 5(   c ). A collar  100  is fit onto each of the protruding portions of the agitator rotating shaft  53 . The collar  100  has an outer diameter slightly smaller than the hole diameter of the second insertion hole  126  (see  FIG. 5(   a )) of the outer casing  41 . 
   On the inner side edge walls  52 , lateral projections  54  are respectively provided which protrude outwardly in the width direction at positions which are radially outward from the agitator rotating shaft  53  and oppose to each other in the width direction. Each of the lateral projections  54  is formed in generally minor arc shape as viewed from side and the circumferential length thereof is approximately one-half of that of the insertion groove  127  of the outer casing  41  (described above), and the radial length thereof is slightly smaller than the groove width of the insertion groove  127 . 
   Moreover, at one portion on a circumference in the lateral center of the inner round wall  51 , specifically, at a position shifted by approximately 90° in a counterclockwise direction with respect to the lateral projection  54  as viewed from the left side, a second toner ejecting port  55  is formed as an example of shutter opening, and extends through the inner round wall  51  in the thickness direction. The second toner ejecting port  55  is formed in a rectangular shape with a size generally identical to that of the first toner ejecting port  49  of the outer casing  41  as viewed from the radial outside. 
   On the inner round wall  51 , a first radial projection  48  is provided along a circumferential edge of the second toner ejecting port  55  and protrudes outward in the radial direction. The first radial projection  48  is formed in a shape of a rectangular frame as viewed from the radial outside, and formed of elastic materials, such as rubber. 
   On both lateral end portions of the inner round wall  51 , the second radial projections  57  are integrally provided, respectively, at positions slightly above the upper end edge of the first radial projection  48  and protrude outward in the radial direction. Further, on the both lateral end portions of the inner round wall  51 , third radial projections  63  are integrally provided, respectively, and protrude outward in the radial direction at positions below the lower end edge of the first radial projection  48 . The second radial projection  57  and the third radial projection  63  are formed to have an identical size. The lateral lengths thereof are designed to be smaller than the groove widths of the upper guide groove  129  and the lower guide groove  130  of the outer casing  41 . 
   Further, on the inner round wall  51 , a fourth radial projection  99  is formed at a position opposite to the second toner ejecting port  55  in relation to the shaft center of the inner casing  42 , and protrudes outward in the radial direction and extends along the width direction, as shown in  FIG. 3 . The size of the fourth radial projection  99  in the width direction is designed to be smaller than the size of the projection exposing hole  149  of the outer casing  41  in the width direction. 
   (b-3-iii) Assembling of Inner Casing into Outer Casing 
   In the toner box  40  described above, the inner casing  42  is accommodated in the outer casing  41 , and both lateral end portions of the agitator rotating shafts  53  of the inner casing  42  are engaged respectively into the second insertion holes  126  of the outer casing  41  together with the collars  100  described above, as shown in  FIG. 5(   a ). Thereafter, each of the lateral projections  54  of the inner casing  42  is protruded outward in the width direction from each of the insertion grooves  127  of the outer casing  41 , each of the second radial projections  57  of the inner casing  42  is protruded outward in the radial direction of the inner casing  42  from each of the upper guide grooves  129  of the outer casing  41 , and each of the third radial projections  63  of the inner casing  42  is protruded outward in the radial direction of the inner casing  42  from each of the lower guide grooves  130  of the outer casing  41 . Moreover, the fourth radial projection  99  of the inner casing  42  is exposed in the projection exposing hole  149  of the outer casing  41  (see the  FIG. 8) . 
   Accordingly, the inner casing  42  is assembled into the outer casing  41 , and the inner casing  42  is pivotably supported on both of the outer side edge walls  46  of the outer casing  41 . As a result, each of the lateral projections  54  is allowed to slide along the corresponding insertion groove  127 , each of the second radial projections  57  is allowed to slide along the corresponding upper guide groove  129 , and each of the third radial projections  63  is allowed to slide along the corresponding lower guide groove  130 . The inner round wall  51  of the inner casing  42  pivots along the peripheral surface of the cylinder  43  of the outer casing  41  and can open and close the first toner ejecting port  49 . In the assembled state of the inner casing  42  into the outer casing  41 , as shown in  FIG. 8 , the first toner ejecting port  49  described above is located in back of the agitator  56  (on the downstream side in attaching direction of the toner box  40  to the developing section  30  to be described later). Moreover, the guide lever  44  is located on the opposite side of the first toner ejecting port  49  in relation to the agitator rotating shaft  53  of the agitator  56 . The second engaging portion  133  is located on the opposite side of the positioning projection  131  in relation to the agitator rotating shaft  53 . Specifically, both the second engaging portion  133  and the positioning projection  131  are located on the straight line X that passes the agitator rotating shaft  53  in the radial direction (see  FIG. 3 ). In other words, the second engaging portion  133  and the positioning projection  131  are arranged in symmetry with each other with reference to the agitator rotating shaft  53 . 
   When the toner box  40  thus assembled is in a state not being attached to the process unit  20  as shown in  FIG. 8 , the first engaging portion  132  in the first restricting portion  94  of the outer casing  41  engages with the fourth radial projection  99  of the inner casing  42 , and the pivot of the inner casing  42  with respect to the outer casing  41  is restricted. This state of the swinging member  92  will hereinafter be referred to as a first state. 
   In the first state as described above, when the guide lever  44 , that is, the fixing member  91  and the swinging member  92  are held together, the swinging member  92  swings in a counterclockwise direction about the insertion shaft  37  against the urging force of the elastic member  128 . After the fixing member  91  and the swinging member  92  are held together for a while, the swinging of the swinging member  92  stops. This state of the swinging member  92  will hereinafter be referred to as a second state. 
   In the second state, as shown in  FIG. 9 , the first engaging portion  132  of the afore-described first restricting portion  94  is apart from the fourth radial projection  99  of the inner casing  42 , and the engagement of the first engaging portion  132  with the fourth radial projection  99  is released. However, the rear end portion of the second restricting portion  95  is brought into contact with the inner round wall  51  of the inner casing  42 , so that the pivot of the inner casing  42  with respect to the outer casing  41  is restricted. 
   Therefore, when the swinging member  92  is in a third state which is between the first state and the second state, the engagement between the first engaging portion  132  and the fourth radial projection  99  is released and additionally, the rear end portion of the second restricting portion  95  is not brought into contact with the inner round wall  51  of the inner casing  42 , the restriction against the pivot of the inner casing  42  with respect to the outer casing  41  is released, as shown in  FIG. 3 . In this case, when the inner casing  42  is pivoted with respect to the outer casing  41 , each of the lateral projections  54  is guided to the corresponding insertion groove  127 , each of the second radial projections  57  is guided to the corresponding upper guide groove  129 , and each of the third radial projections  63  is guided to the corresponding lower guide grooves  130 , as shown in  FIG. 5(   b ). At the time of pivot of the inner casing  42  with respect to the outer casing  41 , the first radial projection  48  of the inner casing  42  is in sliding contact with the internal side surface of the outer round wall  45  of the outer casing  41 , whereby the outer casing  41  and the inner casing  42  are kept in air-tight and fluid-tight manner, as shown in  FIG. 3 . 
   Moreover, when the swinging member  92  is in the third state, the inner casing  42  can move to a toner blocking position where the internal spaces of the outer casing  41  and the inner casing  42  are sealed by blocking the first toner ejecting port  49  of the outer casing  41  by a portion other than the second toner ejecting port  55  in the inner round wall  51 , as shown in  FIG. 5(   b ). At this time, each of the second radial projections  57  is brought into contact with the upper end edge of the corresponding upper guide groove  129 , each of the third radial projections  63  is brought into contact with the upper end edge of the corresponding lower guide groove  130 , and each of the lateral projections  54  is brought into contact with the front end edge of the corresponding insertion groove  127 . On the other hand, the inner casing  42  can be moved to a toner opening position in which the first toner ejecting port  49  and the second toner ejecting port  55  are oppose to each other to open the internal portion of the outer casing  41  and the internal portion of the inner casing  42 , and at the same time, each of the second radial projections  57  is brought into contact with the lower end edge of the corresponding upper guide groove  129 , each of the third radial projections  63  is brought into contact with the lower end edge of the corresponding lower guide groove  130 , and each of the lateral projections  54  is brought into contact with the rear end edge of the corresponding insertion groove  127 , as shown in  FIG. 5(   a ). At this time, when the inner casing  42  is at the toner closing position (see  FIG. 8) , the second toner ejecting port  55  is located higher than in the case where the inner casing  42  is at the toner opening position (see  FIG. 3 ). 
   In the inner casing  42 , a positively chargeable non-magnetic single-component toner is contained as an example of a developing agent. As the toner, a polymerized toner is used. The polymerized toner is obtained by copolymerizing polymerizable monomers, for example, styrene monomers such as styrene, and acrylic monomers such as acrylic acid, alkyl (C1 to C4) acrylate, and alkyl (C1 to C4) methacrylate through suspension polymerization and the like. The polymerized toner is generally in spherical shape, extremely excellent in fluidity, and can achieve high quality image formation. 
   In such toner, a coloring agent such as carbon black or wax is mixed. Additionally, an additive agent such as silica is added to improve the fluidity. The toner has an average particle size of approximately 6 to 10 μm. 
   (b-4) Attaching and Detaching of Toner Box to and from Process Unit 
   (b-4-i) Attaching of Toner Box to Process Unit 
   The toner box  40 , in which the inner casing  42  is in the toner closing position, is attached from obliquely upper side in the obliquely downwardly rearward direction into the toner box accommodation chamber  71  of the developing section  30  of the process unit  20  which is in the state where the open/close lever  113  is at the lever closing position and the shutter  111  is in the developer closing position, as shown in  FIG. 8 . At this time, as shown in  FIG. 6 , each of the positioning projections  131  of the toner box  40  is received by the corresponding guide groove  119  in the toner box accommodation chamber  71  of the process unit  20  and guided by the guide groove  119 . The swinging member  92  of the toner box  40  is in the first state and the pivot of the inner casing  42  with respect to the outer casing  41  is restricted. With reference to  FIG. 8 , when the positioning projection  131  is guided by the guide groove  119 , the toner box  40  slightly pivots in clockwise direction as viewed from left side with the positioning projection  131  as a supporting point. The guide lever  44  also pivots slightly together with the toner box  40  in clockwise direction as viewed from left side. 
   Thereafter, when each of the positioning projections  131  reaches and contacts with the deepest portion of the corresponding guide groove  119 , the positioning projection  131  is fixed to the deepest portion of the guide groove  119  and the above-mentioned pivot of the toner box  40  stops (see  FIG. 9 ). Accordingly, attaching of the toner box  40  to the developing section  30  of the process unit  20  is completed. At this time, each of the lateral projections  54  of the toner box  40  is engaged to the corresponding receiving portion  117  of the open/close lever  113  at the lever closing position, as shown in  FIG. 7 . Moreover, each of the second radial projections  57  of the toner box  40  engages with the corresponding engagement portion  139  of the shutter  111  of the toner box accommodation chamber  71 , and the shutter  111  is sandwiched by the second radial projections  57  and the third radial projections  63  in the pivot direction, as shown in the  FIG. 9 . The swinging member  92  of the guide lever  44  is in the third state as shown in  FIG. 3  when the second engaging portion  133  engages with the engagement portion  124 . At this time, the toner-side first surface  146  of the second engaging portion  133  contacts with the developer-side first surface  142  of the engagement portion  124  from the front side, and whereby the second engaging portion  133  is fixed in the generally anteroposterior direction to the engagement portion  124  (see the enlarged drawing of  FIG. 3 ). On the other hand, the toner-side second surface  147  of the second engaging portion  133  contacts with the developer-side second surface  143  of the engagement portion  124  from below, and whereby the second engaging portion  133  is fixed in generally up-and-down direction to the engagement portion  124  (see the enlarged drawing of  FIG. 3 ). 
   Moreover, the positioning rib  137  of the toner box  40  is engaged in the positioning groove  138  of the process unit  20 , as shown in  FIG. 7 . 
   In this state, the positioning projections  131  are fixed to the respective guide grooves  119  and the second engaging portion  133  is fixed to the engagement portion  124  as described above, and whereby the toner box  40  is fixed to the toner box accommodation chamber  71 . 
   In a state where the toner box  40  is completely attached in the process unit  20 , the swinging member  92  is in the third state as described above, and thus the inner casing  42  is pivotable in relation to the outer casing  41 . Moreover, since each of the lateral projections  54  of the inner casing  42  is engaged with the corresponding receiving portion  117  of the open/close lever  113  which is in the lever closing position, when the open/close lever  113  is moved from the lever closing position to the lever opening position (see  FIG. 2 ), the inner casing  42  pivots from the toner closing position (see  FIG. 9 ) to the toner opening position (see  FIG. 3 ) and thus the first toner ejecting port  49  and the second toner ejecting port  55  are opposed and communicates to each other, as shown in  FIG. 3 . When the inner casing  42  pivots, the shutter  111  which is sandwiched between the corresponding second radial projection  57  and third radial projection  63  of the inner casing  42  also pivots from the developer closing position (see  FIG. 9 ) to the developer opening position, and the penetration hole  112  of the shutter  111  and the toner guiding port  88  of the toner box accommodation chamber  71  are opposed to each other. 
   In the toner box accommodation chamber  71  in which the shutter  111  is at the developer opening position, and in the toner box  40  in which the inner casing  42  is at the toner opening position, the penetration hole  112  and the toner guiding port  88  which are in the opposed state in the toner box accommodation chamber  71 , and the first toner ejecting port  49  and the second toner ejecting port  55  which are in the opposed state in the toner box  40 , are opposed to each other. As a result, the internal portion of the inner casing  42  of the toner box  40  and the internal portion of the developing chamber  72  of the developing section  30  communicate to each other via the toner guiding port  88 , the penetration hole  112 , the first toner ejecting port  49  and the second toner ejecting port  55 . 
   As described above, since a space between the outer casing  41  where the first toner ejecting port  49  is formed and the inner casing  42  where the second toner ejecting port  55  is formed, is kept in air-tight and fluid-tight manner by the first radial projection  48 , and further, since the seal member  125  is interposed in a space between the shutter  111  where the penetration hole  112  is formed and the curved wall  122  where the toner guiding port  88  is formed, the toner is prevented from leaking off to the outside from the toner guiding port  88 , the penetration hole  112 , the first toner ejecting port  49 , and the second toner ejecting port  55 . 
   (b-4-ii) Detaching of Toner Box from Process Unit 
   In a state where the shutter  111  is in the developer opening position and the inner casing  42  is in the toner opening position, the open/close lever  113  which is in the lever opening position, is moved to the lever closing position as shown in  FIG. 9 . At this time, the inner casing  42  in which each of the lateral projections  54  is engaged with the corresponding receiving portion  117  of the open/close lever  113 , pivots from the toner opening position to the toner closing position, whereby the first toner ejecting port  49  of the outer casing  41  is blocked by a portion of the inner round wall  51  other than the second toner ejecting port  55  and the internal portions of the outer casing  41  and the inner casing  42  are sealed. When the inner casing  42  pivots, the second radial projections  57  and the third radial projections  63  pivot accordingly. As a result, the shutter  111 , which is sandwiched by the corresponding second radial projection  57  and third radial projection  63 , pivots from the developer opening position to the developer closing position, whereby the toner guiding port  88  of the toner box accommodation chamber  71  is blocked by a portion of the shutter  111  other than the penetration hole  112 . 
   In this state, since the first restricting portion  94  is in the third state and the second engaging portion  133  is engaged with the engaged portion  124 , as shown in  FIG. 3 , the swinging member  92  is swung to the second state and the engagement between the second engaging portion  133  and the engaged portion  124  is released, as shown in  FIG. 9 . Then, while the swinging member  92  is remained in the second state (the swinging member  92  is held), the toner box  40  is drawn out toward the obliquely upwardly forward direction from the toner box accommodation chamber  71 . At this time, each of the positioning projections  131  (see  FIG. 6 ) of the toner box  40  is guided to the corresponding guide groove  119  (see  FIG. 6 ) in the toner box accommodation chamber  71 . The toner box  40  is drawn out when the positioning projections  131  are guided by the guide grooves  119 , whereby the toner box  40  slightly pivots in counterclockwise direction as viewed from left side with the positioning projections  131  as a supporting point. When the holding of the toner box  40  which has been drawn out, is released, the swinging member  92  is brought into the first state. 
   Thereafter, as shown in  FIG. 8 , each of the positioning projections  131  is out from the corresponding guide groove  119 , the engagement (see  FIG. 7 ) between each of the lateral projections  54  of the toner box  40  and the corresponding receiving portion  117  of the open/close lever  113  is released, and the engagement between each of the second radial projections  57  of the toner box  40  and the corresponding engaged portion  139  of the shutter  111  is released, whereby the detachment of the toner box  40  from the process unit  20  is completed. 
   (b-5) Developing and Transferring Operation 
   As described in (b-4-i) above and as shown in  FIG. 3 , after the toner box  40  is attached to the process unit  20  and accommodated in the toner box accommodation chamber  71 , a driving force from a motor (not shown) is input to the agitator rotating shaft  53  at image forming by the laser printer  1 . Then, the agitator rotating shaft  53  is rotated in clockwise direction as viewed from left and the agitator  56  moves (rotates) about the agitator rotating shaft  53  in circumferential direction (in clockwise direction as viewed from left) in the internal space of the inner casing  42  of the toner box  40 . Accordingly, the toner in the inner casing  42  of the toner box  40  is stirred by the agitator  56  and released into the developing chamber  72  via the second toner ejecting port  55 , the first toner ejecting port  49 , the penetration hole  112 , and the toner guiding port  88 . In accordance with the rotation of the agitator rotating shaft  53 , each of the aforedescribed wipers  50  of the agitator  56  wipes a toner detecting window (not shown) provided in the corresponding inner side edge wall  52  of the inner casing  42 , thereby cleaning the toner detecting windows (not shown) by the wipers  50 . 
   The toner supplied from the first toner ejecting port  49 , received in the toner guiding port  88  and released into the developing chamber  72 , is supplied to the developing roller  104  by the rotation of the feed roller  101 . At this time, the toner is triboelectrically positively charged between the feed roller  101  and the developing roller  104 . In accordance with the rotation of the developing roller  104 , the toner supplied onto the developing roller  104  enters between the pressing member  140  of the layer-thickness regulating blade  107  and the rubber roller  106  of the developing roller  104 , and are carried as a thin layer with a uniform thickness on the developing roller  104 . 
   In accordance with the rotation of the photosensitive drum  28 , the surface of the photosensitive drum  28  is uniformly positively charged by the scorotron charger  29 , and then exposed by laser beams of high-speed scanning from the scanning section  19 , and finally an electrostatic latent image which corresponds to the image to be formed on the sheet  3 , is formed. 
   Thereafter, by the rotation of the developing roller  104 , the toner which is carried on the developing roller  104  and positively charged, opposingly contacts with the photosensitive drum  28 . At this time, the toner is supplied to the electrostatic latent image formed on the surface of the photosensitive drum  28 , that is, a portion exposed by laser beams and has lower potential on the surface of the uniformly positively charged photosensitive drum  28 . Consequently, the electrostatic latent image on the photosensitive drum  28  is visualized and the toner image by reversal developing is carried on the surface of the photosensitive drum  28 . 
   After that, the toner image carried on the surface of the photosensitive drum  28  is transferred on the sheet  3  which is transported by the resist roller  15  (see  FIG. 1 ) and enters from the first passing port  84  into the drum casing  76 . During the passage of the sheet  3  through a transfer position between the photosensitive drum  28  and the transfer roller  31 , the toner image is transferred onto the sheet  3  by transfer bias applied on the transfer roller  31 . 
   The sheet  3  having a transferred toner image is ejected from the second passing port  85  to the outside of the drum casing  76  and transported to the fixing section  21 . 
   The toner remaining on the photosensitive drum  28  after the transfer is recovered by the developing roller  104 . 
   (c) Fixing Section 
   The fixing section  21  is provided in back of the process unit  20  and disposed in generally anteroposteriorly spaced relation to the photosensitive drum  28  of the process unit  20 , as shown in  FIG. 1 . The fixing section  21  includes a fixing frame  59 , and a heating roller  60  and a pressure roller  61  in the fixing frame  59 . 
   In the fixing section  21 , the toner image which has been transferred onto the sheet  3  in the transfer position, is thermally fixed on the sheet  3  when the sheet  3  passes between the heating roller  60  and the pressure roller  61 . The sheet  3  fixed with the toner image is transported to the sheet ejecting transport path and then transported to a sheet ejecting roller  141  by a transport roller  63 , and is finally ejected onto a sheet ejection tray  58  by the sheet ejecting roller  141 . The sheet ejection tray  58  is formed on the upper surface of the main body casing  2 . 
   2. Operations and Effects of the Embodiment 
   In the process unit  20 , when the toner box  40  is attached to the developing section  30  of the process unit  20  by gripping the guide lever  44  of the toner box  40 , the toner guiding port  88  of the developer casing  62  of the developing section  30  and the first toner ejecting port  49  of the toner box  40  are opposed to each other, as shown in  FIG. 3 . Accordingly, when the inner casing  42  is pivoted to the toner opening position, the toner accommodated in the toner box  40  can be supplied to the developing roller  104  of the developing section  30  through the toner guiding port  88  and the first toner ejecting port  49  which are communicated with each other. 
   The toner box  40  attached in the developing section  30  is accommodated in the toner box accommodation chamber  71  of the developer casing  62 . At this time, the positioning projections  131  of the outer casing  41  are fixed to the guide grooves  119  of the developer casing  62 , while the second engaging portions  133  of the outer casing  41  are fixed to the engagement portions  124  of the developer casing  62 , and whereby the toner box  40  is fixed to the toner box accommodation chamber  71 . 
   In the outer casing  41 , the positioning projection  131  is provided between the first toner ejecting port  49  and the guide lever  44  in the rotation direction of the agitator  56  (clockwise direction as viewed from left side in  FIG. 3 ) which is provided in the outer casing  41 . The second engaging portion  133  is disposed at the opposite side of the positioning projection  131  in relation to the agitator rotating shaft  53  of the agitator  56 . In other words, the positioning projections  131  are fixed to the guide grooves  119  and the second engaging portion  133  is engaged with the engagement portion  124 , so that the toner box  40  is fixed to the toner box accommodation chamber  71  at plural positions in the rotation direction of the agitator  56 . 
   Accordingly, even when the rotation of the agitator  56  causes rotational moment, the toner box  40  can be stably fixed to the developing section  30 , thereby preventing the toner leakage between the toner box  40  and the developing section  30 . 
   In the attaching of the toner box  40  to the developing section  30 , the guide lever  44  is gripped and the positioning projections  131  are received by the guide grooves  119  to be fixed thereto. Moreover, the second engaging portion  133  is fixed to the engagement portion  124  by pivoting with the guide lever  44  in the clockwise direction as viewed from left side in  FIG. 3  with the positioning projections  131  which are received in the guide grooves  119  as a supporting point. 
   As a result, the toner box  40  can be fixed to the developing section  30  with a simple operation wherein the guide lever  44  need not to be individually gripped in respective cases for fixing the positioning projections  131  to the guide grooves  119  and for fixing the second engaging portion  133  to the engagement portion  124 . 
   As a result, the toner box  40  can be stably fixed to the developing section  30  while maintaining a simple operability. 
   Moreover, the positioning projection  131  is disposed at the downstream side of the first toner ejecting port  49  in the rotation direction of the agitator  56  (clockwise direction as viewed from left side in  FIG. 3 ) and also at the upstream side of the guide lever  44  disposed at the opposite side of the first toner ejecting port  49  in relation to the agitator rotating shaft  53  of the agitator  56 . With this configuration, the first toner ejecting port  49  can be brought closer to the toner guiding port  88  by effectively utilizing the rotational moment which is applied in the clockwise direction as viewed from left side in relation to the positioning projection  131  during the rotation of the agitator  56 , compared with the case where the positioning projection  131  is disposed at the upstream side of the first toner ejecting port  49  and also at the downstream side of the guide lever  44  in the rotation direction of the agitator  56 . This can reduce the toner leakage between the toner guiding port  88  and the first toner ejecting port  49 . 
   Moreover, the engagement portion  124  is provided with the developer-side first surface  142  and the developer-side second surface  143 . As described above, the toner-side first surface  146  of the second engaging portion  133  contacts with the developer-side first surface  142 , and the toner-side second surface  147  of the second engaging portion  133  contacts with the developer-side second surface  143 , and whereby the second engaging portion  133  is fixed in generally anteroposterior direction and generally up-and-down direction in relation to the engagement portion  124 . The “generally anteroposterior direction” is referred to a direction close to the rotation direction of the agitator  56  (clockwise direction as viewed from left side in  FIG. 3 ), and the “generally up-and-down direction” is referred to a direction close to the attaching and detaching directions of the toner box  40  to and from the developing section  30 . In other words, since the second engaging portion  133  is fixed respectively in the rotation direction of the agitator  56  and the attaching and detaching directions of the toner box  40  to and from the developing section  30  by the developer-side first surface  142  and the developer-side second surface  143  of the engagement portion  124 , the toner box  40  can be fixed more stably to the developing section  30 . 
   Moreover, the positioning projection  131  and the second engaging portion  133  are provided so as to achieve a symmetric arrangement with each other with reference to the agitator rotating shaft  53  of the agitator  56 . With this arrangement, it is prevented that the toner box  40  leans inappropriately to either the positioning projection  131  or the second engaging portion  133  in the rotation direction of the agitator  56  even when the rotation of the agitator  56  generates the rotational moment, and whereby the toner box  40  can be stably fixed to the developing section  30 . 
   Moreover, the positioning projection  131  and the second engaging portion  133  are provided to protrude outward from the cylinder  43  of the outer casing  41 . With this arrangement, since the fixing positions of both the positioning projection  131  and the second engaging portion  133  can be spaced from the agitator rotating shaft  53  of the agitator  56  accommodated in the cylinder  43 , the respective fixing states of the positioning projection  131  and the second engaging portion  133  can be prevented from being influenced by the rotation of the agitator  56 , and whereby the toner box  40  can be more stably fixed to the developing section  30 . 
   Moreover, the positioning projections  131  are provided at both ends of the cylinder  43  (see  FIG. 5 ) in the axial direction (width direction) of the agitator  56 , thereby preventing the positioning projection  131  from interfering with the attaching and detaching of the toner box  40  to and from the developing section  30 . 
   Moreover, the second toner ejecting port  55  of the inner round wall  51  is located in the higher position (see  FIGS. 3 and 8 ) in the case where the inner round wall  51  closes the first toner ejecting port  49  compared with the case where the inner round wall  51  opens the first toner ejecting port  49 . With this arrangement, the second toner ejecting port  55  moves downward when the inner round wall  51  opens the first toner ejecting port  49 . Accordingly, by using the gravity, the toner that settled on the surrounding edge of the second toner ejecting port  55  can be moved inside the first toner ejecting port  49  or the inner casing  42 , thereby removing the toner from the surrounding edge of the second toner ejecting port  55 . 
   Second Embodiment 
   In the first embodiment describes above, the process unit  20  integrally includes the drum portion  27  and the developing section  30 , and the process unit  20  can be detachably attached to the main body casing  2 . In addition to this, the developing section  30  may be detachably attached to the drum section  27 . 
   Third Embodiment 
     FIG. 10(   a ) is a left perspective view of a toner box to which a third embodiment is applied as viewed from above the rear side, while  FIG. 10(   b ) is a left side view of a toner box of  FIG. 10(   a ) placed on a placement surface. 
   In the toner box  40  according to the third embodiment, the upper projection  144  and the lower projection  145  are examples of the preventing member and each of the rear end edges thereof is formed to be located rearward from the first toner ejecting port  49 , as shown in  FIG. 10(   a ). Specifically, the rear end edge of the upper projection  144  and the rear end edge of the lower projection  145  are positioned equally with each other in the anteroposterior direction. 
   Therefore, the rear ends of the upper projection  144  and the lower projection  145  are allowed to contact with a placement surface  148  when the toner box  40  is detached from the developing section  30  and placed on the placement surface  148 , so that the first toner ejecting port  49  can be disposed in a spaced relation to the placement surface  148 , as shown in  FIG. 10(   b ). In other words, the upper projection  144  and the lower projection  145  can prevent the interference of the placement surface  148  with the first toner ejecting port  49 . Accordingly, the placement surface  148  does not interfere with the first toner ejecting port  49  to open the first toner ejecting port  49 , so that the toner leakage from the first toner ejecting port  49  can be prevented. 
   Moreover, the positioning projection  131  is provided at the cylinder  43  of the outer casing  41  and the upper projection  144  includes the positioning projection  131 , thereby simplifying the configuration and reducing the number of components. 
   In the description above, three independent embodiments of the first embodiment, the second embodiment and the third embodiment to be applied with one or more aspects of the present invention, have been described in detail. However, it should be noted that one skilled in the art may optionally combine the gist of these three embodiments and provide a process cartridge having advantages described above in relation to the three embodiments. 
   The embodiments described above are illustrative and explanatory of the invention. The foregoing disclosure is not intended to be precisely followed to limit one or more aspects of the present invention. Various modifications and alterations are possible in light of the foregoing description, and may be obtained by implementing the invention. The present embodiments are selected and described for explaining the essence and practical applicational schemes of one or more aspects of the present invention which allow those skilled in the art to utilize one or more aspects of the present invention in various embodiments and various alterations suitable for anticipated specific use. The scope of the present invention is to be defined by the appended claims and their equivalents.