Patent Publication Number: US-9411261-B2

Title: Developer cartridge having spacer between housing and layer thickness regulation blade

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from Japanese Patent Application No. 2013-195349, filed on Sep. 20, 2013, which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     Aspects disclosed herein relate to a cartridge used in an image forming apparatus which employs electrophotography. 
     BACKGROUND 
     There have been known electrophotographic printers where developing cartridges are detachably mounted. Such known developing cartridges detachably mounted to a printer include a developing cartridge having a developing frame which accommodates toner, a developing roller which carries toner, and a member which regulates the thickness of a toner layer carried by the surface of the developing roller. 
     SUMMARY 
     The developing frame of this developing cartridge has a screwing portion, and the screwing portion, the layer thickness regulating member, and the developing roller are arrayed in a front/back direction. The screwing portion has protruding bosses arrayed toward the layer thickness regulating member, i.e., in the front/back direction, so as to fix the layer thickness regulating member to a housing. 
     Accordingly, in a case of attaching/detaching the layer thickness regulating member to/from the developing cartridge for maintenance or the like, the layer thickness regulating member is moved in the front/back direction so as to be engaged/disengaged with/from the bosses of the screwing portion. The developing roller has to be detached from the developing cartridge in order to move the layer thickness regulating member in the front/back direction. 
     That is to say, in order to attach/detach the layer thickness regulating member to/from the developing cartridge, the developing roller also has to be attached/detached, which is problematic in that the number of work steps increases. 
     Accordingly, it is an object of the present invention to provide a cartridge where the layer thickness regulating member can be easily replaced. 
     According to one or more aspects of the disclosure, a cartridge may include a housing configured to accommodate a developing agent therein, a developing agent carrying member configured to carry the developing agent, a layer thickness restricting member disposed between the housing and the developing agent carrying member and configured to restrict a layer thickness of the developing agent carried by the developing agent carrying member, and a spacer disposed between the housing and the layer thickness restricting member in a first direction in which the developing agent carrying member and the layer thickness restricting member face one another and in which is orthogonal to a longitudinal direction of the developing agent carrying member. The spacer may include a first engaged portion configured to be engaged. The layer thickness restricting member may include a first engaging portion configured to engage with the first engaged portion such that relative movement of the spacer and the layer thickness restricting member is restricted. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view taken along the middle of a developing cartridge according to a first embodiment of a cartridge according to the present embodiment. 
         FIG. 2  is a cross-sectional view taken along the middle of a printer using the developing cartridge illustrated in  FIG. 1 . 
         FIG. 3A  is a perspective view of the developing cartridge illustrated in  FIG. 1  as viewed from the left rear side; and  FIG. 3B  is a cross-sectional view taken along line A-A in  FIG. 3A . 
         FIG. 4  is a disassembled perspective view of the developing cartridge illustrated in  FIG. 1  as viewed from the left rear side. 
         FIG. 5A  is a perspective view of a square spacer illustrated in  FIG. 4  as viewed from the left rear side; and  FIG. 5B  is a perspective view of the square spacer illustrated in  FIG. 4  as viewed from the left front side. 
         FIG. 6A  is an explanatory diagram for describing attaching/detaching of the layer thickness regulating blade of the developing cartridge illustrated in  FIG. 3A , illustrating a state where screws have been removed and engagement of the layer thickness regulating blade and square spacers has been disengaged; and  FIG. 6B  is a cross-sectional view taken along line B-B in  FIG. 6A . 
         FIG. 7A  is an explanatory diagram for describing attaching/detaching of the layer thickness regulating blade of the developing cartridge as a continuation from  FIG. 6A , illustrating a state where the square spacers have been detached from the developing frame; and  FIG. 7B  is a cross-sectional view taken along line C-C in  FIG. 7A . 
         FIG. 8A  is an explanatory diagram for describing attaching/detaching of the layer thickness regulating blade of the developing cartridge as a continuation from  FIG. 7A , illustrating a state where the square spacers have been detached from the developing frame and the layer thickness regulating blade is compressing a blade seal; and  FIG. 8B  is a cross-sectional view taken along line D-D in  FIG. 8A . 
         FIG. 9A  is a perspective view of a developing cartridge according to a second embodiment of the present invention as viewed from the left rear side; and  FIG. 9B  is a cross-sectional view taken along line E-E in  FIG. 9A . 
         FIG. 10  is a disassembled perspective view of the developing cartridge illustrated in  FIG. 9A  as viewed from the left rear side. 
         FIG. 11A  is a perspective view of a rotational spacer illustrated in  FIG. 10  as viewed from the left rear side; and  FIG. 11B  is a perspective view of the rotational spacer illustrated in  FIG. 10  as viewed from the left front side. 
         FIG. 12A  is an explanatory diagram for describing attaching/detaching of the layer thickness regulating blade of the developing cartridge illustrated in  FIG. 9A , illustrating a state where screws have been removed and the rotational spacers have been rotated, and  FIG. 12B  is a cross-sectional view taken along line F-F in  FIG. 12A . 
         FIG. 13A  is an explanatory diagram for describing attaching/detaching of the layer thickness regulating blade of the developing cartridge as a continuation from  FIG. 12A , illustrating a state where the rotational spacers have been detached from the developing frame, and  FIG. 13B  is a cross-sectional view taken along line G-G in  FIG. 13A . 
     
    
    
     DETAILED DESCRIPTION 
     1. Overview of Developing Cartridge 
     A developing cartridge  1  which is an example of a cartridge includes a developing frame  2  which is an example of a housing, an agitator  3 , a developing roller  4  which is an example of a developing agent carrying member, a supply roller  5 , and a layer thickness regulating blade  6  which is an example of a layer thickness restricting member, as illustrated in  FIG. 1 . 
     Note that in the following description, when referring to directions regarding the developing cartridge  1 , the side of the developing roller  4  where the developing roller  4  is disposed will be referred to as the rear of the developing cartridge  1 , and the opposite side thereof will be referred to as the front. That is to say in  FIG. 1 , the left side in the plane of the drawing is the rear, and the right side in the plane of the drawing is the front. The top side in the plane of the drawing is upwards, and the bottom side in the plane of the drawing is downwards. The terms “left” and “right” regarding the developing cartridge  1  refer to when viewing the developing cartridge  1  from the front. That is to say, the near side in the drawing in  FIG. 1  is the left side, and the far side in the drawing is the right side. The front-back direction is one example of a first direction, with the direction toward the front being an example of one way in the first direction and the direction toward the back being an example of the other way in the first direction. 
     The developing frame  2  is in a generally box form extending in the left-right directions, with the rear end portion of the developing frame  2  opened in the front-back direction. The developing frame  2  includes a toner accommodation chamber  7  and a developing chamber  8  therein, disposed in parallel in the front-back direction. The toner accommodation chamber  7  accommodates toner, which is an example of developing agent. 
     The agitator  3  is disposed around the middle portion of the toner accommodation chamber  7  in the front-back and vertical directions. 
     The developing roller  4  is disposed at the rear end portion of the developing chamber  8 . The developing roller  4  includes a developing roller shaft  13  and a rubber roller  14 . 
     The developing roller shaft  13  has a generally cylindrical form extending in the left-right direction. 
     The rubber roller  14  has a generally cylindrical form, and covers the developing roller shaft  13  so that both the left and right end portions of the developing roller shaft  13  are exposed. 
     The developing roller  4  is supported by the developing frame  2 , by the left and right end portions of the developing roller shaft  13  being rotatably supported by a pair of side walls  50 , described later. The upper portion and rear portion of the rubber roller  14  of the developing roller  4  are exposed from the developing frame  2 . 
     The supply roller  5  is disposed at the lower front side of the developing roller  4  within the developing chamber  8 . The supply roller  5  includes a supply roller shaft  16  and a sponge roller  17 . 
     The supply roller shaft  16  has a generally cylindrical form extending in the left-right direction. 
     The sponge roller  17  has a generally cylindrical form, and covers the supply roller shaft  16  so that both the left and right end portions of the supply roller shaft  16  are exposed. 
     The supply roller  5  is supported by the developing frame  2 , by the left and right end portions of the supply roller shaft  16  being rotatably supported by the pair of side walls  50 , described later. The upper rear portion of the sponge roller  17  of the supply roller  5  is pressed against the lower front portion of the rubber roller  14 . 
     The layer thickness regulating blade  6  is disposed to the upper front of the developing roller  4  within the developing chamber  8 . The layer thickness regulating blade  6  is supported by the developing frame  2  by way of later-described square spacers  44 , so that the lower edge portion of the layer thickness regulating blade  6  comes into contact with the upper front portion of the rubber roller  14  of the developing roller  4 . 
     2. Overall Configuration of Printer 
     A printer  20  is an electrophotographic black-and-white printer, as illustrated in  FIG. 2 . The printer  20  includes a main body casing  21 , a process cartridge  22 , a scanner unit  23 , and a fixing unit  24 . 
     The main body casing  21  has a general box shape. The main body casing  21  has an opening portion  25 , a front cover  26 , a sheet feed tray  38 , and a sheet discharge tray  39 . 
     The opening portion  25  is configured such that the front wall of the main body casing  21  is opened in the front-back direction, allowing passage of the process cartridge  22 . 
     The front cover  26  has a general plate form, generally L-shaped in side view. The front cover  26  is supported by the lower edge thereof as a pivot so as to be capable of rocking as to the front wall of the main body casing  21 . The front cover  26  is configured so as to open or close the opening portion  25 . 
     The sheet feed tray  38  is disposed on the bottom within the main body casing  21 , and is configured to store sheets P. 
     The sheet discharge tray  39  is disposed on the upper face of the main body casing  21 . 
     The process cartridge  22  is configured to be mounted to and detached from the main body casing  21 , via the opening portion  25 . The process cartridge  22  includes a drum cartridge  27  and the aforementioned developing cartridge  1 . 
     The drum cartridge  27  includes a photosensitive drum  29 , a scorotron charger  30 , and a transfer roller  31 . 
     The photosensitive drum  29  is rotatably supported at the rear end of the process cartridge  22 . The photosensitive drum  29  has a generally cylindrical form extending on the left-right direction. 
     The scorotron charger  30  is disposed behind the photosensitive drum  29 , with spacing provided between the photosensitive drum  29  and scorotron charger  30 . 
     The transfer roller  31  is disposed beneath the photosensitive drum  29 . The top portion of the transfer roller  31  comes into contact with the bottom portion of the photosensitive drum  29 . 
     The developing cartridge  1  is configured so as to be mounted to and detached from the drum cartridge  27 . In a state where the developing cartridge  1  is mounted to the drum cartridge  27 , the rearmost portion of the developing roller  4  comes into contact with the foremost portion of the photosensitive drum  29 . 
     A scanner unit  23  is disposed above the process cartridge  22 . The scanner unit  23  is configured to emit a laser beam toward the photosensitive drum  29 , based on image data, as illustrated by a dashed line in  FIG. 2 . 
     The fixing unit  24  is disposed behind the process cartridge  22 . The fixing unit  24  includes a heating roller  34 , and a pressure roller  35  which is pressed against the lower rear portion of the heating roller  34 . 
     Upon the printer  20  starting image forming operations under control of a control unit omitted from illustration, the scorotron charger  30  uniformly charges the surface of the photosensitive drum  29 . Thereafter, the scanner unit  23  exposes the surface of the photosensitive drum  29 . Thus, an electrostatic latent image based on the image data is formed on the surface of the photosensitive drum  29 . 
     The agitator  3  stirs toner within the toner accommodation chamber  7 , so as to be supplied to the supply roller  5 . The supply roller  5  supplies the toner supplied from the agitator  3  to the developing roller  4 . At this time, the toner is charged by friction to a positive polarity between the developing roller  4  and the supply roller  5 , and is carried by the developing roller  4 . The layer thickness regulating blade  6  regulates the thickness of the toner layer carried on the developing roller  4  to a constant thickness. 
     The toner carried by the developing roller  4  is then supplied to the electrostatic latent image on the surface of the photosensitive drum  29 . Accordingly, a toner image is carried on the surface of the photosensitive drum  29 . 
     Sheets P are fed one at a time from the sheet feed tray  38 , at predetermined timings, by rotation of various rollers, and fed to the nip of the photosensitive drum  29  and transfer roller  31 . The toner image on the photosensitive drum  29  is transferred to the sheet P when passing between the photosensitive drum  29  and the transfer roller  31 . 
     Thereafter, the sheet P is heated and pressurized when passing between the heating roller  34  and the pressure roller  35 . The toner image on the sheet P is thermally fixed to the sheet P at this time. Thereafter, the sheet P is discharged to the sheet discharge tray  39 . 
     3. Detailed Description of Developing Cartridge 
     The developing cartridge  1  includes the aforementioned developing frame  2 , the aforementioned layer thickness regulating blade  6 , a blade seal  45  which is an example of a seal member, side seals  46 , and the square spacers  44  which are an example of spacers, as illustrated in  FIGS. 3A and 3B . 
     Note that the developing cartridge  1  has a driving unit  42  to the left side of the developing frame  2 . The driving unit  42  is configured so as to transmit driving force, from an unshown driving source of the main body casing  21 , to each of the agitator  3 , developing roller  4 , and supply roller  5 . 
     The developing cartridge  1  also has an electrode unit  43  to the right of the developing frame  2 . The electrode unit  43  is configured so as to supply electric power from an unshown external power source to the developing roller  4  and the supply roller  5 . 
     (1) Developing Frame 
     The developing frame  2  has a base frame  47  and a cover frame  48 , as illustrated in  FIGS. 1 and 4 . 
     The base frame  47  is formed as a frame having a bottom. The base frame  47  has the pair of side walls  50 , a lower wall  51 , and a front wall  52 . 
     The pair of side walls  50  is disposed at the left and right edge portions of the base frame  47 . Each side wall  50  in the pair has a main unit  55 , a seal supporting unit  56 , a spacer fixing portion  58  which is an example of a fixing portion, and a developing roller attaching portion  59 , as illustrated in  FIGS. 3B and 4 . 
     The main unit  55  makes up the front half of the side walls  50 . The main unit  55  is of a general plate form, generally rectangular in side view, and extends in the front-back direction. 
     The seal supporting unit  56  protrudes outwards to the left and right directions from the rear edge portion of the main unit  55 , and extends vertically. Each seal supporting unit  56  includes a blade seal supporting portion  62 , a side seal supporting portion  63 , and a shaft seal supporting portion  64 . 
     The blade seal supporting portion  62  is disposed above the seal supporting unit  56 . The blade seal supporting portion  62  has a generally rectangular shape in frontal view. 
     The side seal supporting portion  63  extends downward from the blade seal supporting portion  62 . The side seal supporting portion  63  extends continuously downward from the lower edge of the blade seal supporting portion  62 , curves backwards following the perimeter of the rubber roller  14 , and extends toward the rear. 
     The shaft seal supporting portion  64  is disposed around the middle of the side seal supporting portion  63  in the vertical direction. The side seal supporting portion  63  is recessed toward the lower front from the rear face of the side seal supporting portion  63  and extends in the left-right direction. The shaft seal supporting portion  64  is a generally square tube, with the end at the left and right ends being opened. The shaft seal supporting portion  64  supports a shaft seal  65 . 
     The shaft seal  65  is a generally square tube, extending in the left-right direction. The shaft seal  65  is formed of an elastic material such as sponge or the like, and has a supply roller shaft insertion hole  66  formed therein. 
     The supply roller shaft insertion hole  66  is situated at the generally middle portion of the shaft seal  65  in side view. The supply roller shaft insertion hole  66  has a generally circular shape in side view, and pass through the shaft seal  65  in the left-right direction. The rear face of the shaft seal  65  is generally arc-shaped in side view, so as to follow the perimeter of the rubber roller  14 , and is generally flush with the rear face of the side seal supporting portion  63 . 
     The spacer fixing portion  58  continues from the upper edges of the seal supporting units  56  and protrudes upwards. Each spacer fixing portion  58  has a base portion  70 , an extending portion  71 , a cylindrical portion  72 , and a frame boss  73  which is an example of a second engaged portion. 
     The base portion  70  is disposed at the bottom portion of the spacer fixing portion  58 , as illustrated in  FIG. 4 . The base portion  70  has a general plate shape, which bends outwards in the left and right directions after having protruded upwards continuously from the top portion of the seal supporting unit  56 . The outer edge portions of the base portion  70  in the left-right direction are continuous with inner faces of later-described developing roller attaching portions  59 . 
     The extending portion  71  is disposed at the front edge of the spacer fixing portion  58 , and has a general plate form, generally rectangular in frontal view. The base portion  70  has a generally rectangular shape in plan view. The lower portion of the rear of the extending portion  71  is continuous with the front edge portion of the base portion  70 , and the outer edge portions of the extending portions  71  in the left-right direction are continuous with inner face of the later-described developing roller attaching portions  59 . 
     The cylindrical portion  72  has a generally cylindrical shape extending in the left-right direction, and is embedded in a bent portion of the base portion  70 . The front edge portion of the cylindrical portion  72  is connected to the inner portions in the left-right direction of the extending portion  71  at the rear face thereof. A rear face  74  of the cylindrical portion  72  is formed following the vertical and left-right directions. 
     The frame boss  73  is disposed on the rear face  74  of the cylindrical portion  72 . The frame boss  73  protrudes rearwards from the inner peripheral edge of the cylindrical portion  72  at the rear face  74  thereof, that is to say toward the square spacer  44  in a state where the layer thickness regulating blade  6  is assembled to the developing frame  2  by the square spacers  44 . The frame boss  73  has a generally cylindrical shape, and is formed such that the outer diameter thereof is smaller than the outer diameter of the cylindrical portion  72 . The inner diameter of the frame boss  73  is generally the same as the inner diameter of the cylindrical portion  72 . The rear edge portion of the frame boss  73  is situated further toward the front than the rear face of the blade seal supporting portion  62 , as illustrated in  FIG. 3B . 
     Note that the cylindrical portion  72  and frame boss  73  have screw threads formed on the inner peripheral faces thereof, omitted from illustration. 
     The developing roller attaching portion  59  extends rearwards from the outer edge portion of the seal supporting unit  56  in the left-right direction, as illustrated in  FIG. 4 . The top of the developing roller attaching portion  59  protrudes upwards beyond the seal supporting unit  56 . Also, the shape of the developing roller attaching portion  59  which the left side wall  50  has and the shape of the developing roller attaching portion  59  which the right side wall  50  has are different. Accordingly, description will be made hereinafter by referring to the left side developing roller attaching portion  59  as “left developing roller attaching portion  59 L” and the right side developing roller attaching portion  59  as “right developing roller attaching portion  59 R”. 
     The left developing roller attaching portion  59 L has a general plate shape which is generally rectangular in side view, and which extends vertically. The left developing roller attaching portion  59 L has a developing roller shaft insertion hole  68  and a notched groove  77 . 
     The developing roller shaft insertion hole  68  is disposed at the bottom portion of the left developing roller attaching portion  59 L. The developing roller shaft insertion hole  68  has a generally circular shape in side view, with the rear part opened. The developing roller shaft insertion hole  68  penetrates the left developing roller attaching portion  59 L in the left-right direction. The inner diameter of the developing roller shaft insertion hole  68  is greater than the diameter of the developing roller shaft  13  of the developing roller  4 . 
     The notched groove  77  is situated at the upper right portion of the left developing roller attaching portion  59 L, around the middle in the front-back direction. The notched groove  77  is recessed from the right face of the left developing roller attaching portion  59 L toward the left, and has a general open-box shape with the right side and top being opened. 
     The right developing roller attaching portion  59 R is generally rectangular in side view, and has a general plate shape which is generally crank-shaped in rear view. The right developing roller attaching portion  59 R has a top portion  79 , an inclined portion  80 , and a bottom portion  81 . 
     The top portion  79  forms the upper portion of the right developing roller attaching portion  59 R. The top portion  79  has a general plate shape, generally rectangular in side view, and extends in the vertical direction. 
     The inclined portion  80  forms the generally middle portion of the right developing roller attaching portion  59 R in the vertical direction. The inclined portion  80  continues from the bottom portion of the top portion  79 , and extends inclining to the left from there on down. 
     The bottom portion  81  forms the lower portion of the right developing roller attaching portion  59 R. The bottom portion  81  continues from the bottom portion of the inclined portion  80  and extends downwards. The bottom portion  81  has a developing roller shaft insertion hole  68 , the same as described above, formed at the rear end portion thereof. 
     The developing roller attaching portions  59  rotatably support by the developing roller  4  by accepting the left and right end portions of the developing roller shaft  13  of the developing roller  4  in the left and right developing roller shaft insertion holes  68 . 
     The lower wall  51  has a general plate shape extending in the front-back direction, as illustrated in  FIG. 1 , curving downwards. The left and right edge portions of the lower wall  51  continue to the bottom portion of the pair of side walls  50 . 
     The front wall  52  continues from the front edge portion of the lower wall  51  and extends upwards. The front wall  52  has a general plate shape, generally rectangular in frontal view. The left and right edge portions of the front wall  52  continue to the front edge portion of the main unit  55  of the pair of side walls  50 . 
     The cover frame  48  is disposed above the base frame  47  as illustrated in  FIG. 4 . The cover frame  48  integrally includes a cover portion  86  and a blade seal supporting portion  87 . 
     The cover portion  86  has a general plate shape, generally rectangular in plan view. The front edge of the cover portion  86  is fused to the top portion of the front wall  52  of the base frame  47 . The left and right edges of the cover portion  86  are fused to the top portions of the pair of side walls  50  of the base frame  47 . 
     The blade seal supporting portion  87  is disposed between the rear edge portions of the pair of the side walls  50  of the base frame  47 , behind the cover portion  86 . The blade seal supporting portion  87  has a general plate shape, generally rectangular in plan view. The blade seal supporting portion  87  continues from the rear edge portion of the cover portion  86  and extends rearwards. The left and right edge portions of the blade seal supporting portion  87  are fused to the pair of side walls  50  of the base frame  47 . The blade seal supporting portion  87  has a plurality of screw accommodating portions  88 , the number of which is four here. 
     The four screw accommodating portions  88  are disposed in the left-right direction with intervals therebetween, at the generally middle portion of the blade seal supporting portion  87  in the front-back direction. Each screw accommodating portion  88  is recessed downwards from the upper face of the blade seal supporting portion  87 , and has a generally rectangular shape in plan view, extending in the front-back direction. 
     (2) Layer Thickness Regulating Blade 
     The layer thickness regulating blade  6  has a first clamping member  91 , a second clamping member  92 , and a blade member  93 , as illustrated in  FIGS. 1 and 4 . 
     The first clamping member  91  is disposed above the blade seal supporting portion  87  of the cover frame  48 . The first clamping member  91  has a bent plate shape, slender in the left-right direction and generally L-shaped in cross-section. In further detail, the first clamping member  91  extends in the front-back direction, and bends downward at the rear edge portion thereof. The first clamping member  91  includes two clamping portion edge portions  95  and two abutting portions  97  as illustrated in  FIG. 4 . 
     Each of the two clamping portion edge portions  95  protrude upwards from the left and right end portions of the rear edge portion of the first clamping member  91 . Each of the two clamping portion edge portions  95  has a general plate shape, generally rectangular in frontal view, and has a first through hole  96  which is an example of a first through-hole. 
     The first through holes  96  penetrate the clamping portion edge portions  95  in the front-back direction. The first through holes  96  have a generally circular shape in frontal view. The inner perimeters of the first through holes  96  define first engaging portions  98 . 
     Each of the two abutting portions  97  is cut so that the end portions of the bottom portion of the first clamping member  91  in the left-right direction are chamfered. The abutting portions  97  incline upwards toward the outside in the left-right direction. 
     The second clamping member  92  is disposed above the first clamping member  91  as illustrated in  FIGS. 1 and 4 . The second clamping member  92  has a bent plate shape, slender in the left-right direction and generally L-shaped in cross-section. In further detail, the second clamping member  92  extends in the front-back direction above the first clamping member  91 , and bends downward at the rear edge portion thereof so as to face the rear end portion of the first clamping member  91 . The dimensions of the second clamping member  92  in the left-right direction are shorter than the dimensions of the first clamping member  91  in the left-right direction. The second clamping member  92  is fixed to the first clamping member  91  by screws  99 . 
     The blade member  93  has a general plate shape, slender in the left-right direction and generally rectangular in frontal view. The blade member  93  extends in the vertical direction. The dimensions of the blade member  93  in the left-right direction are shorter than the dimensions of the first clamping member  91  in the left-right direction, and are longer than the dimensions of the second clamping member  92  in the left-right direction. The top portion of the blade member  93  is clamped between the rear end portion of the first clamping member  91  and the rear end portion of the second clamping member  92 . The bottom portion of the blade member  93  is in contact with the top portion of the developing roller  4  in a state where the layer thickness regulating blade  6  has been assembled to the developing frame  2  by way of the square spacers  44 , which will be described later. 
     (3) Blade Seal and Side Seals 
     The blade seal  45  is formed of an elastic material such as sponge, and has a general plate shape, generally rectangular in rear view and extending in the left-right direction, as illustrated in  FIG. 4 . The left and right end portions of the blade seal  45  are slightly bent downwards. The blade seal  45  comes into contact with the rear face of the blade seal supporting portion  87  of the cover frame  48  up to the rear face of the blade seal supporting portions  62  of the pair of side walls  50 . 
     By being assembled to the developing frame  2 , the blade seal  45  is supported by the blade seal supporting portion  87  by being clamped between the first clamping member  91  and blade member  93  of the layer thickness regulating blade  6 , and the rear face of the blade seal supporting portion  87 , which will be described in detail later. 
     Two side seals  46  are provided, one for each of the side seal supporting portions  63  at the left and right. The base portions of the side seals  46  are formed of an elastic member such as sponge or the like, and the surfaces are formed of a fiver material such as felt or cashmere as illustrated in  FIG. 3B . Each side seal  46  is curved to form a general C-shape in side view which is opened toward the upper rear direction. Each side seal  46  is disposed between a side seal supporting portions  63  of one of the pair of side walls  50  and an end portion of the rubber roller  14  of the developing roller  4  in the left-right direction, beneath the end portions of the blade seal  45  in the left-right direction. Note that the top portions of the side seals  46  and the end portions of the blade seal  45  in the left-right direction are in contact. 
     (4) Square Spacers 
     Two square spacers  44  are provided, corresponding to the left and right spacer fixing portions  58 . Each of the square spacers  44  has a spacer main unit  102  and a spacer boss  103  which is an example of a first engaged portion, as illustrated in  FIGS. 5A and 5B . 
     The spacer main unit  102  is generally formed as a square column, with a front face  104  and rear face  105  of the spacer main unit  102  following the vertical and left-right directions. The spacer main unit  102  has a second through hole  107  which is an example of a second through-hole, and an engaging groove  108 . 
     The second through hole  107  penetrates the generally middle portion of the spacer main unit  102  in the front-back direction in frontal view. The second through hole  107  has a generally circular shape in frontal view. The inner diameter of the second through hole  107  is slightly larger than the outer diameter of the frame boss  73  of the developing frame  2 . The inner perimeter of the second through hole  107  defines a second engaging portion  109 . 
     The engaging groove  108  is disposed at the lower front end of the spacer main unit  102 . The engaging groove  108  extends vertically as a recess toward the rear side, from the front face  104  of the spacer main unit  102 , to a depth of around ⅓ the front-back direction dimensions of the spacer main unit  102 . The top portion of the engaging groove  108  is opened so as to communicate with the second through hole  107 . The bottom portion of the engaging groove  108  is opened downwards. The dimensions of the engaging groove  108  in the left-right direction are generally the same as the inner diameter of the second through hole  107 , and slightly larger than the outer diameter of the frame boss  73 . That is to say, the engaging groove  108  is a groove which has been notched out such that the frame boss  73  can pass through the square spacer  44 . 
     The spacer boss  103  protrudes toward the rear from the rim of the second through hole  107  on the rear face  105  of the spacer main unit  102 , which is to say protrudes toward the layer thickness regulating blade  6  in a state where the layer thickness regulating blade  6  has been assembled to the developing frame  2  via the square spacers  44 , which will be described later. That is to say, when viewed from the rear, the second through hole  107  penetrates the square spacer  44  so as to be within the spacer boss  103 . The spacer boss  103  has a generally cylindrical shape. The outer diameter of the spacer boss  103  is slightly smaller than the inner diameter of the first through hole  96  of the layer thickness regulating blade  6 . The inner diameter of the spacer boss  103  is generally the same as the inner diameter of the second through hole  107 . Further, the dimensions of the spacer boss  103  in the front-back direction in the front-back direction are slightly shorter than the thickness of the first clamping member  91 . 
     4. Assembly State of the Layer Thickness Regulating Blade 
     The layer thickness regulating blade  6  is assembled to the developing frame  2  via two square spacers  44  by screws  111 , as illustrated in  FIGS. 3A and 3B . 
     More specifically, the layer thickness regulating blade  6  is disposed at the rear end portion of the developing frame  2  such that the front portion of the first clamping member  91  faces the blade seal supporting portion  87  upwards, and the rear portion of the first clamping member  91  faces the top portion of the blade seal supporting portion  87  toward the rear, as illustrated in  FIG. 1 . 
     The two square spacers  44  are each disposed between the corresponding clamping portion edge portion  95  of the layer thickness regulating blade  6 , and the cylindrical portion  72  of the corresponding spacer fixing portion  58 , as illustrated in  FIGS. 3A and 3B . That is to say, the square spacers  44  are disposed to the front of the layer thickness regulating blade  6 . 
     More specifically, the front face  104  of the spacer main unit  102  and the rear face  74  of the cylindrical portion  72  come into contact in the front-back direction, and the frame boss  73  of the spacer fixing portion  58  are inserted through the front portion of the second through hole  107  of the square spacer  44 . Accordingly, the outer perimeter face of the frame boss  73  is in contact with the inner perimeter face of the second through hole  107 , and engages the second engaging portion  109  in the radial direction of the frame boss  73 . Accordingly, movement of the square spacer  44  in the radial direction of the frame boss  73  is restricted with regard to the developing frame  2 . 
     Also, the rear face  105  of the spacer main unit  102  and the front face of the clamping portion edge portions  95  come into contact in the front-back direction, and the spacer boss  103  of the square spacer  44  is inserted through the first through hole  96  of the clamping portion edge portions  95 . Accordingly, the outer perimeter face of the spacer boss  103  is in contact with the inner perimeter face of the first through hole  96 , and engages the first engaging portions  98  in the radial direction of the spacer boss  103 . Accordingly, the layer thickness regulating blade  6  is restricted from moving in the radial direction of the spacer boss  103  with regard to the square spacer  44 , and movement in the radial direction of the spacer boss with regard to the developing frame  2  is restricted through the square spacer  44 . 
     Each screw  111  which is an example of a fixing member is screwed to the spacer fixing portion  58  through the first through hole  96  of the layer thickness regulating blade  6  and the second through hole  107  of the square spacer  44 . Thus, the layer thickness regulating blade  6  is fixed to the developing frame  2 . 
     At this time, the front face of the blade seal  45  comes into contact with the rear face of the blade seal supporting portion  87  of the cover frame  48  through the rear face of the blade seal supporting portions  62  of the pair of side walls  50 , and the rear face thereof comes into contact with the front face of the rear end portion of the first clamping member  91  and the front face of the blade member  93  as illustrated in  FIGS. 1 and 3B . In other words, the blade seal  45  is disposed at a position between the developing frame  2  and layer thickness regulating blade  6  different from the position where the square spacers  44  are disposed. 
     Accordingly, the blade seal  45  is compressed in the front-back direction. Note that the rear end portion of the compressed blade seal  45  is disposed further toward the rear as compared to the rear end portion of the spacer fixing portions  58 . 
     Also, the layer thickness regulating blade  6  is disposed further toward the front as compared to the developing roller  4 . The bottom portion of the blade member  93  of the layer thickness regulating blade  6  comes into contact with the upper front portion of the rubber roller  14  of the developing roller  4 . 
     The right abutting portion  97  of the first clamping member  91  of the layer thickness regulating blade  6  come into contact with the upper face of the inclined portion  80  of the right developing roller attaching portion  59 R, as illustrated in  FIG. 3A . The left end portion of the first clamping member  91  of the layer thickness regulating blade  6  is disposed within the notched groove  77  of the left developing roller attaching portion  59 L. While omitted from illustration, the left abutting portion  97  of the first clamping member  91  comes into contact with the bottom portion of the notched groove  77 . 
     Also omitted from illustration is that the bottom portions of the four screws  99  are situated within corresponding screw accommodating portions  88 . 
     5. Mounting/Detaching Layer Thickness Regulating Blade 
     (1) Detaching Layer Thickness Regulating Blade 
     This layer thickness regulating blade  6  is detached from the developing frame  2  by a worker. 
     To detach the layer thickness regulating blade  6  from the developing frame  2 , first, the two square spacers  44  are removed. 
     In order to remove the two square spacers  44 , two screws  111  are removed as illustrated in  FIGS. 6A and 6B . This disengages the fixation of the layer thickness regulating blade  6  as to the developing frame  2 . 
     Next, the worker turns the layer thickness regulating blade  6  counterclockwise from left side view, with the point of contact between the blade member  93  and the rubber roller  14  of the developing roller  4  as a fulcrum. 
     This distances the front face of the clamping portion edge portions  95  from the rear face  105  of the spacer main unit  102 . The engagements between the first engaging portions  98  of the clamping portion edge portions  95  and the spacer bosses  103  of the square spacers  44  are also released. 
     Next, the worker moves the square spacers  44  upwards, so that the front faces  104  thereof slide over the rear faces  74  of the spacer fixing portions  58 , as illustrated in  FIGS. 7A and 7B . The engaging grooves  108  of the square spacers  44  permit the frame bosses  73  of the spacer fixing portions  58  to pass by at this time. 
     Thus, the square spacers  44  are removed from the developing frame  2 . 
     The worker then moves the layer thickness regulating blade  6  forwards toward the blade seal supporting portion  87  as illustrated in  FIGS. 8A and 8B . At this time, the layer thickness regulating blade  6  can move forwards more than when the layer thickness regulating blade  6  is assembled, since the square spacers  44  have been detached. 
     Thus, the layer thickness regulating blade  6  compresses the blade seal  45  in the front-back direction more than in the state where the layer thickness regulating blade  6  is assembled. The screws  99  move forward within the screw accommodating portions  88  at this time. 
     This reduces the contact pressure of the blade member  93  of the layer thickness regulating blade  6  against the rubber roller  14  of the developing roller  4 . Alternatively, the blade member  93  of the layer thickness regulating blade  6  may be moved to where it is separated from the rubber roller  14  of the developing roller  4 . 
     The layer thickness regulating blade  6  is then moved upwards so as to be extracted from the developing frame  2  as indicated by the imaginary line in  FIG. 8B  and as illustrated in  FIG. 4 . 
     This competes detaching of the layer thickness regulating blade  6  from the developing frame  2 . 
     (2) Mounting the Layer Thickness Regulating Blade 
     The layer thickness regulating blade  6  is mounted to the developing frame  2  by performing the above-described procedures in reverse. 
     First, the worker assembles the layer thickness regulating blade  6  to the developing frame  2  while compressing the blade seal  45  against the blade seal supporting portion  62 . 
     Specifically, the layer thickness regulating blade  6  is assembled to the developing frame  2  such that the front portion of the first clamping member  91  approaches the upper face of the blade seal supporting portion  87 , in a state where the blade seal  45  is compressed against the blade seal supporting portion  62 , as illustrated in  FIGS. 8A and 8B . 
     This causes the right abutting portion  97  of the first clamping member  91  of the layer thickness regulating blade  6  to come into contact with the inclined portion  80  of the right developing roller attaching portion  59 R. The left end of the first clamping member  91  of the layer thickness regulating blade  6  is situated in the notched groove  77  of the left developing roller attaching portion  59 L, such that the left abutting portion  97  of the first clamping member  91  is in contact with the bottom portion of the notched groove  77 , though this is not illustrated. 
     Also omitted from illustration is that the bottom portions of the four screws  99  of the layer thickness regulating blade  6  are situated within corresponding screw accommodating portions  88 . 
     Accordingly, the blade member  93  faces the rear face of the blade seal supporting portion  62  and the rear face of the blade seal supporting portion  87 , so as to clamp the blade seal  45 . 
     The bottom portion of the blade member  93  comes into contact with the top portion of the rubber roller  14  of the developing roller  4 . 
     Next, the layer thickness regulating blade  6  is turned clockwise from left side view, with the point of contact between the blade member  93  and the rubber roller  14  of the developing roller  4  as a fulcrum, so that the dimension between the rear face  74  of the cylindrical portion  72  and the front face of the clamping portion edge portion  95  is greater than the front-back dimensions of the square spacer  44 , as illustrated in  FIGS. 7A and 7B . 
     The two square spacers  44  are then inserted from above to between the corresponding clamping portion edge portions  95  of the layer thickness regulating blade  6  and the corresponding spacer fixing portions  58  as illustrated in  FIGS. 6A and 6B . Specifically, the square spacers  44  are moved downwards, so that the front faces  104  of the spacer main units  102  slide over the rear faces  74  of the spacer fixing portions  58 , and thus attached to the developing frame  2 . 
     At this time, the frame bosses  73  of the spacer fixing portions  58  pass through the engaging grooves  108  of the square spacer  44  and come into contact with the front end portion of the inner peripheral face of the second through holes  107 . Thus, the frame bosses  73  of the spacer fixing portions  58  are engaged with the second engaging portions  109  of the square spacers  44 . 
     Next, the layer thickness regulating blade  6  is turned clockwise from left side view, with the point of contact between the blade member  93  and the rubber roller  14  of the developing roller  4  as a fulcrum as illustrated in  FIGS. 6A and 6B . 
     This results in the first through holes  96  of the layer thickness regulating blade  6  accepting the spacer bosses  103  of the square spacers  44 , and the front faces of the clamping portion edge portions  95  coming into contact with the rear faces  105  of the spacer main units  102 . Accordingly, the spacer bosses  103  of the square spacers  44  engage the first engaging portions  98  of the layer thickness regulating blade  6 . 
     The screws  111  are then screwed to the spacer fixing portions  58  through the first through holes  96  of the layer thickness regulating blade  6  and the second through holes  107  of the square spacers  44 , thus fixing the layer thickness regulating blade  6  to the developing frame  2 . 
     This completes mounting of the layer thickness regulating blade  6  to the developing frame  2 . 
     6. Advantages 
     (1) As illustrated in  FIG. 3B , the layer thickness regulating blade  6  of the developing cartridge  1  is assembled to the developing frame  2  via the square spacers  44 , by the spacer bosses  103  protruding toward the layer thickness regulating blade  6  engaging the first engaging portions  98  in the radial direction of the spacer bosses  103 . 
     Engagement of the layer thickness regulating blade  6  as to the spacer bosses  103  is released by detaching the square spacers  44  from the developing frame  2 , as illustrated in  FIG. 7B . 
     Accordingly, the layer thickness regulating blade  6  alone can be easily replaced, without having to remove the developing roller  4  from the developing cartridge  1  in order to release the engagement between the first engaging portions  98  and spacer bosses  103 , as illustrated in  FIG. 8B . 
     (2) Also, the first engaging portions  98  are the inner peripheral faces of the first through holes  96  penetrating the clamping portion edge portions  95  of the blade member  93  of the layer thickness regulating blade  6  in the front-back direction, so the spacer bosses  103  are engaged by being inserted into the first through holes  96 , as illustrated in  FIGS. 6A and 6B . 
     Accordingly, the layer thickness regulating blade  6  and square spacers  44  can be engaged with a simple configuration, as illustrated in  FIGS. 3A and 3B . 
     (3) The layer thickness regulating blade  6  is fixed to the developing frame  2  in the front-back direction by the screws  111 , through the first through holes  96  of the layer thickness regulating blade  6  and the second through holes  107  of the square spacers  44  as illustrated in  FIGS. 3A and 3B . 
     Accordingly, the relative movement of the layer thickness regulating blade  6  as to the developing frame  2  in the radial direction of the spacer bosses  103  is restricted by the engaging of the first engaging portions  98  and the spacer bosses  103  of the square spacers  44 , and relative movement in the front-back direction is restricted by the screws  111 . 
     Accordingly, the layer thickness regulating blade  6  can be securely fixed to the developing frame  2 . 
     (4) Also, the square spacers  44  are assembled to the developing frame  2  by the frame bosses  73  protruding toward the square spacer  44  engaging the second engaging portions  109  in the radial direction of the frame bosses  73 , as illustrated in  FIG. 3B . 
     Accordingly, the developing frame  2  is engaged with the square spacers  44 , and the square spacers  44  are engaged with the layer thickness regulating blade  6 , so the developing frame  2  supports the layer thickness regulating blade  6  via the square spacers  44 . 
     (5) The square spacers  44  are mounted to and detached from the developing frame  2  by the frame bosses  73  of the developing frame  2  moving so as to pass through the engaging grooves  108 , as illustrated in  FIGS. 5B and 7B . 
     Accordingly, the square spacers  44  along can be easily mounted/detached while the layer thickness regulating blade  6  and developing roller  4  remain assembled to the developing frame  2 . 
     (6) The blade seal  45  is disposed at a position between the developing frame  2  and the layer thickness regulating blade  6 , which is different from the position where the square spacers  44  are disposed, as illustrated in  FIGS. 3B and 4 . 
     Accordingly, toner leakage from the developing frame  2  can be suppressed, even though square spacers  44  to facilitate mounting/detaching of the layer thickness regulating blade  6  are disposed between the developing frame  2  and layer thickness regulating blade  6 . 
     (7) Also, the rear end portion of the blade seal  45  is disposed behind the rear end portions of the spacer fixing portions  58 , i.e., toward the layer thickness regulating blade  6  side, as illustrated in  FIG. 8B . Thus, when removing the layer thickness regulating blade  6  in a state where the square spacers  44  have been detached from the developing frame  2 , the layer thickness regulating blade  6  can be moved forward and the blade seal  45  pressed against the developing frame  2  side. 
     Accordingly, this moving the layer thickness regulating blade  6  forward so as to compress the blade seal  45  in the front-back direction enables contact pressure of the layer thickness regulating blade  6  against the developing roller  4  to be reduced, so the layer thickness regulating blade  6  can be detached more easily. 
     7. Second Embodiment 
     A second embodiment of the cartridge according to the present invention will be described with reference to  FIGS. 9A through 13B . Components in the second embodiment which are the same as those in the above-described first embodiment are denoted with the same reference numerals, and description thereof will be omitted. 
     (1) Details of Developing Cartridge According to Second Embodiment 
     A developing cartridge  120  which is an example of a cartridge includes a developing frame  121  which is an example of a housing, a layer thickness regulating blade  122  which is an example of a layer thickness restricting member, and a rotational spacer  123  which is an example of a spacer, as illustrated in  FIGS. 9A and 9B . 
     (1-1) Details of Developing Frame According to Second Embodiment 
     The developing frame  121  has a base frame  47  and a cover frame  48 . Each of the pair of side walls  50  of the base frame  47  has a spacer fixing portion  127  which is an example of a fixing portion, as illustrated in  FIG. 10 . 
     As illustrated in  FIGS. 9B and 10 , each spacer fixing portion  127  continues form and protrudes upwards from the upper end of the seal supporting member  56 . Each spacer fixing portion  127  has a base portion  128  a first extending portion  129 , a cylindrical portion  130 , a second extending portion  131 , a frame boss  132  which is an example of a second engaged portion, a pillar portion  133 , and a bulging portion  134 . 
     The base portion  128  is disposed at the bottom portion of the spacer fixing portion  127 . The base portion  128  has a general plate shape, generally rectangular in plan view, which protrudes upwards continuously from the top portion of the seal supporting unit  56 . The outer edge portions of the base portion  70  in the left-right direction are continuous with inner faces of the developing roller attaching portions  59 . 
     The first extending portion  129  is disposed at the front edge of the spacer fixing portion  127 , and has a plate form, generally rectangular in frontal view. The lower portion of the rear of the spacer fixing portion  127  is continuous with the front edge portion of the base portion  128 , and the outer edge portions of the first extending portions  129  in the left-right direction are continuous with inner faces of the developing roller attaching portions  59 . 
     The cylindrical portion  130  has a generally cylindrical shape extending in the front-back direction. The cylindrical portion  130  is embedded in the inward portion of the base portion  128  in the left-right direction. The front edge portion of the cylindrical portion  130  is connected to the inward portion in the left-right direction of the first extending portion  129  at the rear face of the first extending portion  129 . The rear edge portion of the cylindrical portion  130  is connected to the inward portion in the left-right direction of the second extending portion  131 . 
     The second extending portion  131  is adjacent behind the rear edge portion of the cylindrical portion  130 . The shape of the second extending portion  131  is the same as that of the first extending portion  129 . When projected in the front-back direction, the shapes of the second extending portion  131  and the first extending portion  129  are the same and overlaid. The bottom portion of the second extending portion  131  is continuous from the rear edge portion of the base portion  128 . 
     A rear face  135  of the second extending portion  131  extends in the vertical and left-right directions. The rear face  135  of the second extending portion  131  is situated at generally the same position of the rear portion of the blade seal supporting portion  62  of the seal supporting unit  56  in the front-back direction. 
     The second extending portion  131  has a through hole which, when projected in the front-back direction, overlays the inner perimeter of the cylindrical portion  130 , and has the same dimensions as the inner diameter of the cylindrical portion  130 . 
     The frame boss  132  protrudes rearwards from the inner peripheral edge of the through hole at the rear face  135  of the second extending portion  131 , that is to say toward the rotational spacer  123  in a state where the layer thickness regulating blade  122  is assembled to the developing frame  121  by the rotational spacers  123 . The frame boss  132  has a generally cylindrical shape, and is formed such that the outer diameter thereof is smaller than the outer diameter of the cylindrical portion  130 . The inner diameter of the frame boss  132  is generally the same as the inner diameter of the cylindrical portion  130 , and also the inner diameter of the through hole of the second extending portion  131 . The rear edge portion of the frame boss  132  is situated further toward the back than the rear face of the blade seal supporting portion  62  of the second phase-change unit  56 , as illustrated in  FIG. 9B . 
     Note that the cylindrical portion  130 , through hole of the second extending portion  131 , and frame boss  132  have screw threads formed on the inner peripheral faces thereof, omitted from illustration. 
     Each pillar portion  133  is disposed behind the outward edge portion of the second extending portion  131  in the left-right direction, as illustrated in  FIG. 10 . The pillar portion  133  protrudes backwards from the rear face of the second extending portion  131 , and has a generally square pillar form extending in the vertical direction. The other edge portions of the pillar portions  133  in the left-right direction are connected to the left and right inner faces of the developing roller attaching portions  59 . 
     The bulging portion  134  is disposed beneath the second extending portion  131 . The bulging portion  134  protrudes backwards farther than the second extending portion  131 , and has a generally rectangular shape in rear view. The rear edge portion of the bulging portion  134  is situated at generally the same position as the rear edge portion of the pillar portion  133  in the front-back direction. The bottom portion of the bulging portion  134  is continuous with the tip portion of the blade seal supporting portion  62 , as illustrated in  FIG. 9B . 
     The right spacer fixing portion  127  has a positioning portion  136  as illustrated in  FIG. 10 . 
     The positioning portion  136  continues from the right edge portion of the bulging portion  134  and protrudes backwards. The bottom portion of the positioning portion  136  is continuous with the upper face of the inclined portion  80  of the right developing roller attaching portion  59 R. The right edge portion of the positioning portion  136  is continuous with the right face of the top portion  79  of the right developing roller attaching portion  59 R. The upper face of the positioning portion  136  extends in the front-back and left-right directions. The left face of the positioning portion  136  extends in the vertical and front-back directions. 
     (1-2) Details of Layer Thickness Regulating Blade According to Second Embodiment 
     The clamping portion edge portions  95  of the first clamping member  91  of the layer thickness regulating blade  122  each have a receiving groove  140  which is an example of a first through-hole, as illustrated in  FIG. 10 . The first clamping member  91  of the layer thickness regulating blade  122  also has two abutting portions  141 . 
     Each receiving groove  140  has a generally U-shaped form opened upwards, recessed downwards from the upper edge of the clamping portion edge portion  95 . The dimensions of the receiving groove  140  in the left-right direction are slightly larger than the outer diameter of a spacer boss  145  of the rotational spacer  123 , which will be described later. That is to say, the receiving grooves  140  are grooves which have been notched out in the layer thickness regulating blade  122  so as to allow passage of the spacer bosses  145 . The inner perimeter face of the receiving groove  140  defines a first engaging portion  142 . 
     The two abutting portions  141  have each been formed by notching out the respective outer edge portions of the bottom of the first clamping member  91  in generally rectangular shapes in frontal view. The distance between the inner edge portions of the two abutting portions  141  in the left-right direction is generally the same as the length of the blade member  93  in the left-right direction. 
     (1-3) Details of Rotational Spacer According to Second Embodiment 
     Two rotational spacers  123  are provided, corresponding to the two spacer fixing portions  127 . The two rotational spacers  123  are each detachably mounted to the developing frame  121 . Note that in the following description, reference to directions regarding the rotational spacers  123  will be made based on the directions of the rotational spacers  123  as illustrated in  FIG. 10 . The two rotational spacers  123  are symmetrical in form. Accordingly, description will be made in detail regarding the right rotational spacer  123 , and description of the left rotational spacer  123  will be omitted. 
     The rotational spacer  123  integrally includes a spacer disc portion  144 , the spacer boss  145  which is an example of a first engaged portion, and a spacer half-ring portion  146  as illustrated in  FIGS. 11A and 11B . 
     The spacer disc portion  144  has a general disc shape extending in the vertical and left-and-right directions. A rear face  148  of the spacer disc portion  144  extends in the vertical and left-and-right directions. The spacer disc portion  144  includes a large-diameter portion  150 , a small-diameter portion  151 , and a spacer hole  149  which is an example of a second through-hole. 
     The large-diameter portion  150  makes up the upper half of the spacer disc portion  144 . The large-diameter portion  150  has a half-circle shape in rear view, which bulges upwards. The large-diameter portion  150  also includes a first knob portion  152  which is an example of a knob portion. 
     The first knob portion  152  protrudes to the left from the left edge portion of the large-diameter portion  150 , which is to say outwards in the radial direction of the large-diameter portion  150 . The first knob portion  152  has a generally rectangular shape in rear view. 
     The small-diameter portion  151  makes up the lower half of the spacer disc portion  144 . The small-diameter portion  151  continues from the lower face of the large-diameter portion  150  and protrudes downwards. The small-diameter portion  151  has a half-circle shape in rear view, and shares the same center axial line with the large-diameter portion  150 , but is smaller in outer diameter as compared to the large-diameter portion  150 . The small-diameter portion  151  also includes a second knob portion  153  which is an example of a knob portion. 
     The second knob portion  153  protrudes downwards from the bottom portion of the small-diameter portion  151 , i.e., outwards in the radial direction of the small-diameter portion. The second knob portion  153  has a generally rectangular shape in rear view. 
     The spacer hole  149  penetrates the spacer disc portion  144  in the front-back direction, along the center axial line of the large-diameter portion  150  and small-diameter portion  151 . The spacer hole  149  has a generally circular shape in rear view. The inner diameter of the spacer hole  149  is slightly larger than the inner diameter of the frame boss  132 . 
     The spacer boss  145  protrudes rearwards from the inner peripheral edge of the spacer hole  149  at the rear face  148  of the spacer disc portion  144 , that is to say toward the layer thickness regulating blade  122  in a state where the layer thickness regulating blade  122  is assembled to the developing frame  121  by the rotational spacer  123 . That is to say, when viewed from the rear, the spacer hole  149  penetrates the rotational spacer  123  so as to be within the spacer boss  145 . The spacer boss  145  has a generally cylindrical shape, and is formed such that the outer diameter thereof is smaller than the left-right direction dimensions of the receiving groove  140  of the layer thickness regulating blade  122 . The inner diameter of the spacer boss  145  is generally the same as the inner diameter of the spacer hole  149 . The dimensions of the spacer boss  145  in the front-back direction are slightly shorter than the thickness of the first clamping member  91 . 
     The spacer half-ring portion  146  protrudes forwards from the front face of the large-diameter portion  150  of the spacer disc portion  144 . The spacer half-ring portion  146  has a general half-ring shape with the lower side opened, and shares the center axial line with the large-diameter portion  150  and the small-diameter portion  151 . The outer diameter of the spacer half-ring portion  146  is generally the same as the outer diameter of the large-diameter portion  150  of the spacer disc portion  144 . That is to say, the outer perimeter face of the spacer half-ring portion  146  is flush with the outer perimeter face of the large-diameter portion  150 . The inner diameter of the spacer half-ring portion  146  is slightly larger than the outer diameter of the frame boss  132  of the spacer fixing portion  127 . Note that the inner perimeter face of the spacer half-ring portion  146  defines a second engaging portion  154 . The front face  155  of the spacer half-ring portion  146  extends in the vertical and left-right directions. 
     (2) Assembly State of Layer Thickness Regulating Blade 
     The layer thickness regulating blade  122  is assembled to the developing frame  121  via two rotational spacers  123  by screws  111 , as illustrated in  FIGS. 9A and 9B . 
     Specifically, the layer thickness regulating blade  122  is disposed at the rear end portion of the developing frame  121  such that the front portion of the first clamping member  91  faces the blade seal supporting portion  87  upwards, and the rear portion of the first clamping member  91  faces the top portion of the blade seal supporting portion  87  toward the rear, in the same way as with the first embodiment. 
     The front face of the layer thickness regulating blade  122  at the outer edge portions of the clamping portion edge portions  95  in the left-right direction is in contact with the front faces of the pillar portions  133  of the spacer fixing portions  127 . 
     The front face of the layer thickness regulating blade  122  at the outer edge portions of the first clamping member  91  in the left-right direction is also in contact with the front faces of the bulging portions  134  of the spacer fixing portions  127 . 
     The two rotational spacers  123  are each disposed between the corresponding clamping portion edge portion  95  of the layer thickness regulating blade  122 , and the second extending portion  131  of the corresponding spacer fixing portion  127 . The second knob portions  153  of the rotational spacer  123  are facing upwards. 
     More specifically, at each of the left and right sides, the front face  155  of the spacer half-ring portion  146  and rear face  135  of the second extending portion  131  come into contact in the front-back direction, and the frame boss  132  of the spacer fixing portion  127  comes into contact with the inner peripheral face of the spacer half-ring portion  146  of the rotational spacer  123  from above. That is to say, the outer peripheral face of the frame boss  132  is in contact with the inner peripheral face of the spacer half-ring portion  146 , and engages the second engaging portion  154  in the radial direction of the frame boss  132 . Accordingly, movement of the rotational spacer  123  in the radial direction of the frame boss  132  is restricted respective to the developing frame  121 . The position of the rotational spacer  123  at this time is defined as a detaching restriction position where detachment from between the developing frame  121  and layer thickness regulating blade  122  is restricted. 
     The rear face  148  of the spacer disc portion  144  and the front face of the clamping portion edge portion  95  are in contact in the front-back direction, and the spacer boss  145  of the rotational spacer  123  is accepted within the receiving groove  140  of the clamping portion edge portion  95 . That is to say, the outer peripheral face of the spacer boss  145  is in contact with the inner peripheral face of the receiving groove  140 , and engages the first engaging portion  142  in the radial direction of the spacer boss  145 . Accordingly, movement of the layer thickness regulating blade  122  in the radial direction of the spacer boss  145  is restricted respective to the rotational spacer  123 , and movement of the layer thickness regulating blade  122  in the radial direction of the spacer boss  145  is restricted respective to the developing frame  121  by way of the rotational spacer  123  situated at the detaching restriction position. 
     The screws  111  are screwed to the spacer fixing portion  127 , through the receiving grooves  140  of the layer thickness regulating blade  122 , and spacer holes  149  of the rotational spacers  123 . 
     At this time, the front face of the blade seal  45  comes into contact with the rear face of the blade seal supporting portion  87  of the cover frame  48  through the rear face of the blade seal supporting portions  62  of the pair of side walls  50 , and the rear face thereof comes into contact with the front face of the rear end portion of the first clamping member  91  and the front face of the blade member  93 , in the same way as with the first embodiment. In other words, the blade seal  45  is disposed at a position between the developing frame  121  and layer thickness regulating blade  122  different from the position where the rotational spacers  123  are disposed. 
     Accordingly, the blade seal  45  is compressed in the front-back direction. Note that the rear end portion of the compressed blade seal  45  is disposed further toward the rear as compared to the rear end portion of the spacer fixing portions  127 . 
     The bottom portion of the blade member  93  of the layer thickness regulating blade  122  comes into contact with the upper front portion of the rubber roller  14  of the developing roller  4 . 
     The right abutting portion  141  of the first clamping member  91  of the layer thickness regulating blade  122  come into contact with the upper face and left face of the positioning portion  136  of the right spacer fixing portion  127 , as illustrated in  FIG. 9A . The left end portion of the first clamping member  91  of the layer thickness regulating blade  122  is disposed within the notched groove  77  of the left developing roller attaching portion  59 L. While omitted from illustration, the left abutting portion  141  of the first clamping member  91  comes into contact with the bottom portion of the notched groove  77 . 
     Also omitted from illustration is that the bottom portions of the four screws  99  are situated within corresponding screw accommodating portions  88 , in the same way as with the first embodiment. 
     (3) Mounting/Detaching Layer Thickness Regulating Blade According to Second Embodiment 
     (3-1) Detaching Layer Thickness Regulating Blade According to Second Embodiment 
     This layer thickness regulating blade  122  is detached from the developing frame  121  by a worker. 
     To detach the layer thickness regulating blade  122  from the developing frame  121 , first, the two rotational spacers  123  are removed. 
     In order to remove the two rotational spacers  123 , the two screws  111  are removed. This disengages the fixation of the layer thickness regulating blade  122  as to the developing frame  121 . 
     The operations of the right rotational spacer  123  will be described in the following description. The left rotational spacer  123  is removed by operations horizontally symmetrical to the right rotational spacer  123  so description thereof will be omitted. 
     The worker next holds the second knob portion  153  positioned above the rotational spacer  123  situated at the detaching restriction position, and rotates the right rotational spacer  123  in the clockwise direction in rear view. The position of the second knob portion  153  thus moves from above the rotational spacer  123  to the left of the rotational spacer  123 , and the position of the first knob portion  152  moves from the right of the rotational spacer  123  to above the rotational spacer  123 . 
     The worker then releases the second knob portion  153  and holds the first knob portion  152 , and further rotates the rotational spacer  123  in the clockwise direction in rear view. 
     Thus, the position of the first knob portion  152  moves from above the rotational spacer  123  to the left of the rotational spacer  123 , and the position of the second knob portion  153  moves from the left of the rotational spacer  123  to below the rotational spacer  123 , as illustrated in  FIGS. 12A and 12B . 
     Accordingly, the rotational spacer  123  is rotated 180 degrees. Rotating the rotational spacer  123  180 degrees causes the inner perimeter face of the spacer half-ring portion  146  to come into contact with the outer perimeter face of the frame boss  132  at the upper portion thereof. The position of the rotational spacer  123  at this time is defined as a detachable position, where the rotational spacer  123  can be detached from between the developing frame  121  and the layer thickness regulating blade  122 . That is to say, the rotational spacer  123  is moved by rotated from the detaching restriction position to the detachable position. 
     Next, the rotational spacer  123  at the detachable position is moved upwards by the front face  155  of the spacer half-ring portion  146  sliding over the rear face  135  of the second extending portion  131 , and the rear face  148  of the spacer disc portion  144  sliding over the front face of the clamping portion edge portion  95  of the layer thickness regulating blade  122 , as illustrated in  FIGS. 13A and 13B . 
     At this time, the spacer boss  145  of the rotational spacer  123  passes upwards through the receiving groove  140  of the clamping portion edge portion  95  of the first clamping member  91 . This distances the outer perimeter face of the spacer boss  145  from the receiving groove  140  of the layer thickness regulating blade  122 , and also the engagement between the first engaging portion  142  of the layer thickness regulating blade  122  and the rotational spacer  123  is released. 
     The rotational spacer  123  moving upwards as to the frame boss  132  of the spacer fixing portion  127  causes the inner perimeter face of the spacer half-ring portion  146  of the rotational spacer  123  and the outer perimeter face of the frame boss  132  to be distanced, and the engagement between the second engaging portion  154  of the rotational spacer  123  and the outer perimeter of the frame boss  132  is released. 
     The layer thickness regulating blade  122  is then moved upwards so as to be extracted from the developing frame  121  as indicated by the imaginary line in  FIG. 13B  and as illustrated in  FIG. 10 . 
     This completes detaching of the layer thickness regulating blade  122  from the developing frame  121 . 
     (3-2) Mounting the Layer Thickness Regulating Blade According to the Second Embodiment 
     The layer thickness regulating blade  122  is mounted to the developing frame  121  by performing the above-described procedures in reverse. 
     First, the layer thickness regulating blade  122  to the rear portion of the developing frame  121  from above, as illustrated in  FIGS. 13A and 13B . 
     This brings the right abutting portion  141  of the first clamping member  91  of the layer thickness regulating blade  122  into contact with the upper face and left face of the positioning portion  136  of the right spacer fixing portion  127 . Also, the left end portion of the first clamping member  91  of the layer thickness regulating blade  122  is situated within the notched groove  77 , and though omitted from illustration the left abutting portion  141  of the first clamping member  91  is brought into contact with the bottom portion of the notched groove  77 . 
     Also omitted from illustration is that the bottom portions of the four screws  99  of the layer thickness regulating blade  122  are accepted by corresponding screw accommodating portions  88 , and the blade member  93  faces the rear face of the blade seal supporting portion  62  across the blade seal  45 . 
     The layer thickness regulating blade  122  is thus positioned as to the housing. 
     And the bottom portion of the blade member  93  comes into contact with the top portion of the rubber roller  14  of the developing roller  4 . 
     The two rotational spacers  123  are then inserted between the corresponding clamping portion edge portions  95  of the layer thickness regulating blade  122  and the corresponding spacer fixing portions  127 , as illustrated in  FIGS. 12A and 12B . 
     The operations of the right rotational spacer  123  will be described in the following description. The left rotational spacer  123  is attached by operations horizontally symmetrical to the right rotational spacer  123  so description thereof will be omitted. 
     At each of the two rotational spacers  123 , the first knob portion  152  is situated on the inward side of the rotational spacer  123  in the left-right direction, and the second knob portion  153  is situated below the rotational spacer  123 , as illustrated in  FIGS. 13A and 13B . 
     The rotational spacer  123  moves downward with the front face  155  of the spacer half-ring portion  146  sliding over the rear face  135  of the spacer fixing portion  127 , and the rear face  148  of the spacer disc portion  144  sliding over the front face of the clamping portion edge portions  95  of the layer thickness regulating blade  122 . 
     At this time, the spacer boss  145  of the rotational spacer  123  passes downward through the receiving groove  140  of the clamping portion edge portions  95  of the first clamping member  91 , so that the bottom portion of the outer perimeter face of the spacer boss  145  and the receiving groove  140  of the layer thickness regulating blade  122  come into contact, and the spacer boss  145  of the rotational spacer  123  and the first engaging portion  142  of the layer thickness regulating blade  122  are engaged. 
     The rotational spacer  123  is also assembled as to the frame boss  132  of the spacer fixing portion  127  from above, whereby the inner perimeter face of the spacer half-ring portion  146  of the rotational spacer  123  and the outer perimeter face of the top portion of the frame boss  132  come into contact. That is to say, the rotational spacer  123  is situated at the detachable position. 
     Next, the worker next holds the first knob portion  152  positioned to the left of the rotational spacer  123  situated at the detachable position, and rotates in the counterclockwise direction in rear view. The position of the first knob portion  152  thus moves from to the left of the rotational spacer  123  to above the rotational spacer  123 , and the position of the second knob portion  153  moves from below the rotational spacer  123  to the left of the rotational spacer  123 . 
     The worker then releases the first knob portion  152  and holds the second knob portion  153 , and further rotates the rotational spacer  123  in the counter clockwise direction in rear view. 
     Thus, the position of the second knob portion  153  moves from the left of the rotational spacer  123  to above the rotational spacer  123 , and the position of the first knob portion  152  moves from above the rotational spacer  123  to the right of the rotational spacer  123 . 
     Accordingly, the rotational spacer  123  is rotated 180 degrees. Rotating the rotational spacer  123  180 degrees causes the inner perimeter face of the spacer half-ring portion  146  to come into contact with the outer perimeter face of the frame boss  132  at the lower portion thereof. The rotational spacer  123  is thus rotated and moved from the detachable position to the detaching restricting position, and the frame boss  132  is engaged with the second engaging portion  154  of the rotational spacer  123 . 
     The screws  111  are then screwed to the spacer fixing portion  127  through the receiving grooves  140  of the layer thickness regulating blade  122  and the spacer holes  149  of the rotational spacers  123  as illustrated in  FIGS. 9A and 9B , thus fixing the layer thickness regulating blade  122  to the developing frame  121 . 
     This completes mounting of the layer thickness regulating blade  122  to the developing frame  121 . 
     (4) Advantages of the Second Embodiment 
     (4-1) According to the developing cartridge  120 , the rotational spacers  123  are moved so that the spacer bosses  145  of the rotational spacers  123  pass through the receiving grooves  140  of the layer thickness regulating blade  122  as illustrated in  FIGS. 10 and 12B , so the rotational spacers  123  can be easily mounted to and detached from the layer thickness regulating blade  122 . 
     Consequently, the rotational spacers  123  alone can be easily mounted and detached with the layer thickness regulating blade  122  and developing roller  4  remaining assembled to the developing frame  121 . 
     (4-2) Also, according to the developing cartridge  120 , the rotational spacers  123  can be easily switched between a detachable position where detachable from between the developing frame  121  and layer thickness regulating blade  122 , and a detaching restricting position where detaching from between the developing frame  121  and layer thickness regulating blade  122  is restricted, by rotating the rotational spacers  123 , as illustrated in  FIGS. 9B and 12B . 
     (4-3) According to the developing cartridge  120 , the rotational spacers  123  can be easily rotated by using the first knob portion  152  and the second knob portion  153 , as illustrated in  FIGS. 9A and 13A .