Abstract:
A cartridge includes: a frame; a rotation body; a driving force transmission unit; and a moving member. The rotation body is provided at the frame and rotatable about its rotation axis relative to the frame. The driving force transmission unit is provided at the frame and transmits an external driving force to the rotation body. The moving member is irreversibly movable to one of a covered position and an exposed position by the external driving force transmitted through the driving force transmission unit. The moving member covers at least a portion of the driving force transmission unit when the moving member is at the covered position. The moving member exposes the driving force transmission unit when the moving member is at the exposed position. The exposed position provides an exposing degree greater than that at the covered position.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority from Japanese Patent Application No. 2011-288490 filed Dec. 28, 2011. The entire content of the priority application is incorporated herein by reference. 
       TECHNICAL FIELD 
       [0002]    The present invention relates to a cartridge to be used in an electro-photographic type image forming apparatus, and to an image forming apparatus provided with the cartridge. 
       BACKGROUND 
       [0003]    As an electro-photographic type image forming apparatus, a printer including a photosensitive body and a developing cartridge configured to supply toner to the photosensitive body is known. 
         [0004]    A conventional printer is provided with a detection device for detecting information of the developing cartridge assembled therein, for example, for detecting whether or not the assembled developing cartridge is a brand new cartridge. 
         [0005]    Japanese Patent Application Publication No. 2006-267994 proposes a laser printer that detects rotation of a detection gear provided in a developing cartridge using an actuator provided in a main casing and that determines information on the developing cartridge based on a detection result. 
         [0006]    In the above laser printer, the detection gear has an abutment protrusion corresponding to the information on the developing cartridge. The detection gear is rotated by a predetermined driving amount after assembly of the developing cartridge to the main casing. At this time, the abutment protrusion abuts on the actuator, allowing the rotation of the detection gear to be detected by the actuator. 
       SUMMARY 
       [0007]    However, in the laser printer described above, the developing cartridge only has the detection gear for allowing the main casing to detect the information on the developing cartridge. 
         [0008]    Additionally, substantially the entire part of the detection gear is covered by a gear cover, which lowers visibility of the detection gear from outside the apparatus. 
         [0009]    Therefore, a user who does not have knowledge of the new cartridge detection device has a difficulty in determining whether the developing cartridge is a new one or a used one. 
         [0010]    It is therefore an object of the present invention to provide a cartridge allowing a user to easily determine whether the cartridge is unused or used and an image forming apparatus provided with the cartridge. 
         [0011]    In order to attain the above and other objects, the present invention provides a cartridge including: a frame; a rotation body; a driving force transmission unit; and a moving member. The frame is configured to accommodate therein developing agent. The rotation body has a rotation axis extending in a predetermined direction. The rotation body is provided at the frame and rotatable about the rotation axis relative to the frame. The driving force transmission unit is provided at the frame and configured to transmit an external driving force to the rotation body. The moving member is configured to be irreversibly moved to one of a covered position and an exposed position by the external driving force transmitted through the driving force transmission unit. The moving member covers at least a portion of the driving force transmission unit when the moving member is at the covered position. The moving member exposes the driving force transmission unit when the moving member is at the exposed position. The exposed position provides an exposing degree greater than that at the covered position. 
         [0012]    When the moving member is at the covered position, there may be no exposing degree. In other words, when the moving member is at the covered position, the moving member may cover the driving force transmission unit in its entirety. 
         [0013]    According to another aspect, the present invention provides an image forming apparatus including: a main casing; and a cartridge. The cartridge is detachable from and attachable to the main casing. The cartridge includes: a frame; a rotation body; a driving force transmission unit; and a moving member. The frame is configured to accommodate therein developing agent. The rotation body has a rotation axis extending in a predetermined direction. The rotation body is provided at the frame and rotatable about the rotation axis relative to the frame. The driving force transmission unit is provided at the frame and configured to transmit a driving force from the main casing to the rotation body. The moving member is configured to be irreversibly moved to one of a covered position and an exposed position by the driving force transmitted through the driving force transmission unit. The moving member covers at least a portion of the driving force transmission unit when the moving member is at the covered position. The moving member exposes the driving force transmission unit when the moving member is at the exposed position. The exposed position provides an exposing degree greater than that at the covered position. The main casing includes: a detection unit; and a judgment unit. The detection unit is configured to detect a movement of the moving member. The judgment unit is configured to judge a condition of the cartridge based on a detection of the detection unit. 
         [0014]    The condition of the cartridge judged by the judgment unit in the present invention implies a usage state of the cartridge whether the cartridge is new or used, types of the cartridge, a remaining amount of toner accommodated in the cartridge, and a position of agitation blades, for example. 
         [0015]    Further, when the moving member is at the covered position, there may be no exposing degree. That is, when the moving member is at the covered position, the moving member may cover the driving force transmission unit in its entirety. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    In the drawings; 
           [0017]      FIG. 1  is a cross-sectional view of a printer according to one embodiment of the present invention; 
           [0018]      FIG. 2  is a perspective view of a developing cartridge accommodated in the printer shown in  FIG. 1  as viewed from a diagonally front left side; 
           [0019]      FIG. 3  is an exploded perspective view of the developing cartridge of  FIG. 2 ; 
           [0020]      FIG. 4  is a left side view of a cartridge frame of the developing cartridge of  FIG. 3 ; 
           [0021]      FIG. 5  is a left side view of the cartridge frame of  FIG. 4  at which a gear train is disposed; 
           [0022]      FIG. 6  is a perspective view of an agitator gear of the developing cartridge of  FIG. 3  as viewed from a left side; 
           [0023]      FIG. 7  is a perspective view of a gear cover of the developing cartridge of  FIG. 3  as viewed from a diagonally rear right side; 
           [0024]      FIG. 8  is a perspective view of a shutter of the developing cartridge of  FIG. 3  as viewed from a diagonally rear right side; 
           [0025]      FIG. 9  is a view for description of relative positional relationship among the gear cover, the shutter, and the agitator gear; 
           [0026]      FIGS. 10A and 10B  are views for description of movement of the shutter; and in which  FIG. 10A  shows a state where the shutter is at a covered position, and  FIG. 10B  shows a state where the shutter is at the exposed position; 
           [0027]      FIGS. 11A and 11B  are views for description of a new cartridge detecting operation; and in which  FIG. 11A  shows a state where a detection unit is at a new cartridge detection position and the shutter is at the covered position, and  FIG. 11B  shows a state where the detection unit is at the new cartridge detection position and the shutter is at the exposed position; 
           [0028]      FIGS. 12A and 12B  are views for description of a cartridge type detecting operation; and in which  FIG. 12A  shows a state where the detection unit is at a cartridge type detection position and a right end portion of a probe is in abutment with an agitator gear, and  FIG. 12B  shows a state where the detection unit is at the cartridge type detection position and the right end portion of the probe is inside a detected opening formed in the agitator gear; 
           [0029]      FIGS. 13A and 13B  are views for description of detection by an empty sensor unit; and in which  FIG. 13A  shows a toner amount detection for a remaining amount of toner in a toner chamber, and  FIG. 13B  shows a position detection of an agitator; 
           [0030]      FIG. 14A  is a perspective view of an agitator gear according to one modification; in which the agitator gear is formed with two detected openings; and 
           [0031]      FIG. 14B  is a perspective view of an agitator gear according to another modification; in which the agitator gear is provided with two detected protrusions. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]    A printer as an image forming apparatus according to one embodiment of the present invention will be described with reference to  FIGS. 1 through 13A . Throughout the specification, the terms “upward”, “downward”, “upper”, “lower”, “above”, “below”, “beneath”, “right”, “left”, “front”, “rear” and the like will be used assuming that the image forming apparatus is disposed in an orientation in which it is intended to be used. More specifically, in  FIG. 1  a left side and a right side are a front side and a rear side, respectively. 
         [0033]    1. Overall Structure of Color Printer 
         [0034]    Referring to  FIG. 1 , the printer  1  is a horizontal direct tandem type color printer. The printer  1  includes a main casing  2  having a generally box shape. The main casing  2  has an upper portion provided with a top cover  4  which can be opened or closed for opening and closing an opening  3 . The top cover  4  has a rear end portion pivotally movably supported to the main casing  2 . The printer  1  includes four process cartridges  5 . 
         [0035]    Each process cartridge  5  is detachable from and attachable to the main casing  2 . When mounted, the process cartridges  5  are juxtaposedly arrayed in the frontward/rearward direction at intervals within the main casing  2 . The four process cartridges  5  corresponds to four colors different from each other (black, yellow, magenta, and cyan), respectively. 
         [0036]    Each process cartridge  5  includes a drum cartridge  6  and a developing cartridge  7  detachable from and attachable to the drum cartridge  6 . 
         [0037]    Each drum cartridge  6  has a photosensitive drum  8 . The photosensitive drum  8  is cylindrical in shape and extends in a lateral direction (rightward/leftward direction), and is rotatably supported to a frame of the drum cartridge  6 . 
         [0038]    Further, the drum cartridge  6  has a scorotron charger  9  and an LED unit  10 . The scorotron charger  9  is positioned diagonally above and rearward of the photosensitive drum  8 , and confronts the photosensitive drum  8 . The LED unit  10  is positioned above the photosensitive drum  8 , and confronts the photosensitive drum  8 . 
         [0039]    The developing cartridge  7  has a developing roller  11  and a supply roller  12  adapted to supply toner to the developing roller  11 . 
         [0040]    The developing roller  11  has a rotation shaft extending in the lateral direction. The developing roller  11  is rotatably supported in a rear end portion of the developing cartridge  7  such that each lateral end portion of the rotation shaft is rotatably supported to each side wall  33  of a cartridge frame  31  ( FIG. 2 , described later) of the developing cartridge  7 . A rear edge of the developing roller  11  is exposed to an outside through a rear edge of the developing cartridge  7  and contacts the corresponding photosensitive drum  8  from an upper front side thereof. 
         [0041]    The supply roller  12  has a rotation shaft extending in the lateral direction. The supply roller  12  is rotatably supported in the developing cartridge  7  such that each lateral end portion of the rotation shaft is rotatably supported to each side wall  33  of the cartridge frame  31  (described later). The supply roller  12  is disposed diagonally above and frontward of the developing roller  11  and in contact therewith. 
         [0042]    The developing cartridge  7  is provided with a layer thickness regulation blade  13 , a toner chamber  14  and an agitator  15 . The layer thickness regulation blade  13  is adapted to regulate a thickness of a toner layer supplied to the developing roller  11 . The toner chamber  14  is positioned above the developing roller  11  and the supply roller  12 . The toner chamber  14  accommodates toner therein. 
         [0043]    The agitator  15  is provided in the toner chamber  14  for agitating the toner. The agitator  15  includes an agitator shaft  16  extending in the lateral direction and agitation blades  17  extending radially toward an inner circumferential surface of the toner chamber  14  from the agitator shaft  16 . The agitator  15  is adapted to rotate about an axis A ( FIG. 3 ) of the agitator shaft  16 . 
         [0044]    Toner accommodated in the toner chamber  14  is subjected to tribo-electric charging to have a positive polarity between the supply roller  12  and the developing roller  11 . The toner is carried on an outer peripheral surface of the developing roller  11  in a form of a thin toner layer having a uniform thickness by the layer thickness regulation blade  13 . 
         [0045]    After an outer peripheral surface of the photosensitive drum  8  is uniformly charged by the scorotron charger  9 , the surface is exposed to light by the LED unit  10  based on a predetermined image data to form an electrostatic latent image on the surface. Then, a visible toner image (developing agent image) corresponding to the electrostatic latent image is formed on the outer peripheral surface of the photosensitive drum  8  by supplying toner carried on the developing roller  11  to the corresponding photosensitive drum  8 . 
         [0046]    A sheet cassette  18  is provided at a bottom portion of the main casing  2  for accommodating sheets P therein in a stacked state. Each sheet P accommodated in the sheet cassette  18  is passed through a U-shaped passage and is conveyed diagonally upward and rearward to a position between the photosensitive drum  8  and a conveyor belt  19  at a prescribed timing by various rollers. Then, each sheet P is conveyed rearward by the conveyer belt  19  at a position between each photosensitive drum  8  and each transfer roller  20 . At this time, the toner image is transferred onto the sheet P. 
         [0047]    The sheet P onto which the toner image has been transferred is then conveyed to a fixing unit provided downstream of the conveyer belt  19 . The fixing unit includes a heat roller  21  and a pressure roller  22 . The toner image is thermally fixed to the sheet P when the sheet P passes through the heat roller  21  and the pressure roller  22 . The sheet P carrying the toner image is then conveyed through an U-shaped passage frontward and upward, and is discharged onto a discharge tray  23  provided at the top cover  4 . 
         [0048]    2. Details of Developing Cartridge 
         [0049]    As shown in  FIGS. 2 and 3 , the developing cartridge  7  includes a cartridge frame  31  and a drive unit  32  positioned at a left side of the cartridge frame  31 . 
         [0050]    When referring to the directions in the description of the developing cartridge  7 , the terms “upward”, “downward”, “upper”, “lower”, “above”, “below”, “beneath”, “right”, “left”, “front”, “rear” and the like will be used assuming that the developing cartridge  7  is detached from the main casing  2  and placed on a horizontal plane. Specifically, a side on which the developing roller  11  is disposed is defined as the rear side, and a side on which the layer thickness regulation blade  13  is disposed is defined as the upper side. 
         [0051]    (1) Cartridge Frame 
         [0052]    The cartridge frame  31  extends in the lateral direction and is generally box shaped, as shown in  FIGS. 2 and 3 . The cartridge frame  31  includes the pair of side walls  33 , a front wall  34 , a lower wall  35  and an upper wall  36 . The pair of side walls  33  includes a left side wall  33 L and a right side wall  33 R. 
         [0053]    Each side wall  33  extends in the frontward/rearward direction and in the vertical direction, and is generally rectangular shaped in a side view. The pair of side walls  33  is spaced away from each other in the lateral direction. The left side wall  33 L is formed with an agitator shaft exposure hole  37 , and a detection window  38 , as shown in  FIG. 3 . 
         [0054]    The agitator shaft exposure hole  37  is formed for exposing the agitator shaft  16  to the outside therethrough. The agitator shaft exposure hole  37  is positioned at a generally center portion of the left side wall  33 L in the frontward/rearward direction and is generally circular shaped in a side view. The agitator shaft exposure hole  37  is penetrated through a thickness of the left side wall  33 L and has a diameter greater than an outer diameter of a left end portion of the agitator shaft  16 . The left end portion of the agitator shaft  16  extends through the agitator shaft exposure hole  37  and protrudes laterally outward from the left side wall  33 L. 
         [0055]    The detection window  38  is formed in the left side wall  33 L and positioned adjacent to the agitator shaft exposure hole  37 . More specifically, the detection window  38  is positioned diagonally below and frontward of the agitator shaft exposure hole  37 . The detection window  38  is a generally circular shaped in a side view. The detection window  38  is penetrated through a thickness of the left side wall  33 L. The detection window  38  is closed by a transparent resin plate. 
         [0056]    The agitator shaft  16  has a right end portion which is rotatably supported to the right side wall  33 R. Further, the right side wall  33 R is formed with a detection window (not shown) similar to the detection window  38  formed in the left side wall  33 L. The detection window of the right side wall  33 R is superposed with the detection window  38  of the left side wall  33 L when projected in the lateral direction. 
         [0057]    The front wall  34  extends in the lateral direction and is spanned between front end portions of the side walls  33 . The lower wall  35  extends in the lateral direction and is spanned between lower end portions of the side walls  33  such that the lower wall  35  is connected to a lower end portion of the front wall  34 . The upper wall  36  extends in the lateral direction and is spanned between upper end portions of the side walls  33  such that the upper wall  36  is connected to an upper end portion of the front wall  34 . 
         [0058]    (2) Drive Unit 
         [0059]    As shown in  FIGS. 3 and 5 , the drive unit  32  includes a gear train  41  and a gear cover  42  for covering the gear train  41 . 
         [0060]    (2-1) Gear Train 
         [0061]    The gear train  41  includes a developing gear  43 , a supply gear  44 , a developing coupling  45 , an idle gear  46 , and an agitator gear  47 . The gear train  41  is adapted to transmit a driving force from the main casing  2  to the agitator  15 . 
         [0062]    The developing gear  43  is assembled to a left side of the left side wall  33 L of the cartridge frame  31 . The developing gear  43  is fixedly coupled to a left end portion of the rotation shaft of the developing roller  11  protruding leftward from the left side wall  33 L such that relative rotation therebetween is prevented. 
         [0063]    The supply gear  44  is assembled to the left side of the left side wall  33 L of the cartridge frame  31 . The supply gear  44  is fixedly coupled to a left end portion of the rotation shaft of the supply roller  12  protruding leftward from the left side wall  33 L such that relative rotation therebetween is prevented. The supply gear  44  is positioned below and spaced apart from the developing gear  43 . 
         [0064]    The developing coupling  45  is rotatably supported to the left side wall  33 L of the cartridge frame  31  and positioned frontward of the developing gear  43 . The developing coupling  45  is generally cylindrical shaped extending in the lateral direction. The developing coupling  45  integrally includes a large-diameter gear portion  48 , a small-diameter gear portion  49 , and a coupling portion  50 . 
         [0065]    The large-diameter gear portion  48  is provided at a right end portion of the developing coupling  45 . Gear teeth are provided along the entire circumferential surface of the large-diameter gear portion  48 . The large-diameter gear portion  48  is meshingly engaged with the developing gear  43  from a front side thereof. 
         [0066]    The small-diameter gear portion  49  is generally cylindrical shaped extending leftward continuously from a left end portion of the large-diameter gear portion  48  and coaxial with the large-diameter gear portion  48 . The small-diameter gear portion  49  has an outer diameter smaller than that of the large-diameter gear portion  48 . Gear teeth are provided along the entire circumferential surface of the small-diameter gear portion  49 . The small-diameter gear portion  49  is meshingly engaged with the supply gear  44  from an upper-front side thereof. 
         [0067]    The coupling portion  50  is generally cylindrical shaped extending leftward continuously from a left end portion of the small-diameter gear portion  49  and coaxial with the large-diameter gear portion  48 . The coupling portion  50  has an outer diameter smaller than that of the small-diameter gear portion  49 . The coupling portion  50  has a left side surface provided with a fitting portion  51 . In a state where the developing cartridge  7  is assembled to the main casing  2 , a leading end portion of a main coupling (not shown) provided to the main casing  2  is fixedly coupled to the fitting portion  51  such that relative rotation therebetween is prevented. A driving force from the main casing  2  is transmitted to the fitting portion  51  through the main coupling (not shown). 
         [0068]    The idle gear  46  is rotatably supported to the left side wall  33 L of the cartridge frame  31  at a front side of the developing coupling  45 . The idle gear  46  is generally disk shaped having a thickness in the lateral direction. The idle gear  46  integrally includes a large-diameter portion  52  and a small-diameter portion  53 . 
         [0069]    The large-diameter portion  52  constitutes a left half portion of the idle gear  46 . The large-diameter portion  52  is generally disk shaped having gear teeth formed along the entire circumference thereof. The large-diameter portion  52  is meshingly engaged with the small-diameter gear portion  49  of the developing coupling  45  from a lower-front side thereof. 
         [0070]    The small-diameter portion  53  constitutes a right half portion of the idle gear  46  and is coaxial with the large-diameter portion  52 . The small-diameter portion  53  is generally disk shaped having gear teeth formed along the entire circumference thereof. The small-diameter portion  53  is disposed diagonally below and frontward of the large-diameter gear portion  48  of the developing coupling  45  and spaced apart therefrom. 
         [0071]    The agitator gear  47  is fixedly coupled to a left end portion of the agitator shaft  16  protruding leftward from the left side wall  33 L such that relative rotation therebetween is prevented. The agitator gear  47  is rotatably supported to the left side wall  33 L of the cartridge frame  31  through the agitator shaft  16 . The agitator gear  47  is meshingly engaged with the small-diameter portion  53  of the idle gear  46  from an upper front side thereof. 
         [0072]    More specifically, as illustrated in  FIG. 6 , the agitator gear  47  is formed with a fitting hole  54  in which the agitator shaft  16  is fitted and a detected opening  55 . 
         [0073]    The fitting hole  54  is positioned at a radially substantially center portion of the agitator gear  47 . The fitting hole  54  is generally D-shaped in a side view and penetrated through a thickness of the agitator gear  47  in the lateral direction. The left end portion of the agitator shaft  16  is generally D-shaped in correspondence with the shape of the fitting hole  54 , and non-rotatably fitted into the fitting hole  54  so that relative rotation between the agitator gear  47  and the agitator shaft  16  is prevented. 
         [0074]    The detected opening  55  is positioned between the gear teeth of the agitator gear  47  and the fitting hole  54 . The detected opening  55  is an opening penetrating a thickness of the agitator gear  47  in the lateral direction. The detected opening  55  has a generally arcuate shape extending in a circumferential direction of the agitator gear  47 . The detected opening  55  is defined by an upstream surface  56  and a downstream surface  57 . The upstream surface  56  is positioned upstream of the downstream surface  57  in a clockwise direction in a left side view. The upstream surface  56  is inclined diagonally rightward in a direction from an upstream end to a downstream end of the upstream surface  56  in the clockwise direction in a left side view. The downstream surface  57  is inclined diagonally leftward from an upstream end to a downstream end of the downstream surface  57  in the clockwise direction in a left side view. 
         [0075]    (2-2) Gear Cover 
         [0076]    As shown in  FIG. 3 , the gear cover  42  includes a main portion  61  and a shutter  62 . 
         [0077]    As shown in  FIGS. 3 and 7 , the main portion  61  is generally hollow prismatic body shaped and extends in the lateral direction with its leftmost end being closed. The main portion  61  includes a collar portion  63 , a support portion  66 , and a regulation portion  67 . Further, the main portion  61  is formed with a detection opening  64  and an exposure opening  65 . 
         [0078]    The collar portion  63  is positioned at a rear end portion of a left wall of the main portion  61  and protrudes leftward from the left wall of the main portion  61 . The collar portion  63  is generally hollow cylindrical shaped with its right end portion being in communication with an internal space of the main portion  61 . 
         [0079]    The coupling portion  50  of the developing coupling  45  extends through the collar portion  63  and is rotatable relative to the collar portion  63 . The fitting portion  51  of the coupling portion  50  is exposed to the outside through a left end portion of the collar portion  63 . 
         [0080]    The detection opening  64  is generally circular shaped in a side view. The detection opening  64  is positioned at a generally center portion of the left wall of the main portion  61  in the frontward/rearward direction such that the detection opening  64  confronts a lower front end portion of the agitator gear  47  from a left side thereof. The detection opening  64  is penetrated through a thickness of the left wall of the main portion  61 . 
         [0081]    The exposure opening  65  is generally square shaped in a front view. The exposure opening  65  is positioned at a lower end portion of a front wall of the main portion  61 . The exposure opening  65  is penetrated through a thickness of the front wall of the main portion  61 . 
         [0082]    The support portion  66  is generally rectangular shaped in a side view and elongated in the frontward/rearward direction. The support portion  66  is disposed at a right surface side of the left wall of the main portion  61  and at a rear side of a lower end portion of the exposure opening  65 . The support portion  66  protrudes upward from a lower wall of the main portion  61 . 
         [0083]    The regulation portion  67  is a protrusion protruding rightward from the left wall of the main portion  61  and extending in the frontward/rearward direction. The regulation portion  67  is disposed at the right surface side of the left wall of the main portion  61  and at a rear side of an upper end portion of the exposure opening  65 . 
         [0084]    As shown in  FIGS. 3 and 8 , the shutter  62  integrally includes a slider  71 , a display portion  73 , and a cover portion  72 . 
         [0085]    The slider  71  is generally flat plate shaped extending in the frontward/rearward direction. Gear teeth are provided at an upper surface of a rear end portion of the slider  71 . In the slider  71 , a portion where gear teeth are provided will be referred to as a toothed portion  74 , and a portion where gear teeth are not provided will be referred to as an untoothed portion  75 . 
         [0086]    The display portion  73  is generally rectangular flat-plate shaped in a front view extending continuously from a front end portion of the slider  71  and inclined diagonally upward toward a front side of the display portion  73 . 
         [0087]    The cover portion  72  is generally rectangular flat-plate shaped in a side view extending upward continuously from left end portions of the slider  71  and the display portion  73 . 
         [0088]    As shown in  FIG. 9 , within the main portion  61 , the shutter  62  is slidably mounted on the support portion  66  of the main portion  61  such that the cover portion  72  is positioned between the support portion  66  and regulation portion  67 . 
         [0089]    This configuration allows the shutter  62  to move to a covered position ( FIG. 10A ) and to an exposed position ( FIG. 10B ). At the covered position, the shutter  62  covers the lower front end portion of the agitator gear  47 . At the exposed position, the shutter  62  allows the lower front end portion of the agitator gear  47  to be exposed to the outside. 
         [0090]    When the shutter  62  is at the covered position ( FIG. 10A ), the cover portion  72  of the shutter  62  is interposed between the detection opening  64  and the lower front end portion of the agitator gear  47 . Further, the display portion  73  of the shutter  62  is retracted rearward from the exposure opening  65  of the main portion  61 . Further, the toothed portion  74  of the shutter  62  is meshingly engaged with a lower end portion of the agitator gear  47 . 
         [0091]    When the shutter  62  is at the exposed position ( FIG. 10B ), the cover portion  72  of the shutter  62  is advanced frontward from a position between the detection window  64  and the lower front end portion of the agitator gear  47 . At this time, the display portion  73  of the shutter  62  is exposed to the outside (a front side of the exposure opening  65 ) through the exposure opening  65  of the main portion  61 . Further, the toothed portion  74  of the shutter  62  is positioned frontward of the lower end portion of the agitator gear  47  and spaced apart therefrom. 
         [0092]    3. Main Casing 
         [0093]    As shown in  FIGS. 2 ,  11 A,  11 B,  12 A, and  12 B, a detection unit  78 , an empty sensor unit  79 , and a CPU  82  are provided within the main casing  2 . 
         [0094]    The detection unit  78  is positioned at a left side of the developing cartridge  7  within the main casing  2 . As shown in  FIGS. 11A through 12B , the detection unit  78  includes a slide member  84 , a probe  87 , an actuator  88 , and a photo-sensor  89 . 
         [0095]    The slide member  84  is a generally rectangular flat plate shaped extending in the vertical direction. The slide member  84  is slidably movable in the lateral direction by a moving mechanism (not shown). 
         [0096]    The probe  87  is generally cylindrical shaped extending in the lateral direction. The probe  87  is movably supported in the slide member  84 . The probe  87  is slidably movable in the lateral direction to an advanced position ( FIGS. 11B and 12B ) and to a retracted position ( FIGS. 11A and 12A ). At the advanced position, the probe  87  is advanced rightward, and at the retracted position, the probe  87  is retracted leftward from the advanced position. The probe  87  is connected to a compression coil spring  86 , so that the probe  87  is normally urged rightward by the compression coil spring  86  so as to be positioned at the advanced position. 
         [0097]    The actuator  88  integrally includes a pivot shaft  91 , an abutment lever  92 , and a light shielding lever  93 . The pivot shaft  91  extends in the frontward/rearward direction and is generally hollow cylindrical shaped. The abutment lever  92  extends upward from the pivot shaft  91 . The light shielding lever  93  extends downward from the pivot shaft  91 . The light shielding lever  93  has a lower end portion provided with a light shielding plate  94  extending in the lateral direction. 
         [0098]    The actuator  88  is supported to the slide member  84  and pivotally movable relative to the slide member  84  about the pivot shaft  91 . 
         [0099]    The actuator  88  is pivotally movable to a light transmitting position ( FIGS. 11B and 12B ) and to a light shielding position ( FIGS. 11A and 12A ). At the light transmitting position, the abutment lever  92  is directed diagonally upward and rightward and the light shielding lever  93  is directed diagonally downward and leftward. At the light shielding position, the abutment lever  92  and the light shielding lever  93  are directed in the vertical direction. 
         [0100]    The photo-sensor  89  includes a light emitting portion  95  and a light receiving portion  96 . The light emitting portion  95  is adapted to emit a light. The light receiving portion  96  is adapted to receive the light from the light emitting portion  95  and positioned in confrontation with and downward of the light emitting portion  95  with a gap therebetween. The photo-sensor  89  is positioned below the actuator  88  such that the light shielding plate  94  of the actuator  88  at the light shielding position is positioned between the light emitting portion  95  and the light receiving portion  96  in the vertical direction. 
         [0101]    At the light shielding position of the actuator  88 , the light shielding plate  94  of the actuator  88  is positioned between the light emitting portion  95  and the light receiving portion  96 , so that the light emitted from the light emitting portion  95  of the photo-sensor  89  is blocked by the light shielding plate  94  of the light shielding lever  93 , whereupon an ON signal is outputted from the photo-sensor  89 . 
         [0102]    On the other hand, at the light transmitting position of the actuator  88 , the light shielding plate  94  of the actuator  88  is retracted leftward from the gap between the light emitting portion  95  and the light receiving portion  96 . Thus, the light emitted from the light emitting portion  95  of the photo-sensor  89  is received by the light receiving portion  96 . At this time, an ON signal is not outputted from the photo-sensor  89 . 
         [0103]    Further, the detection unit  78  is movable within the main casing  2  to a new cartridge detection position ( FIGS. 11A and 11B ) and to a cartridge type detection position ( FIGS. 12A and 12B ). At the new cartridge detection position, the detection unit  78  detects whether the developing cartridge  7  is new or used. At the cartridge type detection position, the detection unit  78  detects types of the developing cartridge  7 . 
         [0104]    As shown in  FIG. 2 , the empty sensor unit  79  includes a light emitting element  80  and a light receiving element  81 . 
         [0105]    The light emitting element  80  is positioned within the main casing  2  and in confrontation with the detection opening  64  of the gear cover  42  from a left side thereof. The light emitting element  80  is adapted to emit a detection light to the detection opening  64 . 
         [0106]    The light receiving element  81  is positioned within the main casing  2  and in confrontation with the detection window (not shown) of the right side wall  33 R of the cartridge frame  31  from a right side thereof. The light receiving element  81  outputs an ON signal upon receipt of the detection light emitted from the light emitting element  80 . 
         [0107]    A combination of the detection unit  78  and the empty sensor unit  79  constitutes a claimed detection unit. 
         [0108]    The CPU  82  is electrically connected to the photo-sensor  89  and the light receiving element  81  so as to receive the ON signal from the photo-sensor  89  and the ON signal from the light receiving element  81 . 
         [0109]    4. Operation for Detecting New Developing Cartridge 
         [0110]    An operation for detecting a new developing cartridge  7  will be described. Note that, in the present embodiment, when the developing cartridge  7  is an unused (new) cartridge, the shutter  62  is at the covered position. That is, the covered position of the shutter  62  indicates that the developing cartridge  7  is unused (new). 
         [0111]    In order to assemble the unused developing cartridge  7  into the main casing  2 , the unused developing cartridge  7  is first attached to the drum cartridge  6 . 
         [0112]    At this time, a user looks at the gear cover  42  of the developing cartridge  7  to confirm that the display portion  73  of the shutter  62  is not exposed to the outside through the exposure opening  65 . Thus, the user can determine that the developing cartridge  7  is unused. In order to let the user know how to determine whether the developing cartridge  7  is new or used, for example, the following description is given in an instruction manual of the printer  1 : the developing cartridge  7  is unused in a case where the display portion  73  of the shutter  62  is not exposed to the outside through the exposure opening  65 , while the developing cartridge  7  is in a used state in a case where the display portion  73  of the shutter  62  is exposed to the outside through the exposure opening  65 . The user may determine a used or unused state of the developing cartridge  7  by looking at the shutter  62  as to whether the shutter  62  is visible or invisible through the detection opening  64 . 
         [0113]    Then, in order to assemble the unused developing cartridge  7  into the main casing  2 , the top cover  4  of the main casing  2  is opened to insert, from diagonally above and frontward thereof, into the main casing  2  the process cartridge  5  to which the unused developing cartridge  7  is assembled. After the process cartridge  5  is inserted into the main casing  2 , the top cover  4  is closed. In association with closing movement of the top cover  4 , the main coupling (not shown) provided in the main casing  2  is coupled to the developing coupling  45 , preventing relative rotation therebetween. 
         [0114]    As shown in  FIG. 11A , the detection unit  78  is positioned at the new cartridge detection position before the main coupling (not shown) is driven. 
         [0115]    Then, a right end portion of the probe  87  is brought into contact with the cover portion  72  of the shutter  62  from a left side thereof through the detection opening  64  of the main portion  61 . 
         [0116]    Then, the probe  87  is pressed leftward against the urging force of the compression coil spring  86  to be positioned at the retracted position. At the same time, the actuator  88  is pivotally moved in the counterclockwise direction in a front view to be positioned at the light shielding position 
         [0117]    As a result, the photo-sensor  89  outputs the ON signal to the CPU  82 . That is, the detection unit  78  detects the covered position of the shutter  62 . 
         [0118]    Then, the CPU  82  determines that the shutter  62  has been positioned at the covered position upon receipt of the ON signal from the photo-sensor  89  in a state where the detection unit  78  is at the new cartridge detection position. 
         [0119]    Then, a driving force from the main casing  2  is transmitted to the developing coupling  45  through the main coupling (not shown) for starting a warm-up operation. Then, a driving force from the developing coupling  45  is transmitted to the agitator gear  47  through the gear train  41 . As a result of rotation of the agitator gear  47  in the counterclockwise direction in a left side view, the agitator  15  is rotated in the counterclockwise direction in a left side view. 
         [0120]    At the same time, the counterclockwise rotation of the agitator gear  47  in a left side view causes the shutter  62  to move from the covered position to the exposed position. 
         [0121]    Then, as shown in  FIG. 11B , the cover portion  72  of the shutter  62  is retracted frontward from a position between the detection opening  64  and the lower front end portion of the agitator gear  47 , and the probe  87  is pressed rightward by the urging force of the compression coil spring  86  to be positioned at the advanced position. At the same time, the actuator  88  is pivotally moved in the clockwise direction in a front view from the light shielding position to the light transmitting position. 
         [0122]    As a result, output of the ON signal from the photo-sensor  89  to the CPU  82  is interrupted. That is, the detection unit  78  detects the exposed position of the shutter  62 . 
         [0123]    Then, the CPU  82  determines that the shutter  62  has been moved from the covered position to the exposed position due to interruption of the ON signal from the photo-sensor  89 . 
         [0124]    When having sequentially determined, within a predetermined period of time, that the shutter  62  is positioned at the covered position and the shutter  62  is positioned at the exposed position, the CPU  82  determines that the developing cartridge  7  is unused. 
         [0125]    That is, the CPU  82  determines that the developing cartridge  7  is an unused cartridge when the detection unit  78  detects a movement of the shutter  62  from the covered position to the exposed position within a predetermined time period. 
         [0126]    Subsequently, as shown in  FIG. 12A , the detection unit  78  is moved rightward to be positioned at the cartridge type detection position while the agitator gear  47  is rotated continuously. 
         [0127]    Then, the right end portion of the probe  87  is brought into contact with the agitator gear  47  from a left side thereof. 
         [0128]    Then, the probe  87  is pressed leftward against the urging force of the compression coil spring  86  to be positioned at the retracted position. At the same time, the actuator  88  is pivotally moved in the counterclockwise direction in a front view to be positioned at the light shielding position. 
         [0129]    As a result, the photo-sensor  89  outputs the ON signal to the CPU  82 . 
         [0130]    Then, the CPU  82  determines that the probe  87  has been moved from the advanced position to the retracted position upon receipt of the ON signal from the photo-sensor  89 . 
         [0131]    Then, as shown in  FIG. 12B , further rotation of the agitator gear  47  causes the probe  87  to face the detected opening  55  of the agitator gear  47 . 
         [0132]    As a result, the probe  87  is pressed rightward by the urging force of the compression coil spring  86  to be positioned at the advanced position. At the same time, the actuator  88  is pivotally moved in the clockwise direction in a front view from the light shielding position to be positioned at the light transmitting position. 
         [0133]    Thus, output of the ON signal from the photo-sensor  89  to the CPU  82  is interrupted. That is, the detection unit  78  detects the detected opening  55  of the agitator gear  47 . 
         [0134]    Then, the CPU  82  determines that the detected opening  55  of the agitator gear  47  has been detected due to interruption of the ON signal from the photo-sensor  89  in a state where the detection unit  78  is at the cartridge type detection position. 
         [0135]    Then, the CPU  82  determines the type of the developing cartridge  7  in accordance with the number of times of interruption of the ON signal from the photo-sensor  89  per unit time. 
         [0136]    For example, in a case where a single detected opening  55  is formed in the agitator gear  47  ( FIG. 6 ), the ON signal from the photo-sensor  89  is interrupted once during one rotation of the agitator  15 . In this case, the CPU  82  determines that a predetermined printing times is 6,000 sheets printing. 
         [0137]    In a case where two detected openings  55  are formed in the agitator gear  47  so as to be angularly spaced away from each other by 180 degrees (see  FIG. 14A ), the ON signal from the photo-sensor  89  is interrupted twice during one rotation of the agitator  15 . In this case, the CPU  82  determines that a predetermined printing times is 3,000 sheets printing. 
         [0138]    That is, the number of the detected openings  55  corresponds to information about the types of the developing cartridge  7 . More specifically, the case where the agitator gear  47  is formed with a single detected opening  55  corresponds to information (first information) about the types of the developing cartridge  7  indicating that the predetermined printing times is 6,000 sheets printing, and the case where the agitator gear  47  is formed with two detected openings  55  corresponds to information (second information) about the types of the developing cartridge  7  indicating that the predetermined printing times is 3,000 sheets printing. 
         [0139]    Thereafter, the CPU  82  counts actual printing times starting from assembly of the unused developing cartridge  7  into the main casing  2 , and notifies and displays on an operation panel (not shown) an exchanging timing of the developing cartridge  7  when the counted printing times approaches a predetermined printing times in accordance with the types of the developing cartridge  7 . 
         [0140]    Incidentally, the CPU  82  determines that the developing cartridge  7  has been detached from the main casing  2  when the type of the developing cartridge  7  has not been detected within a predetermined period of time. 
         [0141]    On the other hand, there is a case where after the unused developing cartridge  7  is assembled, the developing cartridge  7  is again assembled to the main casing  2  after the developing cartridge  7  is detached from the main casing  2 , for example, for removing a jammed sheet P. In such a case, the shutter  62  is stopped at the exposed position. 
         [0142]    At this time, the user looks at the gear cover  42  of the developing cartridge  7  to confirm that the display portion  73  of the shutter  62  is exposed to the outside through the exposure opening  65 . Thus, the user determines that the developing cartridge  7  is an old cartridge (a cartridge in use). 
         [0143]    After the used developing cartridge  7  that has once been detached is assembled once again into the main cartridge  2 , the probe  87  is not positioned at the retracted position but stays at the advanced position as shown in  FIG. 11B  when the detection unit  78  is positioned at the new cartridge detection position. Thus, the CPU  82  does not receive the ON signal from the photo-sensor  89 . 
         [0144]    Accordingly, the CPU  82  determines that the shutter  62  has stayed at the exposed position. Further, the CPU  82  determines that the re-assembled cartridge  7  is an old cartridge. 
         [0145]    Then, the CPU  82  continues comparison between the predetermined printing times and the accumulated total number of printing times from the timing at which the CPU  82  determines that the assembled developing cartridge  7  is a new cartridge. 
         [0146]    5. Operation for Detecting Remaining Amount of Toner in Developing Cartridge 
         [0147]    An operation for detecting a remaining amount of toner in the developing cartridge  7  will be described. 
         [0148]    Although not illustrated, after completion of the new cartridge detection operation and the cartridge type detection operation, the detection unit  78  is retracted from an optical path of the detection light emitted from the light emitting element  80 . 
         [0149]    Then, when the detected opening  55  and the detection window  38  are opposed to each other by rotation of the agitator gear  47  as shown in  FIG. 13A , the detection light enters the toner chamber  14  passing through the detection window  38 . That is, the detected opening  55  serves also as a light guiding portion that guides the detection light to the toner chamber  14 . 
         [0150]    When an amount of the toner in the toner chamber  14  is reduced to allow the detection light to pass through the toner chamber  14  and the detection window (not shown) of the right side wall  33 R of the cartridge frame  31 , and thus, the detection light is received by the light receiving element  81 , the light receiving element  81  outputs an ON signal to the CPU  82 . 
         [0151]    By receiving the ON signal from the light receiving element  81 , the CPU  82  determines that the amount of the toner in the toner chamber  14  is reduced. 
         [0152]    Also in this case, the CPU  82  notifies and displays on an operation panel (not shown) that an exchanging timing of the developing cartridge  7  is approaching. 
         [0153]    6. Operational Advantages 
         [0154]    (1) According to the developing cartridge  7  and the printer  1 , the shutter  62  is irreversibly movable from the covered position ( FIG. 10A ) to the exposed position ( FIG. 10B ). 
         [0155]    When the detection unit  78  detects the movement of the shutter  62  within a predetermined period of time, the CPU  82  determines that the developing cartridge  7  is unused. 
         [0156]    Thus, in a state where the developing cartridge  7  is assembled into the main casing  2 , the movement of the shutter  62  allows the detection unit  78  of the main casing  2  to detect the information as to whether the developing cartridge  7  is used or unused. 
         [0157]    Further, in a state where the developing cartridge  7  is detached from the main casing  2 , the user can easily visually confirm a position of the display portion  73  of the shutter  62 . 
         [0158]    Thus, the user can easily recognize whether the developing cartridge  7  is used or unused by confirming displacement of the display portion  73  of the shutter  62 . 
         [0159]    (2) Further, according to the developing cartridge  7  and the printer  1 , the developing cartridge  7  can be determined to be unused when the display portion  73  of the shutter  62  is positioned at the exposed position. 
         [0160]    (3) Further, according to the developing cartridge  7  and the printer  1 , the agitator gear  47  can be covered by the shutter  62  before the driving force is inputted to the gear train  41 , i.e., when the developing cartridge  7  is unused, as shown in  FIG. 10A . 
         [0161]    Thus, when the developing cartridge  7  is unused, the agitator gear  47  can be protected. 
         [0162]    (4) Further, according to the developing cartridge  7  and the printer  1 , by positioning the detection unit  78  at the cartridge type detection position after the shutter  62  has been positioned at the exposed position as shown in  FIG. 12 , the types of the developing cartridge  7  can be detected. 
         [0163]    Thus, during the use of the developing cartridge  7 , the detection unit  78  can detect the types of the developing cartridge  7  at an arbitrary timing. 
         [0164]    (5) Further, according to the developing cartridge  7  and the printer  1 , the detected opening  55  serves also as a light guiding portion for guiding the detection light emitted from the light emitting element  80  of the empty sensor unit  79  to the toner chamber  14  as shown in  FIG. 13A . 
         [0165]    Thus, the empty sensor unit  79  can detect the remaining amount of toner in the toner chamber  14 . 
         [0166]    7. Modifications 
         [0167]    (1) In the above-described embodiment, the remaining amount of toner in the toner chamber  14  is detected by means of the empty sensor unit  79 . Alternatively, however, as shown in  FIG. 13B , a position of the agitation blades  17  of the agitator  15  can be determined by means of the empty sensor unit  79 . In this case, it is assumed that a toner level is below the detection window  38  and the detection light emitted from the light emitting element  80  is always received by the light receiving element  81 . 
         [0168]    When the agitation blades  17  extending from the agitator shaft  16  confront the detection window  38  during rotation of the agitator  15 , the detection light is blocked by the agitation blades  17 . As a result, output of the ON signal from the light receiving element  81  to the CPU  82  is interrupted. 
         [0169]    Then, the CPU  82  determines that the agitation blades  17  are in confrontation with the detection window  38  due to interruption of the ON signal from the light receiving element  81 . 
         [0170]    According to the modification, the position of the agitation blades  17  of the agitator  15  can be detected by means of the empty sensor unit  79 . 
         [0171]    Thus, rotation of the agitator  15  can be controlled so as to stop the agitation blades  17  at a desired position. 
         [0172]    According to this modification, operations and effects similar to those of the above-described embodiment can also be obtained. 
         [0173]    (2) Further, in the above-described embodiment, the empty sensor unit  79  includes the light emitting element  80  and the light receiving element  81 . The light emitting element  80  is positioned at a left side of the developing cartridge  7 , and the light receiving element  81  is positioned at a right side of the developing cartridge  7 . The detection light from the light emitting element  80  is received by the light receiving element  81 . 
         [0174]    Alternatively, however, a configuration may be possible in which both the light emitting element  80  and the light receiving element  81  are positioned at a left side of the developing cartridge  7  and a reflection plate is positioned at a right side of the developing cartridge  7  to allow the detection light from the light emitting element  80  to be reflected by the reflection plate and received by the light receiving element  81 . 
         [0175]    (3) In the above-described embodiment, the shutter  62  is positioned at the covered position in a state where the developing cartridge  7  is unused, and the shutter  62  is moved from the covered position to the exposed position in the new cartridge detection operation. Alternatively, however, a configuration may be possible in which the shutter  62  is positioned at the exposed position in a state where the developing cartridge  7  is unused and the shutter  62  is moved from the exposed position to the covered position in the new cartridge detection operation. 
         [0176]    Then, after the shutter  62  is positioned at the covered position, the toothed portion  74  of the shutter  62  is moved rearward of the agitator gear  47  so as to be spaced away from the agitator gear  47 , and the untoothed portion  75  of the shutter  62  is opposed to the agitator gear  47  from below. 
         [0177]    As a result, meshing engagement between the toothed portion  74  of the shutter  62  and the agitator gear  47  is released. 
         [0178]    Note that, in this modification, the cartridge type detecting operation and the toner amount detecting operation may be performed by methods different from those described in the above embodiment and known to those skilled in the art. 
         [0179]    According to this modification, the agitator gear  47  can be covered after input of the driving force to the gear train  41 , i.e., while the developing cartridge  7  is being used. 
         [0180]    Thus, the agitator  47  can be protected while the developing cartridge  7  is being used. 
         [0181]    Further, the shutter  62  includes the toothed portion  74  to which the driving force is transmitted and the untoothed portion  75  to which the driving force is not transmitted. Accordingly, the shutter  62  can be stopped reliably after being moved with a predetermined moving amount. 
         [0182]    Thus, the shutter  62  can reliably be irreversibly moved with a simple configuration. 
         [0183]    According to this modification, operations and effects similar to those of the above-described embodiment can also be obtained. 
         [0184]    (4) Further, in the above-described embodiment, the number of the detected openings  55  formed in the agitator gear  47  corresponds to information about the type of the developing cartridge  7 . Further, the CPU  82  determines the type of the developing cartridge  7  in accordance with the number of times of interruption of the ON signal from the photo-sensor  89  per unit time. 
         [0185]    Alternatively, however, a length of the detected opening  55  in a circumferential direction of the agitator gear  47  may be made to correspond to the information about the type of the developing cartridge  7 . 
         [0186]    For example, in a case where the length of the detected opening  55  in the circumferential direction of the agitator  47  is long, this length of the detected opening  55  corresponds to the information (first information) about the type of the developing cartridge  7  indicating that a predetermined printing times is 6,000 sheets printing. Further, in a case where the length of the detected opening  55  in the circumferential direction of the agitator  47  is short, this length of the detected opening  55  corresponds to the information (second information) about the type of the developing cartridge  7  indicating that a predetermined printing times 3,000 sheets printing. 
         [0187]    Thus, the CPU  82  determines the types of the developing cartridge  7  in accordance with duration of interruption of the ON signal from the photo-sensor  89 . 
         [0188]    More specifically, in a case where the duration of interruption of the ON signal from the photo-sensor  89  is long, the CPU  82  determines that the predetermined printing times is 6,000 sheets printing. Further, in a case where the duration of interruption of the ON signal from the photo-sensor  89  is short, the CPU  82  determines that the predetermined printing times is 3,000 sheets printing. 
         [0189]    According to this modification, operations and effects similar to those of the above-described embodiment can also be obtained. 
         [0190]    (5) Further, in the above-described embodiment, the detected opening  55  is formed in the agitator gear  47 . However, a shape of the detected portion is not specifically limited. For example, as shown in  FIG. 14B , two detected projections  100  may be provided in the agitator gear  47 . 
         [0191]    Each of the detected projections  100  is formed as a projection protruding leftward from a left surface of the agitator gear  47 . The detected projection  100  is defined by a first sloped surface  98  and a second sloped surface  99 . The first sloped surface  98  is positioned downstream of the second sloped surface  99  in the clockwise direction in a left side view. The first sloped surface  98  is inclined diagonally rightward from an upstream end to a downstream end of the first sloped surface  98  in the clockwise direction in a left side view. The second sloped surface  99  is inclined diagonally leftward from an upstream end to a downstream end of the second sloped surface  99  in the clockwise direction in a left side view. 
         [0192]    Note that, in this modification, the toner amount detecting operation may be performed by a method different from that described in the above embodiment and known to those skilled in the art. 
         [0193]    According to this modification, the detection unit  78  is allowed to detect the types of the developing cartridge  7  with a simple configuration. 
         [0194]    According to this modification, operations and effects similar to those of the above-described embodiment can also be obtained. 
         [0195]    (6) Further, in the above-described embodiment, the detection unit  78  is movable to the new cartridge detection position and to the cartridge type detection position. Alternatively, however, appropriate arrangement of the slide member  84 , the probe  87 , the actuator  88 , and the photo-sensor  89  allows detection of whether the developing cartridge  7  is used or unused and detection of the type of the developing cartridge  7  without moving the detection unit  78 . 
         [0196]    While the present invention has been described in detail with reference to the embodiments thereof, it would be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the present invention.