Abstract:
A cartridge which may include a housing, a driving input member provided at the housing wherein the driving input member is configured to be rotated by an externally supplied rotation driving force, and a rotational member configured to receive the rotation driving force, which is transmitted from the driving input member, and be rotated thereby. The cartridge may also include a detection protrusion provided at a position away from a rotational center of the rotational member. The detection protrusion may include a main body protruding from the rotational member away from the housing and a pivot part configured to pivot relative to the main body. The detection protrusion may be configured to be changeable between an extended state and a collapsed state with respect to the rotational member.

Description:
TECHNICAL FIELD 
     The present disclosure relates to a cartridge used for an image forming apparatus such as a laser printer. 
     BACKGROUND 
     In an example of a laser printer, a developing cartridge is installed in a printer body. Toner is included in the developing cartridge. The toner in the developing cartridge is used to form an image on paper. When the toner in the developing cartridge is exhausted, the developing cartridge is taken out of the printer body, and a new developing cartridge is installed in the printer body. If a paper jam occurs in the printer body, the developing cartridge is taken out of the printer body; after the paper jam has been cleared, the developing cartridge may be installed again in the printer body. 
     A detecting gear is attached to a side surface of the developing cartridge so as to be rotatable about an axis line (rotational axis line) extending in a direction orthogonal to the side surface. The detecting gear has a plate-like detecting gear body and an abutting protrusion formed integrally with the detecting gear body, the abutting protrusion being disposed on an outer side of the detecting gear (on a side of the detecting gear body opposite to the side surface of the developing cartridge). Gear teeth are formed on the circumferential surface of the detecting gear except some portion of the circumferential surface. 
     With a new developing cartridge, the gear teeth of the detecting gear are engaged with the gear teeth of a transmission gear. When the developing cartridge is installed in the printer body, the driving force of a motor is supplied to the transmission gear, and the driving force is transmitted from the transmission gear to the detection gear through their gear teeth. 
     Thus, the detection gear rotates, and the abutting protrusion of the detecting gear moves in the rotational direction of the detecting gear due to the rotation of the detecting gear. When the detecting gear further rotates and a missing tooth portion of the detecting gear faces the gear teeth of the transmission gear, the engagement between the gear teeth of the transmission gear and the gear teeth of the detecting gear is released, stopping the rotation of the detecting gear. Accordingly, after the developing cartridge has been installed in the printer body even once, the engagement between the gear teeth of the transmission gear teeth of the gear teeth of the detecting gear is released and the disengaged state is kept after that. 
     In the printer body, a sensor that detects the passage of the abutting protrusion is provided, regarding the abutting protrusion as a protrusion to be detected. Whether the developing cartridge is a new one or an old one is determined depending on whether the sensor has detected the passage of the abutting protrusion. Specifically, after the developing cartridge has been installed in the printer body, if the passage of the abutting protrusion is detected by the sensor, the developing cartridge is determined to be new. However, after the developing cartridge has been installed in the printer body, if the passage of the abutting protrusion is not detected by the sensor, the developing cartridge is determined to be old. 
     If, however, an amount by which the abutting protrusion protrudes from the side surface of the developing cartridge is large, when the developing cartridge is installed in or removed from the printer body, the abutting protrusion may rub against a member in the printer body and may wear out. Further, with the large amount of protrusion of the abutting protrusion is that when the developing cartridge is installed in or removed from the printer body, the abutting protrusion may come into contact with a member in the printer body or may be caught by the member and the abutting protrusion and/or the member in the printer body may thereby be damaged. 
     SUMMARY 
     Aspects of the disclosure provide a cartridge that can reduce the wear of a protrusion to be detected. For example, in an illustrative embodiment of the disclosure, a cartridge which may include a housing, a driving input member provided at the housing wherein the driving input member is configured to be rotated by an externally supplied rotation driving force, and a rotational member configured to receive the rotation driving force, which is transmitted from the driving input member, and be rotated thereby. The cartridge may also include a detection protrusion provided at a position away from a rotational center of the rotational member. The detection protrusion may include a main body protruding from the rotational member away from the housing and a pivot part configured to pivot relative to the main body. The detection protrusion may be configured to be changeable between an extended state and a collapsed state with respect to the rotational member. 
     Accordingly, if the detection protrusion is in the collapsed state when, for example, the cartridge is installed in or removed from the main body casing, contact of the detection protrusion with other members can be reduced and the wear and damage of the detection protrusion due to the contact can be reduced. 
     Aspects of the disclosure may relate to a cartridge which may include a housing, a driving input member provided at the housing wherein the driving input member is configured to be rotated by an externally supplied rotation driving force, and a rotational member configured to receive the rotation driving force, which is transmitted from the driving input member, and be rotated thereby. The cartridge may also include a cover attached to the housing wherein the cover has an opposite part that faces the rotational member and a detection protrusion provided at a position away from a rotational center of the rotational member. The detection protrusion may include a main body which protrudes from a face of the rotational member and a pivot part configured to pivot relative to the main body. The detection protrusion may be configured to be changeable between an extended state and a collapsed state. At an initial position, which is a position before the rotational member is rotated, and at a terminal position, which is a position after the rotational member has completed rotating, the opposite part of the cover may contact the detection protrusion and configure to change the detection protrusion from the collapsed state to the extended state. At a point between the initial position and the terminal position, the detection protrusion may extend through a hole in the opposite part of the cover and assume the extended state. 
     Aspects of the disclosure may relate to cartridge which may include a housing, a driving input member provided at the housing wherein the driving input member is configured to be rotated by an externally supplied rotation driving force, and a rotational member configured to receive the rotation driving force, which is transmitted from the driving input member, and be rotated thereby. The cartridge may also include a cover attached to the housing wherein the cover has an opposite part that faces the rotational member and a detection protrusion provided at a position away from a rotational center of the rotational member. The detection protrusion may be configured to be changeable between an extended state in which the pivot part is positioned at first orientation relative to the main body, and a collapsed state in which the pivot part is positioned at second orientation relative to the main body, which is different that the first orientation. At least a portion of the detection protrusion may be configured to pivot about a pivotal axis that is substantially parallel to a face of the rotational member that faces the cover in order to assume each of the extended state and the collapsed state. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a cross-sectional view of a laser printer in which a developing cartridge according to an embodiment of the present disclosure is installed. 
         FIG. 2  is a left side view of the developing cartridge, indicating a state in which a detection protrusion is positioned at an initial position. 
         FIG. 3  is a perspective view at the left end of the developing cartridge illustrated in  FIG. 2 , as viewed from above at the back on the left side. 
         FIG. 4  is a perspective view at the left end of the developing cartridge illustrated in  FIG. 2 , as viewed from above at the back on the left side, indicating a state in which a gear cover is removed. 
         FIG. 5  is a cross sectional view taken along cutting-plane line A-A indicated in  FIG. 2 . 
         FIG. 6  is a left side view of the developing cartridge, indicating a state in which the detection protrusion is positioned at an intermediate position between the initial position and a terminal position. 
         FIG. 7  is a perspective view at the left end of the developing cartridge illustrated in  FIG. 6 , as viewed from above at the back on the left side. 
         FIG. 8  is a perspective view at the left end of the developing cartridge illustrated in  FIG. 6 , as viewed from the bottom at the back on the left side. 
         FIG. 9  is a cross sectional view taken along cutting-plane line B-B indicated in  FIG. 6 . 
         FIG. 10  is a left side view of the developing cartridge, indicating a state in which the detection protrusion is placed in a extended state. 
         FIG. 11  is a perspective view at the left end of the developing cartridge illustrated in  FIG. 10 , as viewed from the bottom at the front on the left side. 
         FIG. 12  is a perspective view at the left end of the developing cartridge illustrated in  FIG. 10 , as viewed from the bottom at the front on the left side, indicating a state in which the gear cover is removed. 
         FIG. 13  is a left side view of the developing cartridge, indicating a state in which an actuator is placed in a detecting state. 
         FIG. 14  is a left side view of the developing cartridge, indicating a state in which the detection protrusion is in contact with a linear portion. 
         FIG. 15  is a left side view of the developing cartridge, indicating a state in which the detection protrusion is positioned at the terminal position. 
         FIG. 16  is a left side view of the developing cartridge illustrated in  FIG. 15 , indicating a state in which the gear cover is removed. 
         FIG. 17  is a left side view of a developing cartridge in a variation. 
         FIG. 18  is a schematic side view illustrating a structure (structure used instead of a missing tooth gear part of a reset gear) according to the variation. 
     
    
    
     DETAILED DESCRIPTION 
     An embodiment of the present disclosure will be described below in detail with reference to the attached drawings. 
     1. Entire Structure of a Laser Printer 
     As illustrated in  FIG. 1 , a laser printer  1  has a main body casing (printer body)  2 . A side wall at the front of the main body casing  2  has a cartridge installing/removing port  3  and a front cover  4  that opens and closes the installing/removing port  3 . 
     The front of the laser printer  1  is on the forward side in the fore-aft direction. The upper sides, lower sides, right sides, and left sides of the laser printer  1  placed on a flat surface and a developing cartridge  7  (described later) installed in the main body casing  2  of the laser printer  1  are defined as viewed from the front. 
     A process cartridge  5  is installed at a position a little apart from the center in the main body casing  2  toward the front. The process cartridge  5  is inserted into the main body casing  2  through the installing/removing port  3  with the front cover  4  open, and is removed from the main body casing  2 . 
     The process cartridge  5  has a drum cartridge  6  and the developing cartridge  7 , which is an example of a cartridge that is removably installed in the drum cartridge  6 . 
     The drum cartridge  6  has a drum frame  8 . A photosensitive drum  9  is rotatably held at the rear end of the drum frame  8 . A charger  10  and a transfer roller  11  are held in the drum frame  8 . The charger  10  is disposed above the photosensitive drum  9  and the transfer roller  11  is disposed below the photosensitive drum  9 . 
     In the drum frame  8 , a portion in front of the photosensitive drum  9  is a cartridge installation part  12 . The developing cartridge  7  is installed in the cartridge installation part  12 . 
     The developing cartridge  7  has a housing  13  in which toner is included. A toner room  14  and a developing room  15 , which mutually communicate, are adjacently formed fore and aft in the housing  13 . 
     An agitator  16  is provided in the toner room  14  so as to be rotatable about an agitator rotational axis line  17  extending in the right and left direction. The toner in the toner room  14  is stirred by the rotation of the agitator  16  and is fed from the toner room  14  to the developing room  15 . 
     In the developing room  15 , a developing roller  18  is provided so as to be rotatable about a developing rotational axis line  20  extending in the right and left direction and a supply roller  19  is also provided so as to be rotatable about a supply rotational axis line  21  extending in the right and left direction. 
     The developing roller  18  is disposed so that part of its circumferential surface is exposed from the rear end of the housing  13 . The developing cartridge  7  is installed in the drum cartridge  6  so that the circumferential surface of the developing roller  18  comes into contact with the circumferential surface of the photosensitive drum  9 . 
     The supply roller  19  is disposed so that its circumferential surface comes into contact with the circumferential surface of the developing roller  18  from its lower side on the front side. The toner in the developing room  15  is supplied by the supply roller  19  to the circumferential surface of the developing roller  18  and is supported on the circumferential surface of the developing roller  18  as a thin layer. 
     In the main body casing  2 , an exposure unit  22  including a laser and the like is disposed above the process cartridge  5 . 
     During the formation of an image, the photosensitive drum  9  is rotated at a fixed speed clockwise as viewed from the left side. The circumferential surface (front surface) of the photosensitive drum  9  is uniformly charged due to the discharging of the charger  10  when the photosensitive drum  9  rotates. The exposure unit  22  is controlled according to image data, and a laser beam is emitted from the exposure unit  22 . For example, the laser printer  1  is connected to a personal computer (not shown), and the image data is sent from the personal computer to the laser printer  1 . The laser beam passes between the charger  10  and the developing cartridge  7  and is incident on the uniformly charged circumferential surface of the photosensitive drum  9 , selectively exposing the circumferential surface of the photosensitive drum  9 . This exposure selectively removes charges from exposed parts of the photosensitive drum  9 , forming an electrostatic latent image on the circumferential surface of the photosensitive drum  9 . When the photosensitive drum  9  rotates and the electrostatic latent image faces the developing roller  18 , toner is supplied from the developing roller  18  to the electrostatic latent image and the electrostatic latent image is developed as a toner image. 
     A paper supply cassette  23  that stores paper P is provided at the bottom of the main body casing  2 . A pickup roller  24  used to feed out paper from the paper supply cassette  23  is provided above the paper supply cassette  23 . 
     A transport path  25 , which is S-shaped as viewed from a side, is formed in the main body casing  2 . The transport path  25  extends from the paper supply cassette  23  through the photosensitive drum  9  and transfer roller  11  to a paper ejection tray  26  formed on the upper surface of the main body casing  2 . 
     The toner image on the circumferential surface of the photosensitive drum  9  is transferred to the paper P that passes between the photosensitive drum  9  and the transfer roller  11  by the effect of a bias applied to the transfer roller  11 . 
     On the transport path  25 , a fixing unit  27  is provided downstream of the transfer roller  11  in the direction in which the paper P is transported. The paper P on which the toner image has been transferred is transported along the transport path  25  and passes through the fixing unit  27 . In the fixing unit  27 , the toner image is heated and pressurized to fix it to the paper P as an image. The paper P, on which the image has been formed in this way, is further transported along the transport path  25  and is ejected onto the paper ejection tray  26 . 
     2. Developing Cartridge 
     2-1. Housing 
     The housing  13  of the developing cartridge  7  has a first side wall  41  (see  FIG. 2 ) and a second side wall  42  (see  FIG. 1 ) that face each other with a spacing therebetween in the right and left direction, as shown in  FIGS. 1 and 2 . 
     2-2. Gear Train 
     A gear cover  43  is attached to the external side surface (left surface) of the first side wall  41  used as an example of a cover, as shown in  FIGS. 2 and 3 . A gear train  44  is provided inside the gear cover  43 , as shown in  FIG. 4 . The gear train  44  includes an input gear  45  used as an example of a driving input member, a developing gear  46 , a supply gear  47 , an intermediate gear  48 , an agitator gear  49  used as an example of a transmitting member, and a reset gear  50  used as an example of a rotating member. 
     2-2-1. Input Gear 
     The input gear  45  is positioned at an upper portion at the rear end of the first side wall  41 . The input gear  45  is disposed so as to be rotatable about an input gear rotational axis  51  (see  FIG. 2 ) that extends in the right and left direction. The input gear rotational axis  51  is held to the first side wall  41  so as not to be rotatable. 
     The input gear  45  integrally has a large-diameter gear part  52 , a small-diameter gear part  53 , and a coupling part  54  as shown in  FIG. 4 . The large-diameter gear part  52 , small-diameter gear part  53 , and coupling part  54  are placed in that order from the same side as the first side wall  41 . 
     The large-diameter gear part  52  is formed in a discoid shape, which has a central axis line that matches the central axis line of the input gear rotational axis  51 . Many gear teeth are formed over the entire circumferential surface of the large-diameter gear part  52 . 
     The small-diameter gear part  53  is formed in a discoid shape, which has a central axis line that matches the central axis line of the input gear rotational axis  51 , the small-diameter gear part  53  having a smaller diameter than the large-diameter gear part  52 . Many gear teeth are formed over the entire circumferential surface of the small-diameter gear part  53 . 
     The coupling part  54  is formed in a columnar shape, which has a central axis line that matches the central axis line of the input gear rotational axis  51 , the circumferential surface of the coupling part  54  having a smaller diameter than the circumferential surface of the small-diameter gear part  53 . A linkage recess  55  is formed in the left side surface of the coupling part  54 . With the developing cartridge  7  installed in the main body casing  2 , the distal end of a driving output member  56  (see  FIG. 3 ) provided in the main body casing  2  is inserted into the linkage recess  55 . 
     The driving output member  56  is provided so as to be advanceable and retractable in the right and left direction. With the developing cartridge  7  installed in the main body casing  2 , the driving output member  56  advances to the right and its distal end is inserted into the linkage recess  55 . Thus, the driving output member  56  and linkage recess  55  are mutually joined so as not to be relatively rotatable. When the driving output member  56  is rotated, therefore, the rotational force of the driving output member  56  is received by the input gear  45  as a driving force and the input gear  45  is thereby rotated together with the driving output member  56 . 
     2-2-2. Developing Gear 
     The developing gear  46  may be placed below and behind the input gear  45  as shown in  FIG. 4 . The developing gear  46  is attached to a developing roller axis  57  of the developing roller  18  so as not to be relatively rotatable. The developing roller axis  57  is rotatably attached to the first side wall  41 ; the central axis line of the developing roller axis  57  is the developing rotational axis line  20  (see  FIG. 1 ), which is the rotational axis line of the developing roller  18 . Gear teeth are formed over the entire circumferential surface of the developing gear  46 ; the gear teeth have been engaged with the gear teeth of the large-diameter gear part  52  of the input gear  45 . 
     2-2-3. Supply Gear 
     The supply gear  47  may be placed below the input gear  45  as shown in  FIG. 4 . The supply gear  47  is attached to a supply roller axis  58  of the supply roller  19  (see  FIG. 1 ) so as not to be relatively rotatable. The supply roller axis  58  is rotatably attached to the first side wall  41 ; the central axis line of the supply roller axis  58  is the supply rotational axis line  21  (see  FIG. 1 ), which is the rotational axis line of the supply roller  19 . Gear teeth are formed over the entire circumferential surface of the supply gear  47 ; the gear teeth of the supply gear  47  be engaged with the gear teeth of the large-diameter gear part  52  of the input gear  45 . 
     2-2-4. Intermediate Gear 
     The intermediate gear  48  may be placed above and in front of the input gear  45  as shown in  FIG. 4 . The intermediate gear  48  is disposed so as to be rotatable about the central axis line of an intermediate gear rotational axis  59  extending in the right and left direction. The intermediate gear rotational axis  59  is held to the first side wall  41  so as not to be rotatable. 
     The intermediate gear  48  integrally has a small-diameter part  60 , which is formed in a discoid shape with a relatively small outer diameter, and a large-diameter part  61 , which is formed in a columnar shape with a relatively large outer diameter, as shown in  FIG. 3 . The small-diameter part  60  and large-diameter part  61  are placed in that order from the same side as the first side wall  41 . The central axis lines of the small-diameter part  60  and large-diameter part  61  match the central axis line of the intermediate gear rotational axis  59 . 
     Gear teeth are formed over the entire circumferential surface of the small-diameter part  60 . 
     Gear teeth are formed over the entire circumferential surface of the large-diameter part  61 ; the gear teeth of the large-diameter part  61  have been engaged with the gear teeth of the small-diameter gear part  53  of the input gear  45 . 
     2-2-5. Agitator Gear 
     The agitator gear  49  may be placed below and in front of the intermediate gear  48  as shown in  FIG. 4 . The agitator gear  49  is attached to an agitator rotational axis  62  so as not to be relatively rotatable. The agitator rotational axis  62  passes through the first side wall  41  and second side wall  42  (see  FIG. 1 ) in the right and left direction and is rotatably held to the first side wall  41  and second side wall  42 . In the housing  13 , the agitator  16  is attached to the agitator rotational axis  62 . Accordingly, the agitator  16  and agitator gear  49  use the central axis line of the agitator rotational axis  62  as the agitator rotational axis line  17  (see  FIG. 1 ), so they are rotatable together with the agitator rotational axis  62 . 
     The agitator gear  49  integrally has a large-diameter gear part  64  and a small-diameter gear part  65 . 
     The large-diameter gear part  64  is formed in a discoid shape, which has a central axis line that matches the central axis line of the agitator rotational axis  62 . Gear teeth are formed over the entire circumferential surface of the large-diameter gear part  64 . The gear teeth of the large-diameter gear part  64  have been engaged with the gear teeth of the small-diameter part  60  of the intermediate gear  48 . 
     The small-diameter gear part  65  is formed on a side opposite to the first side wall  41  with respect to the large-diameter gear part  64 , has a discoid shape, which has a central axis line that matches the central axis line of the agitator rotational axis  62 , and has a smaller diameter than the large-diameter gear part  64 . Gear teeth  66  are formed over the entire circumferential surface of the small-diameter gear part  65 . 
     2-2-6. Reset Gear 
     The reset gear  50  may be placed above and in front of the agitator gear  49  as shown in  FIG. 4 . The reset gear  50  is disposed so as to be rotatable about a rotational axis  67  extending in the right and left direction, as shown in  FIG. 5 . The rotational axis  67  is held to the first side wall  41  so as not to be rotatable. 
     The reset gear  50  integrally has a missing tooth gear part  68  used as an example of a passive part and a cylindrical boss  69 , which is cylindrical. 
     The missing tooth gear part  68  is formed in a discoid shape, which has a central axis line that matches the central axis line of the rotational axis  67 . Gear teeth  70  are formed on part of the circumferential surface of the missing tooth gear part  68 . Specifically, a portion having a central angle of about 185 degrees is formed on the circumferential surface of the missing tooth gear part  68  as a missing tooth part  71 , and gear teeth  70  are formed on a portion having a central angle of about 175 degrees outside the missing tooth part  71 . The gear teeth  70  are engaged with the gear teeth  66  of the small-diameter gear part  65  of the agitator gear  49  at some rotational position of the reset gear  50 . 
     The cylindrical boss  69 , which protrudes from the left end surface of the missing tooth gear part  68  to the left, is formed in a cylindrical shape, which has a central axis line that matches the central axis line of the missing tooth gear part  68 . The rotational axis  67  is inserted into the cylindrical boss  69  so as to be relatively rotatable. Accordingly, the reset gear  50  is rotatably supported with the rotational axis  67  acting as a fulcrum. 
     2-3. Detection Protrusion 
     On the left end surface of the missing tooth gear part  68  of the reset gear  50 , a detection protrusion  81  is provided on a portion where the missing tooth gear part  68  has the missing tooth part  71  as the circumferential surface. 
     The detection protrusion  81  has a main body  811  and a swinging or pivot part  812 . The main body  811 , which is formed in a rectangular plate shape, protrudes from the missing tooth gear part  68  to the left in the tangential direction of a circular track drawn by the detection protrusion  81  when the reset gear  50  rotates (simply referred to below as the tangential direction). A columnar swinging axis part  813  is integrally formed at the proximal end of the swinging part  812 , the central axis line of the swinging part  812  extending in the tangential direction. The swinging axis part  813 , used as an example of a rotational axis, of the swinging part  812  is held to the distal end of the main body  811  so as to be rotatable about the central axis line of the main body  811 . Accordingly, the detection protrusion  81  is attached so as to be changeable between a extended state (shown in  FIG. 11 ) in which the swinging part  812  extends from the distal end of the main body  811  to the left and a collapsed state (shown in  FIG. 4 ) in which the swinging part  812  is bent with respect to the main body  811  through 90 degrees toward the outside of the rotational radial direction of the reset gear  50 . 
     2-4. Gear Cover 
     A gear cover  43  integrally has an opposite wall  82 , which faces the first side wall  41  from the left side, and a circumferential wall  83 , which extends toward the first side wall  41  from the circumferential edge of the opposite wall  82 , as shown in  FIG. 3 . The gear cover  43  is made of, for example, a resin. 
     The opposite wall  82  has an opposite part  84 , which faces the reset gear  50  from the left side as shown in  FIGS. 3 and 5 . The opposite part  84  has a circular shape as viewed from a side. 
     A round hole  85 , which is a through-hole, is formed at the center of the opposite part  84 . A substantially cylindrical boss part  86  is formed, which protrudes from the circumferential edge of the round hole  85  toward the inside of the gear cover  43  (to the right), as shown in  FIG. 5 . The part  86  is inserted into the cylindrical boss  69  of the reset gear  50  and the distal end (right end) of the part  86  is inserted into the distal end of the rotational axis  67 . 
     On the inner surface of the opposite part  84 , a recess  87 , which has a circular shape concentric with the round hole  85  and is one step deeper, is formed on a side opposite to the first side wall  41  (on the left side), as shown in  FIG. 5 . Accordingly, a cylindrical side wall  88 , which is linked to the inside and outside of the recess  86 , is formed on the inner surface of the opposite part  84 . 
     On the side wall  88 , a protrusion extending cam  89  used as an example of a protrusion extending cam member is formed so as to protrude toward the inside as shown in  FIGS. 2 and 5 . The protrusion extending cam  89 , disposed between a position in front of the round hole  85  and a position above the round hole  85 , has an arc shape having a central angle of about 90 degrees as viewed from a side, as shown in  FIG. 2 . The protrusion extending cam  89  is also sloped so as to separate from the first side wall  41  as the protrusion extending cam  89  approaches from the position in front of the round hole  85  to the position above the round hole  85 . 
     The opposite part  84  used as an example of a protrusion falling cam member has a substantially arc-shaped opening  90 , which extends along the side wall  88 , inside the side wall  88 . A spacing is provided between the round hole  85  and the inner end edge of the opening  90  in a radial direction of the opposite part  84 . The inner end edge of the spacing has a semicircular part  901  in a semicircular shape and a linear part  902 , used as an example of an edge, that linearly extends and is linked to the downstream of the semicircular part  901  in its rotational direction R (described later) and intersects the circular track drawn by the detection protrusion  81  when the reset gear  50  rotates. 
     The opposite wall  82  has an opening  91  through which the coupling part  54  of the input gear  45  is exposed. 
     3. Detection Mechanism 
     A detection mechanism  101  that detects the detection protrusion  81  is provided in the main body casing  2  as shown in  FIG. 2 . The detection mechanism  101  includes an actuator  102  and an optical sensor  103  that has a light emitting element and a photosensitive element. 
     The actuator  102  integrally has a swinging axis  104  extending in the right and left direction, an abutting lever  105  extending downward from the swinging axis  104 , and a light shielding lever  106  extending backward from the swinging axis  104 . The swinging axis  104  is rotatably held to, for example, the inner wall (not shown) of the main body casing  2 . The abutting lever  105  and light shielding lever  106  intersect at an angle of about 80 degrees, centered around the swinging axis  104 . 
     The actuator  102  is swingably attached so as to be changeable between a non-detecting state (state shown in  FIG. 2 ), in which the abutting lever  105  extends forward and downward from the swinging axis  104  and the light shielding lever  106  extends backward and downward, and a detecting state (state shown in  FIG. 13 ), in which the abutting lever  105  extends backward and the light shielding lever  106  extends backward. The actuator  102  is biased by a spring force of a spring (not shown) so that the actuator  102  is placed in the non-detecting state when external forces other than the spring force are not applied. 
     The optical sensor  103  has the light emitting element and photosensitive element that are placed opposite to each other in the right and left direction. An optical path of the optical sensor  103 , which extends from the light emitting element to the photosensitive element, is blocked by the light shielding lever  106  of the actuator  102 , and the actuator  102  placed in the detecting state is positioned at a position to which the light shielding lever  106  is retracted from the optical path. When the light shielding lever  106  is retracted (shifted) from the optical path extending from the light emitting element to the photosensitive element, an ON signal is output from the optical sensor  103 . 
     A microcomputer (not shown) is electrically connected to the optical sensor  103 . 
     4. Detection of a New Developing Cartridge 
     As shown in  FIGS. 3 and 4 , when the developing cartridge  7  is a new one, the detection protrusion  81  is positioned at an initial position below and in front of the cylindrical boss  69  (rotational axis  67 ) of the reset gear  50 . In this initial state, about half of the detection protrusion  81  is placed inside the gear cover  43 , and the detection protrusion  81  is placed in the collapsed state. The most downstream gear tooth  70  of the row of the gear teeth  70  of the reset gear  50  in the rotational direction R has been engaged with the gear teeth  66  of the agitator gear  49 . 
     When the developing cartridge  7  is installed in the main body casing  2 , a warm-up operation starts for the laser printer  1 . In the warm-up operation, the driving output member  56  (see  FIG. 2 ) is inserted into the coupling part  54  (linkage recess  55 ) of the input gear  45 , and the driving force is supplied from the driving output member  56  to the input gear  45 , rotating the input gear  45 . Due to the rotation of the input gear  45 , the developing gear  46 , supply gear  47 , and intermediate gear  48  are rotated and the developing roller  18  and supply roller  19  are rotated. Due to the rotation of the intermediate gear  48 , the agitator gear  49  is rotated and the agitator  16  (see  FIG. 1 ) is rotated. Due to the rotation of the agitator  16 , the toner in the developing cartridge  7  is stirred. 
     When the new developing cartridge  7  is a new one, the gear teeth  66  of the agitator gear  49  and the gear teeth  70  of the reset gear  50  have been mutually engaged; when the agitator gear  49  is rotated, therefore, the reset gear  50  follows the rotation and is rotated in the rotational direction R, which is counterclockwise as viewed from the left side. 
     Before and immediately after the new developing cartridge  7  is installed in the main body casing  2 , the actuator  102  is placed in a to-be-detected state as shown in  FIG. 2 , the abutting lever  105  faces the opening  90  of the gear cover  43  in the right and left direction, and the optical path of the optical sensor  103  is blocked by the light shielding lever  106 . Thus, an OFF signal is output from the optical sensor  103 . 
     When the reset gear  50  rotates, the detection protrusion  81  moves in the rotational direction R. The swinging part  812  of the detection protrusion  81  abuts the protrusion extending cam  89  during the movement as shown in  FIGS. 6 ,  7 ,  8 , and  9 . The swinging part  812  then receives a force from the protrusion extending cam  89  during the subsequent rotation of the reset gear  50 ; the force causes the swinging part  812  to change from a state in which the swinging part  812  is bent with respect to the main body  811  to a state in which the swinging part  812  extends to the left. As a result, the detection protrusion  81  changes from the collapsed state to the extended state as shown in  FIGS. 10 ,  11 , and  12 . 
     When the rotation of the reset gear  50  proceeds, the detection protrusion  81  abuts the abutting lever  105 . When the rotation of the reset gear  50  further proceeds, the detection protrusion  81  pushes the abutting lever  105  backward, shifting the actuator  102  from the to-be-detected state to the detecting state as shown in  FIG. 13 . As a result, the light shielding lever  106  is removed from the optical path of the optical sensor  103 , which extends from the light emitting element to the photosensitive element, and an ON signal is output from the optical sensor  103 . Accordingly, detection of the detection protrusion  81  by the optical sensor  103  is achieved. 
     When the reset gear  50  further rotates and the detection protrusion  81  is released from the abutting lever  105 , the actuator  102  returns from the detecting state to the to-be-detected state. As a result, the optical path of the optical sensor  103 , which extends from the light emitting element to the photosensitive element, is blocked by the light shielding lever  106  and the output signal from the optical sensor  103  is switched from the ON signal to an OFF signal. 
     When the reset gear  50  further rotates, the detection protrusion  81  abuts the downstream end edge of the opening  90  of the gear cover  43  in the rotational direction R as shown in  FIG. 14 , that is, the linear part  902 . Due to the subsequent rotation of the reset gear  50 , the detection protrusion  81  receives a force from the linear part  902 . This force bends the swinging part  812  of the detection protrusion  81  toward the outside of the rotational radial direction of the reset gear  50  and protrudes into the inside of the gear cover  43 . As a result, the detection protrusion  81  changes from the extended state to the collapsed state as shown in  FIG. 15 . 
     Then, when the rotation of the reset gear  50  further proceeds, the gear teeth  70  of the reset gear  50  are disengaged from the gear teeth  66  of the agitator gear  49  and the missing tooth part  71  of the reset gear  50  faces the gear teeth  66 , as shown in  FIG. 16 . Accordingly, the rotation of the reset gear  50  stops and the detection protrusion  81  is positioned at a terminal position. 
     As described above, when the new developing cartridge  7  is installed in the main body casing  2  for the first time, an ON signal is output from the optical sensor  103 . Therefore, if an ON signal is output from the optical sensor  103  after the developing cartridge  7  has been installed in the main body casing  2 , it can be determined that the developing cartridge  7  is a new one. 
     When an old developing cartridge  7  (a developing cartridge  7  that has been installed in the main body casing  2  at least once) is installed in the main body casing  2 , the rotational position of the reset gear  50  is a position at which the gear teeth  70  have already been disengaged from the gear teeth  66 , so even if the warm-up operation of the laser printer  1  is started, the reset gear  50  does not rotate. Therefore, if an ON signal is not output from the optical sensor  103  within a prescribed time after the developing cartridge  7  has been installed in the main body casing  2 , it can be determined that the developing cartridge  7  is an old one. 
     As described above, the input gear  45  is provided in the casing of the developing cartridge  7 . The input gear  45  is rotated by a rotation driving force supplied from the outside. When the input gear  45  rotates, the rotation driving force is output from the input gear  45 . The developing cartridge  7  has the reset gear  50  that receives the rotation driving force output from the input gear  45  and rotates. 
     The detection protrusion  81  is provided at a position apart from the rotational center of the reset gear  50 . The detection protrusion  81  is changeable between the extended state and the collapsed state with respect to the reset gear  50 . 
     If the detection protrusion  81  is placed in the collapsed state when, for example, the developing cartridge  7  is installed in or removed from the main body casing, the detection protrusion  81  can be made less likely to come into contact with other members and the wear and damage of the detection protrusion  81 , which is caused by the contact, can thereby be reduced. 
     Even if the detection protrusion  81  is placed in the extended state, when the detection protrusion  81  abuts another member and a force is applied to the detection protrusion  81 , the detection protrusion  81  changes from the extended state to the collapsed state. Accordingly, it can be reduced that the detection protrusion  81  is strongly rubbed and the wear of the detection protrusion  81  can thereby be reduced. Since the force applied to the detection protrusion  81  can be released, the damage to the detection protrusion  81  can also be reduced. 
     The detection protrusion  81  is placed in the collapsed state at the initial position, which is a position before the reset gear  50  rotates, that is, in a state in which the detection protrusion  81  is positioned at the initial position before the reset gear  50  receives the rotation driving force from the input gear  45 . 
     Accordingly, the detection protrusion  81  can be made less likely to come into contact with other members when, for example, the developing cartridge  7  is carried or the developing cartridge  7  is installed in the main body casing  2 , and the wear and damage of the detection protrusion  81 , which is caused by the contact, can thereby be reduced. 
     The detection protrusion  81  is provided so as to be rotatable about the swinging axis part  813 . The swinging axis part  813  extends in the tangential direction of the circular track drawn by the detection protrusion  81  when the reset gear  50  rotates. 
     Accordingly, the detection protrusion  81  can be made changeable between the state in which the detection protrusion  81  stands on the circular track and the state in which the detection protrusion  81  falls down in a radial direction of the circular track. 
     The developing cartridge  7  has the protrusion extending cam  89 , which is used to change the detection protrusion  81  from the collapsed state to the extended state. 
     Accordingly, when the reset gear  50  is rotated after the developing cartridge  7  has been installed in the main body casing  2 , the detection protrusion  81  can be changed from the collapsed state to the extended state, enabling the detection mechanism  101  to detect the detection protrusion  81  placed in the extended state. 
     The developing cartridge  7  has the agitator gear  49  used to transmit the rotation driving force, which is output from the input gear  45 , to the reset gear  50 . The missing tooth gear part  68  to which the rotation driving force is transmitted from the agitator gear  49  is formed on the reset gear  50 . The transmission of the rotation driving force from the agitator gear  49  to the missing tooth gear part  68  is discontinued at least when the detection protrusion  81  is positioned at the terminal position. 
     Accordingly, it is possible to stop the detection protrusion  81  at the terminal position and to maintain the state in which the detection protrusion  81  is stopping at the terminal position. 
     The developing cartridge  7  has the opposite part  84  with the linear part  902  used to change the detection protrusion  81  from the extended state to the collapsed state. 
     Accordingly, it is possible to change the detection protrusion  81  from the extended state to the collapsed state and place the detection protrusion  81  in the collapsed state at the terminal position. When the developing cartridge  7  is removed from the main body casing  2 , therefore, the detection protrusion  81  is made less likely to come into contact with other members and the wear and damage of the detection protrusion  81 , which is caused by the contact, can thereby be reduced. 
     The linear part  902  intersects a circular track drawn by a portion of the detection protrusion  81 , which moves when the reset gear  50  rotates, the portion first abutting the protrusion falling cam member. When the detection protrusion  81  moves while sliding on the linear part  902  due to the rotation of the reset gear  50 , the detection protrusion  81  superiorly changes from the extended state to the collapsed state. 
     Although an embodiment of the present disclosure has been described so far, the present disclosure is not limited to the structure described above. 
     In the structure described above, the detection protrusion  81  is placed in the collapsed state with it positioned at the terminal position, as shown in  FIG. 15 . 
     As shown in  FIG. 17 , however, the detection protrusion  81  may be placed in the extended state with it positioned at the terminal position. In this case, it is desirable to predetermine the terminal position so that with the detection protrusion  81  positioned at the terminal position, the central axial line of the swinging axis part  813  extends in a direction substantially orthogonal to a direction A in which the developing cartridge  7  is installed in and removed from the main body casing  2 . 
     Accordingly, when the developing cartridge  7  is removed from the main body casing  2 , if the detection protrusion  81  abuts another member and a force is applied to the detection protrusion  81 , the detection protrusion  81  changes from the extended state to the collapsed state. Therefore, it can be reduced that the detection protrusion  81  is strongly rubbed and the wear of the detection protrusion  81  can thereby be reduced. Since the force applied to the detection protrusion  81  can be released, the damage to the detection protrusion  81  can also be reduced. 
     In addition, in the structure according to the embodiment described above, the reset gear  50  has the missing tooth gear part  68  and the gear teeth  70  are formed on the outer circumferential surface of the missing tooth gear part  68 . 
     Instead of the missing tooth gear part  68 , a main body  181  in a sector plate shape centered around the cylindrical boss  69  and a resistance applying member  182  wound on the outer circumference of the main body  181  may be provided as shown in  FIG. 18 , at least the outer circumferential surface of the resistance applying member  182  being made of rubber or another material having a relatively large frictional coefficient. In this case, gear teeth may or may not be formed on the circumferential surface of the small-diameter gear part  65  of the agitator gear  49 . The main body  181  and resistance applying member  182  are formed so as to have a size that prevents a portion  182 B, which is formed on the outer circumferential surface of the resistance applying member  182  and is recessed relatively inside in a radial direction, from coming into contact with the small-diameter gear part  65  and allows an arc surface  182 A, which is formed on the outer circumferential surface of the resistance applying member  182  and is placed relatively outside in a radial direction, to come into contact with the circumferential surface of the small-diameter gear part  65 . 
     Although the developing cartridge  7  in the structure according to the embodiment described above has the gear cover  43 , the gear teeth  70  may be eliminated (a structure in which the reset gear  50  is exposed may be used) as long as the detection protrusion  81  provided on the reset gear  50  is changeable between the extended state and the collapsed state. 
     While certain aspects of the disclosure have been shown and described with reference to certain illustrative embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.