Abstract:
An image forming apparatus includes: an electrostatic latent image bearing member; a toner cartridge; a developing member; a transfer member; a developing device; a toner-circulating member; a drive-force output unit; and a circulating-member driving unit. The toner cartridge is removably coupled to the developing device. The toner-circulating member is incorporated in the developing device and circulates toner between the developing device and the toner cartridge. The drive-force output unit is provided in the toner cartridge and is configured to output to the developing device a drive force for driving the toner-circulating member. The circulating-member driving unit is provided in the developing device and is configured to drive the toner-circulating member upon receiving the drive force outputted from the drive-force output unit while the toner cartridge is being coupled to the developing device.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims priority from Japanese Patent Application No. 2005-53070 filed Feb. 28, 2005, the entire content of which is hereby incorporated by reference.  
       TECHNICAL FIELD  
       [0002]     The disclosure relates to an image forming apparatus of an electronic photographic type, in which an electrostatic latent image formed on an electrostatic latent image bearing body is developed into a toner image, and the toner image is transferred to a recording medium, and to a cartridge that can be used in the image forming apparatus.  
       BACKGROUND  
       [0003]     There has been proposed an image forming apparatus of a type that includes: an electrostatic latent image bearing body having an electrostatic latent image formed thereon; a toner cartridge containing toner; a developing member for supplying toner from the toner cartridge to the electrostatic latent image bearing body, thereby developing the electrostatic latent image into a toner image; a transfer member for transferring the toner image from the electrostatic latent image bearing body to a recording medium; and a developing device which incorporates at least the developing member and in which the toner cartridge is removably provided.  
         [0004]     In the image forming apparatus of this type, after an electrostatic latent image is formed on the electrostatic latent image bearing body, the developing member supplies the toner from the toner cartridge onto the electrostatic latent image bearing body, thereby developing the latent image. Then, the transfer member transfers the toner image from the electrostatic latent image bearing body to a recording medium. As a result, an image corresponding to the electrostatic latent image is formed on the recording medium.  
         [0005]     Since the toner cartridge can be removed from the developing device that incorporates the developing member, the toner cartridge can be replaced by a new one when toner is consumed up, thereby continuing image forming.  
       SUMMARY  
       [0006]     It is desirable to ensure that some components in the developing device will not operate while the toner cartridge remains disconnected from the developing device.  
         [0007]     U.S. Pat. No. 5,867,756 has proposed an image forming apparatus of this type, in which toner-circulating members, such as auger rollers, are provided in the housing to circulate toner between the developing device and the toner cartridge. This prevents toner from accumulating or coagulating at a particular position. Sufficient fluidity of toner can be ensured.  
         [0008]     In this type of developing device provided with the toner-circulating members, however, if the toner-circulating members are erroneously driven while the toner cartridge remains removed from the developing device, the pressure on the toner in the developing device will rise, and consequently, the toner will overflow through a gap formed in the developing device. It is therefore desirable to ensure that the toner-circulating members will not operate while the toner cartridge remains disconnected from the developing device.  
         [0009]     In view of the foregoing, an object of the invention is to provide an image forming apparatus that has a developing device and a toner cartridge and that can ensure that at least one component in the developing device will not operate while the toner cartridge remains disconnected from the developing device, and to provide the toner cartridge.  
         [0010]     Another object of the invention is to provide a development cartridge and a process cartridge that can ensure that at least one component in the cartridge will not operate while the toner cartridge remains disconnected from the cartridge.  
         [0011]     In order to attain the above and other objects, the invention provides an image forming apparatus, including: an electrostatic latent image bearing member; a toner cartridge; a developing member; a transfer member; a developing device; a toner-circulating member; a drive-force output unit; and a circulating-member driving unit. The electrostatic latent image bearing member has an electrostatic latent image formed thereon. The toner cartridge contains toner. The developing member supplies the toner from the toner cartridge onto the electrostatic latent image bearing member, thereby developing the electrostatic latent image into a toner image. The transfer member transfers the toner image from the electrostatic latent image bearing member to a recording medium. The toner cartridge is removably coupled to the developing device. The developing device incorporates the developing member. The toner-circulating member is incorporated in the developing device and circulates toner between the developing device and the toner cartridge. The drive-force output unit is provided in the toner cartridge and is configured to output to the developing device a drive force for driving the toner-circulating member. The circulating-member driving unit is provided in the developing device and is configured to drive the toner-circulating member upon receiving the drive force outputted from the drive-force output unit while the toner cartridge is being coupled to the developing device.  
         [0012]     According to another aspect, the invention provides a toner cartridge, which is capable of being removably coupled to a development cartridge that includes a developing member, the toner cartridge including: a casing defining a toner containing portion that contains toner; a drive-force input unit to which a drive force is inputted; and a drive-force output unit that is configured to output the drive force.  
         [0013]     According to another aspect, the invention provides a development cartridge which is capable of being detachably mounted in an image forming apparatus, the development cartridge including: a casing; a developing member that is mounted in the casing and that supplies toner from a toner cartridge to an electrostatic latent image bearing member, on which an electrostatic latent image is formed, thereby developing the electrostatic latent image into a toner image; a toner-circulating member that circulates toner; and a circulating-member driving unit that is configured to drive the toner-circulating member upon receiving a drive force from the toner cartridge.  
         [0014]     According to another aspect, the invention provides a process cartridge which is capable of being detachably mounted in an image forming apparatus, the process cartridge including: a casing; an electrostatic latent image bearing member provided in the casing, an electrostatic latent image being formed on the electrostatic latent image bearing member; a developing member that is mounted in the casing and that supplies toner from the toner cartridge to the electrostatic latent image bearing member, thereby developing the electrostatic latent image formed on the electrostatic latent image bearing member into a toner image; a toner-circulating member that circulates toner; and a circulating-member driving unit that is configured to drive the toner-circulating member upon receiving a drive force transmitted from the toner cartridge.  
         [0015]     According to another aspect, the invention provides an image forming apparatus, including: an electrostatic latent image bearing member; a toner cartridge; a developing member; a transfer member; a developing device; and a drive-force output unit. The electrostatic latent image bearing member has an electrostatic latent image formed thereon. The toner cartridge contains toner. The developing member supplies the toner from the toner cartridge onto the electrostatic latent image bearing member, thereby developing the electrostatic latent image into a toner image. The transfer member transfers the toner image from the electrostatic latent image bearing member to a recording medium. The toner cartridge is removably coupled to the developing device. The developing device incorporates the developing member. The drive-force output unit is provided in the toner cartridge and is configured to output a drive force to the developing device while the toner cartridge is being coupled to the developing device.  
         [0016]     According to another aspect, the invention provides a development cartridge which is capable of being detachably mounted in an image forming apparatus, the development cartridge including: a casing; a developing member that is mounted in the casing and that supplies toner from a toner cartridge to an electrostatic latent image bearing member, on which an electrostatic latent image is formed, thereby developing the electrostatic latent image into a toner image; and a drive-force receiving unit that is configured to receive a drive force from the toner cartridge while the toner cartridge is being coupled to the casing.  
         [0017]     According to another aspect, the invention provides a process cartridge which is capable of being detachably mounted in an image forming apparatus, the process cartridge including: a casing; an electrostatic latent image bearing member provided in the casing, an electrostatic latent image being formed on the electrostatic latent image bearing member; a developing member that is mounted in the casing and that supplies toner from a toner cartridge to the electrostatic latent image bearing member, thereby developing the electrostatic latent image formed on the electrostatic latent image bearing member into a toner image; and a drive-force receiving unit that is configured to receive a drive force transmitted from the toner cartridge while the toner cartridge is being coupled to the casing. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]     Illustrative aspects in accordance with the invention will be described in detail with reference to the following figures wherein:  
         [0019]      FIG. 1  is a perspective view of a laser printer according to an illustrative aspect of the invention;  
         [0020]      FIG. 2  is a perspective view of the laser printer, illustrating how a lid of the laser printer is opened;  
         [0021]      FIG. 3  is a perspective view of the laser printer, illustrating how a sheet cassette is pulled out of the main body of the laser printer;  
         [0022]      FIG. 4  is a sectional view of the laser printer, taken along a line IV-IV in  FIG. 2 , showing the internal structure thereof;  
         [0023]      FIG. 5  is a sectional view of the laser printer, illustrating how a photosensitive-drum cartridge, a development cartridge, and a toner cartridge are removed, as an integral unit, from the main body of the laser printer;  
         [0024]      FIG. 6  is a sectional view of the laser printer, illustrating how the toner cartridge is disconnected from the development cartridge;  
         [0025]      FIG. 7  is a sectional view of the laser printer, illustrating how only the toner cartridge is removed from the main body of the laser printer;  
         [0026]      FIG. 8  is a sectional view of the laser printer, illustrating how the development cartridge and the toner cartridge are removed, as an integral unit, from the main body of the laser printer;  
         [0027]      FIG. 9  is a left-side view of the photosensitive-drum cartridge, from which the development cartridge and the toner cartridge are removed;  
         [0028]      FIG. 10  shows the configuration on the inner surface of a left-side wall in the main body of the laser printer;  
         [0029]      FIG. 11  is a left-side view showing the toner cartridge and the development cartridge when they are coupled with each other;  
         [0030]      FIG. 12A  is a front view of a toner-cartridge holder in the development cartridge as viewed from the toner cartridge side when the toner cartridge is disconnected from the development cartridge;  
         [0031]      FIG. 12B  is a rear view of the toner cartridge as viewed from the toner-cartridge holder side when the toner cartridge is disconnected from the development cartridge;  
         [0032]      FIG. 12C  is a front view of a toner-cartridge holder in the development cartridge as viewed from the toner cartridge side when the toner cartridge is coupled to the development cartridge;  
         [0033]      FIG. 12D  is a rear view of the toner cartridge as viewed from the toner-cartridge holder side when the toner cartridge is coupled to the development cartridge;  
         [0034]      FIG. 13  is a right-side view showing the toner cartridge and the development cartridge when they are coupled with each other;  
         [0035]      FIG. 14  is a cross-sectional view of the development cartridge, taken along a line in which auger rollers are arranged;  
         [0036]      FIG. 15  is an enlarged view showing the configuration on a part of the inner surface of the left-side wall in the main body of the laser printer shown in  FIG. 10 ;  
         [0037]      FIG. 16  is a left-side view showing the configuration of the toner cartridge and the development cartridge according to an additional aspect;  
         [0038]      FIG. 17A  is a left-side view showing the configuration of the toner cartridge and the development cartridge according to another additional aspect;  
         [0039]      FIG. 17B  is a right-side view showing the toner cartridge and the development cartridge according to the other additional aspect;  
         [0040]      FIG. 17C  is a right-side view showing the toner cartridge and the development cartridge according to the other additional aspect, showing some gears that are hidden, not indicated in  FIG. 17B ; and  
         [0041]      FIG. 17D  is a sectional view illustrating the inner structures of the toner cartridge and development cartridge according to the other additional aspect. 
     
    
     DETAILED DESCRIPTION  
       [0042]     An image forming apparatus according to some aspects of the invention will be described while referring to the accompanying drawings wherein like parts and components are designated by the same reference numerals to avoid duplicating description.  
         [0043]      FIG. 1  is a perspective view representing the outer appearance of a laser printer  1  according to this aspect.  
         [0044]     The terms “upward”, “downward”, “upper”, “lower”, “above”, “below”, “beneath”, “left”, “right” and the like will be used throughout the description assuming that the laser printer  1  is disposed in an orientation in which it is intended to be used. In use, the laser printer  1  is disposed as shown in  FIG. 1 . The left-and-right direction defined in the laser printer  1  is equivalent to the widthwise direction of a sheet of paper that is conveyed in the laser printer  1 .  
         [0045]     As shown in  FIG. 1 , a cover  2  is provided covering the outer periphery of the main body of the laser printer  1 . A sheet cassette  3  is mounted below the cover  2 .  
         [0046]     As shown in  FIG. 2 , the cover  2  defines an opening  2   a  at its front side, and has a lid  4  that can open and close the opening  2   a . Usually, the lid  4  closes the opening  2   a  as shown in  FIG. 1 .  
         [0047]     The lid  4  has finger rests  4   a  on the upper left and right sides, respectively. The user may hold the lid  4 , placing his or her fingers in the finger rests  4   a , and then pull the lid  4 . As a result, as shown in  FIG. 2 , the lid  4  rotates around a hinge  4   b , that is located at the lower edge of the lid  4 , and opens the opening  2   a.    
         [0048]     As shown in  FIG. 3 , the sheet cassette  3  can be pulled out forwardly from the main body of the laser printer  1 . Thus, the sheet cassette  3  can be removed from the main body of the laser printer  1 .  
         [0049]     As shown in  FIG. 4 , a spring  6  and a support plate  5  are mounted in the sheet cassette  3 . The spring urges the support plate  5  upwardly. A sheet-feeding roller  9  is provided above the front edge of the support plate  5 . The sheet-feeding roller  9  is for feeding, one at a time, paper sheets (not shown) that are stuck on the support plate  5  toward an image forming unit  7 . Along a sheet conveying path from the sheet-feeding roller  9  to the image forming unit  7 , a transport roller  11 , a guide  13 , and a pair of registration rollers  14  and  15  are arranged in this order. The transport roller  11  cooperates with the sheet-feeding roller  9  to transport paper sheets. The guide  13  receives a paper sheet transported by the transport roller  11  and turns back the sheet by about 180° along the outer circumference of the transport roller  11 . The registration rollers  14  and  15  stop rotating at appropriate timings to catch the leading edge of a paper sheet and eliminate a skew of the paper sheet.  
         [0050]     The image forming unit  7  includes a photosensitive drum  21  and a transfer roller  22 . The photosensitive drum  21  and the transfer roller  22  are mounted in a photosensitive-drum cartridge  20 . The transfer roller  22  is opposed to the photosensitive drum  21 . A toner image is formed on a paper sheet as the sheet passes through the nip between the photosensitive drum  21  and the transfer roller  22 . The paper sheet is then supplied to a fixing unit  31 .  
         [0051]     In the fixing unit  31 , the toner image on the sheet is fixed as the sheet passes through the nip between a heating roller  33  and a pressing roller  35 . The sheet, on which the image is now fixed, is transported by a pair of transport rollers  36 .  
         [0052]     A guide  37  is provided to guide the paper sheet that has been transported by the rollers  36 , toward the top of the cover  2 . A pair of sheet-discharging rollers  38  discharge the paper sheet onto a sheet tray  39  that is provided on the upper surface of the cover  2 .  
         [0053]     A scanner unit  90  is provided between the sheet tray  39  and the photosensitive-drum cartridge  20 . The scanner unit  90  is for scanning the photosensitive drum  21  with a laser beam L.  
         [0054]     Next, the image forming unit  7  and the scanner unit  90  will be described in more detail.  
         [0055]     The photosensitive drum  21  is rotatably supported in the photosensitive-drum cartridge  20 . The photosensitive drum  21  has a photosensitive layer on the circumferential surface thereof. The transfer roller  22 , a scorotron charger  23 , and a paper-dust recovering brush  24  are also mounted in the photosensitive-drum cartridge  20 . The scorotron charger  23  is for electrically charging the surface of the photosensitive drum  21  uniformly. The photosensitive-drum cartridge  20  is formed with an exposure opening  20   a . The laser beam L emitted from the scanner unit  90  enters the photosensitive-drum cartridge  20  through the exposure opening  20   a . The laser beam L forms an electrostatic latent image on the photosensitive drum  21 .  
         [0056]     A leaf spring  26  is provided on the photosensitive-drum cartridge  20  to hold a development cartridge  40  on the photosensitive drum cartridge  20 ,. A handle  25  is provided on the front free end of the leaf spring  26 . The development cartridge  40  is detachably mounted on the photosensitive drum cartridge  20 . A developing roller  41  is rotatably mounted in the development cartridge  40 . The developing roller  41  supplies toner onto the surface of the photosensitive drum  21 , thereby developing the electrostatic latent image into a toner image on the photosensitive drum  21 . The toner image is then transferred from the photosensitive drum  21  onto the paper sheet when the paper sheet is passing through the nip between the photosensitive drum  21  and the transfer roller  22 .  
         [0057]     The paper-dust recovering brush  24  is in abutment contact with the surface of the photosensitive drum  21  at its location downstream, in the rotating direction of the photosensitive drum  21 , from the location where the toner image is transferred from the photosensitive drum  21  to the paper sheet. The brush  24  is applied with a positive bias, and removes negatively-charged paper dust from the photosensitive drum  21 .  
         [0058]     As shown in  FIG. 4 , the developing roller  41  is rotatably supported in the development cartridge  40 . The developing roller  41  is driven by a mechanism (later described), while in contact with the photosensitive drum  21 .  
         [0059]     More specifically, the development cartridge  40  has a developing section  40   a  and a toner-cartridge holding section  40   b . In the developing section  40   a , the developing roller  41 , an upper auger roller  43 , a lower auger roller  44 , a toner-supplying roller  45 , and a developing blade  47  are mounted in the development cartridge  40 .  
         [0060]     The development cartridge  40  has a toner-cartridge holder  42  in the toner-cartridge holding section  40   b.    
         [0061]     The toner-cartridge holder  42  is of a hollow cylindrical shape that has a peripheral side wall and a pair of end walls (right-side and left-side end walls), with the front parts of the peripheral side wall and the end walls being opened. The toner-cartridge holder  42  is for detachably supporting a toner cartridge  60  on its inner surface, with the front side of the toner cartridge  60  being exposed. The toner-cartridge holder  42  is formed with an opening  42   a  as shown in  FIG. 7 . Toner is supplied through the opening  42   a  from the toner cartridge  60  into the developing section  40   a.    
         [0062]     As shown in  FIG. 14 , the auger rollers  43  and  44  are for receiving toner from the toner cartridge  60  through the opening  42   a , which confronts the axial middle parts of the auger rollers  43  and  44 ,. The auger rollers  43  and  44  circulate toner along the axial directions thereof between the left and right side ends thereof.  
         [0063]     The toner-supplying roller  45  is for receiving toner from the upper and lower auger rollers  43  and  44  and for supplying toner to the developing roller  41 . The developing blade  47  is for electrically charging by friction toner that is supplied from the toner-supplying roller  45  onto the surface of the developing roller  41  and for forming a thin layer of toner on the developing roller  41 .  
         [0064]     An agitator  61  is rotatably supported in the toner cartridge  60 . The agitator  61  rotates around its rotational shaft  61 a to stir the toner in the toner cartridge  60  to supply the toner to the development cartridge  40 .  
         [0065]     The scanner unit  90  will be described below.  
         [0066]     The scanner unit  90  includes a polygon mirror  91 , two mirrors  92  and  93 , an fθ lens  95 , and a cylindrical lens  97 . The polygon mirror  91  deflects and scans the laser beam L that is emitted from a laser emitting unit (not shown). The mirrors  92  and  93  reflect the laser beam L, guiding the beam L to the photosensitive drum  21 . The fθ lens  95  is located on an optical path that extends from the polygon mirror  91  to the mirror  92 . A cylindrical lens  97  is located on another optical path that extends from the mirror  92  to the mirror  93 .  
         [0067]     The laser unit (not shown) intermittently emits a laser beam L at appropriate timings, while the polygon mirror  91  and the photosensitive drum  21  are being rotated. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum  21 . The developing roller  41  supplies toner to the photosensitive drum  21 , thereby developing the electrostatic latent image into a toner image. The toner image is then transferred from the photosensitive drum  21  onto a paper sheet. Thus, an image is formed on the paper sheet according to an electronic photography method.  
         [0068]     As shown in  FIG. 5 , when the user opens the lid  4  and pulls the handle  25  provided on the photosensitive-drum cartridge  20 , the photosensitive-drum cartridge  20  is removed from the main body of the laser printer  1 , together with the development cartridge  40  and the toner cartridge  60 , through the opening  2   a.    
         [0069]     The toner cartridge  60  has a handle  62 . When the user rotates the handle  62  upwards to a disconnecting position shown in  FIG. 6 , the toner cartridge  60  is disconnected from the development cartridge  40  in a manner described later. The user then pulls the handle  62 , whereby only the toner cartridge  60  is removed from the main body of the laser printer  1  through the opening  2   a , as is illustrated in  FIG. 7 .  
         [0070]     As shown in  FIG. 8 , when the user pushes down the handle  25  on the photosensitive-drum cartridge  20 , the leaf spring  26  is pushed down. The user then pulls the handle  62  forwardly without rotating the handle  62  upwards. In this case, the toner cartridge  60  and the development cartridge  40  are detached together, as an integral unit, from the photosensitive-drum cartridge  20  as shown in  FIG. 8 , and are removed from the main body of the laser printer  1  through the opening  2   a.    
         [0071]     Next, the respective components in the image forming unit  7  will be described in detail.  
         [0072]     As described above, the handle  25  is fixedly secured to the photosensitive-drum cartridge  20  via the leaf spring  26 . As shown in  FIG. 9 , the leaf spring  26  is bent upwardly at its midpoint, providing a bent part  26   a  that is shaped like a step. When the development cartridge  40  is mounted on the photosensitive-drum cartridge  20  as shown in  FIG. 4 , the bent part  26   a  comes into engagement with the lower edge of the toner-cartridge holder  42 , as a result of which the development cartridge  40  is coupled to the photosensitive-drum cartridge  20 . When the handle  25  is pushed down as described above (see  FIG. 8 ), the bent part  26   a  disengages from the lower edge of the toner-cartridge holder  42 . Hence, the development cartridge  40  can be coupled to, and disconnected from, the photosensitive-drum cartridge  20 .  
         [0073]     As shown in  FIG. 9 , the photosensitive drum  21  has a metal rotational shaft  21   a , which projects outwardly from both of the left and right sides of the photosensitive-drum cartridge  20 . A gear  21   b  is provided on the left-side end of the photosensitive drum  21 . The gear  21   b  rotates integrally with the photosensitive drum  21 . The gear  21   b  protrudes from the rear end of the photosensitive-drum cartridge  20 .  
         [0074]     As shown in  FIG. 10 , a guide groove  121  is formed on the inner surface of the left-side wall in the main body of the laser printer  1 . The guide groove  121  is for guiding the rotational shaft  21   a  of the photosensitive drum  21 . A gear  121   b  is provided in the main body of the laser printer  1 . When the photosensitive-drum cartridge  20  is set in position in the main body of the laser printer  1 , the gear  121   b  is in engagement with the gear  21   b . Accordingly, a drive force is transmitted from the main body of the laser printer  1  to the photosensitive drum  21 .  
         [0075]     As shown in  FIG. 11 , a drive shaft  51  is provided on the left side of the development cartridge  40  at the developing section  40   a . The drive shaft  51  is for receiving a drive force from a drive shaft  151 , which is provided on the inner surface of the left-side wall in the main body of the laser printer  1  as shown in  FIG. 10 . The drive shaft  151  has a plate-shaped projection  151   a  on its axial tip end. The drive shaft  51  has a hollow cylindrical portion at its axial tip end; and a pair of projections  51   a  that are provided within the hollow cylindrical portion. The pair of projections  51   a  can engage with the plate-shaped projection  151   a  of the drive shaft  51 . Thus, the drive shaft  151  can be fitted in the drive shaft  51 . The drive shafts  51  and  151  constitute a so-called drive coupling.  
         [0076]     As shown in  FIG. 11 , a gear  51   b  is fixedly mounted on the drive shaft  51 . The gear  51   b  is located on the outer side of the left-side wall of the development cartridge  40  at the developing section  40   a . The gear  51   b  rotates integrally with the drive shaft  51 .  
         [0077]     A rotational shaft  41   b  of the developing roller  41  and a rotational shaft of the toner-supplying roller  45  protrude outwardly from the left-side wall of the development cartridge  40 . A gear  41   a  is fixed on the left-side end of the rotational shaft  41   b , and rotates integrally with the developing roller  41 . A gear  45   a  is fixed on the left-side end of the rotational shaft of the toner-supplying roller  45 , and rotates integrally with the toner-supplying roller  45 . Thus, the gears  41   a  and  45   a  are located on the outer side of the left-side wall of the development cartridge  40  at the developing section  40   a . The gear  51   b  is in engagement with both of the gear  41   a  and the gear  45   a.    
         [0078]     The toner cartridge  60  can be connected to and disconnected from the development cartridge  40 .  FIGS. 12A and 12B  show the state where the toner cartridge  60  is disconnected from the development cartridge  40 , that is, the handle  62  of the cartridge  60  has been rotated upwards to the disconnecting position as of  FIG. 6 .  FIG. 12A  shows the toner-cartridge holder  42  in the development cartridge  40 , as viewed from the toner cartridge  60  side, and  FIG. 12B  shows the toner cartridge  60  as viewed from the toner-cartridge holder  42  side.  
         [0079]     As shown in  FIG. 12B , the toner cartridge  60  has an inner cylinder  63  and an outer cylinder  64 .  
         [0080]     The inner cylinder  63  is a longitudinal hollow cylinder-shaped casing that has a peripheral side wall and a pair of opposite end walls (right-side and left-side end walls). The inner cylinder  63  contains toner therein. The rotational shaft  61   a  of the agitator  61  extends along the central axis of the inner cylinder  63 . The rotational shaft  61   a  protrudes outwardly from the pair of opposite end walls (right-side and left-side end walls) of the inner cylinder  63 . A gear  61   b  is provided on the right-side end of the rotational shaft  61   a  and is therefore located on the outer side of the right-side end wall of the inner cylinder  63 . The gear  61   b  rotates integrally with the rotational shaft  61   a.    
         [0081]     The outer cylinder  64  is coaxial with the inner cylinder  63  and surrounds the axial central part of the inner cylinder  63 . The inner and outer cylinders  63  and  64  are supported by the cylindrical toner-cartridge holder  42  coaxially.  
         [0082]     The outer cylinder  64  has an elongated projection  64   a  on its outer peripheral surface. The elongated projection  64   a  projects toward the inner peripheral surface of the toner-cartridge holder  42 . The toner-cartridge holder  42  has an elongated groove  42   b  on its inner peripheral surface. The outer cylinder  64  is supported by the toner-cartridge holder  42 , with the projection  64   a  being fitted in the elongated groove  42   b . Hence, the outer cylinder  64  is fixedly secured to the toner-cartridge holder  42  and cannot rotate relative to the outer cylinder  64 .  
         [0083]     The handle  62  is formed integrally with the inner cylinder  63 . The inner cylinder  63  can rotate around its central axis relative to the outer cylinder  64  when the user operates the handle  62  to move the handle  62  upwardly or downwardly.  
         [0084]     As shown in  FIG. 12A , a pair of rails  42   c  are provided on the inner peripheral surface of the toner-cartridge holder  42 . A shutter  48  made of metal is slidably mounted on the pair of rails  42   c  at its pair of opposite ends. The shutter  48  is of a rectangular shape that is elongated in the axial direction of the toner-cartridge holder  42 . The shutter  48  can move along the circumference of the cylindrical toner-cartridge holder  42 , between the closing position where the shutter  48  closes the opening  42   a  as shown in  FIG. 12A  and the opening position where the shutter  48  is shifted upwardly from the opening  42   a  to expose the opening  42   a  as shown in  FIG. 12C .  
         [0085]     Two pairs of projections  63   a  are provided on the outer peripheral surface of the inner cylinder  63 . The two pairs of projections  63   a  are separate from each other in the circumferential direction of the inner cylinder  63  as sandwiching the shutter  48  therebetween. Two projections  63   a  constituting each pair are separate from each other in the axial direction of the inner cylinder  63  and confront the two opposite longitudinal ends of the shutter  48 . As the inner cylinder  63  rotates, the two pairs of projections  63   a  move the shutter  48  while holding it therebetween in the circumferential direction along the inner peripheral surface of the toner-cartridge holder  42 . When the handle  62  is rotated to the disconnecting position shown in  FIG. 6 , the shutter  48  closes the opening  42   a  as shown in  FIG. 12A .  
         [0086]     The elongated groove  42   b  is located on the inner peripheral surface of the toner-cartridge holder  42  at a position below the shutter  48  and not overlapping the shutter  48  even when the shutter  48  is moved to its lowest position shown in  FIG. 12A  to completely close the opening  42   a.    
         [0087]     The opening  42   a  is of a rectangular shape that is elongated in the axial direction of the toner-cartridge holder  42 . A sponge member  49  in a rectangular frame shape is bonded to the inner peripheral surface of the toner-cartridge holder  42  around the opening  42   a.    
         [0088]     A pair of engagement members  63   c  are formed on the outer peripheral surface of the inner cylinder  63  integrally with the inner cylinder  63 . The pair of engagement members  63   c  are provided on the inner cylinder  63  at such locations that the engagement members  63   c  can engage with the pair of rails  42   c  when the handle  62  of the inner cylinder  63  is in a coupling position shown in  FIG. 4 . It is noted that each rail  42   c  has an L-shaped cross-section, while each engagement member  63   c  has a cross-sectional shape that can be engaged with the L-shaped cross-section of the corresponding rail  42   c.    
         [0089]     The outer cylinder  64  is formed with an opening  64   b  that has the same shape as the opening  42   a . The opening  64   b  is provided in the outer cylinder  64  at such a position that the opening  64   b  will confront the opening  42   a  when the outer cylinder  64  is mounted in the toner-cartridge holder  42  with the elongated projection  64   a  being fitted in the elongated groove  42   b . A sponge member  65  in the same shape with the sponge member  49  is bonded to the outer peripheral surface of the outer cylinder  64  around the opening  64   b.    
         [0090]     The inner cylinder  63  is formed with an opening  63   b  that has the same shape with the opening  64   b . As shown in  FIG. 12B , the openings  64   b  and  63   b  do not overlap with each other when the handle  62  is in the disconnecting position of  FIG. 6 . This ensures that toner will not come out from the toner cartridge  60  when the toner cartridge  60  is removed from the development cartridge  40  as shown in  FIG. 7 .  
         [0091]     The handle  62  of the toner cartridge  60  can be rotated from the disconnecting position of  FIG. 6  downwards to the coupling position shown in  FIG. 4 , while maintaining the projection  64   a  to be fitted in the elongated groove  42   b . As a result, the openings  64   b  and  63   b  become overlapping with each other as shown in  FIG. 12D , and the projections  63   a  push up the shutter  48  from the opening  42   a  as shown in  FIG. 12C . As a result, the inside of the inner cylinder  63  is brought into fluid communication with the inside of the developing section  40   a  of the development cartridge  40 . Toner can therefore be supplied from the toner cartridge  60  to the developing section  40   a  in the development cartridge  40 .  
         [0092]     At this time, the sponge members  49  and  65  come into firm contact with each other, and the engagement members  63   c  are engaged with the rails  42   c . Accordingly, the entire periphery of the openings  64   b  and  42   a  are tightly sealed, allowing no toner to come outside When the engagement members  63   c  are thus engaged with the rails  42   c , the development cartridge  40  and the toner cartridge  60  are coupled to each other as shown in  FIG. 4 . Accordingly, the cartridges  40  and  60  can be removed and inserted, as an integral unit, from and onto the photosensitive-drum cartridge  20  as shown in  FIG. 8 . Thus, the cartridges  40  and  60  can be removed and inserted, as an integral unit, from and into the main body of the laser printer  1  as shown in  FIG. 8 .  
         [0093]     The handle  62  may be operated to rotate the inner cylinder  63  to release the engagement members  63   c  from the rails  42   c . Thus, the development cartridge  40  and the toner cartridge  60  can be disconnected from each other. Accordingly, only the toner cartridge  60  can be removed from the laser printer  1  as shown in  FIG. 7 .  
         [0094]     As shown in  FIG. 12A  and  FIG. 13 , a gear  53  is mounted on the inner side of the right-side end wall of the toner-cartridge holder  42 . The gear  53  is engaged with the gear  61   b  when the toner cartridge  60  is set in the toner-cartridge holder  42 .  
         [0095]     As shown in  FIG. 14 , the upper auger roller  43  and the lower auger roller  44  protrude outwardly from the right-side wall of the development cartridge  40 . As shown in  FIGS. 13 and 14 , gears  43   a  and  44   a  are attached to the right-side ends of the upper auger roller  43  and the lower auger roller  44 , respectively. Accordingly, the gears  43   a  and  44   a  are located on the outer side of the right-side wall of the development cartridge  40 . The gears  43   a  and  44   a  rotate integrally with the upper auger roller  43  and the lower auger roller  44 , respectively. The gear  53  is in engagement with both of the gears  43   a  and  44   a.    
         [0096]     As shown in  FIG. 10 , a drive shaft  161  is provided on the inner surface of the left-side wall in the main body of the printer  1 . The drive shaft  161  and the rotational shaft  61   a  of the agitator  61  shown in  FIG. 11  constitute a so-called drive coupling. More specifically, the drive shaft  161  has a plate-shaped projection  161   a  on its axial tip end. The rotational shaft  61   a  has a hollow cylindrical portion at its left-side axial tip end, and a pair of projections  61   c  provided within the hollow cylindrical portion. The pair of projections  61   c  can engage with the plate-shaped projection  161   a  of the drive shaft  161 . Thus, the drive shaft  161  can be fitted in the rotational shaft  61   a.    
         [0097]     The agitator  61  is rotated when a drive force is transmitted to the rotational shaft  61   a  from the drive shaft  161 . The drive force is transmitted from the gear  61   b  to the gear  53 , and then from the gear  53  to the gears  43   a  and  44   a . As a result, the auger rollers  43  and  44  are rotated.  
         [0098]     As shown in  FIG. 14 , the upper auger roller  43  and lower auger roller  44  have spiral blades  43   b  and  44   b , respectively. When the agitator  61  is driven, the lower auger roller  44  transports toner from the opening  42   a  to the left and right sides of the development cartridge  40 , and the upper auger roller  43  transports toner from the left and right sides of the development cartridge  40  back to the middle part of the cartridge  40 , as indicated by arrows in the figure. The toner can therefore be recovered from the right and left sides of the development cartridge  40  to the middle part thereof and returned back to the toner cartridge  60  through the opening  42   a.    
         [0099]     Therefore, the toner can not only be circulated in the development cartridge  40 , but also be supplied back and forth between the development cartridge  40  and the toner cartridge  60 . This prevents degraded toner from accumulating at a particular position to be firmly adhered thereto, thereby maintaining fluidity of toner As shown in  FIG. 14 , a partition wall  55  is provided in the development cartridge  40  at a location between the upper auger roller  43  and the lower auger roller  44 . The partition wall  55  helps to transport toner smoothly.  
         [0100]     Next will be described, with reference to  FIG. 15 , the drive system that is provided on the left-side wall in the main body of the laser printer  1  to drive the drive shafts  151  and  161 .  
         [0101]     As shown in  FIG. 15 , a gear  151   b , which rotates integrally with the drive shaft  151 , is in engagement with a gear  171 , which rotates integrally with a shaft of an electric motor  170 . Further, a gear  161   b , which rotates integrally with the drive shaft  161 , is in engagement with a gear  172 , which is in engagement with the gear  151   b . With this arrangement, when the electric motor  170  is driven to rotate, both of the drive shafts  151  and  161  rotate at prescribed gear ratios. Hence, the developing roller  41 , toner-supplying roller  45 , upper auger roller  43 , lower auger roller  44  and agitator  61  can be driven simultaneously.  
         [0102]     The drive shafts  151  and  161  are provided on the left-side wall in the main body of the laser printer  1  as being capable of protruding and retracting together. More specifically, the drive shafts  151  and  161  are connected to a link mechanism (not shown), and protrude when the lid  4  is closed and retract when the lid  4  is opened. When the lid  4  is opened, the drive shafts  151  and  161  are brought out of engagement from the drive shaft  51  and rotational shaft  61   a , respectively. Thus, the photosensitive-drum cartridge  20 , development cartridge  40  and toner cartridge  60  can be removed from the main body of the laser printer  1 . On the other hand, when the lid  4  is closed, the drive shafts  151  and  161  are brought into engagement with the drive shaft  51  and rotational shaft  61   a , respectively. As a result, the above-described various components can be driven.  
         [0103]     As shown in  FIGS. 11 and 12 B, a pair of spring receptacles  66  are provided on the outer surface of the inner cylinder  63 . The spring receptacles  66  are located slightly above the left- and right-side ends of the handle  62 . Each spring receptacle  66  has a recess in the middle part in the circumferential direction of the cylinder  63 . As shown in  FIG. 2 , a pair of pushing members  71  project from the rear surface of the lid  4 . Each pushing member  71  is urged in its protruding direction by a spring (not shown) that is installed in the pushing member  71 . The spring receptacles  66  receive the pushing force from the pushing members  71  when the lid  4  is closed. The pushing force reliably holds the cartridges  20 ,  40  and  60  in their mounting positions.  
         [0104]     An interference member  72  also protrudes from the rear surface of the lid  4  at a location between the pair of pushing members  71 . The interference member  72  interferes with the handle  62  unless the handle  62  is placed at the coupling position shown in  FIG. 4 . Hence, the lid  4  cannot be closed until the handle  62  is properly placed at the coupling position.  
         [0105]     As described above, the gear  61   b  will not be engaged with the gear  53  once the toner cartridge  60  is disconnected from the development cartridge  40 . Therefore, no drive force will be transmitted to the upper auger roller  43  or the lower auger roller  44 . As long as the toner cartridge  60  remains disconnected from the development cartridge  40 , the upper auger roller  43  or the lower auger roller  44  will not rotate. This reliably prevents the toner from overflowing the development cartridge  40 . Only when the toner cartridge  60  is mounted on the development cartridge  40 , the gear  61   b  will be engaged with the gear  53  and drive force will be transmitted to the auger rollers  43  and  44 .  
         [0106]     In the above description, the drive shaft  51  can transmit a drive force, driving the developing roller  41  and the toner-supplying roller  45 , even when the toner cartridge  60  remains disconnected from the development cartridge  40 . Thus, both rollers  41  and  45  can be driven to perform various tests for evaluating the performance of the laser printer  1 , without the necessity of coupling the toner cartridge  60  to the development cartridge  40 . In this case also, the upper auger roller  4 . 3  or the lower auger roller  44  is not driven. This reliably prevents the toner from overflowing the development cartridge  40 .  
         [0107]     The drive force for the auger rollers  43  and  44  is inputted from the main body of the laser printer  1  directly to the toner cartridge  60  via the coupling between the drive shafts  61  and  161 . This shortens the force-transmitting path, which in turn helps to reduce the loss of the drive force.  
         [0108]     The drive force for the developing roller  41  and the toner-supplying roller  45  is inputted from the main body of the laser printer  1  directly to the development cartridge  40  via the coupling between the drive shafts  51  and  151 . Accordingly, when the toner cartridge  60  is mounted in the development cartridge  40 , the developing roller  41  and the toner-supplying roller  45  can be controlled and driven independently from the auger rollers  43  and  44 .  
         [0109]     The auger roller  44  supplies toner from the toner cartridge  60  to the development cartridge  40 , and the auger roller  43  recovers toner from the development cartridge  40  to the toner cartridge  60 . Toner can be circulated with a simple structure. This serves to lower the manufacturing cost of the laser printer  1 .  
         [0110]     The left-side tip end of the rotational shaft  61   a  is coupled to the drive shaft  161 , thereby receiving drive force from the drive shaft  161 . The gear  61   b  provided on the right-side tip end of the rotational shaft  61   a  and rotating integrally with the rotational shaft  61   a  serves to output the drive force to the auger rollers  43  and  44 . The agitator  61  rotates integrally with the rotational shaft  61   a . Thus, output of the drive force to the auger rollers  43  and  44  is interlocked with the rotation of the agitator  61 . Accordingly, control of the laser printer  1  is simplified.  
         [0111]     The left-side tip end of the rotational shaft  61   a  couples with the drive shaft  161  to receive the drive force, while the gear  61   b  is provided on the right-side tip end of the rotational shaft  61   a  to output the drive force to the auger rollers  43  and  44 . Thus, the portion receiving the drive force and the portion outputting the drive force are provided on the opposite sides of the toner cartridge  60 . It is possible to easily design the driving system, such as the gear arrangement, that is located near to the driving-force inputting portion and the driving-force outputting portion. It is possible to easily make compact the toner cartridge  60 , the development cartridge  40 , and the laser printer  1 .  
         [0112]     More specifically, in the development cartridge  40 , the developing roller  41  and the auger rollers  43  and  44  have to be arranged close to each other Because the toner-supplying roller  45  has to be further arranged in the development cartridge  40 , one drive mechanism is provided on one side (left side) of the development cartridge  40  to drive the developing roller  41  and the toner-supplying roller  45  and another drive mechanism is provided on the other side (right side) of the development cartridge  40  to drive the auger rollers  43  and  44 . Then, a drive force is transmitted via the toner cartridge  60  (rotational shaft  61   a ) from one side (left side) of the toner cartridge  60  to the other side (right side) thereof. Thus, all of the developing roller  41 , the supplying roller  45 , and the auger rollers  43  and  44  can be driven by the single motor  170 . It is unnecessary to mount two motors each on one side of the development cartridge  40 . It is possible to make compact the laser printer  1 .  
         [0113]     It is noted that the drive shafts  151  and  161  may be driven independently from each other. For example, two motors may be provided to drive the shafts  151  and  161 , independently.  
         [0114]     The development cartridge  40  can be replaced by a new one when the developing roller  41  is found degraded excessively. This improves maintenance efficiency. Similarly, the photosensitive-drum cartridge  20  can be replaced by a new one if the photosensitive drum  21  is found degraded. This also improves maintenance efficiency.  
         [0115]     As described above, when mounting the toner cartridge  60  in the toner-cartridge holder  42  of the development cartridge  40 , the toner cartridge  60  is first mounted in the toner-cartridge holder  42 . As a result, the inner and outer cylinders  63  and  64  of the toner cartridge  60  are located coaxially with the cylindrical toner-cartridge holder  42 , and the projection  64   a  of the outer cylinder  64  is fitted in the elongated groove  42   b . At this time, the gear  61   b  is brought into engagement with the gear  53 . Then, the inner cylinder  63  is rotated about its central axis relative to the outer cylinder  64  so that the toner cartridge  60  is completely mounted in the development cartridge  40 . In other words, the inner cylinder  63  is rotated about its central axis relative to the outer cylinder  64  until the engagement members  63   c  are brought into engagement with the rails  42   c  and the inside of the inner cylinder  63  is brought into fluid communication with the inside of the developing section  40   a  of the development cartridge  40 . After the toner cartridge  60  is completely mounted in the development cartridge  40 , the drive force is inputted from the drive shaft  161  to the drive shaft  61   a . As a result, the agitator  6 i rotates, and the drive force is properly transmitted from the rotational shaft  61  of the agitator  60  via the gear  61   b  to the auger rollers  43   a  and  44 . Because the rotational axis of the gear  61   b  and the rotational axis of the agitator  61  (rotational shaft  61   a ) coincide with each other and extend along the central axis of the inner cylinder  63 , it is possible to easily mount the toner cartridge  60  to the development cartridge  40 . It is ensured that the drive force is properly transmitted from the agitator  60  to the auger rollers  43  and  44 .  
         [0000]     &lt;Modification&gt; 
         [0116]     The system for driving the development cartridge  40  and toner cartridge  60  may be configured as shown in  FIG. 16 . In this case, the main body of the laser printer  1  may have the drive shaft  151  only. The drive shaft  161  may be omitted from the main body of the laser printer  1 .  
         [0117]     The system of this modification is the same as the above-described system except for the following points:  
         [0118]     A gear  57  is provided on the inner surface of the left-side wall of the toner-cartridge holder  42 . The left-side tip end of the rotational shaft  61   a  has no configuration that constitutes the above-described drive coupling. Instead, a gear  61   d  is integrally formed with the rotational shaft  61   a  at the left-side tip end thereof. The gear  61   d  is located on the outer side of the left-side end wall of the inner cylinder  63 . The gear  57  is in engagement with the gear  51   b . The gear  61   d  is in engagement with the gear  57  when the toner cartridge  60  is mounted in the development cartridge  40 .  
         [0119]     It is noted that the development cartridge  40  and toner cartridge  60  according to this modification have the same configuration as that described above with reference to  FIG. 13 .  
         [0120]     In this modification, when a drive force is transmitted from the drive shaft  151  on the main body of the laser printer  1  to the drive shaft  51 , the drive force is transmitted to the developing roller  41  and the toner-supplying roller  45  via the gears  41   a  and  45   a , respectively. The drive force transmitted to the drive shaft  51  is transmitted also to the gear  57 . The drive force is transmitted from the gear  57  further to the rotational shaft  61   a  via the gear  61   d . As a result, the agitator  61  is driven to rotate. Further, the drive force is transmitted from the gear  61   b  to both the upper auger roller  43  and the lower auger roller  44 , through the gears  53 ,  43   a  and  44   a . The upper auger roller  43  and the lower auger roller  44  are thereby rotated.  
         [0121]     In this modification, the developing roller  41  and the toner-supplying roller  45 , upper auger roller  43 , lower auger roller  44 , and agitator  61  can be rotated, merely by transmitting the drive force to the drive shaft  51  from the drive shaft  151 . Also in this modification, the gear  61   b  is not engaged with the gear  53  when the toner cartridge  60  is disconnected from the development cartridge  40 . Hence, the drive force is not transmitted to the upper auger roller  4 . 3  or the lower auger roller  44  (see  FIG. 13 ). This modification can therefore achieve the same advantages as described above.  
         [0000]     &lt;Another Modification&gt; 
         [0122]     The system for driving the development cartridge  40  and toner cartridge  60  may be configured as shown in  FIGS. 17A-17D . In this case, the main body of the laser printer  1  may have the drive shaft  161  only. The drive shaft  151  may be omitted from the main body of the laser printer  1 .  
         [0123]     Except for the following points, the system of this modification is the same as the system described above with reference to FIGS.  1 - 15 :  
         [0124]     In this modification, as shown in  FIG. 17A , no drive shaft  51  is provided on the left side of the development cartridge  40 . No gear  41   a  is provided on the left-side end of the rotational shaft  41   b , and no gear  45   a  is provided on the left-side end of the rotational shaft of the toner-supplying roller  45 . As shown in  FIG. 17D , no auger roller  43  or  44  is provided in the development cartridge  40 .  
         [0125]     Instead, as shown in  FIG. 17C , an additional gear  154  is provided on the outer side of the right-side wall of the development cartridge  40 . The gear  53  is in engagement with the additional gear  154 .  
         [0126]     A gear  141  is fixed on the right-side end of the rotational shaft  41   b , and rotates integrally with the developing roller  41 . A gear  145  is fixed on the right-side end of the rotational shaft of the toner-supplying roller  45 , and rotates integrally with the toner-supplying roller  45 . The gears  141  and  145  are in engagement with the additional gear  154 .  
         [0127]     The agitator  61  is rotated when a drive force is transmitted to the rotational shaft  61   a  from the drive shaft  161 . The drive force is transmitted from the gear  61   b  via the gears  53  and  154  to the gears  141  and  145 . As a result, the developing roller  41  and the toner-supplying roller  45  are rotated.  
         [0128]     In this modification, the developing roller  41  and the toner-supplying roller  45 , and agitator  61  can be rotated, merely by transmitting the drive force to the drive shaft  61   a  from the drive shaft  161 . Also in this modification, the gear  61   b  is not engaged with the gear  53  when the toner cartridge  60  is disconnected from the development cartridge  40 . Hence, the drive force is not transmitted to the developing roller  41  or the toner-supplying roller  45 . This modification can ensure that the developing roller  41  and the toner-supplying roller  45  are driven to rotate only when the toner cartridge  60  is mounted in the development cartridge  40 .  
         [0129]     While the invention has been described in detail with reference to the above aspects 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 invention.  
         [0130]     The laser printer  1  can be modified to various image forming apparatuses of electronic photographic type, such as copying apparatuses, facsimile apparatuses and color laser printers. The photosensitive drum  21  may be modified into a photoelectric belt. A non-photosensitive electrostatic latent image bearing body may be provided instead of the photosensitive drum  21 . An intermediate transfer belt may be used to transfer toner images onto a recording medium.  
         [0131]     In the above description, since the photosensitive-drum cartridge  20  and the development cartridge  40  are detachably mounted in the main body of the laser printer  1 , they can be replaced by new ones when necessary. This facilitates easy maintenance of the laser printer  1 . However., the photosensitive-drum cartridge  20  and the development cartridge  40  may be fixedly secured in the main body of the laser printer  1 .  
         [0132]     In the above description, the photosensitive-drum cartridge  20  and the development cartridge  40  can be disconnected from each other. This facilitates easy maintenance of the photosensitive-drum cartridge  20  and the development cartridge  40 . However, the photosensitive-drum cartridge  20  and the development cartridge  40  may be formed integrally with each other into a process cartridge. The photosensitive-drum cartridge  20  and the development cartridge  40  may not be disconnected from each other.