Abstract:
An image forming device includes a process cartridge, a wall section, and a flow restrictor. The process cartridge includes a photosensitive drum, a charger, and a frame. The charger is disposed spaced away from the photosensitive drum for charging the photosensitive drum. The frame is formed with a first opening at a position opposite to the photosensitive drum with respect to the charger. The frame is also formed with a first vent hole for ventilation of a space defined by the frame. The first vent hole is positioned upstream of the first opening and downstream of the image transfer position of the photosensitive drum in the rotational direction of the photosensitive drum. The wall section is positioned in direct confrontation with the first opening. The flow restrictor restricts air flow and is provided between the frame and the wall section.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority from Japanese Patent Application No. 2008-300610 filed Nov. 26, 2008. The entire content of this priority application is incorporated herein by reference. 
       TECHNICAL FIELD 
       [0002]    The present invention relates to an image-forming device provided with a process cartridge having a charger. The invention also relates to the process cartridge detachably mounted in the image forming device. 
       BACKGROUND 
       [0003]    In an electrophotographic type image forming device, a laser beam is irradiated to a charged photosensitive drum to form an electrostatic latent image thereon, and a toner image formed by supplying toner to the electrostatic latent image is transferred on a sheet. 
         [0004]    The image forming device includes a process cartridge having a charger and a frame. The charger includes a corona discharge type wire adapted for charging the photosensitive drum. The frame is formed with an opening located at a position opposed to the photosensitive drum with respect to the charger. An ion is generated on the wire by applying a voltage thereto, and ion wind moves toward and impinges on the photosensitive drum, whereupon the photosensitive drum is electrically charged with a polarity. 
       SUMMARY 
       [0005]    However, for charging the photosensitive drum, the ion wind generated in the charger should be controlled. If the ion wind is impinged on a contaminated area of the photosensitive drum, the ion wind may be contaminated with dust or foreign materials, and such contaminated ion flow may return to the charger. As a result, dust or foreign materials may be deposited on the wire, leading to degradation of the charging efficiency of the charger. 
         [0006]    In view of the foregoing, it is an object of the present invention to provide an image forming device and process cartridge capable of restricting the deposition of the dust and foreign materials on the charger and maintaining the efficiency of the charger. 
         [0007]    In order to attain the above and other objects, the invention provides an image forming device including a process cartridge, a wall section, and a flow restrictor. The process cartridge includes a photosensitive drum, a charger, and a frame. The photosensitive drum is rotatable about an axis in a rotational direction and defines an image transfer position where a toner is transferred to an electrostatic latent image area formed on the photosensitive drum. The charger is disposed spaced away from the photosensitive drum for charging the photosensitive drum. The frame is formed with a first opening at a position opposite to the photosensitive drum with respect to the charger. The frame is also formed with a first vent hole for ventilation of a space defined by the frame. The first vent hole is positioned upstream of the first opening and downstream of the image transfer position of the photosensitive drum in the rotational direction of the photosensitive drum. The wall section is positioned in direct confrontation with the first opening. The flow restrictor restricts air flow and provided between the frame and the wall section and between the first opening and the first vent hole. 
         [0008]    According to another aspect, the present invention provides a process cartridge installed on an install portion of an image forming device. The install portion includes a wall section. The process cartridge includes a photosensitive drum, a charger, a frame, and a flow restrictor. The photosensitive drum is rotatable about an axis in a rotational direction and defines an image transfer position where a toner is transferred to an electrostatic latent image area formed on the photosensitive drum. The charger is disposed spaced away from the photosensitive drum for charging the photosensitive drum. The frame is formed with a first opening at a position opposite to the photosensitive drum with respect to the charger. The first opening is in direct confrontation with the wall section upon installation of the frame into the install portion. The frame is also formed with a first vent hole for ventilation of a space defined by the frame. The first vent hole is positioned upstream of the first opening and downstream of the image transfer position of the photosensitive drum in the rotational direction of the photosensitive drum. The flow restrictor restricts air flow and provided between the frame and the wall section and between the first opening and the first vent hole. 
         [0009]    According to still another aspect, the present invention provides a process cartridge installed on an install portion of an image forming device in a juxtaposed fashion so that mutually neighboring process cartridges are positioned side by side. The process cartridge includes a photosensitive drum, a charger, a frame, and a flow restrictor. The photosensitive drum is rotatable about an axis in a rotational direction and defining an image transfer position where a toner is transferred to an electrostatic latent image area formed on the photosensitive drum. The charger is disposed spaced away from the photosensitive drum for charging the photosensitive drum. The frame is formed with a first opening at a position opposite to the photosensitive drum with respect to the charger. The first opening is in direct confrontation with a neighboring process cartridge upon installation of the frame into the install portion. The frame is also formed with a first vent hole for ventilation of a space defined by the frame. The first vent hole is positioned upstream of the first opening and downstream of the image transfer position of the photosensitive drum in the rotational direction of the photosensitive drum. The flow restrictor restricts air flow flowing between the frame and the neighboring process cartridge. The flow restrictor is positioned between the first opening and the first vent hole. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The particular features and advantages of the invention as well as other objects will become apparent from the following description taken in connection with the accompanying drawings, in which: 
           [0011]      FIG. 1  is a cross-sectional view of an entire configuration of a color printer according to a first embodiment of the present invention; 
           [0012]      FIG. 2  is an enlarged cross-sectional view showing a most upstream process cartridge according to the first embodiment; 
           [0013]      FIG. 3  is a perspective view showing the most upstream process cartridge according to the first embodiment; 
           [0014]      FIG. 4  is an enlarged cross-sectional view showing a process cartridge other than the most upstream process cartridge according to the first embodiment; 
           [0015]      FIG. 5  is an enlarged view illustrating a flow of an ion wind in the first embodiment; 
           [0016]      FIG. 6  is an enlarged cross sectional view showing a process cartridge other than a most upstream process cartridge according to a second embodiment of the present invention; 
           [0017]      FIG. 7  is a perspective view of the process cartridge according to the second embodiment; 
           [0018]      FIG. 8  is an enlarged cross-sectional view illustrating a flow of ion wind around a process cartridge detachably mounted in a color printer according to a third embodiment of the present invention; 
           [0019]      FIG. 9  is an enlarged cross-sectional view showing a process cartridge detachably mounted in a monochromatic printer according to a fourth embodiment of the present invention; 
           [0020]      FIG. 10  is an enlarged cross-sectional view illustrating a flow of ion wind around a process cartridge according to a fifth embodiment of the present invention; 
           [0021]      FIG. 11  is an enlarged cross-sectional view showing a process cartridge detachably mounted in a monochromatic printer according to a sixth embodiment of the present invention; and 
           [0022]      FIG. 12  is an enlarged cross-sectional view showing a process cartridge detachably mounted in a monochromatic printer according to a seventh embodiment of the present invention; 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    Next, an image forming device according to a first embodiment of the present invention will be described while referring to  FIGS. 1 through 5 . The terms “upward”, “downward”, “upper”, “lower”, “above”, “below”, “right”, “left”, “front”, “rear” and the like will be used throughout the description assuming that the image forming device is disposed in an orientation in which it is intended to be used. 
         [0024]    As shown in  FIG. 1 , the image forming device  1  includes a main frame  10 . In the main frame  10 , a sheet feeding unit  20  for supplying a sheet P, an image forming unit  30  for forming an image on the supplied sheet P, and a discharge unit  90  for discharging the sheet P bearing an image are provided. 
         [0025]    The main frame  10  has an upper position at which an upper cover  12  can be opened and closed. The upper cover  12  is pivotally movable in an upper/lower direction about a hinge (not shown) provided rearward thereof. The upper cover  12  has an upper surface functioning as a sheet tray  13 , and the upper cover  12  has a lower surface provided with a plurality of support frames  14  each supporting an upper part of an LED (Light Emitting Diode) array  40  described later. 
         [0026]    The sheet feeding unit  20  is provided at a lower position of the main frame  10 . The sheet feeding unit  20  includes a sheet tray  21  that is detachably mounted in the main frame  10  and a sheet supplying mechanism  22  for transmitting the sheet P from the sheet tray  21  to the image forming unit  30 . 
         [0027]    The image forming unit  30  includes four LED arrays  40 , four process cartridges  50 , a transfer unit  70 , and a fixing unit  80 . The LED array  40  includes a plurality of LEDs arrayed in line in a lateral direction (widthwise direction of the sheet P). 
         [0028]    Each of the LEDs in the LED array  40  is selectively turning on and off according to an image data. The LED array  40  has a light emitting end in confrontation with the photosensitive drum  53  and another end opposite to the light emitting end. The main frame  14  supports the other end of the LED array  40 . 
         [0029]    The process cartridges  50  are juxtaposed in front-to-rear direction between the upper cover  12  and the sheet feeding unit  20 . The process cartridges  50  respectively accommodate four toner colors black, cyan, magenta, and yellow. The process cartridges  50  are detachably mounted in the main frame  10  and are accessible through an upper opening upon opening the upper cover  12 . 
         [0030]    The configuration of a most upstream side process cartridge  50 A is different from that of a remaining three process cartridges  50 B,  50 B′, and  50 B″. The general configuration of the process cartridge  50  will be described below with reference to the most upstream side process cartridge  50 A and the detailed configuration thereof will be described later. 
         [0031]    The process cartridge  50  includes a drum unit  51  and a developer cartridge  61  detachably mounted in the drum unit  51  as shown in  FIG. 2 . The drum unit  51  includes a drum frame  52 , a photosensitive drum  53  rotatable in a counterclockwise direction in  FIG. 2 , a charging wire  54  and a grid  58  which are separated from the photosensitive drum  53 . The drum frame  52  is formed with an opening  55  for exposing the photosensitive drum  53  outwardly upon mounting the developer cartridge  61 . The photosensitive drum  53  is exposed to light emitted from the LED array  40  based on the image data, thereby forming an electrostatic latent image thereon. The electrostatic latent image is developed into a toner image and the toner image is transferred to the sheet P at the transfer position C. 
         [0032]    The opening  55  is formed at a position downstream of the charging wire  54  and upstream of the transfer position C in the rotating direction of the photosensitive drum  53 . The LED array  40  is inserted into the opening  55 . 
         [0033]    The developer cartridge  61  includes a developing frame  62 , a developing roller  63  and a toner supply roller  64  which are rotatably supported by the developing frame  62 , a thickness-regulating blade  65  in sliding contact with the developing roller  63 , and a toner housing  66  for accommodating toner T therein. 
         [0034]    As shown in  FIG. 1 , the transfer unit  70  includes a drive roller  71 , a follower roller  72 , an endless transfer belt  73 , and a transfer rollers  74 . The drive roller  71  and the follower roller  72  are separated in a front-to-rear direction and extend in parallel with each other. The endless transfer belt  73  is mounted under tension between the drive roller  71  and the follower roller  72 . The endless transfer belt  73  has an outer side surface in contact with the photosensitive drum  53  at the transfer position C. The four transfer rollers  74  are disposed at an inner side of the transfer belt  73  to nip the transfer belt  73  in cooperation with the photosensitive drum  53 . A transfer bias is applied to the transfer roller  74  in a constant current control when transferring. 
         [0035]    The fixing unit  80  includes a heat roller  81  and a pressure roller  82  disposed opposite to the heat roller  81  and pressing the heat roller  81 . 
         [0036]    In the image forming unit  30 , the surface of the photosensitive drum  53  is uniformly charged by the charging wire  54  with positive polarity, and then is exposed to light emitted from the LED array  40 . As a result, the potential of the exposed portion is decreased to form the electrostatic latent image based on the image data on each photosensitive drum  53 . 
         [0037]    A corona discharge is generated between the charging wire  54  and the photosensitive drum  53  by applying the voltage to the charging wire  54  while charging the photosensitive drum  53 . The charging wire  54  generates an ion during the generation of the corona discharge. A potential difference between the charging wire  54  and the surface of the photosensitive drum  53  causes the ion to move toward the surface of the photosensitive drum  53 . The ion moves from the charging wire  54  to the surface of the photosensitive drum  53  so that an ion wind toward the photosensitive drum  53  is generated. 
         [0038]    The toner supply roller  64  is adapted to supply the toner T accommodated in the toner housing  66  to the developing roller  63 . As the developing roller  63  continues to rotate, the toner T supplied onto the surface of the developing roller  63  passes between the developing roller  63  and the thickness-regulating blade  65 , at which time the toner is smoothed so that a thin layer of uniform thickness is carried on the developing roller  63 . The toner T carried on the developing roller  63  is positively charged by the friction generated between the toner supply roller  64  and the developing roller  63  or the developing roller  63  and the thickness-regulating blade  65 . 
         [0039]    The toner T carried on the developing roller  63  is supplied to the electrostatic latent image formed on the photosensitive drum  53 . In this way, the toner T is selectively carried on the photosensitive drum  53 , developing the electrostatic latent image into a visible toner image, and forming the toner image (inversed image) thereon. 
         [0040]    By passing through the sheet P supplied on the endless transfer belt  73  between the each photosensitive drum  53  and the transfer roller  74 , the toner images formed on each photosensitive drum  53  are superimposed on the sheet P. When the sheet P passes between the heat roller  81  and the pressure roller  82 , the toner image is thermally fixed on the sheet P. 
         [0041]    The discharge unit  90  includes a plurality of discharge roller  92 . The sheet P forming the toner image thereon is discharged by the discharge roller  92  onto the sheet discharge tray  13 . 
         [0042]    Next, a detailed configuration of the process cartridges  50 A,  50 B will be described below with reference to the  FIGS. 2 through 4 . As shown in  FIG. 2 , the most upstream side process cartridge  50 A further includes a cleaning roller  56 , a collection roller  57 , a remover  57 B, and the grid  58 . The cleaning roller  56  is adapted to absorb the toner T and foreign materials on the photosensitive drum  53  and is disposed at a position contacting the photosensitive drum  53 . The foreign materials include a paper dust and other dust. Specifically, the cleaning roller  56  is disposed at a position upstream of the charging wire  54  and downstream of the transfer position C in the rotating direction of the photosensitive drum  53 . 
         [0043]    The collection roller  57  is adapted to absorb the foreign materials and the toner on the cleaning roller  56  and disposed at a position contacting the cleaning roller  56 . The remover  57 B formed of a sponge is provided in contact with the collection roller  57  for removing the foreign materials absorbed by the collection roller  57 . 
         [0044]    The grid  58  is adapted to commutate a potential of the ion moving from the charging wire  54  to the surface of the photosensitive drum  53 . The grid  58  has a box shape with the upper side open and has a bottom wall in which a plurality of holes are formed. 
         [0045]    The drum frame  52  includes a partitioning wall  52 A and a pair of support walls  52 B. The partitioning wall  52 A is adapted to separate a space ambient to the charging wire  54  from a space ambient to the cleaning roller  56  and collection roller  57 . The pair of support walls  52 B are adapted for supporting side walls of the grid  58 . 
         [0046]    The drum frame  52  is formed with a charging opening  52 C at a position opposite to the photosensitive drum  53  with respect to the charging wire  54 . Specifically, the charging opening  52 C is formed between the pair of support walls  52 B. The process cartridge  50 B neighboring the most upstream side process cartridge  50 A has a drum frame  52 ′ disposed in confrontation with the charging opening  52 C of the most upstream side process cartridge  50 A. 
         [0047]    As shown in  FIG. 3 , the charging opening  52 C is configured of a slit shape extending in a right-to-left direction. The charging opening  52 C has a left side portion on which a cleaner CL is provided. The cleaner CL is movable in right-to-left direction while contacting the charging wire  54 . 
         [0048]    The drum frame  52  is formed with a plurality of second openings  52 D formed on both sides of the charging opening  52 C in order to introduce an air from outside of the drum frame  52  into a region ambient to the charging wire  54  and the grid  58  as shown in  FIG. 2 . The plurality of second openings  52 D are arranged in right-to-left direction as shown in  FIG. 3 . With this configuration, ribs can be formed between the neighboring second openings  52 D in comparison with a configuration where an elongated single second opening  52 D extending in the lateral direction is formed like the charging opening  52 C. Thus, the strength of a portion supporting the cleaner CL can be improved. 
         [0049]    As shown in  FIG. 2 , the drum frame  52  is formed with a first opening  52 E formed at a position upstream of the charging opening  52 C and downstream of the transfer position C in the rotating direction of the photosensitive drum  53 . The first opening  52 E is adapted for ventilation of the drum frame  52 . Specifically, the first opening  52 E is formed between the support wall  52 B and the partitioning wall  52 A. 
         [0050]    The first opening  52 E is a through-hole with which a film F is provided. The film F having elasticity is disposed at a position between the frame  52  of the most upstream side process cartridge  50 A and the neighboring frame  52 ′ of the process cartridge  50 B so as to regulate air flowing therebetween. 
         [0051]    The film F protrudes upward and is fixed on the charging opening  52 C side of the first opening  52 E. The top edge of the film F contacts the developing frame  62 ′ of the process cartridge  50 B juxtaposed with the most upstream side process cartridge  50 A. 
         [0052]    The film F is formed of the elastic material. This configuration can prevent vibration occurring at the process cartridge  50 A provided with the film F from being transmitted to the process cartridge  50 B contacting the film F. Thus, degradation of the image quality can be avoided. 
         [0053]    The configuration of the process cartridge  50 B is the same as that of the most upstream side process cartridge  50 A except that the process cartridge  50 B does not have the collection roller  57  provided in the most upstream side process cartridge  50 A. Since the foreign materials attached on the sheet P can be sufficiently collected by the collection roller upon passing through the most upstream side process cartridge  50 A. Therefore, foreign materials may not be introduced into the process cartridge  50 B, thereby avoiding necessity of providing the collection roller at the process cartridge  50 B. 
         [0054]    The process cartridge  50 B includes a cleaning roller  56 ′ similar to that of the most upstream side process cartridge  50 A. 
         [0055]    The drum frame  52 ′ of the process cartridge  50 B also includes an upper wall  522 , a lower wall  533  and an end wall  521 . The drum frame  52 ′ is formed with a first opening  52 E′ disposed at a position different from the position of the first opening  52 E of the most upstream side process cartridge  50 A. That is, the first opening  52 E′ is positioned opposite to the photosensitive drum  53  with respect to the rotation center of the cleaning roller  56 ′. 
         [0056]    The upper wall  522  is in confrontation with a developing frame  62 ″ of the process cartridge  50 B. The end wall  521  is elongated in a direction perpendicular to the upper wall  522 . The first opening  52 E′ is formed on the end wall  521  of the process cartridge  50 B. The first opening  52 E′ is preferably provided by a plurality of through-holes arranged in right-to-left direction to improve the strength of the drum frame  52 ′. 
         [0057]    The first opening  52 E′ is formed on the end wall  521  so that the charging opening  52 C, the second opening  52 D, the grid  58 , the support wall  52 B, the upper wall  522 , and the cleaning roller  56 ′ form a path through which the air flows from the charging opening  52 C to the first opening  52 E′. 
         [0058]    The elastic film F is provided between the drum frame  52 ′ (upper wall  522 ) of the process cartridge  50 B and the drum frame  52 ′ (lower wall  533 ) of the process cartridge  50 B′ neighboring to the process cartridge  50 B. The film F is fixed on a position in which the upper wall  522  is in contact with the support wall  52 B and contacts the neighboring process cartridge  50 B′. 
         [0059]    The ion wind upon charging the photosensitive drum  53  by the charging wire  54  will be described while referring to the  FIG. 5 . An air in each process cartridge  50  is flowed by an electric fan (not shown) and the ion wind from the opening  55  side to the charging wire  54  side. 
         [0060]    As shown in  FIG. 5 , when applying an electric bias to the charging wire  54 , the air flowing from the opening  55  to the charging wire  54  is interrupted by the film F and introduced into the region ambient to the charging wire  54  through the charging opening  52 C and the second opening  52 D. The ion wind can flow from the charging wire  54  to the photosensitive drum  53 , thereby sufficiently charging the photosensitive drum  53 . 
         [0061]    The ion wind impinged on the photosensitive drum  53  is discharged through the first opening  52 E and  52 E′. The film F prevents the ion wind from returning back to the charging opening  52 C. 
         [0062]    With this configuration, if the ion wind impinged on the photosensitive drum  53  is polluted by the toner T or foreign materials deposited on the photosensitive drum  53 , the film F prevents the polluted ion wind from returning back to the charging opening  52 C. Therefore, the charging wire  54  can maintain charging performance because deposition of the toner T or foreign materials onto the charging wire  54  can be prevented. 
         [0063]    By forming the second opening  52 D ambient to the charging opening  52 C, a large amount of air can be introduced into the region ambient to the charging wire  54 . This configuration can prompt the generation of ion wind, thereby charging the photosensitive drum  53  sufficiently. 
         [0064]    The first opening  52 E is formed between the charging opening  52 C and the partitioning wall  52 A in the most upstream side process cartridge  50 A. With this configuration, the ion wind cannot blow up the foreign materials and paper dust collected on the collection roller  57 , thereby improving the quality of the image formed on the sheet P. 
         [0065]    Since the first opening  52 E′ formed on the process cartridge  50 B is positioned opposite to the photosensitive drum  53  with respect to the cleaning roller  56 ′, the ion wind can flow smoothly rather than the configuration where the ion wind flows along U shape path in case of the most upstream side process cartridge  50 A. The collection roller  57  in the most upstream side process cartridge  50 A has already collected the paper dust or foreign materials. Thus, the cleaning roller  56 ′ in the process cartridge  50 B catches only the toner T by the electrical force or the intermolecular force (van de Waals force). Thus, the ion wind cannot blow up the toner T on the cleaning roller  56 ′. 
         [0066]    The LED array  40  is disposed at a position downstream of the charging opening  52 C in the rotating direction of the photosensitive drum  53 , i.e., upstream side of the ion wind flow generated around the charging wire  54 . Thus, an end face of the LED array  40  can be protected against the toner T and foreign materials carried by the ion wind. 
         [0067]    The first opening  52 E′ of the process cartridge  50 B is formed not on the upper wall  522  facing to the process cartridge  50 B′ but on the end wall  521 . Thus, returning the ion wind to the charging opening  52 C can be avoided since the ion wind discharged through the first opening  52 E′ does not go through a path between the process cartridge  50 B′ and the upper wall  522 . 
         [0068]    Next, a process cartridge according to a second embodiment of the present invention will be described below with reference to  FIGS. 6 and 7 , wherein like parts and components are designated by the same reference numbers as those shown in  FIGS. 1-5 . 
         [0069]    In the second embodiment, the drum frame  52  is formed with a first opening  52 E″ positioned neighboring to the upper wall  522 . The first opening  52 E″ is positioned at the charging wire  54  side rather than the cleaning roller  56 ′ side in a direction leading from a center of the photosensitive drum  53  to the charging wire  54 . In other words, the first opening  52 E″ is positioned farther from the photosensitive drum  53  than the cleaning member  56 ′ from the photosensitive drum  53  and is exceeding over the charging wire  54  as viewed from the photosensitive drum  53  in an opposing direction between the photosensitive drum  53  and the charging wire  54 . With this configuration, the ion wind can linearly flow smoothly since the ion wind flows linearly after passing through the support wall  52 B and is subsequently discharged via the first opening  52 E″. 
         [0070]    Next, a third embodiment of the present invention will be described below referring to  FIG. 8 . The third embodiment is almost the same as the process cartridge  50  of the first embodiment. 
         [0071]    In the third embodiment, the process cartridge  50 B includes a sponge S instead of the film F of the first embodiment. The sponge S having elasticity is mounted on the developing frame  62  of the process cartridge  50 B. 
         [0072]    The drum frame  52  has an upper surface F 1  positioned between the charging opening  52 C of the most upstream side process cartridge  50 A and the first opening  52 E thereof. The developing frame  62  of the process cartridge  50 B has a lower surface F 2  positioned at a bottom portion of the process cartridge  50 B and in confrontation with the upper surface F 1 . The sponge S is disposed at the lower surface F 2  and a free end of the sponge S contacts the upper surface F 1 . With this configuration, since the film F need not be provided on the most upstream side process cartridge  50 A, the production process of the most upstream side process cartridge  50 A where the construction is different from that of the process cartridges  50 B,  50 B′,  50 B″ can be reduced, and manufacturing cost can be saved. 
         [0073]    In the process cartridge  50  according to the third embodiment, the drum frame  52 ,  52 ′ includes a first support member  524  and a second support member  525 . 
         [0074]    The first support member  524  includes an end part which protrudes outwardly at a position higher than the free end of the sponge S. With this configuration, when the process cartridge  50  is detached from the main frame  10  and disposed on a board (not shown), the first support member  524  and the second support member  525  contacts the board and supports the process cartridge  50 , thereby avoiding the deformation of the sponge S by the weight of the process cartridge  50 . 
         [0075]    Next, a fourth embodiment of the present invention will be described below referring to  FIG. 9 . The fourth embodiment is almost the same as the process cartridge  50  of the first embodiment. 
         [0076]    In the fourth embodiment, the image forming device  1  is a monochromatic printer having a single process cartridge  50 A. The monochromatic image forming device  1  includes a main frame  100  provided with a sponge S as shown in  FIG. 9 . With this configuration, since the sponge S is provided not on the process cartridge  50  but on the main frame  100 , erroneous removal of the sponge S from the main frame  100  can be avoided. 
         [0077]    Next, a fifth embodiment of the present invention will be described below referring to  FIG. 10 . The fifth embodiment is almost the same as the process cartridge  50  of the first embodiment. 
         [0078]    In the fifth embodiment, each of the upper surface F 1  and the lower surface F 2  is provided with a sponge S. Each of the sponges S has a free end that contacts each other. With this configuration, the air can be surely interrupted since the free end portions of the easily deformable sponges S are in contact with each other. 
         [0079]    Next, a sixth embodiment of the present invention will be described below referring to  FIG. 11 . The sixth embodiment is almost the same as the process cartridge  50  of the first embodiment. 
         [0080]    In the sixth embodiment, the image forming device  1  is a monochromatic printer having a single process cartridge  50 A similarly to the fourth embodiment. The process cartridge  50  is provided with a film F having a top end which is in contact with a main frame  100  as shown in  FIG. 11 . 
         [0081]    Next, a seventh embodiment of the present invention will be described below referring to  FIG. 12 . The seventh embodiment is almost the same as the process cartridge  50  of the second embodiment. 
         [0082]    In the seventh embodiment, the image forming device  1  is a monochromatic printer having a single process cartridge  50 A similarly to the sixth embodiment. The process cartridge  50  is provided with a film F having a top end which is in contact with a main frame  100  as shown in  FIG. 12 . The drum frame  52  is formed with a first opening  52 E″ similarly to the second embodiment. 
         [0083]    While the invention has been described in detail with reference to specific embodiments thereof, if would be apparent to those skilled in the art that many modifications and variations may be made therein without departing from the spirit of the invention. 
         [0084]    In the above-described embodiments, an interrupting member such as the film F and sponge S having elasticity or flexibility is provided on the process cartridge to interrupt an air flow between the process cartridge and the drum frame. However a rigid or non-deformable member is also available as the interrupting member such as a rib provided integrally with the drum frame or the developing frame. A minute clearance can be formed between the free end of interrupting member and the opposing process cartridge of the main frame. 
         [0085]    In the above-described embodiments, the deformable interrupting member is configured to contact the neighboring developing frame. However, the interrupting member can be in contact with the neighboring drum frame. 
         [0086]    In the above-described embodiments, the photosensitive drum  53  is employed as a photosensitive body. However, a belt shaped photosensitive member is also available. 
         [0087]    Further, in the above-described embodiments, the charging wire  54  having a liner shape and the grid  58  are employed as a charger. However, a charger having a saw-edged shape can be employed instead of the charging wire  54 . 
         [0088]    Further, in the above-described embodiments, the scorotron type including the charging wire  54  and the grid  58  charging is employed. However, a corotron type charger eliminating the grid  58  is also available. 
         [0089]    Further, in the above-described embodiments, rollers are used as the cleaning roller  56  and the collection roller  57 . However, brushes are also available as the cleaning member and the collection member. 
         [0090]    Further, in the above-described embodiments, the process cartridge  50  is disposed in an orientation that the end wall  521  faces obliquely downward and rearward, and the upper wall  522  faces obliquely upward and rearward. However, any posture of the process cartridge  50  is available. 
         [0091]    Further, in the above-described embodiments, the LED array  40  having a plurality of LEDs arrayed in a single line in a right-to-left direction is employed as the exposure member that functions to expose the photosensitive body. However, a plurality of LED arrays each having a plurality of LEDs arrayed in a right-to-left direction can be arrayed in the front-to-rear direction. Further, another type of exposure unit is conceivable. The another type includes a plurality of blinking units each including a single light emitting element such as an LED and fluorescent lamp, and an optical shutter such as liquid crystal and PLTZ elements arrayed in the right-to-left direction at the position outside of the light emitting element. Furthermore, EL (electro luminescence) element and fluorescence unit are also available as the light source instead of LED.