Abstract:
An image forming apparatus is provided which includes a rotating image carrier including a central portion and tip portions, and a rotating developing element for contacting the rotating image carrier and applying a developer to a latent image, wherein an axial direction is parallel to an axial direction of the rotating image carrier, and the element includes tip portions at ends in the axial direction. Also, the apparatus includes a member for removing dust from the central portion of the rotating image carrier, a width of the member being less than a width of the rotating developing element and a width of the rotating image carrier in the axial direction of the rotating image carrier, and a dust collector for collecting dust removed by the member, and having a width greater than the width of the rotating developing element in the axial direction of the rotating image carrier.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application claims priority from Japanese Patent Application No. 2005-241211, filed on Aug. 23, 2005, the entire subject matter of which is incorporated herein by reference. 
   FIELD 
   Aspects of the present invention relate to an image forming apparatus that forms an image by developing a latent electrostatic image formed on an image carrier. 
   BACKGROUND 
   Conventionally, an image forming apparatus forms an image by the development of an electrostatic latent image on a photosensitive drum. 
   This type of imaging apparatus is equipped with a fully detachable process unit for easy supply of toner. This process unit includes a photosensitive agent cartridge housed with a peripheral mechanism surrounding a photosensitive drum (image carrier), a toner tank that stores toner, and a development roller that carries and supplies toner to the photosensitive drum, etc. In essence, it is an image developing cartridge including a mechanism for development using toner. The image developing cartridge is fully detachable from the photosensitive agent cartridge. 
   As shown in  FIG. 9 , the cartridge casing  200  of the photosensitive cartridge contains a photosensitive material drum  201 , a transfer printing roller  202  that transfers printing of a visible image (toner image) developed by the toner from an electrostatic latent image on the photosensitive drum  201  to paper P 1 , a conductive brush  203 , and a lower film  204  which is placed so that it blocks a gap between the photosensitive drum  201 , and the cartridge casing  200  so that it is able to retain the paper dust removed from the surface of the photosensitive drum  201  by the conductive brush  203  in the cartridge casing  200 . 
   An electrode bias is applied on the conductive brush  203  to remove paper dust from the photosensitive drum  201  to prevent current leakage between the photosensitive drum  201  and the conductive brush  203 . The conductive brush  203  is installed in a manner in which it is not in contact with both ends of drum in the axial direction of the photosensitive drum  201 . 
   In other words, the tips of the conductive brush  203  along the axial direction of drum are situated toward the central part of the drum in the axial direction of drum away from the ends of the photosensitive drum  201 . To be more precise, the conductive brush  203  is narrower in the lengthwise direction than the photosensitive drum  201  is in the axial direction. 
   As described above, the lower film  204  is located under the conductive brush  203  and is installed so as to retain the paper dust removed by the conductive brush  203  from the drum  201 . In other words, the edge of the lower film  204  in the axial direction of the drum  201  is installed so that the edge extends below the axial direction of drum in relation to the edges of the conductive brush  203  in the axial direction of the drum. That is, the length of the lower film  204  in the axial direction of the drum is slightly longer than the length of the conductive brush  203  in the axial direction of the drum  201 . 
   As described above, in both ends of the drum  201  there are segments that are not in contact with the conductive brush  203  (hereinafter referred to as a non-cleanable area). Hence, the paper dust on the non-contact segments (hereinafter “non-cleanable area”) cannot be removed from the drum  201  by the conductive brush  203 . 
   In other words, the paper dust adhering to the non-cleanable area is the part where the periphery of the photosensitive drum  201  is in contact with the periphery of a development roller (not shown). As a result, the dust may be transferred from the periphery of the photosensitive drum  201  to the periphery of the development roller. The paper dust transferred to the periphery of the development roller will eventually accumulate in 1) the gap between the development roller and a side seal configured to prevent toner leakage from the end of the development roller or 2) in a toner tank which supplies toner to the development roller. 
   When the paper dust accumulates in the gap between the side seal and the development roller, the paper dust attracts the toner which can cause a toner leak. Additionally, when the paper dust accumulates in the toner tank, the electrostatic charge capacity of the toner in the toner tank is decreased, which can result in uneven toner application to the drum  201 . 
   SUMMARY 
   Illustrative aspects of the invention relate to preventing the adhesion of dust to a non-cleanable area of the photosensitive drum. 
   According to at least some aspects of the invention, an image forming apparatus is provided including a rotating image carrier for carrying a latent image, the image carrier including a central portion and tip portions; and a rotating developing element for contacting the rotating image carrier and applying a developer to the latent image to form a visible image on the rotating image carrier, an axial direction of the rotating developing element being parallel to an axial direction of the rotating image carrier, the rotating developing element including tip portions at ends in the axial direction of the rotating image carrier. The apparatus further may include a member for removing dust from the central portion of the rotating image carrier, a width of the member in the axial direction of the rotating image carrier being less than a width of the rotating developing element and a width of the rotating image carrier in the axial direction of the rotating image carrier; and a dust collector for collecting dust removed from the rotating image carrier by the member, the dust collector having a width greater than the width of the rotating developing element in the axial direction of the rotating image carrier. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  is a simplified cross-sectional view of a laser printer according to illustrative aspects of the invention. 
       FIG. 2A  is a top view of the process unit of  FIG. 1 ; 
       FIG. 2B  is a cross-sectional view along the A-A axis of  FIG. 2A . 
       FIG. 3  is a perspective view of the core portion of the photosensitive cartridge of  FIG. 1  according to an illustrative aspect of the invention. 
       FIG. 4  illustrates the relationships and locations of the major parts of the photosensitive cartridge in  FIG. 3 . 
       FIG. 5  is a perspective view of the core of the photosensitive cartridge of  FIG. 1  according to another illustrative aspect of the invention. 
       FIG. 6  illustrates the relationship and locations of the major parts of the photosensitive cartridge in  FIG. 5 . 
       FIG. 7  is a perspective view of the core of the photosensitive cartridge of  FIG. 1  according to another illustrative aspect of the invention. 
       FIG. 8  illustrates the relationships and locations of the major parts of the photosensitive cartridge in  FIG. 7 . 
       FIG. 9  illustrates selected components of a conventional photosensitive cartridge. 
   

   DETAILED DESCRIPTION 
   Illustrative aspects of the present invention are described with reference to the drawings. 
     FIG. 1  is a cross-sectional view of the laser printer  1 . 
   The casing  2  includes a top surface  3 , a bottom surface and four sides including the front side portion  2   a  and the back side portion  2   b . The top surface  3  slopes downward toward the back side portion  2   b , the sloping portion of the top surface  3  forming a recording medium ejection tray  71 . Immediately above the bottom surface of the casing  2 , there is a cassette  11 , which stores a stack of recording medium (e.g., paper) and can be fully removed through the front portion  2   a  of the casing  2 . On the front portion  2   a , there is a recording medium feed part  19  through which the recording medium can be inserted manually and a front cover  4  which can be opened and closed. The back side portion  2   b  includes a rear cover  5  which can be opened and closed. 
   The laser printer  1  further includes a recording medium feed part  10  (the path of the recording medium is indicated by solid imaginary line KP, followed by a broken imaginary line P including the broken imaginary line HP) for supplying the recording medium; a process unit  25  which can form a visible image on the recording medium; a fixation unit  60  which fixes the formed image on the recording medium; and a recording medium ejection part  70  in which the recording medium that has passed the fixation unit  60  is ejected. 
   The feed part  10  includes a feed cassette  11 , and the feed rollers  14 ,  15 , and feed pad  16  located at the front side of the recording medium in the feed cassette  11 . In the feed part  10 , a feed path KP begins in which the recording medium fed from the feed cassette  11  can be fed to the portion under the process unit  25  to form the recording medium transfer path. Below the process unit  25  is a resist roller pair  18  straddling the feed path KP. The recording medium may enter the feed path KP from the paper feed cassette  11 , or by way of a feed part  19  through which the recording medium may be manually inserted. In each of the feeding methods, the recording medium is stopped once at the resist roller pair  18  then fed to the process unit  25  in synch with the image formation controlled by the process unit  25 . 
   The feed cassette  11  is located under the process unit  25  and the fixation unit  60 . The feed cassette  11  is also equipped with a pressing plate  12  and spring  13 . The pressing plate  12  keeps the recording medium in a stack and pivots at the edge far from the feed roller  14 , etc. and the portion of the plate  12  near the roller  14  can be moved up and down. In addition, the spring  13  presses the backside of the pressing plate  12  near the roller  14 , etc. so that the plate  12  can be moved up and down. Hence, the pressing plate  12  moves downward against the force of the spring  13  when the recording medium volume is increased. 
   The feed roller  15  and feed pad  16  are installed opposite to each other. The feed pad  16  presses on the feed roller  15  by the spring  17  on the backside of the feed pad  16 . The top sheet of the stack of recording medium on the pressing plate  12  is pressed to contact the feed roller  14  by the spring  13  located on the backside of the pressing plate  12 . When a printing operation is started the feed roller  14  feeds the top sheet of the recording medium (e.g., paper) along the feed path KP to the feed roller  15 . The feed roller  15  and feed pad  16  grab the recording medium with the rotation of the feed roller  15 . As this process continues for additional sheets of the recording medium, the recording medium is fed sheet by sheet towards the feed path KP. 
   The recording medium fed from the feed cassette  11  or from the manual feed part  19  is sent to the resist roller pair  18  located above the feed roller  14 , etc. The resist roller pair  18  aligns the recording medium and then feeds it to the process unit  25 . 
   The scanning unit  50  located above the process unit  25  includes a laser source (not shown in the figure), a polygon mirror  51  driven by a high-speed motor, first scanning lens (an fθ lens)  52 , second scanning lens (a cylindrical lens)  53 , and reflecting mirrors  54  and  55 . 
   The light beam modulated from the image information emitted from the laser source is passed and reflected in sequence through the polygon mirror  51 , first scanning lens  52 , reflecting mirror  54 , second scanning lens  53 , and reflecting mirror  55 , as shown with a broken line, then subjected to an exposure-scanning process on the surface of a photosensitive drum  31  in the process unit  25 . 
   The process unit  25  includes a photosensitive cartridge  30  and a development cartridge  40 . The development cartridge  40  can be fully removed in relation to the photosensitive cartridge  30 . Additionally, it includes a development roller  41 , a film thickness controlling blade  42 , a feed roller  43 , a container  44 , etc. 
   The developing agent in the container  44  is stirred by the rotation of an agitator  46  in the rotating direction shown by an arrow, driven by a rotating axis  45 , and is discharged through the discharge outlet  47  of the container  44 . On the side of the discharge outlet  47 , a rotating feed roller  43  is attached. Opposite to the feed roller  43 , a rotating development roller  41  is attached. The feed roller  43  and the development roller  41  are in contact with each other under a compressing force. 
   The development roller  41  includes a metal roller core and a conductive rubber material coating on the roller core, and is rotated in the direction shown with an arrow (counterclockwise direction). Additionally, the development roller  41  is constructed so that a development electrode bias is applied thereto. The film thickness controlling blade  42  is located near by the development roller  41 . The film thickness controlling blade  42  includes an elastic metal sheet spring and an insulating silicone rubber on its edge, and the edge portion is curved in an arc. The blade  42  is positioned by a frame of the development cartridge  40  and the development roller  41 , and the edge of the blade is pressed on the development roller  41  by a spring force exerted by the blade tip. 
   The developing agent discharged through the discharge outlet  47  is fed onto the development roller  41  by the action of the feed roller  43  rotating in counterclockwise direction. At this time, the developing agent is positively charged between the feed roller  43  and the development roller  41 . The developing agent fed onto the development roller  41  enters into the gap between the pressing part of the film thickness regulator blade  42  and the development roller  41  by rotation of the development roller  41 , and the agent is deposited on the development roller  41  as a thin film with a uniform thickness. 
   The photosensitive cartridge  30  is equipped with a photosensitive drum  31 , an electric charger  32 , a transfer printing roller  33 , etc. The photosensitive drum  31  is configured so that it rotates in a direction opposite to the rotating direction of the development roller  41  in relation to the development roller  41  and it can also be rotated in the direction shown with an arrow (clockwise direction) in relation to the photosensitive cartridge  30 . The photosensitive drum  31  is grounded and its surface is covered with a positively charged photosensitive layer made of polycarbonate. 
   The electric charger  32  is located at the upper left of the photosensitive drum  31  at a given distance in the opposite direction. The electric charger  32  is a positively charging Scorotron-type charger including a tungsten charging wire capable of generating corona discharge. The electric charger  32  charges the photosensitive drum  31  surface in a positive, uniform manner. 
   The transfer printing roller  33  is located under the photosensitive drum  31  and situated opposite from the photosensitive drum  31 , and it is installed so that it rotates in the direction of the arrow (counterclockwise direction) in relation to the photosensitive cartridge  30 . The transfer printing roller  33  is composed of a metal roller core which is coated with a conductive rubber material, and during the transfer printing, a transfer printing electrode bias is applied on the roller. A visible image (toner image) on the photosensitive drum  31  surface will be transfer printed onto the recording medium, while the recording medium is passing through the gap between the photosensitive drum  31  and the transfer printing roller  33  (hereinafter referred to as the transfer printing nip part). 
   Then the surface of the photosensitive drum  31  is positively charged in a uniform manner by the electric charger  32  with the rotation of the photosensitive drum  31 , and is exposed by the laser beam from scanning unit  50  to form an electrostatic latent image. 
   Subsequently, with the rotation of the developing roller  41 , the positively charged developing agent on the developing roller  41  is deposited on the electrostatic latent image formed on the surface of the photosensitive drum  31  when the developing roller  41  is in contact with the photosensitive drum  31 . On the positively charged photosensitive surface of drum  31 , the developing agent is deposited on the exposed portion after exposure to a laser beam. The exposed portion has a lower bias after laser beam exposure and the developing agent is selectively deposited on the exposed portion, then a developed image will be formed (transfer printed image). 
   Subsequently, the deposited developing agent on the surface of the developing drum  31  is transfer printed onto the recording medium while it passes through the gap between the photosensitive drum  31  and the transfer printing roller  33  (transfer printing nip part), and with the aid of the transfer printing bias applied to the transfer printing roller  33 . 
     FIG. 2A  is a top view of the process unit  25 .  FIG. 2B  is a cross-sectional view along the A-A axis of  FIG. 2A .  FIG. 3  is a perspective view of the core portion of a photosensitive cartridge  30 , without the charger  32 . 
   As shown in  FIG. 2B , in the casing of the photosensitive cartridge  30 , the recording medium feed part inlet  37  is installed so that a recording medium (e.g., sheet of paper) can be fed into the casing in the upstream end of the recording medium flow direction in relation to the transfer printing nip (the right side in  FIG. 1 ). Additionally, an ejection portion  38  is installed to eject the recording medium out of the casing at the downstream end of the recording medium flow direction in relation to the transfer printing nip part (the left side in  FIG. 1 ). 
   In the configuration, a conductive brush  34  is placed between the ejection portion  38  and the charger  32  (the left side of the photosensitive drum  31  in  FIG. 1 ) opposite to the photosensitive drum  31  so that the tip of the brush is in contact with the surface of the photosensitive drum  31 . An electrode bias is applied to the conductive brush  34 . With contact between the photosensitive drum  31  and the recording medium at the transfer printing nip part, dust can be transferred onto the photosensitive drum  31 . The conductive brush  34  then removes the dust from the photosensitive drum  31 . 
   At an opening of the photosensitive cartridge  30  in the casing is an ejection portion  38 . The top edge  49  of the photosensitive cartridge  30  above the ejection portion  38  protrudes in a horizontal (vertical in  FIG. 2B ) direction. The top edge  49  at both end parts (the direction along the rotational axis of the photosensitive drum  31  (hereinafter referred to as the axial direction of the drum)) is notched out to form the receiving end of a dust collector  39 , where the dust removed by the conductive brush  34  is collected. An edge of the dust collector  39  is proximate to a surface of the photosensitive drum  31  such that a gap exists between the photosensitive drum  31  and the dust collector  39 . A film  35  is provided between the photosensitive drum  31  and the dust collector  39  to fill the gap. The dust collector  39  collects the dust removed by the conductive brush  34  along with a film  35  (refer to  FIG. 2B  and  FIG. 3 ). 
   As shown in  FIG. 3 , a protruding sponge material part  36  is installed on both ends of the tips on the film  35  along the axial direction of the drum  31 . The protrusion extends out away from the film  35 . 
     FIG. 4  shows the relationships and locations of the photosensitive drum  31 , the development roller  41 , the conductive brush  34 , the film  35 , and the sponge material part  36 . They are displayed in the view from the front of the process unit  25  (view from the “x” mark in  FIG. 2B ). 
   The width (brush width) of the conductive brush  34  in the axial direction of the drum is configured so that the entire contact area on the recording medium in contact with the photosensitive drum  31  is subjected to cleaning by the conductive brush  34  when the maximum recording medium size allowed by the laser printer  1  is used. 
   As shown  FIG. 4 , the width (film width) of the film  35  in the drum direction is slightly wider than the brush width of the conductive brush  34 . The width of the film  35  allows the dust removed by the conductive brush  34  to be maintained in the dust collector  35 . 
   The width of the development roller  41  in the axial direction of the drum is less than the width of the photosensitive drum  31  in the axial direction but greater than the width of the conductive brush  34 . Furthermore, in development cartridge  40 , a developing agent supported on development roller  41  is arranged such that, to prevent leakage from both ends of the development cartridge  40  in the axial direction of the development roller  41 , a side seal  48  is placed on each tip of the development roller  41  so that the seal rubs the development roller  41 . 
   The width in the axial direction of the drum of the sponge material part  36  plus the film  35  is less than the photosensitive drum width in the axial direction of the drum but greater than the width of the development roller  41 . 
   As shown in  FIG. 1 , the fixation unit  60  is located above the feed cassette  11  and on the side of the process unit  25 , and is on the downstream end of the recording medium path from the process unit  25 . The fixation unit  60  is equipped with a heater-equipped heating roller  61  and is on a side of the recording medium path opposite a pressure roller  62 . The pressure roller  62  presses on the surface of the heating roller  61 . The heating roller  61  is a cylindrical metal cylinder in which both ends are opened and equipped with a heater, namely, a halogen lamp. The heater provides the heating that is necessary to fix the image on the recording medium. 
   The pressure roller  62  includes an elastomeric surface made of silicone rubber, etc., is covered with a PTFE (polytetrafluoroethylene) film, and is rotated by the action of the heating roller  61  while it is pressed by the heating roller  62 . 
   The visible image, which is a transfer printed, developer image on the recording medium in the process unit  25 , is thermally fixed while the recording medium is passing through the heating roller  61  and pressure roller  62  in the fixation unit  60 . Subsequently, the recording medium is transferred to the recording medium ejection path HP in the paper ejection part  70 . 
   The ejection part  70  includes an ejection tray  71  on the top surface  3 , a recording medium ejection path HP including an inner guide part  72  and an outer guide part  73 , and an ejection roller  74  located above the ejection tray  71  by the ejection outlet. 
   The ejection tray  71  is a flat, substantially rectangular shape and gradually slopes downward from the top surface  3  on the front cover side toward the back cover side. Additionally, the tray progressively slopes upward from the backside edge as it reaches to the front part. The recording medium that has passed through the fixation unit  60  and been transferred into the recording medium ejection path HP is then directed upward and deflected by the inner guide part  72  and the outer guide part  73 , then ejected toward the front side of the ejection tray  71  via ejection roller  74 . 
   On the periphery of the photosensitive drum  31  in the laser printer  1 , the conductive brush  34  is not in contact with the area (hereinafter referred to as the non-cleanable area) defined by the tips of the photosensitive drum  31  in the axial direction of the drum (hereinafter referred to as the drum tips) and the tips of the conductive brush  34  (hereinafter referred to as the brush tips). Hence, it is likely that the dust adhering to the photosensitive drum  31  will accumulate and not be removed. Additionally, the area where the periphery of the photosensitive drum  31  is in contact with the conductive brush  34  is defined as cleanable area. 
   Furthermore, the tips of the brush are located toward the center in the axial direction of the drum away from the tips of the development roller  41  (hereinafter referred to as the development roller tip). Thus, a portion of the non-cleanable area is in contact with the periphery of the development roller  41 . Therefore, it may be very possible that the dust adhering to the non-cleanable area of the photosensitive drum  31  migrates to the surface of the development roller  41 . 
   One reason for the dust adhering to the non-cleanable area of the photosensitive drum  31  is that the dust is suspended in air after being removed by the conductive brush  34  and migrates to the tips of the photosensitive drum  31 . 
   In the laser printer  1 , the sponge material part  36  is in contact with a portion of both tips on the periphery of the photosensitive drum  31 . At least some of the dust suspended in air after being removed by the conductive brush  34 , where the sponge material part  36  is located, is collected by, for example adhering to, the sponge material part  36  and thus is prevented from reaching either tip of the photosensitive drum  31 . In essence, the dust collected by the sponge material part  36  causes the dust adhering to the non-cleanable area to be reduced. 
   In this manner, the amount of dust migrating to the development roller  41  is reduced which can suppress toner leakage and uneven toner coverage. 
   Additionally, of the tips of the sponge material part  36  in the axial direction of the drum  31 , the tip away from the film  35  (hereinafter referred to as the sponge outer tip) is located at the tip end of the axial direction of the drum away from the tips of the development roller tips. In other words, the development roller tips are located further inward from the drum tips toward the center part of the drum  31  than the sponge outer tip in the axial direction of the drum  31 . 
   On the periphery of the photosensitive drum  31 , the dust does not migrate to the development roller  41  if the dust adheres to the segment of the non-cleanable area between the sponge outer tips of the development roller  41  and the tips of the photosensitive drum  31  in the axial direction of the drum. This occurs because the development roller  41  is not in contact with this segment of the non-cleanable area. 
   Thus, the dust causing toner leakage and uneven toner coverage may be prevented in segments of the non-cleanable area where adhesion to the photosensitive drum  31  cannot be prevented (the portions from the outer edge of the sponge  36  to the edge along the axial direction of the drum  31 ) by the sponge material part  36 dust. 
   Other aspects of the present invention will be discussed with reference to the drawings below. Only parts that differ from those described in the above aspects will be discussed. 
     FIG. 5  is a perspective view of the core of a photosensitive cartridge  30  according to another illustrative aspect of the invention.  FIG. 6  is an illustration of the relationship and the locations of the photosensitive drum  31 , a development roller  41 , a conductive brush  34 , a film  35 , and wall parts  101  of  FIG. 5 . 
   As shown in  FIG. 5  and  FIG. 6 , the difference between the laser printer  1  as compared with the aspects described above is the elimination of the sponge material part  36  and the addition of the wall parts  101 dust. 
   The wall parts  101 , as shown in  FIG. 5 , may protrude away from the axial direction of the photosensitive drum  31  at angle of between 75 and 105 degrees, for example in a perpendicular direction from the drum  31 . A minimal gap may exist between the wall parts  101  and the photosensitive drum  31  to avoid damage to the drum  31  when a material (e.g., plastic) having a coefficient of friction greater than the coefficient of friction of the photosensitive drum  31  is used as the wall parts  101 . When a material (e.g., a sponge) which has a coefficient of friction less than a coefficient of friction of photosensitive drum  31  is used, the wall parts  101  may contact the drum  31 . 
   In such a laser printer  1 , the migration of dust to the outer axial direction of the photosensitive drum  31  can be prevented when the dust is migrating along the axial direction of the drum from the center part to each tip part in the axial direction of the drum  31  (hereinafter referred to as the outer axial direction of image carrier). In this instance, the dust can contact a wall part  101  and may be diverted toward the film  35  or dust collector  39 . The tips of the photosensitive drum  31  (drum tips) are situated beyond the wall parts  101  and therefore, migration of dust in the outer axial direction of the image carrier can be prevented by wall parts  101  and the amount of dust adhering to the non-cleanable area of the photosensitive cartridge can be reduced. 
   In this way, the amount of paper dust migrating into the development roller  41  can be reduced, which can suppress the toner leakage and reduce the possibility of uneven toner coverage. 
   Other illustrative aspects of the present invention will be discussed with reference to the drawings below. Only parts that differ from those in aspects described above will be discussed. 
     FIG. 7  is a perspective view of the core of a photosensitive cartridge  30  according to aspects of the invention.  FIG. 8  exhibits the relationships and locations of the photosensitive drum  31 , the developing roller  41 , the conductive brush  34 , and the film  111  of  FIG. 7 . 
   As shown in  FIG. 7  and  FIG. 8 , the differences between the laser printer  1  according to these aspects of the invention when compared with the laser printer  1  described in connection with  FIGS. 3 and 4  is the elimination of the film  35  and the addition of a film  111 . 
   The film  111 , similar to the film  35 , can block the gap between the photosensitive drum  31  and the dust collector  39 . The tips of the film  111  are in contact with the photosensitive drum  31  and the dust collector  39  collects the dust removed by the conductive brush  34  along with the film  111 . 
   As shown in  FIG. 8 , the width of the film  111  along the axial direction of the drum (film width) is less than the width of the photosensitive drum  31  (photosensitive drum width) in its axial direction, but greater than the width of the development roller  41  (development roller width) in the axial direction of the drum  31 . 
   In such a laser printer  1 , the film  111  extends to the portion where the sponge material part  36  extends as shown in  FIG. 4 . In this manner, a lesser number of components to collect the dust may be used when compared to, for example, the aspects of the invention described with respect to  FIG. 4 . 
   While certain aspects of the invention have been discussed above, the present invention is not limited to the above described aspects. Many modifications are possible and may be realized as understood by one of ordinary skill in the art. 
   For example, a sponge material can be used to collect dust as described. However, in place of a sponge material any material with some degree of elasticity can be used as long as the material can be pressed on the peripheral surface of the photosensitive drum  31  without damaging the surface. 
   Additionally, aspects of the invention are not limited to a monochrome laser printer and may also be applied to a color laser printer.