Patent Publication Number: US-7212770-B2

Title: Photoconductive drum device

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a photoconductive drum device having a frame, a photoconductive drum supported rotatably on the frame under a state in which a part of an outer circumferential surface of the photoconductive drum is exposed, and a cover supported on the frame in a manner capable of swinging for protecting the photoconductive drum. 
   2. Description of Related Art 
   An open-and-close cover is provided on a main body of an image forming device such as a copying machine, a facsimile machine and a printer. In a conventional image forming device, after the open-and-close cover is opened and an inner part of the device main body is exposed, a user can carry out maintenance work on a photoconductive drum device or the like provided removably in the device main body. In such a conventional image forming device, the open-and-close cover is provided at an upper part of the device main body. When the open-and-close cover is opened, a process cartridge including a photoconductive drum can be removed from an upper side of the device main body. An openable and closable shutter mechanism for covering an exposed part of the photoconductive drum is provided on the process cartridge to prevent the hand of the user or the like from making contact with the exposed part of the photoconductive drum. 
   The process cartridge includes a shutter, a supporting member, an elastic member and a force receiving member. The shutter protects the photoconductive drum and is supported by the supporting member. The shutter can move between a protection position and a receded position. At the protection position, the shutter protects the photoconductive drum. The receded position is located at a rear side of the protection position in a direction in which the process cartridge is inserted into the device main body. The elastic member urges the shutter toward the protection position by an elastic force of the elastic member. The force receiving member is provided on the supporting member and is used for inserting the process cartridge into the device main body. The force receiving member makes contact with an edge of an opening provided on an upper surface of the device main body and receives a force to move the shutter backward in the inserting direction against the elastic force of the elastic member. Since the process cartridge has the above-described structure, when the process cartridge is inserted into the device main body, the shutter can be opened automatically, and when the process cartridge is removed, the shutter can be closed automatically. 
   SUMMARY OF THE INVENTION 
   According to an aspect of the present invention, even in case of an image forming device having a structure in which a photoconductive drum device including a photoconductive drum is inserted and removed horizontally, when the photoconductive drum device is removed from a device main body, an exposed part of the photoconductive drum can be covered automatically. Therefore, the photoconductive drum can be prevented from being touched accidentally by the hand of a user or the like. 
   According to an aspect of the present invention, a photoconductive drum device is inserted into and removed from an image forming device main body, horizontally from a side of the image forming device main body. The photoconductive drum device includes a frame, a photoconductive drum and a cover. The photoconductive drum is supported rotatably on the frame under a state in which a part of an outer circumferential surface of the photoconductive drum is exposed. The cover is also supported on the frame in a manner capable of swinging. In response to an insertion movement in which the photoconductive drum device is inserted horizontally into the image forming device main body, the cover swings to an opened position so as not to block off a light path of an exposure ray irradiated toward the exposed part of the photoconductive drum. In response to a removal movement in which the photoconductive drum device is removed horizontally from the image forming device main body, the cover swings to a closed position so as to cover the exposed part of the photoconductive drum. 
   According to the above aspect of the present invention, when the photoconductive drum device is removed from the image forming device main body, the cover closes automatically and the exposed part of the photoconductive drum is covered. Therefore, the exposed part of the photoconductive drum is prevented from being touched accidentally by the hand of the user or the like. Thus, a maintenance work can be carried out easily. 
   According to another aspect of the present invention, the image forming device main body includes a rack. A longitudinal direction of the rack is provided toward a direction in which the photoconductive drum device is inserted. A pinion, a gear and a rotational force transmitting device are preferable to be provided on the frame of the photoconductive drum device. The pinion engages with the rack. The gear is provided on a rotational shaft of the cover. The rotational force transmitting device transmits a rotational force from the pinion to the gear. 
   According to the above aspect of the present invention, when removing the photoconductive drum device from the image forming device main body, a pinion gear is guided by the rack and rotates. A rotational force is transmitted from the pinion gear via the rotational force transmitting device to the gear of the cover. Therefore, the cover closes automatically and the exposed part of the photoconductive drum is prevented from being touched accidentally by the hand of the user or the like. 
   According to another aspect of the present invention, an urging member is provided between the frame and the cover. When the urging member is located at a position located closer to the photoconductive drum than a dead center (a center of the shaft of the cover), the urging member preferably urges the cover in a direction to close the cover. When the urging member is located at a position located away from the photoconductive drum than the dead center, the urging member preferably urges the cover in a direction to open the cover. 
   According to the above aspect of the present invention, the cover swung to the opened position is urged by the urging member, and unless a force is applied to the cover to some extent, the cover does not close from the opened position by a weight of the cover. The cover swung to the closed position is urged by the urging member, and unless a force is applied to the cover to some extent, the cover does not open from the closed position by the weight of the cover. Thus, reliability is improved. 
   According to another aspect of the present invention, a buffer member, which makes contact with the photoconductive drum, is preferable to be provided on a surface of the cover of a side covering the photoconductive drum. 
   According to the above aspect of the present invention, the cover is prevented from making direct contact with the surface of the photoconductive drum by the buffer member provided on the cover. Therefore, the surface of the photoconductive drum can be prevented from being damaged. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       FIG. 1  is a side view showing a schematic structure of an image forming device. 
       FIG. 2  is a cross-sectional front view showing a schematic structure of the image forming device. 
       FIG. 3  is a perspective view of a photoconductive drum device. 
       FIG. 4  is a front view of the photoconductive drum device. 
       FIGS. 5A through 5C  are cross-sectional side views of the photoconductive drum. 
       FIG. 6  is a plan view of a mechanical swing device. 
       FIG. 7  is a side view of the mechanical swing device. 
       FIG. 8  is a plan view of a gear having a locking member. 
       FIG. 9  is a cross-sectional side view showing a drum cover and a coil spring. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Embodiments of the present invention will be described. Further, the embodiments to be described below are preferable specific examples for implementing the present invention. Therefore, there are various technical limitations in the description. However, unless explicitly stated in the following description to limit the present invention, the present invention shall not be limited to the embodiments. 
   With reference to the drawings, an embodiment of the present invention will be described. First, a description will be given briefly of an image forming device  1  preferably provided in a copying machine, a facsimile machine or the like. As shown in  FIG. 1 , the image forming device  1  is disposed above a paper feed cassette  5 . A paper discharge tray  6  is formed at an upper part of the image forming device  1 . As shown in  FIG. 2 , a main transportation path  11  and a reversal path  12  are formed inside the image forming device  1 . The main transportation path  11  is a path for transporting recording paper fed in from the paper feed cassette  5  to the paper discharge tray  6 . The reversal path  12  is a path for reversing a front side and a back side of the printing paper. The reversal path  12  is disposed at an outer side of the main transportation path  11 . The reversal path  12  starts by diverging from the main transportation path  11  and ends by joining to the main transportation path  11 . Along the main transportation path  11 , a developing device  2 , a photoconductive drum device  3  and a fixing device  4  are disposed toward a downstream side (upward). 
   The photoconductive drum device  3  includes a photoconductive drum  31  and a charger  32  or the like. As a photoreceptor, the photoconductive drum  31  has a photoconductive layer on an outer circumferential surface. The charger  32  charges the outer circumferential surface of the photoconductive drum  31 . When a high voltage is impressed to a discharge wire of the charger  32 , a corona discharge is generated. By the corona discharge, a negative electric charge is applied evenly to the outer circumferential surface of the photoconductive drum  31 . 
   An exposing device (not shown) is disposed diagonally above the photoconductive drum  31 . The exposing device is a laser scanner unit. The exposing device irradiates an exposure ray  50  in accordance with input image information onto the outer circumferential surface of the photoconductive drum  31  charged by the charger  32 . The negative electric charge is eliminated from a part irradiated by the exposure ray  50 , and an electrostatic latent image corresponding to the image information is formed on the outer circumferential surface of the photoconductive drum  31 . 
   The developing device  2  includes a supply roller  21  and a developing roller  22  or the like. The supply roller  21  negatively charges toner in a toner case  20 , which accommodates the toner, and supplies the negatively charged toner to the developing roller  22 . The developing roller  22  supplies the toner to the photoconductive drum  31  on which the electrostatic latent image is formed. By an electrostatic force, the toner is adhered only to the part on the photoconductive drum  31  where the negative electric charge is eliminated. 
   A transfer roller  61  is disposed across the main transportation path  11  so as to make contact with the outer circumferential surface of the photoconductive drum  31 . Printing paper is fed into a nip part between the photoconductive drum  31  and the transfer roller  61 . Under this state, when a bias voltage is impressed to the transfer roller  61  from a back side of the printing paper adhered on the photoconductive drum  31 , the negatively charged toner is transferred from the photoconductive drum  31  onto the printing paper. 
   The fixing device  4  includes a heat roller  41  and a press roller  42  which is pressed against an outer circumferential surface of the heat roller  41  across the main transportation path  11 . The printing paper is fed into a nip part between the heat roller  41  and the press roller  42 . At this time, the printing paper after the transfer is heated and pressured by the heat roller  41  and the press roller  42  and a toner image on the printing paper is fixed. 
   As described above, the toner image is formed on the printing paper fed from the paper feed cassette  5 . After the toner image is fixed by the fixing device  4 , the printing paper is discharged onto the paper discharge tray  6 . 
   Referring to  FIG. 1  again, an open-and-close cover  10  for a maintenance work is mounted on a front surface side, which is one side of a device main body  100 . The open-and-close cover  10  can be swung vertically with a lower position of the device main body  100  as a center. When carrying out maintenance work of the photoconductive drum device  3  or the like accommodated inside the device main body  100 , the open-and-close cover  10  is opened and the front surface side of the device main body  100  is opened. Accordingly, an inner part of the device main body  100  is exposed. Further, the photoconductive drum device  3  is inserted into or removed from the device main body  100  in a horizontal direction orthogonal to a direction in which the printing paper is transported (in  FIG. 1 , in a left-right direction). 
   Referring to  FIGS. 3 and 4 , the photoconductive drum device  3  will be described. The photoconductive drum device  3  includes a drum frame  30 , the photoconductive drum  31 , a drum cover  39  and a gripper  38 . The photoconductive drum  31  is supported rotatably at a lower part of the drum frame  30  (at a side of the drum frame  30  located on a side of the transfer roller  61 ) under a state in which a part (a lower part) of the outer circumferential surface of the photoconductive drum  31  is exposed. The drum cover  39  is also supported on the drum frame  30  in a manner capable of swinging. The gripper  38  is provided at one end of the drum frame  30  in a longitudinal direction. The photoconductive drum device  3  is inserted horizontally into the device main body  100  from another end in the longitudinal direction (from a left side in  FIG. 4 ). A driving gear  35  is provided at the other end of the photoconductive drum  31  in the longitudinal direction. The driving gear  35  engages with a drive transmitting gear of the device main body  100 . 
   As shown in  FIG. 2 , an opening is formed in the lower part of the drum frame  30  (at the side of the drum frame  30  located on the side of the transfer roller  61 ). A part of the outer circumferential surface of the photoconductive drum  31  is exposed from the opening. The exposing device irradiates the exposure ray  50  toward the outer circumferential surface of the photoconductive drum  31  exposed from the opening. 
   As shown in  FIGS. 5A through 5C , the drum cover  39  for covering the opening is mounted on the drum frame  30 . The drum cover  39  swings by a mechanical swing device  7  to be described later. Specifically, when the photoconductive drum device  3  is inserted into the device main body  100 , in response to the insertion movement, the drum cover  39  swings to an opened position (refer to  FIG. 5A ) so as not to block off a light path of the exposure ray  50 . Meanwhile, when the photoconductive drum device  3  is removed from the device main body  100 , in response to the removal movement, the drum cover  39  swings to a closed position (refer to  FIG. 5C ) so as to cover the exposed part of the photoconductive drum  31 . 
   At least one buffer member  40  is mounted on a surface of the drum cover  39  of a side covering the photoconductive drum  31 . When the drum cover  39  is closed, the buffer member  40  makes contact with the photoconductive drum  31 . The buffer member  40  is a sponge or the like, and is adhered on the surface of the drum cover  39  of the side covering the photoconductive drum  31 . The drum cover  39  is prevented from making direct contact with the surface (the outer circumferential surface) of the photoconductive drum  31  by the buffer member  40 . As a result, the surface of the photoconductive drum  31  is prevented from being damaged. 
   Further, in the present embodiment, the buffer member  40  is provided at both ends of the drum cover  39  in the longitudinal direction. However, the buffer member  40  can be provided at three positions, for example, at both ends and at a center part of the drum cover  39  in the longitudinal direction. Alternatively, the buffer member  40  can be provided over the entire surface of the drum cover  39  at the side covering the photoconductive drum  31 . 
   Next, the mechanical swing device  7  for swinging the drum cover  39  will be described. As shown in  FIG. 4 , brackets  101  and  102  extending downward are formed at both ends of the drum frame  30  in the longitudinal direction. A rotational shaft  103  of the drum cover  39  is supported rotatably by the brackets  101  and  102 . 
   As shown in  FIGS. 6 and 7 , a first spur gear  71  is fixed on the other end of the rotational shaft  103  of the drum cover  39  in the longitudinal direction. A second spur gear  72 , which engages with the first spur gear  71 , is supported rotatably by the bracket  102  at the other end of the drum frame  30  in the longitudinal direction (at left in  FIG. 6 ). A rotational shaft  104  of the second spur gear  72  is disposed in parallel with the rotational shaft  103  of the drum cover  39 . The rotational shaft  104  is held only by the bracket  102 . 
   A first bevel gear  73  is fixed on an end part of the rotational shaft  104  of the second spur gear  72 . At the other end of the drum frame  30  in the longitudinal direction, a second bevel gear  74 , which engages with the first bevel gear  73 , is provided rotatably. A rotational shaft  105  of the second bevel gear  74  is disposed in a direction orthogonal to the rotational shaft  104  of the first bevel gear  73 . The first bevel gear  73  and the second bevel gear  74  constitute a rotational direction converting device. The rotational direction converting device converts a rotation of a gear around a shaft orthogonal to the insertion direction of the photoconductive drum device  3  into a rotation of a gear around a shaft parallel to the insertion direction. 
   A pinion gear  75  is fixed on the rotational shaft  105  of the second bevel gear  74 . A rack  76  is provided in the device main body  100 . The rack  76  engages with the pinion gear  75 . The rack  76  is disposed at an inner side of an accommodation space where the photoconductive drum device  3  is accommodated. The rack  76  is mounted in the device main body  100  via a bracket  16 . A longitudinal direction of the rack  76  is the same as the insertion direction of the photoconductive drum device  3 . The length of the rack  76  in the longitudinal direction is designed to be a length necessary for the drum cover  39  to swing between the opened position and the closed position when the pinion gear  75  is guided from one end to another end of the rack  76  in the longitudinal direction. 
   The above-described mechanical swing device  7  for swinging the drum cover  39  is formed with the gears  71  through  74 , the pinion gear  75  and the rack  76 . A rotational force transmitting device for transmitting a rotational force from the pinion gear  75  to the first spur gear  71  is formed with the gears  72  and  73 . 
   As shown in  FIG. 8 , a locking member  79  is provided at the drum frame  30  located immediately next to at least one gear among the first spur gear  71 , the second spur gear  72  and the pinion gear  75 . The locking member  79  includes an arm portion  106  and a craw portion  107 . The arm portion  106  can be transformed elastically in a direction to approach and separate with respect to the gear  71  (or  72  or  75 ). The craw portion  107  is provided protruding from a tip end of the arm portion  106  toward the gear. The craw portion  107  enters into a space between adjacent teeth of the gear  71  (or  72  or  75 ). 
   Therefore, since the rotation of the gear  71  (or  72  or  75 ) is regulated by the locking member  79 , a transmission of the rotational force by the mechanical swing device  7  is regulated. Thus, unless a force is applied to the mechanical swing device  7  to some extent, the drum cover  39  does not close unintentionally by the weight of the drum cover  39 . 
   As shown in  FIG. 9 , a coil spring  36  as an urging device is mounted between the drum frame  30  and the drum cover  39 . When the coil spring  36  is located at a position closer to the photoconductive drum  31  than the rotational shaft  103  of the drum cover  39  (dead center), the coil spring  36  urges the drum cover  39  in a direction to close the drum cover  39 . When the coil spring  36  is located at a position located further away from the photoconductive drum  31  than the rotational shaft  103  of the drum cover  39 , the coil spring  36  urges the drum cover  39  in a direction to open the drum cover  39 . A stopper member  37  is formed protruding from a side of the drum frame  30  toward the drum cover  39 . Therefore, when the drum cover  39  is swung to the opened position by the coil spring  36 , an end part  109  of a base part  108  of the drum cover  39  makes contact with the stopper member  37  and the drum cover  39  is prevented from swinging any further beyond the opened position. 
   When the drum cover  39  is swung to the closed position by the coil spring  36 , the buffer member  40  makes contact with the outer circumferential surface of the photoconductive drum  31  (refer to  FIG. 5C ), and the drum cover  39  is prevented from swinging further toward the photoconductive drum  31 . 
   Further, a second stopper member can be provided on a side of the drum frame  30  at a side of the drum cover  39 . Accordingly, when the drum cover  39  is swung to the closed position, another end of the base part  108  of the drum cover  39  makes contact with the second stopper member and the drum cover  39  is prevented from swinging further toward the photoconductive drum  31 . 
   As described above, the drum cover  39  swung to the opened position (or the closed position) is urged by the coil spring  36 , which is an urging device. Therefore, unless a force is applied to the drum cover  39  to some extent, the drum cover  39  does not close from the opened position (or open from the closed position) unintentionally by the weight of the drum cover  39 . Thus, reliability is improved. 
   Next, an automatic opening and closing of the drum cover  39  will be described. As shown in  FIG. 1 , under a state in which the drum cover  39  is located at the closed position, the user inserts the photoconductive drum device  3  horizontally into the accommodation space in the device main body  100 . When the photoconductive drum device  3  is inserted into the accommodation space in the device main body  100 , immediately before the photoconductive drum device  3  is inserted completely, the rack  76  of the device main body  100  and the pinion gear  75  of the drum frame  30  start to be engaged with one another. 
   At this time, the gear  71  (or  72  or  75 ) is locked by the locking member  79  and the drum cover  39  is urged by the coil spring  36 . Therefore, a force is required to some extent to push in (or pull out) the photoconductive drum device  3 . 
   When the user continues to push in the photoconductive drum device  3 , the pinion gear  75  is guided by the rack  76  and rotates. Accordingly, a rotational force is transmitted sequentially to the pinion gear  75 , the second bevel gear  74 , the first bevel gear  73 , the second spur gear  72  and the first spur gear  71 . As a result, the drum cover  39  located at the closed position swings from the state shown in  FIG. 5C  via a state shown in  FIG. 5B  to the state shown in  FIG. 5A . As described above, the drum cover  39  swings in response to the insertion movement of the photoconductive drum device  3  into the device main body  100  and is held at the opened position so as not to block of f the light path of the exposure ray  50  irradiated toward the exposed part of the photoconductive drum  31 . 
   When removing the photoconductive drum device  3  from the device main body  100 , immediately after the photoconductive drum device  3  starts to be removed, the pinion gear  75  at the drum frame  30  starts to be guided by the rack  76  at the device main body  100 . When the user pulls out the photoconductive drum device  3  with a force to some extent or more, the pinion gear  75  is guided by the rack  76  and rotates. Accordingly, a rotational force is transmitted to the pinion gear  75 , the second bevel gear  74 , the first bevel gear  73 , the second spur gear  72  and the first spur gear  71 . As a result, the drum cover  39  located at the opened position swings from the state shown in  FIG. 5A  via the state shown in  FIG. 5B  to the state shown in  FIG. 5C . As described above, the drum cover  39  swings in response to the removal movement of the photoconductive drum device  3  from the device main body  100  and is held at the closed position to protect the exposed part of the photoconductive drum  31 . 
   As described above, according to an aspect of the present invention, when the photoconductive drum device  3  is removed from the device main body  100 , the drum cover  39  closes automatically and the exposed part of the photoconductive drum  31  is covered. As a result, the exposed part of the photoconductive drum  31  is prevented from being touched by the hand of the user or the like. Since the photoconductive drum  31  is located in the lower part of the photoconductive drum device  3 , the user finds it difficult to visually confirm the photoconductive drum  31  when removing the photoconductive drum device  3 . Conventionally, there are drawbacks that the user accidentally touches the surface of the photoconductive drum  31  and the toner adheres to the hand of the user. However, according to the present invention, such drawbacks are resolved and maintenance work can be carried out easily.