Abstract:
An image forming device capable of attaching and detaching a process cartridge to and from a frame without moving an LED array when a door is open. The process cartridge includes a first casing supporting a photosensitive drum and a developing roller, and a second casing pivotally movably connected to the first casing and supporting a charger. The second casing is pivotally movable between a first position in which the charger is positioned close to the LED array for image forming operation, and a second position in which the charger is remote from the LED array in accordance with push-in and pull-out movement of the first casing relative to the frame.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority from Japanese Patent Application No. 2008243103 filed Sep. 22, 2008. The entire content of the priority application is incorporated herein by reference. 
       TECHNICAL FIELD  
       [0002]    The present invention relates to an image forming device, and more particularly, to an electrophotographic type image forming device having a photosensitive drum and an LED array. 
       BACKGROUND 
       [0003]    An electrophotographic tape image forming device generally includes a photosensitive drum, a charge unit, an LED array, and a developing unit. The charge unit is adapted for uniformly charging a surface of the photosensitive drum. The LED array is adapted for forming an electrostatic latent image on the charged surface of the photosensitive drum. The developing unit is adapted for forming a visible developer agent image with charged developer agent at the electrostatic latent image. The visible image is then transferred onto an image recording medium such as a sheet, so that the visible image can be formed on the sheet. 
         [0004]    In such a conventional image forming device, a process cartridge is detachably provided to a frame of the device. The process cartridge accommodates therein the photosensitive drum, the charge unit, and the developing unit. The process cartridge can be exchanged with a new process cartridge upon consumption of developer agent or upon degradation of the photosensitive drum. In order to perform such exchange, one of the photosensitive drum, the charge unit and the developing unit may be mechanically interfered with the LED array such as an LED. Such interference may occur easily in a front access type image forming device in which the frame has a front side provided with a cover, and the process cartridge can be detached from the frame through a front opening after opening the cover. 
       SUMMARY 
       [0005]    However, operating position of the LED array may be varied in accordance with a repeated retracting movement of the LED array, which degrades imaging quality. 
         [0006]    It is therefore an object of the present invention to provide an image forming device facilitating detachment of the process cartridge without any movement of the LED array when the door is open. 
         [0007]    This and other objects of the invention will be attained by providing an image forming device including a frame, a process cartridge, and au LED array. The frame has a front opening provided with a door. The process cartridge is detachably assembled in the frame and is accessible through the Font opening upon opening the door. The process cartridge includes a first casing, a photosensitive drum, a second casing, a charger, and a developing roller. The first casing is movably supported by the frame and has a seat portion. The photosensitive drum is disposed in the first casing and has an outer surface in which an electrostatic latent image is formable. The second casing is pivotally movably connected to the first casing and is movable between a first position and a second position in accordance with push-in and pull-out movement of the first casing relative to the frame. The charger is disposed in the second casing for uniformly charging the photosensitive drum. The developing roller is disposed in the first casing for supplying charged developer agent to the photosensitive drum. The LED array is supported to the frame and is provided independent of the first casing and second casing for forming an electrostatic latent image on the photosensitive doll after the photosensitive drum is charged by the charger. The charger is positioned close to the LED array in the first position for image forming operation, and the charger is remote from the LED array in the second position for avoiding mechanical interference therewith. At least one of the second casing and the charger is seated on the seat portion in the second position. 
         [0008]    In another aspect of the invention, there is provided an image forming device including a frame, a process cartridge, a secondary cartridge case, a charger, and an LED array. The frame has a front opening provided with a door. The process cartridge is detachably assembled in the frame and is accessible through the front opening upon opening the door. The process cartridge includes a casing, a photosensitive drum, and a developing roller. The casing is movably supported by the frame. The photosensitive drum is disposed in the casing and has an outer surface in which an electrostatic latent image is formable. The developing roller is disposed in the casing for supplying charged developer agent to the photosensitive drum. The secondary cartridge case is separate from the casing and is detachably assembled in the frame and is accessible through the front opening upon opening the door. The charger is disposed in the secondary cartridge case for uniformly charging the photosensitive drum. The LED array is disposed in the secondary cartridge case for forming an electrostatic latent image on the photosensitive drum after the photosensitive drum is charged by the charger 
         [0009]    In still another aspect of the invention, there is provided a process cartridge to be detachably assembled in an image forming device having a frame and an LED array supported to the frame. The frame has a front opening provided Wraith a door. The process cartridge is detachably assembled in the frame and is accessible Through the front opening upon opening the door. The process cartridge includes a fist casing, a photosensitive drum, a developing roller, a second casing, and a charger. The first casing is movably supported by the frame and has a seat portion. The photosensitive drum is disposed in the first casing and has an outer surface in which an electrostatic latent image is formable. The developing roller is disposed in the first casing for supplying charged developer agent to the photosensitive drum. The second casing is pivotally movably connected to the first casing and is movable between a first position and a second position. The charger is disposed in the second casing for uniformly charging the photosensitive drum. The charger is positioned close to the LED array in the first position for image forming operation, and the charger is remote from the LED array in the second position for avoiding mechanical interference therewith. At least one of the second casing and the charger is seated on the seat portion in the second position. 
         [0010]    In still another aspect of the invention, there is provided a combination of a process cartridge and a secondary cartridge to be detachably assembled in an image forming device having a frame. The frame has a front opening provided with a door. The process cartridge includes a casing, a photosensitive drum, and a developing roller. The casing is movably supported by the frame and is detachably assembled in the frame and is accessible through the front opening upon opening the door. The photosensitive drum is disposed in the casing and has an outer surface in which an electrostatic latent image is formable. The developing roller is disposed in the casing for supplying charged developer agent to the photosensitive drum. The secondary cartridge includes a secondary cartridge case, a charger, and an LED array. The secondary cartridge case is separate from the casing and is detachably assembled in the frame and is accessible through the front opening upon opening the door. The charger is disposed in the secondary cartridge case for uniformly charging the photosensitive drum. The LED array is disposed in the secondary cartridge case for forming an electrostatic latent image on the photosensitive drum after the photosensitive drum is charged by the charger. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    In the drawings, 
           [0012]      FIG. 1  is a schematic vertical cross-sectional view of an image forming device according to a first embodiment of the present invention; 
           [0013]      FIG. 2(A)  is a schematic view of a process cartridge in its operating position according to the first embodiment; 
           [0014]      FIG. 2(B)  is a schematic view of the process cartridge in its detaching or attaching state according to the first embodiment; and 
           [0015]      FIG. 3  is a schematic vertical cross-sectional view of an image forming device according to a second embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    An image forming device according to a first embodiment of the present invention will be described with reference to  FIGS. 1 through 2(B) . The first embodiment pertains to a monochromatic laser printer. The terms “upward”, “downward”, “upper”, “lower”, “above”, “below”, “beneath”, “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. 
         [0017]    The image forming device  1  includes a frame  2  having a front side provided with a door  3  which can be opened and closed. The front side is a side toward which a sheet P formed with an image is ejected. The frame  4  has a lower portion at which a sheet cassette  4  is movable in frontward/rearward direction. In the sheet cassette  4 , a plurality of cut sheets is stacked. Various rollers including a sheet supply roller are provided for conveying each sheet in the sheet cassette  4  to a process cartridge  10  provided at an internal center portion of the frame  2 . 
         [0018]    The process cartridge  10  includes a photosensitive drum  11 , a transfer roller  12 , a cleaner  13 , a charger  14 , and a developing roller  16 . Further, an LED array  15  is provided adjacent the process cartridge  10 , i.e., adjacent to the photosensitive drum  11 . The photosensitive drum includes a drum body grounded, and a photosensitive layer formed thereover and made from a positively chargeable material such as polycarbonade. The drum body includes a rotation shaft  11 A as shown in  FIG. 2(A) . The photosensitive drum  11  is rotatable in a counterclockwise direction in  FIG. 1 . The transfer roller  12  is rotatably provided to nip the sheet P in cooperation with the photosensitive drum  11  for transferring a toner image on the photosensitive drum  11  onto the sheet P. 
         [0019]    The cleaner  13 , the charger  14 , the LED array  15 , and the developing roller  16  are disposed around the photosensitive drum  11  in the order from the transfer roller  12  in the rotating direction of the photosensitive drum  11 . The cleaner  13  is in the form of a roller in rolling contact with the photosensitive drum  11  for removing residual toner (developer agent) remaining on the surface of the photosensitive drum  11 . The charger  14  is a positively charging scorotron type charger having a tungsten wire from which a corona discharge occurs so as to uniformly charge the surface of the photosensitive drum  11  with positive polarity. 
         [0020]    The LED array  15  is fixed to the frame  2  and includes a plurality of light emitting elements (LED array) arrayed in a lateral direction (widthwise direction of the sheet P) for exposing the outer peripheral surface of the photosensitive drum  11  to light in accordance with image data. The developing roller  16  is provided in a toner container  16 A and is adapted for supplying positively chargeable non-magnetic single component type toner accumulated in the toner container  16 A to the outer peripheral surface of the photosensitive drum  11  to form a positively charged thin toner layer thereover. The toner container  16 A is detachably attached to the process cartridge  10  along with the developing roller  16 . However, the toner container can be integral with the process cartridge  10  along with the developing roller. 
         [0021]    After the cleaner  13  removes residual toner on the photosensitive drum  11  during its rotation, the surface of the photosensitive drum  11  is uniformly positively charged by the charger  14 . Then, the surface is exposed to light by the LED array  15 , whereupon electrostatic latent image based on the image data is formed on the surface of the photosensitive drum  11 . The latent image area has a potential lower than that of the remaining portion. 
         [0022]    Then, positively charged toner is supplied to the photosensitive drum  11  from the developing roller  16 . As a result, a visible toner image corresponding to the electrostatic latent image is formed on the surface of the photosensitive drum  11 . 
         [0023]    The transfer roller  12  is rotatable in a clockwise direction in  FIG. 1 . The transfer roller  12  includes a roller shaft made from metal and a rubber layer formed over the roller shaft. The rubber layer is made from ion conductive rubber material. A transfer bias is applied to the transfer roller  12  so as to transfer the toner image onto the sheet P passing through the photosensitive drum  11  and the transfer roller  12 . A fixing unit  23  including a heat roller  21  and a pressure roller  22  are provided. The toner image on the sheet P is thermally fixed when the sheet passes through the heat roller  21  and the pressure roller  22 . A curved sheet discharge path  24  extends from the fixing unit  23  so as to direct the sheet P frontward. A discharge roller  25  is provided at an exit of the discharge path  24  to discharge the sheet P onto a discharge tray (not shown). 
         [0024]    Next, details of the process cartridge  10  will be described. Operating position of the process cartridge  10  is shown in  FIG. 2(A) . The process cartridge  10  includes a first casing  18  in which the photosensitive drum  11 , the transfer roller  12 , and the developing roller  16  are rotatably supported. The first casing  18  includes a pair of side plates having rear upper portions serving as seat or stop portions  18 A. The seat portions  18 A also function as a part of the sheet passage at an operating state of the process cartridge  10 . Operating state implies a state for performing image forming operation. The above-described toner container  18 A is detachably assembled to the first casing  18 . 
         [0025]    The process cartridge  10  also includes a second casing  19  separate from the first casing  18  and made from highly rigid material. The cleaner  13  and the charger  14  are supported in the second casing  19 . The second casing  19  is pivotally movable with respect to the first casing  18  to function as a pivotally movable member. The second casing  19  includes a pair of arms  19 A positioned at laterally outward of the first casing  18 . The rotation shaft  11 A of the photosensitive drum  11  laterally protrudes outwardly from the first casing  18 , and the pair of arms  19 A is pivotally movably supported to the rotation shaft  11 A such that the pair of arms  19 A is angularly movable about an axis of the rotation shaft  11 A. 
         [0026]    The second casing  19  has lateral sides from which a pair of bosses  19 B protrudes laterally outward. The frame  2  has lateral sides formed with a pair of guide grooves  30  so as to guide movement of the pair of bosses  19 B therealong. Each guide groove  30  has a horizontal part  31  and a slanting part  32 . The horizontal part  31  is positioned frontward of the slanting part  32 . In the operating position of the process cartridge  10 , the horizontal part  31  extends frontward from a position immediately below the LED array  15  fixed to the frame  2 , and the slanting part  32  is bent from the horizontal part  31  upward toward rearward from the position immediately below the LED array  15 . 
         [0027]    In the operating position, the boss  19 B reaches a rearmost end portion of the guide groove  30 . In this state, the second casing  19  has been pivotally moved upward together with the charger  14  and the cleaner  13 . Thus, the charger  14  is positioned behind and above the photosensitive drum  11  and away from a sheet path. Therefore, abutment of the sheet P against the charger  14  can be prevented, and degradation of the toner image on the sheet P by the discharge from the charger  14  can be restrained. 
         [0028]    For detaching the process cartridge  10  from the frame  2 , the second case  19  is pivotally moved downward because of the engagement between the boss  19 A and the guide groove  30  upon pulling the cartridge  10  frontward. When boss  19 A is brought into engagement with the horizontal part  31 , the second casing  19  provides its posture capable of avoiding mechanical interference with the LED array  15 . Further, in this case, the charger  14  is positioned rearward of the photosensitive drum  11 , and the second casing  19  is seated on the seat portion  18 A. Therefore, a posture of the second casing  19  is fixed to a non-interference position. 
         [0029]    According to the above-described embodiment, mechanical interference between the charger  14  and the LED array  15  can be obviated without any displacement of the LED array  15 . Further, since the second casing  19  can be seated on the seat portion  18 A, the process cartridge  10  can be assembled into the frame  2  without any mechanical interference with the LED array  15 . Moreover, cleaning to the components of the charger  14  such as the wire can be facilitated by maintaining the seating state of the second casing  19  onto the seat portion  18 A. 
         [0030]    Further, since the second casing  19  is pivotally movable about the rotation shaft  11 A of the photosensitive drum  11 , a constant gap between the outer peripheral surface of the photosensitive drum  11  and the charger  14  can be provided regardless of the pivotal position of the second casing  19 . Accordingly, direct contact of the charger  14  with the surface of the photosensitive drum  11  can be obviated. Further, since the cleaner  13  and the charger  14  are supported to the second casing  19 , the cleaner  13  and the charger  14  are moved concurrently with a constant gap therebetween. Thus, mechanical interference therebetween can be avoided. 
         [0031]    An image forming device according to a second embodiment of the present invention will be described with reference to  FIG. 3  wherein like parts and components are designated by the same reference numerals as those shown in  FIGS. 1 through 2(B) . 
         [0032]    In the image forming device  101  according to the second embodiment, a cleaner  13  is dispensed with. Further, a process cartridge  110  is detachably attached to the frame  102  and includes the photosensitive drum  11 , the transfer roller  12  and the developing roller  16 . In other words, the process cartridge  110  does not include the charger  14 . Instead, an secondary cartridge  130  is provided in which the charger  14  and the LED array  15  are assembled. The secondary cartridge  130  functions as exposure and charger unit and is provided with a handgrip  131 . The secondary cartridge  130  is detachably attached to the frame  102  through the handgrip  131  independent of the attachment and detachment of the process cartridge  110 . 
         [0033]    With such structure, the process cartridge  110  can be attached to and detached from the frame  102  without any mechanical interference between the charger  14  and the LED array  15 , even if the LED array  15  is not moved. 
         [0034]    Various modifications may be conceivable. For example, in the first embodiment, the second casing  19  is seated in the seat portion  18 A. However, the charger  14  can be directly seated on the seat portion  18 A. Further, the LED array  15  can be exchanged with a new LED array. Further, in the second embodiment, the cleaner is dispensed with. However, the cleaner  13  can be provided to the process cartridge  110  or the secondary cartridge  130 . Further, in the second embodiment, a toner container  116 A is detachably attached to the process cartridge  110  along with the developing roller  16 . However, the toner container can be integral with the process cartridge  110  along with the developing roller. Further, shape of the process cartridge  10 ,  110  is not limited to the above described embodiments, but various configurations are conceivable. 
         [0035]    While the invention has been described in detail with reference to the embodiments thereof, it would be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention.