Patent Publication Number: US-6993267-B2

Title: Image carrier unit and image forming apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This patent document claims priority to Japanese Patent Publication 2002-325226 filed Nov. 8, 2002, and 2003-305697 filed Aug. 29, 2003, the entire contents of each of which are hereby incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention is directed to an electro-photographic image forming apparatus such as a printer, a facsimile device, a copy machine, etc., and is particularly directed to a replaceable process cartridge used in such an image forming apparatus. 
   2. Discussion of the Background 
   In an image forming device it is known to utilize an image carrier unit having a housing that contains an image carrier. Such an image carrier unit is replaceable to improve efficiency when such an image carrier unit becomes worn out or defective and needs to be replaced. Such an image carrier unit can be formed as a process cartridge that contains a developing device that develops an electrostatic latent image written on the surface of an image carrier and a cleaning unit that cleans a surface of the image carrier. Such a process cartridge also includes a housing with an opening that allows the image carrier to make contact with a transfer member, a paper sheet, etc. 
   In such an image forming device attention must be paid to avoiding contact with the image carrier through the opening in the housing. Particularly, attention must be paid that a worker&#39;s hand does not touch the image carrier when replacing the image carrier unit, or that foreign substances do not adhere to the image carrier. Light should also be prevented from impinging on the image carrier through the opening to prevent breakdown of the image carrier surface. Paying attention to the above-noted matters is particularly significant because the image carrier unit can be replaceably installed by a worker, and at that point must be handled by the worker. 
   Before an image carrier unit is installed into an image forming apparatus, the opening portion in the housing can be covered with a seal member. After the image carrier unit is installed into the image forming apparatus, the seal member is removed from the image carrier unit. An example of such an operation is disclosed in Japanese Patent Laid Open No. 59-61848. In that device a seal member is formed of a material such as a polyester film, which has a drawback that such a material is difficult to tear. 
   The present inventors recognized that an image carrier is particularly susceptible to damage because when a toner image on an image carrier is transferred to a transfer member or a paper sheet, it is necessary that some outer part of the image carrier protrude from an opening of the housing to contact the transfer member or paper sheet. As a result it becomes more difficult to protect that protruding portion of the image carrier. 
   The present inventors also recognized that when the opening of the housing is covered by a hard seal member, the outer layer of the image carrier may become damaged from contact with or rubbing against the hard seal member. Particularly when transporting the image carrier unit, for example prior to installing the image carrier unit, vibration caused by rotation of the image carrier may more easily result in contact between the outer layer of the image carrier and the hard seal member, again resulting in damage to the outer layer of the image carrier. 
   SUMMARY OF THE INVENTION 
   Accordingly, one object of the present invention is to address the above-noted and other drawbacks in the background art. 
   A more specific object of the present invention is to provide a novel image carrier unit structure in which an outer layer of an image carrier, particularly if it protrudes from an opening of a housing, is effectively protected against damage. 
   Another object of the present invention is to provide a novel seal structure for a novel image carrier unit and image forming device that is easy to implement, but that still properly protects an image carrier from damage particularly during transporting thereof, and that also protects the image carrier from light. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of the present invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
       FIG. 1  shows an interior construction of a printer according to an embodiment of the present invention; 
       FIG. 2  shows an exterior construction of a cartridge used in the printer of  FIG. 1 ; 
       FIG. 3  shows an exterior construction of the cartridge of  FIG. 2  before tearing off a seal member; 
       FIG. 4  shows an exterior construction of the cartridge of  FIG. 2  in the process of tearing off a seal member; and 
       FIG. 5  shows in interior construction of the cartridge of  FIG. 2 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, and more particularly to  FIG. 1  thereof, a color printer P as an example of an image forming device to which the present invention is applicable is shown. The present invention is applicable to other image forming devices than a color printer, as would be apparent to those of ordinary skill in the art. 
   As shown in  FIG. 1 , the color printer P includes a main body  1  and an ejection portion  2  at a top of the main body  1 . That ejection portion  2  receives paper sheets that have had images printed thereon, from the main body  1 . 
   In the main body  1  a stack of paper sheets  3  is piled on a paper feed portion  4 . Further, a paper conveyance path  5  is provided such that the paper sheets  3  piled on the paper feed portion  4  can be conveyed to the ejection portion  2 . A paper conveyance roller pair  6  is formed in the paper conveyance path  5 , and a fixing unit  7  is provided further downstream of the paper conveyance roller pair  6 . A paper feed roller  8  is provided to feed the paper sheets  3  one at a time from the paper feed portion  4 . 
   Further, within the main body  1  of the color printer P an image forming portion  9  is provided. The image forming portion  9  includes an intermediate transfer belt  10  supported by a drive roller  10   a  and a driven roller  10   b . Four photoconductor units  20  are disposed along the intermediate transfer belt  10  in the rotation direction of the intermediate transfer belt  10 . The four photoconductor units  20  each individually include a photoconducting portion forming a toner image of a respective color of Y (yellow), M (magenta), C (cyan), and K (black). The details of each photoconducting unit  20  are shown in  FIGS. 2–5 .  FIG. 2  shows a representative photoconducting unit  20  without a seal member, the seal member being described in further detail with respect to  FIGS. 3–5 . 
   Each photoconductor unit  20  includes a housing  21 , a photoconductor roller  11  that rotates within the housing  21 , a charging roller  12  deployed around the photoconductor roller  11 , a developing device  13 , a first transfer roller  14 , and a cleaning unit  15 . The developing device  13  includes a developer accommodation portion  13   a  and a developer roller  13   b.    
   Further, the image forming portion  9  includes an exposure unit  16  to form an electrostatic latent image onto the surface of each photoconductor roller  11 , and a cleaning unit  17  to clean intermediate transfer belt  10 . The exposure unit  16  includes various optical components such as lenses, a polygonal mirror, etc. 
   A second transport roller  18  is also provided in contact with the driven roller  10   b  to contact the intermediate transfer belt  10  under a pressure. In addition, developer (e.g. toner) is replenished to each developing device  13  from toner in various toner bottles  19 . 
   The fixing unit  7  includes a heating roller  7   a  with a heating function and a pressure roller  7   b . An image can be fixed onto paper sheets  3  passing through the fixing unit  7  by the heating roller  7   a  and the pressure roller  7   b.    
   An operation of image forming in the color printer P is now described. 
   In the image forming portion  9 , the surface of the photoconductor roller  11  for each photoconductor unit  20  is charged by the charging roller  12 . An electrostatic latent image corresponding to desired image data is then formed on each photoconductor roller  11  by a signal output from the exposure unit  16 . Each electrostatic latent image is then developed by a respective developing device  13 , and thereby a toner image is formed on each photoconductor roller  11 . The toner images formed on each respective photoconductor roller  11  are then transferred to the surface of the intermediate transfer belt  10  by the respective transfer rollers  14 , in registration. 
   Also, paper sheets  3  piled up on the paper feed portion  4  are then fed to contact the tip portion of the paper conveyance roller pair  6  by the paper feed roller  8 . Each individual paper sheet  3  is then conveyed to the nip portion between the transfer belt  10  and the second transfer roller  18  by the paper conveyance roller pair  6 , and thereby a toner image on the intermediate transfer belt  10  is then transferred to the paper sheet  3 . The paper sheet  3  then subsequently passes through the fixing unit  7 , and the toner image on the paper sheet  3  is fixed by the fixing unit  7 . The paper sheet  3  with a fixed image is then ejected to the ejection portion  2 . 
   Further, after the above-noted operation residual toner remaining on the different photoconductor rollers  11  is removed by their respective cleaning units  15 . The photoconductor rollers  11  are then electrically neutralized at the same time by their respective charging rollers  12 . With those operations the photoconductors rollers  11  are then in a state in which they are ready to execute a next image forming process. 
   Further, residual toner from the intermediate transfer belt  10  is cleaned by the cleaning unit  17 , so that the intermediate transfer belt  10  is also then ready for a next image forming operation. 
   It is also noted that in the color printer P of  FIG. 1  the respective first transfer rollers  14  corresponding to photoconductor rollers  11  of the photoconductor units  20  forming toner images of yellow (Y), magenta (M), and cyan (C) can be held in a state in which they do not contact the intermediate transfer belt  10  in an operation in which only a monochrome black image is formed. In that operation only the transfer roller  14  corresponding to the black (K) photoconductor unit  20  is held in contact with the intermediate transfer belt  10 . Further, at a time of exchanging any of the different photoconductor units  20 , it may be desirable to place all of the transfer rollers  14  in a position in which none of the transfer rollers  14  contact the intermediate transfer belt  10 . A mechanism provided in the main body  1  to support the intermediate transfer belt  10  and to move the first transfer rollers  14  to either contact the intermediate transfer belt  10  or to be spaced apart from the intermediate transfer belt  10  is not detailed in  FIG. 1 , but is known to those of ordinary skill in the art. 
   Specifics of the individual photoconductor units  20  are now further explained with reference to  FIGS. 2–5 .  FIG. 2  shows a state of the photoconductor unit  20  without a sealing member for clarity&#39;s sake. 
   Each photoconductor unit  20  in the present embodiment includes a photoconductor roller  11 , a charging roller  12 , a developing device  13 , and a cleaning unit  15 , all placed inside a main housing  21 . A handle  22  is also disposed at both side ends of an axis direction of the photoconductor roller  11  and a positioning portion  23  is provided to connect with the main body  1  of the color printer P, to ensure proper positioning of the photoconductor unit  20  in the color printer P. That handle  22  and positioning portion  23  are also formed in the housing  21 . 
   The housing  21  further includes a feeding portion  27  that allows feeding a bias to the charging roller  12 , a feeding portion  26  that allows feeding a bias to a diffusion brush  15   a  of the cleaning unit  15  (see  FIG. 5 ), a feeding portion  25  that allows applying a developing bias to the developing roller  13   b  of the developing device  13  (see  FIG. 5 ), and a ground member  24  to ground the photoconductor roller  11 . In addition the ground member  24  functions as a support for the photoconductor roller  11 . 
   As shown in  FIG. 2 , a developer seal member  28  is provided to protrude beyond a front portion  29  of the housing  21  underneath the developing bias feeding portion  25 . That developer seal member  28  protects the photoconductor roller  11 , and particularly prevents developer from adhering to the photoconductor roller  11  in transporting the photoconductor unit  20 . That is, the developer seal member  28  seals a gap between the developer accommodating portion  13   a  and the developer roller  13   b  (see  FIG. 1 ). Viewed at from the front portion  29  of the housing  21 , the developer seal member  28  is adhered from a front end of the developer roller  13   b  towards a back end of the photoconductor unit  20 , for example by heat melting or by two-sided tape. The developer seal member  28  is held back at a back end of the photoconductor unit  20 , and is then pulled towards the front end to remove the developer seal member  28  after the photoconductor unit  20  has been installed into the image forming apparatus. By pulling towards the front end of the developer seal member  28 , the developer seal member  28  is removed from the developing device  13  to open the portion between the developer accommodating portion  13   a  and the developing roller  13   b  when the photoconductor unit  20  is installed into the image forming apparatus. 
   As also shown in  FIGS. 2 and 4 , an opening portion  30  is formed at a top of the housing  21  to allow a portion of the photoconductor roller  11  to protrude from the housing  21 . That structure allows the photoconductor roller  11  to contact the intermediate transfer belt  10  in the present embodiment. That structure could also allow the photoconductor roller  11  to directly contact a paper sheet. 
   Further, an adhesion portion  31  including a step is formed at both sides of the opening portion  30  along an axis direction of the photoconductor roller  11 . As viewed from the front portion  29  of the housing  21 , a guide portion  33  is further formed at a front end of the adhesion portion  31 . 
   As shown in  FIGS. 3 and 4 , a further seal member  32  is provided to cover the opening portion  30 . That further seal member  32  is formed of a soft flexible material that is softer than the surface of the photoconductor  11 . As an example of materials that form the seal member  32 , flexible materials such as polyurethane rubber with a thickness of about 0.2 mm can be utilized. Such polyurethane rubber should also be formed to be black to additionally achieve a light blocking effect. 
   The seal member  32  extends in an axis direction of the photoconductor roller  11  and has a central covering portion  35  that covers substantially all of the opening portion  30 , and thereby that central cover portion  35  covers the portion of the photoconductor roller  11  protruding from the opening portion  30 . That seal member  32  is turned-back on itself (i.e. is folded back to be U-shaped) so that a turned-back portion thereof is underneath the top surface. That turned-back portion  34  directly covers the photoconductor roller  11 . 
   Further, the turned-back portion  34  is turned back at the ends thereof adjacent to the adhesion portion  31  of the housing  21 . The turned-back portion  34  is turned back in an axis direction of the photoconductor roller  11 . 
   Further, the seal member  32  includes a reinforcement portion  36  at each side of the central cover portion  35  and turned-back portion  34 , and also formed in an axis direction of a photoconductor roller  11 . The seal member  32  further includes a handle portion  37  that is attached at an end of the seal member  32 . Handle portion  37  can be formed of a relatively hard material such as a resin. The seal member  32  is provided in the photoconductor unit  20  such that the reinforcement portions  36  go through the guide portions  33  of the housing  21 . In removing the seal member  32  from the housing, the reinforcement portions  36  provide a good guide operation through the guide portion  33 . 
   The reinforcement portions  36  can be formed by bending a polyester sheet of elastically hard millers (e.g., from the Dupont company) on either side of the seal member  32  as lining materials. 
   The seal member  32  can be bonded onto the adhesion portion  31  of the housing  21 . That adhesion can be performed by specifically adhering the reinforcement portions  36  to the adhesion portion  31 , the reinforcement portion  36  in turn being bonded to the main cover portions  35  and turned-back portion  34 . The adhesion of the reinforcement portions  36  to the adhesion portion  31  of the housing can, for example, be effectuated by an adhesive, a two-sided tape, etc. The adhesion should not be so strong to prevent the seal member  32  from being removed by pulling the handle portion  37 . The handle portion  37  is positioned at an end of the sealing member  32  and is also made rigid particularly with respect to the reinforcement portions  36 , i.e. connected to the reinforcement portions  36 . 
   When the handle portion  37  is pulled to tear off the seal member  32  from the housing  21 , almost all of the tension acts on the reinforcement portions  36  so that the seal member  32  can be removed smoothly and without tearing. 
   In addition, one end of the developer seal member  28  can be fixed to the handle portion  37 . With that structure, when the seal member  32  is torn off from the housing  21  by pulling the handle portion  37  in the direction indicated by the arrow A in  FIG. 4 , the seal member  28  is also torn off at the same time. 
   Further, the handle portion  37  can extend beyond the front face  29  of the photoconductor unit  20  such that if the seal member  32  and the developer seal member  28  are not properly removed, the front door of the image forming apparatus will not close. That prevents a user from forgetting to remove the seal member  32  and the developer seal member  28  from the photoconductor unit  20  after the photoconductor unit  20  is installed in an image forming apparatus. 
   With the photoconductor unit  20  with the structure as noted above, the seal member  32  can protect the photoconductor roller  11 , particularly at a time when the photoconductor unit  20  is being transported and then installed into an image forming apparatus. Further, since the seal member  32  is made of a softer material than that of the photoconductor roller  11 , even if the seal member  32  touches an outer layer of the photoconductor roller  11 , particularly the portion of the photoconductor roller  11  protruding from the opening portion  30 , the photoconductor roller  11  can still be prevented from being damaged. 
   Further, by bonding the seal member  32  to the adhesion portion  31  such that the seal member  32  is pulled in a width wise direction, i.e., at a right angle to an axis direction of the photoconductor roller  11 , a stress state in the seal member  32  against the photoconductor roller  11  can be maintained. That is, the seal member  32  has the central cover portion  35  and the reinforcement portions  36  at both edges thereof, and additionally the turned-back portion  34  and the handle portion  37  fixed to the reinforcement portions  36  at an end of the turned-back portion  34 . With such a structure, when the handle portion  37  is gripped to tear off the seal member  32  from the housing  21 , a pulling force is transmitted directly to the reinforcement portions  36  so that the seal member  32  does not stretch. As a result the seal member  32  becomes easy to tear off. 
   Further, at a time of transporting or installing the photoconductor unit  20 , relative movement of the photoconductor roller  11  and the seal member  32  can be controlled so that again any damage caused on the photoconductor roller  11  by contact with the seal member  32  can be further prevented. Further, the seal member  32  and the developer seal member  28  can be torn off from the housing  21  at a same time when a photoconductor unit  20  is changed by merely gripping the single handle portion  37  and pulling the single handle portion  37  in the direction indicated by the arrow A. 
   Further, the seal member  32  as noted above has a light blocking effect to prevent deterioration of the photoconductor roller  11  by light. 
     FIG. 4  shows a specific state in the process of removing the seal member  32  in which the developer seal member  28  is also removed when the handle  37  is pulled in the direction indicated by arrow A. In this case, although the seal member  32  is formed of a flexible material, since the reinforcement portions  36  are bonded to the adhesion portion  31 , the central cover portion  35  of the seal member  32  can be prevented from stretching. Thereby, the seal member  32  can be easily torn off. 
   Further, when tearing off the seal member  32  from the housing  21  the reinforcement portions  36  are positioned on both sides of the seal member  32  and are guided by the guide members  33  in the housing  21 . As a result, the seal member  32  can be pulled smoothly and in a straight direction so to again make the seal member  32  easy to tear off. 
   Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described herein.