Abstract:
An image forming apparatus including a rotating photosensitive drum, a cleaning blade having a cleaning edge part which makes contact with an outer surface of the photosensitive drum along an axial direction of the photosensitive drum and a bracket having a contact surface where the bracket makes contact with the cleaning blade to support the cleaning blade, the width of the contact surface between the bracket and the cleaning blade being maximum at the center part of the cleaning blade and gradually decreasing from the center part to opposite end sides of the cleaning blade. Thus, a cartridge for an image forming apparatus having a cleaning blade and a bracket prevents poor quality in a cleaning surface of a photosensitive drum and has improved durability.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of Korean Patent Application No. 2005-67066, filed Jul. 23, 2005, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     Aspects of the present invention relate to a cartridge for an image forming apparatus, and more particularly, to a cartridge for an image forming apparatus having an improved supporting structure of a cleaning blade.  
         [0004]     2. Description of the Related Art  
         [0005]     A cartridge for an image forming apparatus according to one aspect of the present invention includes a device used when installed in an electrophotographic image forming apparatus, such as a laser beam printer, a multi-function laser printer, a copier, a scanner, a fax machine, etc., and hereinafter is referred to as a cartridge.  
         [0006]      FIG. 1  shows the schematic structure of a conventional cartridge  100 . The cartridge  100  comprises a photosensitive drum  110  on which a latent image is formed, a developing roller  120  which develops a toner image on the latent image formed on the photosensitive drum  110 , and supplying rollers  130  which supply toner to the developing roller  120 . The latent image on the photosensitive drum  110  is formed through light scanned by a laser scanning unit  10  which is provided in the image forming apparatus.  
         [0007]     The cartridge  100  further comprises a cleaning blade  140  which has an elastic plate for cleaning the surface of the photosensitive drum  110 , and a charging roller  160  which charges the surface of the photosensitive drum  110  cleaned by the cleaning blade  14  to a predetermined voltage.  
         [0008]     The cleaning blade  140  makes contact with the outer rounded surface of the photosensitive drum  110  with a predetermined pressure and removes toner remaining on the surface of the photosensitive drum  110  while the photosensitive drum  110  is rotating. The cleaning blade  140  is supported by a bracket  150  and fixed to a casing (not shown) of the cartridge  100  by fixing parts  151 , which are formed at opposite end parts of the bracket  150 .  
         [0009]      FIG. 2  shows the forces acting on the cleaning blade  140  and the bracket  150  used in the prior art. In  FIG. 2 , F A  and F B  respectively represent a horizontal force and a vertical force loaded on the cleaning blade  140  by the photosensitive drum  110  in  FIG. 1 . Also, R A  and R B  represent reaction forces generated on the bracket  150  by the casing of the cartridge  100  and correspond to the magnitudes of F A  and F B , respectively.  
         [0010]     F A  and F B , which are loaded on the cleaning blade  140  by the photosensitive drum  110 , are transferred to the bracket  150  through contact surface A and then to the casing of the cartridge  100  through the fixing parts  151  of the bracket  150 . As a result, during the course of normal operation, the contact surface A is subject to a tensile stress, a compressive stress and a shear stress.  
         [0011]      FIG. 3  is a plan view showing an equilibrium state between the horizontal forces FA and RA loaded on the cleaning blade  140  and the bracket  150  used in the prior art. FA, loaded on the cleaning blade  140  by the photosensitive drum  110 , may be represented as a distributed load q[kgf/mm]. In  FIG. 3 , reference character I represents the length of the photosensitive drum  110  along its axis. A reaction force of the distributed load q corresponds to RA which acts through the fixing parts  151  of the bracket  150  as a pair of divided forces R 1  and R 2  acting at opposite end parts of the bracket  150 .  
         [0012]     Due to the uneven distribution of the reaction force, the cleaning blade  140  and especially the bracket  150  are elastically deformed to approximately the shape of the dotted line in  FIG. 3 . As a result of this deformation, the outer surface of the photosensitive drum  110  is not uniformly cleaned, and the central area of the outer surface of the photosensitive drum  110  may not be properly cleaned.  
         [0013]     In addition to the problem of not properly cleaning the photosensitive drum, prior art cartridges also encounter the problem that the cleaning blade breaks apart from the bracket. As shown in  FIG. 2 , the vertical force FB acting on the cleaning blade  140  is supported by the shear stress acting on the contact surface A between the bracket  150  and the cleaning blade  140 . However, the cleaning blade  140  often becomes detached from the bracket  150  because of the repetitive acting of FB and the limit of the stress which contact surface A can sustain.  
       SUMMARY OF THE INVENTION  
       [0014]     Accordingly, it is an aspect of the present invention to provide a cartridge for an image forming apparatus having a cleaning blade and a bracket which prevent poor quality cleaning of the surface of a photosensitive drum. It is another aspect of the present invention to provide a cartridge for an image forming apparatus having a cleaning blade and a bracket with improved durability.  
         [0015]     Additional aspects and/or advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the present invention.  
         [0016]     The foregoing and/or other aspects of the present invention are also achieved by providing an image forming apparatus comprising a rotating photosensitive drum, a cleaning blade having a cleaning edge part which makes contact with an outer surface of the photosensitive drum along an axial direction of the photosensitive drum, and a bracket having a contact surface where the bracket makes contact with the cleaning blade to support the cleaning blade, wherein the width of the contact surface between the bracket and the cleaning blade is at a maximum at the center part of the cleaning blade and gradually decreases from the center part to opposite end sides of the cleaning blade.  
         [0017]     According to another embodiment of the present invention, a lower edge part of the cleaning blade making contact with the bracket extends to a surface of the bracket so that the lower edge part of the cleaning blade is at a maximum at the center part of the cleaning blade and gradually decreases from the center part to opposite end sides of the cleaning blade.  
         [0018]     According to another embodiment of the present invention, the lower edge part of the cleaning blade comprises a round part.  
         [0019]     According to another embodiment of the present invention, the round part of the cleaning blade is symmetrical.  
         [0020]     According to another embodiment of the present invention, the upper edge part of the cleaning blade extends to a surface of the bracket so that the upper edge part of the cleaning blade is at a maximum at the center part of the cleaning blade and gradually decreases from the center part to the opposite end sides of the cleaning blade.  
         [0021]     According to another embodiment of the present invention, the upper edge part of the cleaning blade comprises a round part.  
         [0022]     According to another embodiment of the present invention, the round part of the cleaning blade is symmetrical.  
         [0023]     The foregoing and/or other aspects of the present invention are also achieved by providing an image forming apparatus comprising a rotating photosensitive drum, a cleaning blade having a cleaning edge part which makes contact with an outer surface of the photosensitive drum along an axial direction of the photosensitive drum, a bracket having a contact surface where the bracket makes contact with the cleaning blade to support the cleaning blade, and a free end of the cleaning blade which protrudes from the bracket and contacts with the photosensitive drum, the contact surface being at a maximum at the center part of the cleaning blade and gradually decreasing from the center part to opposite end sides of the cleaning blade. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]     These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:  
         [0025]      FIG. 1  is a schematic side view showing the structure of a conventional cartridge for an image forming apparatus;  
         [0026]      FIG. 2  is a magnified view of the cleaning blade and the bracket in  FIG. 1 ;  
         [0027]      FIG. 3  is a plan view showing forces acting on the cleaning blade and the bracket in FIG.  2 ;  
         [0028]      FIG. 4  is a cross sectional view of a cartridge for an image forming apparatus according to an embodiment of the present invention;  
         [0029]      FIG. 5  is a schematic view of the cleaning blade and the bracket in  FIG. 4 , seen at side A;  
         [0030]      FIG. 6  is a plan view showing forces acting on the cleaning blade and the bracket in  FIG. 4 ; and  
         [0031]      FIG. 7  is a schematic view of the cleaning blade and the bracket in  FIG. 4 , seen at side B. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0032]     Reference will now be made in detail to the present embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures.  
         [0033]     As shown in  FIG. 4 , a cartridge  200  for an image forming apparatus according to an embodiment of the present invention comprises a photosensitive drum  210 , a developing roller  220 , a supplying roller  230  and a charging roller  260 . The photosensitive drum  210  and the rollers  220 ,  230  and  260  are similar to those of the conventional cartridge, and detailed descriptions thereof will be omitted. Toner used for developing an image is stored in the storing part  201 . The toner is developed to the electrostatic latent image formed on the surface of the photosensitive drum  210  through the supplying roller  230  and the developing roller  220 .  
         [0034]     The cartridge  200  further comprises a cleaning blade  240  which has an elastic plate for cleaning the surface of the photosensitive drum  210  and a bracket  250  having a contact surface where the bracket  250  makes contact with the cleaning blade  240  to support the cleaning blade  240 . The bracket  250  is fixed to a casing  202  through fixing parts  251 .  
         [0035]     The cleaning blade  240  comprises a cleaning edge  241  at its lower end. The cleaning edge  241  makes contact with the outer round surface of the photosensitive drum  210  so that the cleaning edge  241  can remove the toner remaining on the surface of the photosensitive drum  210  when the photosensitive drum  210  is rotated. The toner removed from the photosensitive drum  210  by the cleaning blade  240  is stored in a waste toner storing part  203 .  
         [0036]     The combination of the cleaning blade  240  and the bracket  250  is shown in  FIG. 5 .  
         [0037]      FIG. 5  shows the cleaning blade  240  and the bracket  250  when seen from “A” in  FIG. 4 . A lower edge part  252  of the bracket  250  which makes contact with the cleaning blade  240  comprises a downwardly convex round part. Accordingly, the contact surface of the bracket  250  where the bracket  250  makes contact with the cleaning blade  240  is enlarged by the convex round shape of the lower edge part  252 , in comparison to the contact surface of a conventional bracket.  
         [0038]     Because of the enlarged contact surface between the cleaning blade  240  and the bracket  250 , the shear stress acting on the contact surface is decreased and detachment of the cleaning blade  240  from the bracket  250  can be prevented.  
         [0039]     The contact surface between the cleaning blade  240  and the bracket  250  has a maximum width W at the center part of the cleaning blade  240  due to the rounded lower edge part  252  of the bracket  250 . The width W gradually decreases from the center part to the opposite sides and is at a minimum at the opposite end sides of the cleaning blade  240 .  
         [0040]     Considering that the elastic deformation of the cleaning blade  240  is at a maximum at its center due to the distributed load by the photosensitive drum  210 , the shape of the rounded lower edge part  252  is preferably symmetrical. However, the shape of the rounded lower edge part  252  does not have to be symmetrical. There are many different shapes that could be used in accordance with the present invention to prevent the elastic deformation of the cleaning blade  240 .  
         [0041]     Due to the shape of the lower edge part  252  of the bracket  250 , the width V between the lower edge part  252  and the lower edge of the cleaning edge  241  of the cleaning blade  240  is at a minimum at the center part of the cleaning blade  240  and at a maximum at the opposite end parts of the cleaning blade  240 .  
         [0042]     To compensate for the difference in the stress applied at the opposite end parts of the blade  240 , the lower edge part  252  of the bracket  250  may have not only a round shape but also a stepped shape from the center part to the opposite end parts. In this case, the width V between the cleaning edge  241  of the blade  240  and the lower edge part  252  of the bracket  250  is larger when getting closer to the opposite end parts of the blade  240  because of the stepped shape of the lower edge part  252 .  
         [0043]     Or, the width V may be formed according to the change of the curvature of the lower edge part  252  of the bracket  250 , where the curvature is smaller when getting closer to the opposite end parts of the lower edge part  252  compared to the center part of the lower edge part  252 . This embodiment would also reduce the shear stress acting on the contact surface between the cleaning blade  240  and the bracket  250 .  
         [0044]     The bracket  250  comprises the fixing parts  251  at opposite end parts to couple the bracket  250  with the casing  202 .  
         [0045]     According to the above coupling between the cleaning blade  240  and the bracket  250 , the amount of the elastic deformation at the center part of the cleaning edge  241  may be controlled to be the same amount of elastic deformation as the amount of elastic deformation at the opposite end parts of the cleaning edges  241  when the horizontal force FA is loaded on the cleaning blade  240 . Thus, as a result of this uniform elastic deformation, the toner remaining on the photosensitive drum  210  may be uniformly removed regardless of its positioning at the center part or at the end parts.  
         [0046]     Because of the shape of the lower edge part  252  of the bracket  250 , the distributed load which acts on the cleaning edge  241  by the rotating photosensitive drum  210  is shown as a curved line  2  in  FIG. 6 . According to the curved line  2 , the maximum load is at the center part of the cleaning edge  241 , and the minimum loads are at the opposite end parts of the cleaning edge  241 . It can be inferred that the shape of the above load distribution is similar to the shape of the lower edge part  252 .  
         [0047]     A dotted straight line  1  in  FIG. 6  represents the shape of the cleaning blade and bracket after the uniformly distributed load q acts on the cleaning blade ( 240  in  FIG. 4 ) and the bracket ( 250  in  FIG. 4 ) of the present invention. This uniform distribution of q results in a substantial decrease in the elastic deformation of the cleaning blade  240  and bracket  250  of the present invention.  
         [0048]     The vertical force (similar to FB in  FIG. 2 ) acting on the cleaning blade  240  is supported by the contact surface between the bracket  250  and the cleaning blade  240  which is enlarged by the lower edge part  252  of the bracket  250 , so that the shear stress acting on the contact surface is decreased to prevent the detachment between the cleaning blade  240  and the bracket  250 .  
         [0049]     The drawings in the description of the present invention are simplified through modeling for the illustration of the present invention However, the divided forces R 1  and R 2  may be distributed in a larger area. Therefore, the exact width V of the blade  240  may be optimized through experiments and calculations according to specific products.  
         [0050]     To enlarge the contact surface between the cleaning blade  240  and the bracket  250 , an upper edge part  242  of the cleaning blade  240  may be extended to have a round part, which is shown in  FIG. 7 .  FIG. 7  shows the cleaning blade  240  and the bracket  250  combined with each other when seen from “B” in  FIG. 4 .  
         [0051]     In this case, the contact surface between the cleaning blade  240  and the bracket  250  has a width U which is at a maximum at the center part of the cleaning blade  240  due to the round upper edge part  242  of the cleaning blade  240 . The width U decreases from the center part to the opposite sides, and is at a minimum at the opposite end parts of the cleaning blade  240 .  
         [0052]     The upper edge part  242  of the cleaning blade  240  in  FIG. 7  may be used in combination with the lower edge part  252  of the bracket  250  in  FIG. 5  to further increase the effectiveness of the present invention.  
         [0053]     In the above embodiment, the lower edge part  252  of the bracket  250  and the upper edge part  242  of the cleaning blade  240  are not limited to having round edges. They may also have stepped shapes.  
         [0054]     Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.