Patent Publication Number: US-8995872-B2

Title: Developing device provided with developing roller and thickness regulating blade

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority from Japanese Patent Application No. 2011-077200 filed Mar. 31, 2011. The entire content of this priority application is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to a developing device provided with a developing roller and a thickness regulating blade for regulating a thickness of developing agent deposited on the developing roller. 
     BACKGROUND 
     A conventional developing device includes a casing, a developing roller carrying developing agent thereon, a thickness regulating blade slidingly contacting the developing roller and regulating a thickness of the developing agent carried on the developing roller, and a plurality of seal members preventing the developing agent from leaking from a gap between the thickness regulating blade and the developing roller. The thickness regulating blade is provided with a press member in sliding contact with the developing roller. 
     The seal member includes an upper side seal located between the thickness regulating blade and the casing, and a blade side seal located at each width end of the press member. The upper side seal is configured to prevent a developing agent from leaking from a base portion of the thickness regulating blade. The blade side seal is configured to prevent the developing agent from leaking from a gap among the thickness regulating blade, the casing, and the developing roller. 
     SUMMARY 
     The conventional developing device includes a plurality of seal members, increasing manufacturing cost. 
     The seal member is disposed on a surface in confrontation with the casing of the thickness regulating blade, and provided at a position outside of both ends of the press member in a longitudinal direction of the press member. If a gap is accidentally generated among the press member, the seal member, and the developing roller, the developing agent leaks from the gap. 
     In view of the foregoing, it is an object of the invention to provide a developing device capable of reducing the number of a seal member for preventing a toner leakage and capable of providing the seal member without a gap when a press member is provided on a surface in confrontation with a casing of the developing device. 
     In order to attain the above and other objects, the invention provides a developing device. The developing device includes a casing, a developing roller, a thickness regulating blade, and a seal member. The casing accommodates developer therein. The developing roller is rotatably provided in the casing and has an outer peripheral surface carrying the developer. The thickness regulating blade is configured to regulate a thickness of the developer carried on the outer peripheral surface and has an opposed surface confronting the casing. The thickness regulating blade further has one end part supported on the casing and another end part provided with a press member in sliding contact with the outer peripheral surface. The press member is located on the opposed surface and protrudes toward the developing roller. The press member is formed with a receiving portion depressed inward at its widthwise ends in an axial direction of the developing roller. The seal member is disposed between the thickness regulating blade and the casing and contacting at least a part of the receiving portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The particular features and advantages of the invention as well as other objects will become apparent from the following description taken in connection with the accompanying drawings, in which: 
         FIG. 1  is a schematic cross-sectional view showing an overall structure of a color laser printer according to an embodiment of the invention; 
         FIG. 2  is an exploded perspective view of a developer cartridge from which a thickness regulating blade and a developing roller are removed; 
         FIG. 3  is a perspective view of the thickness regulating blade as viewed from reverse side; 
         FIG. 4(   a ) is an enlarged perspective view of a left end portion of the thickness regulating blade; 
         FIG. 4(   b ) is an enlarged bottom view of the left end portion of the thickness regulating blade; 
         FIG. 5(   a ) is a partial cross-sectional view taken along a line V-V in  FIG. 2 ; 
         FIG. 5(   b ) is an enlarged cross-sectional view of a press member; 
         FIG. 6(   a ) is an enlarged perspective view of the left end portion of a thickness regulating blade according to a modification of the embodiment; and 
         FIG. 6(   b ) is an enlarged bottom view of the left end portion of the thickness regulating blade according to the modification of the embodiment; 
     
    
    
     DETAILED DESCRIPTION 
     An embodiment of the invention will be described while referring to the accompanying drawings. An overall structure of a color laser printer  1  in which a developing device according to the present invention is mounted will be briefly described, and after that technical features of the present embodiment will be described in detail. 
     Throughout the specification, the expressions “front”, “rear”, “above”, “below”, and “laterally” are used herein to define the various parts when the color laser printer  1  is disposed in an orientation in which it is intended to be used. For example, a left side in  FIG. 1  is a front side with respect to a user, a right side in  FIG. 1  is a rear side, a front side of  FIG. 1  is a right side, and a back side of  FIG. 1  is a left side. 
     [Overall Structure of Color Laser Printer] 
     The color laser printer  1  has a main body  2  in which provided are a sheet supply section  20  for supplying a sheet S, an image forming section  30  for forming an image on the sheet S, and a sheet discharging section  90  for discharging the sheet S carrying a color image thereon. 
     The main body  2  has an upper portion formed with an opening  2 A and an upper cover  3  pivotally supported thereon for exposing and closing the opening  2 A. The upper cover  3  has a top surface serving as a discharge tray  4  on which the discharged sheet S from the main body  2  is stacked. 
     The sheet supply section  20  disposed at a bottom portion of the main body  2  includes a sheet supply tray  21  detachably mounted to the main body  2 , a sheet supplying mechanism  22  for conveying the sheet S from the sheet supply tray  21  to the image forming section  30 . The sheet supplying mechanism  22  is disposed at a front portion of the sheet supply tray  21  and includes a sheet supply roller  23 , a separation roller  24 , a separation pad  25 , a paper dust roller  26 , and a pinch roller  27 . 
     In the sheet supply section  20 , the sheet S stacked on the sheet supply tray  21  is fed upward one by one, passes between the paper dust roller  26  and the pinch roller  27  so that the paper dust is removed therefrom, follows a U-shaped path through a conveying path (not shown), and supplied to the image forming section  30 . 
     The image forming section  30  mainly includes four LED (light emitting diode) units  40 , four process cartridges  50 , a transfer unit  70 , and a fixing unit  80 . 
     The LED unit  40  is pivotably connected to an LED supporting member (not shown) disposed below the upper cover  3  and is arbitrarily fixed to a fixing member (not shown) provided on the main body  2 . 
     The four process cartridges  50  are juxtaposed in a front/rear direction at a position between the upper cover  3  and the sheet supply section  20 , and includes a drum cartridge  58  and a developer cartridge  56  detachably mounted to the drum cartridge  58 . 
     The drum cartridge  58  includes a photosensitive drum  51  and a charger  52 . The drum cartridge  58  may be either detachably mounted to the main body  2  or fixedly provided in the main body  2 . 
     The developer cartridge  56  includes a casing  200  ( FIG. 2 ) defining a toner accommodating chamber  55  for accommodating toner, a developing roller  53 , a supply roller  54 , and a thickness regulating blade  100 . 
     The four developer cartridges  56 K,  56 Y,  56 M, and  56 C respectively accommodate black (K), yellow (Y), magenta (M), and cyan (C) toner. These cartridges are arranged in the stated order from an upstream side in a sheet feeding direction. 
     The transfer unit  70  is disposed between the sheet supply section  20  and the process cartridge  50  and includes a drive roller  71 , a follower roller  72 , an endless transfer belt  73 , and a transfer roller  74 . 
     The drive roller  71  and the follower roller  72  are arranged in parallel with and away from each other in the front/rear direction. The transfer belt  73  is stretched between the drive roller  71  and the follower roller  72  and has an outer surface in contact with each photosensitive drum  51 . Four transfer rollers  74  are disposed inside the transfer belt  73  and confronts corresponding photosensitive drum  51 , with the transfer belt  73  interposed therebetween. A transfer bias (transfer voltage) opposite in polarity to the toner is applied to the transfer roller  74  under a constant current control during a transfer operation. 
     The fixing unit  80  is disposed on the rear side of the process cartridge  50  and the transfer unit  70 . The fixing unit  80  includes a heating roller  81  and a pressure roller  82  facing the heating roller  81  and applying a pressure to the same. 
     The sheet discharging section  90  includes a sheet discharge path  91  running upward from the fixing unit  80  and turning forward, and a plurality of conveying rollers  92  conveying the sheet S. 
     In a color print mode, an outer surface of each of the photosensitive drums  51  is charged by the charger  52  and exposed by the LED unit  40 , so that the potential level of the exposed portion becomes lower than the remaining portion on the outer surface, thereby forming an electrostatic latent image on the photosensitive drum  51  based on image data. The toner accommodated in the toner accommodating chamber  55  is supplied to the developing roller  53  by the supply roller  54 , regulated to a prescribed uniform thickness by the thickness regulating blade  100 , and then deposited on the developing roller  53 . 
     The toner carried on the developing roller  53  is supplied to the electrostatic latent image formed on the photosensitive drum  51 . As a result, the electrostatic latent image is developed into a visible toner image. 
     The sheet S supplied on the transfer belt  73  passes between each photosensitive drum  51  and each transfer roller  74  located within the transfer belt  73 , transferring the toner image formed on the photosensitive drum  51  onto the sheet S. The sheet S passes between the heating roller  81  and the pressure roller  82 , so that the toner image transferred onto the sheet S is thermally fixed. 
     The sheet S with thermally fixed toner image is conveyed through the sheet discharge path  91  by the conveying rollers  92 , discharged outside of the main body  2 , and stacked on the discharge tray  4 . 
     [Developer Cartridge] 
     Next, the detailed construction of the developer cartridge  56  will be described. A direction will be used throughout the following description assuming that the developer cartridge  56  is transversely disposed. That is, as shown in  FIG. 2 , a side to which the thickness regulating blade  100  is mounted as viewed from the casing  200  defines “upward”, and the opposite side “downward”. A side at which the developing roller  53  is disposed with respect to the casing  200  defines “rear”, and the opposite side defines “front”. Based on the upward/downward direction and the front/rear direction, “right” and “left” are defined. 
     As shown in  FIG. 2 , the casing  200  has a rear side wall formed with an elongated opening  201 . The developing roller  53  is rotatably supported on the casing  200  so as to cover the opening  201 . The opening  201  has a lower portion provided with a film  210  and widthwise end portions provided with a side seal  220 . A mounting surface  202  to which the thickness regulating blade  100  is to be mounted is disposed above the opening  201 . 
     The side seal  220  is curved to follow a circumferential surface of the developing roller  53  and is in sliding contact with the developing roller  53 . The film  210  is in sliding contact with a lower portion of the developing roller  53 , and the thickness regulating blade  100  is in sliding contact with the upper portion of the developing roller  53 . The developing roller  53  is surrounded by the thickness regulating blade  100 , the film  210 , and the side seal  220  in the upward/downward and rightward/leftward directions, thereby preventing the toner in the casing  200  from leaking from the shielded portion of the developing roller  53 . 
     The thickness regulating blade  100  slidingly contacts the developing roller  53  to regulate a thickness of the toner thereon. The thickness regulating blade  100  has a base part fixed to the mounting surface  202  and a free end part in sliding contact with the developing roller  53 . As shown in  FIG. 3 , the thickness regulating blade  100  is configured of a metallic plate  110  and a reinforcing member  140 . 
     The metallic plate  110  is in contact with the developing roller  53  and made of substantially thin rectangular metallic plate. The metallic plate  110  has an opposed surface  110 A facing the casing  200  provided with a press member  120  and a seal member  130 . 
     The press member  120  is formed of a rubber or the like and in sliding contact with the circumferential surface of the developing roller  53 . The press member  120  protrudes from the free end part of the thickness regulating blade  100  toward the developing roller  53 . Specifically, as shown in  FIG. 4(   a ), the press member  120  has a semicircular cross-section and extends from one widthwise end of the developing roller  53  to the other in an axial direction of the developing roller  53 . The press member  120  has a contact part N in direct sliding contact with the developing roller  53 . The contact part N is disposed furthest from the metallic plate  110  on the press member  120  in top-to-bottom direction and extends in the axial direction. 
     The press member  120  has widthwise ends portion formed with a concave part  121  positioned at a front side (upstream side in a rotational direction of the developing roller  53 , shown in arrow A of  FIG. 4(   b )) and depressed rearward (downstream side in the rotational direction of the developing roller  53 ). The concave part  121  is of substantially squared U-shape and includes a first side surface  122 , a depth-side surface  123 , and a second side surface  124 . 
     The first side surface  122  extends in front/rear direction (rotational direction of the developing roller  53 ). The depth-side surface  123  extends in the axial direction from a rear end portion (the most downstream side in the rotational direction of the developing roller  53 ) of the first side surface  122 . As shown in  FIG. 5(   b ), the depth-side surface  123  extends orthogonal to the opposed surface  110 A of the metallic plate  110 . The depth-side surface  123  is aligned with the contact part N as shown in a hatching area of  FIG. 4(   b ). The second side surface  124  extends from an outside end portion of the depth-side surface  123  toward the upstream side in the rotational direction of the developing roller  53  so as to be in confrontation with the first side surface  122 . 
     The seal member  130  is made of a sponge or the like. The seal member  130  has a thickness greater than that of the press member  120  before the thickness regulating blade  100  is assembled in the casing  200 , whereas the seal member  130  has a thickness equivalent to the press member  120  due to the elastic deformation after the thickness regulating blade  100  is assembled in the casing  200 . 
     The seal member  130  includes, as shown in  FIG. 3 , a main part  131  positioned at the base part of the metallic plate  110  and extending in the axial direction, and a side part  132  connected to widthwise end of the main part  131  and extending toward the concave part  121  of the press member  120 . The side part  132  has a rear end portion fitted into the concave part  121  so as to be sandwiched between the first side surface  122  and the second side surface  124  and in contact with the first side surface  122 , the depth-side surface  123 , and the second side surface  124 . As shown in  FIG. 5(   a ), the rear end portion of the side part  132  is closely in contact with an end surface of the side seal  220  at the downstream side in the rotational direction of the developing roller  53  in order to avoid toner leakage from a gap which may be formed by the side seal  220 , the side part  132 , and the developing roller  53 . 
     The seal member  130  provides hermetically seals between the thickness regulating blade  100  and the mounting surface  202 , and between the thickness regulating blade  100  and the developing roller  53 , which prevents the toner leakage from these gaps. 
     If the seal member  130  were provided at downstream side in the rotational direction of the developing roller  53  from the contact part N, the toner may leak from a gap accidentally formed by the press member  120 , the seal member  130 , and the developing roller  53 . On the other hand, in the embodiment, the depth-side surface  123  of the concave part  121  positioned most downstream side in the rotational direction of the developing roller  53  is aligned with the contact part N in the rotational direction of the developing roller  53 . The contact part N extends over the entire width of the thickness regulating blade  100  in the axial direction. Thus, even if the gap is accidentally formed by the press member  120 , the seal member  130 , and the developing roller  53 , the contact part N blocks the toner which may leak to the downstream side in the rotational direction of the developing roller  53  through the formed gap. 
     The reinforcing member  140  extends in the rightward/leftward direction and located at an opposite side of the opposed surface  110 A of the metallic plate  110  where the press member  120  is provided, as shown in  FIG. 2 . The reinforcing member  140  sandwiches the metallic plate  110  in cooperation with the casing  200  in order to reinforce the metallic plate  110 . Providing the reinforcing member  140  on the opposed surface  110 A in this way prevents the deformation of the metallic plate  110 , provides the base part of the metallic plate  110 , and uniforms a contact pressure between the developing roller  53  and the metallic plate  110 . 
     As shown in  FIG. 3 , the metallic plate  110  is formed with a through hole  111  located at a position outside of an area surrounded by the press member  120  and the seal member  130 . The reinforcing member  140  is also formed with a through hole  141  located at a position corresponding to the through hole  111 . The through holes  111  and  141  respectively penetrate the metallic plate  110  and the reinforcing member  140  in a thickness direction thereof. As shown in  FIG. 2 , a screw  150  passes through the through holes  111  and  141  to fix the thickness regulating blade  100  to the mounting surface  202  of the casing  200 . 
     With the metallic plate  110  having this construction, as shown in  FIGS. 2 and 5(   a ), the metallic plate  110  is fixed to the mounting surface  202  of the casing  200 , and sandwiched by the mounting surface  202  and the reinforcing member  140 . The press member  120  located at the rear end portion of the metallic plate  110  is in sliding contact with the circumferential surface of the developing roller  53  while being urged by the metallic plate  110 . 
     Advantageous effects of the embodiment will be described. Because the single seal member  130  seals between the thickness regulating blade  100  and the casing  200 , and between the thickness regulating blade  100  and the developing roller  53 , the manufacturing cost can be reduced in comparison with a case where a plurality of seal members is provided. 
     Further, because the seal member  130  is in contact with the concave part  121  of the press member  120  provided on the opposed surface  110 A in confrontation with the casing  200 , the seal member  130  can be provided without a gap. 
     Further, because the seal member  130  is in facial contact with the concave part  121 , the contact part N providing a direct contact between the developing roller  53  and the press member  120  can be defined continuously from one widthwise end of the thickness regulating blade  100  to the other in the axial direction of developing roller  53 . In the embodiment, even if a gap is accidentally formed by the press member  120 , the side part  132 , and the developing roller  53 , the contact part N blocks the toner which may leak from the gap, compared with a case where the side part  132  is located at the outside of the press member  120  in the axial direction without the concave part  121 . 
     The rear end part of the side part  132  is in facial contact with the depth-side surface  123  of the concave part  121 , which prevents the toner from leaking via a gap between the seal member  130  and the depth-side surface  123 . 
     Because the depth-side surface  123  of the concave part  121  vertically extends relative to the opposed surface  110 A on which the press member  120  is provided, the rear end part of the side part  132  can easily contact the depth-side surface  123  without gap. 
     The side part  132  of the seal member  130  is in also facial contact with the first side surface  122 , which reliably prevents the toner from leaking from the gap between the seal member  130  and the concave part  121 . 
     Because the side part  132  of the seal member  130  is sandwiched between the first side surface  122  and the second side surface  124 , the toner leakage from the gap between the seal member  130  and the concave part  121  can be reliably obviated, and the seal member  130  can be easily positioned relative to the press member  120 . 
     While the invention has been described in detail with reference to the embodiment 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 of the invention. 
     In the above-described embodiment, the side part  132  of the seal member  130  is in contact with the first side surface  122 , the depth-side surface  123 , and the second side surface  124 . However, the present invention is not limited to this configuration. The side part  132  may be in contact with at least a part of the concave part  121 . For example, the side part  132  may be in contact with only the depth-side surface  123  of the concave part  121 . This prevents toner leakage from the gap between the concave part  121  and the seal member  130 . 
     Although, the concave part  121  is of substantially squared U-shape in the above-described embodiment, the present invention is not limited to this configuration. For example, as shown in  FIGS. 6(   a ) and  6 ( b ), the press member  120  may be cut out so as to be formed with the concave part  121  having substantially L-shape without the second side surface  124 . In this modification, a rear end part of the side part  132  is in contact with the first side surface  122  and the depth-side surface  123 . Since the concave part  121  is formed in L-shape, the seal member  130  can be easily attached to the metallic plate  110  compared with the above-described embodiment. 
     Although the color laser printer  1  is employed as an image forming device, the present invention is applicable to a multifunction device or a copying device can be available.