Patent Publication Number: US-8121514-B2

Title: Developing device and image forming apparatus employing the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under Korean Patent Application No. 10-2009-0060838, filed on Jul. 3, 2009, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
     BACKGROUND 
     1. Field of the Invention 
     One or more embodiments of the present general inventive concept relate to a developing device and an electrophotographic image forming apparatus employing the development device. 
     2. Description of the Related Art 
     Electrophotographic image forming apparatuses print an image on a recording medium by irradiating light, which is modulated to correspond to image information, onto a photoconductor in order to form an electrostatic latent image on a surface of the photoconductor, supplying toner to the electrostatic latent image in order to develop the electrostatic latent image into a visible toner image, and then, transferring and fixing the toner image onto the recording medium. Electrophotographic image forming apparatuses include a developing device containing toner. 
     The photoconductor and the toner may be provided via a cartridge which may be referred to as a ‘developing device’. When the toner contained in the developing device is completely consumed, the developing device is removed from the electrophotographic image forming apparatus, and a new developing device is inserted into the electrophotographic image forming apparatus. 
     A developing device may be divided into a toner container and a developing unit. Before the developing device is inserted into an image forming apparatus, the toner container and the developing unit are isolated from each other by disposing a blocking film therebetween. The blocking film is removed in order to connect the toner container and the developing unit with each other before the developing device is inserted into the image forming apparatus. When the toner container is not completely isolated from the developing unit, toner may leak to the developing unit during delivery of the developing device. If toner leaks to the developing unit, it may be difficult to remove the blocking film. 
     SUMMARY 
     One or more embodiments of the present general inventive concept provide a developing device in which toner contained in a toner container is prevented from leaking to the developing unit, and an electrophotographic image forming apparatus employing the same. 
     One or more embodiments of the present general inventive concept also provide a developing device in which a blocking film disposed between a toner container and a developing unit is easily removed, and an electrophotographic image forming apparatus employing the same. 
     Additional aspects and utilities of the present general inventive concept 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 general inventive concept. 
     Features and/or utilities of the present general inventive concept may be realized by a developing device including a housing including a toner container containing toner, and a developing unit, wherein the developing unit includes a developing roller and a photoconductive drum; a barrier member including a toner supply window, wherein the barrier member is combined with the housing to separate the toner container and the developing unit from each other; and a blocking film that is attached to the barrier member to block the toner supply window, wherein an end of the blocking film is exposed outside the housing through an opening formed in a sidewall of the housing, wherein a bottom surface and first and second side surfaces of the barrier member are attached to a bottom surface and first and second side surfaces of the housing by using a welding process, and a distance between the first and second side surfaces of the barrier member and a distance between the first and second side surfaces of the housing increase from bottom to top. 
     The first and second side surfaces of the barrier member may be disposed at an angle of about 75 to about 81 degrees with respect to a horizontal plane. 
     The developing device may further include a plurality of fusion protrusions protruding from the bottom surface and the first and second side surfaces of the barrier member, and fusion grooves formed in the bottom surface and the first and second side surfaces of the housing, into which the plurality of fusion protrusions are inserted. An overlapping distance, constituting a measure of how much the fusion protrusions overlap the fusion grooves, respectively, may be about 0.3 to about 0.5 mm. 
     The blocking film may be attached to an attachment surface of the barrier member, the attachment surface facing the developing unit. 
     A lower end of the toner supply window may be disposed to be higher than a bottom surface of the developing unit. The developing unit may include a supply roller attaching toner to the developing roller, and the lower end of the toner supply window may be disposed to be higher than a center of the supply roller. 
     The barrier member may include a reinforcing rib having a multi-rib structure, the reinforcing rib being disposed on an upper portion of the toner supply window. 
     The barrier member may include a plurality of window reinforcement ribs crossing the toner supply window, wherein each of the window reinforcement ribs may be disposed such that an upper surface of each of the window reinforcement ribs is lower than the attachment surface, thereby forming a step between each of the window reinforcement ribs and the attachment surface. 
     A lower end of the opening may be disposed to be higher than a lower end of the toner supply window. 
     The developing device may include an elastic sealing unit that is combined with the sidewall of the housing in which the opening is formed, to cover the opening. A length of the sealing unit may be greater than a length of the opening. The developing device may further include a pressurizing unit pressing the sealing unit toward the sidewall of the housing. The housing may include a lower frame forming a lower frame of both the toner container and the developing unit; a receiving frame receiving remnant toner removed from the photoconductive drum; and a side frame that is combined with side surfaces of the lower frame and the receiving frame to connect the lower frame and the receiving frame, wherein the pressurizing unit is disposed at the side frame. 
     The housing may include a lower frame forming a lower structure of both the toner container and the developing unit; and an upper frame covering an upper portion of the lower frame, wherein a front end of the upper frame is fused with a top surface of the barrier member. A location at which the bottom surface of the barrier member is fused with the lower frame may be disposed closer to the toner container than a location at which the top surface of the barrier member is fused with the front end of the upper frame. 
     Features and/or utilities of the present general inventive concept may also be realized by an electrophotographic image forming apparatus including the developing device described above, an optical scanning unit scanning light, which is modulated according to an image signal, onto the photoconductive drum; a transfer device transferring a toner image formed on the photoconductive drum onto a recording medium; and a fixing unit fixing the toner image to the recording medium by applying heat and pressure to the recording medium. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features and advantages of the present general inventive concept will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which: 
         FIG. 1  is a schematic view showing the configuration of a developing device according to an embodiment of the present general inventive concept; 
         FIG. 2  is a perspective view of the developing device of  FIG. 1 ; 
         FIG. 3  is an exploded view illustrating how a lower frame, a barrier member, and an upper frame included in the developing device of  FIG. 1  are combined with one another, according to an embodiment of the present general inventive concept; 
         FIG. 4  is a perspective view of a barrier member included in the developing device of  FIG. 1 , according to an embodiment of the present general inventive concept; 
         FIG. 5  is a cross-sectional view taken along a line A-A′ of  FIG. 4 , according to an embodiment of the present general inventive concept; 
         FIG. 6  is a front view of the barrier member included in the developing device of  FIG. 1 , according to an embodiment of the present general inventive concept; 
         FIG. 7  is a front view for describing a process of fusing the barrier member of  FIG. 1  with a lower frame; 
         FIG. 8  is a cross-sectional view taken along a line B-B′ of  FIG. 4 , according to an embodiment of the present general inventive concept; 
         FIG. 9  is a plan view for describing how a blocking film included in the developing device of  FIG. 1  is removed, according to an embodiment of the present general inventive concept; 
         FIG. 10  is a diagram illustrating in detail a region E of  FIG. 1 , according to an embodiment of the present general inventive concept; 
         FIG. 11  is a front view illustrating the location of a plurality of toner supply windows and a opening via which an end of the blocking film is exposed to the outside, according to an embodiment of the present general inventive concept; 
         FIG. 12  is an exploded perspective view of a sealing unit that blocks the opening via which an end of the blocking film is exposed to the outside, according to an embodiment of the present general inventive concept; and 
         FIG. 13  is a schematic view showing the configuration of an electrophotographic image forming apparatus employing the developing device illustrated in  FIGS. 1 to 12 , according to an embodiment of the present general inventive concept. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Reference will now be made in detail to the embodiments of the present general inventive concept, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below to explain the present general inventive concept by referring to the figures. 
       FIG. 1  illustrates a configuration of a developing device  100  according to an embodiment of the present general inventive concept.  FIG. 2  is a perspective view of the developing device illustrated in  FIG. 1 . Referring to  FIGS. 1 and 2 , the developing device  100  according to the present embodiment includes a housing  101  in which a toner container  10  and a developing unit  20  are installed. The housing  101  may further include a waste toner container  30 . Toner that is to be used for a developing operation is contained in the toner container  10 . The toner container  10  and the developing unit  20  are separated by a barrier member  40 . A blocking film  50  is attached to the barrier member  40 . If an end of the blocking film  50  that is exposed via a side portion of the developing device  100  is pulled before the developing device  100  is used, then the blocking film  50  is separated from the barrier member  40 . When the blocking film  50  is completely removed, the toner container  10  and the developing unit  20  are connected, and thus the toner in the toner container  10  can be supplied to the developing unit  20 . 
     The developing unit  20  includes a photoconductive drum  1 , a charging roller  2 , and a developing roller  3 . The photoconductive drum  1  is manufactured by forming a photoconductive layer around an outer circumference of a cylindrical metal pipe. The charging roller  2  is an example of a charger that charges a surface of the photoconductive drum  1  to a uniform potential. A charging bias voltage is applied to the charging roller  2 . A corona charger (not shown) may be used instead of the charging roller  2 . The developing roller  3  supplies the toner from the toner container  10  to an electrostatic latent image formed on a surface of the photoconductive drum  1  in order to develop the electrostatic latent image. In the current embodiment, the developing device  100  employs a contact developing technique based on a principle that the developing roller  3  and the photoconductive drum  1  contact each other to form a developing nip D. In this case, the developing roller  3  may consist of an elastic layer (not shown) formed around an outer circumference of a conductive metal core (not shown). When a developing bias voltage is applied to the developing roller  3 , the toner is transferred and attached to the electrostatic latent image, which is formed on the surface of the photoconductive drum  1 , via the development nip D. If the developing device  100  employs a non-contact developing technique, a surface of the developing roller  3  and a surface of the photoconductive drum  1  are spaced about several hundreds of microns apart from each other. The development unit  20  may further include a supply roller  4  that attaches the toner supplied from the toner container  10  to the developing roller  3 . A supply bias voltage may be applied to the supply roller  4  so as to attach the toner to the developing roller  3 . Reference numeral  5  denotes a cleaning roller that removes foreign substances or toner attached to the charging roller  2 . Reference numeral  6  denotes a regulator that regulates an amount of toner that is attached to a surface of the developing roller  3  to be supplied to the development nip D. Reference numeral  7  denotes a cleaning unit that removes remnant toner and foreign substances from a surface of the photoconductive drum  1  before charging is performed. The remnant toner and foreign substances removed from the photoconductive drum  1  via the cleaning unit  7  are contained in the waste toner container  30 . 
     The toner container  10  may include an agitator  8  that supplies the toner to the development unit  20 . The agitator  8  may agitate the toner contained in the toner container  10  in order to charge the toner to a predetermined electric potential. Although  FIG. 1  illustrates two agitators  8 , the present general inventive concept is not limited thereto. In the toner container  10 , an appropriate number of agitators  8  may be installed at appropriate locations in order to effectively supply toner to the developing unit  20  in consideration of the capacity and shape of the toner container  10 . 
     Referring to  FIGS. 1 and 2 , the housing  101  of the developing device  100  may include a lower frame  60 , a receiving frame  70 , an upper frame  80 , and a cover  90 . The lower frame  60  forms a lower frame of both the toner container  10  and the developing unit  20 . The receiving frame  70  forms the waste toner container  30 . The upper frame  80  covers an upper part of the toner container  10 . The cover  90  covers an upper part of the developing unit  20 . The cover  90  has an optical window  9   a  through which light irradiated by an optical scanning unit  200  of  FIG. 13 , which will be described in detail later, is incident on the photoconductive drum  1 . A part of the photoconductive drum  1  is exposed to the outside via an aperture  9   b  formed in the bottom of the developing unit  20 . The lower frame  60  and the receiving frame  70  may be connected to each other via a side frame  95 . 
       FIG. 3  is an exploded view illustrating how the lower frame  60 , the barrier member  40 , and the upper frame  80  included in the developing device  100  are combined with one another, according to an embodiment of the present general inventive concept.  FIG. 4  is a perspective view of the barrier member  40  included in the developing device  100 , according to an embodiment of the present general inventive concept.  FIG. 5  is a cross-sectional view taken along a line A-A′ of  FIG. 4 , according to an embodiment of the present general inventive concept.  FIG. 6  is a front view of the barrier member  40  included in the developing device  100 , according to an embodiment of the present general inventive concept. 
     Referring to  FIGS. 3 and 4 , the blocking film  50  is attached to an attachment surface  421  of the barrier member  40 , and the barrier member  40  is combined with the lower frame  60 . The blocking film  50  blocks a toner supply window  411  of the barrier member  40 . The barrier member  40  may be combined with the lower frame  60  by performing an ultrasonic welding process on the barrier member  40 . To this end, as illustrated in  FIGS. 4 to 6 , a lower fusion protrusion  401  protrudes from a bottom surface  441  of the barrier member  40 , and first and second side fusion protrusions  402  and  403  protrude from first and second side surfaces  442  and  443  of the barrier member  40 , respectively. The lower fusion protrusion  401  extends along the bottom surface  441 . The first and second side fusion protrusions  402  and  403  extend along the first and second side surfaces  442  and  443  of the barrier member  40 , respectively. In the lower frame  60 , a lower fusion groove  601  is formed, into which the lower fusion protrusion  401  is inserted. First and second fusion grooves  602  and  603  are respectively formed in first and second sidewalls  61  and  62  of the lower frame  60 , into which the first and second fusion protrusions  402  and  403  are respectively inserted. 
     As indicated by dotted lines in  FIG. 7 , the barrier member  40  is disposed on the lower frame  60  such that the first and second side fusion protrusions  402  and  403  of the barrier member  40  are inserted into the first and second side fusion grooves  602  and  603 , respectively. Next, ultrasonic vibration is applied to the barrier member  40  while pressing a top surface  431  of the barrier member  40  with a fusion jig  901 . Then, the first side fusion protrusions  402  and  403  are temporarily melted within the first and second side fusion grooves  602  and  603 , and the barrier member  40  is moved downward along the first and second side fusion grooves  602  and  603 . When the lower fusion protrusion  401  is inserted into the lower fusion groove  601 , the lower fusion protrusion  401  is melted within the lower fusion groove  601 . When the application of the ultrasonic vibration is stopped, the lower fusion protrusion  401  and the first and second side fusion protrusions  402  and  403  that are melted are hardened to be attached to the lower and first and second side fusion grooves  601  to  603 . Thus, the barrier member  40  is combined with the lower frame  60 . In this case, an overlapping distance f 1 , f 2 , representing a measure of how much the first and second side fusion protrusions  402  and  403  and the lower fusion protrusion  401  overlap first and second side fusion grooves  602 ,  603  and the lower fusion groove  601 , respectively, may be between about 0.3 mm and about 0.5 mm. If the overlapping distance f is less than about 0.3 mm, then the barrier member  40  may not be firmly fused with the lower frame  60 . If the overlapping distance f is greater than about 0.5 mm, then the fusion protrusions  401  to  403  may not be fully placed within the fusion grooves  601  to  603 . The fusion jig  901  is used to press the top surface  431  of the barrier member  40 . In this case, if the first and second side surfaces  442  and  443  of the barrier member  40  are perpendicular to a horizontal plane, then pressure is not applied by the fusion jig  901  between the first and second side fusion protrusions  402  and  403  and the first and second side fusion grooves  602  and  603 , thereby preventing the barrier member  40  from being fused with the lower frame  60 . According to one embodiment, not only the first and second side surfaces  442  and  443  of the barrier member  40  but also first and second sidewalls  61  and  62  of the lower frame  60  are inclined with respect to the horizontal plane by an angle E. That is, the distance between the first and second side surfaces  442  and  443  of the barrier member  40  and the distance between the first and second sidewalls  61  and  62  of the lower frame  60  increase from bottom to top. The angle E may be appropriately determined but if the angle E approaches 90 degrees, then the pressure applied between the first and second side fusion protrusions  402  and  403  and the first and second side fusion grooves  602  and  603  by the fusion jig  901  is insufficient, thereby preventing the barrier member  40  from being fused with the lower frame  60 . Through experimentation, the maximum angle E that allows the barrier member  40  to be satisfactorily fused with the lower frame  60  was determined to be about 81 degrees. If the angle E is relatively small, the entire width of the developing device  100  should be increased in order to secure an effective supply width W of the plurality of toner supply windows  411  so that toner can be uniformly supplied to the entire surface of the developing unit  20 . Through experimentation, the lower limit of the minimum angle E that allows the barrier member  40  to be satisfactorily fused with the lower frame  60  while minimizing an increase in the entire width of the developing device  100 , was determined to be about 75 degrees. Accordingly, the angle E may range between about 75 degrees and about 81 degrees with respect to a horizontal plane. 
     As described above, the first and second side surfaces  442  and  443  of the barrier member  40  and the first and second sidewalls  61  and  62  of the lower frame  60  are determined to be inclined at the angle E with respect to a horizontal plane, thereby allowing the first and second side surfaces  442  and  443  of the barrier member  40  to be firmly fused with the first and second sidewalls  61  and  62  of the lower frame  60 . When the first and second side surfaces  442  and  443  of the barrier member  40  are firmly fused with the first and second sidewalls  61  and  62  of the lower frame  60 , it is possible to prevent the toner contained in the toner container  10  from leaking to the developing unit  20 . 
     During fusing of the barrier member  40  with the lower frame  60 , if the fusion jig  901  pressurizes the entire top surface  431  of the barrier member  40 , then the barrier member  40  may be deformed. If the barrier member  40  is deformed, a part of the blocking film  50  may be separated from the attachment surface  421  of the barrier member  40 . To prevent this, during the fusing operation, the fusion jig  901  applies pressure to only parts of the top surface  431  of the barrier member  40  that are adjacent to the first and second side surfaces  442  and  443  of the barrier member  40  instead of to the entire top surface  431  of the barrier member  40 , as illustrated in  FIG. 7 . In this case, in order to reinforce the strength of the barrier member  40 , the top surface  431  may further include an upper reinforcement rib  432 . The upper reinforcement rib  432  may have a multi-rib structure that extends along a length direction x of the top surface  431  of the barrier member  40  as illustrated in  FIGS. 4 and 5 . Where a length direction of the barrier member  40  is represented by a symbol “x” and a height direction is represented by a symbol “y,” the upper reinforcement rib  432  may extend from the planar surface of the barrier member  40  in a direction “z” perpendicular to the directions x and y. According to one embodiment, the upper reinforcement rib  432  has a double rib structure. Also, when first and second side surfaces  433  and  434  of the upper reinforcement rib  432  extend to the first and second side surfaces  442  and  443  of the barrier member  40 , the barrier member  40  may be further reinforced and is better equipped to withstand pressure applied thereto by the fusion jig  901 . 
     Referring to  FIG. 4 , the barrier member  40  includes the plurality of toner supply windows  411  for supplying the toner in the toner container  10  to the developing unit  20 . The toner supply window  411  is a through-hole extending along the length direction of the barrier member  40 . In order to prevent the plurality of toner supply windows  411  from deforming due to pressure applied by the fusion jig  901  during the fusing operation, a plurality of window reinforcement ribs  412  may be formed on the attachment surface  421  of the barrier member  40  crossing the toner supply window  411 . 
     Referring to  FIG. 8 , the blocking film  50  is placed on the attachment surface  421  of the barrier member  40  and is then heated in order to be attached to the barrier member  40 . In this case, when the blocking film  50  is attached to not only the barrier member  40  but also the window reinforcement ribs  412 , the blocking film  50  is securely attached to the barrier member  40  and thus cannot be easily separated from the barrier member  40 . Accordingly, as illustrated in  FIGS. 4 and 8 , it is possible to prevent the plurality of window reinforcement ribs  412  from being attached to the blocking film  50  by forming the plurality of window reinforcement ribs  412  such that the upper surfaces of the plurality of window reinforcement ribs  412  are lower than that of the attachment surface  421  to form a step between the plurality of window reinforcement ribs  412  and the attachment surface  421 . 
     Referring to  FIG. 3 , the first sidewall  61  of the lower frame  60  has an opening  610  through which an end of the blocking film  50  is exposed to the outside. 
     After the toner container  10  is filled with toner, the upper frame  80  is combined with the lower frame  60  and the barrier member  40 . The upper frame  80  may be combined with the lower frame  60  and the barrier member  40  according to the ultrasonic welding process is performed on the barrier member  40 . A plurality of fusion grooves (not shown) are formed at a bottom surface of the upper frame  80  to surround the toner container  10 . Also, a plurality of fusion protrusions (not shown) are formed on the lower frame  60  to surround the lower frame  60  except for a region where the barrier member  40  is located. The top surface  431  of the barrier member  40  includes an upper fusion groove  452  into which a fusion protrusion (not shown) at a front end of the upper frame  80  and protruding toward the developing unit  20  is inserted. A location at which the lower frame  60  is fused with the bottom surface  441  of the barrier member  40  is closer to the toner container  10  than a location at which the front end of the upper frame  80  is fused with the top surface  431  of the barrier member  40 . That is, the lower fusion protrusion  401  is closer to the toner container  10  than the upper fusion groove  452 . 
     When the lower frame  60  and the receiving frame  70  are combined via the side frame  95 , an end of the blocking film  50  is exposed to the outside via a slit  96  illustrated in  FIG. 12  of the side frame  95 . 
       FIG. 9  is a plan view for describing how the blocking film  50  of  FIG. 1  is removed, according to an embodiment of the present general inventive concept.  FIG. 10  is a diagram illustrating in detail a region E of  FIG. 1 , according to an embodiment of the present general inventive concept. Referring to  FIGS. 4 and 9 , the attachment surface  421  to which the blocking film  50  is attached is a part of the barrier member  40 , which faces the developing unit  20 . If the blocking film  50  is attached to a part of the barrier member  40 , which faces the toner container  10 , then the toner in the toner container  10  is drawn by a curved portion  51  of the blocking film  50  toward the opening  610 , thereby preventing the blocking film  50  from being easily removed. 
     In the developing unit  20 , a small amount of toner (which is referred to as “initial toner”) is contained in order to test the performance of the developing device  100  of  FIG. 1  after the developing device  100  is manufactured. If the initial toner is drawn by the curved portion  51  of the blocking film  50  toward the opening  610  when the blocking film  50  is removed, then the blocking film  50  may not be easily removed while being inserted into the opening  610 . That is, the initial toner is jammed between two folds of the blocking film  50  as marked by reference numeral  52  of  FIG. 9 , thereby preventing the blocking film  50  from being easily removed. In order to solve this problem, as illustrated in  FIG. 10 , a lower end  413  of each of the plurality of toner supply windows  411  is disposed to be higher than a bottom surface  21  of the developing unit  20 . The lower end  413  of each of the plurality of toner supply windows  411  is disposed to be higher than a center C of the supply roller  4  in order to reduce an extent to which the initial toner contacts the blocking film  50 . Accordingly, it is possible to reduce an amount of the initial toner drawn by the curved portion  51  toward the opening  610  when the blocking film  50  is removed and to prevent the blocking film  50  from being stuck due to the initial toner. 
     In other words, as illustrated in  FIG. 10 , a distance d 1  between a lower end of the supply window  411  and the bottom surface  21  of the developing unit  20  may be greater than a distance d 2  between the lower end of the supply window  411  and the lower end of the blocking film  50 . In addition, the distance d 3  in the vertical direction y between a center axis C of the supply roller  4  and the bottom surface  21  of the developing unit  20  may be less than a distance d 4  in the y direction between the lower end of the supply window  411  and the bottom surface  21  of the developing unit. 
       FIG. 11  is a front view illustrating the location of toner supply window  412  and the opening  610 , according to an embodiment of the present general inventive concept. Referring to  FIG. 11 , a lower end  611  of the opening  610  may be disposed to be higher than the lower end  413  of the toner supply window  411  of the barrier member  40 . In other words, a distance d 5  in a vertical direction y between the lower end of the opening  610  and the bottom surface  21  of the developing unit  20  may be greater than a distance d 6  between the lower end of the opening  610  and the lower end of the blocking film  50 . In this case, the blocking film  50  is removed while being inclined with respect to a horizontal plane including a horizontal direction x, thereby preventing the initial toner from being moved by the curved portion  51  toward the opening  610 . Even if a small amount of the initial toner is moved toward the opening  610 , the moved toner is contained in a space lower than the lower end  611  of the opening  610 , and thus, the blocking film  50  is not prevented from being removed due to the initial toner. 
       FIG. 12  is an exploded perspective view of a sealing unit  640  that blocks the opening  610 , according to an embodiment of the present general inventive concept. Referring to  FIG. 12 , the first sidewall  61  of the lower frame  60  of  FIG. 3  is combined with the sealing unit  640 . The sealing unit  640  may be attached to the first sidewall  61  of the lower frame  60  using double-sided tape. The double-sided tape is disposed not to cover the opening  610 . The sealing unit  640  cleanses toner stuck to the blocking film  50  when the blocking film  50  is removed. In order to prevent toner from leaking when the blocking film  50  is removed, the sealing unit  640  is fabricated such that a width W 2  thereof is greater than a width W 3  of the opening  610 . The width W 2  of the sealing unit  640  is determined so that the sealing unit  640  covers below the lower end  611  of the opening  610  and above an upper end  612  of the opening  610 . For example, the width W 2  of the sealing unit  640  may be determined so that the sealing unit  640  covers 0.7 mm or more away from the lower end  611  and away from the upper end  612  of the opening  610 . A guiding rib  620  protrudes from the first sidewall  61 , and guides the sealing unit  640  to be combined with the first sidewall  61  in order to cover below the lower end  611  and above the upper end  612  of the opening  610 . The sealing unit  640  may be formed of an elastic foaming material such as foam rubber. 
     Also, a pressurizing unit  650  may further be installed to push the sealing unit  640  so that the sealing unit  640  is not separated from the first sidewall  61  when the blocking film  50  is removed. The pressurizing unit  650  may be disposed, for example, at an inner side of the side frame  95  that connects the lower frame  60  and the receiving frame  70  with each other. When the side frame  95  is combined with the lower frame  60  and the receiving frame  70 , the pressurizing unit  650  presses the sealing unit  640  not to be separated from the lower frame  60 . In this case, the pressurizing unit  650  presses a location on the sealing unit  640  close to the opening  610 . If the pressurizing unit  650  presses a location on the sealing unit  640  closest to the opening  610 , then the blocking film  50  is extremely firmly pressed by the sealing unit  640  and thus cannot be easily removed. For example, the pressurizing unit  650  may press a location on the sealing unit  640  about 0.5 mm to 1 mm away from the opening  610 . 
       FIG. 13  is a schematic view showing the configuration of an electrophotographic image forming apparatus employing the developing device  100  illustrated in  FIGS. 1 to 12 , according to an embodiment of the present general inventive concept. Referring to  FIG. 12 , the developing device  100  is inserted into a body  700  of the image forming apparatus through a door  701 . The blocking film  50  is removed before inserting the developing device  100  into the body  700 . Thus, the toner container  10  is connected to the developing unit  20  to supply toner to the developing unit  20 . 
     The optical scanning unit  200  scans light, which is modulated according to image information, onto the photoconductive drum  1  which has been charged to a uniform potential. For example, a laser scanning unit (LSU) that scans light emitted from a laser diode onto the photoconductive drum  1  by deflecting the light in a main scanning direction by using a polygon mirror, may be used as the optical scanning unit  200 . 
     The transfer roller  300 , which is an example of a transfer device, is disposed to face a surface of the photoconductive drum  1 , which is exposed through an opening  9   b , in order to form a transfer nip. A transfer bias voltage is applied to the transfer roller  300  so as to transfer a toner image developed on the surface of the photoconductive drum  1  onto a recording medium P. A corona transfer device may be used instead of the transfer roller  300 . 
     The toner image transferred onto the recording medium P by the transfer roller  300  remains adhered to the recording medium P due to electrostatic attraction. A fixing unit  400  applies heat and pressure onto the toner image in order to fix the toner image on the recording medium P, thereby forming a permanent printed image on the recording medium P. 
     A method of forming an image by using the electrophotographic image forming apparatus having the above configuration will now be briefly described. When a charging bias voltage is applied to the charging roller  2 , the photoconductive drum  1  is charged to a uniform potential. The optical scanning unit  200  forms an electrostatic latent image on the photoconductive drum  1  by scanning light, which is modulated according to image information, onto the photoconductive drum  1  through the optical window  9   a  of the developing device  100 . The toner contained in the toner container  10  is supplied to the development unit  20  by the agitator  8  and is then attached to the developing roller  3  by the supply roller  4 . The regulator  6  forms a toner layer having a uniform thickness on the developing roller  3 . A developing bias voltage is applied to the developing roller  3 . The toner is moved to the development nip D as the developing roller  3  rotates and is then transferred and attached to the electrostatic latent image on the photoconductive drum  1 , due to the developing bias voltage. Thus, a visible toner image is formed on the photoconductive drum  1 . The recording medium P picked up from a recording medium tray  501  by a pick-up roller  502  is transported to the transfer nip between the transfer roller  300  and the photoconductive drum  1  by a transporting roller  503 . When a transfer bias voltage is applied to the transfer roller  300 , the toner image is transferred onto the recording medium P by electrostatic attraction. If the fixing unit  400  applies heat and pressure onto the toner image transferred onto the recording medium P, then the toner image is fixed to the recording medium P, thereby completing printing. The recording medium P is externally discharged by a discharge roller  504 . Toner remaining on the surface of the photoconductive drum  1  which has not been transferred to the recording medium P is removed by the cleaning unit  7  and is collected in the waste toner container  30 . 
     While the present general inventive concept has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present general inventive concept as defined by the following claims.