Patent Publication Number: US-2022221812-A1

Title: Developing apparatus

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a developing apparatus preferably adopted in image forming apparatuses utilizing electrophotography technique, such as a printer, a copying machine, a facsimile or a multifunction printer. 
     Description of the Related Art 
     Image forming apparatuses that adopt electrophotography technique, such as printers, copying machines, facsimiles or multifunction printers, are equipped with a developing apparatus that develops and visualizes electrostatic latent images formed on photosensitive drums and that is attached to an apparatus body in a detachable manner. A developing apparatus for replacement includes new developer stored in advance in a storage portion having an opening portion thereof sealed by a sealing sheet so as to prevent new developer from being exposed to outer air and deteriorated. Therefore, if the developing apparatus for replacement is attached, the sealing sheet must be drawn out to open the storage portion and enable developer to flow out of the storage portion. A conveyance screw capable of conveying developer flown out of the storage portion is disposed in the developer container, and the sealing sheet is drawn out toward a rotation axis direction of the conveyance screw. In the developer container, a sheet discharge port that enables the sealing sheet to be drawn out approximately in parallel and enables the sealing sheet being drawn out to be discharged outside the developer container is formed on a lower side close to the conveyance screw than the opening portion or on an extended line of the opening portion of the storage portion (Japanese Patent Application Laid-Open Publication No. 2010-48944). 
     If the conveyance screw is rotated after the sealing sheet is drawn out, developer scatters in the developer container by the rotation of the conveyance screw and scattered developer tends to be discharged easily through the sheet discharge port to the outer side of the developer container. One conceivable method for preventing this problem relates to arranging the sheet discharge port away from the conveyance screw in a rotational axis direction of the conveyance screw, but such arrangement leads to increasing the size of the apparatus, and therefore not easily adopted. Another conceivable method relates to sealing the sheet discharge port with a sealing member formed of an elastic member and enhancing elasticity of the sealing member. However, in such case, force that is required to draw out the sealing sheet becomes too strong, and in some cases, the sealing sheet breaks while being drawn out and the developing apparatus must be replaced again, so that it was difficult to adopt such arrangement. In consideration of these problems, there was a demand for a developing apparatus adopting a configuration where developer is stored in advance in a storage portion sealed by a sealing sheet, wherein developer is prevented from being discharged easily through the sheet discharge port to an outer side of the developer container by the rotation of the conveyance screw after the sealing sheet has been drawn out from the developing apparatus. However, there has not been any proposal of such arrangement. 
     In consideration of the above problems, the present invention provides a developing apparatus that adopts a configuration where developer is stored in advance in a storage portion sealed by a sealing sheet, wherein developer is not easily discharged to the outer side of the developer container by the rotation of the conveyance screw through the sheet discharge port after the sealing sheet has been drawn out. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention, a developing apparatus includes a developer container configured to store developer, a conveyance screw disposed in the developer container and configured to convey developer in the developer container, a wall portion dividing a space above the conveyance screw in the developer container in a rotational axis direction of the conveyance screw and forming a first chamber and a second chamber respectively comprising an opening portion that is opened to a conveyance screw side, and a sheet member sealing an opening portion of the first chamber in a state where developer is stored in the first chamber, the sheet member configured to be peeled off from the opening portion of the first chamber. The second chamber comprises a sheet discharge port that communicates the second chamber and an outer side of the developer container, a portion of the sheet member reaching the outer side of the developer container through the sheet discharge port in a state sealing the opening portion of the first chamber. The sheet discharge port is arranged above the opening portion of the first chamber. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view illustrating a configuration of an image forming apparatus that is suitable for adopting a developing apparatus according to a first embodiment. 
         FIG. 2  is a cross-sectional view illustrating a developing apparatus according to the first embodiment. 
         FIG. 3  is a cross-sectional view illustrating the developing apparatus according to the first embodiment taken at a vertical cross-section along an axial direction. 
         FIG. 4  is a cross-sectional perspective view illustrating in enlarged view a vicinity of a sheet discharge port of the developing apparatus according to the first embodiment. 
         FIG. 5  is a cross-sectional view illustrating a developing apparatus of a second embodiment taken at a vertical cross-section along an axial direction. 
         FIG. 6  is a cross-sectional perspective view illustrating in enlarged view a vicinity of a sheet discharge port of the developing apparatus according to the second embodiment. 
         FIG. 7  is a cross-sectional view illustrating a developing apparatus according to another embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     First Embodiment 
     Image Forming Apparatus 
     Now, a first embodiment will be described. At first, a configuration of an image forming apparatus suitable for adopting a developing apparatus according to the present embodiment will be described with reference to  FIG. 1 . An image forming apparatus  60  illustrated in  FIG. 1  is a color image forming apparatus adopting a tandem-type intermediate transfer system in which image forming units  600  corresponding to four colors are arranged to oppose to an intermediate transfer belt  61  within an apparatus body  100 . 
     A conveyance process of a recording material of the image forming apparatus  60  will be described. A recording material S is stored in a manner stacked in a recording material storage, i.e., cassette,  62 , and the recording material S is fed at a matched timing with an image forming timing by a sheet feed roller  63 . Feeding of sheets from the cassette  62  can utilize a friction separation system, for example. The recording material S sent out from the sheet feed roller  63  is conveyed to a registration roller  65  arranged in midway of a conveyance path  64 . After performing skew correction and timing correction of the recording material S at the registration roller  65 , the recording material S is sent to a secondary transfer portion T 2 . The secondary transfer portion T 2  is a transfer nip portion formed by a secondary transfer inner roller  66  and a secondary transfer outer roller  67  that are opposed to one another, and the secondary transfer portion T 2  applies predetermined pressure and electrostatic load bias to attach a toner image to the recording material S. 
     Regarding the conveyance process of the recording material S to the secondary transfer portion T 2  described above, a process for forming an image sent to the secondary transfer portion T 2  at a similar timing will be described. At first, image forming units  600  will be described. The image forming units  600  of respective colors basically have the same configurations except for the color of the toner, so that in  FIG. 1 , only the image forming unit  600  of black (BK) is denoted with reference numbers, and other image forming units are not denoted with reference numbers. Therefore, in the following description, the image forming unit  600  of black (BK) is illustrated as an example. 
     The image forming unit  600  is mainly composed of a photosensitive drum  1 , a charging unit  2 , a developing apparatus  3 , a photosensitive drum cleaner  5  and so on. The surface of the photosensitive drum  1  driven to rotate is charged uniformly in advance by the charging unit  2 , and thereafter, an electrostatic latent image is formed by an exposing unit  68  that is driven based on an image information signal. Next, the electrostatic latent image formed on the photosensitive drum  1  is visualized by development of toner image by the developing apparatus  3 . That is, the developing apparatus  3  develops the electrostatic latent image using toner included in developer described later and forms a toner image on the photosensitive drum  1 . The developing apparatus  3  will be descried later (refer to  FIG. 2 ). 
     Thereafter, predetermined pressure and electrostatic load bias is applied by primary transfer apparatuses  4  arranged opposed to the image forming units  600  with the intermediate transfer belt  61  intervened, and toner image formed on the photosensitive drum  1  is primarily transferred to the intermediate transfer belt  61 . Primary transfer residual toner remaining on the photosensitive drum  1  after primary transfer is recovered by the photosensitive drum cleaner  5 , and the apparatuses prepare for the next image forming process. 
     According to the present embodiment, four sets of image forming units  600  corresponding to yellow (Y), magenta (M), cyan (C) and black (BK) are provided. However, the number of colors is not restricted to four, and the order in which the colors are arranged is not restricted to this example. The developing apparatus  3  uses two-component developer including nonmagnetic toner and magnetic carrier as developer. Since toner is consumed by development, toner can be replenished to the developing apparatus  3  from a toner bottle  605  storing toner. 
     The intermediate transfer belt  61  onto which toner image is primarily transferred is an endless belt that is stretched across a tension roller  6 , the secondary transfer inner roller  66  and driven rollers  7   a  and  7   b  and moved toward the direction of arrow C in the drawing. In the present embodiment, the secondary transfer inner roller  66  also functions as a drive roller that drives the intermediate transfer belt  61 . The image forming process of respective colors subjected to parallel processing by the image forming units  600  of respective colors mentioned above is performed at a timing for sequentially superposing the toner image on a different colored toner image primarily transferred to the intermediate transfer belt  61  upstream in the direction of movement. As a result, a full-color toner image is finally formed on the intermediate transfer belt  61  and conveyed to the secondary transfer portion T 2 . The secondary transfer residual toner remaining on the intermediate transfer belt  61  after passing the secondary transfer portion T 2  is collected from the intermediate transfer belt  61  by a transfer cleaner device  8 . 
     As described, by the conveyance process and the image forming process described above, the timings of the recording material S and the full-color toner image correspond at the secondary transfer portion T 2 , and secondary transfer where the toner image is transferred from the intermediate transfer belt  61  to the recording material S is performed. Thereafter, the recording material S is conveyed to a fixing unit  9 , where heat and pressure is applied by the fixing unit  9 , and thereby, toner image is melted and fixed to the recording material S. The recording material S to which image has been fixed is selected to be either discharged onto a sheet discharge tray  601  by rotation of the sheet discharge roller  69  in a forward direction or subjected to duplex image forming. 
     If duplex image forming is necessary, after conveying the recording material S such that a trailing edge of the recording material S passes a switching member  602  by rotation of the sheet discharge roller  69  in the forward direction, the sheet discharge roller  69  is rotated in reverse rotation to switch a leading edge and a trailing edge of the recording material S, and then the recording material S is conveyed to a duplex conveyance path  603 . Thereafter, at a matched timing with the recording material for a subsequent job conveyed from the sheet feed roller  63 , the recording material S is sent again to the conveyance path  64  by a sheet refeeding roller  604 . The conveyance and image forming processes performed thereafter are similar to the processes described earlier, so that the descriptions thereof are omitted. 
     Developing Unit 
     Next, the developing apparatus  3  according to the first embodiment will be described based on  FIGS. 2 and 4  with reference to  FIG. 1 . In  FIG. 2 , in order to help understand the present embodiment, a sheet discharge port  80  described later is illustrated by dotted lines. The developing apparatus  3  according to the present embodiment includes, as illustrated in  FIG. 2 , a developer container  30  forming a housing, a developing sleeve  17 , a developing screw  33  and an agitating screw  34 , and a regulating blade  36 . 
     Two-component developer including nonmagnetic toner and magnetic carrier, hereinafter simply referred to as developer, is stored in the developer container  30 . That is, the developing apparatus  3  of the present embodiment adopts a two-component developing system as developing system and uses developer in which nonmagnetic toner having negative charge polarity and magnetic carrier having positive charge polarity are mixed. Nonmagnetic toner is formed by including coloring agent, external additive such as colloidal silica fine powder or wax in resin such as polyester or styrene acryl and powdering by pulverization or polymerization. Magnetic carrier is formed by applying resin coating on a surface of cores formed of ferrite particles or resin particles kneaded with magnetic powder. Toner density, that is, ratio of toner weight with respect to total weight of toner and carrier, of a new developer in a so-called initial state is 10%, for example. 
     The developer container  30  has one portion opposed to the photosensitive drum  1  opened, and a developing sleeve  17  capable of bearing developer is rotatably arranged in the developer container  30  to be partially exposed from the opening. The developing sleeve  17  serving as a developer bearing member is formed into a cylindrical shape using nonmagnetic material such as aluminum and stainless steel and rotated in a same direction as the photosensitive drum  1  at a surface opposed to the photosensitive drum  1  (refer to arrows R 2  and R 3  in the drawing). The direction of rotation of the developing sleeve  17  may also be opposite to the direction of the photosensitive drum  1  at the surface opposed to the photosensitive drum  1 . 
     A magnet roller  18  is arranged on an inner side of the developing sleeve  17  and fixed thereto. A magnetic brush of developer is formed on the surface of the developing sleeve  17  by magnetic force of the magnet roller  18 . The magnetic brush formed on a surface of the developing sleeve  17  has its layer thickness regulated by the regulating blade  36  and is sent to a predetermined developing area. The regulating blade  36  is a plate-like member formed of nonmagnetic material such as aluminum, and it is disposed along a rotational axis direction, i.e., longitudinal direction, of the developing sleeve  17 . In a state where the magnetic brushes moved to the developing area brush against the photosensitive drum  1 , the electrostatic latent image formed on the photosensitive drum  1  is developed as toner image. In this state, either DC voltage or superposed voltage in which DC voltage and AC voltage are superposed is applied as developing voltage from a power supply not shown to the developing sleeve  17 . 
     The developer container  30  is divided into a developing chamber  31  and an agitating chamber  32  by a partition wall  39  that is arranged to extend in a vertical direction in the drawing at approximately a center portion thereof. The developing chamber  31  and the agitating chamber  32  are communicated through communication portions that are arranged at both ends in a longitudinal direction of the partition wall  39 , by which a circulation path of developer is formed. The developing screw  33  is disposed rotatably on the developing chamber  31  and the agitating screw  34  is disposed rotatably on the agitating chamber  32 . The developing screw  33  and the agitating screw  34  are screws respectively having vanes not shown disposed helically around rotation shafts  33   a  and  34   a.    
     The developing sleeve  17 , the developing screw  33  and the agitating screw  34  mentioned above are connected via a gear train and are rotated by a drive motor not shown via the gear train. In a state where the developing screw  33  rotates, developer in the developing chamber  31  is conveyed along the developing screw  33 , during which a portion of the developer is supplied to the developing sleeve  17 . Developer conveyed in the developing chamber  31  is transferred from the developing chamber  31  to the agitating chamber  32  via a communication portion on a first end side of the partition wall  39  at a downstream side in a developer conveyance direction of the developing screw  33 . Meanwhile, if the agitating screw  34  rotates, developer in the agitating chamber  32  is conveyed to an opposite direction as the developer conveyance direction of the developing screw  33  along the agitating screw  34 . Developer conveyed in the agitating chamber  32  is transferred from the agitating chamber  32  to the developing chamber  31  through a communication portion on a second end side of the partition wall  39  at an upstream side in the developer conveyance direction of the developing screw  33 . In this manner, developer is conveyed in circulation in the developer container  30  while being agitated by the developing screw  33  and the agitating screw  34 . 
     Storage Portion and Sealing Sheet 
     In order to improve convenience, the developing apparatuses  3  of respective colors are detachably attached to the apparatus body  100  (refer to  FIG. 1 ) according to the present embodiment. In the developing apparatus  3  for replacement, developer in a new state that is not yet used for developing images, also referred to as initial state, is sealed in advance in the developer container  30  so that it is not exposed to air and deteriorated. In the present embodiment, as illustrated in  FIG. 2 , a storage portion  35  capable of storing new developer in advance is formed above the agitating screw  34  serving as the conveyance screw in the developer container  30 . 
     The storage portion  35  serving as a first chamber is formed by dividing a space above the agitating screw  34  in the developer container  30  in the rotational axis direction, i.e., longitudinal direction, of the agitating screw  34  by a wall portion  35   b , as illustrated in  FIGS. 3 and 4 . In addition to the storage portion  35 , the wall portion  35   b  defines a space portion  32   a  serving as a second chamber. In other words, the developing apparatus  3  includes the storage portion  35  and the space portion  32   a  formed by dividing a space above the agitating screw  34  in the developer container  30  by the wall portion  35   b  in the horizontal direction in a state where the developer container  30  is attached to the image forming apparatus  60 . The storage portion  35  and the space portion  32   a  are arranged adjacent one another in a rotational axis direction of the agitating screw  34 . In the present embodiment, the storage portion  35  and the space portion  32   a  are opened toward the agitating screw  34  and are communicated with the agitating chamber  32 . That is, both the storage portion  35  and the space portion  32   a  have opening portions that are opened downward. Preferably, the storage portion  35  is formed to approximately cover the whole area in which the blade (not shown) of the agitating screw  34  is formed with respect to the rotational axis direction of the agitating screw  34 , so that the developer is conveyed efficiently after a sealing sheet  37  described later is drawn out. 
     The sealing sheet  37  can be adhered onto an opening portion  35   a  of the storage portion  35 , and the sealing sheet  37  is capable of sealing the opening portion  35   a  in a state where developer is stored in the storage portion  35 . The sealing sheet  37  is a sheet member formed of a resin material such as a plastic film, for example, and it is adhered to the opening portion  35   a  by an appropriate method, such as heat sealing or using adhesive agent, so that it can be peeled off from the opening portion  35   a . As described, the storage portion  35  can be sealed by the sealing sheet  37  in a state where new developer is stored therein. That is, the sealing sheet  37  can seal the opening portion  35   a  when developer is stored in the storage portion  35  and be peeled off from the opening portion  35   a.    
     The developing apparatus  3  for replacement stores new developer in advance in the storage portion  35  sealed by the sealing sheet  37  as described, and no developer is stored in the developing chamber  31  and the agitating chamber  32  including the space portion  32   a . Therefore, in a state where the developing apparatus  3  for replacement is attached, the sealing sheet  37  must be removed. If the sealing sheet  37  is removed, developer stored in the storage portion  35  drops into the agitating chamber  32  including the agitating screw  34  and is conveyed by the rotation of the agitating screw  34  and the developing screw  33 , such that new developer is delivered throughout the developer container  30 . In the present embodiment, the sealing sheet  37  is configured to be drawn out in the rotational axis direction, i.e., longitudinal direction, of the agitating screw  34  from the outer side of the developer container  30 . 
     As illustrated in  FIG. 4 , a sheet discharge port  80  is formed on the developer container  30  so as to enable the sealing sheet  37  to be drawn out in the longitudinal direction. That is, the space portion  32   a  includes the sheet discharge port  80  that communicates the space portion  32   a  with the outer side of the developer container  30 . In the present embodiment, the sheet discharge port  80  is formed on an end wall  30   a  of the developer container  30  having a bearing portion (not shown) for rotatably supporting the agitating screw  34  so as to enable the sealing sheet  37  to be drawn out along the rotational axis direction of the agitating screw  34 . Specifically, the sheet discharge port  80  is formed on the end wall  30   a  opposite to the wall portion  35   b  interposing the space portion  32   a . That is, the sheet discharge port  80  is formed on the end wall  30   a  of the space portion  32   a  opposed to the wall portion  35   b  with respect to the rotational axis direction. 
     A first end side of the sealing sheet  37  that is not adhered to the opening portion  35   a  is inserted to the sheet discharge port  80  so that the first end side, i.e., free end portion  37   b  described later, projects out of the developer container  30 . A portion of the sealing sheet  37  reaches the outer side of the developer container  30  through the sheet discharge port  80  in a state where the sealing sheet  37  seals the opening portion  35   a  of the storage portion  35 . Since the first end side of the sealing sheet  37  is projected to the outer side of the developer container  30  through the sheet discharge port  80 , the sealing sheet  37  can be drawn out from outside the developer container  30 . Thereby, in a state where the sealing sheet  37  is drawn out, the sealing sheet  37  is discharged to the outer side of the developer container  30  while being guided by the sheet discharge port  80 . 
     According to the present embodiment, the sheet discharge port  80  is formed above the opening portion  35   a  when viewed from the horizontal direction. As described, the sheet discharge port  80  is separated from the agitating screw  34  with respect to a radial direction of the agitating screw  34 , and therefore, developer will not be easily discharged by the rotation of the agitating screw  34  to the outer side of the developer container  30  through the sheet discharge port  80  after the sealing sheet  37  has been drawn out. 
     The sheet discharge port  80  is an opening having a long hole shape, and it is formed such that a longitudinal direction of the long hole shape is inclined at a predetermined angle with respect to a horizontal direction. The predetermined angle (refer to an angle in  FIG. 4 ) should preferably be 30 degrees or greater and smaller than 90 degrees with respect to the horizontal direction, and more preferably, 45 degrees, since if the angle is too great, the tension applied while drawing out the sealing sheet  37  may be too high. By inclining the sheet discharge port  80 , the upper end side of the sheet discharge port  80  will be more separated from the agitating screw  34  than the lower end side with respect to the radial direction of the agitating screw  34 . Then, compared to the case where the sheet discharge port  80  is not inclined (0=0), developer is not easily discharged by the rotation of the agitating screw  34  to the outer side of the developer container  30  through the sheet discharge port  80  after the sealing sheet  37  has been drawn out. 
     Further, as illustrated in  FIGS. 2 and 4 , in a state where a wall surface  30   c  of the developer container  30  on an opposite side from the developing sleeve  17  in a width direction intersecting the rotational axis direction of the agitating screw  34  is formed to be inclined with respect to the vertical direction, the sheet discharge port  80  can be inclined along the inclination of the wall surface  30   c . That is, the sheet discharge port  80  can be inclined at a same angle of inclination as the wall surface  30   c  with respect to the vertical direction. The sheet discharge port  80  is arranged such that the longitudinal direction of the long hole shape thereof is arranged along an edge portion  30   e  on an end wall side of the wall surface  30   c  of the side wall. In this case, at least a portion of the sheet discharge port  80  may be formed to overlap with the wall portion  35   b  when viewed from the rotational axis direction of the agitating screw  34 . According to this arrangement, it becomes possible to prevent developer from being easily discharged by the rotation of the agitating screw  34  to the outer side of the developer container  30  through the sheet discharge port  80  after the sealing sheet  37  has been drawn out, without having to increase the size of the apparatus. 
     The sealing sheet  37  adhered to the opening portion  35   a  is bent, as illustrated in  FIG. 4 , and projected to the outer side of the developer container  30  through the sheet discharge port  80 . That is, in a state where the sealing sheet  37  seals the opening portion  35   a  of the storage portion  35 , a sealing portion  37   a  that seals the opening portion  35   a  and a free end portion  37   h  that is projected to the outer side of the developer container  30  from the sheet discharge port  80  are connected by a bent portion  37   c  bent in the space portion  32   a . The bent portion  37   c  serves to change the positions where the sealing portion  37   a  and the free end portion  37   b  are extended in the space portion  32   a , such that force by which the sealing portion  37   a  is drawn out is transmitted appropriately from the free end portion  37   b  during draw out operation to thereby enable the sealing sheet  37  to be easily discharged through the sheet discharge port  80 . If the sheet discharge port  80  is formed above the opening portion  35   a  when viewed from the horizontal direction, the sealing sheet  37  must be bent. Therefore, according to the present embodiment, the storage portion  35  and the space portion  32   a  are defined by the wall portion  35   b  so as to ensure the space portion  32   a  in which the bent portion  37   c  described above is stored. In other words, by ensuring the space portion  32   a  by the wall portion  35   b , it becomes possible to form the sheet discharge port  80  above the opening portion  35   a  when viewed from the horizontal direction. 
     A sealing member  40  formed of an elastic member such as urethane material can be arranged in the sheet discharge port  80 , as illustrated in  FIG. 4 . The sealing member  40  is arranged to fill the gap of the sheet discharge port  80  while the sealing member  40  interposes the sealing sheet  37  in a manner capable of passing through the sheet discharge port  80 . The sealing member  40  is an elastic member capable of interposing the sealing sheet  37  to allow the sealing sheet  37  to pass therethrough and also capable of sealing the sheet discharge port  80  after the sealing sheet  37  has been drawn out of the developer container  30  through the sheet discharge port  80 . 
     As described, according to the present embodiment, the sheet discharge port  80  is formed above the opening portion  35   a  when viewed from the horizontal direction to thereby separate the sheet discharge port  80  from the agitating screw  34  in the radial direction of the agitating screw  34 . Further, by inclining the sheet discharge port  80  by a predetermined angle with respect to the horizontal direction, the sheet discharge port  80  can be separated from the agitating screw  34  in the radial direction of the agitating screw  34 . Thus, it becomes possible to easily realize an arrangement where developer is not easily discharged by the rotation of the agitating screw  34  to the outer side of the developer container  30  through the sheet discharge port  80  after the sealing sheet  37  has been drawn out. 
     Second Embodiment 
     A developing apparatus  3 A according to a second embodiment will be described with reference to  FIGS. 5 and 6 . The developing apparatus  3 A according to the second embodiment has a similar configuration as the developing apparatus  3  of the first embodiment described earlier (refer to  FIGS. 3 and 4 ), except for the point that a discharge port wall  41  that is projected to the inner side of the developer container  30  is provided. Therefore, regarding the developing apparatus  3 A of the second embodiment, the same configurations as the developing apparatus  3  of the first embodiment are assigned with the same reference numbers and descriptions thereof are omitted. 
     In the present embodiment, the discharge port wall  41  serving as a protruded portion arranged in a manner surrounding the sheet discharge port  80  is formed in the developer container  30 . That is, the developer container  30  includes the discharge port wall  41  that is projected toward the inner side of the developer container  30  from the end wall  30   a  on which the sheet discharge port  80  is formed. The discharge port wall  41  enables the amount of developer scattered in the developer container  30  by the rotation of the agitating screw  34  after the sealing sheet  37  has been drawn out that flows into the sheet discharge port  80  to be reduced. According to this arrangement, the elasticity of the sealing member  40  (refer to  FIG. 4 ) can be reduced, or even further, the sealing member  40  can be omitted. Then, the force required for drawing out the sealing sheet  37  can be reduced, and the problem of the sealing sheet  37  being broken when being drawn out from the developer container  30  can be reduced. Furthermore, the discharge port wall  41  includes a guide portion  41   a  that guides the sealing sheet  37  to the sheet discharge port  80  when the sealing sheet  37  is drawn out of the developer container  30  through the sheet discharge port  80 . Thereby, the arrangement of the sealing sheet  37  with respect to the sheet discharge port  80  can be stabilized while drawing out the sealing sheet  37 , so that even if the sheet discharge port  80  is inclined, the sealing sheet  37  will not be easily broken when being drawn out. 
     At least a portion of the discharge port wall  41  should be arranged below the sheet discharge port  80 . However, it is more preferable to form the discharge port wall  41  in a manner surrounding the sheet discharge port  80  as according to the present embodiment, since developer is less likely to be discharged through the sheet discharge port  80 . 
     OTHER EMBODIMENTS 
     The sealing sheet  37  can be drawn out by a user manually or by a removing device (not shown) configured to automatically wind the sealing sheet  37 . In the removing device, a first end of the sealing sheet  37  is fixed to a winding shaft, and in a state where the winding shaft is rotated to wind the sealing sheet  37 , the sealing sheet  37  is drawn to the outer side of the developer container  30 . In a case where such removing device is used, the developing apparatus  3  will not be operated without drawing out the sealing sheet  37  and the sealing sheet  37  is collected in the developer unit  3  so that there is no need for the user to dispose the sealing sheet  37  having been drawn out of the developer container  30  as waste. 
     In the first and second embodiments described above, an example has been described where the sealing sheet  37  is drawn out in the rotational axis direction of the agitating screw  34 , but the direction in which the sealing sheet  37  is drawn out is not restricted to this example. That is, the sheet discharge port  80  can be formed at a portion other than the end wall  30   a  of the developer container  30 . For example, in a type of apparatus where the developing apparatuses  3  of respective colors are placed in parallel on a support base (not shown) drawn out from the apparatus body  100  and the plurality of developing apparatuses  3  are collectively attached together with the support base onto the apparatus body  100 , the sealing sheet  37  should be drawn out after placing the new developing apparatus  3  on the support base. In this case, the sealing sheet  37  can be drawn out toward a radial direction of the agitating screw  34 , instead of toward the rotational axis direction of the agitating screw  34 . Therefore, the sheet discharge port  80  can be formed on the wall surface  30   c  (refer to  FIG. 4 ) of the developer container  30 , for example. 
     According to the first and second embodiments described above, as illustrated in  FIG. 2 , a case has been described where the side wall along the rotational axis direction of the storage portion  35  is disposed separately from the wall surface  30   c  and the partition wall  39  of the developer container  30 , but the present invention is not restricted thereto. For example, as illustrated in  FIG. 7 , the side wall arranged along the rotational axis direction of the storage portion  35  can be formed of the same material as the wall surface  30   c  and the partition wall  39  of the developer container  30 . Even according to this example, the sheet discharge port  80  is formed above the opening portion  35   a  in the horizontal direction, such that developer can be prevented from being easily discharged by the rotation of the agitating screw  34  to the outer side of the developer container  30  through the sheet discharge port  80  after the sealing sheet  37  has been drawn out. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2018-032050, filed Feb. 26, 2018, which is hereby incorporated by reference herein in its entirety.