Abstract:
A developing device for an image forming apparatus, comprising a frame provided with a developer accommodating chamber accommodating a developer, and a development opening for supplying the developer from an inside of the developer accommodating chamber to an outside; a first sealing member sealing the development opening, the first sealing member being dismountable from the development opening by being pulled out through a pulling opening provided in the frame; and a second sealing member for sliding on the first sealing member to prevent the developer from leaking to an outside of the frame through the pulling opening when the first sealing member is pulled through the pulling opening, wherein the second sealing member is integrally molded on the frame by injecting a thermoplastic elastomer into a space between the first sealing member and an edge of the pulling opening.

Description:
FIELD OF THE INVENTION AND RELATED ART 
     The present invention relates to a developing apparatus, a process cartridge and a method for assembling a developing apparatus. 
     In the field of an electrophotographic image forming apparatus, it has been common practice to employ a process cartridge system, which integrates an electrophotographic photosensitive member (which hereafter may be referred to simply as photosensitive drum), a developing apparatus (device), etc., in the form of a cartridge, which is removably installable in the main assembly of an electrophotographic image forming apparatus. A process cartridge system makes it possible for a user of an electrophotographic image forming apparatus to maintain the apparatus without relying on a service person. Thus, it can substantially improve an electrophotographic image forming apparatus in usability. 
     The developing apparatus (device) in a process cartridge has a frame having a development chamber and a developer storage chamber. The development chamber is the chamber in which a developer bearing member for supplying the peripheral surface of the photosensitive drum in the process cartridge with developer is placed. The development chamber and developer storage chamber are in connection to each other through an opening which is between the two chambers. 
     Thus, it has to be ensured that the developer in the developer storage chamber of a process cartridge does not leak into the development chamber of the process cartridge during the period between the production of the process cartridge and when the process cartridge is used for the first time. Thus, the aforementioned opening between the development chamber and developer storage chamber is kept sealed with a piece of film welded to the developer storage chamber frame. This sealing film is to be removed by a user, or automatically removed by the image forming apparatus, before the cartridge begins to be used for the first time, after the installation of the process cartridge into the apparatus main assembly. 
     At this time, referring to  FIG. 21 , a process cartridge B is described about its general structure.  FIG. 21  is an exploded perspective view of the cartridge B, which is for describing the general structure of the cartridge B. As is evident from  FIG. 21 , the cartridge B is made up of a cleaning unit C and a development unit D. The cleaning unit C has a photosensitive drum  2  and a cleaning unit frame  9 . The development unit D has a developer bearing member (unshown) and a development unit frame  13 . 
     The development unit frame  13  is provided with an opening  13   a , which is covered with a sealing film  103  for preventing the developer in the developer storage chamber of the development unit D from leaking. The sealing film  103  is welded to the rim of the opening  13   d.    
     Further, the development unit frame  13  is provided with a slit  101  so that a user can extract the sealing film  103  from the process cartridge B through the slit  101 , by pulling the end portion of the sealing film  103  outward of the development unit frame  13 , that is, the direction indicated by an arrow mark X. That is, the sealing film  103  is removed from the development unit frame  13  by being extracted through the slit  101 . 
     The developer in the development storage chamber has to be prevented from leaking from the process cartridge not only prior to the removal of the sealing  103 , but also, after the removal of the sealing film  103 . Thus, there have been proposed various methods for preventing the developer in the development storage chamber from leaking from the cartridge B. One of the methods is disclosed in Japanese Laid-open Application No. 3142746. Accordingly to this patent application, a sealing member  902  ( FIG. 22 ) made of thermoplastic elastomer, sponge, or the like is inserted into the sealing film extraction slit  101  to keep the slit  101  plugged. One of the examples of feasible structural arrangements for the sealing member  902  is shown in  FIG. 22 .  FIGS. 22(   a )- 22 ( c ) are sectional views of the combination of the sealing member  902  and development unit frame  13 , at a vertical plane which coincides with a line P 1 -P 1 , in  FIG. 21 , which is parallel to the direction indicated by the arrow mark X.  FIGS. 22(   a )- 22 ( c ) correspond to the state of sealing member  902  before, during, and after its insertion into the sealing film extraction slit  101 , respectively. 
     Referring to  FIG. 22(   a ), the sealing member  902  is made up of a base portion  902   a , and fin portions  902   b  which perpendicularly project from the base portion  902   a . Next, referring to  FIG. 22(   b ), the sealing member  902  is to be inserted into the sealing film extraction slit  101  from the opposite direction from the direction indicated by the arrow mark X, while the sealing film  103  is kept tensioned by a preset amount of force applied to the sealing film  103  in the direction indicated by the arrow mark X. Further, the development unit frame  13  is structured so that as the sealing member  902  is inserted into the sealing film extraction slit  101 , the angle of contact between each of the fin portions  902   a  and the sealing film  103  becomes a preset angle θ. Therefore, as the sealing film  103  is pulled out through the film extraction slit  101 , the fin portions  902   b , which are in contact with the sealing film  103  wipe away the developer having adhered to the sealing film  103 , as shown in  FIG. 22(   c ). Therefore, the developer does not leak through the sealing film extraction slit  101 . 
     SUMMARY OF THE INVENTION 
     The present invention is one of the results of the further development of the structural arrangement for the sealing member for a process cartridge, such as the above described one. Thus, the primary object of the present invention is to provide a process cartridge and/or a developing apparatus, which is simpler in terms of the operation for attaching the sealing film, and the process for attaching the sealing member, than any of the process cartridges and developing apparatuses which are in accordance with the prior art. 
     According to an aspect of the present invention, there is provided a developing device for an image forming apparatus, comprising a frame provided with a developer accommodating chamber accommodating a developer, and a development opening for supplying the developer from an inside of said developer accommodating chamber to an outside; a first sealing member sealing said development opening, said first sealing member being dismountable from said development opening by being pulled out through a pulling opening provided in said frame; and a second sealing member for sliding on said first sealing member to prevent the developer from leaking to an outside of said frame through said pulling opening when said first sealing member is pulled through said pulling opening, wherein said second sealing member is integrally molded on said frame by injecting a thermoplastic elastomer into a space between said first sealing member and an edge of said pulling opening. 
     According to another aspect of the present invention, there is provided a developing device for an image forming apparatus, comprising a frame provided with a developer accommodating chamber accommodating a developer, and a development opening for supplying the developer from an inside of said developer accommodating chamber to an outside; a first sealing member sealing said development opening, said first sealing member being dismountable from said development opening by being pulled out through a pulling opening provided in said frame; and a second sealing member for sliding on said first sealing member to prevent the developer from leaking to an outside of said frame through said pulling opening when said first sealing member is pulled through said pulling opening, wherein said second sealing member is provided with a retaining portion for preventing said second sealing member from moving in a pulling direction of said first sealing member, by engaging with a regulating portion of said frame. 
     According to a further aspect of the present invention, there is provided a process cartridge detachably mountable to a main assembly of an image forming apparatus, said process cartridge comprising an image bearing member for bearing a latent image; a developer carrying member for carrying a developer; a frame provided with a developer accommodating chamber accommodating the developer, a developing chamber holding said developer carrying member, and a development opening for fluid communication between said developing chamber and said developer accommodating chamber; a first sealing member sealing said development opening, said first sealing member being dismountable from said development opening by being pulled out through a pulling opening provided in said frame; and a second sealing member for sliding on said first sealing member to prevent the developer from leaking to an outside of said frame through said pulling opening when said first sealing member is pulled through said pulling opening, wherein said second sealing member is integrally molded on said frame by injecting a thermoplastic elastomer into a space between said first sealing member and an edge of said pulling opening 
     According to a further aspect of the present invention, there is provided a process cartridge detachably mountable to a main assembly of an image forming apparatus, said process cartridge comprising an image bearing member for bearing a latent image; a developer carrying member for carrying a developer; a frame provided with a developer accommodating chamber accommodating the developer, a developing chamber holding said developer carrying member, and a development opening for fluid communication between said developing chamber and said developer accommodating chamber; a first sealing member sealing said development opening, said first sealing member being dismountable from said development opening by being pulled out through a pulling opening provided in said frame; and a second sealing member for sliding on said first sealing member to prevent the developer from leaking to an outside of said frame through said pulling opening when said first sealing member is pulled through said pulling opening, wherein said second sealing member is provided with a retaining portion for preventing said second sealing member from moving in a pulling direction of said first sealing member, by engaging with a regulating portion of said frame. 
     According to a further aspect of the present invention, there is provided an assembling method for a developing device, said assembling method comprising preparing a frame provided with a developer accommodating chamber accommodating a developer, a development opening for supplying the developer from an inside of said developer accommodating chamber to an outside, and a pulling opening through which a first sealing member for sealing said development opening is pulled; and providing a second sealing member by injecting a thermoplastic elastomer into a space between said first sealing member and said pulling opening in a state that said first sealing member is mounted to said development opening to seal said development opening, thus sealing said pulling opening. 
     According to a further aspect of the present invention, there is provided an assembling method for a developing device, said assembling method comprising preparing a frame provided with a developer accommodating chamber accommodating a developer, a development opening for supplying the developer from an inside of said developer accommodating chamber to an outside, a pulling opening through which a first sealing member for sealing said development opening is pulled, and a regulating portion for suppressing movement of said second sealing member in a pulling direction of said first sealing member; and sealing said pulling opening by inserting said second sealing member into said pulling opening in a state that first sealing member is mounted to said development opening to seal said development opening, and engaging a retaining portion provided on said second sealing member with said regulating portion in a process of inserting said second sealing member into said pulling opening. 
     These and other objects, features, and advantages of the present invention will become more apparent upon consideration of the following description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic sectional view of the image forming apparatus in the first embodiment of the present invention, at a vertical plane parallel to the recording medium conveyance direction of the apparatus, and shows the general structure of the apparatus. 
         FIG. 2  is a schematic sectional view of the process cartridge in the first embodiment, and shows the general structure of the cartridge. 
         FIGS. 3(   a ),  3 ( b ) and  3 ( c ) are perspective views of the development unit frame of the cartridge, and sequentially shows how the sealing film is attached to the development unit frame. 
         FIG. 4  is a perspective view of the lengthwise end portion of the cartridge in the first embodiment, from which the sealing film of the cartridge is to be pulled out. It shows the state of the lengthwise end portion of the cartridge before the cartridge is used for the first time. 
         FIG. 5(   a ) is a schematic sectional view of the process cartridge in the first embodiment of the present invention, at a plane perpendicular to the recording medium conveyance direction of the cartridge.  FIG. 5(   b ) is a schematic sectional view of the process cartridge, at a vertical plane parallel to the recording medium conveyance direction.  FIG. 5(   c ) is a side view of the cartridge, as seen from the side from which the sealing film is extracted. 
         FIGS. 6(   a ),  6 ( b ) and  6 ( c ) are drawings for describing the process for forming the sealing member in the first embodiment. 
         FIGS. 7(   a ) and  7 ( b ) are drawings for describing the process for forming the sealing member in the first embodiment. 
         FIGS. 8(   a ) and  8 ( b ) are drawings of the development unit immediately after the removal of the metallic molds from the development unit frame of the process cartridge. 
         FIGS. 9(   a ) and  9 ( b ) are drawings for describing the difference in developer removal performance between a sealing member, the sealing edge of which makes an obtuse angle with the sealing film, and a sealing member, the sealing edge of which makes an acute angle with the sealing film. 
         FIG. 10  is a schematic sectional view of the end portion of the development unit frame of the cartridge, which has the sealing film extraction slit. It shows the state of the sealing member after the removal of the sealing film. 
         FIG. 11  is a perspective view of the end portion of the development unit frame of the cartridge in the second embodiment of the present invention, which has the sealing film extraction slit. It shows the state of the cartridge before the cartridge is used for the first time. 
         FIG. 12  is a schematic sectional view of the downstream end portion of the process cartridge in terms of the direction in which the sealing member is pulled out of the cartridge. It shows the structure of the sealing member in the second embodiment. 
         FIGS. 13(   a ),  13 ( b ) and  13 ( c ) are schematic sectional views of the downstream end portion of the second embodiment in terms of the sealing film extraction direction. They sequentially show the process through which the sealing member in the second embodiment is formed. 
         FIG. 14(   a ) is a schematic sectional view of the sealing member and its adjacencies of the development unit frame of the process cartridge in the third embodiment of the present invention, and shows the structure of the sealing member.  FIG. 14(   b ) is a perspective view of the sealing member in the third embodiment, and  FIG. 14(   c ) is a schematic sectional view of the development unit frame  13  of the process cartridge, at a vertical plane which is parallel to the recording medium conveyance direction and intersects with the sealing film extraction slit. It shows the structure of the development unit frame  13 , which corresponds in position to the sealing film extraction slit. 
         FIG. 15(   a ) is a schematic perspective view of the end portion of the development unit frame of the process cartridge in the fourth embodiment of the present invention, which has the sealing film extraction slit.  FIG. 15(   b ) is a schematic perspective view of the end portion of the development unit frame of the cartridge prior to the installation of the sealing member. 
         FIG. 16  is a schematic sectional view of the portion of the development unit frame of the process cartridge in the fourth embodiment, in which the sealing film extraction slit and sealing member are present. 
         FIG. 17  is a schematic sectional view of the portion of the development unit frame of the process cartridge in the fourth embodiment, which has the sealing film extraction slit and sealing member. 
         FIGS. 18(   a ),  18 ( b ) and  18 ( c ) are schematic sectional views of the portion of the development unit frame of the process cartridge in the fourth embodiment, which has the sealing film extraction slit and sealing member, before, during, and after the installation of the sealing member into the slit. 
         FIG. 19  is a schematic sectional view of the sealing member, and its adjacencies, of the process cartridge in the fourth embodiment, and shows the structure of the sealing member. 
         FIG. 20(   a ) is a schematic sectional view of the portion of the development unit frame of the process cartridge in the fourth embodiment, which has one of the modified versions of the sealing member in the fourth embodiment. It shows the structure of the modified version of the sealing member.  FIG. 20(   b ) is a schematic perspective view of the modified version of the sealing member, and shows the structure of the sealing member. 
         FIG. 21  is an exploded perspective view of a comparative process cartridge, and shows the structure of the cartridge. 
         FIGS. 22(   a ),  22 ( b ) and  22 ( c ) are sectional views of the portion of the development unit frame of the comparative process cartridge, which has the sealing film extraction slit and sealing member. They sequentially show the portion before, during, and after the insertion of the sealing member into the sealing film extraction slit. 
         FIG. 23  is a drawing for describing the sealing member and development unit frame of the comparative process cartridge. 
         FIGS. 24(   a ),  24 ( b ) and  24 ( c ) are schematic sectional views of the portion of the development unit frame of the comparative process cartridge, which has the sealing film extraction slit and sealing member. They show the portion before, during, and after the insertion of the sealing member into the slit. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     (Overall Structure of Image Forming Apparatus) 
     First, referring to  FIG. 1 , a typical electrophotographic image forming apparatus, with which the present invention is compatible, and which is in the form of a laser printer (which hereafter will be referred to simply as image forming apparatus A) is described about its overall structure.  FIG. 1  is a schematic sectional view of the image forming apparatus A, at a vertical plane parallel to the recording medium conveyance direction of the apparatus A, and shows the general structure of the apparatus A. The image forming apparatus A has a laser scanner  1 , a sheet feeder cassette  3 , a pickup roller  4 , a recording medium pressing member  5 , a transfer roller  6 , a fixing device  7 , a pair of discharge rollers  8 , and a recording medium conveying means, which are the major structural components of the apparatus A. Here, the recording medium conveying means is the means which conveys recording medium such as a sheet of paper, from the sheet feeder cassette  3  into the main assembly of the image forming apparatus A, and conveys the recording medium out of the main assembly of the apparatus A. Further, the image forming apparatus A is structured so that a process cartridge B (which hereafter may be referred to simply as cartridge B), is removably installable in the main assembly of the apparatus A. 
     Next, referring to  FIG. 2 , the cartridge B is described.  FIG. 2  is a schematic sectional view of the cartridge B, and shows the general structure of the cartridge B. The cartridge B consists of two primary units, that is, a cleaning unit C, and a development unit D (as developing device). The cleaning unit C has: an electrophotographic photosensitive member  2  (which hereafter may be referred to simply as photosensitive drum) as an image bearing member; a cleaning unit frame  9 , a cleaning blade  10 , and a charge roller  11 . The photosensitive drum  2  and charge roller  11  are rotatably supported in contact with each other, by the frame  9 . The cleaning blade  10  is attached to the frame  9  in such a manner that its cleaning edge remains in contact with the peripheral surface of the photosensitive drum  2 . Further, the cleaning unit frame  9  is provided with a waste toner container  9   a  in which the waste toner, that is, the toner removed from the peripheral surface of the photosensitive drum  2  by the cleaning blade  10 , is stored. 
     The development unit D has a developer bearing member  12 , a development unit frame  13 , a development blade  14 , and a developer stirring member  15 . The development unit frame  13  has: a developer storage chamber  13   b  in which toner T, which is developer, is stored; and a development chamber  13   c  in which the developer bearing member  12  is placed. The developer bearing member  12  is rotatably supported by the development unit frame  13 . The development blade  14  is attached to the development unit frame  13 , and is kept virtually in contact with the peripheral surface of the developer bearing member  12 . The developer stirring member  15  is in the developer storage chamber  13   b , and is rotatably supported by the development unit frame  13 . 
     Further, the development unit frame  13  is provided with an opening  13   d  through which the developer storage chamber  13   b  is in connection to the development chamber  13   c . Before the cartridge B is used for the first time, the developer delivery opening  13   d  of the development unit frame  13  is kept sealed with a sealing film  103 , which is the first sealing member of the cartridge B, that is, the sealing member for keeping the developer delivery opening  13   c  sealed. More specifically, the sealing film  103  keeps the developer delivery opening  13   d  sealed by being welded to the development unit frame  13 . The sealing film  103  is to be removed immediately before the cartridge B is used for the first time. As the sealing film  103  is removed, the toner T in the developer storage chamber  13   b  is allowed to be moved into the development chamber  13   c  by the developer stirring member  15  while being stirred by the stirring member  15 . 
     Next, referring to  FIGS. 1 and 2 , the image forming operation of the image forming apparatus in this embodiment is briefly described. First, the charge roller  11  charges the peripheral surface of the photosensitive drum  2 . Then, the laser scanner  1  exposes the charged portion of the peripheral surface of the photosensitive drum  2 ; the laser scanner  1  scans the charge portion of the peripheral surface of the photosensitive drum  2  with a beam L of laser light, which it emits while modulating the beam L with the electrical signals generated based on the information of the image to be formed. Consequently, an electrostatic latent image is formed on the peripheral surface of the photosensitive drum  2  (image bearing member). 
     Meanwhile, the stirring member  15  in the developer storage chamber  13   b  stirs the toner T in the developer storage chamber  13   b . Thus, the toner T is conveyed to the developer bearing member  12  in the development chamber  13   c  through the developer delivery opening  13   d  of the development unit frame  13 . Then, as the developer bearing member  12  rotates in the direction indicated by an arrow mark R in  FIG. 2 , the toner T is borne on the peripheral surface of the developer bearing member  12 , forming a layer of the toner T (toner layer). Then, as the developer bearing member  12  is rotated further, the layer of the toner T on the peripheral surface of the developer bearing member  12  is conveyed the to the development blade  14  by the rotation of the developer bearing member  12 . Then, as the developer bearing member  12  is rotated further, the layer of the toner T is regulated in thickness by the development blade  14  while being given a preset amount electrical charge. Consequently, a thin layer of the toner T, which has a preset thickness and a preset amount of electrical charge is formed on the peripheral surface of the developer bearing member  12 . Then, the thin layer of the toner T is conveyed to the development area, that is, the area in which the distance between the peripheral surface of the photosensitive drum  2  and the peripheral surface of the developer bearing member  12  is smallest. The thin layer of toner T is conveyed through the area. While the thin layer of the toner T is conveyed through the development area, development bias is applied to the developer bearing member  12 . Consequently, the toner T is supplied from the developer bearing member  12  onto the peripheral surface of the photosensitive drum  2 , developing thereby the electrostatic latent image on the peripheral surface of the photosensitive drum  2  into a visible image, that is, an image formed of the toner T (which hereafter will be referred to as toner image). 
     Meanwhile, sheets M of recording medium such as paper, OHP film, fabric, or the like, which are in the sheet feeder cassette  3 , are fed into the main assembly of the image forming apparatus A, while being separated one by one from the rest, by the combination of the pickup roller  4  and sheet pressing member  5 . Then, each sheet M of recording medium is conveyed to the transfer roller  6  while being guided by the sheet conveyance guide (unshown). Then, the toner image on the photosensitive drum  2  is transferred onto the sheet M of recording medium by the transfer roller  6 . The toner remaining on the peripheral surface of the photosensitive drum  2  after the transfer is removed, as waste toner, by the cleaning blade  10 , and is stored in the waste toner container  9   a.    
     After the transfer of the toner image onto the sheet M of recording medium, the sheet M is conveyed to the fixing device  7  along the recording medium conveyance guide, and is conveyed through the fixing device  7 . As the sheet M is conveyed through the fixing device  7 , the driving roller  7   a  and fixation roller  7   b  of the fixing device  7  apply heat and pressure to the sheet M and the toner image thereon. Consequently, the toner image is fixed to the surface of the sheet M. Thereafter, the sheet M is conveyed to the pair of discharge rollers  8 , and is discharged from the image forming apparatus A by the pair of discharge roller  8 , ending thereby the image formation operation of the image forming apparatus A. 
     (Structural Arrangement for Attaching Sealing Film) 
     Next, referring to  FIG. 3 , the structural arrangement, in this embodiment, for attaching the sealing film  103  to the development unit frame  13  is described.  FIG. 3  is a perspective view of the development unit frame  13  of the cartridge B. It sequentially shows how the sealing film  103  is attached to the development unit D. More specifically,  FIGS. 3(   a ),  3 ( b ) and  3 ( c ) are schematic perspective views of the development unit frame  13  before, during, and after the attachment of the sealing film  103  to the development unit frame  13 , respectively. 
     Referring to  FIG. 3(   a ), the sealing film  103  is welded to the rim of the developer delivery opening  13   d  of the development unit frame  13 . Here, the portion of the sealing film  103 , by which the sealing film  103  is welded to the development unit frame  13 , is referred to as the rim surface  103   a  of the developer delivery opening  13   d . Next, referring to  FIG. 3(   b ), after the welding of the sealing film  103  to the development unit frame  13 , the sealing film  103  is doubled back in the direction indicated by an arrow mark X at the double-back point (opposite end of development unit frame  13  from where sealing film extraction slit  101  is present), all the way to the lengthwise end where sealing film extraction slit  101  is present, and is extended through the sealing film extraction slit  101  so that the leading end portion  103   c , in terms of the direction in which the sealing film  103  is doubled back, extends outward from the development unit frame  13 , as shown in  FIG. 3(   c ). This is how the sealing film  103  is attached (welded) to the development unit frame  13  to seal the developer delivery opening  13   d.    
     Embodiment 1 
     Structure of Sealing Member 
     Next, referring to  FIGS. 4 and 5 , the sealing member  102  in the first embodiment is described. The sealing member  102  is the second sealing member of the development unit frame  13 . More specifically, the sealing member  102  is for plugging the sealing film extraction slit  101  to prevent the developer in the cartridge B from leaking out through the sealing film extraction slit  101 . The details of the sealing member  102  will be given later. 
       FIG. 4  is a perspective view of the lengthwise end portion of the cartridge B in the first embodiment, from which the sealing film  103  is extended outward from the cartridge B through the sealing film extraction slit  101 , before the cartridge is used for the first time (before sealing film is removed).  FIG. 5  is a schematic sectional view of the sealing member and its adjacencies (part of developer unit frame  13 ) of the cartridge B, in the first embodiment, which is for describing the sealing member  102 . More specifically,  FIG. 5(   a ) is a schematic sectional view of the sealing member  102  and its adjacencies of the development unit frame  13  in the first embodiment, at a vertical plane which coincides with the line P 2  in  FIG. 4 , which is parallel to the lengthwise direction of the cartridge B. It is for describing the sealing member  102 .  FIG. 5(   b ) is a schematic sectional view of the sealing member and its adjacencies of the development unit frame  13  in the first embodiment, at a vertical plane which coincides with the line P 3 -P 3  in  FIG. 4 , which is parallel to the lengthwise direction of the cartridge B. It is for describing the sealing member  102 .  FIG. 5(   c ) is a side view of the development unit frame  13  as seen from the opposite direction from the direction indicated by the arrow mark X. Incidentally, the developer bearing member  12  and development blade  14 , etc., are not shown in  FIG. 5  for the sake of making it easier to describe the sealing member  102 . 
     Before the cartridge B is used for the first time (before sealing film is removed), the developer delivery opening  13   d  remains sealed by the sealing film  103  welded to the development unit frame  13 . In other words, the developer storage chamber  13   b  remains hermetically sealed. Thus, the toner T in the developer storage chamber  13   b  has not been delivered to the development chamber  13   c . When the cartridge B is in the above described state, the end portion  103   c  of the sealing film  103  extends in the direction indicated by the arrow mark X through the sealing film extraction slit  101  as shown in  FIG. 4 . 
     The development unit D in the first embodiment is provided with the development unit sealing member  102  (which hereafter will be referred to simply as sealing member  102 ), which is for preventing the toner T in the developer storage chamber  13   b  from leaking out through the sealing film extraction slit  101 . The sealing member  102  is formed in the sealing film extraction slit  101  by filling the sealing film extraction slit  101  with thermoplastic elastomer. Thus, as the thermoplastic elastomer is filled into the sealing film extraction slit  101 , the sealing member  102  is formed like an integral part of the development unit frame  13 . More specifically, the sealing film extraction slit  101  is filled with thermoplastic elastomer from one end  101   a  to the other  101   c  of the slit  101  in terms of the direction perpendicular to the lengthwise direction of the cartridge B. Thus, the resultant sealing member  102  fills the sealing film extraction slit  101  with the presence of no gap between itself and development unit frame  13 , and also, between itself and sealing film  103 , as shown in  FIG. 5(   b ). 
     Referring to  FIG. 5(   a ), the most upstream end portion of the sealing member  102  in terms of the direction (indicated by arrow mark X) in which the sealing film  103  is extracted is provided with a sealing film scraping portion  109  for scraping away the toner T having adhered to sealing film  103 . A referential code θ in  FIG. 5(   a ) stands for the angle of contact between the upstream surface of the sealing member  102 , and the surface of the sealing film  103 , which is in contact with the sealing member  102 . In this first embodiment, the sealing member  102  is formed so that the angle θ of contact becomes no more than 90° as shown in  FIG. 5(   a ). 
     Next, referring to  FIGS. 5(   a ) and  5 ( b ), the development unit frame  13  is provided with a sealing member retaining member  111 . The upstream end  112  of this retaining member  111 , in terms of the direction (indicated by arrow mark X) in which the sealing film  103  is to be extracted, is in contact with the downstream end  110  of the sealing member  102 . Thus, it does not occur that the sealing member  102  comes out of the sealing film extraction slit  101 . 
     Next, referring to  FIG. 5(   c ), the sealing member retaining member  111  is shaped so that its retaining portion  112  (upstream end portion) fits into the sealing film extraction slit  101 , and also, so that it can be solidly attached to the development unit frame  13  with small screws. However, attaching the sealing member retaining member  111  to the development unit frame  13  as shown in  FIG. 5(   a ) increases the dimension of the cartridge B by an amount equal to the width X 1  of the sealing member retaining member  111 . Further, a gap Z 1  through which the sealing film  103  is extracted from the development unit frame  13  is provided between the bottom surface  111   a  of the sealing member retaining member  111  and the bottom surface  101   h  of the sealing member extraction slit  101 . In order to ensure that the sealing film  103  can be extracted through this gap Z 1 , the sealing member retaining member  111  is formed so that the dimension of the gap Z in terms of the direction perpendicular to the bottom surface of the retaining member  111  is greater than the thickness Z 2  of the sealing film  103 . 
     (Process for Forming Sealing Member) 
     Next, referring to  FIGS. 6-8 , the process for forming the sealing member  102  in this embodiment is described.  FIGS. 6 and 7  are drawings which show the process through which the sealing member  102  in this embodiment is formed. More specifically,  FIGS. 6(   a ),  6 ( b ), and  7 ( a ) are schematic sectional views of the sealing member  102  (or space for sealing member  102 ) and its adjacencies, at a vertical plane which coincides with the line P 2 -P 2  in  FIG. 4 .  FIGS. 6(   c ) and  7 ( b ) are schematic sectional views of the sealing member  102  in this embodiment, at a vertical plane which coincides with the line P 3 -P 3  in  FIG. 4 .  FIG. 8  is a schematic sectional view of the sealing member  102  and its adjacencies, after the removal of the first and second metallic molds after the injection molding of the sealing member  102 . More specifically,  FIG. 8(   a ) is a schematic sectional view of the sealing member  102  at the vertical plane which coincide with the lines P 2 -P 2  in  FIG. 4 , and  FIG. 8(   b ) is a schematic sectional view of the sealing member  102 , at the vertical plane which coincides with the line P 3 -P 3  in  FIG. 4 , as seen from the opposite direction from the direction indicated by the arrow mark X in  FIG. 4 . 
     In the first embodiment, the sealing member  102  is formed in the sealing film extraction slit  101  by injecting thermoplastic elastomer into the sealing film extraction slit  101  after the attachment (welding) of the sealing film  103  to the development unit frame  13 . More concretely, referring to  FIG. 6(   a ), first, in order to remove slack from the sealing film  103  by tensioning the sealing film  103 , force is applied to the end portion  103   c  of the sealing film  103  in the direction indicated by the arrow mark X by an amount which is sufficient to tighten the sealing film  103 , but, is not large enough to cause the sealing film  103  to be peeled from the development unit frame  13 . Then, the first and second metallic molds  105  and  106  are inserted into the sealing film extraction slit  101  while keeping the sealing film  103  tensioned. Thus, a space  107  (mold) for forming the sealing member  103  is formed in the sealing film extraction slit  101  by the first and second metallic molds  105  and  106 , sealing film  103 , and development unit frame  13 . 
     Next, referring to  FIGS. 6(   a ) and  6 ( b ), the first metallic mold  105  has a surface  105   a  which is for forming the abovementioned sealing member formation space  107 , more specifically, for forming the sealing film scraping portion (edge) of the sealing member  102 . The first metallic mold  105  is shaped so that the angle θ between this surface  105   a  for forming the sealing film scraping portion of the sealing member  102 , and the sealing film  103  becomes no more than 90°. The second metallic mold  106  is provided with a surface  106   a , which is for forming the abovementioned sealing member formation space  107 , more specifically, for forming the surface of the sealing member  102 , which comes into contact with the sealing member retaining member  111 . Next, referring to  FIG. 6(   c ), designated by a referential code  101   e  is the top surface of the sealing film extraction slit  101 , that is, the opposite surface of the sealing film extraction slit  101  from the surface of the sealing film extraction slit  101 , which is in contact with the sealing film  103 . In other words, the sealing member formation space  107  is formed by the surface  105   a  for forming the sealing film scraping portion of the sealing member  102 , surface  106   a  for forming the surface of the sealing member  102 , which comes into contact with the sealing member retaining member  111 , top surface  101   e  of the sealing film extraction slit  101 , surface  103   a  of the sealing film  103 , which faces upward, first lateral surface  101   f  of sealing film extraction slit  101 , and second lateral surface  101   g  of sealing film extraction slit  101 . 
     Referring to  FIG. 6(   a ), the second metallic mold  106  is provided with an injection nozzle  108  for injecting thermoplastic elastomer into the sealing member formation space  107 , in the opposite direction from the direction indicated by the arrow mark X; thermoplastic elastomer is flowed into the sealing member formation space  107  from the tip  108   a  of the injection nozzle  108 , as shown in  FIG. 6(   b ). As the thermoplastic elastomer is injected into the sealing member formation space  107 , it flows in the direction indicated by the arrow mark Y, into the corners  101   a - 101   d  of the sealing member formation space  107  in the sealing film extraction slit  101 , while filling up the sealing member formation space  107 , as shown in  FIG. 6(   c ). 
     Consequently, the sealing member  102  is formed in the sealing member formation space  107 , leaving no gap between itself and the aforementioned surfaces (surrounding walls) as shown in  FIGS. 7(   a ) and  7 ( b ). That is, even if the corners  101   a - 101   d , etc., of the sealing member formation space  107  in the sealing film extraction slit  101  are imperfect in shape (superficial texture) because of manufacture errors and the like, thermoplastic elastomer is filled into the sealing member formation space  107  in a manner to accommodate the imperfections. In other words, in the first embodiment, the sealing member  102  is formed in the sealing member formation space  107 , leaving no gap between itself and the walls of the sealing member formation space  107 , as if it becomes an integral part of the development unit frame  13 . That is, the sealing member  102  is enabled to remain stable in shape, as shown in  FIGS. 8(   a ) and  8 ( b ), even after the removal of the first and second metallic molds  105  and  106 . 
     Incidentally, it is desired that the primary monomer among the monomers of which the development unit frame  13  is formed is included in the material for the sealing member  102 . That is, it is desired that the thermoplastic elastomer as the material for the sealing member  102  is similar in properties to the material for the development unit frame  13 , for the reason that in a case where the material for the sealing member  102  is similar in properties to the material for the development unit frame  13 , the sealing member  102  does not need to be separated from the development unit frame  13  when recycling the used cartridge B as the thermoplastic material. In the first embodiment, the development unit frame  13  is formed of high impact polystyrene, and the sealing member  102  is formed of thermoplastic elastomer, the primary ingredient of which is styrene. However, this embodiment is not intended to limit the present invention in terms of the material for the sealing member  102 . That is, the present invention is compatible with any sealing member ( 102 ) as long as the sealing member is similar in mechanical properties to the sealing member  102  in this embodiment, even if the sealing member ( 102 ) is different in material (resin) from the sealing member  102  in this embodiment. 
     (Function of Sealing Member) 
     Next, referring to  FIG. 8 , the function of the sealing member  102  in this embodiment is described. Before the cartridge B is used for the first time, the developer delivery opening  13   d  of the development unit frame  13  remains sealed with the sealing film  103 . Thus, the portion of the surface of the sealing film  103 , which has been facing the developer storage chamber  13   b  is covered with toner T. When the cartridge B is used for the first time, the sealing film  103  has to be removed by a user; as the sealing film  103  is pulled by the user, by the end portion  103  of the sealing film  103 , which is exposed from the development unit frame  13  through the sealing film extraction slit  101 , in the direction indicated by the arrow mark X as shown in  FIG. 8(   a ), the sealing film  103  comes out of the development unit frame  13  through the sealing film extraction slit  101 . As the sealing film  103  welded to the development unit frame  13  is pulled, the sealing film  103  gradually peels away from the development unit frame  13 , starting from its double-back point  103   b . As the sealing film  103  peels away, the portion  103   a  of the surface of the sealing film  103 , which was facing inward of the developer storage chamber  13   b , and therefore, is covered with the toner T, rubs against the sealing film scraping portion (edge)  109  of the sealing member  102 , whereby the toner T on the sealing film  103  is scraped away from the film  103 . Therefore, it does not occur that as the sealing film  103  is pulled out of the development unit frame  13  through the sealing film extraction slit  101 , the toner T having adhered to the sealing film  103  leaks from (comes out of) the development unit frame  13 . 
     Next, referring to  FIG. 9 , how the toner T on the sealing film  103  is scraped away is described.  FIG. 9  is a drawing for describing the function of the sealing member  102  in terms of scraping away the toner T on the sealing film  103 .  FIG. 9(   a ) is an enlarged schematic sectional view of the sealing film scraping portion (edge)  119  ( 119   a ) of a sealing member  121 , the angle θ of contact of which relative to the sealing film  103  is no less than 90°  FIG. 9(   b ) is an enlarged schematic sectional view of the sealing film scraping portion  109  ( 109   a ) of the sealing member  102 , the angle θ of contact of which relative to the sealing film  103  is no more than 90°, that is, the sealing film scraping portion of the sealing member  102  in this embodiment. In  FIG. 9 , the dotted lines indicate the contours of the sealing members  120  and  102  before the sealing film  103  begins to be pulled in the direction indicated by the arrow mark X, whereas the hatched areas indicate the shape of the sealing members  120  and  102  after the sealing film  103  began to be pulled in the arrow X direction. Referring to  FIG. 9(   a ), a referential code  120  stands for the upstream surface of the sealing member  102  in terms of the direction in which the sealing film  103  is extracted, and a referential code  119  stands for the film scraping portion (scraping edge) of the sealing member  102 . Further, referential codes  119   a  and  120   a  stand for the film scraping portion (edge) and upstream surface  120   a  of the sealing member  121  after the sealing film  103  began to be pulled in the direction of the arrow mark X. 
     As the sealing film  103  is pulled in the direction of the arrow mark X by the tension applied to the sealing film  103  in order to extract the sealing film  103 , the sealing film scraping portion  109  is subjected to the shearing stress generated between the sealing film scraping portion  109  and sealing film  103 . Referring to  FIG. 9(   a ), if the angle θ of contact between the sealing film scraping portion  119  and sealing film  103 , that is, the angle between the upstream surface  120  and sealing film  103 , is no less than 90°, the sealing film scraping portion  119  of the sealing member  121  buckles downstream in terms of the direction in which the sealing film  103  is pulled. As the sealing film scraping portion  119   a  buckles as described above, the upstream surface  120   a  of the sealing member  121  comes into contact with the sealing film  103 . Hereafter, this phenomenon will be referred to as “belly buckling”, of the sealing member  121 . As the “belly-buckling” occurs to the sealing film scraping portion  119   a  of the sealing member  121 , the sealing film scraping portion (edge)  119   a  stops contacting the sealing film  103 . Consequently, the sealing member  103  reduces in performance in terms of its function of scraping away the toner T from the sealing film  103 . In other words, the sealing member  121  fails to completely scrape away the toner T having adhered to the sealing film  103 . 
     In comparison, referring to  FIG. 9(   b ), in the case of the sealing member  102  in this embodiment, which is no more than 90° in the angle θ of contact between its sealing film scraping portion  109  and the sealing film  103 , the shearing stress friction between the sealing film scraping portion  109  and sealing film  103  works in the direction of pressing the sealing film scraping portion  109  toward the upstream surface  118  of the sealing member  102 . Therefore, it does not occur that the sealing film scraping portion  109  buckles downstream. That is, in the case of the sealing member  102  in this embodiment, its sealing film scraping portion  109  does not buckle downstream when the sealing film  103  is extracted from the development unit frame  13 . In other words, the “belly buckling” does not occur. Therefore, the sealing film scraping portion (edge)  109   a  of the sealing member  102  in this embodiment remains perfectly in contact with the sealing film  103 ; the sealing member  102  in this embodiment remains stable in terms of its function of scraping the toner T having adhered to the sealing film  103 . 
     As described above, in order for the sealing member  102  to be effective to prevent the toner T from leaking out of the development unit frame  13  through the sealing film extraction slit  101 , the angle θ of contact between the sealing film scraping portion  109  of the sealing member  102  is desired to be no more than 90°. 
     Next, referring to  FIG. 10 , the state of the development unit frame  13  after the extraction of the sealing film  103  from the development unit frame  13  is described.  FIG. 10  is a schematic sectional view of the sealing member  102  and its adjacencies, at the vertical plane which coincides with the line P 2 -P 2  in  FIG. 4 , after the removal of the sealing film  103 . It shows the state of the sealing member  102  after the removal of the sealing film  103 . The sealing member  102  is kept in the sealing film extraction slit  101  even after the extraction of the sealing film  103  from the development unit frame  13 , as shown in  FIG. 10 . Therefore, it can prevent the toner T from leaking through the sealing film extraction slit  101  even while the cartridge B is being used for image formation. 
     As described above, in the first embodiment, the problem that the toner T leaks from the development unit frame  13  through the sealing film extraction slit  101  is prevented with the use of the sealing member  102 . Further, the sealing member  102  in the first embodiment is formed in such a manner that as it is formed, it becomes a virtually integral part of the development unit frame  13 . Therefore, it is ensured that the toner T having adhered to the sealing film  103  is satisfactorily scraped away by the sealing member  102 . 
     (Comparison of Sealing Member in First Embodiment with Sealing Member Different in Structure from Sealing Member in First Embodiment) 
     Here, in order to verify the effectiveness of the sealing member  102  in the first embodiment of the present invention, the sealing member  102  in this embodiment was compared with a comparative sealing member  902 , which is shown in  FIGS. 22(   a ),  22 ( b ) and  22 ( c ). The comparative sealing member  902  is different from the sealing member  102  in this embodiment in that it is formed before it is inserted into the sealing film extraction slit  101 . 
     In the case where the sealing member extraction slit  101  of the development unit frame  13  is plugged with the abovementioned comparative sealing member  902 , the sealing member  902 , which has fins  902   b , has to be inserted into the sealing film extraction slit  101  in such an attitude that the fins  902   b  come into contact with the sealing film  103 . Thus, when the cartridge B (development unit frame  13 ) is assembled, the sealing member  902  has to be placed in the proper attitude. 
     Moreover, in the case where the development unit frame  13  is structured so that the preformed sealing member  902  is to be inserted into the sealing film extraction slit  101  of the development unit frame  13 , the process for manufacturing the sealing member  902  and sealing film extraction slit  101  have to be strictly controlled in terms of the measurement of the sealing member  902  and sealing film extraction slit  101 , in order to ensure that the developer does not leak from the development unit frame  13  at the corner portions  101   a - 101   d  of the sealing film extraction slit  101  shown in  FIG. 23 . Thus, it is possible that using the preformed sealing member  902  to plug the sealing film extraction slit  101  and scrape the sealing film  103  adds to the cartridge cost. 
     In comparison, in the case where the development unit frame  13  and sealing member  102  are structured as they are in this embodiment, the process for inserting the sealing member  102  into the sealing film extraction slit  101  is unnecessary. In other words, the sealing member  102  in this embodiment is superior to the comparative sealing member  109  in terms of the productivity of the process of manufacturing the process cartridge B. Further, the sealing member  102  conforms to the shape of the sealing film extraction slit  101  as it is formed. Therefore, it does not need to be preformed with such an accuracy that it perfectly matches in measurement with the sealing film extraction slit  101 . That is, the process for manufacturing the cartridge B (development unit frame  13 ) does not need to be strictly controlled in terms of the measurement of the sealing member  102  and sealing film extraction slit  101 . Therefore, this embodiment can improve in productivity the process for manufacturing the cartridge B (development unit frame  13 ), and also, reduce the cartridge B (development unit frame  13 ) in cost. 
     Embodiment 2 
     Next, referring to  FIGS. 11 and 12 , the development unit frame  13  and sealing member in the second embodiment of the present invention are described.  FIG. 11  is a perspective view of the end portion of the development unit frame  13  in the second embodiment of the present invention, which has the sealing film extraction slit  101 . It shows the end portion before the cartridge is used for the first time.  FIG. 12  is a schematic sectional view of the downstream end portion of the development unit frame  13  in terms of the direction in which the sealing film  103  is pulled out of the cartridge B, at the vertical plane which coincides with the line P 2 -P 2  in  FIG. 11 . It shows the structure of the sealing member in the second embodiment. The components, portions, etc., of the development unit frame  13  in this embodiment, which are the same in structure as the counterparts in the first embodiment, are given the same referential codes as those given to the counterparts, and are not going to be described here. 
     Referring to  FIG. 11 , in the second embodiment, the sealing film  103  is welded (adhered) to the development unit frame  13  to cover the developer delivery opening  13   d  of the development unit frame  13 , and is doubled back at the opposite end of the developer delivery opening  13   d  from the sealing film extraction slit  101 , extended to the sealing film extraction slit  101 , and extended out of the development unit frame  13  by a preset length, through the sealing film extraction slit  101 , in the direction indicated by an arrow mark X, as in the first embodiment. Next, referring to  FIG. 12 , the sealing member  202  in the second embodiment is shaped so that the angle θ of contact becomes no more than 90° like that of the sealing member  102  in the first embodiment. 
     Referring to  FIGS. 11 and 12 , in the second embodiment, the development unit frame  13  is provided with an injection hole  204 , which leads to the sealing member formation space which is to be filled with the material for the sealing member  102 . Referring to  FIG. 11 , a line P 2 -P 2  coincides with the center of the injection hole  204  and parallel to the lengthwise direction of the cartridge B. Referring to  FIG. 12 , designated by a referential code  202  is a sealing member formed by filling the sealing member formation space and injection hole  204  with the material for the sealing member  202 . The portion of the sealing member  202 , which is in the injection hole  204 , will be referred to as a sealing member locking portion  212  (which hereafter may be referred to simply as locking portion  212 ). The locking portion  212  prevents the sealing member  102  from dropping out of the sealing film extraction slit  101  of the development unit frame  13 . 
     Referring to  FIG. 12 , the sealing member locking portion  212 , which is a part of the sealing member  202  is formed in the injection hole  204 . When the sealing film  103  is pulled out of the development unit frame  13 , the shearing stress generated between the sealing film scraping portion  209  and sealing film  103  acts on the sealing film scraping portion  209 . That is, the sealing member  202  is pressed outward of the development unit frame  13  by this shearing stress. In the second embodiment, however, the sealing member locking portion  212  of the sealing member  202  comes into contact with the wall  204   a  of the injection hole  204 , preventing thereby the sealing member  202  from being moved out of the sealing film extraction slit  101 . That is, the injection hole  204  is a hole with which the development unit frame  13  is provided to regulate the movement of the sealing member  202 ; because the sealing member locking portion  212  of the sealing member  202  is in the injection hole  204 , the sealing member  202  is prevented from moving. 
     Next, referring to  FIG. 13 , the process for forming the sealing member  202  in the second embodiment is described.  FIGS. 13(   a ),  13 ( b ) and  13 ( c ) are sectional views of the lengthwise end portion of the development unit frame  13 , which has the sealing film extraction slit  101  and sealing member  202 . They are for describing the process for forming the sealing member  202  in the second embodiment. Referring to  FIG. 13(   a ), before the sealing member  202  is formed by injection molding, the sealing film  103 , which has been welded to the development unit frame  13 , is kept tensioned by a preset amount pressure applied to the outward end  103   c  of sealing film  103  in the direction indicated by an arrow mark X, while keeping sealed the developer delivery hole  13   d . While the development unit frame  13  is kept in this state, the first and second metallic molds  205  and  206  are inserted into the sealing film extraction slit  101  to form the sealing member formation space (mold)  207 . Referring also to  FIG. 13(   a ), the sealing member formation space (mold)  207  is formed by the surface  205   a  for forming the sealing film scraping portion of the sealing member  202 , surface  206   a  for forming the downstream end surface of the sealing member  202  in terms of the direction in which the sealing film  103  is extracted, top surface  101   e  of the sealing film extraction slit  101 , surface  103   a  of the sealing film  103 , which faces upward; first lateral surface  101   f  of sealing film extraction slit  101 , second lateral surface  101   g  of sealing film extraction slit  101 , and injection hole  204 . Here, the first and second lateral surfaces  101   f  and  101   g  of the sealing film extraction slit  101  are the same as the counterparts in the first embodiment, which are shown in  FIG. 6(   c ). 
     Referring to  FIG. 13(   b ), as thermoplastic elastomer is injected through the injection nozzle  208  in the direction indicated by an arrow mark Z, thermoplastic elastomer is filled into the sealing member formation space  207  from the tip  208   a  of the injection nozzle  208 . Next, referring to  FIG. 13(   c ), as the thermoplastic elastomer is injected into the sealing member formation space  207 , it fills up the sealing member formation space  207 , forming the sealing member  202 , leaving no gap between the sealing member  202  and the aforementioned surfaces. That is, the sealing member  202  is formed as a virtually integral part of the development unit frame  13 . 
     As described above, in the second embodiment, the sealing member  202  is used to prevent the toner T from leaking through the sealing film extraction slit  101 . Further, the sealing member  202  in the second embodiment is formed as a virtually integral part of the development unit frame  13 . Therefore, it is ensured that the toner T having adhered to the sealing film  103  is satisfactorily scraped away by the sealing member  202 . Further, the process for manufacturing the development unit frame  13  (cartridge B) does not need to be extremely precisely controlled in terms of the measurement of the sealing member  202  and sealing film extraction slit  101 . Thus, this embodiment of the present invention also can improve in productivity the process for manufacturing the cartridge B, and reduce in cost the cartridge B. Further, the sealing member  202  in the second embodiment is provided with the sealing member locking portion  212 , making unnecessary the sealing member retaining member  111  (which is independent from development unit frame  13 ) used in the first embodiment. Thus, the developer unit D (cartridge B) in the second embodiment is shorter by an amount equal to the width X 1  of sealing member retaining member  111  ( FIG. 5(   a )), and also, is less in cost, than the development unit D (cartridge B) in the first embodiment. 
     Embodiment 3 
     Next, referring to  FIG. 14 , the sealing member and development unit frame in the third embodiment of the present invention are described.  FIGS. 14(   a ),  14 ( b ) and  14 ( c ) are drawings for describing the sealing member and development unit frame  13  in the third embodiment. More specifically,  FIG. 14(   a ) is a schematic sectional view of the development unit frame  13  and sealing member in the third embodiment, and  FIG. 14(   b ) is a schematic perspective view of the sealing member in the third embodiment.  FIG. 14(   c ) is a schematic sectional view of the development unit frame  13  and sealing member in the third embodiment, at a vertical plane which coincides with a line P 4 -P 4  in  FIG. 14(   a ). The structural components, portions thereof, etc., of the development unit frame  13  and sealing member in the third embodiment, which are the same in structure as the counterparts in the first or second embodiment are given the same referential codes as those given to the counterparts, and are not going to be described here. 
     Referring to  FIG. 14(   a ), in the third embodiment, the portion of the sealing film  103 , which was not welded to the development unit frame  13  is doubled back (folded back) at the opposite end of the development unit frame  13  from where the sealing film extraction slit  101  is present, is laid on the portion of the sealing film  103 , which is covering the developer delivery opening  13   d , in the direction indicated by an arrow mark X, and is extended outward of the development unit frame  13  through the sealing film extraction slit  101 , so that the end portion  103   c  of the sealing film  103  is exposed from the development unit frame  13 , like the sealing film  103  in the first embodiment. Further, the sealing member  302  in the third embodiment also is shaped so that its angle θ of contact becomes no more than 90°, like the sealing member  102  in the first embodiment. Further, the sealing member  302  in the third embodiment is formed as a virtually integral part of the development unit frame  13 , by injection molding thermoplastic elastomer, like the sealing member  102  in the first embodiment. Thus, the sealing member  302  in the third embodiment also occupies the sealing member formation space even to the corners  101   a - 101   d  of the sealing member formation space. In other words, thermoplastic elastomer fills the sealing member formation space (mold) to the corners  101   a - 101   d  of the sealing member formation space (mold), regardless of the imperfection in the surface texture of the surfaces (walls) which form the sealing member formation space; the resultant sealing member  302  fits in the sealing film extraction slit  101 , with the presence of no gap between itself and the walls of the sealing film extraction slit  101 . 
     Further, the sealing member  302  in this embodiment is directly molded into the sealing film extraction slit  101  and injection hole  304 , in a manner similar to the manner in which the sealing member  202  in the second embodiment was directly molded into the sealing film extraction slit  101 . Thus, the sealing member locking portion  312  of the sealing member  302 , which is formed in the injection hole  304  can prevent the sealing member  302  from falling out of the development unit frame  13  through the sealing film extraction slit  101 , because when the sealing film  103  is pulled out of the development unit frame  13  through the sealing film extraction slit  101 , the sealing member locking portion  312  prevents the sealing member  302  from moving in the direction indicated by the arrow mark X, by coming into contact with the wall  304   a  of the injection hole  304 . 
     Referring to  FIG. 14 , the sealing member  302  in the third embodiment has the sealing member locking second portion  315  in addition to the above described structural features. Referring to  FIG. 14(   b ), the sealing member locking second portion  315  has end portions  315   a  and  315   b , and bottom portion  315   c . Next, referring to  FIG. 14(   a ), the sealing member locking portion  315  is formed by injecting the thermoplastic elastomer into the through hole  316 , which the development unit frame  13  is provided; the sealing member locking portion  315  is in the through hole  316 . The sealing member locking portion  315  prevents the sealing member  302  from coming out of the sealing film extraction slit  101  when the sealing film  103  is pulled out of the development unit frame  13 . Further, it is in contact with the side walls of the hole  316   a  of the development unit frame  13 . Therefore, the reaction from the side wall surface  316   a  prevents the film scraping portion (edge) of the sealing member  302  from buckling downstream as shown in  FIG. 9(   a ). In other words, the reaction prevents the angle θ of contact from being increased. Therefore, the sealing film scraping portion  309  can scrape the toner T, with its angle θ of contact relative to the sealing film  103  remaining to be no more than 90°. Thus, it is ensured that the toner T is satisfactorily scraped away when the sealing film  103  is pulled out of the development unit frame  13 . 
     As described above, in the third embodiment, the sealing member  302  was used to prevent the toner T from leaking out of the development unit frame  13  through the sealing film extraction slit  101 . Further, the sealing member  302  in the third embodiment is formed as a virtually integral part of the development unit frame  13 . Therefore, it is ensured that the toner T having adhered to the sealing film  103  is satisfactorily scraped away by the sealing member  302 . Further, the third embodiment makes it unnecessary to strictly control the process for manufacturing the development unit frame  13  (cartridge B) in terms of the measurement of the sealing member  302  and sealing film extraction slit  101 . Thus, this embodiment of the present invention also can improve in productivity the process for manufacturing the cartridge B, and reduce in cost the cartridge B. Further, the sealing member  302  in the third embodiment is provided with the sealing member locking portion  312 , making unnecessary the sealing member retaining member  111  (which is independent from development unit frame  13 ) used in the first embodiment. Thus, the development unit frame  13  in the third embodiment is shorter, and also, less in cost, than the development unit frame  13  in the first embodiment. Further, the sealing member  302  in the third embodiment has the sealing member locking second portion  315 , which can prevent the angle θ of contact from increasing when the sealing film  103  is pulled out of the development unit frame  13 . Therefore, it is ensured that the sealing member  302  in the third embodiment can satisfactorily scrape the toner T from the sealing film  103 . 
     Embodiment 4 
     In the case of each of the first to third embodiments, in order to increase in efficiency the process for attaching the sealing member to the cartridge B, the sealing member is molded into the sealing film extraction slit  101  by injecting the thermoplastic elastomer into the sealing film extraction slit  101 . 
     This embodiment is different from the preceding embodiments described above in that the sealing member  702  in this embodiment is molded before it is inserted into the sealing film extraction slit  101 . That is, this embodiment is about how to simplify the process for assembling the cartridge B (development unit frame  13 ) which uses a preformed sealing member. The characteristic feature of this embodiment is that the sealing member locking member for preventing the sealing member  702  from coming out of the sealing film extraction slit  101  is formed as an integral part of the sealing member  702 , although the details of the sealing member  702  will be described later. 
     (Structure of Sealing Member) 
     Referring to  FIGS. 15 and 16 , the structure of the sealing member  702  in this embodiment is described. 
     First, referring to  FIG. 2 , until the cartridge B is used for the first time, the developer delivery opening  13   d  of the development unit frame  13  is kept sealed with the development unit sealing film  103 , which was welded to the rim  13   a  of the developer delivery opening  13   d . Therefore, the toner T remains hermitically sealed in the developer storage chamber  13   b . In other words, until the cartridge B is used for the first time, there is no toner in the development chamber  13   c.    
       FIG. 15(   a ) is a perspective view of the development unit frame  13 , developer storage chamber sealing film  103 , and sealing member locking portion  702   e  of the development unit frame  13 , before the cartridge B is used for the first time. In order to make it easier to describe the structure of the sealing member  702 ,  FIG. 15  does not show the aforementioned developer bearing member  13 , development blade  14 , etc. 
     Referring to  FIG. 15(   a ), the portion of the developer storage chamber sealing film  103   d , which was not welded to the development unit frame  13 , is doubled (folded) back at the opposite end of the developer delivery opening  13   d  from where the sealing film extraction slit  101  is present, is extended in the direction indicated by an arrow mark X, is put though the sealing film extraction slit  101 , and is extended outward of the development unit frame  13 , leaving its end portion  103   c  exposed from the development unit frame  13 . 
     A referential code P 2  in  FIG. 15(   a ) stands for such a line that is parallel to the lengthwise direction of the development unit frame  13 , and also, that coincides with the center of the injection hole  104  in terms of the widthwise direction of the development unit frame  13 .  FIG. 15(   b ) is a partially exploded perspective view of the lengthwise end portion of the development unit frame  13 , in which the sealing member  702  is inserted. The sealing member  702  is inserted into the sealing film extraction slit  101 , with the developer storage chamber sealing film  103  being kept flat by being pulled in the direction indicated by the arrow mark X, as will be described later. 
       FIG. 16  is a schematic sectional view of the sealing member  702  and its adjacencies, at a vertical plane which coincides with the line P 2 -P 2  in  FIG. 15(   a ), when the sealing member  702  is properly positioned in the sealing film extraction slit  101 . Referring to  FIG. 16 , there is the developer delivery opening sealing film  103  in the sealing film extraction slit  101 , and the end portion  103   c  of the sealing film  103  is exposed from the development unit frame  13 . There is also the sealing member  702  in the sealing member extraction slit  101 . The sealing member  702  is provided with fins  207   b  for wiping away the toner T having adhered to the sealing film  103 , and a sealing member locking portion  702   c  for preventing the sealing member  702  from coming out of the sealing film extraction slit  101  when the sealing film  103  is pulled out of the development unit frame  13 . 
     Further, the sealing member  702  has a base portion  702   a  which supports the abovementioned fins  702   b  and sealing member locking portion  702   e . The fins  702   b  are the portions of the sealing member  702 , against which the sealing film  103  rubs when the film  103  is pulled out of the development unit frame  13 , that is, the portions of the sealing member  702 , which wipe away the developer (toner T) on the sealing film  103 . The fins  702   b  are flexible as will be described later. Further, the fins  702   b  are on the opposite side of the base portion  702   a  from the sealing member locking portion  702   e.    
     Next, referring to  FIG. 15(   b ), a referential code Y 1  stands for the dimension of the sealing member  702  in terms of the direction indicated by an arrow mark Y, and a referential code Y 2  stands for the dimension of the sealing member locking portion  702   e  in terms of the direction indicated by the arrow mark Y. The dimension (width) Y 2  of the sealing member locking portion  702   e  is less than the dimension (width) Y 1  of the base portion  702   a.    
     Next, referring to  FIG. 16 , a referential code θ stands for the angle (of contact) between the sealing film wiping edge portion of each fin  702   b , and the surface  103   a  of the developer storage chamber sealing film  103 , which was facing inward of the developer storage chamber  13   b.    
     Referring to  FIG. 16 , the sealing member  702  in this embodiment is provided with multiple fins  702   b , as its sealing film wiping portions, which contact the surface  103   a  of the sealing film  103 , which was facing inward of the developer storage chamber  13   b . When the sealing member  702  is in the sealing member extraction slit  101 , the fins  702   b  remain elastically bent in such a manner that their film wiping edges are on the downstream side of their base portions in terms of the direction indicated by the arrow mark X. The sealing member locking portion  702   e  is in the form of a protrusion, and protrudes from the base portion  702   a . As the sealing member  702  is inserted into the sealing member extraction slit  101 , the sealing member locking portion  702   e  fits into the hole  104  (which may be referred to as sealing member locking hole, hereafter), which is in the top wall of the sealing member extraction slit  101 , and remains fitted in the hole  104  while the sealing member  702  is in the sealing film extraction slit  101 . During the extraction of the developer storage chamber sealing film  103  from the development unit frame  13 , the sealing film  103  rubs against the film wiping portions  702   b   2 , and therefore, the film wiping portions  702   b   2  are subjected to shearing stress directed as indicated by the arrow mark X, being pulled in the direction of the arrow mark X. As the sealing member  702  is pulled in the direction indicated by the arrow mark X, the downstream wall of the sealing member locking portion  702   e  comes into contact with the upstream wall  104   a  of the sealing member locking hole  104 , preventing thereby the sealing member  702  from coming out of the sealing film extraction slit  101  in the direction indicated by the arrow mark X. That is, the sealing member locking hole  104 , that is, the hole in which the sealing member locking portion  702   e  fits, functions as the portion of the development unit frame  13 , which prevents the sealing member  702  from moving in the direction in which the developer storage chamber sealing film  103  is pulled. 
     The sealing member  702  in this embodiment is formed of thermoplastic elastomer, separately from the development unit frame  13 , and is inserted into the sealing film extraction slit  101 . If the sealing member  702  is formed of the same type of thermoplastic elastomer as the one for the development unit frame  13 , the sealing member  702  does not need to be separated from the development unit frame  13  when the development unit frame  13  (cartridge B) is recycled as the material for the development unit frame  13 . Thus, it is desired that the sealing member  702  is formed of the same type of thermoplastic elastomer as that for the development unit frame  13 . In this embodiment, therefore, the development unit frame  13  is formed of high impact polystyrene, and the sealing member  702  is formed of thermoplastic elastomer which belongs to a styrene group. The material for the sealing member  702  may be different from the above described one, as long as it is similar in mechanical properties as the material for the sealing member  702  in this embodiment. Next, the process through which the sealing member  702  is inserted into the sealing film extraction slit  101  is described. 
     (Process for Inserting Sealing Member into Sealing Film Extraction Slit) 
     The process for inserting the sealing member  702  into the sealing film extraction slit  101  is described with reference to  FIGS. 16 and 18 . 
       FIGS. 18(   a )- 18 ( c ) are schematic sectional views of the combination of the sealing member  702  and sealing film extraction slit  101 , at a vertical plane which coincides with the line P 2 -P 2  in  FIG. 15 , before, at the start of, and after the insertion of the sealing member  702  into the sealing film extraction slit  101 , respectively. 
     Referring to  FIG. 18(   a ), before the developer delivery opening sealing member  702  is inserted into the sealing film extraction slit  101 , such force that is large enough to tension the sealing film  103 , but, not large enough to cause the sealing film  702  to peel from the development unit frame  13 , is applied to the end portion  103   c  of the sealing film  103  in the direction indicated by an arrow mark X, in order to rid the sealing film of slack. Next, referring to  FIG. 18(   b ), the sealing member  702  is provided with six fins  702   b , which are the same in shape. 
     Each fin  702   b  has the upstream surface  702   b   1 , in terms of the direction indicated by the arrow mark X, and the film wiping portion (edge)  702   b   2  for wiping away the toner T having adhered to the surface of the developer delivery opening sealing member  103 , which was facing inward of the developer storage chamber  13   b . Further, each fin  701   b  has the base portion  702   b , by which the fin  702   b  is held to the base portion  702   a , and the downstream surface  702   b   4  in terms of the direction indicated by the arrow mark X. In addition, the sealing member locking portion  702   e  of the sealing member  702  has the upstream surface  702   e   1  in terms of the direction indicated by the arrow mark X, top surface  702   e , and downstream surface  702   e   3  in terms of the direction indicated by the arrow mark X. Further, the sealing member locking portion  702   e  has the base portion  702   e   4  by which the sealing member locking portion  702   e  is held to the base portion  702   a  of the sealing member  702 . Further, the base portion  702   a  of the sealing member  702  has the bottom combination made up of the downwardly facing surface  702   c  of the base portion  702   a  and the base portions  702   b   3  of the fins  702   b , and bottom combination  702   g  made up of the top surface  702   f  and base portions  702   e   4  of the base portion  702   a . The top surface  101   e   2  of the sealing film extraction slit  101 , top surface  702   f  of the base portion  702   a , and the downward facing surface  702   c  of the base portion  702   a  are roughly parallel to each other. 
     Referring to  FIG. 18(   b ), when the sealing member  702  is inserted into the sealing film extraction slit  101  in the opposite direction from the direction indicated by the arrow mark X, it is the upstream surface  702   h  of the base portion  702   a , in terms of the direction indicated by the arrow mark X that enters the sealing film extraction slit  101  first. As the sealing member  702  enters the sealing member extraction slit  101 , the fin  702   j   1 , which is the most upstream fin in terms of the direction indicated by the arrow mark X, first comes into contact with the surface  103   a  of the sealing film  103 , which is facing inward of the developer storage chamber  13   b , and is gradually bent downstream. As the fin  702   b  is bent downstream, the film wiping portion  702   b  of the sealing film  103  is subjected to the reaction force generated in the direction indicated by an arrow mark Z by the bending of the fin  702   b , by the surface  103   a  of the sealing film  103 , which is facing inward of the developer storage chamber  13   b . As the sealing member  702  is inserted further into the sealing film extraction slit  101  in the opposite direction from the direction indicated by the arrow mark X, the fins  702   j   2  and  702   j   3 , that is, the downstream fins relative to the most upstream fin  702   j   1 , sequentially come into contact with the surface  103   a  of the sealing film  103 , which is facing inward of the developer storage chamber  13   b , and are sequentially bent in the downstream direction indicated by the arrow mark X. Just about the time when the fin  702   j   3  comes into contact with the surface  103   a  of the sealing film  103 , the upstream surface  702   e   1  of the base portion  702   a  of the sealing member  702  comes into contact with the outward edge  101   i  of the sealing film extraction slit  101 . Then, as the sealing member  702  is inserted further into the sealing film extraction slit  101 , the upstream surface  702   e   1  of the base portion  702   a  of the sealing member  702  is guided in the opposite direction from the direction indicated by the arrow mark X while rubbing the outward edge  101   i  of the sealing film extraction slit  101 . Therefore, the fins  702   j   1 - 702   j   3 , which are already in the sealing film extraction slit  101  and bent, are further bent by an amount equivalent to an amount (height) Z 3  shown in  FIG. 18   b ), increasing the abovementioned reaction force. 
     The height (vertical dimension in  FIG. 18(   b )) of the fins  702   j   1 - 702   j   3  are substantially greater than that of the sealing member locking portion  702   e . Therefore, even though the sealing member locking portion  702   e  protrudes upward from the base portion  702   a  of the sealing member  702 , the sealing member  702  can be inserted into the sealing film extraction slit  101  by bending the fins  702   j   1 - 702   j   3 . 
     Next, referring to  FIG. 18(   c ), as the sealing member  702  is inserted further into the sealing film extraction slit  101  in the opposite direction from the direction indicated by the arrow mark X, the fins  702   j   4 - 702   j   6 , which are on the downstream side of the sealing member locking portion  702   e  in terms of the direction indicated by the arrow mark X sequentially come into contact with the surface  103   a  of the sealing film  103 , which is facing inward of the developer storage chamber  13   b , and are gradually bent downstream in terms of the direction indicated by the arrow mark X. Thus, the film wiping portions  702   b   2  are under the reaction force from the surface  103   a  of the sealing film  103 , generated in the direction indicated by the arrow mark Z by the bending of the fins  702   b . Thus, the top surface  702   e  of the base portion  702   a  of the sealing member  702  is placed, and kept in contact, with the top surface  101   e  of the sealing film extraction slit  101 , by this reaction force. Therefore, the base portion  702   a  becomes, and remains, roughly parallel to the top surface  101   e  of the sealing film extraction slit  101 . Thus, while the sealing member  702  is inserted further into the sealing film extraction slit  101 , the top surface  702   e   2  of the sealing member  702  continue to rub the top surface  101   e  of the sealing film extraction slit  101 , and the film wiping portions  702   b   2  of the fins  702   b  of the sealing member  702  continues to rub the surface  103   a  of the developer storage opening sealing film  103 , which is facing inward of the developer storage chamber  13   b . As the sealing member  702  is inserted further into the sealing film extraction slit  101 , the top surface  702   e   2  of the sealing member locking portion  702   e  becomes separated from the top surface  101   e  of the sealing film extraction slit  101 , because of the presence of the sealing member locking hole  104  in the top wall of the sealing film extraction slit  101 . Thus, the sealing member locking portion  702   e  is forced into the sealing member locking hole  104  in the direction indicated by the arrow mark Z, by the aforementioned reaction force which is directed as indicated by the arrow mark Z, and to which the film wiping portions  702   b   2  are subjected. The sealing member locking portion  702   e  enters the sealing member locking hole  104  as far as the top surface  702   f  of the base portion  702   a  of the sealing member  702  comes into contact with the top surface  101   e  of the sealing film extraction slit  101 . As the sealing member locking portion  702  enters the sealing member locking hole  104  as far as the top surface  702   f  comes into contact with the top surface  101   e , the bending of the multiple fins  702   b  is reduced by an amount equivalent to the dimension (height) Z 3  in  FIG. 18(   b ). Consequently, the state of contact between the film wiping portion  702   b   2  of each fin  702   b  becomes such that the angle of contact between the film wiping portion  702   b   2  and the surface  103   a  of the sealing film  103 , which is facing inward of the developer storage chamber  13   b  of the development unit frame  13  is θ. 
     (Function of Sealing Member) 
     Next, referring to  FIGS. 15-19 , the function of the sealing member  702  in this embodiment is described. 
     Referring to  FIG. 2 , the development storage chamber sealing film  103  keeps the toner T sealed in the developer storage chamber  13   b . Therefore, the toner T adheres to the surface  103   a  of the sealing film  103 , which is facing inward of the developer storage chamber  13   b . Before the cartridge B is used for the first time, a user has to pull the developer storage chamber sealing film  103  out of the development unit frame  13  by pulling the sealing film  103  in the direction indicated by the arrow mark X, by the portion of the sealing film  103 , which is exposed from the development unit frame  13 , as shown in  FIG. 15 . As the sealing film  103  is pulled, the sealing film  103  begins to peel away from the edge of the developer delivery opening  13   d . More specifically, the sealing film  103  begins to peel away in the direction indicted by the arrow mark X, starting from the portion  103   b  of the edge of the developer delivery opening  13   d , at which the sealing film  103  is doubled back in the direction indicated by the arrow mark X as shown in  FIG. 16(   a ). Thus, the portion of the surface  103   a  of the sealing film  103 , which was facing inward of the developer storage chamber  13   b , rubs against the film wiping portions  702   b   2  of the sealing member  702 , whereby the toner T having adhered to the portion of the surface  103   a  of the sealing film  103 , is wiped away by the film wiping portions  702   b   2 . Therefore, the toner T having adhered to the portion of the surface  103   a  of the sealing film  103 , which was facing inward of the developer storage chamber  13   b , is prevented from leaking through the sealing film extraction slit  101 . In other words, it is possible to prevent the problem that the toner T leaks through the sealing film extraction slit  101  when the developer storage chamber sealing film  103  is pulled out of the development unit frame  13 . 
       FIG. 17  is a schematic sectional view of the developer storage chamber sealing member  702  and sealing film extraction slit  101 , at the vertical line P 2 -P 2  in  FIG. 15 , after the extraction of the developer delivery opening sealing film  103  from the development unit frame  13 . It shows the shape of the sealing member  702  after the extraction of the sealing film  103 . Referring to  FIG. 17 , the sealing member  702  is held in the sealing film extraction slit  101  even after the extraction of the developer delivery opening sealing film  103  from the development unit frame  13 . Therefore, it can prevent the toner T from leaking through the sealing film extraction slit  101  even during the usage of the cartridge B. 
     (Comparison between Sealing Member in Fourth Embodiment and Comparative Sealing Member) 
     Here, in order to verify the effectiveness of the sealing member  702  in this embodiment, a comparative sealing member  902  is shown in  FIGS. 24(   a ),  24 ( b ) and  24 ( c ), which are schematic sectional views of the comparative sealing member  902 . 
     In the case where the comparative sealing member  902  is used to keep the developer storage chamber  13   b  sealed, the developer storage chamber sealing film  103  rubs against the fins  902   b  when the sealing film  103  is pulled out of the development unit frame  13 . Thus, the fins  902   b  are subjected to such shearing stress that works in the direction indicated by an arrow mark X. Therefore, a means that can prevent the sealing member  902  from being moved out of the sealing film extraction slit  101  by the shearing stress directed as shown by the arrow mark X is necessary. One of the solutions to this issue is to provide the development unit frame  13  with a sealing member retaining member  111 , which is positioned at the outward end of the sealing film extraction slit  101  as shown in  FIG. 24(   c ). 
     However, in the case where the sealing member retaining member  111 , which is separately manufactured from the development unit frame  13 , is attached to the development unit frame  13  as shown in  FIG. 24(   c ), the cartridge B becomes larger by an amount equivalent to the width X 2  of the sealing member retaining member  111  (dimension of retaining member in terms of lengthwise direction of development unit frame  13 ), making it necessary for the chamber in the main assembly of an image forming apparatus to be increased by an amount equivalent to the width X 2  of the sealing member retaining member  111 , which may result in increase in the size of an electrophotographic image forming apparatus. It also possible that the process cartridge of an electrophotographic image forming apparatus may be restricted in terms of the positioning of the other components than the process cartridge. Moreover, if the sealing member  902  is reduced in the number of the fins  902   b  to compensate for the space taken up by the sealing member retaining member  111 , the width of which is X 2 , the sealing member  902  and sealing film extraction slit  101  have to be more strictly controlled in measurement, in order to compensate for the problem that reducing the sealing member  902  in fin count is likely to reduce the group of fins  902   b  of sealing member  902  in its effectiveness in terms of the removal of the toner T from the sealing film  103 . Strictly controlling the process for manufacturing the cartridge B in terms of the measurement of the sealing film extraction slit  101  and sealing member  902  adds to the cost of the cartridge B. Further, manufacturing the sealing member retaining member  111  separately from the development unit frame  13  and/or sealing member  902  adds to the component cost for the cartridge B, and also, increases the number of steps in the process for assembling the cartridge B, which further increases in cost the cartridge B. 
     In comparison, in the case of the sealing member  702  in the fourth embodiment, its sealing member locking portion  702   e  is an integral part of the sealing member  702  (it protrudes from base portion  702   a ). Therefore, the sealing member retaining member  111 , the width of which is X 2 , is unnecessary, making it unnecessary to increase in size the cartridge chamber of the main assembly of an electrophotographic image forming apparatus by the amount equivalent to the width X of the sealing member retaining member  111 . In other words, using the sealing member  702  in this embodiment in stead of the comparative sealing member  902  can provide a process cartridge which is significantly smaller in dimension in terms of its lengthwise direction than a process cartridge which uses the comparative sealing member  902 . Further, using the sealing member  702  in this embodiment does not require the step necessary to attach the comparative sealing member (conventional sealing member)  902  ( FIG. 24(   c )) to the development unit frame  13 . In other words, the sealing member  702  can simplify and shorten the process for assembling (manufacturing) the process cartridge B. 
     On the other hand, let&#39;s think about the case in which the sealing member  702  is increased in the number of its fins  702   b  by the number equivalent to the width X 2  of the sealing member retaining member  111 .  FIG. 19  is a schematic sectional view of a sealing member  402 , which was created to utilize the space which would have been occupied by the sealing member retaining member  111 . The number of the fins  414  of the sealing member  402  is greater by a value equivalent to the width X 2  of the sealing member retaining member  111  than the comparative sealing member  902 . 
     Using the sealing member  402  increases by a value equal to the number of film wiping portion  402   b   2  (additional film wiping portions), the number of times the developer storage chamber sealing film  103  is wiped (by the film wiping portions) when the sealing film  103  is pulled out of the development unit frame  13  through the sealing film extraction slit  101  in the direction indicated by an arrow mark X. In other words, the sealing member  402  is superior in performance in terms of ability to wipe away the toner T on the developer storage chamber sealing film  103 . In addition, not only does the sealing member  702  in this embodiment function as the sealing member  902  shown in  FIG. 24(   c ), but also, as the sealing member retaining member  111 . Therefore, it can reduce in cost the cartridge B. 
     Referring to  FIG. 16 , the sealing member locking portion  702   e  of the sealing member  702  in this embodiment, which is for preventing the sealing member  702  from coming out of the sealing film extraction slit  101  when the developer storage chamber sealing film  103  is pulled out of the development unit frame  13 , is at the midpoint among the multiple fins  702   b  of the sealing member  702  in terms of the direction indicated by the arrow mark X. However, it may be at the upstream end of the group of multiple fins  702   b  in terms of the direction indicated by the arrow mark X, like the sealing member locking portion  502   e  of the sealing member  502  shown in  FIG. 20(   a ). 
     In addition, in this embodiment, the sealing member  702  was structured so that the width Y 2  of its locking portion  702   e  in terms of the direction indicated by the arrow mark Y became less than the width Y 1  of the base portion  702   a , as shown in  FIG. 15(   b ). However, the sealing member  702  may be structured like the sealing member  602 , shown in  FIG. 20(   b ), the width of the locking portion  602   a  of which is the same as the width of its base portion  602   a . That is, the sealing member  702  may be structured so that the width Y 2  of its locking portion  702   e  becomes the same as the width Y 1  of its base portion  702   a . The effectiveness of the sealing members  502  and  602  shown in  FIGS. 20(   a ) and  20 ( b ), respectively, is the same as that of the above described sealing member  702  in this embodiment. 
     As described above, any one of the sealing members  702 ,  503  and  602  can satisfactorily wipe away the toner T on the developer storage chamber sealing film  103 , without being pulled out of the sealing film extraction slit  101  by the sealing film  103 , when the sealing film  103  is pulled out of the development unit frame  13  through the sealing film extraction slit  101 . Further, they do not increase the development unit frame  13  (cartridge B) in length, and do not add to the cost of the development unit frame  13  (cartridge B). Moreover, they can simplify the process for placing a sealing member in the sealing film extraction slit  101 . 
     That is, this embodiment of the present invention can simplify the process for immovably placing a sealing member in the sealing film extraction slit  101 , and therefore, can simplify the process for assembling the cartridge B, because the sealing member locking portion  702   e  automatically fits into the sealing member locking (regulating) hole  104  of the development unit frame  13  while the sealing member  702  is inserted into the sealing film extraction slit  101 . 
     In each of the above described embodiments of the present invention, the development unit D from which the sealing film  103  is to be pulled out by a user was a part of a developing apparatus (device). However, the present invention is also applicable to a sealing member for the development unit frame of a process cartridge removably installable in an image forming apparatus equipped with an internal mechanism for automatically pulling the sealing film out of its development unit. Further, the development unit D was an integral part of the cartridge B. However, the present invention is also applicable to a sealing member for a development unit in the form of a cartridge which is removably installable in the main assembly of an image forming apparatus A. Further, the image forming apparatus was a laser beam printer. However, the present invention is also applicable to a sealing member for the developing device (apparatus) or development unit removably installable in the main assembly of a copying machine, a facsimile machine, or the like. 
     While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth, and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following claims. 
     This application claims priority from Japanese Patent Applications Nos. 249893/2011, 101130/2012 and 234028/2012 filed Nov. 15, 2011, Apr. 26, 2012 and Oct. 23, 2012, respectively, which are hereby incorporated by reference.