Patent Publication Number: US-9405225-B2

Title: Developer accommodating unit, process cartridge and image forming apparatus

Description:
FIELD OF THE INVENTION AND RELATED ART 
     The present invention relates to a developer accommodating unit, a process cartridge and an image forming apparatus including these members. 
     As an electrophotographic image forming apparatus for forming an image on a recording material (medium) by using an electrophotographic image forming process, there is, e.g., an electrophotographic copying machine. Further, the electrophotographic image forming apparatus includes, e.g., an electrophotographic printer such as LED (light emitting diode printer or laser beam printer; an electrophotographic facsimile machine; an electrophotographic word processor; and the like. 
     Further, the process cartridge refers to a cartridge which is prepared by integrally assembling at least a developing means and a developer accommodating unit accommodating a developer into a unit (cartridge) and which is made detachably mountable to an electrophotographic image forming apparatus main assembly. 
     Further, a developer accommodating container and the developer accommodating unit are to be accommodated in the image forming apparatus or the cartridge. Each of the developer accommodating container and the developer accommodating unit includes at least a flexible container for accommodating the developer. 
     In a conventional electrophotographic image forming apparatus using the electrophotographic image forming process, a process cartridge type in which an electrophotographic photosensitive member and image forming process means actable thereon are integrally assembled into a cartridge and the cartridge is made detachably mountable to the electrophotographic image forming apparatus main assembly has been employed. 
     In such a process cartridge, as shown in  FIG. 18 , an opening provided in a developer accommodating frame  31  for accommodating the developer (toner, carrier and the like) is sealed with a sealing member  32 . In order to reduce a load of a user when the user pulls and peels out a bonding portion  33  formed by (thermal) welding, a constitution in which a free end of the sealing member  32  is folded back and the user can pull the sealing member  32  in an opposite direction (arrow direction in  FIG. 18 ) to a fold back portion haw been widely used. A process cartridge in which a welding pattern is devised for alleviating a force for pulling the sealing member  32  to improve an unsealing operativity has been provided by Japanese Laid-Open Patent Application (JP-A) Hei 07-209976. 
     In this process cartridge, a leading end portion  36   a  and a trailing end portion  36   b  of the sealing member  32  with respect to a pulling-out direction are formed in a mountain (V-character) shape. Further, a seal width of each of the leading end portion  36   a  and the trailing end portion  36   b  is made narrower than the seal width of an intermediate portion (central portion). As a result, strength when the user pulls and unseals the sealing member  32  in the case where an opening width is broad. 
     Further, in order to solve a problem such that the developer is scattered in the process cartridge in a developer filling step during manufacturing of the process cartridge, a process cartridge using deformable inside container has been proposed in JP-A Hei 04-066980. 
     However, there was the following problem in the convention process cartridge. 
     For the purpose of reducing a cost of a developer supplying device by improving operativity of supply of the developer and by preventing the scattering of the developer in the process cartridge, a method of accommodating the developer in a deformable developer accommodating member has been described in JP-A Hei 04-066980. However, in the case where the developer is accommodated in the deformable developer accommodating member described in JP-A Hei 04-066980, during unsealing, an opening of the deformable developer accommodating member is pulled together with a toner seal to be largely deformed, so that it is difficult to effect the unsealing. 
     Further, a method in which the welding pattern of the sealing member is devised has been described in JP-A Hei 07-209976. As shown in  FIG. 18 , the leading end portion  36   a  and the trailing end portion  36   b  of the sheet-like sealing member  32  with respect to the pulling direction are formed in the mountain shape. As a result, a peeling force can be reduced to some extent. In order to further reduce the peeling force, an apex angle of the mountain shape of each of the leading end portion  36   a  and the trailing end portion  36   b  is required to be an acute angle smaller than 90 degrees. In that case, the mountain shape of each of the leading end portion  36   a  and the trailing end portion  36   b  is increased in size. With this increase in size of the mountain shape, there is a need to ensure a space for permitting sealing of the sheet-like sealing member  32  correspondingly, so that a toner accommodating device is increased in size. 
     SUMMARY OF THE INVENTION 
     A principal object of the present invention is to provide a developer accommodating unit, using a flexible container for accommodating a developer, capable of facilitating unsealing of a sealing member for sealing an opening of a flexible container. 
     According to an aspect of the present invention, there is provided a developer accommodating unit for accommodating a developer, comprising: a flexible container provided with an opening for permitting discharge of the accommodated developer; a sealing member for sealing the opening and for exposing the opening by being moved in a direction crossing a longitudinal direction of the developer accommodating unit; an unsealing member, mounted to the sealing member, for moving the sealing member; a frame including a fixing portion for fixing the flexible container; and a bonding portion for bonding an end portion of the sealing member and a periphery of the opening, wherein the bonding portion includes a projected portion or recessed portion in a plane of the bonding portion as at least a part thereof, in an upstream side or a downstream side of the opening with respect to an unsealing direction of the opening. 
     According to another aspect of the present invention, there is provided a developer accommodating unit for accommodating a developer, comprising: a flexible container provided with a plurality of openings for permitting discharge of the accommodated developer; a sealing member for sealing the openings and for exposing the openings by being moved; an unsealing member, mounted to the sealing member, for moving the sealing member; a frame including a fixing portion for fixing the flexible container; and a bonding portion for bonding an end portion of the sealing member and a periphery of the opening, wherein the bonding portion includes a projected portion or recessed portion in a plane of the bonding portion as at least a part thereof in an upstream side or a downstream side of the openings with respect to an unsealing direction of the openings. 
     These and other objects, features and advantages of the present invention will become more apparent upon a 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 sectional illustration showing a structure of an image forming apparatus to which a process cartridge including a developer accommodating unit according to the present invention is detachably mounted. 
         FIG. 2  is a sectional illustration showing a structure of the process cartridge including the developer accommodating unit according to the present invention. 
         FIG. 3  is a perspective illustration showing a cross section of a part of a flexible container in the developer accommodating unit. 
       Part (a) of  FIG. 4  is a sectional illustration showing a structure of a developing device in the developer accommodating unit, and (b) and (c) of  FIG. 4  are sectional illustrations showing a state in which a bonding portion between a sealing member and the flexible container is peeled with advance of rotation of an unsealing member to expose an opening. 
         FIG. 5  is a perspective illustration showing a structure of the flexible container of the developer accommodating unit in Embodiment 1. 
         FIG. 6  is a graph for illustrating a peeling force when the flexible container of the developer accommodating unit in Embodiment 1 is unsealed. 
       Parts (a) and (b) of  FIG. 7  are sectional illustrations showing a structure of the developing device of the developer accommodating unit in Embodiment 1. 
         FIG. 8  is a perspective illustration showing another structure, in which a whole surface of the bonding portion is welded, of the developer accommodating unit in Embodiment 1. 
         FIG. 9  is a perspective illustration showing a still another structure, in which the bonding portion is modified, of the developer accommodating unit in Embodiment 1. 
         FIG. 10  is a perspective illustration showing a structure of a flexible container of a developer accommodating unit in Embodiment 2 of the present invention. 
         FIG. 11  is a sectional illustration showing a structure of a developing device of the developer accommodating unit in Embodiment 2. 
         FIG. 12  is a perspective illustration showing a structure of a developing device of a developer accommodating unit in Embodiment 3 of the present invention. 
         FIG. 13  is a plan illustration showing structures of a plurality of openings, connecting portions each provided between adjacent ones of the openings, and a bonding portion in the developer accommodating unit in Embodiment 3. 
       Parts (a), (b) and (c) of  FIG. 14  are perspective illustrations showing a structure of a flexible container of the developer accommodating unit in Embodiment 3. 
         FIG. 15  is a perspective illustration showing structures of a plurality of openings, connecting portions each provided between adjacent ones of the openings, and a bonding portion in a developer accommodating unit in a comparison example. 
         FIG. 16  is a plan illustration showing structures of a longitudinal of openings, connecting portions each provided between adjacent ones of the openings, and a bonding portion in a developer accommodating unit in Embodiment 4 of the present invention. 
         FIG. 17  is a plan illustration showing structures of a longitudinal of openings, connecting portions each provided between adjacent ones of the openings, and a bonding portion in a developer accommodating unit in Embodiment 5 of the present invention. 
         FIG. 18  is a perspective view for illustrating a conventional constitution. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of an image forming apparatus to which a process cartridge including a developer accommodating unit according to the present invention is detachably mounted will be specifically described with reference to the drawings. 
     [Embodiment 1] 
     First, with reference to  FIGS. 1 to 9 , a constitution of an image forming apparatus which a process cartridge including a developer accommodating unit according to the present invention in Embodiment 1 is detachably mounted will be described. 
     In the following description, a developer accommodating unit generating a toner constituting a developer includes at least a developing bag  16  as a flexible container provided with a plurality of openings  35   a  for permitting discharge of the accommodated developer, and flames  17  and  18  which accommodate the developer bag  16 . The flames  17  and  18  accommodated also an unsealing member  21  and include a fixing portion  18   a  for fixing the developer bag  16 . The unsealing member  21  is accommodated between the flames  17  and  18 . 
     Further, the developer accommodating unit includes a sealing member  19  for sealing the plurality of openings  35   a  and for exposing the openings  35   a  by being moved. The developer accommodating unit further includes the unsealing member  21 , mounted to the sealing member  19 , for moving the sealing member  19 . 
     Further, the developer accommodating unit includes a bonding portion  22  for bonding an end portion of the sealing member  19  and a periphery of the openings  35   a  of the developer bag  16 . The bonding portion  22  includes projected portions (projection-shaped portions)  22   a   1  and  22   a   2  projected outward of a closed pattern thereof indicated by a broken line in each of  FIGS. 5, 9, 12 and 14 , and includes a recessed portion (recess-shaped portion)  22   d  recessed inward of a closed pattern thereof indicated by a broken line in  FIG. 10 . 
       FIG. 1  is a sectional illustration of an image forming apparatus B to which a process cartridge A including the developer accommodating unit according to the present invention is detachably mounted.  FIG. 2  is a sectional illustration of the process cartridge A including the developer accommodating unit according to the present invention. 
     &lt;Process Cartridge&gt; 
     As shown in  FIG. 2 , the process cartridge A includes a photosensitive drum  11  as an image bearing member, and includes an image forming process means actable on the photosensitive drum  11 . 
     Here, as the image forming process means, e.g., a charging roller  12  as a charging means for electrically charging the surface of the photosensitive drum  11  is used. Further, a developing device  38  for forming a toner image on the surface of the photosensitive drum  11  and a cleaning blade  14  as a cleaning means for removing the developer (containing the toner, a carrier and the like) remaining on the surface of the photosensitive drum  11 . 
     The process cartridge A in this embodiment includes, as shown in  FIG. 2 , at a periphery of the photosensitive drum  11  as the image bearing member, the charging roller  12  as the charging means and a cleaning unit  24  including the cleaning blade  14 , as the cleaning means, having elasticity. 
     Further, the process cartridge A includes the developing device  38  including the frames  17  and  18 . The process cartridge A integrally includes the cleaner unit  24  and the developing device  38  and is, as shown in  FIG. 1 , constituted so as to be detachably mountable to a main assembly of the image forming apparatus B. 
     The developing device  38  includes a developing roller  13  as the developing means, a developing blade  15 , a developer supplying roller  23 , and the flexible developer bag  16  for accommodating the developer. The developing roller  13  and the developing blade  15  are supported by the frame  17 . 
     &lt;Image Forming Apparatus&gt; 
     The process cartridge A is mounted in the image forming apparatus B and then is used for image formation. In the image formation, a sheet S is fed, by a feeding roller  7 , from a sheet cassette  6  mounted at a lower portion of the image forming apparatus B. In synchronism with the feeding of the sheet S, the surface of the photosensitive drum  11  uniformly charged by the charging roller  12  is subjected to selective exposure to light from an exposure device  8  depending on image data, so that the electrostatic latent image is formed. 
     The developer is supplied to the developing roller  13  as a developer carrying member by the developer supplying roller  23  in a sponge-like shape, so that the developer is carried in a thin layer on the surface of the developing roller  13  by the developing blade  15 . By applying a developing bias voltage to the developing roller  13 , the developer is supplied depending on the electrostatic latent image, so that the latent image is developed into a developer image. Then, by applying a transfer bias voltage to the transfer roller  9 , the developer image is transferred onto the sheet S conveyed to a nip. 
     The sheet S is conveyed into a fixing device  10 , in which the developer image is heated and pressed to be fixed on the sheet S, and thereafter is discharged, by a discharging roller  1  onto a discharge portion  3  provided at an upper portion of the image forming apparatus B. 
     &lt;Developer Bag&gt; 
     With reference to  FIGS. 3 and 4 , a constitution of the developer bag  16  will be described.  FIG. 3  is a perspective illustration showing a cross section of a part of the developer bag  16 . Part (a) of  FIG. 4  is a sectional illustration showing a structure of the developing device  38 , and (b) and (c) of  FIG. 4  are sectional illustrations showing a state in which the bonding portion  22  between the sealing member  19  and the developer bag  16  is peeled with advance of rotation of the unsealing member  21  to expose the openings  35   a.    
     As shown in  FIG. 3 , the developer bag  16  accommodates the developer therein and has a deformable bag-like shape. In order to discharge the accommodated developer, the developer bag  16  includes, at a discharging portion  35 , the longitudinal of openings  35   a  and connecting portions  36   b  each provided between adjacent ones of the openings  35   a . Each of the openings  35   a  in this embodiment has an elongated circle hole shape. Incidentally, as the shape of each of the openings  35   a , in addition to the elongated circle hole shape, it is possible to appropriately employ shapes of a round hole, a rectangular hole, and the like. The shape of each opening  35   a  may only be required to be appropriately selected in view of a necessary amount of discharge of the toner (developer) from the developer bag  16 , strength of the developer bag  16  in the neighborhood of the openings  35   a , and the like. 
     Further, as shown in  FIG. 4 , before use of the developer bag  16 , a periphery of the openings  35   a  is continuously surrounded by the bonding portion  22  having a loop-like shape indicated by a broken line in  FIG. 5 , and then is unsealably sealed with the sealing member  19 , so that the toner constituting the developer is accommodated in the developer bag  16 . 
     The bonding portion  22  includes a first bonding portion  22   a  in an upstream side (lower side in  FIG. 5 ) of the openings  35   a  with respect to an unsealing direction (arrow E direction in  FIG. 5 ) in the case where the bonding portion  22  is seen along a surface of the sealing member  19 . Further, the bonding portion  22  includes a second bonding portion  22   b , opposing the first bonding portion  22   a  via the openings  35   a , in a downstream side (upper side in  FIG. 5 ) of the openings  35   a  with respect to the unsealing direction (arrow E direction in  FIG. 5 ). Further, a widthwise bonding portion  22   c  for connecting an end portion of the first bonding portion  22   a  and an associated end portion of the second bonding portion  22   b  is provided, continuously to the first and second bonding portions  22   a  and  22   b , at each of longitudinal end portions of the bonding portion  22 . 
     The sealing member  19  is engaged with the unsealing member  21  in other end side opposite from the bonding portion  22  side where the periphery of the openings  35   a  is sealed. The unsealing member  21  is rotatably shaft-supported at end portions thereof by the flame  18 , and is rotationally driven by an unshown driving means provided in the image forming apparatus B. Further, as shown in  FIG. 3 , the developer bag  16  includes a fixed portion  16   d  engaged with the fixing portion  18   a  of the flame  18 . 
     &lt;Bonding Portion of Developer Bag&gt; 
     With reference to  FIG. 4 , a constitution of the bonding portion  22  of the developer bag  16  will be described.  FIG. 5  is perspective view of the developer bag  16 . 
     The bonding portion indicated by the broken line in  FIG. 5  is provided with a sealant layer in the sealing member  19  side, and is bonded to the periphery of the openings  35   a  of the developer bag  16  by welding. 
     Along a longitudinal direction (arrow F direction in  FIG. 5 ) of the developer accommodating unit, the bonding portion  22  includes two bonding portions consisting of the first bonding portion  22   a  and the second bonding portion  22   b  and includes, along a widthwise direction (arrow E direction in  FIG. 5 ) of the developer accommodating unit, two bonding portions each consisting of the widthwise bonding portion  22   c . These bonding portions are continuously generated (connected) to each other in a shape such that the bonding portions surround the openings arranged in a direction crossing (perpendicular to) the unsealing direction (arrow E direction) of the openings  35   a . For this reason, the sealing of the openings  35   a  is enabled. 
     Here, of the two bonding portions  22   a  and  22   b  welded along the longitudinal direction (arrow F direction in  FIG. 5 ) of the developer accommodating unit, a bonding portion to be unsealed earlier is the first bonding portion  22   a  and a bonding portion to be unsealed later is the second bonding portion  22   b . The bonding portion opposing the first bonding portion  22   a  via the openings  35   a  is the second bonding portion  22   b . The bonding portions each connected with the two bonding portions  22   a  and  22   b  along the widthwise direction (arrow E direction in Embodiment 5) of the developer accommodating unit are the widthwise bonding portions  22   c.    
     In this embodiment, the plurality of projected portions  22   a   1  and  22   a   2  each projected toward the upstream side (lower side in  FIG. 5 ) with respect to the unsealing direction (arrow E direction) which is a direction in which the unsealing of the first bonding portion advances are provided. Each of the projected portions  22   a   1  and  22   a   2  is projected toward the upstream side (lower side in  FIG. 5 ) with respect to the unsealing direction (arrow E direction) in a plane of the first bonding portion  22   a  at each of longitudinal end portions of the first bonding portion  22   a . These projected portions  22   a   1  and  22   a   2  are provided in position, of the first bonding portion  22   a , corresponding to the end portions where the unsealing member  21  is supported. 
     When the unsealing member  21  is rotated to wind the sealing member  19  about an outer peripheral surface thereof and thus is pulled, at first, the unsealing of the first bonding portion  22   a  of the bonding portion  22  is started. At that time, portions which are peeled first as a trigger for the peeling are the projected portions  22   a   1  and  22   a   2 . These projected portions  22   a   1  and  22   a   2  are provided at the end portions of the first bonding portion  22   a  with respect to the arrow F direction perpendicular to the unsealing direction (arrow E direction) as the direction in which the unsealing of the first bonding portion  22   a  advances. 
     Further, the first bonding portion  22   a , the projected portion  22   a   1  provided at a left end portion of the first bonding portion  22   a  in  FIG. 5 , and the widthwise bonding portion  22   c  provided in a left side in  FIG. 5  are continuously bonded (connected). Further, the second bonding portion  22   b , the widthwise bonding portion  22   c  provided in a right side in  FIG. 5 , and the projected portion  22   a   2  provided at a right end portion of the first bonding portion  22   a  are continuously bonded (connected). 
     Here, provision of the projected portions  22   a   1  and  22   a   2  in the plane of the bonding portion  22  means that the projected portions  22   a   1  and  22   a   2  are provided at a part of the bonding portion  22  in the plane of the bonding portion  22  based on the assumption of a phantom plane including the bonding portion  22 . 
     &lt;Arrangement of Openings of Developing Bag&gt; 
     Next, with reference to  FIGS. 4 and 5 , arrangement of the openings  35   a  provided in the developer bag  16  will be described. 
     As shown in  FIG. 4 , a movement direction (pulling direction) of the sealing member  19  for sealing the openings  35   a  provided in the developer bag  16  and for exposing the openings  35   a  by being moved is an arrow D direction in (a) of  FIG. 4 . 
     By the movement of the sealing member  19  in the arrow D direction of  FIG. 4 , the exposure of the openings  35   a  advances in the unsealing direction which is the arrow E direction of  FIG. 5 . The plurality of openings  35   a  are formed with predetermined pitches with respect to the arrow F direction which crosses which is (perpendicular to) the unsealing direction as the arrow E direction of  FIG. 5  and which is the longitudinal direction of the developer accommodating unit, and each of connecting portions  35   b  is provided between adjacent ones of the openings  35   a . Further, the sealing member  19  is fixed at an end portion thereof on an outer peripheral surface of the unsealing member  21  and has a constitution in which the sealing member  19  is wound up about the outer peripheral surface of the unsealing member  21  by rotating the unsealing member  21 . A rotational axis direction of the unsealing member  21  is parallel to the arrow F direction shown as the longitudinal direction in  FIG. 5 . 
     A rotational axis direction of the developing roller  13  shown in (a) of  FIG. 4  and the arrow F direction along which the plurality of openings  35   a  are arranged are made parallel to each other. As a result, when the developer in the developing bag  16  is discharged through the openings  35   a , the developer is supplied uniformly over the longitudinal direction of the developing roller  13 . 
     &lt;Sealing Member&gt; 
     Next, with reference to  FIG. 5 , a constitution of the sealing member  19  will be described. As shown in  FIG. 5 , the sealing member  19  includes a sealing portion  19   a  for sealing (covering) the developing bag  16  to confine the developer in the developing bag  16  before use of the process cartridge A and includes an engaged portion  19   b  engaged with the unsealing member  21 , and is formed in a sheet shape. The engaged portion  19   b  is engaged with the unsealing member  21  for exposing the openings  35   a  by being rotated to move the sealing member  19  in the arrow D direction in (a) of  FIG. 4 . The unsealing member  21  is provided rotatably about a rotation shaft provided in the frame  18 . Further, the sealing member  19  includes a fold-back portion  19   d  folded back at a portion between the sealing portion  19   a  and the engaged portion  19   d.    
     &lt;Unsealing Member&gt; 
     Next, with reference to  FIG. 4 , a constitution of the unsealing member  21  will be described. The unsealing member  21  applies a force to the sealing member  19  to move the sealing member  19 , so that the sealing member  19  is peeled off from the developing bag  16 . The unsealing member  21  includes an unshown supporting portion which has a shaft shape and which is rotatably supported by the frame  18  at its end portions, and includes the engaging portion  21   c  for fixing the engaged portion  19   b  of the sealing member  19 . Further, the unsealing member  21  includes an urging sheet  21   b.    
     &lt;Unsealing Operation of Developing Bag&gt; 
     Next, with reference to  FIGS. 4 to 7 , an unsealing operation of the developing bag  16  will be described. Part (a) of  FIG. 4  is a sectional illustration of the developing device  38  immediately before the developer bag  16  is unsealed, and (b) and (c) of  FIG. 4  are parted sectional illustrations showing a structure in the neighborhood of the openings  35   a .  FIG. 6  is a graph for illustrating a peeling force when the sealing member  19  is unsealed, and  FIG. 7  is a sectional illustration showing a structure of the developing device  38 . Here, in the order from (a) of  FIG. 4  to (b) of  FIG. 4 , the unsealing operation advances. 
     As shown in  FIG. 4 , by a driving force transmitted from a driving source provided in the image forming apparatus B, the unsealing member  21  is rotated in an arrow C direction in (a) of  FIG. 4 , so that the sealing member  19  is pulled in the arrow D direction in (a) of  FIG. 4  to gradually expose the openings  35   a . At this time, the sealing member  19  exposes the openings  35   a  while maintaining the fold-back portion  19   d . For this reason, the bonding portion  22  is not in a state of shearing peeling (approximately 0-degree peeling), and therefore the unsealing of the sealing member  19  can be advanced. 
     As shown in (b) and (c) of  FIG. 4 , the developer bag  16  is fixed to the fixing portion  18   a  of the flame  18  by the fixed portion  16   d . For this reason, first, as shown from (a) of  FIG. 4  to (b) of  FIG. 4 , when the rotation of the unsealing member  21  in the arrow C direction is started, the sealing member  19  fixed to the unsealing member  21  is pulled in the arrow D direction in (a) and (b) of  FIG. 4 , so that the unsealing starts. At this time, the unsealing of the bonding portion  22  starts from the first bonding portion  22   a.    
     In this embodiment, as shown in  FIG. 5 , the projected portions  22   a   1  and  22   a   2  disposed so as to be projected toward the upstream side (lower side in  FIG. 5 ) with respect to the arrow E direction in  FIG. 5  as the direction in which the unsealing advances are provided. For this reason, a peeling force generated by the pulling of the sealing member  19  concentratedly acts on the projected portions  22   a   1  and  22   a   2 , so that the unsealing of the first bonding portion  22   a  advances from the projected portions  22   a   1  and  22   a   2  as the trigger of the unsealing. 
     Here, with respect to the longitudinal direction (arrow F direction in  FIG. 5 ) of the first bonding portion  22   a , with a longer distance in which the peeling of the first bonding portion  22   a  is generated simultaneously, a peak  40  of the peeling force shown in  FIG. 6  becomes larger. In this embodiment, the projected portions  22   a   1  and  22   a   2  disposed so as to be projected toward the upstream side (lower side in  FIG. 5 ) with respect to the arrow E direction in  FIG. 5  as the direction in which the unsealing of the first bonding portion  22   a  advances are provided. For this reason, when the peeling of the first bonding portion  22   a  occurs, it becomes possible to suppress generation of the peak  40  of the peeling force shown in  FIG. 6  to reduce the peeling force. 
     Further, during start of the unsealing of the first bonding portion  22   a , when the force for unsealing the unsealing member  21  is applied to the unsealing member  21 , the unsealing member  21  is pulled by the sealing member  19  in a direction opposite to the arrow D direction shown in (a) of  FIG. 4 . The unsealing member  21  is supported at the ends thereof by the flame  18 . For this reason, the unsealing member  21  is not a little flexed in the direction opposite to the arrow D direction shown in (a) of  FIG. 4 . 
     A degree of this flexure of the unsealing member  21  is smallest in the neighborhood of each of portions closer to the end where the unsealing member  21  is supported, and is largest in the neighborhood of a central portion, remote from the end where the unsealing member  21  is supported, with respect to an axial direction of the unsealing member  21 . That is, the first bonding portion  22   a  is pulled by the sealing member  19  fixed to the unsealing member  21  in a manner such that portions thereof in the neighborhood of the ends are not a little peeled earlier than a portion in the neighborhood of the longitudinal central portion thereof, so that the unsealing advances. 
     In this embodiment, with respect to the arrow F direction in  FIG. 5 , the first bonding portion  22   a  is provided with the positions  22   a   1  and  22   a   2  at the end portions thereof where the unsealing starts earlier. For that reason, even when the flexure is not a little generated in the unsealing member  21 , it is possible to start the unsealing of the first bonding portion  22   a  with reliability from the projected portions  22   a   1  and  22   a   2  as the trigger of the unsealing. 
     Thereafter, as shown from (b) of  FIG. 4  to (c) of  FIG. 4 , with advance of the rotation of the unsealing member  21  in the arrow C direction, the widthwise bonding portions  22   c  provided continuously from the first bonding portion  22   a  through the second end portions of the first bonding portion  22   a  are peeled. Then, the longitudinal of openings  35   a  are exposed, and finally the second bonding portion  22   b  provided continuously from the widthwise bonding portions  22   c  through longitudinal end portions of the second bonding portion  22   b  is peeled, as shown in  FIG. 5 , the deformation of the openings  35   a  is suppressed by the connecting portions  35   b  each provided between adjacent ones of the openings so as to bridge the first bonding portion  22   a  and the second bonding portion  22   b.    
     By employing such a constitution, the second bonding portion  22   b  can be mode peelable with reliability. When the unsealing is completed, the openings  35   a  are completely exposed, so that the developer in the developer bag  16  is discharged in an arrow I direction in (c) of  FIG. 4  through the openings  35   a , into a toner supplying chamber  2  in which the developer supplying roller  23  is provided. 
     After the unsealing of the sealing member  19 , as shown from (a) of  FIG. 7  to (b) of  FIG. 7 , the unsealing member  21  is rotated in the arrow C direction shown in  FIG. 7 . As a result, deformation and contraction of the developer bag  16  by unsealing of the developer bag  16  with an urging sheet  21   b  provided on the unsealing member  21  in an arrow J direction in (a) of  FIG. 7  and shape restoration of the developer bag  16  in an arrow K direction by the weight of the developer inside the developer bag  16  and flexibility of the developer bag  16  are repeated. As a result, the developer inside the developer bag  16  is discharged into the toner supplying chamber  2  through the openings  35   a.    
     In this way, the projected portions  22   a   1  and  22   a   2  projected toward the upstream side (lower side in  FIG. 5 ) with respect to the arrow E direction in  FIG. 5  in which the unsealing of the first bonding portion  22   a  advances. Further, the projected portions  22   a   1  and  22   a   2  are provided at the end portions of the first bonding portion  22   a  with respect to the arrow F direction in  FIG. 5  perpendicular to the arrow E direction in  FIG. 5  in which the unsealing of the first bonding portion  22   a  advances. 
     By employing such a constitution, when the peeling of the first bonding portion  22   a  is generated, it is possible to start the unsealing from the projected portions  22   a   1  and  22   a   2  as the trigger of the unsealing so that the generation of the peak  40  of the peeling force shown in  FIG. 6  can be suppressed and thus the peeling force can be reduced. 
     &lt;Another Example of Constitution of the Bonding Portion of Developer Bag&gt; 
     Next, with reference to  FIGS. 8 and 9 , another example of the constitution of the bonding portion  22  of the developer bag  16  will be described.  FIGS. 8 and 9  are perspective illustrations each showing a structure in the neighborhood of the openings  35   a  and the bonding portion  22 . 
     In this embodiment, the bonding portion  22  for sealing the openings  35   a  was formed in a shape such that the openings  35   a  is continuously surrounded by the first bonding portion  22   a  including the projected portion  22   a   1  and  22   a   2 , the second bonding portion  22   b  and the widthwise bonding portions  22   c.    
     As another example of the constitution of the bonding portion  22 , as shown in  FIG. 8 , a bonding portion  22  bonded to the periphery of the openings  35   a  by whole-surface welding is provided. Further, the bonding portion  22  is provided, at end portions thereof with respect to the longitudinal direction (arrow F direction in  FIG. 8 ) of the bonding portion  22 , with projected portions  22   a   1  and  22   a   2  projected toward an upstream side (lower side in  FIG. 8 ) with respect to the arrow E direction in  FIG. 8  as the unsealing direction of the openings  35   a . Even when such a constitution is employed, a similar effect can be obtained. 
     When the unsealing of the bonding portion  22  constituting a bonding portion is started, the unsealing of the bonding portion  22  advances from the projected portions  22   a   1  and  22   a   2  as the trigger for the unsealing. Even when such a constitution is employed, it is possible to suppress the generation of the peak  40  of the peeling force shown in  FIG. 6  to reduce the peeling force. 
     Further, in this embodiment, as the trigger when the first bonding portion  22   a  is unsealed, the projected portions  22   a   1  and  22   a   2  were provided at the longitudinal end portions of the first bonding portion  22   a  with respect to the arrow F direction in  FIG. 8  perpendicular to the arrow E direction in  FIG. 8  in which the unsealing advances. 
     As another constitution of the bonding portion  22 , as shown in  FIG. 9 , the bonding portion  22  is constituted as follows with respect to the arrow F direction in  FIG. 9  perpendicular to the arrow E direction in  FIG. 9  in which the unsealing advances. At a longitudinal central portion of the first bonding portion  22   a , a projected portion  22   a   3  projected toward an upstream side (lower side in  FIG. 9 ) with respect to the arrow E direction in  FIG. 9  in which the unsealing of the first bonding portion  22   a  advances. 
     In this case, a projection amount X 2  of the projected portion  22   a   3  from a rectilinear portion of the first bonding portion  22   a  is provided so as to be not less than a projection amount X 1  of the unsealing member  21  at the central portion with respect to the axial direction of the unsealing member  21 . As a result, by using the projected portion  22   a   3  as the trigger for the unsealing with reliability, it is possible to perform the unsealing of the first bonding portion  22   a  and thus a similar effect can be obtained. 
     [Embodiment 2] 
     Next, with reference to  FIGS. 10 and 11 , a constitution of an image forming apparatus to which a process cartridge including a developer accommodating unit according to the present invention in Embodiment 2 is detachably mounted will be described. Incidentally, constituent elements similar to those in the above-described Embodiment 1 are represented by the same reference numerals or symbols and will be omitted from description.  FIG. 10  is a perspective illustration of the developer bag  16 , and  FIG. 11  is a sectional illustration of the developing device  38 . In this embodiment and later embodiments, a difference from the above-described embodiment(s) will be specifically described. Unless otherwise specified particularly, materials, shapes and the like are the same as those in the above-described embodiment(s). 
     In Embodiment 1 described above, as the trigger when the first bonding portion  22   a  is unsealed, the projected portions  22   a   1  and  22   a   2  projected toward the upstream side with respect to the arrow E direction in which the unsealing of the first bonding portion  22   a  advances are provided. 
     In this embodiment, as indicated by a broken line in  FIG. 10 , a first bonding portion  22   a  is provided in an upstream side (lower side in  FIG. 10 ) with respect to the arrow E direction in  FIG. 10  as the unsealing direction of the openings  35   a . In a plane of the first bonding portion  22   a , a plurality of recessed portions (recess-shaped portions)  22   d  recessed toward a downstream side (upward direction in  FIG. 10 ) with respect to the arrow E direction in  FIG. 10  as the unsealing direction in which the unsealing advances are provided. Further, at least a part of the recessed portions  22   d  enters a region of connecting portions  35   b.    
     Also in such a constitution, it is possible to obtain an effect similar to the effect in Embodiment 1. Further, in this embodiment, the recessed portions  22   d  are disposed in positions associated with the connecting portions  35   b  in the following manner. Along an extension line of the arrow E direction in  FIG. 10  in which the unsealing advances, the recessed portions  22   d  are disposed so that at least a part of each of the recessed portions  22   d  enters the region of an associated connecting portion  36   b  provided between associated adjacent ones of the openings  35   a  shown in  FIG. 10 . 
     Here, provision of the recessed portions  22   d  in the plane of the bonding portion  22  means that the recessed portions  22   d  are provided at a part of the bonding portion  22  in the plane of the bonding portion  22  based on the assumption of a phantom plane including the bonding portion  22 . 
     By the rotation of the unsealing member  21  in the arrow C direction in  FIG. 11 , the unsealing of the first bonding portion  22   a  starts from projected portions, each having a predetermined width, other than the recessed portions  22   d  of the first bonding portion  22   a  indicated by the broken line in  FIG. 10 , as the trigger for the unsealing. By forming the recessed portions  22   d  in such a shape, a longitudinal distance of the first bonding portion  22   a  in which the peeling of the first bonding portion  22   a  is generated simultaneously with respect to the arrow F direction in  FIG. 10  can be made short, so that it is possible to suppress the peak  40  of the peeling force shown in  FIG. 6 . 
     Further, the developer bag  16  includes a corner portion  16   e  shown in  FIG. 11  at a lower portion thereof in the upstream side (lower side in  FIG. 11 ) with respect to the arrow E direction in  FIG. 10  in which the exposure of the openings  35   a  advances. As shown in  FIG. 11 , the corner portion  16   e  constitutes a portion where it is difficult to discharge the developer in the developer bag  16  through the openings  35   a  when the discharge of the developer advances and thus an amount of the developer becomes small. Then, the developer  99  not a little remains in the corner portion  16   e.    
     For that reason, when a volume of the corner portion  16   e  of the developer bag  16  becomes large, an amount of the developer which is not readily discharged from the developer bag  16  is increased, so that a residual developer  99  remaining in the developer bag  16  is increased in amount. In the case of the recessed portions  22   d  disposed in this embodiment, as shown in  FIG. 10 , a most recessed portion  22   d   1  of each of the recessed portions  22   d  of the first bonding portion is disposed so as to enter the region of the associated connecting portion  36   b  provided between the associated adjacent ones of the openings  35   a . As a result, a necessary area for the first bonding portion  22   a  can be minimized, and therefore, a volume of the corner portion  16   e  of the developer bag  16  shown in  FIG. 11  can be minimized, so that it is possible to decrease the amount of the developer  99  remaining in the corner portion  16   e  of the developer bag  16 . 
     For this reason, the unsealing can be started from the projected portions, each having the predetermined width, other than the recessed portions  22   d  of the first bonding portion  22 , as the trigger. Further, the generation of the peak  40  of the peeling force shown in  FIG. 6  can be suppressed and thus the peeling force can be reduced. Further, the generation of the peak  40  of the peeling force shown in  FIG. 6  can be suppressed to reduce the peeling force. Further, the volume of the corner portion  16   e  of the developer bag  16  can be optimized so as to be minimized. For this reason, the developer  99  remaining in the corner portion  16   e  of the developer bag  16  can be made smallest in amount. Other constitutions are the same as those in Embodiment 1, and a similar effect can be obtained. 
     [Embodiment 3] 
     Next, with reference to  FIGS. 12 and 15 , a constitution of an image forming apparatus to which a process cartridge including a developer accommodating unit according to the present invention in Embodiment 2 is detachably mounted will be described. Incidentally, constituent elements similar to those in the above-described embodiment 5 are represented by the same reference numerals or symbols and will be omitted from description.  FIG. 2  is a perspective illustration showing a structure of the developing device  38 , and  FIG. 13  is a plan illustration showing a structure in the neighborhood of the plurality of openings  35   a  and the bonding portion  22 . Parts (a) to (c) of  FIG. 14  are perspective views for illustrating an unsealing operation of the openings  35   a , and  FIG. 15  is a perspective illustration showing a structure in the neighborhood of the openings  35   a  and the bonding portion  22  in another shape. 
     In Embodiment 1 described above, as shown in  FIG. 5 , as the trigger when the first bonding portion  22   a  is unsealed, the projected portions  22   a   1  and  22   a   2  projected toward the upstream side (lower side in  FIG. 5 ) with respect to the arrow E direction in which the unsealing of the first bonding portion  22   a  advances are provided. 
     In this embodiment, as shown in  FIG. 12 , a second bonding portion  22   b  indicated by a broken line in  FIG. 12  is provided in a downstream side (upward direction in  FIG. 12 ) with respect to the arrow E direction in  FIG. 12  as the unsealing direction of the openings  35   a.    
     Further, in a plane of the second bonding portion  22   b , a plurality of projected portions  22   e  projected recessed toward a downstream side (upward direction in  FIG. 12 ) with respect to the arrow E direction in  FIG. 12  in the plane of the second bonding portion  22   b . A most projected portion  22   e   1  of each of the projected portions  22   e  is disposed in the neighborhood of a longitudinal central portion of an associated opening  35   a . Further, each of the projected portions  22   e  and an associated opening  35   a  thereof are disposed on the same line in the arrow E direction of  FIG. 12  as the unsealing direction of the openings  35   a.    
     As shown in  FIG. 12 , the projected portions  22   e  projected toward the downstream side (upper side in  FIG. 12 ) with respect to the arrow E direction in  FIG. 12  in which the unsealing of the second bonding portion  22   b  advances. For this reason, the unsealing of the second bonding portion  22   b  starts from the portions, as the trigger, other than the projected portions  22   e . For this reason, similarly as in the case where the first bonding portion  22   a  is provided with the projected portions  22   a   1  and  22   a   2  as shown in  FIG. 5 , the generation of the peak  40  of the peeling force, shown in  FIG. 6 , of the second bonding portion  22   b  can be suppressed to reduce the peeling force. 
     Further, in this embodiment, as shown in  FIG. 13 , with respect to the arrow F direction in  FIG. 13  perpendicular to the arrow E direction in  FIG. 13  in which the unsealing advances, the most projected portion  22   e   1  of each of the projected portions  22   e  is disposed in the neighborhood of the longitudinal central portion of the associated opening  35   a . A state in which the unsealing advances to the second bonding portion  22   b  of the developer bag  16  is shown in (a) of  FIG. 14 . From this state, when the rotation of the unsealing member  21  in the arrow C direction further advances, the sealing member  19  is further pulled and moved in the arrow D direction in (a) of  FIG. 14 . 
     At this time, as shown in  FIG. 13 , in some cases, a width L 2  of the openings with respect to the arrow E direction in which the unsealing advances is extremely larger than a width L 1  of each opening  35   a  with respect to the arrow F direction perpendicular to the arrow E direction in which the unsealing advances. In that case, a pulling effect of the connecting portions each provided between adjacent ones of the openings  35   a  is not exerted until the neighborhood of the longitudinal central portions of the openings  35   a , so that it becomes difficult to unseal the second bonding portion  22   b  is some cases. 
     Here, a region of the connecting portions each provided between adjacent ones of the openings  35   a  refers to a region defined by upper and lower rectilinear lines, indicated by a chain line in  FIG. 13 , between which the width L 2  with respect to the arrow E direction in which the unsealing of the openings  35   a  advances is shown, and left and right edges of each of the openings shown in  FIG. 13 . 
       FIG. 15  shows an example of the case where it is difficult to unseal the openings since the width L 2  of the openings  35   a  with respect to the arrow E direction in  FIG. 13  in which the unsealing of the openings  35   a  advances is extremely larger than the width L 1  of each opening  35   a  with respect to the arrow F direction in  FIG. 13  perpendicular to the arrow E direction.  FIG. 15  shows a state in which the unsealing advances to the second bonding portion  22   b.    
     The openings  35   a  shown in  FIG. 15  has the width L 2 , with respect to the arrow E direction in  FIG. 13  in which the unsealing thereof advances, extremely larger than the width L 1  with respect to the arrow F direction in  FIG. 13  perpendicular to the arrow E direction. For this reason, during the unsealing of the second bonding portion  22   b  shown in  FIG. 15 , the openings  35   a  are largely deformed at the longitudinal central portions thereof. As a result, the openings  35   a  largely open with respect to the arrow D direction in  FIG. 15 . 
     That is, due to the deformation of the openings  35   a  in the neighborhood of the central portions thereof, a supporting force for supporting the developer bag  16  at the fixed portion  16   d  cannot be transmitted through the openings  35   a  until the unsealing of the second bonding portion  22   b  is completed. Further, in the case where the shearing peeling (approximately 0-degree peeling) state is created by the deformation of the openings  35   a  in the neighborhood of the central portions of the openings  35   a , compared with the case of an inclination peeling (state), a large force is required to peel the sealing member  19 , so that it becomes difficult to unseal the second bonding portion  22   b.    
     Also in such a case, as in this embodiment shown in  FIG. 12 , with respect to the arrow F direction in  FIG. 12  perpendicular to the arrow E direction in which the unsealing of the openings  35   a  advances, the second bonding portion  22   b  is constituted as follows. In the plane of the second bonding portion  22   b , the most projected portion  22   e   1  of each projected portion  22   e  provided so as to be projected toward the downstream side (upper side in  FIG. 12 ) with respect to the arrow E direction in  FIG. 12  as the unsealing direction of the openings  35   a  is disposed in the neighborhood of the longitudinal central portion of the associated openings  35   a.    
     As a result, during the unsealing of the second bonding portion  22   b , in the neighborhood of the longitudinal central portion of each opening  35   a  where the opening  35   a  is largely deformed, corresponding to a projection of the associated projected portion  22   e  provided in the downstream side with respect to the arrow E direction, it is possible to perform the unsealing at a position remote from the opening  35   a . For this reason, it is possible to suppress the deformation of the openings  35   a  in the neighborhood of the longitudinal central portions of the openings  35   a.    
     Parts (a) to (c) of  FIG. 14  are perspective views each for illustrating a state of the unsealing of the second bonding portion  22   b  in this embodiment. Here, the unsealing advances in the order from (a) of  FIG. 14  to (b) of  FIG. 14  and then to (c) of  FIG. 14 . First, as shown in (a) and (b) of  FIG. 14 , the second bonding portion  22   b  is provided with the projected portions  22   e  projected toward the downstream side (upper side in  FIG. 14 ) with respect to the arrow E direction in  FIG. 14  in which the unsealing advances. For this reason, the unsealing advances from the portions of the second bonding portion  22   b , as the trigger, other than the projected portions  22   e.    
     For this reason, the generation of the peeling force shown in  FIG. 6  at the second bonding portion  22   b  can be suppressed, so that it becomes possible to reduce the peeling force. Further, the most projected portions  22   e   1  of the projected portions  22   e  are disposed in the neighborhood of the longitudinal central portions of the openings  35   a . For this reason, the supporting force for supporting the developer bag  16  at the fixed portion  16   d  can be transmitted to the portions of the second bonding portion  22   b , other than the projected portions  22   e , through the openings  35   a.    
     When the rotation of the unsealing member  21  in the arrow C direction further advances, as shown from (b) of  FIG. 14  to (c) of  FIG. 14 , the unsealing of the projected portions  22   e  disposed in the neighborhood of the longitudinal central portions of the openings  35   a  advances. At this time, in the neighborhood of the longitudinal central portions of the openings  35   a  where the openings  35   a  are largely deformed, correspondingly to the projections of the projected portions  22   e  provided in the downstream side of the arrow E direction, it is possible to perform the unsealing in the position remote from the openings  35   a , and therefore the projected portions  22   e  can be peeled and thus the unsealing is completed. 
     Each of the openings  35   a  is remotest from the associated connecting portion  35   b  in a position in the neighborhood of the longitudinal central portion thereof. For this reason, the developer bag  16 —supporting force at the fixed portion  16   d  is not readily transmitted to the position, and the position is in the neighborhood of the longitudinal central portion of the opening  35   a  and therefore the opening  35   a  is liable to be deformed. Further, in the case where the width L 2  of the openings  35   a  with respect to the arrow E direction in which the unsealing advances is extremely larger than the width L 1  of each opening  35   a  with respect to the arrow F direction perpendicular to the arrow E direction, an amount of deformation of the opening  35   a , with respect to the arrow E direction, in the neighborhood of the longitudinal of the opening  35   a  becomes extremely larger than the (original) width L 2  with respect to the arrow E direction. 
     For this reason, the most projected portions  22   e   1  of the projected portions  22   e  are disposed in the neighborhood of the longitudinal central portions of the openings  35   a . As a result, correspondingly to the projections of the projected portions  22   e , it is possible to perform the unsealing in the position remote from the openings  35   a , so that a degree of the deformation of the openings  35   a  can be made small. Further, during the unsealing of the projected portions  22   e , with respect to the arrow F direction in  FIG. 14  perpendicular to the arrow E direction in  FIG. 14  in which the unsealing advances, a distance in which the peeling of the second bonding portion  22   b  is generated can be shortened, so that it is possible to suppress the peeling force. 
     In this way, the projected portions  22   e  projected toward the downstream side (upper side in  FIG. 14 ) with respect to the arrow E direction in which the unsealing of the second bonding portion  22   b  advances are provided. With respect to the arrow F direction in  FIG. 14  perpendicular to the arrow E direction in  FIG. 14 , the most projected portions  22   e   1  of the projected portions  22   e  are disposed in the neighborhood of the longitudinal central portions of the openings  35   a.    
     By employing such a constitution, it is possible to suppress the generation of the peak  40  of the peeling force shown in  FIG. 6  at the second bonding portion  22   b  to reduce the peeling force, so that it is possible to suppress the deformation of the openings  35   a  in the neighborhood of the longitudinal central portions of the openings  35   a . For this reason, the unsealing of the second bonding portion  22   b  can be advanced with reliability. Other constitutions are the same as those in the above-described embodiments, and a similar effect can be obtained. 
     [Embodiment 4] 
     Next, with reference to  FIG. 16 , a constitution of an image forming apparatus to which a process cartridge including a developer accommodating unit according to the present invention in Embodiment 4 is detachably mounted will be described. Incidentally, constituent elements similar to those in the above-described embodiment 5 are represented by the same reference numerals or symbols and will be omitted from description. 
     In the above-mentioned embodiments, each of the constitutions of the first bonding portion  22   a  and the second bonding portion  22   b  is described individually, but it is possible to obtain a similar effect also when the constitution of the first bonding portion  22   a  and the constitution of the second bonding portion  22   b  are used in combination. 
       FIG. 16  shows an example thereof.  FIG. 16  is a plan illustration showing a structure in the neighborhood of the openings  35   a  and the connecting portions  35   b  in this embodiment. Of the bonding portion  22 , the first bonding portion  22   a  is provided in the upstream side (lower side in  FIG. 16 ) with respect to the arrow E direction in  FIG. 16  as the unsealing direction of the openings  35   a  in the case where the structure is seen along the surface of the sealing member  19 . 
     The first bonding portion  22   a  is, similarly as in Embodiment 2 described above with reference to  FIG. 10 , provided with the recessed portions  22   d  recessed toward the downstream side (upper side in  FIG. 16 ) with respect to the arrow E direction in  FIG. 16  in which the unsealing advances. Further, most recessed portions  22   d   1  at least as a part of the recessed portions  22   d  are provided so as to enter the region of the connecting portions  35   b.    
     The second bonding portions  22   b  which is the bonding portion  22  in the downstream side (upper side in  FIG. 16 ) with respect to the arrow E direction in  FIG. 16  as the unsealing direction and which opposes the first bonding portion  22   a  via the openings  35   a  is provided. The second bonding portion  22   b  is provided with the projected portions  22   e  projected toward the downstream side (upper side in  FIG. 16 ) with respect to the arrow E direction in which the unsealing advances, similarly as in Embodiment 3 described above with reference to  FIG. 12 . Further, the most projected portions  22   e   1  of the projected portions  22   e  are disposed in the neighborhood of the longitudinal central portions of the openings  35   a.    
     Also in such a constitution, during the peeling of the first bonding portion  22   a , it is possible to perform the unsealing from the projected portions, each as the trigger and each having a predetermined width, other than the recessed portions  22   d , so that the generation of the peak  40  of the peeling force shown in  FIG. 6  can be suppressed to reduce the peeling force. 
     Further, the most recessed portions of the recessed portions  22   d  of the first bonding portion  22   a  are provided so as to enter the region of the connecting portions  35   b , so that as descried above with reference to  FIG. 11 , the volume of the corner portion  16   e  of the developer bag  16  can be optimized so as to be minimized. For this reason, it becomes possible to minimize the amount of the developer  99  remaining in the corner portion  16   e  of the developer bag  16 . 
     Further, during the peeling of the second bonding portion  22   b , it is possible to suppress the generation of the peak  40  of the peeling force shown in  FIG. 6  at the second bonding portion  22   b  to reduce the peeling force, so that it is possible to suppress the deformation of the openings  35   a  in the neighborhood of the longitudinal central portions of the openings  35   a . For this reason, the unsealing of the second bonding portion  22   b  can be advanced with reliability. Other constitutions are the same as those in the above-described embodiments, and a similar effect can be obtained. 
     [Embodiment 5] 
     Next, with reference to  FIG. 17 , a constitution of an image forming apparatus to which a process cartridge including a developer accommodating unit according to the present invention in Embodiment 5 is detachably mounted will be described. Incidentally, constituent elements similar to those in the above-described embodiment 5 are represented by the same reference numerals or symbols and will be omitted from description. 
       FIG. 16  is a plan illustration showing a structure in the neighborhood of the openings  35   a  and the connecting portions  35   b  in this embodiment. In this embodiment, as shown in  FIG. 17 , of the bonding portion  22  surrounding the openings  35   a , the first bonding portion  22   a  is provided in the upstream side (lower side in  FIG. 17 ) with respect to the arrow E direction in  FIG. 17  as the unsealing direction of the openings  35   a  in the case where the structure is seen along the surface of the sealing member  19 . Further, the second bonding portion  22   b  in the downstream side (upper side in  FIG. 17  with respect to the arrow E direction in  FIG. 17  as the unsealing direction of the openings  35   a  is provided. Further, a plurality of projected portions  34  are continuously provided and disposed in the plane of the first bonding portion  22   a  and the plane of the second bonding portion  22   b.    
     The projected portions  34  of the first bonding portion  22   a  and the projected portions  34  of the second bonding portion  22   b  are disposed in substantially parallel to a rectilinear line connecting the end portions of the unsealing member  21  where the unsealing member  21  is rotatably supported by the flame  18 , and a plurality of circular openings  35   a  are provided so that each circular opening  35   a  is disposed in a gap between opposing projected portions  34  of the first and second bonding portions  22   a  and  22   b.    
     In this embodiment, an example in which the projected portions  34  are disposed over the entire longitudinal direction of the first and second bonding portions  22   a  and  22   b  is shown. 
     Further, the projected portions  34  of the first bonding portion  22   a  and the projected portions  34  of the second bonding portion  22   b  are disposed in parallel to each other along the arrow F direction in  FIG. 17  perpendicular to the arrow E direction in  FIG. 17  as the unsealing direction. As a result, it is possible to dispose, in the gaps created between the first bonding portion  22   a  and the second bonding portion  22   b , it is possible to dispose the plurality of openings  35   a  through which the developer is to be discharged. Further, a bonding portion  22  including a continuous welding portion  44  where the first and second bonding portions  22   a  and  22   b  are connected with each other is provided. As a result, similarly as in the above-described embodiments, the sealing member  19  fixed to the unsealing member  21  is pulled, so that the developer bag  16  can be unsealed. 
     In this way, the first and second bonding portions  22   a  and  22   b  are partly connected with each other, so that the peeling of the first bonding portion  22   a  is easily propagated to the second bonding portion  22   b , so that continuous peeling can be performed and thus it becomes possible to further improve an unsealing property. 
     Incidentally, in the above-described embodiments, the example in the case where the developer bag  16  is provided with the plurality of openings  35   a  was explained. As another example, it is also possible to provide the developer bag  16  with a single opening  35   a  to be unsealed in a direction crossing the longitudinal direction of the developer accommodating unit. Other constitutions are the same as those in the above-described embodiments, and a similar effect can be obtained. 
     According to the above-described constitutions of the present invention, in the developer accommodating unit using the flexible container for accommodating the developer, it is possible to facilitate the unsealing of the sealing member for sealing the openings of the flexible container. 
     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 purpose of the improvements or the scope of the following claims. 
     This application claims priority from Japanese Patent Application No. 003261/2013 filed Jan. 11, 2013, which is hereby incorporated by reference.