hereinafter , embodiments of the present invention are described with reference to the appended drawings . however , the measurements , materials , and shapes of the structural components of the image forming apparatuses in the following embodiments of the present invention , and the positional relationship among the components , are not intended to limit the present invention in scope . they are to be altered as necessary , according to the structure of an apparatus to which the present invention is applied , and various conditions under which the apparatus is used . the image forming apparatus in this embodiment is an electrophotographic image forming apparatus ( which may be referred to simply as image forming apparatus , hereafter ). more specifically , it is an electrophotographic full - color image forming apparatus in which four process cartridges ( which may be referred to simply as cartridges ) are disposed . however , the number of the cartridges installable in the apparatus is not limited to four . it is to be set as necessary . for example , in the case of an image forming apparatus which forms a monochromatic image , the number of cartridges to be installed in the apparatus is one . although , the image forming apparatus in this embodiment is a full - color laser printer which is based on four primary colors and uses an electrophotographic process . however , this embodiment is not intended to limit the present invention in terms of an image forming apparatus to which the present invention is applicable . for example , the present invention is also applicable to a copying machine , a facsimile machine , and a multifunction machine capable of performing as a copying machine as well as a facsimile machine . first , referring to fig2 and 3 , the general structure of the image forming apparatus in the first embodiment is described . fig2 is a schematic sectional view of the image forming apparatus in this embodiment . fig3 ( a ) is an external perspective view of the process cartridge in the first embodiment . fig3 ( b ) is a schematic sectional view of the process cartridge in the first embodiment . this image forming apparatus 1 is a full - color laser printer which uses an electrophotographic image formation process , and is based on four primary colors . it forms a color image on a sheet s of recording medium . it employs the so - called process cartridge system . that is , it is structured so that process cartridges p ( py , pm , pc and pk ) ( which will be referred to simply as cartridges ) are removably installable in the main assembly 2 of the image forming apparatus to form a color image on a sheet s of recording medium . regarding the direction of the image forming apparatus 1 , the side of the image forming apparatus 1 , which is provided with a door 3 will be referred to as the front surface , and the opposite surface from the front surface will be referred to as the rear surface . further , the right and left sides of the image forming apparatus 1 , as seen from the front side , will be referred to as the drive side and non - drive side , respectively . fig2 is a sectional view of the image forming apparatus 1 , as seen from the non - drive side . thus , the front side of the sheet of paper which has fig2 corresponds to the non - drive side of the image forming apparatus 1 , and the left side of the sheet corresponds to the front side of the image forming apparatus 1 . further , the backside of the sheet corresponds to the drive side of the image forming apparatus 1 . referring to fig2 , there are disposed in the apparatus main assembly 2 , four cartridges p ( py , pm , pc and pk ), more specifically , the first , second , third , and fourth cartridges py , pm , pc and pk , respectively , being horizontally aligned in parallel . the first to fourth cartridges p ( py , pm , pc and pk ) have four electrophotographic image processing systems , one for one , which are the same in function . to the first to fourth cartridges p ( py , pm , pc and pk ), rotational driving force is transmitted from the driving force output portion ( unshown ) of the apparatus main assembly 2 . further , to the first to fourth cartridges p ( py , pm , pc and pk ), bias voltages ( charge bias , development bias , etc .) are supplied from the apparatus main assembly 2 . referring to fig3 ( a ), each of the first to fourth cartridges p ( py , pm , pc and pk ) in this embodiment has a photosensitive drum 4 as an image bearing member , and a cleaning unit 8 . the cleaning unit 8 is equipped with a charging means as a means which processes the photosensitive drum 4 , and a cleaning means . further , each of the cartridges p ( py , pm , pc and pk ) has a development device 9 equipped with a developing means for developing the electrostatic latent image on the photosensitive drum 4 . the cleaning unit 8 and development device 9 are in connection to each other . as the charging means , a charge roller 5 is used . as the cleaning means , a cleaning blade 7 is used . as a developing means , a development roller ( developer bearing component ) 6 is used . the first cartridge py stores toner of yellow ( y ) color , in its development frame 29 . it forms a toner image ( developer image ) of yellow color on the peripheral surface of the photosensitive drum 4 . the second cartridge pm stores toner of magenta ( m ) color in its development frame 29 . it forms a toner image of the color on its photosensitive drum 4 . the third cartridge pc stores toner of cyan ( c ) color in its development frame 29 . it forms a toner image of the cyan color on the peripheral surface of the photosensitive drum 4 . the fourth cartridge pk stores toner of black ( k ) color in its development frame 29 . it forms toner image of the black color on the peripheral surface of its photosensitive drum 4 . referring to fig2 , there is disposed a laser scanner unit lb as exposing means , above the combination of the first to fourth cartridges p ( py , pm , pc and pk ). this laser scanner unit lb outputs a beam z of laser light while modulating the beam z according to the information of the image to be formed . the beam z of laser light scans ( exposes ) the peripheral surface of the photosensitive drum 4 , through an exposure window 10 of the cartridge p . referring also to fig2 , there is disposed an intermediary transfer belt unit 11 , as a transfer component , below the combination of the first to fourth cartridges p ( py , pm , pc and pk ). this intermediary transfer belt unit 11 has : a flexible endless belt 12 ; and a combination of a driver roller 13 , a turn roller 14 , and a tension roller 15 , by which the endless belt 12 is suspended and kept tensioned . the transfer belt 12 is circularly movable in the direction indicated by an arrow mark c in fig1 . the photosensitive drum 4 in each of the cartridges p ( py , pm , pc and pk ) is in contact with the top surface of the belt 12 , by the downwardly facing portion of its peripheral surface . the area of contact between the photosensitive drum 4 , and the belt 12 , is the primary transfer station . there are disposed the primary transfer rollers 16 on the inward side of the loop which the transfer belt 12 forms , in such a manner that they are pressed against the photosensitive drums 4 one for one , with the presence of the belt 12 between them and photosensitive drums 4 . against the turn roller 14 , the secondary transfer roller 17 is kept pressed , with the presence of the transfer belt 12 between the turn roller 14 and secondary transfer roller 17 . the area of contact between the secondary transfer roller 17 and belt 12 is the secondary transfer station . referring also to fig2 , there is disposed a sheet feeding / conveying unit 18 below the intermediary transfer belt unit 11 . this sheet feeding / conveying unit 18 has : a sheet feeder tray 19 , in which multiple sheets s of recording medium are stored in layers ; and a sheet feeder roller 20 . there is disposed in the top left section of the apparatus main assembly 2 , a fixation unit 21 and a discharge unit 22 . a part of the top surface of the apparatus main assembly 2 is used as a delivery tray 23 . to the sheet s of recording medium , a toner image is fixed by the fixing means with which the fixation unit 21 is provided . then , the sheet s is discharged into the delivery tray 23 . incidentally , the image forming apparatus 1 in the first embodiment is structured so that it forms an image with the use of the removably installable cartridge p which is equipped with the photosensitive drum 4 , and the cleaning unit 8 having the charging means and cleaning means . however , the structure of the image forming apparatus 1 may be different from the one in this embodiment . for example , the image forming apparatus 1 may be structured so that its main assembly 2 is equipped with one or more photosensitive drums 4 and charging means , and also , so that it forms an image with the use of a removably installable cartridge ( p ) equipped with a cleaning unit having the cleaning means . next , referring to fig2 and 3 , the image forming operation of the image forming apparatus 1 in this embodiment is described . first , the photosensitive drum 4 in each of the first to fourth cartridges p ( py , pm , pc and pk ) is rotationally driven at a preset speed in the counterclockwise direction in fig2 ( direction indicated by arrow mark d in fig3 ( b )). the laser scanner unit lb also is driven . in synchronism with this driving of the laser scanner unit lb , the charge roller 5 in each cartridge p uniformly charges the peripheral surface of the photosensitive drum 4 to preset polarity and a preset potential level . the laser scanner unit lb scans ( exposes ) the peripheral surface of the photosensitive drum 4 with the beam z of laser light it outputs while modulating the beam z with the image formation signals which correspond one for one to the monochromatic toner images , different in color , into which the original has been separated . consequently , an electrostatic latent image , which reflects the image formation signals of the corresponding color is formed on the peripheral surface of the photosensitive drum 4 . the formed electrostatic latent image is developed by the development roller 6 , which is being rotationally driven at a preset speed ( clockwise direction in fig2 ; direction indicated by arrow mark e in fig3 ( b )). through the electrophotographic image formation process described above , a toner image of the yellow color , which corresponds to the yellow color component of the full - color image , is formed on the photosensitive drum 4 of the first cartridge py . then , the toner image is transferred ( primary transfer ) onto the transfer belt 12 . similarly , on the peripheral surface of the photosensitive drum 4 of the second cartridge pm , a toner image of the magenta color , which corresponds to the magenta color component of the full - color image , is formed . then , the toner image of the magenta color is transferred ( primary transfer ) onto the transfer belt 12 in such a manner that it is laid upon the toner image of the yellow color , which has just been transferred ( primary transfer ) onto the transfer belt 12 . further , on the peripheral surface of the photosensitive drum 4 of the third cartridge pc , a toner image of the cyan color , which corresponds to the cyan color component of the full - color image , is formed . then , the toner image is transferred ( primary transfer ) onto the transfer belt 12 in such a manner that it is laid upon the combination of the toner image of the yellow color , and the toner image of the magenta color , which have just been transferred ( primary transfer ) onto the transfer belt 12 . further , on the peripheral surface of the photosensitive drum 4 of the fourth cartridge pk , a toner image of the black color , which corresponds to the black color component of the full - color image , is formed . then , the toner image is transferred ( primary transfer ) onto the transfer belt 12 in such a manner that it is laid upon the combination of the yellow , magenta , and cyan color images , which have just been transferred ( primary transfer ) onto the transfer belt 12 . consequently , an unfixed full - color image is synthetically effected on the transfer belt 12 , by the toner images of the yellow , magenta , cyan and black colors . meanwhile , the sheets s of recording medium begin to be conveyed one by one while being separated from the rest with a preset control timing . then , each sheet s is introduced into the secondary transfer station , which is the area of contact between the secondary transfer roller 17 and transfer belt 12 with a preset control timing . thus , the four toner images , different in color , layered on the transfer belt 12 are transferred together onto the surface of the sheet s while the sheet s is conveyed through the secondary transfer station , as if they are peeled away from the transfer belt 12 . thereafter , the sheet s of recording medium , onto which the toner images , different in color , have just been transferred , is conveyed to the fixation unit 21 , in which it is subjected to pressure and heat . thus , the toner images are fixed to the sheet s . after the fixation of the toner images , the sheet s is discharged into the delivery tray 23 by the discharge unit 22 , ending thereby the image formation sequence described above . referring to fig3 ( a ), each of the cartridges p ( py , pm , pc and pk ) are roughly in the form of a rectangle parallelepiped , the lengthwise direction of which is parallel to the direction of the rotational axis a of the photosensitive drum 4 ( axial line direction ). each cartridge p has a cleaning unit 8 , a development device 9 , a cover 24 on the drive side , a cover 25 on the non - drive side . next , referring to fig3 and 4 , the structure of the cleaning unit is described . fig4 is an exploded perspective view of the cleaning unit in the first embodiment . referring to fig3 ( b ), the cleaning unit 8 is made up of the photosensitive drum 4 , charge roller 5 , cleaning blade 7 , and cleaning unit frame 26 which supports the photosensitive drum 4 , charge roller 5 , and cleaning blade 7 . referring to fig3 ( a ), the photosensitive drum 4 is rotatably supported by the drive side cover 24 and non - drive side cover 25 . it rotates ( in direction indicated by arrow mark d in fig3 ( b )) by obtaining the driving force of the motor ( unshown ) of the apparatus main assembly 2 through the drum drive coupling 4 a . next , referring to fig4 , the charge roller 5 is rotatably supported by the pair of charge roller bearings 27 r and 27 l ( unshown ), on the non - drive and drive sides , respectively , of the cleaning unit frame 26 , by its lengthwise end portions . it is kept in contact with the peripheral surface of the photosensitive drum 4 , being thereby rotated by the rotation of the photosensitive drum 4 . it charges the peripheral surface of the photosensitive drum 4 by being supplied with charge bias . in order to ensure that the peripheral surface of the photosensitive drum 4 is uniformly charged , the lengthwise ends of the charge roller 5 are pressed upon the peripheral surface of the photosensitive drum 4 , by a pair of compression springs 28 r and 28 l ( unshown ), one for one . the cleaning blade 7 is fixed to the blade supporting surface 26 c of the cleaning unit frame 26 , and is placed in contact with the peripheral surface of the photosensitive drum 4 by its cleaning edge , in such an attitude that its cleaning edge is placed in contact with the peripheral surface of the photosensitive drum 4 in the counter direction relative to the rotational direction ( direction indicated by arrow mark d in fig3 ( b )). the cleaning blade 7 cleans the peripheral surface of the photosensitive drum 4 by scraping away the transfer residual toner remaining on the peripheral surface of the photosensitive drum 4 ( image bearing component ) during image formation . in order to ensure that the transfer residual toner is completely scraped away , the cleaning edge of the cleaning blade 7 is kept pressed upon the peripheral surface of the photosensitive drum 4 with the application of a preset amount of pressure . further , the transfer residual toner scraped away from the peripheral surface of the photosensitive drum 4 by the cleaning blade 7 is stored as waste toner , in the waste toner storage 26 a of the cleaning unit frame 26 . therefore , the cleaning unit frame 26 is provided with a waste toner recovery sheet 44 , end seals 45 r and 45 l as the second seals , and elastic components 46 r and 46 l as the first seals , which are for preventing the waste toner from leaking out of the cleaning unit frame 26 . it is not mandatory that the cleaning unit frame 26 is provided with the waste toner storage 26 a . for example , the image forming apparatus 1 may be structured so that the cleaning unit 8 is provided with a mechanism for conveying the waste toner , to store the waste toner in the waste toner storage located outside the cleaning unit frame 26 . the detailed structure of the waste toner seal is described later . referring to fig3 ( b ), the development device 9 is in the form of a rectangular parallelepiped , the lengthwise direction of which is parallel to the direction of the rotational axis of the development roller 6 as a developer bearing member . the development device 9 has a development device frame 29 , a development blade 31 , a developer supply roller 33 , in addition to the development roller 6 . the development device frame 29 has a toner storage 29 c in which toner is stored , and an opening 29 c through which toner is discharged from the toner storage 29 c . the development roller 6 and developer supply roller 33 are positioned at the opening of the development frame 29 , and the lengthwise ends of the development roller 6 , and the lengthwise ends of the developer supply roller 33 , are rotatably supported by the bearings ( unshown ) attached to the corresponding lateral walls of the development device frame 29 . the development blade unit 30 is a unit made up of a development blade 31 , and a blade supporting metallic plate 32 to which the development blade 31 is fixed . the blade supporting metallic plate 33 is fixed to the development device frame 29 with small screws . the development blade 31 is a piece of thin and elastic metallic plate , which is roughly 0 . 1 mm in thickness . it is positioned in contact with the peripheral surface of the development roller 6 in the counter direction with reference to the rotational direction ( indicated by arrow mark e in fig3 ( b )). the flexible sheet 35 is positioned so that it contacts the peripheral surface of the development roller 6 , on the opposite side of the development device frame 29 from where the development blade 31 is in contact with the development roller 6 . it prevents toner from leaking through the gap between the development device frame 29 and development roller 6 . the development device 9 is kept pressured by the compression springs ( unshown ) in such a direction that it is pivotally moved about the pivot ( axial line b ) shown in fig3 ( a ) in the direction ( indicated by arrow mark g in fig3 ( b )) to place the development roller 6 in contact with the photosensitive drum 4 . when an image is formed , the developer supply roller 33 and development roller 6 are rotationally driven while rubbing against each other . thus , the toner is borne on the development roller 6 . the development blade 31 regulates in thickness the toner layer formed on the peripheral surface of the development roller 6 , and also , gives toner triboelectric charge in the area of contact between itself and development roller 6 , by being kept pressed upon the development roller 6 . thus , the charged toner on the development roller 6 adhere to the electrostatic latent image on the photosensitive drum 4 , developing thereby the latent image , in the area of contact between the development roller 6 and photosensitive drum 4 . next , referring to fig5 , the structure of the cleaning blade in the first embodiment is described . fig5 ( a ) is an external perspective view of the cleaning blade in this embodiment , and fig5 ( b ) is a schematic sectional view of the cleaning blade 7 in the first embodiment . the two - dot chain line in fig5 ( b ) shows the contour of the photosensitive drum 4 . referring to fig5 ( a ) and 5 ( b ), the cleaning blade 7 has an elastic blade section 7 a , and a support section 7 b which supports the elastic blade section 7 a . hereafter , various sections of the cleaning blade 7 are referred to as follows : the surface of the cleaning blade 7 , by which the blade 7 contacts the photosensitive drum 4 is referred to as the top surface 7 d . the side of the cleaning blade 7 , in terms of the widthwise direction of the cleaning blade 7 , by which the blade section 7 a contacts the photosensitive drum 4 is referred to as the edge side . the surface of the cleaning blade 7 , which is on the edge side , and is perpendicular to the top surface 7 d , is referred to as the end surface 7 e . the surfaces of the cleaning blade 7 , which are at the lengthwise ends of the cleaning blade 7 , one for one , and are perpendicular to the top surface 7 d , are referred to as the lengthwise end surfaces 7 f r and 7 f l . the surface of the cleaning blade 7 , which are the opposite surface from the top surface 7 d , and which the elastic components 46 r and 46 l contact , is referred to as bottom surface 7 g . further , the direction which is parallel to the top surface 7 d and perpendicular to the lengthwise direction is referred to as the widthwise direction ( indicated by arrow mark d in fig5 ( a ) and 5 ( b )). the blade section 7 a is made of an elastic substance , and contacts the photosensitive drum 4 . it is fixed to the blade support section 7 b with adhesive , or the blade support section 7 b is formed as an integral part of the blade section 7 a . the elastic blade section 7 a removes the transfer residual toner from the photosensitive drum 4 by being placed in contact with the photosensitive drum 4 , by this edge side , in such a manner that its extends from one lengthwise end of the photosensitive drum 4 to the other . as the material for the elastic blade section 7 a , natural rubber , and synthetic rubber such as urethane rubber , can be listed . the support section 7 b is formed of steel plate ( made of iron , for example ) which is 0 . 5 - 2 . 0 mm in thickness . it is fixed to the blade supporting surface 26 c ( fig4 ) of the cleaning unit frame 26 . further , in order to minimize the deformation of the cleaning blade 7 in the direction perpendicular to the lengthwise direction , the support section 7 b is provided with a sub - section 7 c which is perpendicular to the lengthwise direction of the cleaning blade 7 , to increase the cleaning blade 7 in rigidity . however , if the support section 7 b is rigid enough to resist the force which works in the direction to deform the support section 7 b , the sub - section 7 c is unnecessary . for example , the support section 7 b may be increased in rigidity by increasing it in thickness , and / or using a stronger substance such as stainless steel , as the material for the support section 7 b . next , referring to fig6 , the structure of the end seal as the second seal in the first embodiment is described . referring to fig6 , in the first embodiment , the end seal 45 r is roughly l - shaped in cross section , and has a protrusive portion 45 a r which protrudes by a length l from the main section of the end seal 45 r . the end seal 45 r is made up of a surface layer 45 e r , an adhesive layer 45 f r , an intermediary layer 45 g r , and an adhesive layer 45 h r . that is , the end seal 45 r is shaped so that as it is attached to the cleaning unit , the protrusive portion 45 a r extends outward of the cleaning unit 8 beyond the lengthwise end surface 7 f r in the lengthwise direction , and extends further from the cleaning edge of the cleaning blade 7 toward the base side of the cleaning blade 7 . providing the end seal 45 r with the protrusive portion 45 a r makes it possible to prevent the waste toner from leaking from the cleaning unit frame 26 . fig6 shows only an example of the structure of the end seal 45 . that is , the dimension l of the protrusive portion 45 a may be less than the one shown in fig6 . further , as long as the sealing edge of the cleaning blade 7 is satisfactory in terms of sealing performance , it is not mandatory that the end seal 45 r is provided with the protrusive portion 45 a . the surface layer 45 e r is made up of a substrative cloth and multiple upright strands of fiber which are implanted in the substrative cloth . however , the surface layer 45 e r may be made up of the substrative cloth alone . the surface layer 45 e r is attached to the surface of the intermediary layer 45 g r with the placement of the adhesive layer 45 f r , for example , a piece of two - sided adhesive tape , a layer of adhesive , or the like , between the surface layer 45 e r and intermediary layer 45 g r . the material for the substrative cloth may be a piece of cloth woven of warp and weft , a piece of cloth knitted of thread , a piece of nonwoven cloth made by joining strands of fiber , and the like . as for the method for making nonwoven cloth , there are the method for joining strands of fiber by blowing heated steam at the strands , method for joining strands of fiber by thermally melting the strands , method for making strands of fiber entangle by highly pressurized streams of water , and the like . as for the type of pile , the strands may be in the form of a loop , or multiple upright strands . further , in a case where the end seal 45 is formed of the substrative cloth alone , strands of fiber may be electrostatically implanted upright on the surface of the substrative cloth . as the material for the surface layer 45 e r , synthetic fiber made of polyethylene , polypropylene , polyester , nylon , acrylic resin , polyethylene - terephthalate , or the like , semi - synthetic fiber made of rayon or the like , natural fiber such as cotton , may be used . further , the combination of the preceding materials , and the twined version of the preceding fibers , may also be listed as the material for the strands . further , the surface layer 45 e r may be coated with lubricant such as silicone resin , zink stearate . that is , the material for the surface layer 45 e r may be those other than the above listed ones , as long as they are excellent in heat resistance , durability , and friction resistance , and is satisfactory in the strength of its adhesion to the adhesive layer 45 f r . the intermediary layer 45 g r is a cushion layer formed of an elastic substance . as the material for the intermediary layer 45 g r , a foamed version of synthetic resin such as polyurethane , and also , synthetic rubber , natural rubber , thermoplastic elastomer , etc , may be used . the material for the intermediary layer 45 g r may be other substances than the above listed ones , as long as they are excellent in heat resistance and durability , and satisfactory in the strength of adhesion to the adhesive layer 45 h r . the adhesive layer 45 h r is on the back surface of the intermediary layer 45 g r , and is formed of two - sided adhesive tape , pressure sensitive adhesive , or the like . the surface of the adhesive layer 45 h r , by which the adhesive layer 45 h r is adhered to the development device frame 29 , will be referred to as the adhesion surface 45 b r . the material for the adhesive layer 45 h r may be other material than the abovementioned ones , as long as it allows the adhesive layer 45 h r to be flexible and is adherent enough to ensure that the adhesive layer 45 h r remains adhered to the intermediary layer 45 g r and development device frame 29 . the end seal 45 r in the first embodiment , which is made up of four layers , that is , the surface layer 45 e r , adhesive layer 45 f r , intermediary layer 45 g r , and adhesion layer 45 h r , is an example of the end seal 45 which is in accordance with the present invention . however , the end seal 45 r may be made up of only two layers , that is , the surface layer 45 e r and adhesive layer 45 h r . in such a case , the surface layer 45 e r has to be given a certain amount of thickness , with the use of nonwoven cloth as the material for the substrative cloth 45 e r . incidentally , the end seal 45 l ( fig4 ) is symmetrically shaped relative to the end seal 45 r , and the same in structure as the end seal 45 r . therefore , it is not described . next , referring to fig4 , the structural arrangement for keeping the waste toner storage sealed is described . in order to prevent the waste toner stored in the waste toner storage 26 a of the cleaning unit frame 26 from leaking , the cleaning unit frame 26 is provided with the waste toner recovery sheet 44 , pair of end seals 45 r and 45 l as the second seals , and pair of elastic components 46 r and 46 l as the first sealing components . the waste toner recovery sheet 44 is a flexible sheet which prevents the waste toner from leaking through the gap between the cleaning unit frame 26 and photosensitive drum 4 in terms of the widthwise direction . the waste toner recovery sheet 44 is disposed so that it contacts the peripheral surface of the photosensitive drum 4 , on the opposite side of the cleaning unit frame 26 , from where the cleaning blade 7 contacts the photosensitive drum 4 . next , referring to fig4 , 7 and 8 , the elastic components 46 r and 46 l are described . fig7 ( a ) is a drawing which shows the state of the right end of the cleaning blade 7 and its adjacencies , after the elastic component 46 r was formed in the cleaning unit frame 26 by injection molding , and before the cleaning blade 7 and end seal 45 r are attached to the cleaning unit frame 26 . fig7 ( b ) is a drawing which shows the state of the right end of the cleaning blade 7 and its adjacencies . it shows the structural arrangement for keeping the cleaning unit frame 26 sealed at the lengthwise right end of the cleaning unit frame 26 . referring to fig7 ( a ), the portion of the cleaning unit frame 26 , to which the end seal 45 r is attached is indicated by a two - dot chain line . incidentally , the elastic components 46 r and 46 l are the same in shape , although they are symmetrically positioned relative to each other . therefore , only the elastic component 46 r , which is on the non - driven side is described . in the first embodiment , the elastic component 46 r is formed of resinous material , more specifically , thermoplastic elastomer . it is formed by injection molding , which is a method for molding a component by injecting melted resin into a gap formed by affixing a mold to the cleaning unit frame 26 . referring to fig7 ( b ), the elastic component 46 r is positioned 0 - 10 mm away toward the center of the cleaning blade 7 , from the lengthwise end surface 7 f r of the cleaning blade 7 . further , referring to fig7 ( a ), the elastic component 46 r has a cleaning blade contacting vertical section 46 d r ( which may be referred to simply as vertical sealing section ), and an end seal attachment section ( which may be referred to simply as bearing section ) 46 b r to which the end seal 45 r is attached . the vertical seal section 45 d r of the elastic component 46 r prevents the waste toner from leaking through the gaps which are present between the lengthwise ends of the cleaning blade 7 and the corresponding lengthwise ends of the cleaning unit frame 26 . the detail of the shape of the elastic component 46 r is described later . the end seals 45 r and 45 l are disposed in contact with the elastic components 46 r and 45 l , remaining compressed by the photosensitive drum 4 and cleaning unit frame 26 , at the lengthwise ends of the cleaning blade 7 . the end seal 45 r prevents the waste toner from leaking through the gaps created by the cleaning blade 7 , photosensitive drum 4 , elastic component 45 r , and cleaning unit frame 26 . next , referring to fig1 , 7 and 8 , the sequential steps through which the abovementioned components are assembled to prevent the waste toner from leaking from the gaps which are present at the lengthwise ends of the cleaning blade 7 are described . here , the steps are described with reference to the non - drive side of the cleaning unit . fig1 ( a ) is a schematic sectional view of the right end seal 45 r and its adjacencies , at a plane a - a in fig7 ( a ). fig1 ( b ) is a schematic sectional view of the right end seal 45 r , at a plane b - b in fig7 ( b ). it shows the state of the right end seal 45 r after the cleaning blade 7 was attached to the cleaning unit frame 26 . fig1 ( c ) is a schematic sectional view of the right end seal 45 r , at a plane b - b in fig7 ( b ). it shows the state of the end seal 45 r after the photosensitive drum 4 was attached to the cleaning unit frame 26 . fig1 ( d ) is an enlarged view of the right end seal 45 r and its adjacencies shown in fig1 ( c ). fig8 is a perspective view of the elastic component 46 r and its adjacencies , after the attachment of the elastic component 46 r to the cleaning unit frame 26 . hereafter , the lengthwise and widthwise directions of the cleaning unit frame 26 will be referred to as directions x and y , respectively , and the direction perpendicular to the directions x and y will be referred to as the direction z ( directions indicated by arrow marks x , y , and z are their positive directions ). first , the elastic component 46 r is formed by injection molding . referring to fig8 , the elastic component 46 r is in the form of a t - shaped rib , the horizontal and vertical sections of which are parallel to the directions y and x , respectively . it has the vertical sealing section 46 d r for sealing the gap between the cleaning blade 7 and cleaning unit frame 26 , and an end seal bearing deformable section 46 b r , to which the end seal 45 r is pasted . next , referring to fig7 ( b ), the width l 3 of the end seal bearing section 46 b r is greater than the width l 4 of the vertical sealing section 46 d r . next , referring to fig8 and 1 ( a ), the end seal bearing section 46 b r of the elastic component 46 r , which is the end portion of the elastic component 46 r in terms of the direction y , has the top surface 46 b 1 r , a contacting surface 46 b 2 r , and a proximity surface 46 b 3 r . the top surface 46 b 1 r is airtightly in contact with the elastic component contacting front section 26 b r of the cleaning unit frame 26 . the contacting surface 46 b 2 r is in contact with the adhesion surface 45 b r of the end seal 45 r . the proximity surface 46 b 3 r is parallel to the direction − y , and is next to the vertical sealing section 46 d r . the state in which the end seal bearing section 46 b r of the elastic component 46 r was before its deformation is shown in fig1 ( a ). the end seal bearing section 46 b r is roughly in the form of a trapezoid , being shaped so that its contacting surface 46 b 2 r is tilted in such a direction that the thickness of the end seal bearing section 46 b r in terms of the direction z gradually increases from the top surface side , at which it is h 1 , toward the proximity surface side , at which it is h 2 . that is , the closer to the end surface 7 e of the cleaning blade 7 , the thicker the end seal bearing section 46 b r . referring to fig1 ( a ), the elastic component 46 r is formed by injection molding so that the rear end surface 46 c r of the elastic component 46 r in terms of the direction − y airtightly contacts with the elastic component contacting rear section 26 d r of the cleaning unit frame 26 , and also , so that in terms of the direction z , the top surface 46 d 1 r of the vertical sealing section 46 d r will be above the cleaning blade supporting surface 26 c of the cleaning unit frame 26 by a distance j . referring to fig7 ( b ), etc ., the end seal 45 r is placed on the seal contacting surface 46 b 2 r of the elastic component 46 r . the width of the area of contact between the elastic component 46 r and end seal 45 r is u . next , the steps through which the cleaning blade 7 is attached to the cleaning unit frame 26 are described following the sequence in which they are performed . referring to fig1 ( b ), the two - dot chain lines indicate the contours of the cleaning blade 7 and end seal 45 r immediately before the cleaning blade 7 and end seal 45 r are attached to the cleaning unit frame 26 . the cleaning blade 7 is attached to the cleaning unit frame 26 in the direction indicated by an arrow mark k in fig1 ( b ) so that it overlaps with the adhesion surface 45 b r of the end seal 45 r in terms of the direction y . at this point , there is a gap t 1 between the top edge 45 e 1 r of the surface layer 45 e r of the end seal 45 , and the end surface 7 e of the cleaning blade 7 . & lt ; sealing of gap between cleaning blade and vertical sealing section of elastic component & gt ; referring to fig1 ( a ), the elastic component 46 is formed by injection molding in such a shape and a size that after the assembly of cleaning unit , the top surface 46 d 1 r of the vertical sealing section 46 d r of the elastic component 46 is above the cleaning blade supporting surface 26 c in terms of the direction z . therefore , the vertical sealing section 46 d r comes into contact with the bottom surface 5 g and support section 7 b of the cleaning blade 7 , and is squashed ( compressed ) by them . at this time , how the area of contact between the cleaning blade 7 and the vertical sealing section 46 d r is sealed is described . the elastic component 46 r is made of an elastic substance . therefore , as the cleaning blade 7 is attached to the cleaning unit frame 26 , the elastic component 46 r is deformed by the cleaning blade 7 in such a manner that it conforms in shape to both the bottom surface 7 g and support section 7 b of the cleaning blade 7 . therefore , no gap is created between the cleaning blade 7 and the vertical sealing section 46 d r . further , the elastic component 46 r made of thermoplastic elastomer is sticky , and therefore , it airtightly contacts ( sticks to ) the cleaning blade 7 . in other words , the area of contact between the elastic component 46 r and cleaning blade 7 remains airtightly sealed . therefore , it is possible to reduce the width l 4 of the vertical sealing section 46 d r of the elastic component 46 r as shown in fig7 . next , how the area of contact between the cleaning blade 7 and end seal 45 r is sealed is described . referring to fig1 ( b ), the end seal 45 r is pressed by the cleaning blade 7 . as it is pressed , the end seal bearing section 46 b r of the elastic component 46 r , which is deformable , is subjected , through the end seal 45 r , to the force generated in the direction k as the cleaning blade 7 is moved in the direction k to be attached to the cleaning unit frame 26 . referring to fig7 , the width l 4 of the vertical sealing section 46 d r , which is adjacent to the end seal bearing section 46 b r , is less than the width l 3 of the end seal bearing section 46 b r . therefore , there is provided a space for allowing the end seal bearing section 46 b r to extend in the direction y , which is parallel to the proximity surface 46 b 3 r of the elastic component 46 r , as the end seal bearing section 46 b r is compressed . thus , as the elastic component 46 r is compressed by the cleaning blade 7 , the end seal bearing section 46 b r of the elastic component 46 r substantially extends into the abovementioned space in the direction parallel to the proximity surface 46 b 3 r . consequently , the proximity surface 46 b 3 r of the elastic component 46 r , and the ridge ( intersection ) 46 f r between the proximity surface 46 b 3 r and contacting surface 46 b 2 r is moved by a distance m in the direction indicated by an arrow mark n , due to the deformation of the elastic component 46 r . therefore , the end seal 45 r attached to the end seal bearing section 46 b r of the elastic component 46 r is moved by a distance m in the direction indicated by the arrow mark n by the deformation of the elastic component 46 r as shown in fig1 ( b ), being thereby positioned close to the cleaning edge 7 e of the cleaning blade 7 . that is , the gap t 1 between the end surface 7 e of the cleaning blade 7 and the ridge 45 e 1 r of the surface layer 45 e r of the end seal 45 r is reduced . fig1 ( c ) shows the state in which the end seal 45 r , elastic component 46 r , cleaning blade 7 , and photosensitive drum 4 are immediately after the attachment of the photosensitive drum 4 to the cleaning unit frame 26 . the two - dot chain line in fig1 ( c ) indicates the contour of the cleaning blade 7 and end seal 45 r before the attachment of the photosensitive drum 4 to the cleaning unit frame 26 . the blade contacting portion ( surface ) 45 d r of the end seal 45 r is in contact with the end surface 7 e of the cleaning blade 7 , and the surface layer 45 e r is in contact with the photosensitive drum 4 . as the photosensitive drum 4 is attached to the cleaning unit frame 26 , the end seal bearing section 46 b r of the elastic component 46 r is compressed , through the end seal 45 r , by the photosensitive drum 4 , being thereby deformed . consequently , it is moved in the direction indicated by the arrow mark n . thus , the gap t 1 between the end surface 7 e of the cleaning blade 7 and the ridge 45 e 1 r of the surface layer 45 e r , reduces to a gap t 2 . further , the end surface 7 e comes into contact with the end seal 45 r . as described above , the end seal 45 r seals the gap created by the end seal 45 r , cleaning blade 7 , photosensitive drum 4 , and cleaning unit frame 26 , in terms of the lengthwise direction , improving thereby the cleaning unit in terms of the prevention of the waste toner leakage . fig1 ( d ) shows in detail the state of the end surface 7 e of the cleaning blade 7 , and its adjacencies , while the photosensitive drum 4 is rotated . the two - dot chain line in fig1 ( d ) indicated the contour of the end seal 45 r before the photosensitive drum 4 begins to be rotated . the photosensitive drum 4 rotates in the direction indicated by an arrow mark d . the end surface 7 e of the cleaning blade 7 is deformed by the friction between the cleaning blade 7 and photosensitive drum 4 , being thereby shifted downstream in terms of the rotational direction of the photosensitive drum 4 . the rotational force of the photosensitive drum 4 is applied by the friction between the end seal 45 r and photosensitive drum 4 , to the end seal 45 r , which is on the upstream side of the end surface 7 e of the cleaning blade 7 in terms of the rotational direction of the photosensitive drum 4 in the area in which the residual toner is removed from the photosensitive drum 4 . thus , the end seal 45 r is moved by the friction in the direction indicated by the arrow mark d . the end seal 45 r is compressed also in the circumferential direction of the photosensitive drum 4 by the cleaning blade 7 and photosensitive drum 4 . therefore , the end seal 45 r extends in the direction indicated by the arrow mark d , following the movement of the end surface 7 e of the cleaning blade 7 . further , the adhesion surface 45 b r of the end seal 45 r and the top surface 45 b 1 r of the end seal 45 r is moved in the direction indicated by the arrow mark d by the force applied to the end seal 45 r . thus , the end seal 45 r extends along the end surface 7 e of the cleaning blade 7 , preventing thereby the gap t 2 from increasing . further , as the photosensitive drum 4 rotates , the end seal 45 r , which is remaining compressed , expands ( extends ), ensuring that the surface of the end seal 45 r , which is parallel to the direction + y , remains in contact with the cleaning unit frame 26 . regarding the prevention of the waste toner leakage , the cleaning unit can be improved by reducing the gap between the cleaning blade 7 and end seal 45 r . however , if the distance between the portion of the elastic component 46 r , to which the end seal 45 r is adhered , and the end surface 7 e of the cleaning blade 7 , is simply reduced , it becomes likely for the cleaning blade 7 to run onto the surface layer 45 e r of the end seal 45 r when the cleaning blade 7 is attached . as the cleaning blade 7 runs onto the surface layer 45 e r , a gap is created between the photosensitive drum 4 and end seal 45 r . this gap allows the waste toner to pass between the photosensitive drum 4 and end seal 45 r , and leaks from the cleaning unit 8 . in the first embodiment , the end seal bearing section 46 b r of the elastic component 46 r , which has the surface to which the end seal 45 r is pasted , is deformable by the attachment of the cleaning blade 7 . therefore , as the elastic component 46 r is compressively deformed between the photosensitive drum 4 and cleaning unit frame 26 , it can reduce the gap t between the cleaning blade 7 and end seal 45 r . thus , the first embodiment can make it possible to better seal the cleaning unit 8 to prevent the waste toner from leaking , without reducing the cleaning unit 8 in assembly efficiency . also in the first embodiment , the elastic component 46 r is made of thermoplastic elastomer , by injection molding , so that the end seal bearing section 46 b r having the surface to which the end seal 45 r is adhered , will be formed of thermoplastic elastomer . with the use of thermoplastic elastomer as the material for the elastic component 46 r , the gap t between the cleaning blade 7 and end seal 45 r can be reduced by the attachment of the cleaning blade 7 and photosensitive drum 4 to the cleaning unit frame 26 . therefore , the cleaning unit 8 in this embodiment is superior in terms of the prevention of the waste toner leakage . therefore , even if the protrusive portion 45 a r of the end seal 45 r is reduced in its length l , the waste toner remains satisfactorily sealed in the cleaning unit 8 . that is , according to the first embodiment of the present invention , it is possible to reduce the end seal 45 r in size , reducing thereby the cost . further , there is virtually no difference between the cost of thermoplastic elastomer as the material for the end seal 45 r and the cost of foamed version of synthetic resin , which has been widely used as the material for the elastic component 46 r . therefore , the elastic component 46 r in the first embodiment is no higher in cost than any of the conventional elastic components , making it possible to reduce the cleaning unit 8 in cost . incidentally , the structural arrangement for keeping the cleaning unit 8 sealed at the lengthwise end on the drive side , to prevent the waste toner leakage , is the same as the structural arrangement for keeping the cleaning unit 8 sealed at the lengthwise end on the non - drive side to prevent the waste toner leakage . therefore , it is not described . as described above , in the first embodiment , the elastic component which is to be placed , in the compressed state , between the cleaning blade and cleaning unit frame of the cleaning unit , for removing the transfer residual toner remaining on the photosensitive drum , is formed of thermoplastic elastomer , by injection molding . thus , the elastic component is capable of remaining airtightly in contact with the end seal , by its end seal bearing deformable section . further , as it is compressed by the photosensitive drum , the seal bearing section deforms in such a manner that it moves the end seal closer to the cleaning edge of the cleaning blade , improving thereby the cleaning unit in terms of the prevention of the waste toner leakage . the cleaning unit in the first embodiment is for removing the transfer residual toner remaining on the photosensitive drum . however , the present invention is also applicable to a cleaning unit for removing the transfer residual toner remaining on the intermediary transfer belt 12 ( fig2 ) of the image forming apparatus . next , referring to fig9 - 11 , the cleaning unit 108 in the second embodiment is described . fig9 is a drawing which shows how the cleaning unit 108 is structured to keep the cleaning unit sealed at its lengthwise ends . more specifically , fig9 ( a ) is a plan view of the cleaning unit 108 as seen from the direction perpendicular to the supporting surface of the cleaning unit frame . fig9 ( b ) is a sectional view of the cleaning unit 108 , at the plane w 2 - w 2 in fig9 ( a ). fig1 is a perspective view of the elastic component and its adjacencies in the second embodiment . fig1 is a sectional view of the cleaning unit 108 , at the plane v 2 - v 2 in fig9 ( a ). more specifically , fig1 ( a ) shows the state of the combination of the cleaning unit frame 26 , elastic component 146 r , and end seal 145 r , before the attachment of the cleaning blade 7 . fig1 ( b ) shows the state of the combination of the cleaning unit frame 26 , elastic component 146 r , and end seal 145 r after the attachment of the cleaning blade 7 . fig1 ( c ) shows the state of the combination of the cleaning unit frame 26 , elastic component 146 r , end seal 145 r , and photosensitive drum 4 , after the attachment of the photosensitive drum 4 . the components , their portions , etc ., of the cleaning unit 108 in this embodiment , which are the same in structure and / or function as the counterparts in the first embodiment are not described here . first , referring to fig9 ( a ) and 10 , an elastic component 146 r as the first sealing component is formed in the cleaning unit frame 126 by injection molding . the elastic component 146 r has a vertical sealing section 146 d r for sealing the gap between the cleaning blade 7 and cleaning unit frame 126 , and end seal bearing section 146 b r having the end seal adhesion surface to which the end seal 145 r , as the second sealing component , is to be pasted . next , referring to fig9 ( b ) and 10 , the end seal bearing section 146 b r of the elastic component 146 r , which is the front section of the elastic component 146 r in terms of the direction y has the top surface 146 b 1 r , contacting surface 146 b 2 r , and proximity surface 146 b 3 r . the top surface 146 b 1 r is airtightly in contact with the elastic component contacting front area 126 b r of the cleaning unit frame 126 . the contacting surface 146 b 2 r is in contact with the adhesion surface 145 b r of the end seal 145 r . the proximity surface 146 b 3 r is the rear surface of the elastic component 146 r in terms of the direction y , and is in connection to the vertical sealing section 146 d r . the end seal bearing section 146 b r is roughly in the form of a trapezoid , being shaped so that its contacting surface 146 b 2 r is slanted relative to the direction y , making the seal bearing section 146 b r thickest at h 2 at its inward end , and thinnest at h 1 at its outward end , in terms of the direction z . the elastic component 146 r is formed by injection molding in such a shape that its rear surface 146 c r , in terms of the direction y , airtightly contacts the elastic component contacting rear area of the cleaning unit frame 126 . the elastic component 146 r is formed by injection molding so that the top surface 146 d 1 r of the vertical sealing section 146 d r will be above the cleaning blade supporting surface 126 c of the cleaning unit frame 126 by a distance j in terms of the direction z . next , referring to fig1 , the shape of the elastic component 146 r , which is on the outward side of the cleaning blade 7 in terms of the lengthwise direction , is described . the elastic component 146 r has an end seal bearing outward section 146 h r as the second deformable section of the elastic component 146 r , which keeps sealed the lengthwise outward side of the cleaning blade 7 . in terms of the lengthwise direction , the thickness h 3 of the end seal bearing outward section 146 h r , at its inward surface 146 h 1 r in terms of the direction x , is greater than the thickness h 4 of the end seal bearing outward section 146 h r , at its outward surface 146 h 3 r in terms of the direction x . thus , the elastic component contacting outward surface 126 e r of the cleaning unit frame 126 is slanted . next , referring to the sectional views of the cleaning unit 108 at a plane parallel to the widthwise direction of the unit , how the gap located between the cleaning blade 7 and end seal 145 r of the cleaning unit 108 in terms of the lengthwise direction is kept sealed to prevent the waste toner from leaking is descried following the sequential steps through which the cleaning unit 108 is assembled . more concretely , referring to fig9 , 11 ( a ), 11 ( b ) and 11 ( c ), the structural arrangement of the cleaning unit 108 , which is for keeping sealed , the gap located between the cleaning blade 7 and end seal 145 r , at the lengthwise non - driven end of the cleaning unit 108 , to prevent the waste toner leakage , is described . first , the vertical sealing section 146 d r of the elastic component 146 r is formed in the cleaning unit frame 126 by injection molding . the vertical sealing section 146 d r is shaped so that its thickness h 3 at its upstream surface 146 h 1 r in terms of the x direction is greater than its thickness h 4 at its downstream surface 146 h 3 r . that is , referring to fig1 ( b ), the vertical sealing section 146 d r is shaped so that it is thinnest at the downstream surface 146 he r , being h 4 , and gradually increases , being h 3 at the upstream surface 146 h 1 r . that is , the closer to the downstream end surface 7 f r of the cleaning blade 7 , the thicker it is . in the second embodiment , the end seal 145 r is pasted to the end seal bearing section 146 b r and the end seal bearing outward section 146 h r . then , the cleaning blade 7 is attached to the cleaning unit frame 126 . fig1 ( b ) is a sectional view of the combination of the cleaning unit frame 126 , cleaning blade 7 , end seal 145 r , and elastic component 146 r , after the attachment of the cleaning blade 7 to the cleaning unit frame 126 . there is a gap d 1 between the downstream end surface 7 f r of the cleaning blade 7 in terms of the direction x , and inward lateral surface 145 c r of the end seal 145 r . the presence of the gap d 1 can prevent the problem that when the cleaning blade 7 is attached to the cleaning unit frame 126 , the downstream end portion of the cleaning blade 7 in terms of the direction x runs onto the surface layer 145 e r of the end seal 145 r . further , the vertical sealing section 146 d r airtightly conforms to the bottom surface 7 g and support section 7 b of the cleaning blade 7 . the lateral surface 146 g r , in terms of the direction + x , of the vertical sealing section 146 d r , is slanted . therefore , the force applied to the cleaning blade 7 to attach the cleaning blade 7 to the cleaning unit frame 108 presses on the lateral surface 146 g r . thus , the vertical sealing section 146 d r remains airtightly in contact with the cleaning blade 7 while being made to lean in the direction n 2 in fig1 ( b ). next , shown in fig1 ( c ) is the state of the cleaning unit 108 after the attachment of the photosensitive drum 4 . the two - dot chain line indicates the state ( contours ) of the elastic component 146 r and end seal 1145 r before the attachment of the photosensitive drum 4 . as the photosensitive drum 4 is attached , the force applied to the photosensitive drum 4 in the direction k presses on the end seal bearing outward section 146 h r of the elastic component 146 r , through the end seal 145 r . the outward lateral surface 146 g r , in terms of the direction + x , of the end seal bearing outward section 146 d r , which faces the surface 146 h 1 r of the seal bearing outward section 146 h r in terms of the direction − x , is slanted in the direction − x . therefore , there is a space between the surface 146 g r and surface 146 h 1 r , into which the elastic component 146 r is allowed to expand . thus , as pressure is applied to the photosensitive drum 4 to attach the photosensitive drum 4 to the cleaning unit frame 126 , the seal bearing outward section 146 h r is deformed by the pressure in such a manner that it is deformed more on its downstream side ( direction − x side ), where is thicker , than on its upstream side , which it is thinner . consequently , the seal bearing outward section 146 h r of the elastic component 146 r deforms in the direction indicated by the arrow mark n in fig1 ( b ). therefore , the inward lateral surface 145 c r of the end seal 145 r is moved in the direction indicated by the arrow mark n 2 , reducing thereby the gap between the inward lateral surface 145 c r of the end seal 145 r and the outward lateral surface 7 f r of the cleaning blade 7 , from d 1 to d 2 . in other words , the cleaning unit 108 is improved in terms of the prevention of the waste toner leakage through the gap between the cleaning blade 7 and the inward lateral surface 145 c r of the end seal 145 r . further , the attachment of the photosensitive drum 4 causes the cleaning blade 7 to deform , increasing thereby the amount of pressure applied to the vertical sealing section 146 d r , which in turn increases the amount by which the vertical sealing section 146 r is made to lean in the direction n 2 , increasing thereby the amount of the reaction force generated in the vertical sealing section 146 r . therefore , the cleaning unit 108 can be improved in terms of the prevention of the waste toner leakage , without requiring the contact pressure between cleaning blade 7 and photosensitive drum 4 to be increased . as described above , simply pasting the end seal 145 r closer to the lengthwise end of the cleaning blade 7 makes it more likely for the cleaning blade 7 to run onto the surface layer 145 e r of the end seal 145 r during the attachment of the cleaning blade 7 . it is possible that as the cleaning blade 7 runs onto the surface layer 145 e r , a gap will be created between the photosensitive drum and end seal 145 r , and this gap will allow the waste toner to leak . in the second embodiment , however , the attachment of the photosensitive drum 4 reduces the gap between the cleaning blade 7 and end seal 145 r from d 1 to d 2 . thus , the cleaning unit 108 is better sealed in terms of the prevention of the waste toner leakage , without being reduced in its assembly efficiency . in the second embodiment , the top surface 145 b 1 r of the elastic component 146 r , to which the end seal 145 r is adhered , is formed of thermoplastic elastomer as in the first embodiment . therefore , the gap t between the cleaning blade 7 and end seal 145 r in terms of the widthwise direction can be reduced by the attachment of the cleaning blade and photosensitive drum 4 to the cleaning unit frame 126 . with the reduction in the gap t , the cleaning unit 108 is better sealed in terms of the prevention of the waste toner leakage . to describe the additional effects of the second embodiment of the present invention , the end seal bearing outward section 146 h r of the elastic component 146 r is formed of thermoplastic elastomer , in such a shape and size that in terms of the lengthwise direction , the end seal bearing outward portion of the elastic component 146 r , which is adjacent to the end surface 7 f r of the cleaning blade 7 in terms of the direction + x , is thicker than the outward end portion of the end seal bearing outward section 146 h r . with the provision of the end seal bearing outward section 146 h r , the gap between the end surface 7 f r of the cleaning blade 7 and the end seal 145 r in terms of the lengthwise direction is reduced from d 1 , improving thereby the cleaning unit 108 in terms of the prevention of the waste toner leakage at the lengthwise ends , by the attachment of the photosensitive drum 4 . further , even if the end seal 145 r is reduced in the length l of its protrusive section 145 a r , the cleaning unit 108 remains just as well sealed as , or better sealed than , a conventional cleaning unit , in terms of the waste toner leakage . in other words , the present invention can reduce the end seal 145 r in size , which in turn reduces the cleaning unit 108 in cost . the cost of the thermoplastic elastomer as the material for the elastic component 146 r is virtually no different from that of the foamed synthetic resin which has been widely used as the material for the conventional elastic component 146 r . therefore , the elastic component 146 r in accordance with the present invention is no higher in cost than a conventional elastic component , and therefore , the cleaning unit 108 in accordance with the present invention is no higher in cost than a conventional cleaning unit . incidentally , the structural arrangement for preventing the waste toner from leaking at the drive side end of the cleaning unit 108 in terms of the lengthwise direction is the same as the above described one for the non - drive end of the cleaning unit 108 . therefore , it is not described . next , referring to fig1 and 14 , the structural arrangement , in the third embodiment , for preventing the waste toner from leaking from the cleaning unit 208 , at the lengthwise ends of the cleaning blade 7 , is described in detail , following the sequential steps through which the cleaning unit 208 is assembled . fig1 is a drawing for showing the structural arrangement , in the third embodiment , for preventing the waste toner from leaking from the cleaning unit 208 , at the lengthwise ends of the cleaning blade 7 . fig1 ( a ) is a plan view of the lengthwise end of the cleaning unit 208 , as seen from the direction perpendicular to the supporting surface of the cleaning unit frame . it shows the state of the cleaning unit 208 right after the attachment of the cleaning blade 7 . fig1 ( b ) is a sectional view of the right end portion of the cleaning unit 208 , as seen from within the cleaning unit 208 . it also shows the state of the cleaning unit 208 immediately after the attachment of the cleaning blade 7 . fig1 is a drawing for showing the structural arrangement for keeping the cleaning unit 208 sealed at the lengthwise ends of the cleaning blade 7 . more specifically , fig1 ( a ) is a plan view of the right end portion of the cleaning unit frame as seen from the direction perpendicular to the supporting surface of the cleaning unit frame . it shows the state of the lengthwise end portion of the cleaning unit 208 before the attachment of the cleaning blade 7 . fig1 ( b ) is a sectional view of the right end portion of the cleaning unit 208 , as seen from within the cleaning unit 208 . it shows the state of the lengthwise end portion of the cleaning unit 208 before the attachment of the cleaning blade 7 . in fig1 ( b ), the photosensitive drum 4 is indicated by an imaginary line ( singe - dot chain line ). further , the lengthwise and widthwise directions of the cleaning unit will be referred to as directions x and y , respectively . the direction perpendicular to the directions x and y will be referred to as the direction z ( directions which arrow marks point will be referred to as positive (+) directions ). first , the vertical seal 246 r is formed by molding , in cleaning unit frame 226 . referring to fig1 ( a ), the vertical seal 246 r is in the form of a rib , which extends in the direction y . next , referring to fig1 ( b ), the front end surface 246 b r of the vertical seal 246 r in terms of the direction y has a contacting surface 246 b 1 r which contacts the end seal 245 r , and a frame contacting section 246 b 2 r which airtightly contacts the front airtight contact section 226 d r of the cleaning unit frame 226 . referring to fig1 ( b ), the contacting surface 246 b 1 r is formed so that it is roughly level with the end surface 7 e of the cleaning blade 7 in terms of the direction y . referring to fig1 ( b ), the rear end surface 246 c r of the vertical seal 246 r in terms of the direction y is formed so that it airtightly contacts the rear airtight contact section 226 e r of the cleaning unit frame 226 . also referring to fig1 ( b ), the vertical seal 246 r is formed so that prior to the attachment of the cleaning blade 7 , the top surface 246 d r of the vertical seal 246 r will be above the supporting surface 226 b of the cleaning unit frame 226 by an amount j , in terms of the direction z . referring to fig1 ( b ), the end seal 245 r is positioned so that the vertical seal contacting surface 245 b r ( fig8 ) of the end seal 245 r contacts the end seal contacting surface 246 b 1 r of the vertical seal 246 r . further , the cleaning blade 7 is attached to the supporting surface 226 b of the cleaning unit frame 226 . the end seal 245 r and cleaning blade 7 may be reversed in the order in which they are attached to the cleaning unit frame 226 . lastly , the photosensitive drum 4 is attached to the cleaning unit frame 226 . as the photosensitive drum 4 is attached , the vertical seal contacting surface 245 b r of the end seal 245 r comes into contact with the end surface 7 e of the cleaning blade 7 , and the surface layer 245 e r of the end seal 245 r comes into contact with the photosensitive drum 4 . thus , the end seal 245 r seals the gap between the vertical seal 246 r and cleaning blade 7 , and the gap between the photosensitive drum 4 and cleaning unit frame 226 , at the lengthwise ends of the cleaning unit 208 , preventing thereby the waste toner leakage . further , referring to fig1 ( a ), the end seal 245 r has a protrusive portion 245 a r , which is on the outward side of the end surface 7 f of the cleaning blade 7 in terms of the lengthwise direction , and protrudes from the main section of the end seal 245 r by a length of l in the direction y . the cleaning blade 7 is positioned so that its lengthwise end surface 7 f r will be in contact with , or in the adjacencies of , the inward surface 245 c r of the protrusive portion 245 a r of the end seal 245 . at this time , how the waste toner is prevented from leaking through the gap between the cleaning blade 7 and vertical seal 246 r is described . referring to fig1 ( b ), the vertical seal 246 r is formed so that its top surface 246 d r is larger by the amount j than the supporting surface 226 b . therefore , as it comes into contact with the bottom surface 7 g of the cleaning blade 7 , it is squashed by the cleaning blade 7 . since the vertical seal 246 r is elastic , it is made by the compression load to deform in such a manner that it conforms in shape to the bottom surface 7 g of the cleaning blade 7 . therefore , no gap is created between itself and the cleaning blade 7 . further , the vertical seal 246 r is formed of thermoplastic elastomer , being therefore sticky . therefore , it sticks to the cleaning blade 7 . therefore , it is ensured that the area of contact between the vertical seal 246 r and cleaning blade 7 remains airtightly sealed . for the reasons given above , it is most unlikely that the waste toner will leak through the area of contact between the cleaning blade 7 and vertical seal 246 r . next , referring to fig1 , how the gap surrounded by the cleaning blade 7 , end seal 245 r and vertical seal 246 r is sealed in the third embodiment is described . fig1 is a drawing for describing how the cleaning unit frame 226 is kept sealed to prevent the waste toner from leaking at the lengthwise ends . more specifically , fig1 ( a ) is a drawing which shows the gap created by the cleaning blade 7 , end seal 245 r , and vertical seal 246 r . fig1 ( b ) is an enlarged view of the area dt 1 encircled by a dotted line in fig1 ( a ). here , how the area of contact between the end seal 245 r and vertical seal 246 r is sealed by the vertical seal 246 , assuming that the material for the vertical seal 246 r is thermoplastic elastomer . in the third embodiment , the vertical seal 246 r is positioned in the adjacencies of the end seal 245 r so that the distance between the vertical seal 246 r and end seal 245 r is less after the former was compressed than before it is compressed . more concretely , referring to fig1 ( b ), as the vertical seal 246 r is squashed by the cleaning blade 7 , it deforms in such a shape that its end seal contacting surface 246 b 1 r extends by an amount δn 1 in the direction y . therefore , the gap 247 is reduced by the amount δn 1 . that is , the cleaning unit 208 is better sealed . on the other hand , in a case where the vertical seal 246 is formed of foamed synthetic resin as the vertical seal of a conventional cleaning unit , the amount δn 1 by which the vertical seal is compressed is virtually zero . further , because the vertical seal is formed of foamed synthetic resin , even if it is squashed by the cleaning blade 7 , all that happens is that the cells of the foamed synthetic resin are reduced in size . thus , the vertical seal hardly extends in the direction y . therefore , even if the end seal and vertical seal happen to come into contact with each other , the contact is unlikely to be airtight . beside , if gaps happen between them , they are difficult to seal . that is , in the case where the material for the vertical seal is foamed synthetic resin , it is difficult to make the vertical seal come into contact with the end seal . in the third embodiment , the vertical seal 246 r is formed of thermoplastic elastomer , and is positioned so that it is pressed upon the end seal 245 r . thus , it is unlikely for gaps to be created by the vertical seal 246 r , end seal 245 r and cleaning blade 7 . therefore , the cleaning unit is improved in terms of the prevention of the waste toner leakage . therefore , even if the protrusive portion 245 a r of the end seal 245 r is reduced in its length l , the cleaning unit is kept in the state in which the waste toner does not leak . in other words , it is allowed to reduce the end seal 245 r in size . therefore , it is possible to reduce the cleaning unit in cost . further , the cost of the thermoplastic elastomer as the material for the elastic component 246 r is virtually no different from that of the foamed synthetic resin which has been widely used as the material for the conventional end seal 246 r . therefore , the elastic component 246 r in accordance with the present invention is no higher in cost than a conventional elastic component , and therefore , the cleaning unit 208 in accordance with the present invention is no higher in cost than a conventional elastic cleaning unit . incidentally , the structural arrangement for preventing the waste toner from leaking at the drive side end of the cleaning unit 208 in terms of the lengthwise direction is the same as the above described one for the non - drive end of the cleaning unit 208 . therefore , it is not described . as described above , in the third embodiment , as the cleaning blade 7 and photosensitive drum 4 are attached , the vertical seal 246 r is compressed , being thereby deformed in such a manner that it partially extends to the adjacencies of the end seal 245 r . therefore , it is possible to prevent the problem that gaps are created between the vertical seal 246 and end seal 245 . therefore , it is possible to improve the cleaning unit in terms of the prevention of the waste toner leakage . further in the case of the structural arrangement for the cleaning unit 208 in the third embodiment , it does not occur that the end seal 245 runs onto the vertical seal 246 . therefore , it does not occur that the end seal 245 is made to warp by the vertical seal 246 . therefore , it is possible to prevent gaps from occurring between the end seal 245 and cleaning blade 7 . therefore , it is possible to improve the cleaning unit in terms of the prevention of the waste toner leakage . next , referring to fig1 - 18 , the fourth embodiment of the present invention is described . fig1 is a drawing for showing the structural arrangement , in the fourth embodiment , for keeping the lengthwise ends of the cleaning unit sealed in terms of the waste toner leakage . more specifically , fig1 ( a ) is a plan view of the lengthwise right end portion of the cleaning unit in the fourth embodiment , as seen from the direction perpendicular to the supporting surface of the cleaning unit frame . it shows the state of the lengthwise end after the attachment of the cleaning blade . fig1 ( b ) is a sectional view of the lengthwise right end portion of the cleaning unit , as seen from within the cleaning unit after the attachment of the cleaning blade . fig1 is a drawing for showing the structural arrangement , in the fourth embodiment , for keeping the lengthwise ends of the cleaning unit sealed . fig1 ( a ) is a plan view of the lengthwise right end portion of the cleaning unit , as seen from the direction perpendicular to the supporting surface of the cleaning unit frame before the attachment of the cleaning blade . fig1 ( b ) is a sectional view of the lengthwise right end portion of the cleaning unit as seen from within the cleaning unit frame before the attachment of the cleaning blade . fig1 is a drawing of a modified version of the cleaning unit in the fourth embodiment . fig1 ( a ) is a plan view of the lengthwise right end portion of the cleaning unit , as seen from the direction perpendicular to the supporting surface of the cleaning unit frame before the attachment of the cleaning blade . fig1 ( b ) is a sectional view of the lengthwise right end portion of the cleaning unit as seen from within the cleaning unit frame before the attachment of the cleaning blade . fig1 is a drawing for showing the structural arrangement in the fourth embodiment , for keeping the lengthwise ends of the cleaning unit sealed in terms of the waste toner leakage . in fig1 - 18 , the lengthwise and widthwise directions of the cleaning unit are referred to as the directions x and y , respectively . the direction which is perpendicular to both the directions x and y is referred to as the direction z ( directions indicated by arrow marks in drawings are referred to as positive directions ). the components , their portions , and their functions , in the fourth embodiment , which are the same as or similar to the counterparts in the third embodiment are not described . fig1 - 17 , the structural arrangement , in this embodiment , for keeping sealed the cleaning unit , at the lengthwise ends of the cleaning blade 7 , in terms of the waste toner leakage , is described , following the sequential steps through which the cleaning unit is assembled . first the vertical seal 346 r is formed by molding in cleaning unit frame 326 . referring to fig1 ( a ), the vertical seal 346 r is in the form of a rib , which extends in the direction y . next , referring to fig1 ( b ), the front end 346 e r of the vertical seal 346 r in terms of the direction y is provided with a protrusive portion 346 a r , which runs onto the end seal adhesion surface 326 c r of the cleaning unit frame 326 , to which the end seal 345 r is pasted . this protrusive portion 346 a r of the vertical seal 346 r is positioned so that it will be pinched between the cleaning unit frame 326 and end seal 345 r . in the fourth embodiment , the vertical seal 346 r is positioned in the adjacencies of the end seal 345 r in such a manner that the distance between the vertical seal 346 r and end seal 445 r will be less seal after the compression of the vertical seal 246 r than before the compression . also as in the third embodiment , the vertical seal 346 r is provided with a cleaning unit frame contacting surface 346 b 2 r , which airtightly contacts the vertical seal contacting front surface 326 d r of the cleaning unit frame 326 . further , the vertical seal 346 r is formed so that its rear end surface 346 c r in terms of the direction y airtightly contacts the vertical seal contacting rear surface of the cleaning unit frame 326 . referring to fig1 ( b ), the protrusive portion 346 a r is provided with a section 346 d 2 r ( fig1 ) shaped so that its top surface 346 d r is slanted in the direction − z from the ridge line 346 d 1 r toward the edge 346 e r . also as in the third embodiment , the vertical seal 346 r is formed so that before the attachment of the cleaning blade 7 , the top surface 346 d r extends beyond the supporting surface 326 b of the cleaning unit frame 326 in the direction z by a distance j . also referring to fig1 , it is assumed here that in terms of the direction y , the distance between the position y 7 e of the end surface 7 e of the cleaning blade 7 and the edge 346 e r of the protrusive portion 346 a r is referred to as the intrusion distance k . the shape of the vertical seal 346 r in this embodiment is in the form of a rib having the protrusive portion 346 a r having a slanted surface . however , the shape of the vertical seal 346 r may be different from the one in this embodiment . for example , the vertical seal 346 r may be shaped so that the first width ( in terms of direction x ) w 1 , or the width of the protrusive portion 346 a r of the rib , is greater than the second width ( in terms of direction x ) w 2 , or the width of the other portion of the vertical seal 346 r than the protrusive portion 346 r ( w 1 & gt ; w 2 ). that is , the vertical seal 346 r may be in any shape as long as it is shaped so that it is provided with the protrusive portion 346 a r which runs onto the end seal adhesion surface 326 c r of the cleaning unit frame 326 . referring to fig1 ( b ), in terms of the direction y , the end seal 345 r is positioned so that as the cleaning blade 7 is attached , the cleaning blade contacting surface 345 b r of the end seal 345 r comes into contact with the end surface 7 e of the cleaning blade 7 . further , the end seal 345 r runs onto the protrusive portion 346 a r of the vertical seal 346 r by the intrusion distance k , measured from its cleaning blade contacting surface 345 b r . the portion of the end seal 345 r , which runs onto the protrusive portion 346 a r of the vertical seal 346 r , is referred to as an overlap portion 345 e r . that is , the area of contact between the end seal 245 r and vertical seal 346 r is sealed by the placement of the overlap portion 345 e r of the end seal 345 r in contact with the protrusive portion 346 a r of the vertical seal 345 r . this arrangement is described later . next , the cleaning blade 7 is attached to the supporting surface 326 b of the cleaning unit frame 326 . lastly , the photosensitive drum 4 is attached . as the photosensitive drum 4 is attached , the cleaning blade contacting surface 345 b r of the end seal 345 r comes into contact with the end surface 7 e of the cleaning blade 7 , and the surface layer 345 e r of the end seal 345 r comes into contact with the photosensitive drum 4 . further , the end seal 345 r seals the gap between the cleaning blade 7 and cleaning unit frame 326 , and also , the gap between the photosensitive drum 4 and cleaning unit frame 326 , at the lengthwise ends of the cleaning unit frame 326 , preventing thereby the waste toner leakage . also as in the third embodiment , the end seal 345 r is provided with the protrusive portion 345 a r which is on the outward side of the lengthwise end surface 7 f r of the cleaning blade 7 , and protrudes in the direction y by the length l , as shown in fig1 ( a ). the cleaning blade 7 is positioned so that its lengthwise end surface 7 f r will contact , or be in the adjacencies of , the inward surface 345 c r of the protrusive portion 345 a r of the end seal 345 r . incidentally , the order in which the end seal 345 r and cleaning blade 7 are attached may be opposite from the one in this embodiment . at this time , how the waste toner is prevented from leaking from the area of contact between the cleaning blade 7 and vertical seal 346 r in the fourth embodiment is described . referring to fig1 ( b ), the vertical seal 346 r is formed so that its top surface 346 d r is greater by the amount j than the supporting surface 326 b . thus , as it comes into contact with the bottom surface 7 g of the cleaning blade 7 , it is squashed by the cleaning blade 7 . since the vertical seal 346 r is elastic , it is deformed by the compression load in such a manner that it partially extends along the bottom surface 7 g of the cleaning blade 7 while conforming in shape to the bottom surface 7 g . therefore , it is unlikely for gaps to be created between the vertical seal 346 r and cleaning blade 7 . further , the vertical seal 346 r is formed of thermoplastic elastomer , being therefore sticky . thus , it sticks to the cleaning blade 7 , ensuring that the area of contact between the vertical seal 346 r and cleaning blade 7 remains airtightly sealed . therefore , the cleaning unit 308 remains sealed as airtightly as possible in terms of the prevention of the waste toner leakage between the cleaning blade 7 and vertical seal 346 r . next , the gap which occurs between the cleaning blade 7 and end seal 345 r is described . in the fourth embodiment , the end seal 345 r is positioned so that it runs onto the protrusive portion 346 a of the vertical seal 346 r . therefore , the end seal 345 r sometimes warps . however , the protrusive portion 346 a r is wedgie , and therefore , the height by which the end seal 345 r runs onto the protrusive portion 346 a r is not much . therefore , even if the end seal 345 r warps , the amount by which the end seal 345 r warps is very small . therefore , it is unlikely for gaps to occur between the end surface 7 e of the cleaning blade 7 and the cleaning blade contacting surface 345 b r of the end seal 345 r . therefore , even if the protrusive portion 345 a r of the end seal 345 r is reduced in its length l , it is ensured that the waste toner remains satisfactorily sealed in the cleaning unit 308 . in other words , it is allowed to reduce the end seal 345 r in size . therefore , it is possible to reduce the cleaning unit in cost . the vertical seal 346 r is formed by injection molding . therefore , its protrusive portion 346 a r , which is roughly in the shape of a wedge , can be easily formed . in comparison , in the case of a conventional vertical seal 346 r , its material is foamed resin . therefore , from the standpoint of processing foamed resin , it is rather difficult to form a vertical seal ( 346 r ), the protrusive portion ( 346 a r ) of which is in the form of a wedge . that is , it is difficult to form a vertical seal 346 a r which does not cause the end seal 345 r to significantly warp . further , the cost of thermoplastic elastomer as the material for the vertical seal 346 r is barely different from that of the foamed synthetic resin which has been conventionally used as the material for the vertical seal 346 r . therefore , the usage of the thermoplastic resin does not increase the vertical seal 346 r in cost . thus , it is possible to reduce the cleaning unit 308 in cost . next , referring to fig1 , the additional effects of the fourth embodiment are described . in the fourth embodiment , the cleaning unit frame 326 is structured so that the distance between the end seal adhesion surface 326 c r of the cleaning unit frame 326 and the peripheral surface of the photosensitive drum 4 becomes a preset distance m as shown in fig1 . further , the end seal 345 r is made thicker than the preset distance m . thus , pasting the end seal 345 r to the end seal adhesion surface 326 c r prevents the waste toner from leaking through the gap between the photosensitive drum 4 and cleaning unit frame 326 . further , the protrusive portion 346 a r of the vertical seal 346 r runs onto the end seal adhesion surface 326 c r , and enters between the end seal adhesion surface 326 c r and end seal 345 r . therefor , the height of the portion of the end seal adhesion surface 326 c r , which corresponds in position to the overlap portion 345 e r of the end seal 345 r , increases by the height δm of the wedgie portion 346 d 2 r . that is , the distance m between the end seal adhesion surface 326 c r and the peripheral surface of the photosensitive drum 4 is reduced . therefore , the amount by which the end seal 345 r is squashed across its overlap portion 345 e r is increased . the end seal 345 r is elastic . therefore , the greater the amount by which the end seal 345 r is squashed , the greater the contact pressure between the end seal 345 r and photosensitive drum 4 . further , the protrusive portion 346 a r of the vertical seal 346 r is deformed by being compressed , in such a manner that the distance between the vertical seal 346 r , and the end seal 345 r which is positioned adjacent to the vertical seal 346 r , is reduced . further , the protrusive portion 346 a r swells in the direction to cause the end seal 345 to press on the photosensitive drum 4 , increasing thereby the contact pressure between the end seal 345 r and photosensitive drum 4 . thus , the area of contact between the end seal 345 r and photosensitive drum 7 is better sealed from the standpoint of prevention of the waste toner leakage . next , referring to fig2 , another effect of the structural arrangement for the cleaning unit in the fourth embodiment is described in comparison to that in the third embodiment . fig2 is a drawing which shows the structural arrangement , in the fourth embodiment , for keeping the cleaning unit sealed at its lengthwise ends . more specifically , fig2 ( a ) is a drawing which shows the gap which occurs between the cleaning blade and end seal , and fig2 ( b ) is an enlarged view of the inward side of the area dt 2 encircled by a dotted line in fig2 ( a ). referring to fig1 ( a ), in the third embodiment , the vertical seal 246 r is positioned so that end surface 7 e of the cleaning blade 7 becomes roughly level with the cleaning unit frame contacting surface 246 b 2 r of the vertical seal 246 r in terms of the direction y . however , because of the tolerance in component dimension , the end surface 7 e of the cleaning blade 7 protrudes beyond the end seal contacting surface 246 b 1 r of the vertical seal 246 r in the direction y by a distance δn , as shown in fig1 ( a ) and 19 ( b ). therefore , the contacting surface 245 b r of the end seal 245 r comes into contact with the end surface 7 e of the cleaning blade 7 before it comes into contact with the end seal contacting surface 246 b 1 r of the vertical seal 246 r . therefore , a gap 247 , the width of which in terms of the direction z is δn , is created by the cleaning unit frame 226 , cleaning blade 7 , end seal 245 r , and vertical seal 246 r . however , the vertical seal 246 r is formed of an elastic substance . therefore , as it is squashed by the cleaning blade 7 , its deformable portion 246 f r extends in the direction y by a distance δn 1 , as indicated by the dotted lines in fig1 ( b ). similarly , as the end seal 245 r is squashed by the photosensitive drum 4 , its deformable portion 245 f r extends in the direction − y by a distance δn 2 . that is , the vertical seal 246 r and end seal 245 r seal the gap 247 with their deformable portions 246 f r and 245 f r , respectively . (( δn 1 + δn 2 )≧ δn ). however , there are limits to the distances δn 1 and δn 2 by which the vertical seal 246 r and 245 r deform ( extend ), respectively . therefore , the tolerance in component dimension , and the tolerance in assembly have to be strictly controlled . therefore , the third embodiment possibly increases the cleaning unit in cost . in comparison , in the case of the fourth embodiment , the vertical seal 346 r is provided with the protrusive portion 346 a r , which is roughly in the form of a wedge and protrudes in the direction y beyond the end surface 7 e of the cleaning blade 7 as shown in fig2 ( a ). fig2 ( a ) and 20 ( b ) show the state of the cleaning unit 308 after the attachment of the vertical seal 346 r , cleaning blade 7 , and end seal 345 r to the cleaning unit frame 326 . when the cleaning unit frame 308 is in the state shown in fig2 ( a ) and 20 ( b ), the end surface 7 e of the cleaning blade 7 is at a point which is away in the direction y from the starting point ridge 346 d 1 r by a distance q . referring to fig2 ( b ), before the attachment of the photosensitive drum 4 , it is possible that the gap 348 , which is δq in dimension in terms of the direction y will be created by the cleaning blade 7 , vertical seal 346 r , and end seal 345 r . however , the vertical seal 346 r is provided with the protrusive portion 346 a r , which is wedgie in cross section , and the starting point ridge 346 d 1 r is in the position in which it airtightly contacts the bottom surface 7 g of the cleaning blade 7 . further , the distance δq between the slanted surface 346 d 2 r and the bottom surface of the cleaning blade 7 in terms of the direction z is minute . here , the cleaning blade 7 , which is in contact with the photosensitive drum 4 ( fig1 ( b )), deforms in the direction − z by an amount δr as indicated by the dotted lines in fig2 ( b ). since the distance δq is sufficiently smaller than the amount δr of the deformation of the cleaning blade 7 , the cleaning blade 7 can seal the minute gap 348 by being deformed . in the fourth embodiment , therefore , the attachment of the photosensitive drum 4 prevents the occurrence of the above - described gap 348 . incidentally , the structural arrangement , in the fourth embodiment , for preventing the waste toner from leaking from the cleaning unit at the lengthwise end of the cleaning blade 7 on the drive side is the same as that at the lengthwise end of the cleaning blade 7 on the non - drive side . therefore , it is not described . as described above , in the fourth embodiment , as the cleaning blade 7 and photosensitive drum 4 are attached , the vertical seal 346 is compressed , deforming thereby in a manner to extend to the adjacencies of the end seal 345 . thus , it is possible to prevent the problem that a gap occurs between the vertical seal 346 and end seal 345 . therefore , it is possible to improve the cleaning unit 308 in terms of the prevention of the waste toner leakage . further , the protrusive portion 346 a of the vertical seal 346 is compressed , being thereby deformed in such a manner that it extends to the adjacencies of the end seal 345 which is positioned next to the vertical seal 346 . consequently , the end seal 345 is made to press on the photosensitive drum 4 , increasing thereby the contact pressure between the end seal 345 and photosensitive drum 4 . therefore , the area of contact between the end seal 345 and photosensitive drum 4 is better sealed . further , the portion of the protrusive portion 346 a , which comes into contact with the end seal 345 is roughly in the form of a wedge having the slanted surface 346 d 2 r . therefore , the amount by which the end seal 345 is made to warp as it runs onto the protrusive portion 346 a can be minimized . thus , it is allowed to reduce the protrusive portion 345 a of the end seal 345 in length . therefore , it is possible to keep the area of contact between the end seal 345 and cleaning blade 7 satisfactorily sealed , without adding to the cost of the end seal 345 . according to the present invention , it is possible to provide a cleaning unit which is low in cost , and high in its ability to keep developer sealed . while the invention has been described with reference to exemplary embodiments , it is to be understood that the invention is not limited to the disclosed exemplary embodiments . the scope of the following claims is to be accorded the broadest interpretations as to encompass all such modifications and equivalent structures and functions . this application claims priority from japanese patent applications nos . 201857 / 2012 and 201898 / 2012 filed sep . 13 , 2012 and sep . 13 , 2012 , respectively , which are hereby incorporated by reference .