Abstract:
A process cartridge is detachably mountable to a main assembly of an electrophotographic image forming apparatus. The process cartridge includes a photosensitive member unit having a photosensitive drum, a developer carrying member for developing an electrostatic latent image formed on the photosensitive drum with a developer, and a toner accommodating unit having a developer accommodating portion accommodating the developer to be used for development of the electrostatic latent image. A movable frame supports the developer carrying member, and an urging member is provided for urging the movable frame in a direction in which the developer carrying member approaches the photosensitive drum. A space maintaining member, is also provided for maintaining a state in which a distance between the photosensitive drum and the developer carrying member is larger than that in an image formation.

Description:
FIELD OF THE INVENTION AND RELATED ART 
     The present invention relates to a process cartridge used for electrophotographic image formation. More specifically, it relates to a gap maintaining member with which a process cartridge is fitted to ensure that a gap is maintained between its photosensitive member and developer bearing member (inclusive of spacer rings) during the distribution of the process cartridge. 
     In the following description of the present invention, the term “process cartridge” means a cartridge in which at least a developing means and an electrophotographic photosensitive member are integrally disposed so that they can be removably mounted in the main assembly of an electrophotographic image forming apparatus. 
     Further, the term “electrophotographic image forming apparatus” means an apparatus which forms an image on recording medium, with the use of an electrophotographic image forming method. Examples of an electrophotographic image forming apparatus are an electrophotographic printer (laser printer, LED printer, etc., for example), a facsimile apparatus, a wordprocessor, etc. 
     As the cumulative usage of a conventional electrophotographic image forming apparatus, that is, an electrophotographic image forming apparatus in accordance with the prior art, exceeds a certain length of time, various maintenance operations have to be performed, for example, the operation for replacing its electrophotographic photosensitive drum, the operation for replenishing the apparatus with developer or replacing the developer, the operation for adjusting, and/or cleaning the other components (charging device, cleaning device, etc.), etc. In the past, the operations, such as the abovementioned ones, for maintaining an electrophotographic image forming apparatus have been very difficult for an average user. As a matter of fact, they have been virtually impossible to perform, unless a person who performs the operations is a service person having professional knowledge of an image forming apparatus. 
     In the field of an electrophotographic image forming apparatus, therefore, a process cartridge system has come to be employed. According to a process cartridge system, an electrophotographic photosensitive member, and means for processing the electrophotographic photosensitive member, are integrally disposed in a cartridge so that they can be removably mounted in the main assembly of an electrophotographic image forming apparatus. Thus, a process cartridge system makes it possible for an average user to maintain an electrophotographic image forming apparatus by himself, that is, without relying on a service person. In other words, it drastically improves an electrophotographic image forming apparatus in operability. Thus, a process cartridge system has come to be widely used in the field of electrophotographic image forming apparatus. 
     There are two types of developing method compatible with an electrophotographic image forming apparatus which employs a process cartridge system, that is, the type which places an electrophotographic photosensitive member in contact with a developer bearing member, and the type which does not place an electrophotographic photosensitive member in contact with a developer bearing member. In the case of the latter, a latent image on an electrophotographic photosensitive member is developed by transferring developer onto the photosensitive drum from the developer bearing member, with roughly a preset amount of gap provided between the photosensitive member and developer bearing member by the gap regulating members placed in contact with the peripheral surface of the photosensitive member. In other words, in the case of an electrophotographic image forming apparatus which employs a process cartridge system, the developer bearing member is kept in contact with the electrophotographic photosensitive member by a pressure applying means, such as a spring, or the gap regulating member is kept in contact with the electrophotographic photosensitive member by the pressure applying means, such as a spring. 
     Thus, even during the distribution of a process cartridge, that is, even during the period between the moment a process cartridge has been completed to the moment the process cartridge is mounted into the main assembly of an image forming apparatus, the developer bearing member or gap regulating member is kept in contact with the electrophotographic photosensitive member by a pressure applying means, such as a spring. Therefore, the following problems sometimes occur during the distribution of a process cartridge. 
     That is, if a process cartridge happens to be subjected to a large amount of impact, the portion of the electrostatic photosensitive member, which is in contact with the developer bearing member or gap regulating member, the portion of the developer bearing member, which is in contact with the photosensitive member, and/or the portion of the gap regulating member, which is in contact with the photosensitive member, is also subjected to a large amount of impact, making it possible for the electrophotographic photosensitive member, developer bearing member, and/or gap regulating member to be damaged. 
     Next, some process cartridges which employ the prior arts for solving the above described problem will be described. 
     In the case of the process cartridge proposed in Japanese Laid-open Patent Application H05-297646, a protective means, which is a piece of film, is placed between the electrophotographic photosensitive member and developer bearing member, which are positioned to maintain a gap of 250 μm between them, as shown in  FIG. 2  of the abovementioned application. 
     In the case of the process cartridge proposed in Japanese Laid-open Patent Application 2003-241621, the electrophotographic photosensitive member is supported by the first frame, whereas the developer bearing member is supported by the second frame, which is connected to the first frame so that it can be rotationally moved relative to the first frame, as shown in  FIG. 10  of the abovementioned application. This process cartridge is characterized in that as soon as it is produced, it is fitted with a gap maintaining member which remains engaged with both the first and second frames to keep a greater distance between the axial line of the photosensitive member and the axial line of the developer bearing member during the distribution of the process cartridge than the distance maintained between the axial line of the photosensitive member and the axial line of the developer bearing member by the gap regulating member during image formation. 
     More specifically, in the case of the process cartridge proposed by Japanese Laid-open Patent Application H05-297646, a protective means, which is roughly 200-300 μm in thickness, is placed between the photosensitive member and developer bearing member, which are kept separated by roughly 200-300 μm by the gap regulating member. This structural arrangement, however, is effective only when the impact to which the process cartridge subjected is subjected is small. That is, it is effective to prevent the problem that the peripheral surface of the photosensitive member is damaged by the friction caused between the peripheral surface of the photosensitive member and developer bearing member by the direct contact between the peripheral surface of the photosensitive member and the peripheral surface of the developer bearing member. In other words, it is not effective to prevent the damages, more specifically, the deformation of the photosensitive member, developer bearing member, and/or gap regulating member, which occur as the process cartridge is subjected to a large amount of impact. 
     In the case of the process cartridge proposed by Japanese Laid-open Patent Application 2003-241621, the second frame, that is, the frame which supports the developer bearing member, has a developer storage. Thus, as the developer storage (developer container) is increased in capacity to prolong a process cartridge in service life, the second frame increases in weight, which in turn increases the amount of the contact pressure generated between the photosensitive member and developer bearing member during the distribution of the process cartridge, and also, the amount of impact to which the portion of the peripheral surface of the photosensitive member, which is in contact with the peripheral surface of the developer bearing member, or the gap regulating member, is subjected during the distribution of the process cartridge. In the case of this process cartridge, therefore, in order to prevent the deformation of the gap regulating member and/or the damage to the photosensitive member, the process cartridge must be increased in the distance between the photosensitive member and developer bearing member, or the distance between the photosensitive member and gap regulating member. The increase in the distance between the photosensitive member and developer bearing member, or the increase in the distance between the photosensitive member and gap regulating member, requires the process cartridge and/or gap maintaining member to be increased in size, and the increasing the process cartridge and/or gap maintaining in size adds to the cost of the process cartridge. 
     SUMMARY OF THE INVENTION 
     Thus, the primary object of the present invention is to provide a combination of a process cartridge, and a gap maintaining member which is no greater in size than a gap maintaining member in accordance with the prior art, which can prevent the problem that an electrophotographic photosensitive member, a developer bearing member, and/or a gap regulating member is damaged during the distribution of the process cartridge. 
     Another object of the present invention is to provide a combination of a process cartridge of a large capacity, and a gap maintaining member which is not greater in size than a gap maintaining member for a process cartridge of a small capacity. 
     Another object of the present invention is to provide a combination of a process cartridge, and a gap maintaining member which can keep the electrophotographic photosensitive member and developer bearing member separated regardless of the capacity of the developer storage portion of the process cartridge. 
     According to an aspect of the present invention, there is provided a process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, said process cartridge comprising a photosensitive member unit having a photosensitive drum; a developer carrying member for developing an electrostatic latent image formed on said photosensitive drum with a developer; a toner accommodating unit having a developer accommodating portion accommodating the developer to be used for development of said electrostatic latent image, said toner accommodating unit being fixed to said photosensitive member unit; a movable frame which is movable relative to said toner accommodating unit and which supports said developer carrying member; an urging member for urging said movable frame in a direction in which said developer carrying member approaches said photosensitive drum; and a space maintaining member, demountably provided between said photosensitive member unit and said movable frame in contact to said photosensitive member unit and said movable frame, for maintaining a state in which a distance between said photosensitive drum and said developer carrying member is larger than that in an image formation. 
     According to another aspect of the present invention, there is provided a space maintaining member detachably mountable to a process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, said process cartridge including a photosensitive member unit having a photosensitive drum; a developer carrying member for developing an electrostatic latent image formed on said photosensitive drum with a developer; a toner accommodating unit having a developer accommodating portion accommodating the developer to be used for development of said electrostatic latent image, said toner accommodating unit being fixed to said photosensitive member unit; a movable frame which is movable relative to said toner accommodating unit and which supports said developer carrying member; an urging member for urging said movable frame in a direction in which said developer carrying member approaches said photosensitive drum: wherein said space maintaining member, when said space maintaining member is mounted to said process cartridge, contacts to said photosensitive member unit and said movable frame to maintain a state in which a distance between said photosensitive drum and said developer carrying member is larger than that in an image formation. 
     These and other objects, features, and advantages of the present invention will become more apparent upon consideration of the following description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic sectional view of a typical electrophotographic image forming apparatus which is compatible with a process cartridge in accordance with the present invention. 
         FIG. 2  is a schematic sectional view of a process cartridge in accordance with the present invention, showing the general structure of the cartridge. 
         FIG. 3  is a perspective view of the developing means container unit of the process cartridge in accordance with the present invention, showing the structure of the container unit. 
         FIG. 4  is a perspective view of one of the lengthwise end portions of the process cartridge in accordance with the present invention, showing the structure of the developing means container unit. 
         FIG. 5  is a perspective view of the combination of the process cartridge and gap maintaining member in the first embodiment of the present invention, showing the frame structure of the process cartridge, and how the gap maintaining member is engaged with the process cartridge. 
         FIG. 6  is a perspective view of one of the lengthwise end portions of the process cartridge, and corresponding portion of the gap maintaining member, in the first embodiment of the present invention, showing how the gap maintaining member is engaged with the process cartridge to maintain a preset amount of gap between the photosensitive member and developer bearing member, and also, between the photosensitive member and gap regulating member, during the distribution of the process cartridge. 
         FIG. 7  is a plan view of one of the lengthwise ends of the process cartridge, and corresponding portion of the gap maintaining member, in the first embodiment of the present invention, showing how the gap maintaining member engages with the process cartridge to maintain a preset amount of gap between the photosensitive member and developer bearing member, and also, between the photosensitive member and gap regulating member, during the distribution of the process cartridge. 
         FIG. 8(   a ) is a plan view of the photosensitive member and developer bearing member, in the first embodiment of the present invention, which are not in their image forming positions because of the presence of the gap maintaining member, and  FIG. 8(   b ) is a plan view of the photosensitive member and developer bearing member, in the first embodiment, which are in the image forming positions because of the absence of the gap maintaining member. 
         FIG. 9  is a schematic sectional view of a typical electrophotographic image forming apparatus which is compatible with a process cartridge in accordance with the present invention, showing what happens if the process cartridge in accordance with the present invention is mounted into the main assembly of the image forming apparatus without removing the gap maintaining member from the process cartridge. 
         FIG. 10  is a perspective view of the gap maintaining member in the second embodiment of the present invention. 
         FIG. 11  is a perspective view of the combination of one of the lengthwise end portions of the process cartridge, and the corresponding portion of the gap maintaining member properly engaged with the process cartridge, in the second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, the process cartridges and gap maintaining member, which are in accordance with the present invention, will be described in detail with reference to the appended drawings. 
     Embodiment 1 
     First, referring to  FIGS. 1-9 , the first embodiment of the present invention will be described. 
       FIG. 1  is a schematic sectional view of a typical electrophotographic image forming apparatus compatible with a process cartridge in accordance with the present invention.  FIG. 2  is a schematic sectional view of a process cartridge in accordance with the present invention, and shows the general structure of the cartridge.  FIG. 3  is a perspective view of the developing means container unit  15  of the process cartridge in accordance with the present invention, showing the structure of the container.  FIGS. 4(   a ) and  4 ( b ) are  FIG. 4  are perspective views of one of the lengthwise end portions of the developing apparatus unit  8  of the process cartridge in accordance with the present invention, showing the structure of the developing apparatus unit  8 .  FIGS. 5(   a ) and  5 ( b ) are perspective views of the combination of the process cartridge and gap maintaining member  100  in the first embodiment of the present invention, showing the frame structure of the process cartridge, and how the gap maintaining member  100  is engaged with the process cartridge.  FIGS. 6(   a ) and  6 ( b ) are perspective views of one of the lengthwise end portions of the process cartridge, and corresponding portion of the gap maintaining member  100 , in the first embodiment of the present invention, showing how the gap maintaining member  100  is engaged with, or disengaged from, the process cartridge.  FIG. 7  is a plan view of one of the lengthwise ends of the process cartridge, and corresponding portion of the gap maintaining member  100 , showing how the gap maintaining member  100  is engaged with the process cartridge to maintain a preset amount of gap between the photosensitive member and developer bearing member, and also, between the photosensitive member and gap regulating member.  FIG. 8(   a ) is a plan view of the photosensitive member and developer bearing member, which are not in the image forming positions because of the presence of the gap maintaining member  100 , and  FIG. 8(   b ) is a plan view of the photosensitive member and developer bearing member, which are in the image forming positions because of the absence of the gap maintaining member  100 .  FIG. 9  is a schematic sectional view of a typical electrophotographic image forming apparatus which is compatible with a process cartridge in accordance with the present invention, showing what happens if the process cartridge in accordance with the present invention is mounted into the main assembly of the image forming apparatus without removing the gap maintaining member  100  from the process cartridge. 
     In the following description of the preferred embodiments of the present invention, the term “widthwise direction” of a process cartridge B means the direction in which the process cartridge B is mounted into, or removed from, the main assembly A 1  of an image forming apparatus  1 . The widthwise direction of the process cartridge B coincides with the direction in which a recording medium P is conveyed. The term “lengthwise direction” of the process cartridge B means the direction perpendicular (roughly perpendicular) to the direction in which the process cartridge B is mounted into, or removed from, the apparatus main assembly A 1 . The lengthwise direction of the process cartridge B is parallel to the surface of the recording medium P, and is perpendicular to the direction in which the recording medium P is conveyed. Further, the referential symbols used in the description are only for designating the various components, portions, etc., of the image forming apparatus and process cartridge, which are shown in the drawings. They are not intended to limit the present invention in terms of the structures of an image forming apparatus and a process cartridge. 
     &lt;General Structure of Electrophotographic Image Forming Apparatus&gt; 
     Referring to  FIG. 1 , an electrophotographic image forming apparatus A in this embodiment is a laser printer. It is made up of its main assembly A 1  and a process cartridge B. It has a cartridge cover  4 , which is a part of the external shell of the laser printer A. Opening the cartridge cover  4  makes it possible for the cartridge B to be mounted into, or removed from the apparatus main assembly A 1 . The laser printer A forms an image on the recording medium P (recording paper, OHP sheet, fabric, etc.) using an electrophotographic image formation process, which uses developer (which hereafter will be referred to as toner). The electrophotographic image forming process is carried out by the process cartridge B. 
     More specifically, first, the peripheral surface of the electrophotographic photosensitive member  10  (which hereafter will be referred to as photosensitive drum) is uniformly charged by a charge roller  11 , which is a charging means. Then, the uniformly charged peripheral surface of the photosensitive drum  10  is exposed to a beam of laser light L projected onto the peripheral surface of the photosensitive drum  10  from an exposing apparatus  1  (optical means) while being modulated with pictorial information. As a result, an electrostatic latent image, which reflects the pictorial information, is effected on the peripheral surface of the photosensitive drum  10 . The latent image on the photosensitive drum  10  is developed by the developing means  8  into a toner image. The developing means  8  will be described later. 
     Meanwhile, the recording mediums P in the sheet feeder cassette  6   a  are sequentially fed into the apparatus main assembly A 1  by the pickup roller  6   b , a pair of recording medium conveying rollers  6   c  and  6   e . Then, each recording medium P is conveyed to the nip between a transfer roller  3  (transferring means) and the photosensitive drum  10 , by a pair of recording medium conveying-and-turning guides  6   d  and  6   f  and a pair of registration rollers  6   g , in synchronism with the formation of the toner image. Thus, the conveyance of the recording medium P from the sheet feeder cassette  6   a  to the nip puts the recording medium P upside down. 
     Then, the recording medium P is conveyed through the nip formed between the photosensitive drum  10  and transfer roller  3  (transferring means), while a preset amount of voltage is applied to the transfer roller  3 . As the recording medium P is conveyed through the nip, the toner image developed on the photosensitive drum  10  is transferred onto the recording medium P. 
     After the transfer of the toner image onto the recording medium P, the recording medium P is guided to the fixing means  5  by a recording medium conveyance guide  6   h . The fixing means  5  is made up of a driver roller  5   c  and a heater  5   a . The driving roller  5   c  also functions as a pressure applying means. While the recording medium P is conveyed through the fixing means  5 , the fixing means  6  applies heat and pressure to the recording medium P and the toner image thereon. As a result, the toner image is fixed to the recording medium P. 
     Thereafter, the recording medium P is conveyed further by a recording medium conveyance guide  6   i , and then, is discharged into a delivery tray  7  by a pair of discharge rollers  6   j , with the image bearing surface facing downward. 
     &lt;Process Cartridge&gt; 
     The process cartridge B is made up of the photosensitive drum  10 , means for processing the photosensitive drum  10 , and a cartridge in which the photosensitive drum  10  and processing means are integrally disposed. The processing means are a charging means for charging the peripheral surface of the photosensitive drum  10 , a developing means for developing an electrostatic latent image formed on the peripheral surface of the photosensitive drum  10 , and a cleaning means for removing the toner remaining on the peripheral surface of the photosensitive drum  10 . The process cartridge B is required to have the photosensitive drum  10  and at least one of the processing means. 
     Referring to  FIG. 2 , in this embodiment, the process cartridge B is made up a photosensitive member unit  9  and a developing apparatus unit  8  (developing means). 
     The photosensitive member unit  9  of the process cartridge B has a first frame portion  12  (which hereafter will be referred to as waste toner container), the photosensitive drum  10 , and the charge roller  11 . The photosensitive drum  10  is for forming an electrostatic latent image. The charge roller  11  is for uniformly charging the peripheral surface of the photosensitive drum  10 . The photosensitive drum unit  9  also has a cleaning blade  14 , which scrapes the peripheral surface of the photosensitive drum  10  to remove from the peripheral surface, the residual toner T, that is, the toner remaining adhered to the peripheral surface of the photosensitive drum  10  without being transferred onto the recording medium P. The removed residual toner T collects in the waste toner container  12 . 
     The developing apparatus unit  8  of the process cartridge B is a developing means, as described above. It has a toner storage unit  25 , a development blade  17 , a developer bearing member  19  (which hereafter will be referred to as development sleeve), and a developing means container unit  15 , etc. There is a magnetic roller  16  (magnetic field generating means) in the hollow of the development sleeve  19 . 
     The toner storage unit  25  has a developer storage portion  20  (which hereafter will be referred to as toner storage container), and a second frame portion  26  (which hereafter will be referred to as guiding frame) ( FIG. 4(   a )). The toner storage container  20  stores the toner T. It is solidly connected to the guiding frame  26 . 
     There is a toner seal  13  between the toner storage container  20  and guiding frame  26 . The toner seal  13  prevents the unused toner T from leaking from the toner storage container  20 . Pulling out the toner seal  13  allows the toner T in the toner storage container  20  to flow into the developing means container unit  15 . 
     In this embodiment, the toner storage container  20  and the guiding frame  26 , which make up the toner storage container unit  25  by being solidly attached to each other, are independently formed. However, they may be integrally formed. 
     (Image Formation Process) 
     The developing apparatus unit  8  (developing means) sends the toner T in the toner storage container  20  to the development sleeve  19  through the opening  15   a  of the developing means container unit  15   a , by rotating a pair of stirring means  23   a  and  23   b . It has a developer stirring member  24  for circulating the toner T in the developing means container unit  15 . The developer stirring member  24  is rotatably disposed in the adjacencies of the development sleeve  19 . The developing apparatus unit  8  also has a blowout prevention seal  21  for keeping sealed the gap between the development sleeve  19  and the bottom portion of the developing means container unit  15 . That is, the blowout prevention seal  21  prevents the toner T from leaking downward relative to the position of the development sleeve  19 . 
     The developing apparatus unit  8  has a pair of magnetic seals  22 , which are located at the lengthwise ends of the development sleeve  19 , one for one, with the provision of a preset amount of gap between the peripheral surface of the development sleeve  19  and the magnetic seal  22 . The magnetic seal  22  prevents the toner T from leaking from the developing apparatus unit  8  through the gap between the lengthwise end of the development sleeve  19  and the developing means container unit  15 . More specifically, the magnetic seal  22  forms a magnetic field between itself and the magnetic roller  16  to form a brush of the toner T, in the abovementioned gap to prevent the toner T from leaking. 
     As described above, the toner T is sent to the development sleeve  19 , which is rotating, with the presence of the stationary magnetic roller  16  supported in the hollow of the development sleeve  19 . Thus, the toner T is borne on the peripheral surface of the development sleeve  19 , and is formed into a uniform layer of toner with a preset thickness, by the development blade  17 , while being frictionally charged by the development sleeve  19  and development blade  17 . 
     The lengthwise end portions of the development sleeve  19  are fitted with a pair of gap maintaining members  27   a  and  27   b  (which hereafter will be referred to as spacer ring), one for one ( FIG. 3 ). The spacer rings are roughly coaxial and are larger in radius than the development sleeve  19 , by the amount equal to the preset amount of clearance which the spacer rings are required to provide between the peripheral surface of the photosensitive drum  10  and the peripheral surface of the development sleeve  19 . The spacer rings  27   a  and  27   b  are kept pressed upon the peripheral surface of the photosensitive drum  10  by a pair of pressure generating members  28   a  and  28   b  (which hereafter will be referred to simply as spring) ( FIG. 8 ). With the presence of the spacer rings  27   a  and  27   b  between the peripheral surface of the development sleeve  19  and the peripheral surface of the photosensitive drum  10 , and also, the presence of the pressure from the springs  28   a  and  28   b , the preset amount of clearance is maintained between the peripheral surface of the development sleeve  19  and the peripheral surface of the photosensitive drum  10 . 
     The toner layer formed on the peripheral surface of the development sleeve  19  is moved by the rotational of the development sleeve  19  into the development area, in which the toner in the toner layer is transferred onto the peripheral surface of the photosensitive drum  10  in a manner to reversely reflect the electrostatic latent image on the peripheral surface of the photosensitive drum  10 . As a result, an image is formed of toner, on the peripheral surface of the photosensitive drum  10 . 
     The photosensitive drum  10  is rotated in the direction indicated by an arrow mark R 1 , while a preset amount of voltage is being applied to the charge roller  11  which is in contact with the peripheral surface of the photosensitive drum  10 . As a result, the portion of the photosensitive layer of the photosensitive drum  10 , which is in contact with the charge roller  11 , is uniformly charged. Then, the uniformly charged portion of the peripheral surface of the photosensitive drum  10  is exposed to a beam of laser light L projected onto the photosensitive drum  10  while being modulated with pictorial information. As a result, an electrostatic latent image is effected on the peripheral surface of the photosensitive drum  10 . Thereafter, the electrostatic latent image is developed into a toner image by the developing means. 
     The toner image formed on the peripheral surface of the photosensitive drum  10  is transferred onto the recording medium by applying such voltage that is opposite in polarity to the abovementioned toner image, to the transfer roller  3 , with which the laser printer A is provided. Thereafter, the residual toner T, that is, the toner T remaining on the peripheral surface of the photosensitive drum  10  after the toner image transfer, is removed by the cleaning blade  14 . More specifically, the cleaning blade  14  is placed in contact with the peripheral surface of the photosensitive drum  10  to scrape the peripheral surface of the photosensitive drum  10  to remove the residual toner T on the photosensitive drum  10 . After being removed from the peripheral surface of the photosensitive drum  10  by the cleaning blade  14 , the residual toner T collects in the waste toner container  12 . 
     (Frame Structure of Process Cartridge) 
     Referring to  FIG. 3 , the developing means container unit  15  is made up of a slide frame  29 , a right side frame  30 , and a left slide frame  31 . The right and left slide frames  30  and  31  are integrally attached to the slide frame  29 . The development sleeve  19  is rotatably supported by the right and left slide frames  30  and  31 , with the positioning of a pair of sleeve bearings (unshown) between the lengthwise ends of the development sleeve  19  and the right and left slide frame  30  and  31 , respectively. The development blade  17  is solidly attached to the slide frame  29 . 
     Referring to  FIGS. 3 ,  4 ( a ), and  4 ( b ), the top and bottom surfaces  30   a  and  30   b  of the right slide frame  30  of the developing means container unit  15  are parallel to each other, and control the direction in which the developing means container unit  15  slides (direction indicated by arrow mark S in  FIG. 4(   a )). Next, referring to  FIG. 4(   b ), the guiding frame  26  has a pair of guiding surfaces  26   a  and  26   b , which oppose the slide surfaces  30   a  and  30   b , respectively, when the developing means container unit  15  remains properly engaged in the guiding frame  26 . There is a spring  28   a  (pressure generating member) between the developing means container unit  15  and guiding frame  26 . Thus, the developing means container unit  15  is kept pressed toward the photosensitive member unit  9 . That is, the spring  28   a  presses the developing means container unit  15  in the direction to keep the development sleeve  19  virtually in contact with, or truly in contact with the photosensitive drum  10 . The slide surfaces  31   a  and  31   b  of the left slide frame  31 , and the guiding surfaces  26   d  and  26   e  of the guiding frame  26  (which opposes slide surfaces  31   a  and  31   b , respectively), and a spring  28   b , are the same in structure and positioning as those of the right slide frames  31  and right guiding frame  26 , and the spring  28   a  ( FIG. 6(   b )). 
     Further, the developing means container unit  15  is provided with a hole  15   c , which is rectangular in cross section, whereas the guiding frame  26  is provided with a boss  26   c  ( FIGS. 4(   a ) and  4 ( b )). The hole  15   c  and boss  26   c  are for accurately positioning the developing means container unit  15  and guiding frame  26  relative to each other in terms of their lengthwise direction. 
     Since the developing means container unit  15  and guiding frame  26  are structured as described above, the developing means container unit  15  slides straight in the widthwise direction (indicated by arrow mark S in  FIG. 4(   a )), relative to the guiding frame  26 . 
     Referring to  FIG. 5(   a ), the photosensitive member unit  9 , and the toner storage unit  25  of the developing apparatus unit  8  are kept solidly attached to each other, by first and second side covers  32  and  33 , which are located at one lengthwise end of the process cartridge B and the other, respectively. Hereafter, the first side cover  32  will be referred to as the right side cover, whereas the second side cover will be referred to as the left side cover. 
     Since the process cartridge B is structured as described above, the developing means container unit  15  is allowed to slide straight in the direction indicated by the arrow mark S in  FIG. 4(   a ), relative to the toner storage unit  25 . As the developing means container unit  15  is moved toward the toner storage unit  25  as described above, the spacer rings  27   a  and  27   b , with which the lengthwise end portions of the development sleeve  19  supported by the developing means container unit  15  are fitted, one for one, are placed in contact with the peripheral surface of the photosensitive drum  10  supported by the photosensitive member unit  9 . As a result, the developing means container unit  15  becomes fixed in position in terms of its widthwise direction. Therefore, the development sleeve  19  is pressed toward the photosensitive drum  10 , with the presence of the spacer rings  27   a  and  27   b  between the development sleeve  19  and photosensitive drum  10 , while the developing means container unit  15  and toner storage container  20  remain in the state in which the weight of the toner T in the toner storage container  20  is likely to rest on the developing means container unit  15 . 
     &lt;Gap Maintaining Means&gt; 
     In this embodiment, the process cartridge B is provided with a gap maintaining means, that is, a means for keeping the distance between the axial line of the photosensitive drum  10  and the axial line of the development sleeve  19  greater when the process cartridge B is distributed than when the process cartridge  5  is being used for image formation, that is, a means for keeping the spacer rings  27   a  and  27   b , with which the lengthwise ends of the development sleeve  19  are fitted one for one, separated from the photosensitive drum  10  during the distribution of the process cartridge B. 
     Referring to  FIG. 5(   a ), the gap maintaining means in this embodiment is a gap maintaining member  100 , which has a pair of gap maintaining portions  100   a  and  100   b , and a handgrip portion  100   c  which is gripped by a user to take hold of the gap maintaining member  100 . The gap maintaining member  100  is removably attachable to the process cartridge B. The gap maintaining member  100  is shaped ( FIG. 5(   b )) to cover the exposure window  12   c , with which the waste toner container  12  is provided to allow the beam of laser light L to be projected onto the peripheral surface of the photosensitive drum  10  while being modulated with pictorial information. The process cartridge B may be structured so that the exposure window  12   c  is provided between the waste toner container  12  and guiding frame  26 . 
     The handgrip portion  100   c  of the gap maintaining member  100  is on the opposite side of the gap maintaining member  100  from the portion of the gap maintaining member  100 , which is for covering the exposure window  12   c . Next, referring to  FIG. 5(   b ), the gap maintaining member  100  is shaped so that when the gap maintaining member  100  remains attached to the process cartridge B, the handgrip portion  100   c  extends from the process cartridge B by a substantial distance beyond the top surface of the waste toner container  12 . 
     Next, referring to  FIGS. 6(   a ) and  6 ( b ), in this embodiment, the waste toner container  12  is provided with a pair of contact surfaces  12   a  and  12   b , which come into contact with the gap maintaining portions  100   a  and  100   b  of the gap maintaining member  100 , respectively. The waste toner container  12  is structured so that when the gap maintaining member  100  remains attached to the process cartridge B, the contact surfaces  12   a  and  12   b  are perpendicular to the straight line connecting the axial line O 1  of the photosensitive drum  10  and the axial line O 2  of the development sleeve  19  (Line Y-Y in  FIG. 7) . 
     The gap maintaining means is a the means for keeping the distance between the axial line of the photosensitive drum  10  and the axial line of the development sleeve  19  greater when it remains attached to the process cartridge B than when the process cartridge B is being used for image formation, and also, for keeping the spacer rings  27   a  and  27   b , with which the lengthwise ends of the development sleeve  19  are fitted one for one, separated from the photosensitive drum  10  when it remains attached to the process cartridge B. It works in the following manner. 
     That is, the gap maintaining member  100  is to be positioned, as shown in  FIG. 5(   a ), relative to the process cartridge B, and then, is to be moved in the direction indicated by an arrow mark M in  FIG. 5  so that its gap maintaining portions  100   a  and  100   b  follow a pair of gap maintain member insertion guides  32   a  and  32   b , with which the right and left side covers  32  and  33  are provided, respectively. In other words, the gap maintaining member  100  is to be positioned, as shown in  FIG. 5(   a ), relative to the process cartridge B, and then, is to be moved in the direction indicated by the arrow mark M in  FIG. 5  so that its gap maintaining portions  100   a  and  100   b  enter the gaps between the contact surfaces  12   a  and  12   b  of the waste toner container  12 , and the right and left side frames  30  and  31  of the developing means container unit  15 , respectively. Then, the gap maintaining member  100  is to be pressed further inward of the process cartridge B so that the developing means container unit  15  is separated from the waste toner container  12  against the resiliency of the springs  28   a  and  28   b  ( FIG. 8(   a )). 
     The direction in which the developing means container unit  15  is slid as the gap maintaining member  100  is pressed further into the process cartridge B is the direction indicated by an arrow mark S in  FIG. 7 . The direction in which the gap maintaining member  100  is pressed into the process cartridge B, or pulled out of the process cartridge B, is the direction indicated by an arrow mark M or N, respectively, in  FIG. 7 . The relationship between the developing means container unit  15  slides and the direction in which the gap maintaining member  100  is pressed into, or removed from, the process cartridge B, is such that the weight of the developing means container unit  15  and the resiliency of the springs  28   a  and  28   b  press the gap maintaining member  100  on the contact surfaces  12   a  and  12   b . Therefore, the gap maintaining member  100  is secured between the contact surfaces  12   a  and  12   b  of the waste toner container  12  and the developing means container unit  15 , by the weight of the developing means container unit  15  and the force generated by the resiliency of the springs  28   a  and  28   b.    
     The gap maintaining portions  100   a  and  100   b  of the gap maintaining member  100  are subjected to the force generated by the resiliency of the springs  28   a  and  28   b  through the developing means container unit  15 . They are also indirectly subjected, through the developing means container unit  15 , to the impact to which the process cartridge B is subjected during the distribution of the process cartridge B. 
     Therefore, the width and thickness of the gap maintaining portions  100   a  and  100   b  of the gap maintaining member  100  are set to ensure that when the gap maintaining member  100  remains properly attached to the process cartridge B, the distance between the axial line of the photosensitive drum  10  and the axial line of the development sleeve  19  remains greater than when the process cartridge B is being used for image formation, or to ensure that when the gap maintaining member  100  remains properly attached to the process cartridge B, the spacer rings  27   a  and  27   b , with which the lengthwise ends of the development sleeve  19  are fitted one for one, remain separated from the photosensitive drum  10 , even if the process cartridge B is subjected to a substantial amount of impact during the distribution of the process cartridge B. 
     The gap maintaining member  100  has to be removed from the process cartridge B before the process cartridge B is mounted into the laser printer A. The gap maintaining member  100  can be removed by pulling it by gripping the handgrip portion of the gap maintaining member  100  (direction in which gap maintaining member  100  is to be moved is indicated by arrow mark N in  FIG. 7 ). As the gap maintaining member  100  is pulled out in the abovementioned direction, the developing means container unit  15  is slid straight toward the photosensitive member unit  9  by the force generated by the resiliency of the springs  28   a  and  28   b . As a result, the spacer rings  27   a  and  27   b , with which the lengthwise end portions of the development sleeve  19  are fitted, are pressed upon the peripheral surface of the photosensitive drum  10  ( FIG. 8(   b )). At the same time, the exposure windows  12   c  becomes exposed, allowing the beam of laser light L projected while being modulated with the pictorial information, to reach the peripheral surface of the photosensitive drum  10 . It is only when the process cartridge B is in the above described condition that the process cartridge B can be mounted into the laser printer A. 
     In the case of a process cartridge, such as the process cartridge B, structured as described above, the weight of the toner T in the toner storage container  20  is unlikely to rest on the developing means container unit  15 . Therefore, in practical terms, it is only the developing means container unit  15  itself that affects the gap maintaining portions  100   a  and  100   b  of the gap maintaining member  100 . 
     Therefore, in the case of a process cartridge structured as described above, the effect which the weight of the toner T in the toner storage container  20  has on the gap maintaining portions  100   a  and  100   b  of the gap maintaining member  100  when the process cartridge B is subjected to impact during the distribution of the process cartridge B, is significantly smaller than in the case of a process cartridge structured in accordance with the prior art. 
     Further, the gap maintaining means in this embodiment is also very effectively usable with a process cartridge of a large capacity. That is, even when the gap maintaining member  100  is produced for a process cartridge of a large capacity, the width and thickness of the gap maintaining portions  100   a  and  100   b  of the gap maintaining member  100  may be the same as those when the gap maintaining member  100  is produced for a process cartridge of a small capacity. In other words, the gap maintaining means in this embodiment can be used even with a process cartridge of a large capacity to ensure that when the gap maintaining member  100  remains properly attached to the process cartridge B, the distance between the axial line of the photosensitive drum  10  and the axial line of the development sleeve  19  remains greater than when the process cartridge B is being used for image formation, or to ensure that when the gap maintaining member  100  remains properly attached to the process cartridge B, the spacer rings  27   a  and  27   b , with which the lengthwise ends of the development sleeve  19  are fitted one for one, remain separated from the photosensitive drum  10 . In other words, regardless of process cartridge capacity, the gap maintaining means in this embodiment can prevent the problem that the photosensitive drum  10 , development sleeve  19 , and/or spacer rings  27   a  and  27   b  are damaged during the distribution of the process cartridge B. 
     The force to which the gap maintaining portions  100   a  and  100   b  of the gap maintaining member  100  are subjected when the gap maintaining member  100  is disengaged from the process cartridge B is only the force generated by the resiliency of the springs  28   a  and  28   b , and the weight of the developing means container unit  15 . Therefore, the amount of force necessary to disengage the gap maintaining member  100  from the process cartridge B is significantly smaller than that required to disengage a gap maintaining member ( 100 ) in accordance with the prior art from a process cartridge (B) in accordance with the prior art. 
     Further, while the gap maintaining member  100  remains properly engaged with the process cartridge B, the exposure window  12   c  remains covered with the gap maintaining member  100 . Therefore, until the gap maintaining member  100  is disengaged from the process cartridge B (inclusive of while process cartridge B is distributed), the dust and light have no chance to enter the process cartridge B, being thereby prevented from derogatorily affecting the photosensitive drum  10 . 
     Further, unless the gap maintaining member  100  is completely disengaged from the process cartridge B, the process cartridge B cannot be mounted into the laser printer A. More specifically, referring to  FIG. 9 , if an attempt is made to mount the process cartridge B into the laser printer A without removing the gap maintaining member  100 , the handgrip portion  100   c  of the gap maintaining member  100 , which protrudes in the opposite direction from the exposure window  12   c , comes into contact with the internal cover  4   a  of the laser printer A, and prevents the process cartridge B from being inserted further into the laser printer A. In other words, the handgrip portion  100   c  of the gap maintaining member  100  reminds a user that the user forgot to remove the gap maintaining member  100  from the process cartridge B, preventing thereby the user from improperly mounting the process cartridge B into the laser printer A. 
     Incidentally, in this embodiment of the present invention, the process cartridge B and gap maintaining member  100  were structured so that the gap maintaining portions  100   a  and  100   b  of the gap maintaining member  100  come into contact with the contact surfaces  12   a  and  12   b  of the waste toner container  12 . However, the process cartridge B and gap maintaining member  100  may be structured so that the right and left side cover  32  and  33  are provided with the contact surfaces, with which the gap maintaining portions  100   a  and  100   b  of the gap maintaining member  100  come into contact, respectively. The effect of such structural arrangement is the same as that of this embodiment, that is, the structural arrangement which uses the contact surfaces  12   a  and  12   b  of the waste toner container  12  as the surfaces with which the gap maintaining portions  100   a  and  100   b  of the gap maintaining member  100  come into contact. 
     Also in this embodiment of the present invention, the process cartridge B and gap maintaining member  100  were structured so that as the gap maintaining member  100  is engaged with the process cartridge B, the gap maintaining portions  100   a  and  100   b  of the gap maintaining member  100  come into, and remain in, contact with a part of the right frame  30  of the developing means container unit  15 , and a part of the left frame  31 , respectively. However, the process cartridge B and gap maintaining member  100  may be modified in structure so that the slide frame  29  functions as the portion of the process cartridge B, with which the gap maintaining portions  100   a  and  100   b  of the gap maintaining member  100  come into contact, and remain in contact. Also in this case, the gap maintaining member  100  can function as the gap maintaining means just as effectively as in the case in which the process cartridge B and gap maintaining member  100  are structured so that the gap maintaining portions  100   a  and  100   b  of the gap maintaining member  100  come into contact, and remain in contact, with the right and left slide frames  30  and  31 , respectively. 
     Embodiment 2 
     Next, referring to  FIGS. 10 and 11 , the second embodiment of the present invention will be described.  FIG. 10  is a schematic perspective view of the gap maintaining member in this embodiment, and depicts the structure of the gap maintaining member.  FIG. 11  is a perspective view of the lengthwise end portion of the process cartridge when the gap maintaining member in this embodiment is properly engaged with the process cartridge in this embodiment. 
     The gap maintaining member  100 A, that is, the gap maintaining member in this embodiment, is the same in structure as the gap maintaining member  100 , that is, the gap maintaining member in the first embodiment. Thus, the portions of the gap maintaining member  100 A, which are the same in structure and function as the counterparts of the gap maintaining member  100 , are given the same referential symbols as those given to the counterparts, so that the description of the counterparts of the gap maintaining member  100  can be employed to avoid the repetition of the same description. 
     Referring to  FIG. 10 , the gap maintaining portions  100   a  and  100   b  of the gap maintaining member  100 A have portions  100   d  and  100   e , which come into contact, and remain in contact, with the right and left slide frame  30  and  31 , respectively. These portions  100   d  and  100   e  are in the form of a recess (or bulge), the depth (or height) direction of which is roughly perpendicular to the direction (indicated by arrow mark M) in which the gap maintaining member  100 A is engaged into the process cartridge B, and the direction (indicated by arrow mark N) in which the  100 A is disengaged from the process cartridge B. Thus, the portion of the right slide frame  30 , which engages with the portion  100   d  of the gap maintaining portion  100   a  of the gap maintaining member  100 , and the portion of the left slide frame  31 , which engages with the portion  100   e  of the gap maintaining portion  100   b  of the gap maintaining member  100 , are in the form of a bulge (or recess). Although  FIG. 11  does not show the left slide frame  31 , the left slide frame  31  is the same in structure as the right slide frame  30 . 
     In the first embodiment of the present invention, the force which is generated by the resiliency of the springs  28   a  and  28   b  and presses on the gap maintaining portions  100   a  and  100   b  of the gap maintaining member  100  through the developing means container unit  15 , was used to prevent the gap maintaining member  100  from unexpectedly moving in the direction in which the gap maintaining member  100  is to be engaged into, or disengaged from, the process cartridge B. Further, the weight of the developing means container unit  15  itself is utilized to prevent the gap maintaining member  100  from unexpectedly moving in the direction in which the gap maintaining member  100  is to be engaged into, or disengaged from, the process cartridge B, by keeping the gap maintaining portion  100   a  sandwiched between the contact surface  12   a  of the waste toner container  12 , and the right slide frame  30 , and keeping the gap maintaining portion  100   b  sandwiched between the contact surface  12   b  of the waste toner container  12 , and the right slide frame  30 . 
     However, this setup suffers from the following problem if the amount of the friction generated between the gap maintaining member  100  and the process cartridge B by the force which is generated by the resiliency of the springs  28   a  and  28   b  and presses on the gap maintaining member  100  through the developing means container unit  15 , and the force which is generated by the weight of the developing means container unit  15  and pressed on the gap maintaining member  100 , is smaller than the amount of the force generated by the impact to which the process cartridge B is subjected during the distribution of the process cartridge B. 
     That is, it is possible that the moment the process cartridge B is impacted during its distribution, the gap maintaining member  100  will be moved in the direction in which it is to be disengaged (direction indicated by arrow N), and will not return to the original position. 
     In this embodiment, therefore, the gap maintaining portions  100   a  and  100   b  of the gap maintaining member  100 A are provided with portions  100   d  and  100   e , which are in the form of a recess (or bulge), the depth (or height) direction of which is roughly perpendicular to the direction (indicated by arrow mark M) in which the gap maintaining member  100 A is engaged into the process cartridge B, and the direction (indicated by arrow mark N) in which the  100 A is disengaged from the process cartridge B. The provision of these recesses (bulges) increases in size the area of contact between the gap maintaining member  100 A and the right slide frame  30 , and the area of contact between the gap maintaining member  100 A and the left slide frame  31 , increasing thereby the amount of friction between the gap maintaining member  100 A and right slide frame  30 , and the amount of friction between the gap maintaining member  100 A and left slide frame  31 . In other words, the employment of the structural arrangement, in this embodiment, for the process cartridge B and gap maintaining member  100 A makes it possible to increase the amount of force necessary to move the gap maintaining member  100 A, making thereby the process cartridge B and gap maintaining member  100 A more resistant to the external impact, in terms of the amount of impact. Therefore, the combination of the process cartridge B and gap maintaining member  100 A in this embodiment is superior to the combination of the process cartridge B and gap maintaining member  100  in the first embodiment, in terms of the prevention of the disengagement of a gap maintaining member from a process cartridge. 
     Incidentally, the impact to which the process cartridge B is subjected during the distribution of the process cartridge B may sometimes exceed in magnitude even the abovementioned increased friction, that is, may be large enough to displace the gap maintaining member  100 A. However, as long as the amount of the displacement is slight, the force generated by the resiliency of the springs  28   a  and  28   b , and the weight of the developing means container unit  15 , function to move the gap maintaining member  100 A back to where it was. Therefore, the combination of the process cartridge B and gap maintaining member in this embodiment is far superior to the combination of the process cartridge B and gap maintaining member in the first embodiment, in terms of the prevention of the disengagement of a gap maintaining member from a process cartridge in the direction in which the process cartridge is to be disengaged (direction indicated by arrow mark N). 
     The present invention relates to a process cartridge, which is made up of a photosensitive member unit, a toner storage unit solidly attached to the photosensitive member unit, and a developer bearing member supporting frame movable relative to the toner storage unit, and which is characterized in that it can significantly reduce the effect which the weight of the developer storage portion has upon the portion of the peripheral surface of the electrophotographic photosensitive member, which is in contact with the developer bearing member, when a process cartridge is subjected impact during its distribution. More specifically, according to the present invention, a combination of a process cartridge and a gap maintaining member is structured so that after the completion of the process cartridge, the process cartridge is fitted with the gap maintaining member to displace the developer bearing member supporting frame against the force generated by a pair of pressure generating members, in order to keep the distance between the rotational axis of the electrophotographic photosensitive member and the rotational axis of the developer bearing member greater during the distribution of the process cartridge than when the process cartridge is being used for image formation, or to keep the electrophotographic photosensitive member separated from a pair of gap regulating members, with which the lengthwise end portions of the developer bearing member are fitted, one for one, during the distribution of the process cartridge. 
     Thus, the present invention makes it possible to reduce the distance by which a developer bearing member needs to be moved to increase the distance between an electrophotographic photosensitive member and the developer bearing member for the distribution of a process cartridge, compared to the distance which is kept between the electrophotographic photosensitive and developer bearing member when the process cartridge is being used for image formation, or to reduce the distance which needs to be kept between an electrophotographic photosensitive member and a pair of gap regulating members with which the lengthwise end portions of the developer bearing member are fitted, for the distribution of a process cartridge. Therefore, the present invention can make it possible to reduce in size the gap maintaining member for preventing an electrophotographic photosensitive member, a developer bearing member, and/or a gap regulating member from being damaged (deformed) during the distribution of a process cartridge, even for a process cartridge of a large size. Further, according to the present invention, the force to which the gap maintaining member is subjected is only the force generated by the resiliency of the pressure generating members, and the weight of the movable frame. Therefore, the employment of the present invention can make it possible to reduce the amount of force necessary to disengage the gap maintaining member from a process cartridge. 
     While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth, and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following claims. 
     This application claims priority from Japanese Patent Application No. 105689/2007 filed Apr. 13, 2007, which is hereby incorporated by reference.