Abstract:
An electrophotographic image forming apparatus in the state that cartridge is detachably mounted to a main assembly of the apparatus, the apparatus includes a cartridge supporting member movable between an inside position in the main assembly and an outside position outside the main assembly when a cartridge is mountable thereto and dismountable from the cartridge supporting member; a first opening through which the cartridge supporting member passes between the inside position and the outside position; a first openable member for openably closing the first opening; a second opening continuing from the first opening and provided above the first opening, the second opening being effective to permit the cartridge to be removed from the cartridge supporting member in the state that cartridge supporting member takes the outside position and being effective to permit the supporting member to support the cartridge; a second openable member for openably closing the second opening, the second openable member being effective to prevent external light from entering the main assembly when the second openable member closes the second opening; and an interrelating means for moving the second openable member to the opening position in interrelation with movement of the supporting member from the inside position to the outside position.

Description:
FIELD OF THE INVENTION AND RELATED ART 
       [0001]    The present invention relates to an electrophotographic image forming apparatus which forms an image on recording medium while keeping image formation cartridges removably mounted in its main assembly. 
         [0002]    Here, an “electrophotographic image forming apparatus” means an apparatus which forms a color image on recording medium with the use of an electrophotographic image forming process. Examples of an electrophotographic color image forming apparatus include an electrophotographic color copying machine, an electrophotographic color printer (color laser beam printer, color LED printer, etc.), a color facsimile apparatus, a color wordprocessor, etc. “Recording medium” means medium, such as a sheet of paper, an OHP sheet, etc., on which an image can be formed by an electrophotographic image forming apparatus. 
         [0003]    A “cartridge” means a process cartridge or a development cartridge, which contributes to the process of forming an image on recording medium by being removably mounted in the main assembly of an electrophotographic image forming apparatus. The abovementioned process cartridge is a cartridge in which an electrophotographic photosensitive drum, and one or more processing means for processing the photosensitive drum, are integrally disposed, and which is removably mountable in the main assembly of an electrophotographic image forming apparatus. The processing means are such means as a charging means, a developing means, and a cleaning means that are for processing the photosensitive drum. Thus, a “process cartridge” includes a cartridge in which a developing means (processing means), and an electrophotographic photosensitive drum, are integrally disposed, and which is removably mountable in the main assembly of an electrophotographic image forming apparatus. It also includes a cartridge in which a charging means (processing means), a developing means (processing means) or a cleaning means (processing means), and an electrophotographic photosensitive drum, are integrally disposed, and which is removably mountable in the abovementioned main assembly. Incidentally, a process cartridge in which an electrophotographic photosensitive drum and a developing means are integrally disposed is referred to as a process cartridge of the so-called integration type, whereas a process cartridge in which an electrophotographic photosensitive drum, and processing means other than a developing means, are integrally disposed, is referred to as a process cartridge of the so-called separation type. 
         [0004]    A process cartridge can be mounted into, or removed from, the main assembly of an electrophotographic image forming apparatus by a user himself or herself. Therefore, the employment of a process cartridge makes it easier to maintain an electrophotographic image forming apparatus. By the way, the processing means are means which process an electrophotographic photosensitive drum. 
         [0005]    A development cartridge is a cartridge in which a development roller is disposed. It also holds developer (toner) used by the development roller to develop an electrostatic latent image formed on an electrophotographic photosensitive drum. It is removably mounted in the main assembly of an electrophotographic image forming apparatus. In the case of an electrophotographic image forming apparatus which uses a development cartridge, its electrophotographic photosensitive drum is attached to the main assembly of the image forming apparatus, or the cartridge supporting member of the apparatus, which will be described later, or it is disposed in a process cartridge (which does not have developing means) of the so-called separation type. A development cartridge also can be mounted into, or removed from, the main assembly of an image forming apparatus by a user himself or herself, and therefore, can make it easier to maintain the main assembly. 
         [0006]    Thus, process cartridges to which the present invention is applicable include the process cartridges of the so-called integration type, as well as the process cartridges of the so-called separation type. Further, the electrophotographic image forming apparatuses to which the present invention is applicable include electrophotographic image forming apparatuses which employ in pair a process cartridge of the so-called separation and a development cartridge. Moreover, they also include such development cartridges that are removably mountable in an electrophotographic image forming apparatus, the electrophotographic photosensitive member of which is unremovably attached to the main assembly of the apparatus, or the cartridge supporting member of the apparatus, which will be described later. 
         [0007]    As the structural arrangement for mounting a cartridge (for example, process cartridge) in the main assembly of an electrophotographic image forming apparatus, or removing the cartridge from the main assembly, the following structural arrangement has been known. An electrophotographic image forming apparatus and the process cartridge therefor are structured so that the cartridges can be removably mounted in the tray of the main assembly of the apparatus, which can be pulled out of the main assembly (US2006/0067734). There has also been known an image forming apparatus, the top portion of which is provided with a lip which can be upwardly opened (Japanese Laid-open Patent Application H04-296885). 
         [0008]    It is reasonable to think that in order to replace the process cartridge, which is at the rearmost end of the cartridge tray of a conventionally structured electrophotographic image forming apparatus, it is necessary to pull virtually entire cartridge tray out of the main assembly of the image forming apparatus. Therefore, the space for setting up a conventionally structured electrophotographic image forming apparatus has to be large enough to provide the space for allowing the cartridge tray to be pulled out frontward of the main assembly of the apparatus. 
         [0009]    Some image forming apparatuses having a top lid which is to be upwardly opened are structured so that the top lid is opened by the force from a motor. 
         [0010]    The present invention was made in consideration of the above-described concerns. 
       SUMMARY OF THE INVENTION 
       [0011]    The primary object of the present invention is to provide an electrophotographic image forming apparatus which is significantly smaller in the operational space it requires, and also, is significantly easier in terms of the operation for mounting or dismounting cartridges than a conventionally structured electrophotographic image forming apparatus. 
         [0012]    Another object of the present invention is to provide an electrophotographic image forming apparatus which is significantly smaller in the operational space it requires, and also, is significantly easier in terms of the operation for removing the recording medium which has stuck in the main assembly of the apparatus. 
         [0013]    Another object of the present invention is to provide an electrophotographic image forming apparatus, the doors of which can be opened or closed by the movement of the cartridge supporting member of the apparatus. 
         [0014]    Another object of the present invention is to provide an electrophotographic image forming apparatus structured so that the recording medium which has stuck in its recording medium conveyance passage which is behind the innermost position the cartridge supporting member can be easily removed. 
         [0015]    Another object of the present invention is to provide an electrophotographic image forming apparatus structured so that the recording medium has stuck in the recording medium conveyance passage which is below the innermost position of the cartridge supporting member can be easily removed. 
         [0016]    According to an aspect of the present invention, there is provided an electrophotographic image forming apparatus for forming an image on a recording material in the state that cartridge is detachably mounted to a main assembly of said electrophotographic image forming apparatus, said electrophotographic image forming apparatus comprising a cartridge supporting member movable between an inside position in said main assembly of the apparatus and an outside position outside said main assembly of the apparatus when a cartridge is mountable thereto and dismountable from said cartridge supporting member; a first opening through which said cartridge supporting member passes between the inside position and the outside position; a first openable member for openably closing said first opening; a second opening continuing from said first opening and provided above said first opening, said second opening being effective to permit the cartridge to be removed from said cartridge supporting member in the state that cartridge supporting member takes the outside position and being effective to permit said cartridge supporting member to support said cartridge; a second openable member for openably closing said second opening, said second openable member being effective to prevent external light from entering said main assembly of the apparatus when said second openable member closes said second opening; and an interrelating means for moving said second openable member to the opening position in interrelation with movement of said cartridge supporting member from the inside position to the outside position. 
         [0017]    The present invention can make it easier to mount a cartridge into an electrophotographic image forming apparatus, or remove a cartridge from the apparatus, while reducing the space necessary for the operation of the main assembly of the electrophotographic image forming apparatus. 
         [0018]    The present invention can make it easier to remove the recording medium which has stuck in an electrophotographic image forming apparatus, while reducing the space necessary for the operation of the main assembly of the image forming apparatus. 
         [0019]    The present invention can make it possible for the movable covers (door, lid, etc.) of an electrophotographic image forming apparatus to be opened or closed by the movement of the cartridge supporting member of the apparatus. 
         [0020]    The present invention can make it easier to remove the recording medium having stuck in the recording medium conveyance passage which is on the rear side of the innermost position for the cartridge supporting member. 
         [0021]    The present invention can make it easier to remove the recording medium having stuck in the recording medium conveyance passage which is on the under side of the innermost position for the cartridge supporting member. 
         [0022]    These and other objects, features, and advantages of the present invention will become more apparent upon consideration of the following description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  is a drawing for describing the image forming apparatus in the first preferred embodiment of the present invention. 
           [0024]      FIG. 2  is a drawing for describing the operation for replacing the cartridges in the image forming apparatus in the first preferred embodiment. 
           [0025]      FIG. 3  is a drawing for describing the mechanism for causing the movement of the tray to move the covers, in the first preferred embodiment. 
           [0026]      FIG. 4  is a drawing for describing the image forming apparatus in the first preferred embodiment. 
           [0027]      FIG. 5  is a drawing for describing the mechanism for causing the movement of the tray to move the covers, in the first preferred embodiment. 
           [0028]      FIG. 6  is a drawing for describing the mechanism for causing the movement of the tray to move the covers, in the first preferred embodiment. 
           [0029]      FIG. 7  is a drawing for describing the mechanism for causing the movement of the tray to move the covers, in the first preferred embodiment. 
           [0030]      FIG. 8  is a drawing for describing the mechanism for causing the movement of the tray to move the covers, in the first preferred embodiment. 
           [0031]      FIG. 9  is a drawing for describing the image forming apparatus in the second preferred embodiment of the present invention. 
           [0032]      FIG. 10  is a drawing for describing the image forming apparatus in the second preferred embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0033]    Hereinafter, the image forming apparatuses in the preferred embodiments of the present invention will be concretely described with reference to the appended drawings. 
       Embodiment 1  
     (Overall Structure of Image Forming Apparatus) 
       [0034]    First, referring to  FIGS. 1 and 2 , the overall structure of the electrophotographic image forming apparatus in the first preferred embodiment of the present invention will be described. 
         [0035]    The image forming apparatus  200  in this embodiment of the present invention is a full-color laser printer, which uses an electrophotographic image formation process and four primary colors. The image forming apparatus  200  forms an image on a sheet  14  (recording medium), in response to the image formation signals inputted from an external host apparatus (unshown), for example, a personal computer, an image reader, or the like. Here, recording medium means any medium, for example, paper, OHP sheet, label, etc., on which an image can be formed with the use of an electrophotographic image formation process. 
         [0036]    In the following descriptions of the preferred embodiments of the present invention, the front side of the image forming apparatus  200  means the side where a door  28  (member which can be opened or closed) is present, and the rear side of the image forming apparatus means the side opposite from the front side. Further, the left or right side of the image forming apparatus means the left or right side when the main assembly  100  is seen from the front side. Further, the rear side is the upstream side in terms of the direction  300  (indicated by arrow mark in  FIG. 2 ) in which a tray  26  (cartridge supporting member), which will be described later, is moved from its innermost position I to its outermost position O. The front side is the downstream side in terms of the direction  300 . 
         [0037]    Referring to  FIG. 2 , the main assembly  100  (which hereafter may be referred to as apparatus main assembly) of the image forming apparatus contains four process cartridges  3  (which hereafter will be referred to simply as “cartridge  3 ”), more specifically, first to fourth cartridges  3  ( 3 Y,  3 M,  3 C, and  3 K) (listing from rear), respectively, which were horizontally mounted in parallel in the main assembly  100 . The four cartridges  3  are the same in structure, although they are different from each other in the color of the developer (toner) they contain. 
         [0038]    Each of the cartridges  3  in this embodiment is made up of a rotatable photosensitive drum  1  ( 1 Y,  1 M,  1 C, or  1 K), three processing means for processing the photosensitive drum  1 , and a cartridge frame. More specifically, three processing means are a charging member  10 , a developing device having a development roller  2  ( 2 Y,  2 M,  2 C, or  2 K), etc., and a cleaning device  11 . The photosensitive drum  1  and the three processing means are integrally attached to the inward side of the cartridge frame  5 . The charging device  10  is in the form of a roller, and charges the photosensitive drum  1 . The cleaning device  11  is in the form of a blade, and removes the toner remaining on the photosensitive drum  1  after transfer. After being charged by the charging device  10 , the photosensitive drum  1  is irradiated with a beam of laser light, which will be described later. As a result, an electrostatic latent image is formed on the photosensitive drum  1 . The electrostatic latent image is developed by the development roller  2 , which uses toner (developer). Consequently, a visible image (which hereafter will be referred to as toner image or developer image) is formed of toner (developer), on the photosensitive drum  1 . 
         [0039]    The first cartridge  3 Y contains yellow toner in its developing device (developer storage), and forms a yellow toner image on its photosensitive drum  1 . The second cartridge  3 M contains magenta (M) toner, and forms a magenta toner image on its photosensitive drum  1 . The third cartridge  3 C contains cyan toner in its developing device, and forms a cyan toner image on its photosensitive drum  1 . The fourth cartridge  3 K contains black toner, and forms a black toner image on its photosensitive drum  1 . 
         [0040]    The main assembly  100  is provided with a laser scanner unit  25 , which is above the cartridges  3 Y,  3 M,  3 C, and  3 K. The unit  25  scans (exposes) the peripheral surface of the photosensitive drum  1  of each cartridge  3 , by outputting a beam of laser light while modulating the beam of laser light with the information regarding each of the monochromatic images, which is inputted from the external host apparatus (unshown). 
         [0041]    The main assembly  100  is also provided with an intermediary transfer belt unit  60 , which is below the cartridges  3 Y,  3 M,  3 C, and  3 K. The belt unit  60  has an endless belt  18  (intermediary transfer member), a driver roller  16 , and a tension roller  19 . The endless belt  18  is formed of a dielectric material, and is flexible. The driver roller  16  circularly drives the belt  18 . 
         [0042]    The photosensitive drum  1 , which each cartridge  3  has, is in contact with the belt  18  by the bottom portion of the peripheral surface of the drum  1 . The main assembly  100  is provided with four primary transfer rollers (unshown), which are disposed within the loop which the transfer belt  18  forms. Further, the main assembly  100  is provided with a secondary transfer roller  17 , which is kept pressed against the roller  16 , with the presence of the belt  18  between the two rollers  17  and  16 . 
         [0043]    The main assembly  100  is provided with a recording medium feeder unit  61 , which is in the bottom portion of the main assembly  100 . The recording medium feeder unit  61  has a feeder tray  13 , a feeder roller  15   a,  a separation roller  15   b,  etc. The tray  13  is removably mountable in the main assembly  100  from the front side of the main assembly  100  (front loading). 
         [0044]    Further, the main assembly  100  is provided with a fixing apparatus  20  and a pair of discharge rollers  22 , which are in the top rear portion of the main assembly  100 . A part of the top wall of the main assembly  100  is in the form of a delivery tray  24 . 
         [0045]    In an image forming operation, four monochromatic toner images, different in color, are formed on the four photosensitive drums  1 , one for one, with the use of an electrophotographic image formation process. Then, the four toner images are sequentially transferred (primary transfer) onto the rotating belt  18 . As a result, a full-color image is effected on the belt  18 . In synchronism with the progression of this image forming operation, a sheet  14  (of recording medium) is conveyed into the secondary transfer portion, which is the nip between the secondary transfer roller  17  and belt  18 , while a bias is applied to the transfer roller  17 . As a result, the toner images on the belt  18  are transferred together onto the sheet  14  by the bias. 
         [0046]    After the transfer of the toner images onto the sheet  14 , the sheet  14  is conveyed to the fixing apparatus  20 , in which the sheet  14  is subjected to heat and pressure to fix the toner images to the sheet  14 . After the fixation of the toner images, the sheet  14  is discharged into the delivery tray  24  by the pair of discharge rollers  22 . 
       (Structural Arrangement for Mounting or Dismounting Cartridge) 
       [0047]    Next, the structural arrangement for mounting the cartridges  3  into the main assembly  100 , or dismounting the cartridges  3  from the main assembly  100 , will be described. 
         [0048]    Referring to  FIGS. 1 and 2 , the front panel of the main assembly  100  is provided with a hole  100   b  (first hole of the main assembly  100 ). The front panel is provided with a door  28  (which can be opened or closed), which is attached to the front panel so that it can be rotationally moved about a shaft  28   a  attached to the bottom portion of the door  28  so that the door  28  can be opened to expose the hole  100   b,  or closed to cover the hole  100   b . The door  28  is attached to the front panel so that it can be rotationally moved to expose or cover the hole  100   b.  The hole  100   b  is the hole which the tray  26  passes when it is moved between its innermost position I and outermost position O. The door  28  is rotationally moved outward of the main assembly  100  about the shaft  28   a  attached to the bottom of the door  28  to expose or cover the hole  100   b.    
         [0049]    The main assembly  100  is provided with a cartridge space  100   a  in which the cartridges  3  are mounted. The cartridge space  100   a  is in the main assembly  100 . The main assembly  100  is also provided with a cartridge tray  26  (cartridge supporting member) which supports the cartridges  3 . The cartridge tray  26  is attached to the inward side of the cartridge space  100   a.  More specifically, the cartridge tray  26  is attached to the main assembly frame in such a manner that it is slidingly movable in the frontward or backward direction while being guided by a pair of rails  27 L and  27 R on the left and right internal walls, respectively, of the main assembly frame, which form the cartridge space  100   a.  Thus, the cartridge tray  26  is linearly movable between its innermost position I (relative to main assembly  100 ) and outermost position O (relative to main assembly  100 ) while holding the cartridges  3 . 
         [0050]    The outermost position O is the position (outlined by dotted line in  FIG. 1 ; position shown in  FIG. 2 ), which allows a user to mount the cartridge  3  into the tray  26 , or remove the cartridge  3  from the tray  26  (replace cartridges  3 ). That is, it is when the tray  26  is in its outermost position O that a user places the cartridges  3  in the tray  26  so that the cartridges  3  are supported by the tray  26 , or that a user removes the cartridge  3 . It is after the cartridge tray  26  is pulled out from its innermost position I (outlined by solid line in  FIG. 1 ) to its outermost position O when a user is to mount the cartridge  3  into the tray  26 , or to remove the cartridge  3  from the tray  26 . Then, as the user pushes the tray  26  into its innermost position I, the cartridges  3  are placed in their image forming positions R ( FIG. 1 ). 
         [0051]    The image forming position R is the position in which each cartridge  3  contributes to image formation. In this embodiment, the image forming position R is the position in which the drum  1  in the cartridge  3  is in contact with the belt  18 . Incidentally, when the cartridge  3  is in its image forming position R, the cartridge  3  does not need to remain supported by the tray  26 ; the cartridge  3  may be floating from the tray  26 . 
         [0052]    As a user pushes the tray  26  into the main assembly  100 , the cartridges  3  supported by (mounted into) the tray  26  in the outermost position O are moved into the innermost position I, and the cartridges  3  are accurately positioned in their image forming positions R. In this embodiment, as the door  28  is closed while the tray  26  is in its innermost position I, the tray  26  lowers, positioning thereby the cartridges  3  in their image forming positions R. On the other hand, as the door  28  is opened, the tray  26  moves upward, and the cartridge  3  move upward with the tray  26 . As a result, the photosensitive drum  1  separates from the transfer belt  18 . 
         [0053]    In the embodiment described above, the tray  26  horizontally moves relative to the surface (unshown) on which the main assembly  100  is placed. However, the direction in which the tray  26  is moved does not need to be limited to this direction. For example, it may be diagonally upward or downward in a straight line relative to the surface (unshown) which is supporting the main assembly  100 . That is, the tray  26  linearly moves in the direction perpendicular to the lengthwise direction of the cartridges  3  which the tray  26  supports. The lengthwise direction of the cartridge  3  is the direction parallel to the lengthwise direction of the photosensitive drum  1  or development roller  2 . 
         [0054]    The tray  26  is provided with multiple cartridge supporting portions  26   a  ( FIG. 2 ) which removably supports the multiple cartridges  3  ( 3 Y,  3 M,  3 C, and  3 K), one for one; one cartridge  3  fits in each supporting portion  26   a.  That is, four cartridges  3 Y,  3 M,  3 C, and  3 K are removably supported by (mounted in) the tray  26 . Referring to  FIG. 2 , the tray  26  is provided with a handle  26   b,  which is at the front end of the tray  26 . A user is to pull out the tray  26  from the main assembly  100 , or to push the tray  26  into the main assembly  100 , by grasping the handle  26   b.    
         [0055]    The procedure for mounting or dismounting the cartridges  3  ( 3 Y,  3 M,  3 C, and  3 K) is as follows. First, a user is to open the door  28 , and then, to grasp the handle  26   b.  As the handle  26   b  is grasped, a locking member  46 , which keeps the tray  26  locked to the main assembly  100 , is slid, being thereby made to release the tray  26 . Then, the user is to pull the tray  26  to a preset position (outermost position O), which is on the front side, by grasping the handle  26   b.  As a result, the cartridges  3  supported by the tray  26  are exposed from the main assembly  100 , allowing thereby the cartridges  3  to be removed upward. In other words, the cartridges  3  in the tray  26  can be easily replaced. That is, the tray  26  supports the cartridges  3 , so that the cartridges  3  can be slidingly moved relative to the main assembly  100 , making it easier to mount multiple cartridges  3  into the main assembly  100 , or remove them from the main assembly  100 . 
         [0056]    Incidentally, how far the tray  26  is pulled out of the main assembly  100  is regulated by the contact between a stopper (unshown), with which the main assembly  100  is provided, and a stopper (unshown), with which the tray  26  is provided. That is, the length by which the tray  26  is allowed to be pulled out of the main assembly  100  is regulated by this setup. Therefore, it does not occur that the tray  26  becomes disengaged from the main assembly  100 . 
         [0057]    After the tray  26  is pulled out and the cartridges  3  are mounted into the tray  26 , the tray  26  is to be slidingly pushed rearward (deeper end) of the apparatus  100  to be moved back into a preset position (innermost position I), until a projection (unshown), with which one end of the tray  26  is provided, comes into contact with a tray positioning portion (unshown) of the main assembly  100 . At this point, the user is to release the handle  26   b.  As the user release the handle  26   b,  the locking member  34  slides back into its locking position, locking thereby the tray  26  to the main assembly  100 . Then, the user is to close the door  28 . As the door  28  is closed, the driving force transmission coupling (unshown) of each of the cartridges  3  engages with the corresponding driving force transmission coupling (unshown) of the main assembly  100 , and each cartridge  3  is secured in its image forming position R. By the way, the main assembly  100  is what remains after the tray  26 , covers  4  and  5 , and door  28  are removed from the image forming apparatus  100 . 
       (Structural Arrangement for Opening or Closing Covers) 
       [0058]    The image forming apparatus  200  is provided with two covers, which can be opened or closed relative to the main assembly  100 . One is on the front side of the main assembly  100 , and the other is on the rear side of the main assembly  100 . 
         [0059]    More specifically, the front cover  5  (second cover) is at the top front corner of the main assembly  100 , and is on the top side of the door  28  ( FIG. 1 ). The cover  5  exposes or covers the cartridge exposing opening Y (second opening), which is for mounting the cartridge  3 Y (which is the most upstream cartridge in terms of the direction  300  ( FIG. 2 ) in which the tray  26  is pulled out of the main assembly  100 ) into the tray  26 , or removing the cartridge  3 Y from the tray  26 , when the tray  26  is the outermost position O. The opening Y is on the top side of the hole  100   b  (door  28 ), and is in connection to the hole  100   b.  The opening Y is for removing the cartridge  3  supported by the tray  26 , from the tray  26 , when the tray  26  is in its outermost position O. The opening Y is also for making the tray  26  support the cartridge  3 , when the tray  26  is in its outermost position O. That is, the opening Y is the opening through which the cartridge  3  is put through by a user when the user is mounting the cartridge  3  into the tray  26 , or dismounting the cartridge  3  from the tray  26 . 
         [0060]    Another role of the cover  5  is to prevent light from entering the main assembly  100  from outside the main assembly  100  when the cover  5  is in its closed position. That is, when the cover  5  is in its closed position, it prevents the ambient light from hitting the cartridges P in the main assembly  100 . The cover  5  is for exposing or covering the opening Y. That is, the cover  5  is for preventing the ambient light from entering the main assembly  100  when it is in its closed position (outlined by solid line in  FIG. 1 ). Thus, the cover  5  is made of a resinous material which does not transmit light. 
         [0061]    The rear cover  4  (third door), which is on the rear side of the main assembly  100 , is above a sheet passage S (sheet conveying rear passage) ( FIG. 1 ). That is, the cover  4  is a part of the top wall of the main assembly  100 . The sheet conveyance passage S is the sheet passage from the secondary transfer roller  17  to the pair of discharge rollers  22 . The cover  4  is structured so that it can at least partially expose or cover the bottom portion of the sheet conveyance passage opening X (third opening). A user can insert his or her hand, at least partially, into sheet conveyance passage S through the opening X. The cover  4  makes up a part of the delivery tray  24  when it is in its closed position. That is, as the cover  4  is closed, it is placed where it catches the sheet  14  as the sheet  14  is discharged. The opening X is in the top portion of the main assembly  100 . It is for removing the sheet  14  when the sheet  14  becomes stuck in the sheet conveyance passage S, which is positioned so that when the tray  26  is in its innermost position I, the sheet conveyance passage S is on the rear side of the tray  26 . That is, the opening X is the opening through which the sheet  14  can be pulled out of the main assembly  100  if the sheet  14  gets stuck in the sheet conveyance passage S. The cover  4  keeps the opening X covered in such a manner that if necessary, the opening X can be exposed. When the cover  4  is in its position (outlined by solid line in  FIG. 1 ) for keeping the opening X closed, it prevents the ambient light from entering the interior of the main assembly  100 . That is, the cover  4  prevents the ambient light from hitting the cartridges  3  in the main assembly  100 . Thus, the cover  4  is made of a resinous material which does not transmit light. 
         [0062]    The front cover  5  is opened by the movement of the tray  26 ; as the tray  26  is pulled out of the main assembly  100 , the front cover  5  is opened by the outward movement of the tray  26 , whereas as the tray  26  is pushed into the main assembly  100 , the cover  5  is closed by the inward movement of the tray  26 . 
         [0063]    As for the cover  4 , it is only when the sheet  14  is remaining stuck (jammed) in the sheet conveyance passage S that the cover  4  is opened by the movement of the tray  26  as the tray  26  is pulled out of the main assembly  100 ; normally, the covered  4  is not opened by the movement of the tray  26  even when the tray  26  is pulled out of the main assembly  100 . 
         [0064]      FIG. 2  is a sectional view of the image forming apparatus  200  when the tray  26  is in its outermost position O to which the tray  26  was pulled out to replace the cartridge(s)  3 . As the tray  26  is pulled out of the main assembly  100  and the cover  5  is opened to expose the opening Y, the cartridges  3  in the tray  26  are exposed ( FIG. 2 ). It should be noted here that the cover  5  is automatically opened by the outward movement of the tray  26 . Thus, as the tray  26  is pulled out to its outermost position O, all the cartridges  3 , including the cartridge  3 Y, are exposed from the main assembly  100 . In  FIG. 2 , the position in which the cover  5  is when the opening Y is remaining exposed is outlined by a solid line, and the position in which the cover  5  is when the opening Y is remaining covered is outlined by a dotted line. As the tray  26  is pulled out of the main assembly  100 , the cover  5  is slidingly moved both upward and rearward (deeper end of main assembly  100 ) by the movement of the tray  26  while remaining in the same attitude as it remains when it is in its closed position. The cover  5  slidingly moves between its position (outlined by solid line in  FIG. 1 ) for keeping the opening Y closed, and its open position (outlined by dotted line in  FIG. 1 ) for keeping the opening Y exposed, while remaining the same in attitude. The cover  5  never fails to be moved to its outward position by the movement of the tray  26  when the tray  26  is pulled out of the main assembly  100 . That is, as the tray  26  is pulled out of the main assembly  100 , the cover  5  always moves into its open position. 
         [0065]    More specifically, as the tray  26  is pulled out frontward from the main assembly  100  by a distance of L 1  ( FIG. 2 ), the four cartridges  3  are exposed from the main assembly  100 . Referring to  FIG. 2 , the distance L 1  is a distance which is just enough to pull three cartridges  3 M,  3 C, and  3 K out of the main assembly  100  in the frontward direction of the main assembly  100 . Thus, the cartridge  3 Y, which is at the deepest end of the main assembly  100  is exposed from the main assembly  100  by the above described movement of the cover  5  toward the rear end of the main assembly  100 . Therefore, a user can take the cartridge  3 Y out of the tray  26  simply by pulling the tray  26  out of the main assembly  100  by the distance L 1 . That is, this embodiment makes it possible to smoothly mount the cartridge  3 Y into the tray  26 , or dismount the cartridge  3 Y from the tray  26 , without pulling the tray  26  out of the main assembly  100  far enough to place the cartridge  3 Y beyond the hole  100   b.  In the case of this image forming apparatus  200 , the cartridge  3 Y is supported by the most upstream portion of the tray  26 , in terms of the direction  300  ( FIG. 2 ) in which the tray  26  is pulled out of its innermost position I to its outermost position O. Further, in terms of the vertical direction, the hole  100   b  is above the shaft  28   a.  These structural arrangements in this embodiment can reduce the amount of space required to operate the apparatus  200 . 
         [0066]    Referring to  FIG. 2 , as the tray  26  is pulled out of the main assembly  100 , the movement of the tray  26  causes the rear cover  4  to rotationally open rearward about a rotational shaft  30  which is at the bottom of the rear cover  4 . As a result, the top portion of the sheet conveyance passage S in the main assembly  100  becomes exposed, making it easier for a user to remove the jammed sheet  14  in the portion of the sheet conveyance passage S, which is between the secondary transfer portion (secondary transfer roller  17 ) and the fixing portion (fixing apparatus  20 ). 
         [0067]    The image forming apparatus  200  is not structured so that as the tray  26  is pulled out of the main assembly  100 , the cover  4  is always opened by the movement of the tray  26 . That is, the image forming apparatus  200  is structured so that it is only when there is a jammed sheet  14  in the sheet conveyance passage S that as the tray  26  is pulled out of the main assembly  100 , the cover  4  is opened by the outward movement of the tray  26 . 
         [0068]    Here, referring to  FIGS. 3-8 , the means (first and second means) for causing the movement of the tray  26  to open or close the covers  5  and  4  will be described. Shown in the drawings is only one side of the image forming apparatus  200  in terms of the left and right directions of the tray  26 . However, the other side of the image forming apparatus  200  is also provided with the means for causing the movement of the tray  26  to open or close the covers  5  and  4 , which is similar to the first means. 
         [0069]    Referring to  FIG. 3 , the rotational shaft  30  of the cover  4  is in connection with one end of an arm  8 . Further, one end of the cover  4  and one end of the arm  8  are solidly attached to the rotational shaft  30 . Thus, the rotational shaft  30 , cover  4 , and arm  8  rotate together. The rotational shaft  30  is fitted with a torsional coil spring  31  (elastic member). One end of the torsional coil spring  31  is attached to a preset portion of the main assembly  100 , and the other end is attached to the arm  8 . Thus, the arm  8  is under the pressure generated by the resiliency of the spring  31  in the counterclockwise direction  600  ( FIG. 3 ). Therefore, when the tray  26  is in its innermost position I, the arm  8  remains engaged with a projection  6 , with which the rear end of the tray  26  is provided. 
         [0070]    Next, referring to  FIG. 4 , the cover  5  is provided with two shafts  32  and  33 . The cover  5  has a horizontal portion  5   a  and a vertical portion  5   b.  The horizontal portion  5   a  prevents the ambient light from entering the main assembly  100  from the top side of the main assembly  100 . The vertical portion  5   b  prevents the ambient light from entering the main assembly  100  from diagonally above the main assembly  100 . One end of the shaft  32  is fitted in one of the cover linkage  34 . The other end of the linkage  34  is attached to a rotational shaft  36  that it can be rotated about the rotational shaft  36 . Thus, the rotational shaft  36 , an arm  9 , and linkage  34  rotate together. 
         [0071]    Further, the rotational shaft  36  is fitted with a coil spring  38  (elastic member), one end of which is attached to a predetermined portion of the main assembly  100 , and the other end of which is attached to the arm  9 . With the provision of this structural arrangement, the arm  9  is kept pressured in the counterclockwise direction  600  ( FIG. 4 ) by the resiliency of the spring  38 . Further, when the tray  26  is in its innermost position I, the arm  9  is in connection with a projection  7 , with which the front side of the tray  26  is provided. 
         [0072]    Further, the main assembly  100  is provided with a guiding plate  55 , which is provided with an arcuate guiding groove  55   a,  in which the shaft  33  of the cover  5  is fitted, being enabled to slidingly move in the groove  55   a.    
         [0073]    There is a flapper  35  above the cover  5  (horizontal portion  5   a ). The flapper  35  is attached to the top cover  37  in such a manner that it is rotatable about the shaft  35   a,  which is fitted with a torsional coil spring  29  (elastic member). Thus, the flapper  35  is kept pressed in the counterclockwise direction ( FIG. 40 ) by the resiliency of the coil spring  29 . One end of the flapper  35  is in contact with one end of the cover  5 . The flapper  35  prevents the ambient light from entering the main assembly  100  through the gap between the top cover  37  and cover  5  (horizontal portion  5   a ). 
       (Opening and Closing of Covers) 
       [0074]    Next, the sliding movement of the tray  26 , opening of the cover  4 , and opening and closing of the cover  5  will be described. 
         [0075]    The image forming apparatus  200  is structured so that if the tray  26  is pulled out when the sheet conveyance passage S is remaining jammed with the sheet  14 , the cover  4  is opened by the outward movement of the tray  26 . Thus, referring to  FIGS. 5 and 8 , this structural arrangement will be described. Normally, the cover  4  is not opened by the outward movement of the tray  26 ; it remains closed. The main assembly  100  is provided with a solenoid  700  having a lever  47 . The lever  47  is in connection with the arm  8 . There is a sensor  400  positioned along the sheet conveyance passage S. 
         [0076]    If a jam occurs, a jam occurrence signal is transmitted from the sensor  400  to a control portion  500 , which controls the entirety of the apparatus  200 . Receiving the jam occurrence signal, the control portion  500  rotationally moves the lever  47  by driving the solenoid  700 . This rotational movement of the lever  47  disengages the lever  47  from the arm  8 , allowing thereby the arm  8  to be rotationally moved in the counterclockwise direction by the resiliency of the spring  31 . As a result, the arm  8  comes into contact with the projection  6 , with which the tray  26  is provided as described before. If a user pulls out the tray  26  when the apparatus  200  is in the above described condition, the arm  8  rotates, opening thereby the cover  4 . The opening of the cover  4  exposes the opening X, making it possible to take care of the jam (to remove the jammed sheet). 
         [0077]    On the other hand, when there is no jammed sheet in the sheet conveyance passage S, the arm remains engaged with the lever  47  of the solenoid  700 . Thus, even if the tray  26  is pulled out of the main assembly  100 , the cover  4  does not open; it remains closed. 
         [0078]    As soon as the jammed sheet is removed, the driving of the solenoid  700  is stopped, and therefore, the arm  8  comes into contact with the lever  47 , preventing thereby the arm  8  from being moved by the movement of the tray  26 . The ending of the process of taking care of the jam is detected by a sensor (unshown) which detects the closing of the door  28  or cover  4 , for example. This information regarding the ending of the process of taking care of the jam is received by the control portion  500 . Then, the control portion  500  stops the driving of the solenoid  700  based on this information. 
       (Opening Operation) 
       [0079]    If it is necessary again to replace the cartridge(s)  3  or to take care of the jamming of the sheet  14 , a user has to open the door  28  ( FIG. 2 ), first. Then, the user is to pull the tray  26  out of the main assembly  100  by grasping the handle  26   b.  The outward movement of the tray  26  frees the projection  7 , which was preventing the cover  5  from rotationally moving. Consequently, the arm  9  is rotated about the shaft  36  by the resiliency of the spring  38 , causing thereby the cover  5  to open. That is, this embodiment of the present invention makes it possible for the opening Y to be exposed by the outward movement of the tray  26 . The area outlined by a dotted line in  FIG. 2  is where the cover  5  is when it is open. 
         [0080]      FIG. 5  is a perspective view of the cover  4  when the cover  4  is open. If the sheet conveyance passage S is jammed with the sheet  14  while the tray  26  is in the position which keeps the cartridges  3  in their image forming positions R, the arm  8  is disengaged from the lever  47  by the above described operation. Then, the disengaged arm  8  comes into contact with the projection  6 . Therefore, as the tray  26  is pulled out of the main assembly  100 , the arm  8  is rotationally moved by the resiliency of the spring  31  until it is stopped by its contact with an arm stopper  39 , with which the top cover  37  ( FIG. 3 ) is provided. Consequently, the cover  4  is kept open by the resiliency of the spring  31 . As the cover  4  is opened, the opening X becomes exposed. 
         [0081]    The exposure of the opening X exposes the top portion of the sheet conveyance passage S, making it possible for a user to access the sheet conveyance passage S from the front side of the main assembly  100 . Therefore, the user can easily remove the jammed sheet  14  in the sheet conveyance passage S. 
         [0082]      FIG. 6  is a sectional view of the portion of the apparatus  200 , which concerns this embodiment of the present invention, when the cover  5  is open. As the tray  26  is pulled out of the main assembly  100 , the outward movement of the tray  26  causes the arm  9  to disengage from the projection  7 . Consequently, the arm  9  is rotationally moved in the counterclockwise direction by being pressed by the resiliency of the spring  38 , until it comes into contact with an arm catcher  40  on the main assembly  100 , which stops the rotational movement of the arm  9 . While the arm  9  is rotationally moved, the door linkage  34  is rotationally moved with the arm  9 . 
         [0083]    The rotational movement of the door linkage  34  causes the shaft  32 , which is in connection with the door linkage  34 , to arcuately move as indicated by an arrow mark  80  ( FIG. 6 ). During this movement of the shaft  33 , the shaft  33 , with which the cover  5  is provided, arcuately moves by being guided by the guiding groove  55   a.  Thus, the cover  5  slidingly moves in both upward and rearward (toward rear end of main assembly) while remaining in the same attitude as that in which it is when it is remaining closed. That is, the cover  5  slidingly moves with its horizontal portion  5   a  remaining horizontal. This sliding movement of the cover  5  exposes the opening Y. In other words, this embodiment of the present invention makes the cover  5  slidingly move into the area below the delivery tray  24  while keeping the cover  5  in the same attitude as that in which the cover  5  is when it is remaining closed; the cover  5  retreats from the area above the cartridge  3 Y. Therefore, it does not occur that the cover  5  interferes with the mounting of cartridge  3 Y into the tray  26 , or the removal of the cartridge  3 Y from the tray  26 . 
         [0084]    In this embodiment, the cover  5  slidingly moves while maintaining the same attitude as the attitude it has when it is remaining closed. Then, it enters the space below the delivery tray  24 , as described above. Therefore, even though the cover  5  is moved into its open position each time the tray  26  is pulled out of the main assembly  100 , the movement of the cover  5  is not conspicuous. In addition, in a case where the tray  26  is pulled out of the main assembly  100 , it is likely for the cartridge(s) to be replaced. Thus, structuring the apparatus  200  so that the cover  5  is opened by the outward movement of the tray  26  improves the apparatus  200  in cartridge replacement efficiency. 
         [0085]    Further, when the cartridge  3 C, for example, in the apparatus  200  in this embodiment is replaced, the tray  26  has to be pulled out of the main assembly  100  only by the distance which is large enough to place the cartridge  3 C below the opening Y. In other words, this embodiment makes it possible to reduce the distance by which the tray  26  has to be pulled out to replace the cartridges  3 , making it possible to improve the apparatus  200  in the efficiency with which the cartridges  3  can be replaced. As the tray  26  is pulled out from its innermost position I to its outermost position O, the cover  5  is moved to its open position by the outward movement of the tray  26 , as described above. The cover moving first means, that is, the means for moving the cover  5 , to its open position has the projection  7 , arm  9 , shafts  32  and  33 , door linkage  34 , rotational shaft  36 , spring  38 , guiding plate  55 , and guiding groove  55   a.  By the way, the structure of the means for moving the cover  5  does not need to be limited to the above described one. This subject will be described again later. 
         [0086]    Further, as the cover  5  is moved, the flapper  35  rotationally moves by being pushed by the end portion of the cover  5 . 
         [0087]    The apparatus  200  in this embodiment is structured so that the cover  5  is opened through the above described steps. Therefore, it can provide an ample space for mounting or removing the cartridge(s)  3  even though the apparatus  200  is significantly smaller than any of conventional apparatus, in terms of the distance by which the tray  26  has to be pulled out to replace the cartridges  3 . In other words, this embodiment of the present invention can reduce the space which the main assembly  100  occupies, without sacrificing the operability of the apparatus  200  in terms of the mounting or removal of the cartridges  3 . 
       (Closing Operation) 
       [0088]    Next, referring to  FIG. 7 , the movement of the cover  5 , which occurs when the tray  26  is moved into the main assembly  100 , will be described. 
         [0089]    Referring to  FIG. 7 , the tip portion of the arm  9  is provided with a projection  41 . A predetermined portion of the tray  26  is provided with a guide  42 , which is enabled to engage with the projection  41 . The guide  42  has a slanted surface by which the guide  42  engages with the projection  41 . As a user pushes the tray  26  into the main assembly  100 , the tip  42   b  of the guide  42  comes into contact with the projection  41 . Then, as the tray  26  is pushed further inward, the arm  9  rotates in the clockwise direction (indicated by arrow mark  90  in  FIG. 7 ) about the shaft  36 , against the resiliency of the spring  38 , while being guided by the guiding surface  42   a  of the guide  42 . As the arm  9  rotationally moves, the door linkage  34  is rotationally moved by the movement of the arm  9 . Thus, the shaft  32 , which is in connection with the door linkage  34 , arcuately moves as indicated by an arrow mark  100  ( FIG. 7 ). As the shaft  32  arcuately moves, the shaft  33 , with which the cover  5  is provided, is guided by the guiding groove  55   a,  being therefore arcuately moved. Thus, the cover  5  slidingly moves both downward and frontward (frontward of main assembly), while remaining in the same attitude as the attitude in which it is when it is open. In other words, the cover  5  is closed by the movement of the tray  26 , which occurs when the tray  26  is pushed into the main assembly  100 . Here, the means for closing the cover  5  by using the movement of the tray  26 , which occurs when the tray  26  is pushed into the main assembly  100 , is made up of the arm  9 , projection  41 , guide  42 , door linkage  34 , guiding groove  55   a,  and shaft  33 . 
         [0090]    Next, referring to  FIG. 5 , the movement of the rear cover  4 , which occurs when the tray  26  is moved back into the main assembly  100 , will be described. 
         [0091]    The cover  4  is the cover for taking care of the sheet conveyance passage jam caused by the sheet  14 . In order to take care of this problem, it is necessary for a user to put his or her hand through the opening X. Thus, the apparatus  200  is provided with a movement regulating member, which prevents the problem that the tray  26  unexpectedly moves to its inward position when the cover  4  is not closed. The operation for taking care of jam means the operation for removing the jammed sheet  14  in the sheet conveyance passage S. 
         [0092]    Referring to  FIG. 5 , the lengthwise center portion of the arm  8  is provided with a projection  44 , whereas the rear end portion of the tray  26  is provided with an arm movement controlling portion  45  (regulating member on main assembly side), which is enabled to engage with the projection  44 . The arm movement controlling portion  45  is a part of the tray  26 , and projects upward from the tray  26 . If a user happens to attempt to push the tray  26  inward of the main assembly  100  without closing the cover  4 , the arm movement controlling portion  45  comes into contact with the projection  44 , preventing thereby the tray  26  from being pushed into the main assembly  100  when the cover  4  is open. That is, the projection  44  (tray movement regulating member on main assembly side) and the tray movement controlling portion  45  (tray movement regulating portion on supporting member side) are the portions for preventing the tray  26  in its outermost position O from being moved to its innermost position I when the cover  4  is open. 
         [0093]    The surface  45   a  of the tray movement controlling portion  45 , which comes into contact with the projection  45 , arcuately protrudes in such a manner that when the cover  4  is open, the point of contact between the tray movement controlling portion  45  and projection  44  coincides with the axis of the rotational shaft  30  of the arm  8 . Therefore, if an attempt is made to push the tray  26  into the main assembly  100  when the cover  4  is open, the tray movement controlling portion  45  comes into contact with the projection  44 , being prevented from rotationally moving the arm  8 ; even if a greater amount of force is applied to the tray  26  to push the tray  26  into the main assembly  100 , the force does not act in the direction to rotationally move the arm  8 . Therefore, the tray  26  cannot be pushed further into the main assembly  100  to be stored in the main assembly  100 . The image forming apparatus  200  in this embodiment has a second means for moving the cover  4  to its open position. More specifically, if the tray  26  is pulled out of its innermost position I to its outermost position O after the sensor  400  detected that the sheet conveyance passage S became jammed with the sheet  14 , the second means for moving the cover  4  is made, by the movement of the tray  26 , to move the cover  4  to its open position. The second means for moving the cover  4  is made up of the arm  8 , rotational shaft  30 , spring  31 , arm stopper  39 , projection  44 . By the way, the structure of the second means for moving the cover  4  does not need to be limited to the above described one. The means may be structures as will be described later. 
         [0094]    The apparatus  200  in this embodiment is structured so that unless a user manually closes the cover  4 , the tray  26  cannot be moved back into the main assembly  100 , preventing thereby a user from forgetting to take care of the jam. That is, the present invention improves an electrophotographic image forming apparatus in usability. 
         [0095]    The cover  4  is always kept pressed by the resiliency of the spring  31  (elastic member) in the direction to be opened. Therefore, if the cover  4  is closed without moving the tray  26  back into the main assembly  100 , the cover  4  automatically opens again. Thus, the apparatus  200  in this embodiment is provided with a locking means for temporarily keeping the cover  4  in its locked position if the cover  4  is manually closed while the tray  26  is remaining outside the main assembly  100 . 
         [0096]    Referring to  FIG. 8 , the mechanism for temporarily locking the cover  4  is structured so that moving the cover  4  into its closed position in the main assembly  100  enables a user to slide the lever  47 , which can be engaged with the arm  8 , in the direction indicated by the arrow mark. The lever  47  is kept pressed by the resiliency of the compression spring  46  (elastic member) toward the arm  8 . Further, the lever  47  has a tilted and tapered surface  47   a  which faces the arm  8 . 
         [0097]    If a user closes the cover  4  when the tray  26  is outside the main assembly  100 , the arm  8  comes into contact with the slanted surface  47   a.  Then, as the user pushes the cover  4  further toward its closed position, the arm  8  pushes away the lever  47  against the resiliency of the spring  46 . As the user moves the cover  4  in its closing direction by a preset amount, the arm  8  passes by the slanted surface  47   a,  allowing thereby the lever  47  to be pushed back into its initial position by the resiliency of the spring  46 . Consequently, the arm  8  is locked by the lever  47 , and therefore, the rear cover  4  is kept in its closed position. 
         [0098]    As a user manually closes the cover  4 , the contact between the projection  44  and tray movement controlling portion  45  disappears, making it possible for the tray  26  to be put back into the main assembly  100 . 
         [0099]    Referring to  FIG. 5 , the projection  6 , which projects from the rear portion of the tray  26  has a tapered and slanted surface. Thus, as the tray  26  is moved inward of the main assembly  100  when it is outside the main assembly  100 , the projection  6  comes into contact with the slanted surface  47   a  of the lever  47 . Then, as the tray  26  is moved further inward of the main assembly  100 , the projection  6  pushes away the lever  47  against the resiliency of the spring  46 , and comes into contact with the arm  8 . Consequently, the temporarily locked cover  4  is unlocked. 
         [0100]    Even after the unlocking of the temporarily locked cover  4 , the arm  8  remains controlled by the projection  6 . Therefore, as the tray  26  is pulled out of the main assembly  100 , the cover  4  is opened by the outward movement of the tray  26 . 
         [0101]    That is, in the case of the image forming apparatus  200  in this embodiment, as the tray  26  is pulled out of the main assembly  100 , both the rear cover  4  and front cover  5  are opened by the movement of the tray  26 , as described above. That is, the tray  26  opens the covers  4  and  5  as it is pulled out of the main assembly  100 . Further, the tray  26  closes the cover  5  as it is pushed into the main assembly  100 . By the way, the image forming apparatus  200  in this embodiment is not structured so that as the tray  26  is pushed into the main assembly  100 , the cover  4  is closed by the movement of the tray  26 . That is, the cover  4  has to be manually closed by a user. In addition, unless the cover  4  is in its closed position, the tray  26  cannot be pushed into the main assembly  100 . This set up prevents the user from pushing the tray  26  into the main assembly  100  before the user removes the jammed sheet in the sheet conveyance passage S. Further, in the case of the image forming apparatus  200  in this embodiment, the operation for replenishing the main assembly  100  with the sheets  14 , the operation for replacing the cartridge(s)  3 , the operation for removing the jammed sheet  14 , and the like operations, which are to be carried out by a user, can all be carried out from the front side of the main assembly  100 . In other words, the present invention could improve an electrophotographic image forming apparatus in usability. 
         [0102]    Further, the main assembly  100  is provided with the cover  5 , which is on the front side of the main assembly  100  and is opened or closed by the movement of the tray  26 . The provision of this cover  5  made it possible to reduce the distance by which the tray  26  has to be pulled out to replace the cartridge  3 , without reducing the apparatus  200  in terms of the efficiency with which the cartridge  3  can be replaced. In other words, the present invention made it possible to reduce in size the space in which the main assembly  100  is to be set up for image formation. 
         [0103]    Further, the apparatus  200  is structured so that when the cover  4  is open, the tray  26  cannot be moved back into the main assembly  100 . Therefore, it is easy to take care of the sheet jam in the main assembly  100 . 
         [0104]    Further, in this embodiment, the contact between the projection  44  of the tray  26 , and the arm  8 , is used as the structural arrangement for causing the rear cover  4  to be opened by the movement of the tray  26  when the tray  26  is pulled out of the main assembly  100 . Further, the contact is also used as the structural arrangement for causing the front cover  5  to open or closed by the movement of the tray  26  when the tray  26  is pulled out of, or pushed into, the main assembly  100 . The structural arrangement for the means (first and second means) for moving the doors  5  and  4  with the use of the movement of the tray  26  does not need to be limited to the above described one. For example, the means may be made up of a partially toothed gear, and a pinion rack gear. However, the above described structural arrangement is simpler, and smoother in operation. 
       Embodiment 2  
       [0105]    Next, referring to  FIGS. 9 and 10 , the image forming apparatus in the second preferred embodiment of the present invention will be described. The apparatus in this embodiment is the same in basic structure as the apparatus in the preceding embodiment described above. Therefore, the portions of the description of this embodiment, which are the same as those of the counterparts in the preceding embodiment, will not be given here to avoid repetitions. In other words, only the structural features of the image forming apparatus in this embodiment, which characterize this embodiment, will be described. The portions of the image forming apparatus in this embodiment, which are the same in function as the counterparts in the first preferred embodiment, will be given the same referential codes as those given to the counterparts. 
         [0106]    In the first preferred embodiment, toner images (developer images) were transferred (secondary transfer) onto a sheet of recording medium (sheet  14 ) with the use of the intermediary transfer belt. In this embodiment, however, a sheet of recording medium is conveyed with the use of a transfer medium conveyance belt, and toner images are directly transferred onto the sheet of recording medium on the belt, from the photosensitive drum  1 . 
         [0107]      FIG. 9  is a schematic vertical sectional view of the image forming apparatus  200  in the second preferred embodiment of the present invention. After being fed into the main assembly  100  by a pair of sheet feeder rollers  5   a  and  5   b,  the sheet  14  is guided by a guide  48  to an adhesion roller  49  and a transfer medium conveyer belt  50 . The belt  50  conveys the sheet  14  by being circularly moved by a driving roller  16  in the counterclockwise direction of the drawing. After the formation of toner images on the photosensitive drums  1 , the toner images are transferred onto the sheet  14  on the belt  50 . 
         [0108]    After the transfer of the toner images onto the sheet  14 , the sheet  14  is sent to a fixing apparatus  20 , in which the toner images on the sheet  14  are fixed to the sheet  14  by being subjected to head and pressure. Consequently, a permanent full-color toner image is effected on the sheet  14 . After the fixation of the toner images, the sheet  14  is discharged into a delivery tray  24  by a pair of discharge rollers  22 . 
         [0109]      FIG. 10  is a schematic sectional view of the image forming apparatus in this preferred embodiment when the tray  26  is in its outward position to take care of a paper jam. In the case of the image forming apparatus in this embodiment, which is structured to use the belt  50 , the sheet  14  is conveyed through the main assembly  100  by the belt  50 . Therefore, it is sometimes necessary to take care of a sheet  51  ( FIG. 10 ), that is, a sheet  14  which has stuck to the surface of the belt  50 . 
         [0110]    As the tray  26  is pulled out of the main assembly  100 , the rear cover  4  and front cover  5  are opened by the movement of the tray  26  by a mechanical linkage, such as the one in the first preferred embodiment described above, which connects the tray  26  to the front door  4  and rear door  5 . 
         [0111]    Also in this embodiment, pulling the tray  26  out of the main assembly  100  by a distance of L 1  makes it possible to mount or remove the cartridge  3 , and also, to take care of the recording medium Jam which has occurred in the rear portion the main assembly  100  (rear portion of the sheet conveyance passage S), as it does in the first preferred embodiment. 
         [0112]    In the case of the image forming apparatus in this embodiment, the sheet of recording medium, which has stuck to the belt  50 , has to be taken care of. Therefore, the tray  26  has to be pulled out by a distance of L 4  ( FIG. 10 ), which is greater than the distance L 1  ( FIG. 2 ) mentioned in the first preferred embodiment, so that the opening Y, which is large enough for the belt  50  to be accessed, can be created. 
         [0113]    In this embodiment, the opening Y is created by opening the front cover  5  which keeps the tray  26  and sheet conveyance passage S covered. A sheet conveyance passage S 1  (bottom portion) is the sheet conveyance passage, through which the sheet  14  is conveyed by the circularly movement of the belt  50 . Therefore, the sheet  51  which has stuck to the top portion of the belt  50  loop can be removed by an operator through the opening Y and space  100   a  of the main assembly  100 . That is, the present invention can reduce the distance L 4  by which the tray  26  has to be pulled out to take care of the jammed sheet  14 , without negative effects upon the easiness with which the jammed sheet  14  can be taken care of. 
         [0114]    In this preferred embodiment, the main assembly  100  has the sheet conveying passage S 1  under the innermost position I for the tray  26 . The opening Y (second opening) is for taking the cartridge  3  supported by the tray  26 , out of the tray  26 , and for placing the cartridge  3  in the tray  26  to support the cartridge  3  by the tray  26 . It is also for removing the sheet  51  (jammed sheet  14 ) in the sheet conveyance passage S 1 . 
         [0115]    This embodiment makes it possible for a user to remove the jammed sheet  51  by putting his or her hand in the main assembly  100 . Further, it makes it possible for a user to mount the cartridge  3 Y into, removed from, the most upstream cartridge space of the tray  26  through the opening Y, when the tray  26  is in its outermost position O. That is, this embodiment makes it possible to use the opening Y for both purposes described above. Incidentally, the position of the tray  26 , which is shown in  FIG. 10 , is the outermost tray position to which the tray  26  was pulled out to make it possible for the jammed sheet  51  to be removed through the opening Y. However, if the tray  26  is to be pulled out of the main assembly  100  just for mounting the cartridge  3  into the tray  26 , or removing the cartridge  3  from the tray  26 , the tray  26  does not need to be pulled out to the position shown in  FIG. 10 . In other words, normally, the tray  26  is unlikely to pulled out as far as the position shown in  FIG. 10 . 
         [0116]    In each of the preferred embodiments described above, the front cover  5  (first cover) is made to expose or cover the opening Y (second opening), by the movement of the tray  26  (cartridge supporting member). Therefore, the cartridges  3  are exposed even though the distance by which the tray  26  in this embodiment is pulled out is not as large as the distance by which the tray  26  of a conventional electrophotographic image forming apparatus has to be pulled out to expose its cartridges. That is, the present invention makes it possible to replace the cartridges  3  even though the distance (length) by which the tray  26  is pulled out of the main assembly  100  is less than the full length of the tray  26 . In other words, the present invention can make it possible to easily mount or remove the cartridges  3 , while reducing the amount of space necessary to set up the apparatus  200  for operation. 
         [0117]    Further, the front cover  5  is made to expose or close the opening Y, by the movement of the tray  26 . Thus, even though the distance by which the tray  26  has to be moved to mount or remove the cartridges  3  is significantly less than the distance by which the tray ( 26 ) of a conventional image forming apparatus has to be moved for the mounting or removal of the cartridges  3 , the tray  26  is fully exposed for the cartridges  3  to be easily replaced. In other words, the present invention makes it easier to mount or remove the cartridges  3  while reducing the mount of space necessary to set up the apparatus  200  for operation. 
         [0118]    Further, the present invention can make it easier to mount or remove the cartridges  3  while reducing the amount of operational space necessary for the main assembly  100 . Also, the present invention makes it easier to remove the stuck recording medium in the main assembly  100  while reducing the amount of operational space necessary for the main assembly  100 . Further, the present invention can make it possible to open the covers  4  and  5  with the use of the movement of the tray  26 . Further, each of the preferred embodiments of the present invention described above makes it possible to easily remove the jammed sheet  14  in the sheet conveyance passage S which is in the rear side of the innermost position I of the tray  26 . Further, the present invention makes it possible to easily remove the sheet  51  (recording medium) stuck in the sheet conveyance passage S 1  which is under the innermost position I of the tray  26 . 
         [0119]    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. 
         [0120]    This application claims priority from Japanese Patent Applications Nos. 249592/2008 and 212997/2009 filed Sep. 29, 2008 and Sep. 15, 2009, respectively, which are hereby incorporated by reference.