Abstract:
An image forming apparatus includes a belt unit capable of being inserted into and pulled out of the apparatus, the belt unit including a movable endless belt, a supporting frame supporting the endless belt and having an accommodating portion, a grip member which is provided on the supporting frame at a position outside the belt in a widthwise direction of the belt crossing with a moving direction of the belt and which is movable between a first position in which the grip member is projected out of the accommodating portion in a direction crossing with the widthwise direction and a second position in which the grip member is accommodated in the accommodating portion, and an urging member configured to urge the grip member in a direction from the second position toward the first position.

Description:
FIELD OF THE INVENTION AND RELATED ART 
       [0001]    The present invention relates to an image forming apparatus, such as a copying machine, a facsimile machine, and a printer, which is equipped with an endless belt, an endless belt unit, or the like. 
         [0002]    In recent years, an image forming apparatus, such as a copying machine or a printer, which uses an electrophotographic image forming method, has been substantially increased in operational speed. With the increase in operational speed, an image forming apparatus which has multiple image forming sections, and is structured so that the multiple image forming sections oppose an endless belt and simultaneously carry out their image formation processes, which are different in image color, has become the mainstream apparatus. One of the representative examples of such an image forming apparatus is a full-color image forming apparatus which employs an intermediary transfer belt. In the case of an image forming apparatus which employs an intermediary transfer belt, multiple toner images, different in color, are sequentially transferred in layers onto the intermediary transfer belt (primary transfer) to effect a full-color toner image on the intermediary transfer belt, and then, the multiple toner images, different in color, of which the full-color toner image is made up, are transferred together onto recording medium (secondary transfer). 
         [0003]    Also in the case of an image forming apparatus, such as the one described above, which employs an intermediary transfer belt, if its intermediary transfer belt is shorter in the length of service life than the main assembly of the image forming apparatus, it has to be periodically replaced. Generally speaking, an operation for replacing the intermediary transfer belt in an image forming apparatus is carried out after the intermediary transfer belt unit which contains the intermediary transfer belt is moved out of the main assembly of the image forming apparatus. An example of a widely used method for replacing the intermediary transfer belt unit is such a method that the intermediary transfer belt unit is pulled out of the main assembly of the image forming apparatus through one of the lateral walls of the main assembly, in the direction perpendicular to the lateral wall, and then, a replacement intermediary transfer belt unit (possibly new) is inserted into the main assembly. 
         [0004]    Generally speaking, in the case of the intermediary transfer belt unit used by the above-described method, it is provided with a pair of handles to make it easier to be lifted by an operator. For example, in the case of the intermediary transfer belt unit proposed in Japanese Laid-open Patent Application 2011-191459, its handle is above the intermediary transfer belt  33   b  suspended and kept tensioned by multiple rollers. In terms of the width direction of the intermediary transfer belt, it is centrally located. The handle of this intermediary transfer belt unit is made up of a pair of curved and protrusive linkage portions, and a handgrip portion which bridges between the pair of linkage portions. 
         [0005]    By the way, in the case of the intermediary transfer belt unit disclosed in Japanese Laid-open Patent application 2011-191459, the handle is above the intermediary transfer belt. Therefore, a storage space for the handle is necessary above the unit. Therefore, the unit is increased in height by the components for the handle storage space. 
         [0006]    Therefore, in the case of an image forming apparatus which employs a conventional intermediary transfer belt unit, it is necessary to secure a relatively large space for storing a tall intermediary transfer unit, which is problematic in that securing the large space makes it necessary to increase the main assembly of the image forming apparatus in height. 
       SUMMARY OF THE INVENTION 
       [0007]    According to an aspect of the present invention, there is provided an image forming apparatus comprising a main assembly; a belt unit capable of being inserted into and pulled out of said main assembly, said belt unit including a movable endless belt, a supporting frame supporting said endless belt and having an accommodating portion, a grip member which is provided on said supporting frame at a position outside said belt in a widthwise direction of said belt crossing with a moving direction of said belt and which is movable between a first position in which said grip member is projected out of said accommodating portion in a direction crossing with the widthwise direction and a second position in which said grip member is accommodated in said accommodating portion, and an urging member configured to urge said grip member in a direction from the second position toward the first position; an image forming unit provided in said main assembly configured to form an image on said belt; a guiding rail provided in said main assembly and configured to guide said belt unit when said belt unit is inserted into said main assembly; and a contact member provided in said main assembly and configured to be contacted by said grip member to move said grip member from the first position to the second position in midstream of the insertion of said belt unit into said main assembly while being guided by said guiding rail and configured to be disengaged from said grip member to permit said grip member to move from the second position to the first position by an urging force of said urging member in the midstream of the pulling-out of said belt unit while being guided by said guiding rail. 
         [0008]    Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a sectional view of a typical image forming apparatus of the intermediary transfer type, which is compatible with the present invention. 
           [0010]    In  FIG. 2 , part(a) is a sectional view of the image forming apparatus in the first embodiment of the present invention when the door of the apparatus is open, and part (b) is a schematic sectional view of the image forming apparatus as seen from the direction indicated by an arrow mark A. 
           [0011]      FIG. 3  is a perspective view of the entirety of the intermediary transfer belt unit in the first embodiment. 
           [0012]    In  FIG. 4 , part(a) is an enlarged perspective view of the intermediary transfer belt unit conveyance handle, and its adjacencies, in the first embodiment, when the handle is entirely protruding, and part (b) is an enlarged plan view of the intermediary transfer belt unit conveyance handle, and its adjacencies, when the handle is entirely in the intermediary transfer belt unit. 
           [0013]    In  FIG. 5 , parts (a) and (c) are sectional views of the intermediary transfer belt unit, which show the steps through which the intermediary transfer belt unit is inserted into the main assembly of the image forming apparatus. 
           [0014]    In  FIG. 6 , parts (a) and (b) are sectional views of the intermediary transfer belt unit, which show the steps through which the intermediary transfer belt unit is inserted into the main assembly of the image forming apparatus. 
           [0015]    In  FIG. 7 , parts (a)-(c) are sectional views of the intermediary transfer belt unit, which show the steps through which the intermediary transfer belt unit is pulled out of the main assembly of the image forming apparatus. 
           [0016]    In  FIG. 8 , parts (a) and (b) are sectional views of the intermediary transfer belt unit, which show the steps through which the intermediary transfer belt unit is pulled out of the main assembly of the image forming apparatus. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0017]    Hereinafter, embodiments of a belt device in accordance with the present invention, and embodiments of an image forming apparatus equipped with a belt device in accordance with the present invention, are described with reference to appended drawings. By the way, if a component in a drawing has the same referential code as a component in another drawing, the two components are the same, or similar to each other. 
         [0018]    The following embodiments of the present invention are related to cases in which the present invention was applied to a belt device  102  having an intermediary transfer belt unit  103  as a belt unit. However, these embodiments are not intended to limit the present invention in scope. That is, not only is the present invention applicable to the belt device  102 , but also, other belt devices which are removably installable in the main assembly of an image forming apparatus. More specifically, the present invention is applicable to any belt device which is structured so that its endless belt for conveying sheets of recording medium is circularly moved, and is removably installable in the main assembly of an image forming apparatus. 
         [0019]    First, referring to  FIGS. 1 and 2 , the image forming apparatus  101  in the following embodiment of the present invention is described. There are various image forming methods, for example, an electrophotographic method, an offset printing method, an inkjet method, etc., which can be employed by an image forming apparatus. However, the image forming apparatus  100  shown in  FIGS. 1 and 2  is a full-color image forming apparatus which uses an electrophotographic method.  FIG. 1  is a sectional view of the image forming apparatus  101  when the door of the apparatus is closed. In  FIG. 2 , part (a) is a sectional view of the image forming apparatus  101  when the door of the apparatus is open. In  FIG. 2 , part (b) is a schematic sectional view the image forming apparatus  101  as seen from the direction indicated by the arrow mark A. 
         [0020]    This image forming apparatus  101  is of the so-called intermediary transfer type, and also, of the so-called tandem type. More specifically, it has: four image forming sections, which are different in the color of the images they form; and an intermediary transfer belt  1 , which is a circularly movable endless belt. It is structured so that the four image forming sections are arranged in tandem, and in contact with the top side of the intermediary transfer belt  1 . This type of image forming apparatus is capable of forming an image on cardstock, and also, is excellent in productivity. Therefore, it has become the main stream image forming apparatus in recent years. 
       [Recording Medium Conveyance Process] 
       [0021]    Referring to  FIG. 1 , the image forming apparatus  101  has a main assembly  101   a  (which hereafter will be referred to simply as “apparatus main assembly”). The right end of the apparatus main assembly  101   a  is provided with a door  31  which is opened or closed to remove jammed sheets of paper, or to insert or extract the belt device  102 . The door  31  is pivotally movable in the clockwise and counterclockwise direction of  FIG. 1 , about a pivotal shaft  32 , as a pivot, with which the bottom-right portion of the apparatus main assembly  101   a  is provided. When the door  31  is open, it remains in the state shown in part (a) of  FIG. 2 . 
         [0022]    The detailed description of the belt device  102  having the intermediary transfer belt unit  103  is given later. Referring to part (b) of  FIG. 2 , the belt device  102  is inserted into its designated position (shown in part (a) of  FIG. 2 ) in the apparatus main assembly  101   a , through a guiding passage  14  with a pair of components  13  and  13  formed of sheet metal and fixed to the front and rear ends (with reference to  FIG. 1 ) of the apparatus main assembly  101   a . It is also though this guiding passage  14  that the belt device  102  is pulled out of the apparatus main assembly  101   a.    
         [0023]    The components  13  and  13  formed of sheet metal have handle pressing portions  11  and  11 , one for one, formed by bending a part of each of the components  13  and  13  formed of sheet metal in such a manner that the bent part faces the belt device  102 . As for the belt device  102 , it is provided with a pair of handles  8   a  and  8   b . As the belt device  102  is inserted into the apparatus main assembly  101   a , the handles  8   a  and  8   b  are pressed into handle retreats (second position), one for one, by the handles pressing portions  11  and  11 . Further, when the belt device  102  is in the abovementioned designated position in the apparatus main assembly  101   a , the handles  8   a  and  8   b  are kept in their retreats (second position) by the handle pressing portion  11  and  11 . 
         [0024]    Incidentally, in this embodiment, the handle pressing portions  11  are parts of the front and rear components  13  and  13  formed of sheet metal, one for one. However, if the apparatus main assembly  101   a  is such that the space on the top side of the guiding passage  14  is large enough to accommodate the belt device  102 , with one of the handles  8   a  and  8   b  remaining protrusive, it may be only one of the front and rear components  13  formed of sheet metal that is provided with the handle pressing portion  11 . 
         [0025]    Sheets S of recording medium are stored in layers on the sheet lifting device  152  in the recording medium holding portion  151  of the image forming apparatus  101 . The sheets S are fed, in synchronism with image formation timing, into the apparatus main assembly  101   a  (and conveyed) by a sheet feeder roller  153  which is at the top-downstream edge of the recording medium storing portion  151 , in terms of the recording medium conveyance direction. The image feeding method does not need to be limited to the one used by the image forming apparatus  101  in this embodiment; a method other than the one used in this embodiment may be used. 
         [0026]    After being fed into the apparatus main assembly  101   a  by the sheet feeder roller  153 , each sheet S of recording medium is conveyed to a pair of registration rollers  155  through a recording medium feeding/conveying passage  154 . Then, the sheet S is corrected in attitude and/or conveyance timing by the pair of registration rollers  155 , and then, sent to the secondary transfer portion, which is the transfer nip formed by a secondary transfer roller  2  which is on the inward side of the belt loop the intermediary transfer belt  1  forms, and drives the belt, and a secondary transfer roller  156  which is on the outward side of the belt loop. As a preset amount of pressure and a preset electrostatic bias are applied to this secondary transfer portion, the toner image (image formed of toner) on the intermediary transfer belt  1  is transferred onto the sheet S of recording medium. 
       [Image Formation Process] 
       [0027]    Next, an image formation process which is carried out while a sheet S of recording medium is conveyed from the recording medium storage portion  151  to the secondary transfer portion is described. 
         [0028]    The image forming apparatus  101  has image forming sections  110 Y,  110 M,  110 C, and  110 K, each of which forms a toner image on the intermediary transfer belt  1  (endless belt) while the belt is circularly moved. The image forming section  110 Y forms an image with the use of yellow (Y)-colored toner, and the image forming section  110 Y forms an image with the use of magenta (M)-colored toner. The image forming section  110 C forms an image with the use of cyan (C)-colored toner, and the image forming section  110 K forms an image with the use of black (Bk)-colored toner. 
         [0029]    By the way, although the image forming sections  110 Y,  110 M,  110 C and  110 K are different in the color of the toner they use, they are similar in structure. Therefore, only the image forming section  110 Y is described, as a representative of the four portions, about its content. 
         [0030]    The image forming section  110 Y has: a photosensitive drum  111  as an image bearing member; a charging device  112  which charges the photosensitive drum  111 ; an exposing device  113 ; a developing device  114 ; a primary transferring device  115 ; and a photosensitive drum cleaning device  116 . As the photosensitive drum  111  is rotated in the direction indicated by an arrow mark m in  FIG. 1 , it is uniformly charged across its peripheral surface by the charging device  112 . 
         [0031]    A beam of laser light is outputted, while being modulated with image signals, from a scanner unit  126  which includes a laser, a polygon mirror, and a corrective lens system, is reflected by a mirror, and exposes the uniformly charged portion of the peripheral surface of the photosensitive drum  111 , in the exposing section. Consequently, an electrostatic latent image is effected on the peripheral surface of the photosensitive drum  111 . Then, the electrostatic latent image on the photosensitive drum  111  is developed by the developing device  114  into a toner image, on the photosensitive drum  111 . 
         [0032]    Thereafter, the yellow toner image is transferred onto the intermediary transfer belt  1  by the primary transferring device  115  to which a preset amount of pressure, and a preset electrostatic bias, are being applied. Transfer residual toner, or the toner remaining on the photosensitive drum  111  after the transfer, is recovered by the photosensitive member cleaning device  116 , to prepare the photosensitive drum  111  for the next image formation. 
         [0033]    The above-described image forming apparatus is provided with four image forming sections  110  ( 110 Y,  110 M,  110 C, and  110 B). Therefore, a magenta toner image formed by image forming section  110 M is transferred onto the intermediary transfer belt  1  in such a manner that it is laid upon the yellow toner image which was formed by the image forming section  110 M and transferred onto the intermediary transfer belt  1 . Then, a cyan toner image formed by the image forming section  110 C is transferred onto the intermediary transfer belt  1 , in such a manner that it is laid upon the magenta toner image on the intermediary transfer belt  1 . Further, a black toner image formed by the image forming section  110 K is transferred onto the intermediary transfer belt  1  in such a manner that it is laid upon the cyan image on intermediary transfer belt  1 . 
         [0034]    As the four toner images, different in color, are sequentially formed in layers on the intermediary transfer belt  1 , a full-color image is effected on the intermediary transfer belt  1 . By the way, a full-color image formed by the image forming apparatus  101  in this embodiment is made up of four monochromatic images, which are different in color. However, the number of the primary colors of which a full-color is to be effected does not need to be limited to four. Further, the order in which multiple monochromatic images, different in color, are to be formed does not need to be limited to that in which the monochromatic images are formed by the image forming apparatus  101  in this embodiment. 
       [Intermediary Transfer Belt] 
       [0035]    Next, referring to  FIG. 1 , the intermediary transfer belt  1  is described in detail. The intermediary transfer belt  1  is suspended and kept tensioned by the belt driving roller  2 , which doubles as the internal secondary transfer roller, a tension roller which provides the intermediary transfer belt  1  with a preset amount of tension, and idler rollers  4  and  5  as auxiliary tension rollers. The intermediary transfer belt  1  is circularly moved (conveyed, driven) in the direction indicated by an arrow mark V. 
         [0036]    The image formation processes, different in the color of the toner, are carried out by the above-described image forming sections  110 Y,  110 M,  110 C and  110 K, one for one, with such a timing that a toner image formed by a downstream image forming section  110  is transferred (primary transfer) onto the intermediary transfer belt  1  with such a timing that it is laid upon the image transferred onto the intermediary transfer belt  1  by an upstream image forming section  110 . Consequently, a full-color toner image is effected on the intermediary transfer belt  1 , and is conveyed to the secondary transfer section. Incidentally, the number of rollers by which the intermediary transfer belt  1  is suspended and kept tensioned does not need to be limited to the number of rollers by which the intermediary transfer belt  1  is suspended and kept tensioned in the image forming apparatus  101  structured as shown in  FIG. 1 . 
         [0000]    [Image Formation Processes Carried Out after Secondary Transfer Process] 
         [0037]    After the above-described image formation process, and process for conveying a sheet S of recording medium, are carried out with the above-described timing, the full-color toner image on the intermediary transfer belt  1  is transferred (secondary transfer) onto a sheet S of recording medium, in the secondary transfer section. 
         [0038]    Thereafter, the sheet S is conveyed by a pre-fixation conveying portion  157  to a fixing device  158 . There are various fixing devices which are different in structure and/or fixing method. However, the fixing device  158 , shown in  FIG. 1 , is of such a type that weld (fix) a toner image to a sheet S of recording medium by applying a preset amount of pressure and a preset amount of heat to the sheet S and the unfixed toner image thereon, in the fixation nip formed by a fixation roller  159  and a pressure roller  160 , which oppose each other. 
         [0039]    In the case of the fixing device  158  in this embodiment, the fixing device  158  is equipped with a heater as a heat source which is disposed in the hollow of the fixation roller  159 , and the pressure roller  160  is kept pressed against the fixation roller  159 . The sheet S is conveyed through the fixing device  158 , and conveyed to a pair of discharge-reversal rollers  161 . Then, it is discharged straight onto a delivery tray  162 , or guided by a sheet directing device  163  to a sheet conveying device  164  for two-sided image formation. When it is necessary to form an image on both surfaces of a sheet S of recording medium, the sheet S is switch-backed by the discharge-reversal rollers  161  so that the sheet edge, which was the downstream edge while an image is formed on the first surface of the sheet, becomes the upstream edge. Then, the sheet S is conveyed to the sheet conveying device  164  for two-sided image formation. 
         [0040]    Thereafter, it is conveyed into the sheet feeding/conveying passage  154  through a sheet re-feeding passage  165 , with such a timing that it does not interfere with the conveyance of the next sheet S of recording medium sent and conveyed by the sheet feeder roller  153  to form the next image. Then, it is sent to the second transferring portion as it was to form an image on its first surface. The process for forming an image on the back surface (second surface) of the sheet S is similar to the above-described process for forming an image on its front (first) surface, and therefore, is not described. The toner which failed to be transferred (secondary transfer) from the intermediary transfer belt  1  onto the sheet S, and therefore, is remaining on the intermediary transfer belt  1  after the secondary transfer is removed by the intermediary transfer belt cleaner  50 , which is kept in contact with the intermediary transfer belt  1 . 
       [Structure of Handle Section of Intermediary Transfer Belt Unit] 
       [0041]    Next, referring to  FIG. 3  and parts (a) and (b) of  FIG. 4 , a pair of handle sections  15   a  and  15   b  of the belt device  102 , which are for transporting the belt device  102 , and a pair of handle sections  16   a  and  16   b , which are for inserting the belt device  102  into the apparatus main assembly  101   a , or extracting the belt device  102  from the apparatus main assembly  101   a , are described about their structure.  FIG. 3  is a perspective view of the entirety of the belt device  102  which the image forming apparatus  101  has. Part (a) of  FIG. 4  is an enlarged perspective view of the transportation handle section  15   a  when the handle section  15   a  is in its outside position, and part (b) of  FIG. 4  is an enlarged front view of the transportation handle section  15   a  when the handle section  15   a  is in its inside position. 
         [0042]    Referring to  FIG. 3 , the belt device  102  has the intermediary transfer belt unit  103 , which is a belt unit structured so that it can be inserted into, or extracted from, the apparatus main assembly  101   a . The intermediary transfer belt unit  103  has a pair of support frames  6   a  and  6   b , which support the intermediary transfer belt  1  and are provided with a storage portion  33 . Further, the intermediary transfer belt unit  103  has the pair of transportation handle sections  15   a  and  15   b , which are outwardly offset from the main assembly of the intermediary transfer belt unit  103 , in the belt width direction (indicated by arrow mark W) which is intersectional (perpendicular) to the direction in which the intermediary transfer belt  1  is circularly moved. Further, the support frames  6   a  and  6   b  are provided with handle sections  16   a  and  16   b , respectively, for inserting the belt device  102  into the apparatus main assembly  101   a , or extracting the belt device from the apparatus main assembly  101   a . Further, the storage portion  33  with which each of the support frames  6   a  and  6   b  is provided has a storage space sp. 
         [0043]    The above-described support frames  6   a  and  6   b  are at the ends, one for one, of the intermediary transfer belt unit  103 , in terms of the belt width direction (indicated by arrow mark W) which is intersectional (perpendicular) to the direction (indicated by arrow mark V in  FIG. 3 ) in which the belt device  102  is inserted into, or extracted from, the apparatus main assembly  101   a . The two support frames  6   a  and  6   b  are connected to each other by an unshown frame, which is on the inward side of the loop which the intermediary transfer belt  1  forms. 
         [0044]    The aforementioned belt driving roller  2  (which also functions as inward secondary transfer roller), tension roller  3 , auxiliary tension roller  4 , and auxiliary tension roller  5  are supported by the support frames  6   a  and  6   b , by their lengthwise end portions. The support frames  6   a  and  6   b  are partially protrusive outward from the intermediary transfer belt  1 . Further, the downstream end portions of the support frames  6   a  and  6   b , in terms of the direction (indicated by arrow mark X in part (a) of  FIG. 4 ) in which the belt device  102  is inserted are provided with guide bosses  7   a  and  7   b , respectively, by which the support frames  6   a  and  6   b  are guided by the guide rails  13  and  13  of the apparatus main assembly  101   a , which are made of sheet metal. 
         [0045]    Referring to  FIG. 3 , and parts (a) and (b) of  FIG. 4 , the transportation handle sections  15   a  and  15   b  have handles  8   a  and  8   b , respectively, which are roughly outwardly curved. The belt device  102  is structured to enable the transportation handle sections  15   a  and  15   b  to move out of the storage portion  33  in such a manner that the handles  8   a  and  8   b  move into their outside position (first position) in which the handles  8   a  and  8   b  are protrusive from the main assembly of the belt device  102 , and also, that the handles  8   a  and  8   b  move into their retreat, or inside position (second position) in which they remain in the storage portion  33 . Further, the transportation handle sections  15   a  and  15   b  have a torsion coil spring  9  (only coil spring  9  of transportation handle section  15   a  is shown, for convenience sake), as a pressure applying means for keeping the transportation handle sections  15   a  and  15   b  pressured in the direction (handle erecting direction) to move the handles  8   a  and  8   b  from their inside position (second position) to the outside position (first position). 
         [0046]    The storage portions  33  are compartmentalized by the support frames  6   a  and  6   b , and have ribs  12  which are for strengthening the frames  6   a  and  6   b  and correspond in position to the bottom portion of the curved portions  26  of the handles  8   a  and  8   b . Incidentally, a referential code  30  in parts (a) and (b) of  FIG. 4  stands for a protrusion with which the support frames  6   a  and  6   b  are provided. The protrusion  30  is made to temporarily engage into a recess  29 , with which the handles  8   a  and  8   b  are provided, during the operation for attaching the handles  8   a  and  8   b  to the support frames  6   a  and  6   b.    
         [0047]    In terms of the direction in which the belt device  102  is inserted into, or extracted from, the apparatus main assembly  101   a , the handles  8   a  and  8   b  are located at the middle of the support frames  6   a  and  6   b , respectively. They are pivotally supported at roughly the center of gravity of the belt device  102  so that they are allowed to vertically emerge (come out) from, or submerge (retract) into, the main assembly of the belt device  102 . They are kept pressed by the torsion coil spring  9  in the direction to emerge in the vertical direction. One end  9   a  of the torsion coil spring  9  is in engagement with a protrusion  22  of the corresponding end portion  27  of the handles  8   a  and  8   b , whereas the other end  9   b  of the torsion coil spring  9  is in engagement with the coil spring engaging portions  34  of the support frames  6   a  and  6   b . The torsion coil spring  9 , which is an elastic member, makes up a pressing means for keeping the handles  8   a  and  8   b  pressed in the direction to move the handles  8   a  and  8   b  from the inside position (second position) to the outside position (first position). 
         [0048]    As the intermediary transfer belt unit  103  is inserted into the apparatus main assembly  101   a  in the direction indicated by the arrow mark X, shown in part (a) of  FIG. 4 , the handles  8   a  and  8   b  move to their inside position while remaining engaged with the handle pressing portion  11 , which is a part of the apparatus main assembly  101   a . On the other hand, as the intermediary transfer belt unit  103  is pulled out of the apparatus main assembly  101   a , the handles  8   a  and  8   b  are released from the handle pressing portions  11 , and therefore, move into the outside position, making it easier for an operator to transport the intermediary transfer belt unit  103 . 
         [0049]    That is, the handles  8   a  and  8   b  make it easier for the belt device  102  to be transported by an operator when the belt device  102  is out of the apparatus main assembly  101   a . If an operator wants to grasp the handles  8   a  and  8   b  to transport the belt device  102 , the operator is to insert his or her fingers into the space between the curved portion  26  of the handles  8   a  and  8   b , and the support frames  6   a  and  6   b , grasp the handles  8   a  and  8   b , and then, lift the belt device  102 . In order to increase the space between the curved portion  26  and corresponding support frames  6   a  and  6   b  to make it easier to grasp the curved portion  26 , the end portion  27  of each of the handles  8   a  and  8   b , which is between the pivotal shaft  20  and curved portion  26 , is given an appropriate length. 
         [0050]    Further, the transport handle sections  15   a  and  15   b  are pivotally supported by the pivotal shaft  20  ( FIG. 4  shows only transportation handle section  15   a ), by their end portion  27 . The pivotal shaft  20  which pivotally supports the transportation handle section  15   a  ( 15   b ) is parallel to the belt width direction (indicated by arrow mark W in  FIG. 3 ), which is intersectional to the rotational direction of the intermediary transfer belt  1 . Further, the transportation handle section  15   a  ( 15   b ) has a guide engaging portion  24 , which not only guides the handle  8   a  ( 8   b ) by the other end  23  of the handle  8   a  ( 8   b ) while the handle  8   a  ( 8   b ) moves between its outside position and inside position, but also, keeps the handle  8   a  ( 8   b ) locked in the outside position to make it possible for the handle  8   a  ( 8   b ) to be used for transporting the belt device  102 . The pivotal shaft  20  is provided with a disengagement prevention pawl (unshown) for preventing the handle  8   a  and  8   b  from becoming disengaged from the support frames  6   a  and  6   b , respectively. 
         [0051]    The transportation handle sections  15   a  and  15   b  are located at the outward ends (side) of the support frames  6   a  and  6   b  in terms of the belt width direction (indicated by arrow mark W). Further, they are roughly symmetrically positioned with reference to the line which is parallel to the lateral edges of the belt device  102  and coincides with the center G of gravity of the intermediary transfer belt unit  103 . Therefore, the belt device  102  in this embodiment is excellent in terms of the weight balance when an operator transports the belt device  102  by grasping the handles  8   a  and  8   b.    
         [0052]    Each of the handles  8   a  and  8   b  has the curved portion  26 , which is between the downstream end portion  27  and upstream end portion of the handle  8   a  ( 8   b ), in terms of the direction in which the intermediary transfer belt unit  103  is inserted into the apparatus main assembly  101   a , and is curved in a manner of protruding from the inside position (second position) to the outside position (first position). The abovementioned pivotal shaft  20  is at the downstream end of the handle  8   a  ( 8   b ) in terms of the direction in which the belt device  102  is inserted into the apparatus main assembly  101   a . Therefore, the handle  8   a  ( 8   b ) can be smoothly pushed into the inside position while causing the slanted surface of the handle  8   a  ( 8   b ), which is between the downstream end portion  27  and curved portion  26 , to slide on the end portion  11   a  ( FIG. 5 ) of the handle pressing portion  11 . 
         [0053]    While the belt device  102  is in the apparatus main assembly  101   a , the handle  8   a  ( 8   b ) is under the pressure applied from above by the handle pressing portion  11  of the apparatus main assembly  101   a . Therefore, it remains in the storage space sp in the support frame  6   a  ( 6   b ) (part (b) of  FIG. 4 ). In this case, the position of the handle  8   a  ( 8   b ) in the storage space sp of the support frame  6   a  ( 6   b ) in terms of the height of the intermediary transfer belt unit  103  is roughly the same as the intermediary transfer belt  1 . In other words, this embodiment can reduce the belt device  102  in overall height. 
         [0054]    Further, the storage space sp of the storage portion  33  is positioned so that the support frame  6   a  ( 6   b ) does not interfere with the rotational movement of the upstream end portion  23  of the handle  8   a  ( 8   b ). Therefore, in the case of the belt device  102  in this embodiment, it is unnecessary for a storage space for the handle  8   a  ( 8   b ) to be provided above the intermediary transfer belt  1 , unlike in the case of a belt device based on conventional technologies. 
         [0055]    Further, the guide engaging portion  24  has: a protrusion  24   a  which engages with the protrusion  25 , with which the upstream end portion  23  of the handle  8   a  ( 8   b ) is provided, and keeps the handle  8   a  ( 8   b ) in the support frame  6   a  ( 6   b ) compartmentalized to provide the storage portion  33 . The protrusion  24   a  has a guiding groove  24   b  which guides the protrusive portion  23   a  of the upstream end portion  23 , by which the handle  8   a  ( 8   b ) is guided by the guiding groove  24   b.    
         [0056]    The belt device  102  is structured so that as the handle  8   a  ( 8   b ) is pivotally moved, the protrusive portion  23   a  of the upstream protrusion  23  of the handle  8   a  ( 8   b ) is guided by the guiding groove  24   b  of the support frame  6   a  ( 6   b ). Further, the protrusive portion  23   a  is given a curvature, the center of which coincides with the axial line of the pivotal shaft  20 . Therefore, the protrusive portion  23   a  can smoothly slide in the guiding groove  24   b . As the handle  8   a  ( 8   b ) is allowed to be made to erect out of the support frame  6   a  ( 6   b ) by the torsion spring  9 , it pivots until it engages with the protrusion  24   a.    
         [0057]    The handle  8   a  of the support frame  6   a  and the handle  8   b  of the support frame  6   b , are shaped the same, and positioned so that they remain symmetrically positioned whether they are completely out of, or in, the support frames  6   a  and  6   b , respectively. Further, the aforementioned insertion-extraction handle sections  16   a  and  16   b  are provided with handles  10   a  and  10   b , which are on the downstream side of the insertion-extraction handle sections  16   a  and  16   b  in terms of the direction in which the belt device  102  is pulled out of the apparatus main assembly  101   a.    
         [0058]    In other words, the insertion-extraction handle sections  16   a  and  16   b  are attached to the support frames  6   a  and  6   b  in such a manner that they can be grasped by a user when the belt device  102  is inserted or extracted. The direction in which the belt device  102  is extracted from the apparatus main assembly  101   a  is parallel to the surface on which the apparatus main assembly  101   a  is placed. Therefore, the operation for guiding belt device  102  to the unit guiding rails  13  and  13  formed of sheet metal, in the apparatus main assembly  101   a , and inserting the belt device  102  into the apparatus main assembly  101   a , or the operation for extracting the belt device  102  from the apparatus main assembly  101   a , can be simply carried out by grasping the handles  10   a  and  10   b.    
         [0000]    [Insertion of Intermediary Transfer Belt Unit into Apparatus Main Assembly] 
         [0059]    Next, referring to parts (a)-(c) of  FIG. 5  and parts (a) and (b) of  FIG. 6 , the operation for inserting the belt device  102  into the apparatus main assembly  101   a  is described. Parts (a)-(c) of  FIG. 5  and parts (a) and (b) of  FIG. 6  show in steps how the belt device  102  is to be inserted into its designated position for image formation, in the apparatus main assembly  101   a.    
         [0060]    Incidentally, although the transportation handle sections  15   a  and  15   b  are positioned at opposite ends of the belt device  102 , they are the same in structure. Therefore, they are described with reference to primarily the transportation handle section  15   a , which is on the front side of the belt device  102 . 
         [0061]    First, the guiding bosses  7   a  and  7   b  with which the support frames  6   a  and  6   b  are provided, respectively, are guided by the unit guiding rails (part (b) of  FIG. 2 ) with which the apparatus main assembly  101   a  is provided. Thus, the belt device  102  is inserted into the apparatus main assembly  101   a  in the roughly horizontal direction indicated by the arrow mark X (part (a) of  FIG. 4 ). As described before, the apparatus main assembly  101   a  is provided with the pair of handle pressing portions  11  and  11 , which will be above the support frames  6   a  and  6   b  and will extend in the direction in which the belt device  102  is inserted, as the belt device  102  is inserted into the apparatus main assembly  101   a.    
         [0062]    That is, part (a) of  FIG. 5  shows the state in which the belt device  102  is after an operator has brought the belt device  102  to the apparatus main assembly  101   a  by grasping the handles  8   a  and  8   b , and has inserted the belt device  102  into the apparatus main assembly  101   a  until the guiding bosses  7   a  and  7   b  fit into the unit guide rails. As the belt device  102 , which is in the state shown in part (a) of  FIG. 5 , is inserted further into the apparatus main assembly  101   a , it moves in the direction indicated by the arrow mark X, until it moves into its designated position in the apparatus main assembly  101   a.    
         [0063]    In this case, by the way, even after the belt device  102  has been inserted into the apparatus main assembly  101   a  in the direction indicated by the arrow mark X, deep enough for the handles  8   a  and  8   b  to come into contact with the handle pressing portions  11  and  11 , the handles  8   a  and  8   b  remain erect, as shown in part (b) of  FIG. 5 , because of the resiliency of the torsion springs  9   a  and  9   b.    
         [0064]    However, as the belt device  102  is inserted deep enough into the apparatus main assembly  101   a  in the direction indicated by the arrow mark X, for the handles  8   a  and  8   b  to come under the handle pressing portions  11  and  11 , from the side of the downstream end portion  11   a , the handles  8   a  and  8   b  are moved downward into the storage space sp of the support frames  6   a  and  6   b , by the downstream end portion  11   a  of the handle pressing portion  11 , as shown in part (c) of  FIG. 5 . During this process, the handles  8   a  and  8   b  smoothly pivot toward their inside positions, that is, without hanging up at the handle pressing portions  11  and  11 , because the pivotal shaft  20  is on the downstream side of the slanted surface  28  in terms of the direction of the belt device insertion. 
         [0065]    Further, while the belt device  102  is inserted in the direction indicated by the arrow mark X into the primary transfer position after the insertion of the belt device  102  into the position shown in part (a) of  FIG. 6 , the handles  8   a  and  8   b  remain stored in the support frames  6   a  and  6   b . As the belt device  102  is stopped in its designated position, the operation ends (part (b) of  FIG. 6 ). 
         [0000]    [Extraction of Intermediary Transfer Belt Unit from Apparatus Main Assembly] 
         [0066]    Next, referring to parts (a)-(c) of  FIG. 7  and parts (a) and (b) of  FIG. 8 , the operation for extracting (pulling out) the belt device  102  from the apparatus main assembly  101   a  is described. Parts (a)-(c) of  FIG. 7  and parts (a) and (b) of  FIG. 8  show how the belt device  102  in its designated position in the apparatus main assembly  101   a  is to be pulled out of the apparatus main assembly  101   a.    
         [0067]    The operation for extracting the belt device  102  is carried out similarly to the operation for inserting the belt device  102  into the apparatus main assembly  101   a . The operator is to grasp the handles  10   a  and  10   b  of the belt device  102 , and pull the belt device  102  along the unit guide rails, by the handles  10   a  and  10   b  in the direction indicated by an arrow mark Y until the belt device  102  comes to the position in which the handles  8   a  and  8   b  can be grasped. 
         [0068]    That is, until the belt device  102 , which is in its designated position in the apparatus main assembly  101   a  as shown in part (a) of  FIG. 7 , is pulled outward, through the position shown in part (b) of  FIG. 7 , to the position shown in part (c) of  FIG. 7 , the handles  8   a  and  8   b  remain in the support frames  6   a  and  6   b , respectively. When the belt device  102  is in the position shown in part (c) of  FIG. 7 , the handle  8   a  ( 8   b ) will have reached the area below the upstream end  11   a  of the handle pressing portion  11 . 
         [0069]    Then, as the belt device  102  is pulled further in the direction indicated by the arrow mark Y, in the apparatus main assembly  101   a , as shown in part (a) of  FIG. 8 , the handle  8   a  ( 8   b ) passes by the upstream end  11   a . As the handle  8   a  ( 8   b ) passes by the upstream end  11   a , the handle  8   a  ( 8   b ), which is under the pressure from the torsion spring  9 , automatically and pivotally erects. 
         [0070]    As the handle  8   a  ( 8   b ) erects as described above, it becomes very easy to see to transport the belt device  102 . Then, after the belt device  102  is pulled out in the direction indicated by the arrow mark Y to the position shown in part (b) of  FIG. 8 , the operator is to grasp the handle  8   a  ( 8   b ) so that the belt device  102  can be quickly transported. 
         [0071]    In the case of this embodiment, the transportation handle sections  15   a  and  15   b  are attached to the support frames  6   a  and  6   b  so that they outwardly offset from the intermediary transfer belt  1  in terms of the width direction of the intermediary transfer belt  1 ; are storable in the storage portion  33  when the belt device  102  is inserted into the apparatus main assembly  101   a ; and can be made to protrude when the belt device  102  is pulled out of the apparatus main assembly  101   a . That is, the belt device  102  in this embodiment can be reduced in the height of the intermediary transfer belt unit  103 . Further, the handles  8   a  and  8   b  regulate their movement relative to the handle pressing portions  11  and  11  by themselves. Therefore, it is smaller in component count and cost. That is, the present invention can reduce a belt device in component count and cost. 
         [0072]    Further, a belt device of the conventional type is problematic in that the apparatus main assembly  101   a  requires a substantial amount of space for belt unit insertion. In comparison, in the case of the belt device  102  in this embodiment, the handles  8   a  and  8   b  retract into the support frames  6   a  and  6   b , respectively. Therefore, the abovementioned space is substantially smaller. That is, this embodiment can minimize in size the above-described space. 
         [0073]    Incidentally, in the case of this embodiment, the present invention was applied to a combination of the image forming apparatus  101  and belt device  102 , which is of such a type that one of the lateral walls of the apparatus main assembly  101   a  is provided with the door  31  which is to be opened to insert the belt device  102  into the apparatus main assembly  101   a  or extract the belt device  102  from the apparatus main assembly  101   a . However, the application of the present invention is not limited to an image forming apparatus of the above-described type. That is, the present invention is also applicable to an image forming apparatus, of such a type that the apparatus main assembly  101   a  is vertically opened or closed. 
         [0074]    The application of the present invention is not limited to a color printer of the so-called tandem type, such as the one in this embodiment. That is, the present invention is also applicable to various image forming apparatuses other than the one in this embodiment, such as a monochromatic copying machine, a digital multifunction machine, a facsimile machine, a laser printer, etc., which employ a unit which can be inserted into, or extracted from, their main assembly. 
         [0075]    While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
         [0076]    This application claims priority from Japanese Patent Application No. 193727/2013 filed Sep. 19, 2013, which is hereby incorporated by reference herein in its entirety.