Patent Publication Number: US-9423762-B2

Title: Image forming apparatus with frame having hollowly-formed connecting frames

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority from Japanese Patent Application No. 2013-129798, filed on Jun. 20, 2013, the entire subject matter of which is incorporated herein by reference. 
     BACKGROUND 
     1. Technical Field 
     An aspect of the present invention relates to an image forming apparatus having an optical scanner configured to emit exposure light to a photosensitive drum. 
     2. Related Art 
     An image forming apparatus having an optical scanner is known. The image forming apparatus may include a scanner-supporting plate arranged in a lower position with respect to the optical scanner, an upper frame arranged in an upper position with respect to the optical scanner, and side frames arranged on lateral positions of the scanner-supporting plate and the upper plate so that the scanner-supporting plate and the upper plate may be attached to the lateral frames at lateral ends thereof. In such an image forming apparatus, each of the scanner-supporting plate and the upper plate may be assembled independently in a body of the image forming apparatus. In this regard, the scanner-supporting plate, the upper plate, and the lateral frames may form an open cross-section when viewed along a plane orthogonal to a crosswise direction thereof. 
     SUMMARY 
     In the image forming apparatus with the above-mentioned frame structure in the body, in which the lateral frames are connected with each other by the lower and upper plates, while the lower and upper plates are assembled in the body independently from each other, substantial rigidity may not be provided. 
     The present invention is advantageous in that an image forming apparatus, in which rigidity in a frame structure having a pair of mutually connected lateral frames is increased, is provided. 
     According to an aspect of the present invention, an image forming apparatus is provided. The image forming apparatus includes a plurality of image forming units, each of which comprises a photosensitive drum configured to be rotatable about a rotation axis and a developer device configured to supply a developer agent to the photosensitive drum, the plurality of image forming unit being aligned along an aligning direction, the aligning direction being orthogonal to an axial direction, which is a direction of the rotation axes of the photosensitive drums; a pair of frames arranged to face each other along the axial direction across the plurality of image forming units, the pair of frames being configured to support the plurality of image forming units; an optical scanner arranged on one side of the plurality of image forming units along an orthogonal direction orthogonal to the aligning direction and to the axial direction, the optical scanner being configured to emit exposure light to the plurality of photosensitive drums; a first connecting frame made of a metal and formed to be hollow providing a space inside, the first connecting frame being coupled to the pair of frames at both ends thereof along the axial direction and being configured to accommodate the optical scanner therein; and a second connecting frame made of a metal and arranged on another side of the plurality of image forming units along the orthogonal direction, the second connecting frame being formed to be hollow providing a space inside, the second connecting frame being coupled to the pair of frames at both ends thereof along the axial direction. 
    
    
     
       BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS 
         FIG. 1  is a cross-sectional side view of a color printer according to an embodiment of the present invention. 
         FIG. 2  is a cross-sectional side view of the color printer with a drawer being drawn out of a body of the color printer according to the embodiment of the present invention. 
         FIG. 3  is a perspective view of the body of the color printer according to the embodiment of the present invention. 
         FIG. 4  is an exploded view of a first connecting frame in the color printer according to the embodiment of the present invention viewed from an upper rear view point. 
         FIG. 5  is an exploded view of a second connecting frame and an L-shaped metal piece in the color printer according to the embodiment of the present invention taken from an upper front view point. 
         FIG. 6  is an exploded view of the second connecting frame in the color printer according to the embodiment of the present invention viewed from an upper front view point. 
         FIG. 7  is a perspective view of a third plate in the body of the color printer and a fourth plate being removed from side frames in the color printer according to the embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, a configuration of a color printer  1  according to an embodiment of the present invention will be described with reference to the accompanying drawings. First, an overall configuration of the color printer  1  will be described, and second, specific components in the color printer  1  will be described in detail. 
     In the following description, directions concerning the color printer  1  will be referred to in accordance with orientation indicated by arrows in each drawing. Therefore, for example, a viewer&#39;s left-hand side appearing in  FIG. 1  is referred to as a front side of the color printer  1 , and a right-hand side in  FIG. 1  opposite from the front side is referred to as a rear side. A side which corresponds to the viewer&#39;s nearer side is referred to as a right-hand for a user, and an opposite side from the right, which corresponds to the viewer&#39;s farther side is referred to as a left-hand side for the user. An up-down direction in  FIG. 1  corresponds to a vertical direction of the color printer  1 . Further, the right-to-left or left-to-right direction of the color printer  1  may be referred to as a widthwise direction, and the front-to-rear or rear-to-front direction may be referred to as a direction of depth. The widthwise direction and the direction of depth are orthogonal to each other. Furthermore, directions of the drawings in  FIGS. 2-7  are similarly based on the orientation of the color printer  1  as defined above and correspond to those with respect to the color printer  1  shown in  FIG. 1  even when the drawings are viewed from different angles. 
     Overall Configuration of the Color Printer 
     The color printer  1  includes a feeder unit  20 , an image forming unit  30 , and an ejection unit  90 , which are arranged inside a body  10 . The feeder unit  20  is configured to feed a sheet P in the body  10 , the image forming unit  30  is configured to form an image on the sheet P being fed, and the ejection unit  90  is configured to eject the sheet P with the image formed thereon outside. A configuration of the body  10  of the color printer  1  will be described later in detail. 
     The feeder unit  20  includes a feeder tray  21  to store the sheet P therein and a sheet conveyer  22  to convey the sheet P from the feeder tray  21  to the image forming unit  30 . 
     The image forming unit  30  includes an optical scanner  40 , a plurality of (e.g., four) processing units  50 , a drawer  60 , a transfer unit  70 , and a fixing unit  80 . 
     The optical scanner  40  is arranged on one side of the plurality of processing units  50  along a direction orthogonal to an axial direction and to an aligning direction of photosensitive drums  51 , which will be described later in detail. In other words, the optical scanner  40  is arranged in an upper position with respect to the plurality of processing units  50 , in the body  10 . The optical scanner  40  includes a laser-beam emitter (not shown), a plurality of polygon minors (unsigned), lenses (unsigned), and a plurality of reflection minors (unsigned). Laser beams emitted from the laser-beam emitter for a plurality of (e.g., four) colors are reflected on the polygon minors and the reflection minors and transmit through the lenses to be casted to scan on surfaces of photosensitive drums  51  in the processing units  50 . 
     The processing units  50  are aligned in line, along a direction of depth (i.e., a front-rear direction) of the color printer  1 , orthogonally to the direction of rotation axes of the photosensitive drums  51 . Each of the processing units  50  includes the photosensitive drum  51 , which is rotatable about a rotation axis thereof extending along the widthwise direction, a charger  52  to electrically charge the photosensitive drum  51 , and a developer cartridge  53 . Each developer cartridge  53  includes a developer roller  54  to supply a developer agent (e.g., toner) to the photosensitive drum  51  and a toner container  56  to store the toner therein. All the processing units  51  are configured similarly but different from one another in colors of the toner contained in the toner containers  56 . 
     The drawer  60  supports the plurality of processing units  50  and is movable along the front-rear direction with respect to a pair of side frames  12 ,  13 , which form lateral walls of the body  10  of the color printer  1 . Each of the side frames  12 ,  13  is provided with a rail RA, solely one of which on the left is shown in  FIGS. 2 and 3 , so that the drawer  60  is guided by the rails RA to move frontward or rearward along the front-rear direction. As shown in  FIG. 2 , the drawer  60  can be drawn out of the body  10  of the color printer  10  through an opening  10 A, which is exposed when a front cover  11  arranged on the front side of the body  10  is opened. Thus, the processing units  50  are exposed to the outside atmosphere. 
     Referring back to  FIG. 1 , the transfer unit  70  is arranged in a position between the feeder unit  20  and the drawer  60 . The transfer unit  70  includes a driving roller  71 , a driven roller  72 , a conveyer belt  73 , and transfer rollers  74 . 
     The driving roller  71  and the driven roller  72  are arranged to extend axially in parallel with each other in spaced-apart positions from each other along the front-rear direction so that the conveyer belt  73  being an endless belt is strained to roll around the driving roller  71  and the driven roller  72 . The conveyer belt  73  is arranged to have an upper outer surface thereof to be in contact with the photosensitive drums  51 . A plurality of (e.g., four) transfer rollers  74  are arranged in positions opposite from the photosensitive drums  51  across the conveyer belt  73 , and the conveyer belt  73  is in contact with the transfer rollers  74  at an upper inner surface thereof. Transfer bias under constant current control is applied to the transfer rollers  74  to transfer an image from the photosensitive drums  51  to the sheet P. 
     The fixing unit  80  is arranged in a rear position with respect to the processing units  50  and includes a heat roller  81  and a pressure roller  82 . The pressure roller  82  is arranged in a position to face the heat roller  81  and is urged against the heat roller  81 . 
     In each of the processing units  50  in the image forming unit  30  configured as above, the charger  52  electrically charges a surface of the photosensitive drum  51  evenly, and the surface of the photosensitive drum  51  is exposed to the laser beam emitted selectively based on image data from the optical scanner  40  in order to form a lower-potential regions, i.e., an electrostatic latent image representing the image to be formed on the sheet P, thereon. Thereafter, the toner is supplied to the latent image on the photosensitive drum  51  from the developer cartridge  53  through the developer roller  54 . Thus, the latent image is developed to be a toner image and carried on the surface of the photosensitive drum  51 . 
     When the sheet P supplied from the feeder unit  20  is carried on the conveyer belt  73  to a position between the photosensitive drum  51  and the transfer roller  74 , the toner image formed on the surface of the photosensitive drum  51  is transferred onto the sheet P. Thus, four colored images are sequentially overlaid on the surface of the sheet P to form a colored image. The sheet P with the transferred toner images is carried to a nipped position between the heat roller  81  and the pressure roller  82  in the fixing unit  80  to have the toner images thermally fixed thereon. 
     The ejection unit  90  includes a plurality of conveyer rollers  91  to convey the sheet P. The sheet P with the fixed image is ejected out of the body  10  of the color printer  1  by the conveyer rollers  91 . 
     Configuration of the Body  10  of the Color Printer  1   
     As shown in  FIG. 3 , the body  10  of the color printer  1  includes the paired side frames  12 ,  13 , a first connecting frame  100  to connect upper portions of the side frames  12 ,  13 , a second connecting frame  200  to connect lower rear portions of the side frames  12 ,  13 , and lower beams  14  to connect lower ends of the side frames  12 ,  13 . The lower beams  14  are elongated metal bars extending along the widthwise direction. One of the lower beams  14  is arranged on the front side of the side frames  12 ,  13 , and another one of the lower beams  14  is arranged on the rear side of the side frames  12 ,  13 . 
     The side frames  12 ,  13  are resin plates, each of which is formed to have an approximate shape of a rectangle, and are arranged on the left side and the right side in the color printer  1  to have a predetermined amount of clearance there-between to accommodate the processing units  50  therein. The processing units  50  disposed in the clearance is supported by the side frames  12 ,  13  via the drawer  60 . 
     The first connecting frame  100  is a metal frame forming a shape of a sleeve, which is hollow and provides a space inside, and a cross-section of the first connecting frame  100  taken along a plane orthogonal to the widthwise direction is closed. Widthwise ends of the first connecting frame  100  are connected to the side frames  12 ,  13 . The first connecting frame  100  is arranged in an upper position with respect to the processing units  50  and accommodates the optical scanner  40  in the hollow space. 
     With the sleeve-shaped first connecting frame  100  connected with the side frames  12 ,  13  at the widthwise ends thereof, the first connecting frame  100  can provide enhanced rigidity compared to, for example, the conventional frame structure, in which the upper and lower plates independently arranged in the upper and lower positions with respect to the optical scanner are connected to the side frames respectively. In this regard, while the optical scanner  40  is accommodated in the first connecting frame  100 , the first connecting frame  100  may not only provide the increased rigidity to the color printer  1  but also protect the optical scanner  40  securely. 
     The first connecting frame  100  is formed to have a dimension in the front-rear direction being substantially equivalent to a dimension in the front-rear direction of the drawer  60  and is arranged to overlap the processing units  50  in a perspective view projected along the vertical direction. Thus, the first connecting frame  100  arranged over the processing units  50  may provide the rigidity to the body  10  of the color printer  1  effectively. 
     Meanwhile, the first connecting frame  100  is arranged to locate a center C 1  thereof along the front-rear direction in a frontward position deviated from a center C of the side frames  12 ,  13  along the front-rear direction. In other words, the first connecting frame  100  is arranged in a frontward off-centered position closer to the front ends rather than the rear ends of the side frames  12 ,  13 . 
     As shown in  FIG. 4 , the first connecting frame  100  includes a first metal plate  110  and a second metal plate  120 , which are formed to have cross-sectional shapes of “L.” The first metal plate  110  includes a lower plate  111  to be arranged in a lower position with respect to the optical scanner  40  to support the optical scanner  40  and a rear plate  112  to be arranged in a rear position with respect to the optical scanner  40 . 
     The lower plate  111  is formed in an approximate shape of a rectangle and has a lower plane  111 A, which spreads along the front-rear direction and the widthwise direction. The lower plane  111 A faces the processing units  50  (see  FIG. 1 ). The lower plate  111  includes flanges  111 B,  111 C,  111 D, which extend upward from a front end, a right-side end, and a left-side end of the lower plate  111  respectively. 
     The flange  111 B, at the front end of the lower plate  111 , is formed to have a plurality of in-flange holes  111 E, in which screws S 1  to fasten the second metal plate  120  to the first metal plate  110  are screwed. In other words, the flange  111 B provides a fixing structure, by which the second metal plate  120  is fixed to the first metal plate  110 , in the areas surrounding the in-flange holes  111 E. 
     On the right-side end of the lower plate  111 , a plurality of engageable protrusions  111 F, which protrude outward along the widthwise direction from the flange  111 C on the right-hand side, are formed. The engageable protrusions  111 F are formed when the flange  111 C is bent upward. More specifically, the engageable protrusions  111 F originally consist of parts of the flange  111 C until the flange  111 C is bent with respect to the lower plate  111 . Once openings, of which shape correspond to the engageable protrusions  111 F, are formed in the flange  111 C, and the flange  111 C is bent with respect to the lower plate  111 , the engageable protrusions  111 F remain unbent to protrude outward from the right-side end of the lower plate  111  along the widthwise direction. The engageable protrusions  111 F formed as above are, as shown in  FIG. 5 , inserted in engageable openings  301  from inside toward outside along the widthwise direction. The engageable openings  301  are formed in an L-shaped metal piece  300 , which is fixed to the side frame  12 . 
     The L-shaped metal piece  300  includes a main part  300 A elongated along the front-rear direction and an extended part  300 B extended downward from the main part  300 A toward a side where the photosensitive drums  51  are disposed. The main part  300 A is arranged to overlap the first connecting frame  100  in a perspective view projected along the widthwise direction, which coincides with the axial direction of the photosensitive drums  51 . The extended part  300 B supports a positioning shaft  310  (see also  FIG. 1 ), which is engageable with a rear part of the drawer  60  to place the drawer  60  in a correct position in the body  10  of the color printer  1 . The L-shaped metal piece  300  is stably fixed to the side frame  12  on an inner side of the side frame  12  along the widthwise direction. 
     As shown in  FIGS. 4 and 5 , the flange  111 C on the right is formed to have a plurality of in-flange holes  111 G, in which screws S 2  to fasten the flange  111 C to the L-shaped metal piece  300  are screwed, in upper positions in the flange  111 C. Thus, with the L-shaped metal piece  300  fastened to the first metal plate  110 , rigidity of the L-shaped metal piece  300  can be increased. Therefore, while the rigidity of the L-shaped metal piece  300  is secured, the drawer  60  can be placed in the correct position preferably by relying on the position of the L-shaped metal piece  300 . Further, a relative position between the optical scanner and the drawer  60  can be maintained correctly. 
     Although detailed description is herein omitted, the left-side end of the lower plate  111  is configured to have the same structure, including the engageable protrusions  111 F, the in-flange holes  111 G, and the L-shaped metal piece  300 , as the right-side end of the lower plate  111 . 
     As shown in  FIG. 4 , the rear plate  112  is formed by bending a rear portion of the lower plate  111  upward. The rear plate  112  includes a plurality of fixing flanges  112 A, which are formed by cuts and bends to protrude rearward, at an upper end thereof. Each of the fixing flanges  112 A is formed to have an in-flange hole  112 B, in which a screw S 3  to fasten the second metal plate  120  to first metal plate  110  is screwed. 
     The second metal plate  120  includes an upper plate  121  and a front plate  122 , which are to be arranged in an upper position and a frontward position with respect to the optical scanner  40  respectively. 
     The upper plate  121  is arranged to spread along an upper surface of the optical scanner  40 . The upper plate  121  is formed to have an upward bulge in a central portion thereof, to have a cross-sectional shape similar to a cross-section of a hat. The upper plate  121  includes an upper plane  121 A, which spreads in parallel with the lower plane  111 A of the lower plate  111 . The upper plane  121 A faces the lower plane  111 A of the lower plate  111  across the optical scanner  40  (see  FIG. 1 ). The upper plate  121  includes a plurality of fixing flanges  121 B on a rear edge thereof. The plurality of fixing flanges  121 B protrude rearward from the rear edge of the upper plate  121  and are formed to have through holes  121 C, in which the screws S 3  to fasten the second metal plate  120  to first metal plate  110  are screwed. 
     Thus, by placing the fixing flanges  112 A of the first metal plate  110  over the fixing flanges  121 B of the second metal plate  120 , and by fastening the screws S 3  through the through holes  121 C to the in-flange holes  112 B, the rear plate  112  in the first metal plate  110  and the rear end of the upper plate  121  in the second metal plate  120  are fastened to each other. 
     On widthwise ends of the upper plate  121 , a plurality of positioning holes  121 D are formed. The positioning holes  121 D are engageable with a plurality of positioning projections  12 A,  13 C, which are formed to protrude upward from upper edges of the side frames  12 ,  13  respectively (see  FIG. 3 ). Further, the upper plate  121  is formed to have a plurality of through holes  121 E, through which a plurality of screws S 4  (see  FIG. 3 ) to fasten the upper plate  121  to the side frames  12 ,  13  are screwed, in positions in proximity to the positioning holes  121 D. Meanwhile, on the upper edges of the side frames  12 ,  13 , a plurality of screw holes (not shown), to which the screws S 4  are screwed, are formed. 
     Thus, as shown in  FIGS. 3 and 4 , when the first metal plate  110  is placed on the upper edges of the side frames  12 ,  13  with the positioning holes  121 D fitted around the positioning projections  12 A,  13 A, the through holes  121 E coincide with the screw holes formed in the side frames  12 ,  13 . Therefore, when the screws S 4  are screwed to the screw holes in the side frames  12 ,  13  through the through holes  121 E, the upper plate  121  is fastened to the side frames  12 ,  13 . 
     As shown in  FIG. 5 , the front plate  122  is formed by bending a front portion of the upper plate  121  downward. When the first metal plate  110  and the second metal plate  120  are assembled together, the front plate  122  covers the flange  111 B at the front side of the first metal plate  110  from outside along the front-rear direction. The front plate  122  is formed to have a plurality of through holes  122 A, through which the screws Si are inserted, in lower positions corresponding to the in-flange holes  111 E (see  FIG. 4 ) formed in the flange  111 B of the first metal plate  110 . More specifically, each of the through holes  122 A is formed on a closed-end wall in a dent  122 B, which is formed to recess rearward from the front plate  122 , while a rear side of the closed-end wall in the dent  122 B contacts the flange  111 B on the front side of the first metal plate  110 . 
     Therefore, by placing the front plate  122  on the outer side of the flange  111 B of the first metal plate  110  to cover the flange  111 B along the front-rear direction, and by fastening the screws S 1  through the through holes  122 A to the in-flange holes  111 E, the flange  111 B on the front side of the first metal plate  110  and the front plate  122  are fastened to each other. Thus, the first connecting frame  100  having the first metal plate  110  and the second metal plate  120  is formed to have a shape of a sleeve with a closed cross-section when taken along the plane orthogonal to the widthwise direction. In this regard, the first metal plate  110  and the second metal plate  120  are coupled to the side frames  12 ,  13  at the widthwise ends thereof. 
     As shown in  FIG. 1 , the second connecting frame  200  is a metal frame formed in a shape of a sleeve, which is hollow and provides a space inside. A cross-section of the second connecting frame  200  is closed when taken along the plane orthogonal to the widthwise direction. The second connecting frame  200  is coupled to the side frames  12 ,  13  at widthwise ends thereof. The second connecting frame  200  is arranged in a lower position with respect to the processing units  50 . 
     Thus, the first connecting frame  100  and the second connecting frame  200  are arranged to align along the vertical direction to place the processing units  50  interposed there-between. Therefore, central areas of the side frames  12 ,  13 , i.e., areas coincident with the processing units  50  along the direction of rotation axes, can be effectively enhanced. 
     According to the configuration described above, the drawer  60  to support the processing units  50  is arranged in the intermediate position between the first connecting frame  100  and the second connecting frame  200  along the vertical direction; therefore, the rigidity of the body  10  of the color printer  1  can be maintained while the space for the drawer  60  to move therein is reserved. 
     According to the configuration described above, a central area C 2  of the second connecting frame  200  along the front-rear direction is arranged in a rearward position deviated from the center C of the side frames  12 ,  13  along the front-rear direction. In other words, the second connecting frame  200  is arranged in the rearward off-centered position closer to the rear ends rather than the front ends of the side frames  12 ,  13 . Therefore, with regard to the relative position among the second connecting frame  200 , the side frames  12 ,  13 , and the first connecting frame  100 , the first connecting frame  100  is disposed in the frontward position closer to the front ends of the side frames  12 ,  13  while the second connecting frame  200  is disposed in the rearward position closer to the rear ends of the side frames  12 ,  13 . Thus, the first connecting frame  100  and the second connecting frame  200  are disposed in diagonal positions with respect to each other in the side frames  12 ,  13 . Accordingly, the rigidity of the body  10  of the color printer  1  may be effectively increased. 
     According to the configuration described above, the second connecting frame  200  is formed to range from a position in proximity to the rear end of the first connecting frame  100  to a position in proximity to the rear ends of the side frames  12 ,  13  along the front-rear direction. Further, the second connecting frame  200  is arranged to overlap the first connecting frame  100 , at least partly, in the perspective view projected along the vertical direction. Therefore, an entire range of the side frames  12 ,  13  along the front-rear direction is enhanced by the first and second connecting frames  100 ,  200 , and the rigidity of the body  10  of the color printer  1  may be effectively increased. 
     Meanwhile, inside the second connecting frame  200 , a power board  400  to supply power to electrically movable components, such as the processing units  50 , is disposed. On the power board  400 , a transformer  401  (see  FIGS. 1, 2, and 7 ) being one of elements composing a power circuit, is mounted. While the power board  400  is accommodated in the metal-made second connecting frame  200 , noises generated in the power board  400  may be prevented from being radiated. 
     As shown in  FIGS. 6 and 7 , the second connecting frame  200  includes a third metal plate  210  and a fourth metal plate  220 , which are formed to have approximately L-shaped cross-sections when taken along the plane orthogonal to the widthwise direction. 
     The third metal plate  210  includes an upper wall  211  and a front wall  212 , which are arranged in an upper position and a frontward position with respect to the power board  400  respectively. The upper wall  211  is formed to have a front part  211 X and a rear part  211 Y, which are formed in split levels. The rear part  211 Y is formed in an upper level, and the front part  211 X is formed in a lower level. The transformer  401  is disposed in a lower position with respect to the rear part  211 Y. On widthwise ends of the upper wall  211 , fixing flanges  211 A,  211 B,  211 C are formed by bending end portions downward or rearward in the sleeve-shaped second connecting frame  200 . The fixing flanges  211 A- 211 C are formed to have through holes  211 D, through which screws (not shown) to fasten the fixing flanges  211 A- 211 C to the side frames  12 ,  13  are inserted. Further, the fixing flanges  211 B,  211 C are formed to have reference openings  211 G, which are referred to when the second connecting frame  200  is placed in the correct position with respect to the side frames  12 ,  13 . 
     A plurality of connecting flanges  211 E are formed by bending rear-end portions of the upper wall  211  downward. Each of the connecting flanges  211 E is formed to have an in-flange hole  211 F, through which a screw S 5  to fasten the fourth metal plate  220  to the third metal plate  210  is inserted. 
     The front wall  212  of the third metal plate  210  is formed by bending a front end portion of the upper wall  211  downward. At a lower end of the front wall  212 , an engageable hole  212 A, through which an engageable piece  221 B of the fourth metal plate  220  is inserted from the rear side toward the front side, is formed. The engageable piece  221 B will be described later in detail. 
     The fourth metal plate  220  includes a lower wall  221 , which is arranged in a lower position with respect to the power board  400  to support the power board  400 , and a rear wall  222  arranged in a rearward position with respect to the power board  400 . 
     The lower wall  221  is formed in an approximate shape of a rectangle and has a plurality of bulges  221 A, which protrude upward to support the power board  400 . At a front end of the lower wall  221 , the engageable piece  221 B is formed to protrude frontward. 
     On widthwise ends of the lower wall  221 , engageable flanges  221 C protruding upward are formed by bending widthwise end portions of the lower wall  221  upward. The engageable flanges  221 C are movably supported by grooves formed in the side frames  12 ,  13  to move along the front-rear direction. 
     The rear wall  222  is formed by bending a rear end portion of the lower wall  221  upward. At upper positions in the rear wall  222 , as shown in  FIG. 7 , a plurality of through holes  222 A, through which the screws S 5  to fasten the fourth metal plate  220  to the third metal plate  210  is inserted, is formed. At lower positions in the rear wall  222 , a plurality of through holes  222 B, through which screws S 6  to fasten the fourth metal plate  220  to the side frames  12 ,  13  are inserted, are formed. Meanwhile, the side frames  12 ,  13  are formed to have screw holes  12 B,  13 B, to which the screws S 6  are screwed, respectively. 
     The fourth metal plate  220  is movable along the front-rear direction to be detached from or attached to the third metal plate  210  and the side frames  12 ,  13  while the screws S 5 , S 6  are removed. Therefore, by removing the fourth metal plate  220  from the third metal plate  210  and the side frames  12 ,  13 , a user can easily access the power board  400  to exchange with a new power board  400 . More specifically, through an opening which is exposed when a rear cover  15  (see  FIG. 1 ) arranged on the rear side of the body  10  of the color printer  1  is opened, the fourth metal plate  220  can be removable from the third metal plate  210  and the side frames  12 ,  13 . 
     Thus, the second connecting frame  200 , including the third metal plate  210  and the fourth metal plate  220 , is formed in a shape of a sleeve having a closed cross-section, when taken along the plane orthogonal to the widthwise direction. Meanwhile, the third metal plate  210  and the fourth metal plate  220  are coupled to the side frames  12 ,  13  at the widthwise ends thereof. In this regard, the second connecting frame  200  is open sideward at the widthwise ends thereof, and one of the openings on the right aligns with an air duct  12 C formed in the side frame  12  so that air to cool the power board  400  can be introduced through the air duct  12 C and the opening. 
     According to the embodiment described above, with the first connecting frame  100  having the lower plane  111 A and the upper plane  121 A, which spread in parallel with each other along the front-rear direction, when external force is applied to the side frames  12 ,  13 , the relative position between the optical scanner  40  and the processing units  50  can be maintained substantially in parallel steadily. 
     According to the embodiment described above, the first connecting frame  100  is formed with the metal plates  110 ,  120 , which provide certain rigidity. Therefore, the first connecting frame  100  can maintain the stable shape of the sleeve, and the optical scanner  40  can be securely stored inside the connecting frame  100 . 
     Although an example of carrying out the invention has been described, those skilled in the art will appreciate that there are numerous variations and permutations of the image forming apparatus that fall within the spirit and scope of the invention as set forth in the appended claims. It is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or act described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims. 
     For example, the developer cartridge  53  may not necessarily be configured to include the developer roller  54  and the toner container  56  but may include a developer device containing the rollers alone, and the toner container  56  may be replaced with an exchangeable toner cartridge. 
     For another example, the sleeve-form of the connecting frames  100 ,  200  may not necessarily include the L-shaped metal pieces. For example, the sleeve-form of the connecting frames  100 ,  200  may be achieved by assembling a U-shaped metal piece and a flat metal plate. For another example, the sleeve-form may be achieved by forming the upper, lower, front, and rear sides of each of the connecting frames  100 ,  200  integrally. 
     For another example, the electrically movable components may not necessarily be limited to the processing units  50  but may include, for example, a motor to drive the photosensitive drums  51 . 
     For another example, the processing units  50  supported by the drawer  60  may be removable from the drawer  60 . For another example, a part of each processing unit  50 , such as the developer cartridge  53 , may be removable from the drawer  60 . For another example, the photosensitive drums  51  may be integral with the drawer  60  to be supported by the drawer  60 . 
     The embodiment described above may not necessarily be applied to a monochrome printer, a color printer but may be employed in, for example, a copier or a multifunction peripheral device.