Patent Publication Number: US-RE46128-E

Title: Sheet tray device with slide portion and image forming apparatus having the sheet tray device

Description:
This application is a reissue application of U.S. Pat. No. 7,748,692 B2, which is issued from U.S. application Ser. No. 11/677,122 and which is based on Japanese Patent Application No. 2006-048514 filed on Feb. 24, 2006, the content contents of which is are incorporated hereinto by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a sheet tray device for accommodating a media sheet such as paper sheet, OHP sheet, envelop and postal card, and also an image forming apparatus including such a sheet tray device. 
     2. Discussion of Related Art 
     It is common that a sheet tray device for use in an image forming apparatus is provided by a single tray member that is removably introduced into a main body of the image forming apparatus, as disclosed in JP-2005-314067A. 
     The sheet tray device is required to accommodate the media sheets of various sizes such as A4-sized papers and A-5 sized papers. However, the media sheets of plurality of different sizes can not be concurrently accommodated in the single tray member. Every time the size of the media sheets (on which an image forming or printing operation is to be performed) is changed to another size of those, the sheet tray device has to be removed from the main body of the image forming apparatus, for carrying out a sheet replacement operation, namely, for changing the media sheets with those of the other size. 
     That is, where the image forming operation is to be carried out on the media sheets of various sizes, the sheet replacement operation has to be frequently done. Since such a sheet replacement operation is generally cumbersome, the conventional image forming apparatus is poor in maneuverability, particularly, for a user who has to carry out the image forming operation on the media sheets of various sizes. 
     The above problem could be solved, for example, by employing an image forming apparatus such as large-sized copier machine equipped with a sheet tray device that has a plurality of trays for accommodating respective different sizes of media sheets. In the large-sized copier machine in which the media sheets of different sizes can be concurrently accommodated in the respective trays, the sheet replacement operation is not required every time the size of the media sheets is changed. However, the large-sized image forming apparatus is not feasible for a domestic use in which there is not a large space available for installation of the apparatus. 
     For solving the above problem, the present inventor manufactured, by way of trial, a double-deck sheet tray device including the conventional tray as a first tray for accommodating first size sheets, and a second tray for accommodating second size sheets whose size is smaller than that of the first size sheets, wherein the second tray is movably disposed on an upper side of the first tray. However, another problem is encountered in this double-deck sheet tray device. The problem is that refilling the first tray with the sheets could be made difficult by the arrangement in which the second tray is disposed to cover an upper opening of the first tray. 
     In view of this, in the double-deck sheet tray device manufactured by way of trial, the second tray is constituted by a support member and a supported body. The support member is arranged to bridge between opposite side walls of the first tray, while the supported body is supported by the support member and is pivotable to open and close the upper opening of the first tray. However, the double-deck sheet tray device suffers from still another problem that the second tray could be rotated relative to the first tray or removed from the first tray during movement of the second tray relative to the first tray. 
     SUMMARY OF THE INVENTION 
     The present invention was made in view of the background prior art discussed above. It is therefore a first object of the invention to provide a sheet tray device in which a second tray can be advantageously moved relative to a first tray without risk of rotation of the second tray relative to the first tray or removal of the second tray from the first tray. It is a second object of the invention to provide an image forming apparatus including the sheet tray device that provides the above technical advantage. The first object may be achieved according to a first aspect of the invention that is described below. The second object may be achieved according to a second aspect of the invention that is described below. 
     The first aspect of the invention provides a sheet tray device that is removably introduced into a main body of an image forming apparatus through an opening of the main body, so as to hold a media sheet that is to be supplied to an image forming unit of the image forming apparatus by which an image forming operation is performed on the media sheet. The sheet tray device includes: (a) a first tray accommodating a larger or first size sheet as the media sheet; and (b) a second tray disposed on an upper side of the first tray and accommodating a smaller or second size sheet as the media sheet. The second tray includes (b-1) a support member which bridges between opposite side walls of the first tray and which is movable relative to the opposite side walls, and (b-2) a supported body pivotably supported by the support member so as to open and close an upper opening of the first tray. Each of the opposite side walls of the first tray includes first and second rail portions that extend in a rail extending direction in which the support member is movable relative to the opposite side walls. The second rail portion is located on an upper side of the first rail portion and being spaced apart from the first rail portion. The support member of the second tray includes (i) a main slide portion that is slidably held in contact with an upper surface of the first rail portion, (ii) a removal-preventing slide portion that extends through a gap or space between the first and second rail portions so as to prevent removal of the support member of the second tray from the first tray, and (iii) a rotation-preventing slide portion that is slidably held in contact with an inside or outside surface of the first rail portion so as to prevent rotation of the support member of the second tray relative to the first tray. 
     In the sheet tray device constructed according to the first aspect of the invention, the main slide portion is slidably held in contact with the upper surface of the first rail portion, whereby the support member of the second tray is movably held by the first tray. 
     Further, since the removal-preventing slide portion extends through the space between the first and second rail portions, removal of the support member of the second tray from the first tray can be prevented by engagement of the removal-preventing slide portion with at least one of the first and second rail portions. 
     Moreover, since the rotation-preventing slide portion is slidably held in contact with the inside or outside surface of the first rail portion, it is possible to prevent rotation of the second tray relative to the first tray. 
     Therefore, in the present sheet tray device, it is possible to avoid problems such as rotation of the second tray relative to the first tray and removal of the second tray from the first tray, when the second tray is moved relative to the first tray. 
     It is noted that, in the present sheet tray device, the main slide portion and the rotation-preventing slide portion may be provided by either respective members that are independent from each other, or may be formed integrally with each other to be provided by a single common member. 
     It is further noted that, in the present sheet tray device, the first and second rail portions may be either offset or not offset from each other in a lateral direction in which the opposite side walls of the first tray are opposed to each other. 
     The second aspect of the invention provides an image forming apparatus including the sheet tray device defined in the first aspect of the invention, an image forming unit operable to perform an image forming operating on a media sheet, and a sheet supplying unit operable to supply the media sheet held by the sheet tray device, to the image forming unit. 
     In the image forming apparatus according to this second aspect of the invention, owing to incorporation of the sheet tray device defined in the first aspect of the invention, it is possible to enjoy the above-described technical advantages provided by the sheet tray device. That is, in the sheet tray device of the image forming apparatus, the second tray can be advantageously moved relative to the first tray without risk of rotation of the second tray relative to the first tray or removal of the second tray from the first tray. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features, advantages and technical and industrial significance of the present invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings, in which; 
         FIG. 1  is a perspective view of an image forming apparatus  100  that is constructed according to an embodiment of the present invention; 
         FIG. 2  is a side view partially in cross section of a sheet supplying unit  500  and an image forming unit  700  that are incorporated in the image forming apparatus  100  of  FIG. 1 ; 
         FIG. 3  is a perspective view of the sheet supplying unit  500  and a sheet tray device  300  that is to be removably introduced into the image forming apparatus  100  of  FIG. 1 , wherein the sheet tray device  300  includes a first tray  310  and a second tray  360 ; 
         FIG. 4  is an upper plan view of the sheet tray device  300  of  FIG. 3 ; 
         FIG. 5  is a perspective view of the sheet tray device  300  of  FIG. 3  when the second tray  360  has been forwardly moved relative to the first tray  310 ; 
         FIG. 6  is an upper plan view of the sheet tray device  300  of  FIG. 3  together with the sheet supplying unit  500  when the second tray  360  has been forwardly moved relative to the first tray  310 ; 
         FIG. 7  is a perspective view of the sheet tray device  300  of  FIG. 3  when an upper opening of the first tray  310  is exposed and an extension tray  350  is drawn out of the first tray  310 ; 
         FIG. 8  is a perspective view showing in enlargement a portion B of  FIG. 5 ; 
         FIG. 9  is a cross sectional view taken along line C-C of  FIG. 6 ; 
         FIG. 10  is a cross sectional view taken along line D-D of  FIG. 6 ; 
         FIG. 11  is a cross sectional view taken along line E-E of  FIG. 6 ; 
         FIG. 12  is a cross sectional view taken along line E-E of  FIG. 6  when the second tray  360  has been rearwardly moved relative to the first tray  310 ; 
         FIG. 13  is a perspective view of the sheet supplying unit  500  and the sheet tray device  300  of  FIG. 3  in absence of the second tray  360 ; 
         FIG. 14  is an upper plan view of the second tray  360 ; 
         FIG. 15  is a cross sectional view of a support member  361  of the second tray  360 , taken along line F-F of  FIG. 14 ; 
         FIG. 16  is a cross sectional view of a supported body  380  of the second tray  360 , taken along line F-F of  FIG. 14 ; 
         FIG. 17  is a cross sectional view of the support member  361  and the supported body  380  of the second tray  360 , taken along line F-F of  FIG. 14 ; 
         FIG. 18  is a cross sectional view of the support member  361  of the second tray  360 , taken along line G-G of  FIG. 14 ; 
         FIG. 19  is a cross sectional view of the supported body  380  of the second tray  360 , taken along line G-G of  FIG. 14 ; 
         FIG. 20  is a cross sectional view of the support member  361  and the supported body  380  of the second tray  360 , taken along line G-G of  FIG. 14 ; 
         FIG. 21  is a cross sectional view of the support member  361  and the supported body  380  of the second tray  360 , taken along line H-H of  FIG. 14 ; 
         FIG. 22  is a cross sectional view taken along line A-A of  FIG. 4 ; 
         FIG. 23  is a cross sectional view of the sheet supplying unit  500 ; 
         FIG. 24A  is a view showing a state in which a sheet supplying roller  600  (rotary shaft  650 ) is in parallel with axes of through-holes  551  of respective shaft supporting portions  550 ; 
         FIG. 24B  is a view showing another state in which the sheet supplying roller  600  (rotary shaft  650 ) is inclined with respect to the axes of the through-holes  551  of the respective shaft supporting portions  550 ; 
         FIGS. 25A-25C  are views showing an operation of a second coil spring  580 ; 
         FIG. 26A  is a view schematically showing a hinge  370  in the embodiment of the invention; 
         FIG. 26B  is a view schematically showing a C-type hinge; 
         FIG. 27  is a view showing a modification of the support member  361  of the second tray  360 ; and 
         FIG. 28  is a view showing another modification of the support member  361  of the second tray  360 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     There will be described an image forming apparatus  100  that is constructed according to an embodiment of the invention. The image forming apparatus  100  is a multi function device having various functions such as printer function, scanner function, color copier function and facsimile function. 
     1. Basic Construction of Image Forming Apparatus  100   
       FIG. 1  is a perspective view of the image forming apparatus  100 .  FIG. 2  is a side view partially in cross section of a sheet supplying unit  500  and an image forming unit  700  that are incorporated in the image forming apparatus  100  of  FIG. 1 . The image forming apparatus  100  has a main body in the form of a casing body  120  that is provided by a rectangular parallelepiped box-like body made of a resin. This apparatus  100  is installed for use, with its front portion and upper portion as seen in  FIG. 1  facing forwardly and upwardly, respectively. 
     An operator&#39;s control panel  110  is provided on an upper surface of a front portion of the casing body  120 , and includes an input portion  111  and a display portion  112 . The input portion  111  has various keys that are manually operable by an operator of the apparatus  100  to input various command signals for various operations to be performed by the apparatus  100 . The display portion  112  is provided for indicating a message and an image to provide the operator with information. 
     A scanner unit  200  is provided in an upper portion of the casing body  120  and is located on a rear side of the operator&#39;s control panel  110 , so as to read an image or script carried on an original. The scanner unit  200  serves as an image reader that is operable when the scanner function, color copy function or facsimile function is used. Since the scanner unit  200  has a known construction with an image pick-up device such as CCD and CIS, redundant description of the scanner unit  200  is not provided in the present specification. 
     As shown in  FIG. 2 , a sheet tray device  300  is provided in a lower portion of the casing body  120 , so as to hold or accommodate recording or media sheets such as paper sheets and OHP sheets that are superposed on each other. The sheet tray device  300  can be removed from the casing body  120  of the apparatus  100 , by forwardly and horizontally moving the tray device  300  out of the casing body  120  through an opening  121  that is provided in a front surface of the casing body  120 . The tray device  300  can be introduced into the casing body  120 , by rearwardly and horizontally moving the tray device  300  into the casing body  120  through the opening  121 . 
     A sheet supplying unit  500  is provided to feed or supply the media sheets stacked in the sheet tray device  300 , one after another, to the image forming unit  700 . The sheet supplying unit  500  is supported by a frame  122  (see  FIG. 2 ) that is fixed to the casing body  120 , so as to be located on an upper side of the sheet tray device  300 . 
     In a rear end portion of the casing body  120  that corresponds to a rear end portion of the sheet tray device  300 , a sheet feed path L is defined to interconnect the sheet tray device  300  and the image forming unit  700 . The sheet feed path L has a U-shaped cross sectional shape as seen in  FIG. 2 , so that each of the media sheets separated from the sheet tray device  300  is first moved in a rearward direction and is then moved in a forward direction. That is, the sheet feed path has a U turn portion by which a feed direction of each media sheet is changed from the rearward direction to the forward direction by substantially about 180°. 
     The image forming unit  700  is provided on an upper side of the sheet supplying unit  500 , so as to perform an image forming (printing) operation on each media sheet that has been fed (supplied) along the sheet feed path L. Each media sheet, after being subjected to the image forming operation, is discharged to a front portion of an upper surface of the sheet tray device  300 . Since the image forming unit  700  is of a known inkjet type and accordingly has a known construction, redundant description of the image forming unit  700  is not provided in the present specification. 
     2. Construction of Sheet Tray Device  300   
     2.0. Description of Drawing related to Sheet Tray Device  300   
       FIG. 3  is a perspective view of the sheet supplying unit  500  and the sheet tray device  300  in a state in which a second tray (sub tray)  360  is mounted on a first tray (main tray)  310 .  FIG. 4  is an upper plan view of the sheet tray device  300  in the same state as in  FIG. 3 .  FIG. 5  is a perspective view of the sheet tray device  300  in a state in which the second tray  360  is positioned in a front position relative to the first tray  310 . 
       FIG. 6  is an upper plan view of the sheet tray device  300  together with the sheet supplying unit  500  in the same state as in  FIG. 5 .  FIG. 7  is a perspective view of the sheet tray device  300  in a state in which an upper opening of the first tray  310  is exposed and an extension tray  350  is drawn out of the first tray  310 . 
       FIG. 8  is a perspective view showing in enlargement a portion B of  FIG. 5 .  FIG. 9  is a cross sectional view taken along line C-C of  FIG. 6 .  FIG. 10  is a cross sectional view taken along line D-D of  FIG. 6 .  FIG. 11  is a cross sectional view taken along line E-E of  FIG. 6 .  FIG. 12  is a cross sectional view taken along line E-E of  FIG. 6  in a state in which the second tray  360  is positioned in a rear position relative to the first tray  310 .  FIG. 13  is a perspective view of the sheet supplying unit  500  and the sheet tray device  300  without the second tray  360  being mounted on the first tray  310 . 
       FIG. 14  is an upper plan view of the second tray  360 .  FIG. 15  is a cross sectional view of a support member  361  of the second tray  360 , taken along line F-F of  FIG. 14 .  FIG. 16  is a cross sectional view of a main body (supported body)  380  of the second tray  360 , taken along line F-F of  FIG. 14 .  FIG. 17  is a cross sectional view taken along line F-F of  FIG. 14 . 
       FIG. 18  is a cross sectional view of the support member  361  of the second tray  360 , taken along line G-G of  FIG. 14 .  FIG. 19  is a cross sectional view of the main body  380  of the second tray  360 , taken along line G-G of  FIG. 14 .  FIG. 20  is a cross sectional view taken along line G-G of  FIG. 14 .  FIG. 21  is a cross sectional view taken along line H-H of  FIG. 14 .  FIG. 22  is a cross sectional view taken along line A-A of  FIG. 4 . 
     2.1. Basic Construction of Sheet Tray Device  300   
     The sheet tray device  300  is provided to hold or accommodate the media sheets that are to be supplied to the image forming unit  700 . As shown in  FIG. 3 , the sheet tray device  300  includes the first tray  310  provided by a rectangular parallelepiped plate-like body that has an upper opening, the second tray  360  disposed on an upper side of the first tray  310  so as to cover a part of the upper opening of the first tray  310 , and the extension tray  350  movably attached to the first tray  310 . The extension tray  350  is movable relative to the first tray  310  in forward and rearward directions that are parallel to tray-device introduction and removal directions in which the sheet tray device  300  is introducible into and removable from the casing body  120  of the image forming apparatus  100 . 
     2.2. Construction of First Tray  310   
     As shown  FIG. 13 , the first tray  310  is provided by the thin plate-like body having the rectangular parallelepiped shape. In the present embodiment, the first tray  310  has a size which permits A4-sized papers to be accommodated therein as maximum-sized media sheets when the extension tray  350  is not drawn out thereof, and which permits legal-sized papers to be accommodated therein as maximum-sized media sheets when the extension tray  350  is drawn out thereof. 
     The first tray  310  includes a bottom portion  311  (hereinafter referred to as bottom wall  311 ), and opposite side walls  312  which are located on respective end portions (i.e., right and left end portions in the present embodiments) of the first tray  310  that are opposite to each other in a horizontal direction perpendicular to the above-described tray-device introduction and removal directions. The opposite side walls  312  project upwardly from the bottom wall  311 , and is elongated in the tray-device introduction and removal directions. In the present embodiment, the opposite side walls  312  and the bottom wall  311  are integrally formed of a resin. 
     A pair of guide members  313  are provided in the bottom wall  311  of the first tray  310 , and are arranged to be movable in respective opposite directions that are parallel to a lateral direction of the sheet tray device  300  in which the opposite side walls  312  are opposed to each other (i.e., in respective opposite directions corresponding to right and left directions in the present embodiment). The pair of guide members  313  are movable together with each other in respective opposite directions, so that a center between the guide members  313  always lies in a constant position (i.e., in a laterally central portion of the sheet tray device  300  in the present embodiment), irrespective of positions of the guide members  313 . 
     As shown in  FIG. 13 , each of the guide members  313  includes a bottom plate portion  314  on which the media sheets are to be mounted, a side plate portion  315  which extends vertically upwardly from a laterally outer end of the bottom plate portion  314 , and a linear guide bar portion  316  which extends from a bottom surface of the bottom plate portion  314  toward the other of the guide members  313 . 
     The linear guide bar portions  316  of the respective guide members  313  are in parallel to each other and are spaced apart from each other in a longitudinal direction of the sheet tray device  300  (corresponding to the sheet feed direction), and are slidably fitted in respective grooves  317  that are formed in the bottom wall  311  of the first tray  310  and extend in the lateral direction. Each of the linear guide bar portions  316  has teeth (not shown) formed in its surface opposed to a surface of the other of the linear guide bar portions  316 , so as to serve as a rack. 
     The linear guide bar portions  316 , which serve as the racks, mesh with a pinion (not shown) that is rotatably disposed in a laterally central portion of the bottom wall  311 . Thus, the pair of guide members  313  are mechanically connected to each other through the pinion, so as to be slidable or movable in the respective opposite directions such that the center between the guide members  313  always lies in the constant position. 
     The side plate portion  315  of each of the guide members  313  has a contact surface that is to be in contact with a corresponding one of widthwise opposite ends of each media sheet. The contact surface of the side plate portion  315  is provided by a flat surface that is parallel to the longitudinal direction of the sheet tray device  300 . Thus, each media sheet is fed to the sheet feed path L to be supplied to the image forming unit  700  while widthwise opposite ends of each media sheet are being positioned by the guide members  313 . 
     The first tray  310  further includes a slant plate portion  318  that is provided in its rear end portion, i.e., its lower stream end portion as viewed in the sheet feed direction. The slant plate portion  318  is inclined for converting the feed direction of the media sheet (that is given a feed force by the sheet supplying unit  500 ) into an upward direction. A separator  319  is provided in a laterally central portion of the slant plate portion  318 . 
     The separator  319  is constituted by a plurality of metallic protrusions which are vertically arranged at a certain pitch and which slightly protrude from a front surface of the slant plate portion  318 . Owing to the separator  319 , when the media sheets are pressed onto the slant plate portion  318  by the sheet supplying unit  500 , the media sheets are brought into contact at their leading ends with distal ends of the respective protrusions of the separator  319 . In this instance, the media sheet brought into contact with the protrusions of the separator  319  receive resistance acting against their feed movements, and an uppermost one of the media sheets is separated from the other media sheets so as to be moved toward the image forming unit  700 . Thus, the media sheets are supplied, one after another, to the image forming unit  700 . 
     Each of the opposite side walls  312  of the first tray  310  includes first and second rail portions  320 ,  325  that are provided in its portion close to the slant plate portion  318 , as shown in  FIG. 8 , for movably supporting the second tray  360 . The first and second rail portions  320 ,  325  extend in a rail extending direction (i.e., the longitudinal direction of the sheet tray device  300 ) in which the second tray  360  is movable relative to the first tray  310 , as shown in  FIG. 8 . The second rail portion  325  is located on an upper side of the first rail portion  320 , and is spaced apart from the first rail portion  320  in a vertical direction (that is perpendicular to the lateral direction and the rail extending direction). The first and second rail portions  320 ,  325  are offset from each other in the lateral direction, and do not overlap with each other as seen in the vertical direction. 
     Since the first and second rail portions  320 ,  325  do not overlap with each other as seen in the vertical direction, an upper portion of each side wall  312  located on an upper side of an upper end of the first rail portion  320  and a lower portion of each side wall  312  located on a lower side of a lower end of the second rail portion  325  are separated from each other. 
     Therefore, where the opposite side walls  312  (each including the first and second rail portions  320 ,  325 ) and the bottom wall  311  are to be integrally formed of a resin in an injection molding using upper and lower mold halves, there is a risk that it is impossible to form a portion of each side wall  312  interconnecting the above-described upper and lower portions of the side wall  312 . 
     In the present embodiment, for solving such an inconvenience, each of the opposite side walls  312  of the first tray  310  further includes a plurality of interconnecting portions  329  which interconnect the first and second rail portions  320 ,  325 , as shown in  FIG. 8 . The interconnecting portions  329  are spaced apart from each other in the longitudinal direction of the sheet tray device  300 , and are disposed in a region L 1  of each side wall  312  throughout which the first rail portion  320  extends in the longitudinal direction. This region L 1  of each side wall  312  corresponds to a range L 1  within which the second tray  360  (support member  361 ) is movable relative to the first tray  310 . 
     Each of the interconnecting portions  329  includes a portion which bridges the upper and lower portions of the side wall  312  and which is located on a laterally outside of the second rail portion  325 , as shown in  FIG. 5 , so as to interconnect the first and second rail portions  320 ,  325 . 
     The extension tray  350  is attached to the first tray  310 , movably relative to the first tray  310  in the rail extending direction (i.e., the longitudinal direction of the sheet tray device  300 ), as shown in  FIGS. 7 and 13 . The extension tray  350  can be drawn out of the first tray  310 , by moving the extension tray  350  in the forward direction relative to the first tray  310 . The extension tray  350  can be introduced into the first tray  310 , by moving the extension tray  350  in the rearward direction relative to the first tray  310 . The extension tray  350  has opposite side walls  351  each of which is slidably accommodated in a sheath-shaped accommodating portion  330  of a corresponding one of the opposite side walls  312  of the first tray  310 . The accommodating portion  330  is provided by a front region L 2  of each side wall  312 . 
     Each of the opposite side walls  312  of the first tray  310  has a cutout  332 , as shown in  FIGS. 9 and 13 , which is provided for facilitating an operation to move the guide members  313 . The cutout  332  is located between the above-described regions L 1 , L 2  as viewed in the rail extending direction. Specifically, the cutout  332  is located on a downstream side of the region L 1  and on an upstream side of the region L 2 , as viewed in the sheet feed direction. 
     2.3. Construction of Second Tray  360   
     The second tray  360  is provided to accommodate the media sheets whose size is smaller than a size of the media sheets accommodated in the first tray  310 . Specifically, the second tray  360  is designed to accommodate envelops or postal cards as the smaller-sized media sheets. 
     As shown in  FIG. 7 , the second tray  360  includes the support member  361  which extends in the lateral direction so as to bridge between the opposite side walls  312  of the first tray  310  and which is movable relative to the opposite side walls  312  in the rail extending direction, and the main body  380  pivotably supported by the support member  361 . The second tray  360  further includes a hinge  370  through which the main body  380  is pivotable relative to the support member  361  so as to open and close the upper opening of the first tray  310 . 
     2.3.1. Detailed Description of Second Tray  360   
     The support member  361  of the second tray  360  includes engaged portions at which the support member  361  is engaged with the opposite side walls  312  of the first tray  310 . As shown in  FIG. 22 , each of the engaged portions of the support member  361  includes a main slide portion  362  that is slidably held in contact with an upper surface  321  of the first rail portion  320 , a removal-preventing slide portion  363  that extends through a space between the first and second rail portions  320 ,  325  in a direction perpendicular to the rail extending direction (i.e., in the lateral direction of the sheet tray device  300  in the present embodiment) so as to prevent removal of the support member  361  of the second tray  360  from the first tray  310 , and a rotation-preventing slide portion  364  that is slidably held in contact with an inside surface  322  of the first rail portion  320  so as to prevent rotation of the support member  361  of the second tray  360  relative to the first tray  310 . 
     The support member  361  of the second tray  360  further includes an extending wall portion  365  which extends from the removal-preventing slide portion  363  and which is located on the side of an outside surface  323  of the first rail portion  320 . The extending wall portion  365  cooperates with the rotation-preventing slide portion  364  to interpose the first rail portion  320  therebetween in the lateral direction. In the present embodiment, the extending wall portion  365  and the removal-preventing slide portion  363  are integrated with each other. The extending wall portion  365  has an opposed surface which is opposed to the first rail portion  325  in the lateral direction, and which is inclined such that a distance between the opposed surface and the first rail portion  320  increases in a downward direction away from the upper surface  321  of the first rail portion  320 . 
     In the present embodiment, the removal-preventing slide portion  363  is formed integrally with the main slide portion  362 , and extends from the main slide portion  362  in a laterally outward direction, i.e., in a leftward direction as seen in  FIG. 22 . The extending wall portion  365  is formed integrally with the main slide portion  362 , and projects downwardly from a distal end of the removal-preventing slide portion  363 . The rotation-preventing slide portion  364  is formed integrally with the main slide portion  362 , and projects downwardly from a proximal end of the main slide portion  362 . 
     As shown in  FIG. 9 , the rotation-preventing slide portion  364  of the support member  361  has a length D 1  as measured in the rail extending direction, while the support member  362  as a whole has a length D 2  as measured in the rail extending direction, such that the length D 1  and the length D 2  are substantially equal to each other. 
     The above-described region or range L 1 , within which the support member  361  of the second tray  360  is movable relative to the first tray  310 , is determined such that the support member  361  is positioned in a position that is distant from an operational region of the sheet supplying unit  500  when the media sheets accommodated in the first tray  310  are supplied to the image forming unit  700  by the sheet supplying unit  500 , as shown in  FIG. 11 . 
     On the other hand, when the media sheets accommodated in the second tray  360  are supplied to the image forming unit  700  by the sheet supplying unit  500 , as shown in  FIG. 12 , the support member  361  is positioned in the vicinity of the sheet supplying unit  500 . 
     2.3.2. Detailed Description of Hinge  370   
     As shown in  FIGS. 15 and 18 , the hinge  370  includes a shaft portion  371  which is provided in the support member  361 , and first and second bearing portions  376 ,  377  which are provided in the main body  380  and which cooperate with each other to support the shaft portion  371 . The first and second bearing portions  376 ,  377  are rotatably held in contact with an outer circumferential surface of the shaft portion  371 . 
     As shown in  FIGS. 17 and 20 , the first and second bearing portions  376 ,  377  are located on respective opposite sides of the shaft portion  371  in a diametrical direction of the shaft portion  371 . In the present embodiment, the first bearing portions  376  are located on an upper side of the shaft portion  371  (see  FIG. 17 ) while the second bearing portions  377  are located on a lower side of the shaft portion  371  (see  FIG. 20 ). 
     The first and second bearing portion  376 ,  377  are offset from each other in an axial direction of the shaft portion  371 , such that each first bearing portion  376  is located between two second bearing portions  377  in an axial direction of the shaft portion  371 . 
     The shaft portion  371  includes a small diameter portion  372  having a radius R 1  (see  FIG. 15 ) and a large diameter portion  373  having a radius R 2  (see  FIG. 18 ) that is smaller than the radius R 1 . The small diameter portion  372  and the large diameter portion  373  are arranged to be contactable with the first bearing portion  376  and the second bearing portion  377 , respectively. 
     In the present embodiment, the first diameter portion  372  and the second diameter portion  373  are arranged to be coaxial with each other. The small diameter portion  372  has an axial length D 3  that is smaller than an axial length D 4  of the large diameter portion  373 , as shown in  FIG. 14 . 
     Further, the small diameter portion  372  and the large diameter portion  373  are not completely circular in cross section. Rather, the small diameter portion  372  has an arcuate cross section only in its upper portion that is contactable with the first bearing portion  376  (see  FIG. 15 ), while the large diameter portion  373  has an arcuate cross section only in its lower portion that is contactable with the second bearing portion  377  (see  FIG. 18 ). 
     The hinge  370  further includes a removal preventer portion  378  that is provided in the second bearing portion  377  so as to prevent removal of the shaft portion  371  from the first and second bearing portions  376 ,  377 , as shown in  FIGS. 16 and 19 . Specifically, the removal preventer portion  378  is located between the first and second bearing portions  376 ,  377  in a circumferential direction of the shaft portion  371 , for preventing removal of the shaft portion  371  through a space between the first and second bearing portions  376 ,  377  in the circumferential direction. The removal preventer portion  378  is provided by a projecting portion of the main body  380  of the second tray  360 , and projects from a surface contiguous to a sliding contact surface S 1  of the second bearing portion  377  at which the second bearing portion  377  is to be contact with the shaft portion  371 . 
     In the present embodiment, a front surface of the removal preventer portion  378 , which faces the shaft portion  371  to be contactable with the shaft portion  371 , is substantially perpendicular to the above-described surface contiguous to the sliding contact surface S 1 , while a rear surface of the removal preventer portion  378  is inclined with respect to the front surface of the removal preventer portion  378  such that a cross section of the removal preventer portion  378  reduces in an upward direction toward a distal end of the removal preventer portion  378 , as shown in  FIGS. 16 and 19 . 
     The inclination of the rear surface of the removal preventer portion  378  facilitates an operation to attach the main body  380  to the support member  361 , since the above-described inclined rear surface of the removal preventer portion  378  serves as a guide surface so as to cause the removal preventer portion  378  to be elastically deformed upon introduction of the shaft portion  371  into a space surrounded by the first and second bearing portions  376 ,  377 . 
     In an assembled state in which the shaft portion  371  is introduced into the space surrounded by the first and second bearing portions  376 ,  377 , as shown in  FIGS. 17, 19 and 20 , the first and second bearing portions  376 ,  377  are located on respective opposite sides of the shaft portion  371  in a diametrical direction of the shaft portion  371 , while the removal preventer portion  378  and an end face of the main body  380  of the second tray  360  (that is close to proximal ends of the first and second bearing portions  376 ,  377 ) are located on respective opposite sides of the shaft portion  371  in another diametrical direction that is perpendicular to the above-described diametrical direction. 
     The hinge  370  further includes a stopper portion  379  that is provided in the second bearing portion  377 , so as to define a maximum angle by which the main body  380  of the second tray  360  is pivotable relative to the first tray  310 . The stopper portion  379  projects from one of opposite side surfaces of a distal end portion of the second bearing portion  377  (which one is remote from the removal preventer portion  378 ), and is to be brought into contact with a part of the support member  361  so as to limit a pivot motion of the main body  380  of the second tray  360  in a direction away from the first tray  310 . 
     3. Construction of Sheet Supplying Unit  500   
       FIG. 23  is a cross sectional view of the sheet supplying unit  500 .  FIGS. 24A and 24B  are cross sectional views of the sheet supplying roller  600 , wherein  FIG. 24A  shows a state in which a rotary shaft  650  of the sheet supplying roller  600  is in parallel with axes of through-holes  551  of respective shaft supporting portions  550  (which are aligned with each other), while  FIG. 24B  shows another state in which the rotary shaft  650  of the sheet supplying roller  600  is inclined with respect to the axes of the through-holes  551 .  FIGS. 25A-25C  are views showing an operation of a second coil spring  580 . 
     The sheet supplying unit  500  is a mechanism that is arranged to apply the feed force to the media sheets accommodated in the first and second trays  310 ,  360  of the sheet tray device  300  so as to feed or supply the media sheets to the image forming unit  700 . As shown in  FIG. 3 , the sheet supplying unit  500  is rockably or pivotably supported by a support shaft  510  which is located on an upper side of the sheet tray device  300  and which extends from a laterally central portion of the casing body  120  of the image forming apparatus  100  toward one of laterally opposite ends of the casing body  120  (toward a right end of the casing body  120  in the present embodiment). 
     The support shaft  510  is held by a metal frame  122  (see  FIG. 2 ). A component of an external force exerted to the support shaft  510 , which component acts in a radial direction of the support shaft  510 , is received primarily by the metal frame  122 . Meanwhile, the support shaft  510  primarily transmits or receives a torque acting on the support shaft  510 . 
     A large gear  530  is mounted on one of axially opposite end portions of the support shaft  510  (that corresponds to a right end of the sheet tray device  300  in the present embodiment), so as to transmit a rotational force (generated by a drive source) to the support shaft  510 . A small gear  540  (see  FIG. 23 ) is mounted on the other of the axially opposite end portions of the support shaft  510  (that corresponds to a laterally central portion of the sheet tray device  300  in the present embodiment), so as to be rotated integrally with the support shaft  510 . 
     A roller arm  520  is provided by a member which is rotatably attached to the support shaft  510  and which extends in a radial direction of the support shaft  510 . The sheet supplying roller  600 , which is rotatable about an axis of the rotary shaft  650 , is held by a distal end portion of the roller arm  520  (see  FIG. 24 ). In this arrangement, when the roller arm  520  is pivoted about an axis of the support shaft  510  in a direction toward the bottom wall  311  of the first tray  310 , i.e., toward the media sheets, the sheet supplying roller  600  is pressed against the media sheets, namely, there is generated a pressing force forcing the sheet supplying roller  600  onto the media sheets. 
     The sheet supplying roller  600  is rotated while being held in contact with an uppermost one of the media sheets stacked in the sheet tray device  300 , so as to apply the feed force to the uppermost one of the media sheets. As shown in  FIG. 24 , the sheet supplying roller  600  includes a cylindrical main body  610  and a pair of roller members  620  that are mounted on respective axially opposite end portions of the main body  610 . 
     In the present embodiment, the cylindrical main body  610  is made of a hard synthetic resin, while each of the roller members  620  is made of a rubber or the like which is elastically deformable and which has a high coefficient of friction. The cylindrical main body  610  includes a pair of roller supporting portions  630 ,  640  on which the respective roller members  620  are mounted, a gear contact portion  651  provided in an axially central portion of the rotary shaft  650  that interconnects the roller supporting portions  630 ,  640 , and a pair of arm contact portions  652  provided in respective portions of the rotary shaft  650  that are located on respective opposite sides of the axially central portion of the rotary shaft  650 . 
     The rotary shaft  650  has a generally cross shape in its transversal cross section, as shown in  FIG. 23 . The gear contact portion  651  is provided by a cylindrical portion and protruding portions, wherein the cylindrical portion has a diameter that is larger than a maximum size of the rotary shaft  650  while the protrusion portions protrude radially outwardly from respective diametrically opposite ends of the cylindrical portion. Each of the arm contact portions  652  is provided by a cylindrical portion having a diameter that is larger than the maximum size of the rotary shaft  650 . 
     The shaft support portions  550  are provided by the distal end portion of the roller arm  520 , and define the respective through-holes  551 , as shown in  FIGS. 24A and 24B . The rotary shaft  650  is introduced in the through-holes  551  that are coaxial with each other, so as to be rotatably held by the shaft support portions  550 . 
     Each of the arm contact portions  652 , which are located on respective opposite sides of the gear contact portion  651 , is slidably contacted at its outer circumferential surface with an inner circumferential surface of a corresponding one of the through-holes  551 , so that the rotary shaft  650  is rotatably held by the shaft support portions  550 . Since the diameter of the arm contact portions  652  is slightly smaller than an inside diameter of the through-holes  551 , the rotary shaft  650  is rotatable even in the state, as shown in  FIG. 24B , in which the rotary shaft  650  is inclined with respect to the axes of the through-holes  551 . 
     A gear  660  is provided between the two shaft support portions  550  of the roller arm  520 , rotatably relative to the roller arm  520 , so as to transmit a drive force to the sheet supplying roller  600  (rotary shaft  650 ). The gear contact portion  651  is located within a through-hole  661  that is formed through an axis of the gear  660  (about which the gear  660  is rotatable). 
     In an inner circumferential surface of the through-hole  661 , fan-shaped grooves are formed to receive therein the above-described protruding portions of the gear contact portion  651 . That is, the gear contact portion  651  is fitted at its protruding portions in the grooves of the inner circumferential surface of the through-hole  661 , so that the gear  660  and the gear contact portion  651  are held in engagement with each other. 
     In the present embodiment, a length of each of the fan-shaped grooves as measured in a circumferential direction of the through-hole  661  is larger than a length of a corresponding one of the protruding portions of the gear contact portion  651  as measured in a circumferential direction of the gear contact portion  651 , so that there is a play between each fan-shaped groove and the corresponding protruding portion, which allows the gear  660  to be rotated relative to the gear contact portion  651  by a predetermined degree of angle (by about 60° in the present embodiment). 
     The roller arm  520  has a plurality of intermediate gears  560  incorporated therein to transmit the drive force from the small gear  540  (fixed to the support shaft  510 ) to the gear  660 . The intermediate gears  560  are arranged in a direction in which the roller arm  520  extends, as shown in  FIG. 23 . 
     The number of the intermediate gears  560  is determined such that a direction of tangent line between the sheet supplying roller  600  and an uppermost one of the stacked media sheets coincides with the feed direction of each of the media sheets when the roller arm  520  is pivoted in a direction causing its distal end portion to be displaced toward the media sheets (bottom wall  311 ) by rotating the support shaft  510  (small gear  540 ) in a direction indicated by arrow in  FIG. 23 . 
     As the drive force is applied to the sheet supplying roller  600 , the feed force is given to the uppermost media sheet, while the roller arm  520  is forced by a reaction acting on the sheet supplying roller  600  to be pivoted toward the media sheet. Therefore, the feed force is reliably given to the media sheet from the sheet supplying roller  600  to which the drive force is applied, without separation of the sheet supplying roller  600  from the media sheet. 
     In the above-described arrangement in which the sheet supplying roller  600  is pressed onto the stacked media sheets by utilizing the reaction against the drive force that causes rotation of the sheet supplying roller  600 , the pressing force (by which the roller  600  is pressed on the media sheets) is easily changeable, and is not generated, particularly, in a stage of initiation of feed of the media sheets in which the drive force is not yet applied to the sheet supplying roller  600 . 
     In the present embodiment, as shown in  FIG. 3 , a first torsion coil spring  570  is disposed on the side of the support shaft  510  so as to constantly generate an elastic force that forces the roller arm  520  to be pivoted toward the media sheets, while the above-described second torsion coil spring  580  is disposed on the side of the distal end portion of the roller arm  520  so as to generate an elastic force that forces the roller arm  520  to be pivoted toward the media sheets. 
     The second torsion coil spring  680  is held in contact with a contact member  123  provided in the frame  122  so as to be elastically deformed, when an angle defined by the roller arm  520  and the uppermost media sheet is small, namely, when the roller arm  520  extends substantially in a horizontal direction, as shown  FIGS. 25B and 25C . In this instance, the roller arm  520  is pressed (biased) toward the media sheets, owing to the elastic deformation of the second torsion coil spring  580 . It is noted that the uppermost media sheet is represented by one-dot chain line in  FIGS. 25B and 25C . 
     On the other hand, when the angle defined by the roller arm  520  and the uppermost media sheet is large, as shown in  FIG. 25A , the second torsion coil spring  580  is separated from the contact member  123 , so that the second torsion coil spring  580  does not generate the elastic force that forces the roller arm  520  toward the media sheets. That is, the second torsion coil spring  580  presses (biases) the roller arm  520  toward the media sheets, only when the roller arm  520  is substantially parallel to the horizontal direction. 
     4. Characteristics of Image Forming Apparatus 
       FIG. 26A  is a view schematically showing the hinge  370  in the present embodiment of the invention.  FIG. 26B  is a view schematically showing a C-type hinge in which a shaft portion is fitted in a bearing portion that has a letter C shape. 
     As shown in  FIG. 26A , the hinge  370  has a height or thickness H 1  that is equal to a sum of a distance R 1  between an axis of the small diameter portion  372  and the first bearing portion  376 , a height or thickness T 1  of the first bearing portion  376 , a distance R 2  between an axis of the large diameter portion  373  and the second bearing portion  377  and a height or thickness T 2  of the second bearing portion  377 . 
     On the other hand, as shown in  FIG. 26B , the C-type hinge has a height or thickness H 2  that is equal to a sum of a height or thickness T 3  of a part of the bearing portion at which the bearing portion is in contact with one of diametrically opposite ends of the shaft portion  371 , a height or thickness T 4  of another part of the bearing portion at which the bearing portion is in contact with the other of the diametrically opposite ends of the shaft portion  371  and a diameter R 3  of the shaft portion  371 . 
     Therefore, the height or thickness H 1  of the hinge  370  in the present embodiment is smaller than the height or thickness H 2  of the C-type hinge, as long as a radius of the shaft portion  371  of the C-type hinge is equal to a radius of the large diameter portion  373  of the shaft portion  371  of the hinge  370  in the present embodiment, and a sum of the height or thickness T 1  of the first bearing portion  376  and the height or thickness T 2  of the second bearing portion  377  is equal to a sum of the height or thickness T 3  of the part of the bearing portion at which the bearing portion is in contact with the above-described one of the diametrically opposite ends of the shaft portion  371  and the height or thickness T 4  of the above-described another part of the bearing portion at which the bearing portion is in contact with the above-described other of the diametrically opposite ends of the shaft portion  371 . 
     That is, H 1 =R 1 +R 2 + 2 ×t and H 2 = 2 ×R 2 + 2 ×t, when T 1 =T 2 =T 3 =T 4 =t and R 3 = 2 ×R 2 . Therefore, the height (thickness) H 1  of the hinge  370  in the present embodiment is smaller than the height (thickness) H 2  of the C-type hinge. 
     Further, in the present embodiment, the shaft portion  371  is interposed between the first and second bearing portions  376 ,  377 , and is prevented by the removal preventer portion  378  from being removed from the first and second bearing portions  376 ,  377 , whereby removal of the main body (supported body)  380  from the support member  361  is reliably prevented. 
     Therefore, in present embodiment, the hinge  370  can be made small in size whereby the sheet tray device  300  as a whole can be made compact in size, while the removal of the main body (supported body)  380  from the support member  361  is reliably prevented. 
     Since the radius R 1  of the small diameter portion  372  is smaller than the radius R 2  of the large diameter portion  373 , the smaller diameter portion  372  has a rigidity smaller than that of the large diameter portion  373 . In general, a portion having a smaller rigidity is likely to surfer from a fatigue fracture before a portion having a large rigidity suffers from it. 
     However, in the present embodiment, since the axial length D 3  of the small diameter portion  372  is smaller than the axial length D 4  of the large diameter portion  373 , it is possible to prevent the fatigue fracture of the small diameter portion  372  from taking place before that of the large diameter portion  373 . 
     Further, in the present embodiment, the hinge  370  includes the stopper portion  379  for defining the maximum angle by which the main body  380  of the second tray  360  is pivotable relative to the first tray  310 . The provision of the stopper portion  379  is effective to prevent problems such as breakage of the hinge  370  (that could be caused if the main body  380  were pivoted by an excessively large angle) and removal of the main body  380  from the support member  361 . 
     Further, in the present embodiment, the main slide portion  362  is slidably held in contact with the upper surface of the first rail portion  362 , as shown in  FIG. 22 , whereby the support member  361  of the second tray  360  is movably held by the first tray  310 . 
     Further, since the removal-preventing slide portion  363  extends through the space between the first and second rail portions  320 ,  325 , removal of the support member  361  of the second tray  360  from the first tray  310  can be prevented by engagement of the removal-preventing slide portion  363  with at least one of the first and second rail portions  320 ,  325 . 
     Moreover, since the rotation-preventing slide portion  364  is slidably held in contact with the inside surface  322  of the first rail portion  320 , it is possible to prevent rotation of the second tray  360  relative to the first tray  310 . 
     Therefore, in the sheet tray device  300  in the present embodiment, it is possible to avoid problems such as rotation of the second tray  360  relative to the first tray  310  and removal of the second tray  360  from the first tray  310 , when the second tray  360  is moved relative to the first tray  310 . 
     In the present embodiment, the first tray  310  including the opposite side walls  312  is a product that is formed of a resin according to a forming process (e.g., injection molding) using molds. Therefore, if the first and second rail portions  320 ,  325  were positioned relative to each other to overlap with each other as seen in the vertical direction, it would be necessary to use, in addition to the upper and lower mold halves, a core (insert) or a slide mold, for obtaining the space between the first and second rail portions  320 ,  325 . 
     Thus, if the first and second rail portions  320 ,  325  were arranged to overlap with each other as seen in the vertical direction, the required cost for the mold assembly and the efficiency in the forming process would be increased and reduced, respectively, possibly resulting in a considerable increase in the cost of manufacturing the first tray  310  (sheet tray device  300 ). 
     In the present embodiment, the first and second rail portions  320 ,  325  are offset from each other in the lateral direction, and do not overlap with each other as seen in the vertical direction, thereby making it possible to obtain the space between the first and second rail portions  320 ,  325  in the forming process using the upper and lower mold halves without the core (insert) or slide mold. 
     It is therefore possible to avoid the increase in the required cost for the mold assembly and the reduction in the efficiency in the forming process, thereby preventing the increase in the cost of manufacturing the first tray  310  (sheet tray device  300 ). 
     However, in the arrangement in which the first and second rail portions  320 ,  325  are offset from each other in the lateral direction, the removal-preventing slide portion  363  are contactable, at its contact regions that are offset from each other in the lateral direction, with the respective first and second rail portions  320 ,  325 . Since the contact regions of the removal-preventing slide portion  363  contactable with the respective first and second rail portions  320 ,  325  are offset from each other in the lateral direction, the removal-preventing slide portion  363  is likely to receive a bending moment such that the contact region contacted with the first rail portion  320  acts as a fulcrum while the contact region contacted with the second rail portion  325  acts as a point of action. 
     If the removal-preventing slide portion  363  is considerably deformed or bent as a result of application of the bending moment thereto, there is a risk that the removal-preventing slide portion  363  could be removed through the space between the first and second rail portions  320 ,  325 , and accordingly the support member  361  could be removed from the first tray  310 . 
     In the present embodiment, however, the extending wall portion  365  is provided to extend from the removal-preventing slide portion  363  such that the first rail portion  320  is located between the extending wall portion  365  and the rotation-preventing slide portion  364  in the lateral direction. When the bending moment acts on the removal-preventing slide portion  363 , the extending wall portion  365  is brought into contact with the outside surface  323  of the first rail portion  320 , so as to serve as a stopper or restrainer for restraining deformation of the removal-preventing slide portion  363 . 
     Therefore, even when the bending moment is applied to the removal-preventing slide portion  363 , it is possible to prevent considerable deformation of the removal-preventing slide portion  363 , and accordingly avoid removal of the removal-preventing slide portion  363  from through the space between the first and second rail portions  320 ,  325 . 
     As is clear from the above description, in the present embodiment, it is possible to restrain increase in the cost required for manufacturing the sheet tray device  300  while preventing the support member  361  of the second tray  360  being removed from the first tray  310 . 
     The above-described bending moment can be reduced with reduction in an amount of offset of the first and second rail portions  320 ,  325  from each other in the lateral direction in which the opposite side walls  312  are opposed to each other. However, the reduction in the offset amount makes it difficult to attach the support member  361  to the opposite side walls  312 , since the extending wall portion  365  has to pass through the space between the first and second rail portions  320 ,  325  that is small in its cross section that is perpendicular to the vertical direction. 
     In view of such a difficulty, in the present embodiment, the opposed surface of the extending wall portion  365  (that is opposed to the first rail portion  325  in the lateral direction) is inclined with respect to the vertical direction such that the distance between the opposed surface and the first rail portion  320  increases in the downward direction away from the upper surface  321  of the first rail portion  320 . The inclination of the opposed surface of the extending wall portion  365  facilitates an operation to cause the extending wall portion  365  to pass through the space between the first and second rail portions  320 ,  325 , since the above-described inclined opposed surface of the extending wall portion  365  serves as a guide surface. Thus, the extending wall portion  365  can be easily caused to pass through the space between the first and second rail portions  320 ,  325 , even where the above-described offset amount is small. 
     Therefore, without making it difficult to attach the support member  361  to the opposite side walls  312 , it is possible to reliably prevent removal of the support member  361  from the first tray  310  due to the bending moment acting on the removal-preventing slide portion  363 . 
     In the present embodiment, the cutout  332  is formed in a portion of each of the opposite side walls  312  that is located in a front side of the above-described region or range L 1  within which the second tray  360  (support member  361 ) is movable relative to the first tray  310 , so that the range of the movement of the second tray  360  is not limited by the presence of the cutout  332 . 
     Further, the above-described region or range L 1  is determined such that the support member  361  is positioned in the position that is distant from the operational region of the sheet supplying unit  500  when the media sheets accommodated in the first tray  310  are supplied to the image forming unit  700  by the sheet supplying unit  500 , so that the sheet supplying unit  500  is prevented from being interfered by the support member  361 . 
     While the presently preferred embodiment of the invention has been described above in detail, it is to be understood that the invention is not limited to the details of the illustrated embodiment, but may be otherwise embodied without departing from the spirit of the invention. 
     For example, the arrangement for connection of the support member  361  with each of the opposite side walls  312  is not limited to details shown in  FIG. 22 , and may be modified as shown in  FIG. 27  in which the extending wall portion  365  is not provided, or may be modified as shown in  FIG. 28  in which the opposed surface of the extending wall portion  365  (opposed to the first rail portion  325 ) is not inclined with the respect to the vertical direction. 
     Further, in the above-described embodiment, the main slide portion  362 , removal-preventing slide portion  363  and rotation-preventing slide portion  364  are located in substantially the same position in the rail extending direction, namely, these portions  362 ,  363 ,  364  can be represented by a single cross section perpendicular to the rail extending direction. However, these portions  362 ,  363 ,  364  may be offset from each other in the rail extending direction. 
     Further, while the first and second rail portions  320 ,  325  are offset from each other in the lateral direction in the above-described embodiment, the first and second rail portions  320 ,  325  does not necessarily have to be offset from each other but may overlap with each other as seen in the vertical direction. 
     In the above-described embodiment, the extending wall portion  365  is positioned outside the first rail portion  320  while the rotation-preventing slide portion  364  are positioned inside the first rail portion  320 . However, the extending wall portion  365  and the rotation-preventing slide portion  364  may be positioned inside and outside the first rail portion  320 , respectively. 
     While the axial length D 3  of each small diameter portion  372  is smaller than the axial length D 4  of each large diameter portion  373  in the present embodiment, the axial length D 3  of the small diameter portion  372  may be equal to or larger than the axial length D 4  of the large diameter portion  373 . 
     While each small diameter portion  372  is located between two large diameter portions  373  in the above-described embodiment, each large diameter portion  373  may be located between two small diameter portions  372 . 
     In the above-described embodiment, the small diameter portion  372  and the large diameter portion  373  are arranged to be contactable with the first and second bearing portions  376 ,  377 , respectively. However, the portions  372 ,  373  may be arranged such that the small diameter portion  372  is contactable with the second bearing portion  377  while the large diameter portion  373  is contactable with the first bearing portion  376 . Further, in the above-described embodiment, the first bearing portions  376  are located on the upper side of the shaft portion  371  while the second bearing portions  377  are located on the lower side of the shaft portion  371 . However, the first bearing portions  376  are located on the lower side of the shaft portion  371  while the second bearing portions  377  are located on the upper side of the shaft portion  371 . 
     In the above-described embodiment, the small diameter portion  372  has the arcuate cross section only in its upper portion that is contactable with the first bearing portion  376  (see  FIG. 15 ), while the large diameter portion  373  has the arcuate cross section only in its lower portion that is contactable with the second bearing portion  377  (see  FIG. 18 ). However, each of the small diameter portion  372  and the large diameter portion  373  may be completely circular in cross section. 
     In the above-described embodiment, the shaft portion  371  is provided in the support member  361  of the second tray  360  while the first and second bearing portions  376 ,  377  are provided in the main body  380  of the second tray  360 . However, this arrangement may be modified such that the shaft portion  371  is provided in the main body  380  while the first and second bearing portions  376 ,  377  are provided in the support member  361 . 
     In the above-described embodiment, the image forming unit  700  is of inkjet type. However, the invention is equally applicable to a case where the image forming unit  700  is of electrophotographic type.