Abstract:
An opening and closing assembly includes a first casing, a second casing pivotally coupled to the first casing, and a support stand configured to support the second casing. The support stand includes a proximal end portion pivotally connected to one of the first and second casings, and a distal end portion slidably connected to the other thereof. The other of the first and second casings includes a guide portion for guiding the distal end portion, and first and second wall portions. The distal end portion includes a gripped portion gripped between the first and second wall portions, the gripped portion has a cross section having a width which increases, from one end of the cross section, to a maximum width and decreases from the maximum width until the other end of the cross section. The maximum width causes the first and second wall portions to be spaced apart.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and the benefit of Japanese Patent Application No. 2008-210052, filed Aug. 18, 2008, the entire disclosure of which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to an opening and closing assembly including a first casing a second casing pivotally coupled to the first casing, and a support stand configured to maintain the second casing in an open position, and relates to an image forming apparatus having the opening and closing assembly. 
         [0004]    2. Description of Related Art 
         [0005]    As an example of an image forming apparatus, a multifunction device is provided with an image recording unit for recording image on a recording sheet and an image reading unit for reading an image on an original. As an example of the image reading unit, a flatbed type is known. 
         [0006]    Generally, the flatbed-type image reading unit is pivotally disposed on top of the image recording unit in the multifunction device. As a mechanism to maintain the image reading unit in an open position with respect to the image recording unit, the multifunction device includes a support stand having a friction member at an end of the support stand. The image reading unit can be prevented from being rapidly pivoted toward the image recording unit. 
       SUMMARY OF THE INVENTION 
       [0007]    Aspects of the invention provide an opening and closing assembly and an image forming apparatus including the opening and closing assembly. 
         [0008]    In an aspect of the invention, an opening and closing assembly may comprise a first casing having a connected portion and a distant portion that is distant from the connected portion; a second casing having a connected portion and a distant portion that is distant from the connected portion of the second casing, the second casing being connected at the connected portion thereof to the connected portion of the first casing, and being pivotable about the connected portions of the respective first and second casings relative to the first casing so as to be selectively placed in open and closed positions relative to the first casing; and a support stand configured to support the second casing so as to maintain the open position of the second casing when the second casing is to be held in the open position, the support stand including a proximal end portion that is pivotably connected to the distant portion of one of the first and second casings and a distal end portion that is slidably connected to the other of the first and second casings. The other of the first and second casings may include a guide portion configured to guide the distal end portion of the support stand, for permitting the distal end portion of the support stand to be slidable between the connected portion and the distant portion of the other of the first and second casings, and first and second wall portions opposed to each other and cooperating with each other for gripping the distal end portion of the support stand that is interposed between the first and second wall portions. The distal end portion of the support stand may include a gripped portion at which the distal end portion is gripped between the first and second wall portions of the other of the first and second casings, and the gripped portion may be brought into slidable contact with the first and second wall portions of the other of the first and second casings. The gripped portion may have a cross section having a width and a length. The width of the cross section increases from one end of the cross section to a maximum width and decreases from the maximum width until the other end of the cross section. The maximum width of the cross section of the gripped portion may cause the first and second wall portions of the other of the first and second casings to be spaced apart. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    For a more complete understanding of the present invention, and the needs satisfied thereby, reference now is made to the following descriptions taken in connection with the accompanying drawings. 
           [0010]      FIG. 1  is a perspective view of a multifunction device according to an embodiment of the invention. 
           [0011]      FIG. 2  is a perspective view of the multifunction device when a scanner unit is in a first position. 
           [0012]      FIG. 3A  is a left side view of a guide member. 
           [0013]      FIG. 3B  is a bottom view of the guide member. 
           [0014]      FIG. 4A  is a cross sectional view of the guide member along the line IVA-IVA of  FIG. 3B . 
           [0015]      FIG. 4B  is a cross sectional view of the guide member along the line IVB-IVB of  FIG. 3B . 
           [0016]      FIG. 5  is a left side view of a support stand. 
           [0017]      FIG. 6  is a cross sectional view of a neck portion of the support stand along the line VI-VI of  FIG. 5 . 
           [0018]      FIG. 7  is a left side view of the support stand and the guide member when the scanner unit is in a second position. 
           [0019]      FIG. 8  is a left side view of the support stand and the guide member when the scanner unit is in between the first position and the second position. 
           [0020]      FIG. 9  is a left side view of the support stand and the guide member when the scanner unit is in the first position. 
           [0021]      FIG. 10  is a cross sectional view of the neck portion of the support stand along the line X-X of  FIG. 8 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0022]    Embodiments of the present invention and their features and technical advantages may be understood by referring to accompanying drawings, like numerals being used for like corresponding portions in the various drawings. 
         [0023]    A multifunction device  10  shown in  FIG. 1  is an example of a rotation apparatus according to an embodiment of the invention. As shown in  FIG. 1 , multifunction device  10  may include a first casing, e.g. a casing for a printer unit  11 , and a second casing, e.g. a casing for a scanner unit  12 . Multifunction device  10  may combine functions of a printer, scanner, copier and fax machine. Printer unit  11  is disposed in a lower portion of multifunction device  10 , and scanner unit  12  is disposed in an upper portion of multifunction device  10 . 
         [0024]    Printer unit  11  is configured to record images and text on a recording medium, e.g. a recording sheet, based on image data scanned by scanner unit  12  and recorded data externally input. As the invention does not directly relate to an internal structure of printer unit  11 , a detailed description thereof is omitted. However, printer unit  11  may be comprised of a structure used for a known inkjet printer. 
         [0025]    Scanner unit  12  is configured to optically read image and text of a document and convert them into electronic data. As the invention does not directly relate to an internal structure of scanner unit  12 , a detailed description thereof is omitted. However, scanner unit  12  may be comprised of a structure for a known flatbed scanner. 
         [0026]    A structure in which scanner unit  12  is rotated with respect to printer unit  11  will be described. Scanner unit  12  is coupled to printer  11  via a hinge portion, which is disposed at a rear side of multifunction device  10  (on the left side of  FIG. 2 ). Although the hinge portion is not shown in any drawings, it may include a known structure. Scanner unit  12  is rotatable upward as shown by an arrow  110  of  FIG. 2  from printer unit  11 , taking a front side of scanner unit  12  as a rotating end. As shown in  FIG. 2 , a position of scanner unit  12  that is rotated upward for access to a top surface of printer unit  11  is referred to as a first position. As shown in  FIG. 1 , a position of scanner unit  12  that closes the top surface of printer unit  11  is referred to as a second position. 
         [0027]    As shown in  FIG. 2 , a support stand  13  is disposed between printer unit  11  and scanner unit  12 . Support stand  13  is shaped in a rectangle having a length, which is slightly shorter than a depth of the multifunction device  10 . Support stand  13  has a first end portion  21  ( FIG. 5 ) and a second end portion  22 . First end portion  21  is rotatably connected to a front side of printer unit  11  (on the right side of  FIG. 2 ), and second end portion  22  is inserted into a guide member  14  ( FIG. 3 ) provided at scanner unit  12 . Stand  13  is configured to support scanner unit  12  in the first position from diagonally below, like a strut. A detailed structure of stand  13  will be described later. 
         [0028]    As indicated by a dotted line of  FIG. 2 , guide member  14  is accommodated in a bottom surface of the scanner unit  12  and to a left surface thereof. Although not shown in detail in  FIG. 2 , guide member  14  is fitted into a recessed portion formed in the bottom surface of the scanner unit  12  and assembled as a part of scanner unit  12 . A length of guide member  114 , which is shown in  FIG. 3  as a longitudinal direction  111 , aligns with a depth dimension of scanner unit  12 . 
         [0029]    Guide member  14  is open on a bottom side thereof, and thus is shaped in an inverse “U” in cross section taken along a height direction  112  of the multifunction device  10 . Guide member  14  is mounted onto scanner unit  12  so as to open on the bottom side of scanner unit  12 . In  FIGS. 3A and 4A , guide member  14  is shown as being open downward. As shown in  FIG. 3B , guide member  14  includes two opposed sidewalls  41 ,  42  extending in longitudinal direction  111 . Sidewalls  41 ,  42  are spaced apart by a specified distance L 1  and mainly define an opening  40  therebetween. Opening  40  is formed along almost all a lower end of each of sidewalls  41 ,  42 . Opening  40  continues in longitudinal direction  111  of sidewalls  41 ,  42 . Opening  40  is an example of a guide groove of the invention, and second end portion  22  of stand  13  is inserted into opening  40 . 
         [0030]    Sidewalls  41 ,  42  are connected by connecting portions  43 ,  44  at their one end in longitudinal direction  111  and their upper end. Connecting portion  43  is disposed at an end of guide member  14  in longitudinal direction  111  corresponding to the rear side of multifunction device  10 . Connecting portion  43  is formed with an engaging protrusion  45 . Engaging protrusion  45  is formed at a central portion of connecting portion  43  in the height direction, and protrudes outward along the longitudinal direction  111 . Sidewall  41  is formed with an engaging protrusion  46  in the vicinity of an upper end of sidewall  41 . Engaging protrusion  46  is formed at an end in longitudinal direction  111  opposite the engaging protrusion  45 . Engaging protrusion  46  is an extension of an upper portion of sidewall  41  along longitudinal direction  111 , and protrudes outward in longitudinal direction  111 . 
         [0031]    Although it is not shown, guide member  14  is fitted into the recessed portion formed in the bottom surface of scanner unit  12  by engaging protrusions  45 ,  46 . The recessed portion of scanner unit  12  is provided with holes in which engaging protrusions  45 ,  46  engage. By engaging engaging protrusion  45  in one of the holes, one end of guide member  14  in longitudinal direction  111  is fixed in position in a depth dimension of the recessed portion or in height direction  112  of scanner unit  12 . By engaging engaging protrusion  46  in the other hole, the other end of guide member  14  in longitudinal direction  111  is supported so as to move vertically with respect to the depth dimension of the recessed portion. Namely, engaging protrusion  46  engages in a long hole that is long in the depth dimension of the recessed portion, and thus is capable of moving within the dimension of the long hole. As guide member  14  is assembled to scanner unit  12  in this manner, it is movable vertically at engaging protrusion  46  side, taking engaging protrusion  45  as a shaft. Guide member  14  mounted into scanner unit  12  is capable of moving vertically such that its rear side (engaging protrusion  45  side) is taken as a shaft and its front side (engaging protrusion  46  side) moves in and out from the bottom surface of scanner unit  12 . This vertical movement causes guide member  14  to move between a pressed position where guide member  14  is pressed against scanner unit  12  and non-pressed position where guide member  14  is separated away from scanner unit  12 . 
         [0032]    As shown in  FIGS. 3A and 4B , sidewall  41  of guide member  14  has a guide hole  47  formed therethrough and extended generally along longitudinal direction  111 . A pin  24  ( FIG. 5 ) provided at second end portion  22  of stand  13  is inserted into guide hole  47 . The width of guide hole  47  is set to be slightly greater than the outside diameter of pin  24  so as to allow pin  24  to freely slide along guide hole  47 . Pin  24  slides in a direction generally close to longitudinal direction  111 . 
         [0033]    An engaging hole  48  is formed continuously to an end of guide hole  47  situated to the front side of the multifunction device  10 . Engaging hole  48  extends diagonally upward from guide hole  47 . When pin  24  slides from guide hole  47  into engaging hole  48 , stand  13  is held in a position to support scanner unit  12  in the first position as shown in  FIG. 2 . 
         [0034]    An arm  49  is disposed in a boundary between guide hole  47  and engaging hole  48 . Arm  49  is elastically deformable in a direction to increase the width of guide hole  47 . Arm  49  protrudes from an upper end of guide hole  47  toward the boundary between guide hole  47  and engaging hole  48 . A protruding end of arm  49  is widened to narrow the width of guide hole  47 . Thus, to cause pin  24  of stand  13  to pass between guide hole  47  and engaging hole  48 , arm  49  is required to be elastically deformed toward the upper end of guide hole  47 . As arm  49  is elastically deformed and restored to normal state, arm  49  provides a feel of the click generated when pin  24  of stand  13  is passed between guide hole  47  and engaging hole  48 . 
         [0035]    Sidewalls  41 ,  42  have inner surfaces  51 ,  52 , respectively, which are spaced apart by distance L 1  and opposed to each other. A part of each inner surface  51 ,  52  lower than guide hole  47  slidingly contacts a friction member  16  provided at stand  13 . Each inner surface  51 ,  52  is formed to substantially the same length as guide hole  47  along longitudinal direction  111 . 
         [0036]    The inner surfaces  51 ,  52  are provided with bulging portions  53 ,  54 , respectively, on the side where engaging protrusion  45  is formed or on a side close to the rear side of multifunction device  10 . Bulging portions  53 ,  54  stick out toward respective opposed inner surfaces  51 ,  52 , each forming a mountain shape. Slopes of the mountain shape that forms each bulging portion  53 ,  54  are provided such that a slope extending from the top of the mountain shape toward engaging protrusion  45  is steeper than a slope extending from the top toward engaging protrusion  46 . Distance L 1  between inner surfaces  51 ,  52  is narrowed at bulging portions  53 ,  54 . Distance L 1  becomes a distance L 2  at between tops of bulging portions  53 ,  54 , which is the narrowest distance between the inner surfaces  51 ,  52  (L 1 &gt;L 2 ). 
         [0037]    When scanner unit  12  is in the second position shown in  FIG. 1 , stand  13  is positioned as shown in  FIG. 5 . Stand  13  is generally a flat plate-like member wide in height direction  112  and long in longitudinal direction  111 . First end portion  21  of stand  13  is formed with a hole  23  recessed in the thickness of stand  13  on one side thereof. Hole  23  receives a pin (not shown) provided in printer unit  11 , so that first end portion  21  of stand  13  is rotatably coupled to printer unit  11 . 
         [0038]    Second end portion  22  of stand  13  is slightly bent with respect to longitudinal direction  111  and protrudes diagonally upward as shown by double-headed arrow  113 . Second end portion  22  is inserted into opening  40  of guide member  14 . Arrow  113  indicates a direction of insertion. Second end portion  22  is formed with pin  24  protruding in the thickness of stand  13  (in a direction perpendicular to the sheet of  FIG. 5 ). As described above, pin  24  is inserted into guide hole  47  of guide member  14  and movable along guide hole  47 . 
         [0039]    Second end portion  22  includes a gripped portion in the form of neck portion  25  ( FIG. 6 ) that is located in the vicinity of pin  24 . Neck portion  25  is disposed between pin  24  and a main body of stand  13 . As shown in  FIG. 6 , neck portion  25  is generally oval in cross section taken along a line VI-VI of  FIG. 5  which is perpendicular to insertion direction  113 . The oval shape of neck portion  25  is long in the insertion direction  113  and short in a direction perpendicular to insertion direction  113 . 
         [0040]    Neck portion  25  includes friction member  16 , which contacts inner surfaces  51 ,  52 . Friction member  16  is an elastically deformable member made of rubber. Friction member  16  is a cylindrical tube having a perimeter sufficient to cover the peripheral surface of a body of neck portion  25 . Neck portion  25  has spaces  30  covered by friction member  16 . Spaces  30  may absorb the deformation of the friction member  16 . Neck portion  25  is inserted into opening  40  of guide member  14  to slide on inner surfaces  51 ,  52  of sidewalls  41 ,  42  and produce desired sliding friction. 
         [0041]    As shown in  FIG. 6 , in the oval shaped cross section, neck portion  25  has a maximum width W passing through a center C of neck portion  25  and points A and B, and a maximum length L passing through center C of neck portion  25  and points D and E. Points A, B, D, and E are located on perimeter of neck portion  25 . Maximum width W of neck portion  25  is wider than distance L 1  between inner surfaces  51 ,  52  of guide member  14  and distance L 2  between bulging portions  53 ,  54  (W&gt;L 1 &gt;L 2 ). The perimeter of neck portion  25  is divided equally at line passing through points A, C, and B or line passing through points D, C, and E. 
         [0042]    Thus, while pin  24  of stand  13  moves along guide hole  47  of guide member  14 , neck portion  25  contacts inner surfaces  51 ,  52  and produces sliding friction. In addition, when neck portion  25  passes between bulging portions  53 ,  54  of guide member  14 , friction member  16  is elastically deformed such that its thickness is reduced. Due to this elastic deformation, a contact pressure between neck portion  25  and bulging portions  53 ,  54  is increased, and sliding friction therebetween is increased as neck portion  25  slides toward the tops of bulging portions  53 ,  54 . 
         [0043]    The following describes operations of stand  13  and guide member  14  along with rotation of scanner unit  12 . 
         [0044]    As scanner unit  12  is rotated upward with respect to printer unit  11 , stand  13  is rotated upward on hole  23  in first end portion  21  as an axis of rotation. Pin  24  in second end portion  22  of stand  13  is slidingly moved in and along guide hole  47  of guide member  14 . Guide member  14 , which is accommodated in the recessed portion formed in the bottom surface of scanner unit  12 , is rotated on the hinge portion provided at the rear side of multifunction device  10  as an axis of rotation along with the rotation of scanner unit  12 . 
         [0045]    As described above, guide member  14  is moved vertically at engaging protrusion  46  side, taking engaging protrusion  45  as a shaft, so that guide member  14  is moved between the pressed position and the non-pressed position. When scanner unit  12  is rotated toward the first position shown in  FIG. 2 , if external force does not act on guide member  14 , engaging protrusion  46  side of guide member  14  is lowered due to gravity, and protrudes from the bottom surface of scanner unit  12 . The part of guide member  14 , which protrudes from the bottom surface of scanner unit  12 , includes lower edges of inner surfaces  51 ,  52  of guide member  14 , on which neck portion  25  of stand  13  is slid. 
         [0046]    For example, when scanner unit  12  is rotated from the first position shown in  FIG. 2  to the second position shown in  FIG. 1 , upward external force acts on guide member  14  via pin  24  of stand  13 . The upward external force causes guide member  14  partially protruding from the bottom surface of scanner unit  12  to be retracted in the recessed portion against gravity. Thus, inner surfaces  51 ,  52  of guide member  14  are also accommodated into the recessed portion of scanner unit  12 . 
         [0047]    When scanner unit  12  is positioned in the second position as shown in  FIG. 1 , pin  24  of stand  13  is positioned at the rear end of guide hole  47  of guide member  14  as shown in  FIG. 7 . Stand  13  and guide member  14  are positioned horizontally along their length. 
         [0048]    When scanner unit  12  is rotated from the second position to the first position, guide member  14  is rotated upward along with scanner unit  12  as shown in  FIG. 8 . As engaging protrusion  46  side of guide member  14  is rotated upward on the hinge portion as the axis of rotation, pin  24  engaged in guide hole  47  is lifted. Thus, stand  13  is rotated upward on hole  23  of first end portion  21  as the axis of rotation to stand up, which causes pin  24  to slide in guide hole  47  from the rear side to the front side (to engaging hole  48 ). Along with the sliding of pin  24 , neck portion  25  slides on inner surfaces  51 ,  52  and bulging portions  53 ,  54 . 
         [0049]    As a reaction force of guide member  14  that lifts pin  24  engaged in guide hole  47 , downward load is applied to guide member  14 . Due to the downward load, engaging protrusion  46  side of guide member  14  lowers so as to protrude from the bottom surface of scanner unit  12 . Namely, guide member  14  is brought in the non-pressed position. 
         [0050]    As described above, when neck portion  25  slides on inner surfaces  51 ,  52  with guide member  14  placed in the non-pressed position, friction member  16  is elastically deformed such that distance L 1  between sidewalls  41 ,  42  is increased or sidewalls  41 ,  42  are separated further away from each other. Thus, sliding friction between friction member  16 , inner surfaces  51 ,  52  or bulging portions  53 ,  54  becomes reduced in comparison with guide member  14  placed in the pressed position, and load applied during rotation of scanner unit  12  from the second position to the first position becomes small. 
         [0051]    When scanner unit  12  is brought into the first position, pin  24  of stand  13  enters engaging hole  48  of guide member  14  from guide hole  47  as shown in  FIG. 9 . When pin  24  moves from guide hole  47  to engaging hole  48 , it elastically deforms arm  49 . When pin  24  completely enters engaging hole  48 , arm  49  elastically restores to normal state. A user who holds and rotates scanner unit  12  may feel a click when pin  24  enters engaging hole  48  after arm  49  is elastically deformed and then returns to its normal state. After pin  24  enters engaging hole  48 , scanner unit  12  is rotated slightly downward, and pin  24  reaches an end of engaging hole  48  at engaging protrusion  46  side. While pin  24  is engaged in engaging hole  48 , pin  24  does not return to guide hole  47  unless scanner unit  12  is lifted again. Thus, stand  13  is kept in a lifted state as shown in  FIG. 9 . The lifted stand  13  supports scanner unit  12  in the first position like a strut. 
         [0052]    To rotate scanner unit  12  from the first position to the second position, scanner unit  12  is temporarily lifted in order to return pin  24  in engaging hole  48  to guide hole  47 . The temporary lifting of scanner unit  12  causes pin  24  to move in the vicinity of the border between engaging hole  48  and guide hole  47 . Then, scanner unit  12  is lowered, thereby pin  24  elastically deforms arm  49  and enters guide hole  47 . When pin  24  enters guide hole  47 , arm  49  elastically restores to its normal state. The user who holds and rotates scanner unit  12  may feel a click when pin  24  enters guide hole  47  after arm  49  is elastically deformed and then returns to its normal state. 
         [0053]    Pin  24  of stand  13  is engaged in guide hole  47  of guide member  14 . When scanner unit  12  is rotated into the second position, guide hole  47  presses pin  24  downward, and stand  13  is rotated on hole  23  in first end portion  21  as the axis of rotation so as to fall down. Accordingly, pin  24  is slid in guide hole  47  from the front side of multifunction device  10  to the rear side thereof. 
         [0054]    As a reaction force of guide member  14  that presses pin  24  engaged in guide hole  47  downward, upward load is applied to guide member  14 . Engaging protrusion  46  side of guide member  14  is lifted, and accommodated in the recessed portion of scanner unit  12 . Namely, guide member  14  is brought in the pressed position. 
         [0055]    Due to guide member  14  placed in the pressed position, sidewalls  41 ,  42  keep distance L 1  when neck portion  25  slides on inner surfaces  51 ,  52  of guide member  14 . In other words, sidewalls  41 ,  42  positioned in the recessed position of scanner unit  12  are not elastically deformed. Thus, sliding friction between neck portion  25  and inner surfaces  51 ,  52  or bulging portions  53 ,  54  becomes increased in comparison with guide member  14  placed in the non-pressed position, and the load applied during rotation of scanner unit  12  from the first position to the second position becomes increased. 
         [0056]    As shown in  FIG. 8 , when neck portion  25  passes between bulging portions  53 ,  54 , it passes through distance L 2  narrower than distance L 1  between inner surfaces  51 ,  52 , so that pressure applied to neck portion  25  is increased and the sliding friction is increased. Thus, scanner unit  12 , which is located in a state shown in  FIG. 8 , is suddenly resistant to rotation to the second position. When neck portion  25  passes the tops of bulging portions  53 ,  54 , the distance between bulging portions  53 ,  54  is widened from distance L 2  to distance L 1 , and the sliding friction applied to neck portion  25  is reduced. Then, scanner unit  12  is located in the second position. 
         [0057]    For example, when neck portion  25  passes between bulging portions  53 ,  54  as shown in  FIG. 8 , a great sliding friction is applied to neck portion  25 . As shown in  FIG. 10 , neck portion  25  is pressed in contact with bulging portions  53 ,  54 , respectively, at portions  61 ,  62 , which are located on both ends of the maximum width of neck portion  25 . When stand  13  is moved in a sliding direction  115 , neck portion  25  slides on bulging portions  53 ,  54 . During this sliding, sliding friction F is produced between friction member  16  and bulging portions  53 ,  54  in directions of arrows  116 ,  117 . 
         [0058]    When sliding friction F exceeds a frictional force produced between the body of neck portion  25  and friction member  16 , friction member  16  may be shifted in a manner to turn around the body of neck portion  25 . In this embodiment, sliding friction F is equal at each portion  61 ,  62 , and thus friction member  16  is shifted in such a manner as to thin the thickness of friction member  16  partially, without turning around the body of neck portion  25 . Specifically, in a front portion of friction member  16  from portions  61 ,  62  in sliding direction  115 , a tensile force is produced in directions of arrows  118 ,  119  from a portion  63 , which is located at a front end with respect to the maximum length of neck portion  25  in sliding direction  115 . Due to the tensile force, friction member  16  is shifted such that the thickness of friction member  16  is slightly thinned in the front portion and is slightly increased in a rear portion of friction member  16  from portions  61 ,  62  in sliding direction  115 . 
         [0059]    Even if the thickness of friction member  16  is increased in the rear portion from portions  61 ,  62  in sliding direction  115 , friction member  16  does not slide on bulging portions  53 ,  54  by sliding friction greater than that applied to portions  61 ,  62 , due to the increase in the thickness. Friction member  16  contacts bulging portions  53 ,  54 , at portions  61 ,  62 , which are located on both ends of the maximum width of neck portion  25 . The peripheral surface of friction member  16  is curved in directions away from bulging portions  53 ,  54  in front of and behind portions  61 ,  62  in sliding direction  115 . Thus, the thickness of friction member  16  is increased at portions  61 ,  62  not only toward bulging portions  53 ,  54  but also toward the body of neck portion  25 . 
         [0060]    As described above, due to the oval shape of neck portion  25 , the tensile force is produced from portion  63  to portions  61 ,  62 , and reduction in the thickness of friction member  16  in the front portion from portions  61 ,  62  in sliding direction  115  becomes relatively small. Thus, increase in the thickness of friction member  16  in the rear portion from portions  61 ,  62  in sliding direction  115  also becomes relatively small. In the rear portion, the thickness of friction member  16  is increased toward not only bulging portions  53 ,  54  but also the body of neck portion  25 . If the thickness of friction member  16  is increased due to sliding friction F, sliding friction F is not extremely increased at a portion of friction member  16  whose thickness has been increased. 
         [0061]    According to the embodiment, neck portion  25  of stand  13  is generally oval in cross section perpendicular to the direction  113  along which second end portion  22  is inserted into opening  40  of guide member  14 . When friction member  16  slides on bulging portions  53 ,  54  of guide member  14 , sliding friction F is increased and friction member  16  is shifted with respect to the body of neck portion  25 . As the shifting is caused by the tensile force produced from portion  63  to portions  61 ,  62  that contact bulging portions  53 ,  54 , a change in thickness of friction member  16  becomes relatively small and the thickness of friction member  16  is not extremely increased around portions  61 ,  62 . 
         [0062]    Friction member  16  contacts bulging portions  53 ,  54  at portions  61 ,  62 . If the thickness of friction member  16  is increased at a part of the rear portion from portions  61 ,  62  contacting bulging portions  53 ,  54  in sliding direction  115 , sliding friction F is not extremely increased at the part of the rear portion where the thickness is increased. Thus, friction member  16  of stand  13  can be prevented from being worn out on one side. 
         [0063]    According to the embodiment, neck portion  25  may be generally oval in cross section. Neck portion  25  may be also circle in cross section. Neck portion  25  may be shaped such that its cross section has a maximum width and a maximum length equal to or greater than the maximum width. Portions  61 ,  62  may define the maximum width of neck portion  25 . 
         [0064]    In the embodiment, neck portion  25  is interposed between opposing sidewalls  41 ,  42  of guide member  14  to slide on inner surfaces  51 ,  52 . Guide member  14  may not have sidewalls  41 ,  42 . Instead, guide member  14  may make up one wall and casing of scanner unit  12  may make up the other wall. 
         [0065]    In the embodiment, distance L 1  between opposing sidewalls  41 ,  42  of guide member  14  is narrowed to distance L 2  at bulging portions  53 ,  54 . However, bulging portions  53 ,  54  may be omitted. 
         [0066]    In the embodiment, the first casing is for printer unit  11  and the second casing is for scanner unit  12 . Printer unit  11  may be disposed in the second casing and scanner unit  12  may be disposed in the first casing. The first casing and the second casing may be used for other functional units of the image forming apparatus.