Patent Publication Number: US-11656567-B2

Title: Image forming apparatus and operation unit for operating the same

Description:
BACKGROUND 
     Field 
     The present disclosure relates to an image forming apparatus and an operation unit for operating the image forming apparatus. 
     Description of the Related Art 
     Image forming apparatuses such as copying machines are provided with an operation unit operated by the user to switch between operations and make detailed settings in each operation. In a system (image forming system) where optional apparatuses such as a paper feed unit, a conveyance unit, and a post-processing unit are connected with an image forming apparatus, the user performs setting operations for various optional apparatuses by using the operation unit. 
     In a large-sized image forming system having a long length connected with a plurality of optional apparatuses as described above, the user may perform operations for the optional apparatuses on a location apart from the image forming apparatus provided with the operation unit. It is troublesome for the user to move between these optional apparatuses each time the user operates the optional apparatuses and the operation unit. 
     There is proposed an image forming system, for example, where an operation unit can be installed not only on an image forming apparatus but also on optional apparatuses (Japanese Patent Application Laid-Open No. 2010-243977). The operation unit discussed in Japanese Patent Application Laid-Open No. 2010-243977 includes a display that displays information to the user, an arm that supports the display, and a supporting base that supports the display via the arm. The display supported by the arm extending from the supporting base forms a predetermined angle with respect to a placement surface where the supporting base is placed. 
     For example, when the display panel of the operation unit displays small images and texts, some users may feel it hard to view. In this case, such a user adjusts the posture by bending down or comes close to the display panel. In this way, the posture and the distance to the display panel with which the display of the display panel is easily viewable are different from user to user. 
     For this reason, a form where the user can operate the operation unit placed on the palm will be considered below. Generally, when the user operates the operation unit placed on the palm, the fingertips are upwardly oriented so that the palm is oriented toward the user&#39;s face. In this state, each user is able to operate the operation unit with the posture most suitable for the user by adjusting the angles of the arm and wrist. 
     In a possible situation, the user operating the operation unit placed on the palm may show the display of the operation unit to another user next to the user. As a specific example of a specific situation, the user has a preview screen for a print product or a print condition setting screen to be checked by another user before printing. When the user shows the display to the user next to him/her, the user twists the wrist with the fingertips upwardly oriented so that the palm is oriented toward the face of the user next to him/her. As a result, the display of the operation unit placed on the palm is oriented toward the next user&#39;s face. 
     However, when the user shows the display of the operation unit to the user next to him/her in this way, the operation unit may possibly slip down from the palm. If the operation unit slips down from the palm and then hits the floor, the operation unit may possibly be damaged by the impact. 
     SUMMARY 
     According to an aspect of the present disclosure, an image forming apparatus having a placement surface as a top surface of the image forming apparatus includes an image forming unit configured to form an image on paper, and an operation unit configured to be operated by a user to transmit an execution signal for instructing the image forming unit to perform image formation, wherein the operation unit is configured to allow an operation while the operation unit is in a state of being held up by the user and in a state of being placed on the placement surface of the image forming apparatus at an arbitrary position within a predetermined range, and a controller configured to receive the execution signal and control the image forming unit, wherein the operation unit includes: a touch panel display configured to receive a touch operation by the user, and to display an execution icon to be touched by the user to enable the operation unit to transmit the execution signal to the image forming apparatus, a cable having one of both ends of the cable connected to the operation unit and configured to transmit the execution signal to the controller, an exterior cover configured to form an exterior, and an insertion member disposed on a side opposite to a side where the touch panel display is disposed on an outside of the exterior cover and configured to pass fingertips of the user through when the user operates the operation unit while holding up the operation unit, and wherein the predetermined range is a range where the operation unit is movable in a state of being connected to the cable. 
     Further features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic cross-sectional view illustrating an image forming system. 
         FIG.  2    is a schematic cross-sectional view illustrating a part of the image forming system. 
         FIG.  3    illustrates a control configuration of the operation unit of the image forming system. 
         FIG.  4    illustrates an operation unit placed on the top surface of a housing, to the left of a reading apparatus. 
         FIG.  5    illustrates the operation unit placed on the top surface of the housing, to the right of the reading apparatus. 
         FIGS.  6 A,  6 B, and  6 C  illustrate the operation unit. 
         FIGS.  7 A and  7 B  are schematic perspective views illustrating the operation unit. 
         FIGS.  8 A and  8 B  illustrate a mechanism of adjusting the inclination angle of the display panel with respect to the top surface. 
         FIGS.  9 A,  9 B, and  9 C  illustrate an effect of attaching a band to the operation unit. 
         FIGS.  10 A,  10 B, and  10 C  illustrate the band attached to the operation unit. 
         FIGS.  11 A and  11 B  are enlarged views illustrating attachment portions of the band to the operation unit. 
         FIG.  12    illustrates a space formed by the band. 
         FIGS.  13 A and  13 B  illustrate the positional relation between the band and a cable. 
         FIGS.  14 A and  14 B  illustrate a configuration of the band attachment to the operation unit (modification). 
         FIGS.  15 A and  15 B  illustrate a configuration of the band attachment to a portion other than an arm (second exemplary embodiment). 
         FIGS.  16 A and  16 B  illustrate an arm having the function of a band (third exemplary embodiment). 
         FIG.  17    illustrates a system configuration of an image forming apparatus capable of wirelessly communicating with the operation unit (fourth exemplary embodiment). 
         FIG.  18    illustrates a system configuration of an operation unit capable of wirelessly communicating with the image forming apparatus (fourth exemplary embodiment). 
         FIG.  19    illustrates a communication state transition in wireless communication. 
         FIG.  20    illustrates a configuration of wireless communication. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Exemplary embodiments of the present disclosure will be described below with reference to the accompanying drawings. Sizes, materials, shapes, and relative arrangements of elements described in the exemplary embodiments are not limited thereto. Unless otherwise specifically described, the scope of the present disclosure is not limited to the exemplary embodiments described below. Descriptions of the present exemplary embodiment will be made based on the directions defined as illustrated in  FIG.  1   . The front side, the rear side (back side), the left-hand side, the right-hand side, the upper side, and the lower side of an image forming apparatus  2  are defined as a front direction F, a rear direction B, a left direction L, a right direction R, an upward direction U, and a downward direction D, respectively. 
     Configuration of Image Forming System 
     As illustrated in  FIG.  1   , an image forming system  1  according to the present exemplary embodiment includes, for example, the image forming apparatus  2 , which is a printer, and a post-processing apparatus  103  adjacently disposed in the left direction L of the image forming apparatus  2  and configured to stack sheets S ( FIG.  2   ). According to the present exemplary embodiment, the image forming apparatus  2  and the post-processing apparatus  103  are defined as housings. A top surface  109  that can be used as a workspace is provided on the top face of the image forming apparatus  2 . According to the exemplary embodiment, the area of the top surface  109  is larger than the maximum area of the sheet S on which the image forming apparatus  2  can form an image. The user spreads a drawing on the top surface  109  and performs work such as drafting. Therefore, the top surface  109  is configured to become horizontal on the assumption that the floor where the image forming system  1  is installed is horizontal. 
     In addition, the top surface  109  is configured to be flat as much as possible. A region  1010  illustrated in  FIG.  4    (described below) is an example of a workspace. If the image forming system  1  is horizontally installed, the workspace  1010  also becomes horizontal. This region is flat since it is a part of the top surface  109 . “A flat surface” refers to a surface other than connecting portions between members unavoidably formed in designing the exterior of the image forming system  1 . This surface is designed to reduce grooves and other unevenness as much as possible. The workspace  1010  may be in a size that allows at least A3-size paper to be spread, in which a flat surface needs is secured. The top surface  109  is made of resin, for example, and is assumed to be a “flat surface” even if there is a certain wobble or waviness that unavoidably arises in production. The concept “horizontal” in this case includes not only “horizontal” in the strictly mathematical sense but also “approximately horizontal” that can be practically regarded as horizontal. 
     The present exemplary embodiment will be described below centering on a tandem full-color printer as an example of the image forming apparatus  2 . However, the present disclosure is not limited to the tandem image forming apparatus  2  but may be image forming apparatuses of other types, for example, monochrome and monocolor image forming apparatuses. 
     As illustrated in  FIG.  2   , according to the exemplary embodiment, the image forming apparatus  2  as an example of the housing can be divided into two different portions: an image forming unit housing  2   a  and a conveyance unit housing  2   b . The conveyance unit housing  2   b  conveys paper with an image formed thereon in the image forming unit housing  2   a  to the post-processing apparatus  103  (not illustrated). Each of the image forming unit housing  2   a  and the conveyance unit housing  2   b  is also an example of a housing. The image forming unit housing  2   a  has a top surface  109   a , and the conveyance unit housing  2   b  has a top surface  109   b . The image forming unit housing  2   a  and the conveyance unit housing  2   b  can be connected with each other. The top surfaces  109   a  and  109   b  can be connected to configure the flat top surface  109 . The image forming unit housing  2   a  and the conveyance unit housing  2   b  can be connected and separated in this way. Therefore, for example, when conveying these housings to upper floors of a building, the housings can be separately loaded on an elevator and then conveyed to a destination floor. This enables easily conveying the image forming system  1  having a large full length and a large size to a destination floor in a building by using an elevator. 
     The image forming system  1  includes a toner supply unit  20 , a sheet feeding unit  30 , an image forming unit  40 , a sheet conveyance unit  50 , a sheet discharge unit  60 , an electrical device unit  70 , and an operation unit  80 . A toner image is formed on the sheet S, which is a recording material. Specific examples of the sheet S include plain paper, a synthetic resin sheet as a substitute of plain paper, thick paper, and an overhead projector (OHP) sheet. 
     The sheet feeding unit  30  disposed at the bottom of the image forming apparatus  2  includes sheet cassettes  31  for storing sheets S in a stacked way, and feed rollers  32 . The sheet feeding unit  30  is configured to feed the sheet S to the image forming unit  40 . 
     The image forming unit  40  includes image forming units  41 , toner bottles  42 , exposure apparatuses  43 , an intermediate transfer unit  44 , a secondary transfer portion  45 , and a fixing apparatus  46 . 
     The image forming unit  41  includes four image forming units  41   y ,  41   m ,  41   c , and  41   k  for toner colors yellow (y), magenta (m), cyan (c), and black (k), respectively, for forming a 4-color toner image. Each of these image forming units  41  can be attached to and detached from the image forming apparatus  2 . For example, the image forming unit  41   y  includes a photosensitive drum  47   y  for forming a toner image, a charging roller  48   y , a developing sleeve  49   y , a drum cleaning blade (not illustrated), and toner. The image forming unit  41   y  is supplied with toner from a toner bottle  42   y  filled with toner, and toner bottle  42   m , toner bottle  42   c , and toner bottle  42   k  supply associated image forming units  41   m ,  41   c , and  41   k . Detailed descriptions of other image forming units  41   m ,  41   c , and  41   k  having a similar configuration to that of the image forming unit  41   y , such as including developing sleeves  49   m ,  49   c , and  49   k , except for the toner color will be omitted. 
     An exposure apparatus  43   y  is an exposure unit that exposes the surface of the photosensitive drum  47   y  to light to form an electrostatic latent image on the surface of the photosensitive drum  47   y.    
     The intermediate transfer unit  44  is disposed in the downward direction D of the image forming units  41 . The intermediate transfer unit  44  includes a drive roller  44   a , a plurality of rollers such as primary transfer rollers  44   y ,  44   m ,  44   c , and  44   k , and an intermediate transfer belt  44   b  stretched on these rollers. The primary transfer rollers  44   y ,  44   m ,  44   c , and  44   k  are disposed to face the photosensitive drums  47   y ,  47   m ,  47   c , and  47   k , respectively, so as to be in contact with the intermediate transfer belt  44   b . When the intermediate transfer belt  44   b  is applied with a positive-polarity transfer bias by the primary transfer rollers  44   y ,  44   m ,  44   c , and  44   k , negative-polarity toner images on the photosensitive drums  47   y ,  47   m ,  47   c , and  47   k  are sequentially transferred to the intermediate transfer belt  44   b  in an overlapped way. Thus, a full-color image is formed on the intermediate transfer belt  44   b.    
     The secondary transfer portion  45  is formed of a secondary inner transfer roller  45   a  and a secondary outer transfer roller  45   b . When the secondary outer transfer roller  45   b  is applied with a positive-polarity secondary transfer bias, the full-color image formed on the intermediate transfer belt  44   b  is transferred to the sheet S. 
     The secondary inner transfer roller  45   a  stretches the intermediate transfer belt  44   b  on an inner side of the intermediate transfer belt  44   b . The secondary outer transfer roller  45   b  is disposed at a position facing the secondary inner transfer roller  45   a  across the intermediate transfer belt  44   b.    
     The fixing apparatus  46  includes a fixing roller  46   a  and a pressure roller  46   b . When the sheet S is pinched and conveyed between the fixing roller  46   a  and the pressure roller  46   b , the toner image transferred on the sheet S is pressurized and heated to be fixed onto the sheet S. Although, in the present exemplary embodiment, the conveyance unit housing  2   b  includes the fixing apparatus  46 , the present disclosure is not limited thereto. For example, the image forming unit housing  2   a  may include the fixing apparatus  46  but the conveyance unit housing  2   b  may not include the fixing apparatus  46 . Of course, each of the housings may include a fixing apparatus. 
     The sheet conveyance unit  50  conveys the sheet S, fed from the sheet feeding units  30 , from the image forming unit  40  to the sheet discharge unit  60 . The sheet conveyance unit  50  includes a secondary pre-transfer conveyance path  51 , a pre-fixing conveyance path, a discharge path  53 , and a re-conveyance path  54 . 
     The sheet discharge unit  60  includes a discharge roller pair  61  disposed on the downstream side of the discharge path  53 , and a discharge port  62  disposed on the side face on the left direction L side of the image forming apparatus  2 . The discharge roller pair  61  feeds the sheet S, conveyed from the discharge path  53 , from the nip portion and discharges the sheet S from the discharge port  62 . The discharge port  62  is able to feed the sheet S to the post-processing apparatus  103  disposed on the left direction L side of the image forming apparatus  2 . 
     As illustrated in  FIG.  3   , the electrical device unit  70  includes an image controller  710 , which is a control board including a control unit, and a hard disk drive (hereinafter referred to as an HDD)  72  as a removable mass storage device. The image controller  710  includes a computer, for example, a central processing unit (CPU)  73 , a read only memory (ROM)  74  for storing programs that control each section, a random access memory (RAM)  75  for temporarily storing data, and an input/output circuit interface (I/F)  76  for outputting and inputting signals to/from the outside. The HDD  72  ( FIG.  2    and  FIG.  3   ) is a removable mass storage device for storing electronic data and can mainly accumulate image processing programs, digital image data, and supplementary information for the digital image data. At the time of image forming, the image data is read from the HDD  72 . 
     The CPU  73  is a microprocessor that controls the entire image forming apparatus  2  and is the main component of a system controller. The CPU  73  is connected with the sheet feeding unit  30 , the image forming unit  40 , the sheet conveyance unit  50 , the sheet discharge unit  60 , the HDD  72 , and the operation unit  80  via the input/output circuit  76 . The CPU  73  exchanges signals with these units and controls the operations thereof. The image controller  710  enables the user to perform operations and make settings via an instruction from a computer (not illustrated) connected to the image forming apparatus  2  and an operation on the operation unit  80 . 
     The operation unit  80  is provided separately from the image forming apparatus  2  to enable operation of each unit of the image forming apparatus  2 . The operation unit  80  includes a driver board  81  and a display panel  82  (display unit). The display panel  82  displays information necessary for the user to operate the image forming apparatus  2 , such as the remaining amount of sheets S supplied to the image forming apparatus  2 , the remaining amount of toner, warning messages displayed when these consumables run out, and procedures for replenishing the consumables. The display panel  82  also accepts user operations for setting the size and grammage of the sheet S, adjusting the image density, and setting the number of sheets to be output. 
     The operation unit  80  is connected to the electrical device unit  70  of the image forming apparatus  2  via a cable  90 . Although, in the above-described example, the cable  90  bundles a signal line  90   a  and a power line  90   b , the signal line  90   a  and the power line  90   b  may be separate cables. The signal line  90   a  connects the input/output circuit  76  of the image controller  710  and the driver board  81 . The power line  90   b  connects a power source apparatus  17  of a DCON control unit  10  ( FIG.  3   ) of the image forming apparatus  2  and the driver board  81 . More specifically, the signal line  90   a  transmits an execution signal from the driver board  81  (also referred to as a controller) of the operation unit  80  to the image controller  710  (also simply referred to as a controller) of the image forming apparatus  2 . For example, the execution signal serves as a trigger signal that triggers an image forming unit  15  ( FIG.  17   ) to perform image forming. When the user touches an icon (execution icon) displayed on the display panel  82  of the operation unit  80 , the execution signal is transmitted from the driver board  81  to the image controller  710 . 
     The image forming operation by the image forming apparatus  2  configured as described above will be described below. 
     When the image forming operation is started, the photosensitive drums  47   y ,  47   m ,  47   c , and  47   k  rotate, and the surfaces of these drums are charged by the charging rollers  48   y ,  48   m ,  48   c , and  48   k , respectively. Then, the exposure apparatuses  43   y ,  43   m ,  43   c , and  43   k  emit laser beams to the photosensitive drums  47   y ,  47   m ,  47   c , and  47   k , respectively, based on image information. Electrostatic latent images are formed on the surfaces of the photosensitive drums  47   y ,  47   m ,  47   c , and  47   k . When toner is applied to the electrostatic latent images, the electrostatic latent images are visualized as toner images and then transferred to the intermediate transfer belt  44   b.    
     Meanwhile, in parallel with this toner image forming operation, the feed roller  32  rotates to separate and feed the uppermost sheet S in the sheet cassettes  31 . Then, in synchronization with the toner image on the intermediate transfer belt  44   b , the sheet S is conveyed to the secondary transfer portion  45  via the secondary pre-transfer conveyance path  51 . Further, the image is transferred from the intermediate transfer belt  44   b  to the sheet S, the sheet S is conveyed to the fixing apparatus  46 , the unfixed toner image is heated and pressurized to be fixed to the surface of the sheet S, and the sheet S is discharged from the discharge port  62  by the discharge roller pair  61  and then supplied to the post-processing apparatus  103 . 
     Configuration of Operation Unit 
     Overview of the electrical device unit  70 , the operation unit  80 , the cable  90 , a cover  101 , and an opening  102  will be described below. 
     The electrical device unit  70  is provided on the rear face of the image forming apparatus  2 . A connector (not illustrated) provided on one end of the cable  90  is connected to the electrical device unit  70 . The cable  90  transmits a control signal for controlling the operation unit  80  from the electrical device unit  70  to the operation unit  80 . The cable  90  has a function of communicably connecting the image forming apparatus  2  and the operation unit  80 . 
     The other end of the cable  90  is provided with a connector (not illustrated) that is connected to the operation unit  80 . The operation unit  80  is connected to the image forming apparatus  2  with a cable in this way but is not fixed to the top surface  109 . Therefore, the user is able to freely place the operation unit  80  at an arbitrary position on the top surface  109  within a range of the cable extension. A “free” state in this case refers to a state where the operation unit  80  is not fixed to the top surface  109  with screws, for example. This means that the operation unit  80  is configured so that its position can be freely changed on the top surface  109 . 
     According to the present exemplary embodiment, the image forming apparatus  2  and the operation unit  80  perform bidirectional communication via the cable  90 . Therefore, as described above, the user is able to place the operation unit  80  at an arbitrary position within in the range of the length (a predetermined range) of the cable  90 . In other words, the predetermined range refers to the movable range of the operation unit  80  in a state where the operation unit  80  and the cable  90  are connected with each other. More specifically, the predetermined range is determined by the length of the cable  90 . 
     Therefore, for example, the movable range of the operation unit  80  can be adjusted by adjusting the length of the cable  90 . 
     Other forms will be described in detail below as a fourth exemplary embodiment where a wireless communication method is adopted. In this case, the movable range of the operation unit  80  is not limited by the cable  90 . In this case, the user is able to place the operation unit  80  at an arbitrary position within the range (a predetermined range) of the top surface  109 . More specifically, the entire top surface  109  serves as the placement surface for the operation unit  80 . 
     Thus, the operation unit  80  can be moved exceeding the range of the length of the cable  90 . Even in this case, since the placement position of the operation unit  80  can be freely changed on the top surface  109 , the operation unit  80  can be freely placed on the top surface  109 . 
       FIGS.  4  and  5    illustrate the position on the top surface  109  where the operation unit  80  can be placed. For example, the operation unit  80  can be placed on a space close to a document reading apparatus  115  on the top surface  109  of the image forming apparatus  2 , as illustrated in  FIG.  4   . The operation unit  80  can also be placed on a space on a top surface  106  of a sheet feeding apparatus  105 , as illustrated in  FIG.  5   . Although not illustrated in  FIGS.  4  and  5   , the operation unit  80  can be placed on the top face of the image forming system  1 , such as a top surface  104  of the post-processing apparatus  103 . In addition, the operation unit  80  can also be placed on a space other than the top surface of the image forming system  1 , for example, on a bench (not illustrated) disposed in the vicinity of the image forming system  1 . 
       FIG.  6 A  illustrates the top face of the operation unit  80  viewed from above along the vertical direction.  FIG.  6 B  illustrates the bottom face of the operation unit  80 .  FIG.  6 C  illustrates the side face of the operation unit  80 . 
     As illustrated in  FIG.  6 A , the operation unit  80  has the display panel  82 . The display panel  82  of the operation unit  80  according to the present exemplary embodiment is a liquid crystal touch panel. More specifically, the display panel  82  can accept touch operations by the user. Touch operations refer to operations of touching the display panel  82  with the fingertips, and include a flick and a scroll operation. The cable  90  extends from the back side of the operation unit  80 . As illustrated in  FIG.  6 B , rubber bases  85  ( 85   a  and  85   b   1 ) as examples of elastic members are provided on the bottom face of the operation unit  80 . The rubber bases  85  are also examples of a first to fourth contact portions (examples of a plurality of bases) and are portions in contact with the top surface  109 . The rubber bases  85  are portions that come into contact with the top surface  109  when the operation unit  80  is placed on the top surface  109 . The rubber bases  85  are made of an elastic member the surface of which has a high friction coefficient. The rubber bases  85  are configured to be slightly bent when the operation unit  80  is placed on the top surface  109 . This makes it possible to support the operation unit  80  at four points as in the present exemplary embodiment. Mathematically, a plane is determined by three different points. All of the four points come in contact with the top surface  109  since one of the rubber bases  85  is bent. The operation unit  80  according to the present exemplary embodiment is provided with two rubber bases  85   a  on the front side of the operation unit  80 , and two rubber bases  85   b   1  on the rear side thereof. The rubber bases  85  reduce the possibility of the operation unit  80  shaking when the user presses any portion of the display panel  82 . 
     As illustrated in  FIG.  6 B , the four rubber bases  85  are disposed to surround the center of gravity G of the operation unit  80 . In other words, the center of gravity G is located in the region surrounded by the four rubber bases  85 . The four rubber bases  85  disposed in this way stably support the operation unit  80 , improving the user&#39;s operability. When the operation unit  80  is viewed from above along the vertical direction, the rubber bases  85   a  are disposed on the upstream side of the center of gravity G, and the rubber bases  85   b   1  are disposed on the downstream side thereof in the direction perpendicular to both the front/back direction of paper (the direction perpendicular to both the direction perpendicular to a display surface  820  ( FIG.  7 A ) and the vertical direction) and the direction perpendicular to a display surface  820 , i.e., in the direction of climbing the slope of the display panel  82 . 
     One of the two rubber bases  85   b   1  is disposed at the right-hand end on the bottom face of the operation unit  80 , and the other thereof is disposed at the left-hand end on the bottom surface of the operation unit  80 . It is assumed that the operation unit  80  placed on the top surface  109  is viewed from the bottom side of the operation unit  80 . Therefore, the left-hand side of paper is defined as the right-hand side of the operation unit  80 , and the right-hand side of paper is defined as the left-hand side of the operation unit  80 . If the operation unit  80  is assumed to have a width L 1  in the horizontal direction, it is desirable that one of the rubber bases  85   b   1  is disposed at the rightmost region (on one end side) and the other of the rubber bases  85   b   1  is disposed at the leftmost region (on the other end side) when the width L 1  is divided into quarters. Disposing the two rubber bases  85   b   1  at a certain distance in this way enables improving the stability of the operation unit  80  placed on the top surface  109 . 
     The horizontal direction in this case refers to the direction perpendicular to both the direction perpendicular to the display surface  820  (described below) and the vertical direction, and also is the width direction of the operation unit  80 . 
       FIG.  6 C  illustrates the operation unit  80  placed on the top surface  109  viewed from the right-hand side of the operation unit  80 . The surface on which the rubber bases  85  conform to the top surface  109  when the operation unit  80  is placed thereon is referred to as the rubber base surface, and is illustrated in  FIG.  6 C . As described above, in a case where the rubber bases  85  are made of a rigid member and the rubber bases  85  come into contact with the top surface  109  at the four positions, one of the four positions is lifted. This phenomenon is unavoidable in terms of the tolerance of parts. For this reason, all of the four rubber bases  85  conform to the top surface  109  if at least two of the four rubber bases  85  are elastic members. This enables the user to stably operate the operation unit  80  on the top surface  109 . 
     An advantage of the cable  90  extending from the back side of the operation unit  80  will be described below with reference to  FIG.  6 C . As illustrated in  FIG.  6 C , the cable  90  extends from the operation unit  80  in the direction of climbing the slope of the display panel  82  when the operation unit  80  is viewed along the vertical direction. When the operation unit  80  is viewed along the vertical direction, the “extending direction” matches the direction perpendicular to both the front/back direction of paper (the direction perpendicular to both the direction perpendicular to the display surface  820  of the display panel  82  and the vertical direction) and the direction perpendicular to the display surface  820 . 
     Since the cable  90  backwardly extends from the rear side of the operation unit  80 , the connecting portion between the cable  90  and the operation unit  80  cannot be seen from the user operating the operation unit  80 . This improves the designability of the operation unit  80 . 
       FIG.  7 A  is a perspective view illustrating the operation unit  80  and an enlarged view illustrating the display panel  82  (touch panel display). The display panel  82  displays icons (examples of execution icons) such as “Copy” and “Scan”. When an icon displayed on the display panel  82  is touched, the execution signal is transmitted from the operation unit  80  to the image forming apparatus  2 . As illustrated in  FIG.  7 A , the operation unit  80  is provided with a supporting base  86 . The supporting base  86  supports the display panel  82 . More specifically, when the operation unit  80  is placed on the top surface  109 , the supporting base  86  supports the display panel  82  so that the display panel  82  forms a predetermined angle A ( FIG.  6 C ) with respect to the top surface  109 . 
     The supporting base  86  is also provided with the rubber bases  85  ( 85   a  and  85   b   1 ). More specifically, the rubber bases  85   a  are provided at the right and the left ends on the front side of the supporting base  86 , and an arm  822  is provided on the rear side of the supporting base  86 . The rubber bases  85   b   1  are provided at the right and the left ends of the arm  822 . The angle of the display panel  82  with respect to the top surface  109  is determined when the four rubber bases  85  come into contact with the top surface  109 . 
     The display panel  82  has the display surface  820  that displays a copy start button, a screen for setting the paper size, a screen for setting the number of print copies, a screen for displaying the remaining amount of toner, and information about image forming. Although, in the present exemplary embodiment, the display surface  820  is disposed on the portion excluding the edges of the display panel  82 , information about image forming and a screen for print setting may be displayed on the entire surface of the display panel  82 . However, in either case, the inclination angle of the display surface  820  with respect to the top surface  109  means the angle formed by an area near the center (the region corresponding to the display surface  820  in  FIG.  7 A ) of the display panel  82  with respect to the top surface  109 . 
       FIGS.  8 A and  8 B  illustrate the function of the arm  822  disposed on the operation unit  80 .  FIG.  8 A  illustrates the operation unit  80  in a state where the arm  822  is retracted on the bottom side of the operation unit  80 . 
       FIG.  8 B  illustrates the operation unit  80  in a state where the arm  822  is pulled out. 
     As illustrated in  FIGS.  8 A and  8 B , the arm  822  rotatable with respect to the operation unit  80  is provided on the bottom side of the operation unit  80 . The angle A of the display panel  82  with respect to the top surface  109  can be adjusted by retracting the arm  822  on the bottom side of the operation unit  80  ( FIG.  8 A ) and pulling out the arm  822  ( FIG.  8 B ). According to the present exemplary embodiment, this angle A is 30 degrees when the arm  822  is retracted on the bottom side of the operation unit  80 , and 45 degrees when the arm  822  is pulled out. Since the angle A of the display panel  82  with respect to the top surface  109  can be adjusted in this way, the operation unit  80  is easy to use for various users with different heights of eye line, such as users on a wheelchair and tall users. 
     Effect of Providing Band (Insertion Member) on Operation Unit 
     A band will be described below as an example of an insertion member. Examples of applicable insertion members include a leather belt, a ring-shaped resin part, and a metal fixture. 
     When the operation unit  80  is configured to be freely placed on the top surface  109 , like the present exemplary embodiment, the user is able to hold up the operation unit  80  in user&#39;s hand and then place it at an arbitrary position on the top surface  109 . Some users may use the operation unit  80  not in a state of being placed on the top surface  109  but in a state of being held up in user&#39;s hand. For example, if the user feels that the texts or drawings displayed on the display panel  82  are small, the user may want to bring the eyes close to the display panel  82 . In such a case, if the user tries to bring the eyes close to the display panel  82  of the operation unit  80  placed on the top surface  109 , the user needs to bend down. Some users may feel it troublesome to take such a posture. Particularly, such users have a tendency to view and operate the display panel  82  with the operation unit  80  placed on the palm. 
     Although, in the above-described exemplary embodiment, communication between the operation unit  80  and the image forming apparatus  2  is performed via the cable  90 , a form of wireless communication is also possible. A form of wireless communication will be described in detail below as the fourth exemplary embodiment. In such a form of wireless communication, the operation unit  80  is often operated at a position away from the image forming apparatus  2 , and hence the user is assumed to use the operation unit  80  on the palm to a further extent. 
       FIGS.  9 A to  9 C  illustrate a use mode of the operation unit  80  using a band  92  (described below). In this example of a situation, the user operates the operation unit  80  at an angle of the display panel  82  of about 30 to 45 degrees with respect to the horizontal plane. More specifically, the user holds up the operation unit  80  with the palm oriented toward the face ( FIG.  9 A ). As illustrated in  FIG.  9 A , there is no possibility of the operation unit  80  dropping from the palm in a state where the operation unit  80  is placed on the palm. 
     However, if the wrist is twisted in the state in  FIG.  9 A , i.e., if the palm is turned over in the state in  FIG.  9 A , the operation unit  80  will drop from the palm. If the wrist is slightly twisted, even without the palm being completely turned over, the operation unit  80  may possibly slip down from the palm. This may happen, for example, when the user shows the display panel  82  to have information displayed on the display panel  82  checked by another user next to the user. More specifically, in a possible case, print contents are previewed in the display panel  82  before being printed on paper, and the screen is shown to another user. In another possible case, settings including the number of print copies and two-sided/one-sided printing (information about image forming) are shown to another user. How much the wrist can be twisted before the operation unit  80  slips down from the palm depends on the palm condition and the material and shape of the bottom side of the operation unit  80  in contact with the palm. In any case, the operation unit  80  slips down at least before the palm is turned over. In a case where a user shows the display panel  82  to another user next to the user, the user may pay attention to the orientation of the palm so as not to let the operation unit  80  slip down from the palm or may unconsciously twist the wrist. In such a case, the operation unit  80  can be prevented from dropping from the palm when the wrist is twisted by putting the palm (fingertips) through the band  92  (describe in detail below).  FIG.  9 B  illustrates a state where the wrist is turned over. Referring to  FIG.  9 B , since the user has turned over the palm completely, the operation unit  80  has slipped down from the palm. However, since the palm is put through the band  92 , the band  92  is caught on the palm, preventing the operation unit  80  from dropping and hitting the floor. 
       FIG.  9 C  illustrates a state where the orientation of the palm is changed so that the fingertips are downwardly oriented. Even if the palm is put through the band  92 , orienting the palm in this way may possibly allow the band  92  to fall off from the fingertips, and the operation unit  80  may slip down from the palm. 
     Accordingly, when showing the display panel  82  to the user next to him/her or a user facing him/her, the user needs to avoid showing the display panel  82  in the way illustrated in  FIG.  9 C . Although the band  92  according to the present exemplary embodiment reduces the possibility of the operation unit  80  slipping down from the palm, the operation unit  80  cannot be prevented from dropping if the fingertips are downwardly oriented. The band  92  according to the present exemplary embodiment is intended to reduce the possibility of the operation unit  80  slipping down from the palm when the wrist is turned over in a state where the fingertips are upwardly oriented. 
     Band Configuration (First Exemplary Embodiment) 
       FIGS.  10 A to  10 C  are perspective views illustrating the bottom side of the operation unit  80 . The bottom side of the operation unit  80  refers to the side opposite to the side where the display panel  82  is provided. When the rubber bases  85  of the operation unit  80  are brought into contact with the top surface  109 , the display panel  82  is upwardly oriented in the vertical direction. This state is defined as the normal operating state. The side upwardly oriented in this state, i.e., the side on which the display panel  82  is provided, is defined as the front side of the operation unit  80 . In this state, the bottom side of the operation unit  80  is oriented toward the top surface  109 . 
       FIG.  10 A  illustrates a state where the arm  822  is closed with respect to the operation unit  80 , i.e., a state where the arm  822  is retracted on the bottom side of the operation unit  80 . Further, the arm  822  is provided with a groove  93  formed to store the band  92 . Thus, the groove  93  has a space for storing the entire band  92 . In a state where the entire band  92  is stored in the groove  93 , the band  92  does not protrude from the virtual plane determined by the rubber bases  85 . The virtual plane is defined by selecting arbitrary three bases out of the rubber bases  85 . The band  92  can be folded in this way. In the folded state, the band  92  is stored in the space within the height of rubber bases  85 . 
     A state where the band  92  does not protrude from the virtual plane is defined as a state where the band  92  is stored in the groove  93 . The size of the entire operation unit  80  including the band  92  (the volume occupying the space) when the band  92  is stored in the groove  93  is smaller than the size thereof in a state where the band  92  protrudes from the bottom side of the operation unit  80 . More specifically, forming the groove  93  on the bottom side of the operation unit  80  enables downsizing the operation unit  80 . The band  92  not protruded from the bottom side of the operation unit  80  also provides an effect of improving the appearance. If the band  92  partly protrudes from the bottom side of the operation unit  80  in a state where the operation unit  80  is placed on the top surface  109 , a certain number of users may feel that the appearance is degraded. Since the band  92  can be stored in the groove  93  when the band  92  is not in use, the above-described degradation in appearance can be prevented. Further, when the band  92  is stored in the groove  93 , the band  92  does not protrude from the virtual plane determined by the rubber bases  85 . Accordingly, it is possible to reduce the possibility of the band  92  partly coming into contact with the top surface  109  and the operation unit  80  wobbling when the operation unit  80  is placed on the top surface  109 . When the band  92  is not in use, i.e., when the operation unit  80  is not placed on the palm, the operation unit  80  is often placed on the top surface  109 . The band  92  can be stored in the groove  93  formed on the bottom side of the operation unit  80 . Therefore, even when the user operates the operation unit  80  on the top surface  109 , the operation unit  80  can be used in a stable way without wobble. 
     Methods for putting the band  92  into and out of the groove  93  will be described below with reference to  FIGS.  10 A and  10 B . As illustrated in  FIGS.  10 A and  10 B , an oblong hole  95  is formed at one end side of the band  92 . The one end side of the band  92  is fixed to the bottom side of the operation unit  80  by a screw  94   b  via the oblong hole  95 . More specifically, the one end side of the band  92  can slide with respect to the operation unit  80  within the range of the oblong hole  95 . The other end side of the band  92  is fixed to the bottom side of the operation unit  80  by a screw  94   a . When one end side of the band  92  is slid toward the other end side, a central portion of the band  92  is bent. The bent portion of the band  92  protrudes from the groove  93 , making it easier for the user to put the fingertips through the band  92 . When the one end side of the band  92  is slid away from the other end side, the bent portion of the band  92  is stretched and the entire band  92  is stored in the groove  93 . Although, in the present exemplary embodiment, only one end side of the band  92  is configured to be slidable with respect to the bottom side of the operation unit  80 , both the one end side and the other end side may be configured to be slidable with respect to the bottom side of the operation unit  80 . 
     As described above, if the band  92  is not configured in such a way that the one end side or both end sides of the band  92  is slidably attached to the bottom side of the operation unit  80 , pushing the band  92  into the groove  93  when not in use may be considered as a method for storing the band  92 . In such a method, the band  92  may partly protrude from the groove  93  by its own weight when the user holds up the operation unit  80 . On the other hand, if the band  92  is configured in such a way that one end side or both end sides of the band  92  is slidably attached to the bottom side of the operation unit  80 , it is possible to reduce the possibility that the band  92  partly protrudes from the groove  93  by its own weight when the user holds up the operation unit  80 . To allow the band  92  to bend, one end side or both end sides of the band  92  need to slide with respect to the bottom side of the operation unit  80 . However, a frictional force corresponding to the sliding is generated. The possibility that the band  92  protrudes from the groove  93  is low as long as the bending force by its own weight is smaller than the frictional force. 
       FIG.  10 C  illustrates an exterior cover on the bottom side of the operation unit  80 . As illustrated in  FIG.  10 C  (and  FIG.  8 A ), the exterior cover of the operation unit  80  is provided with two rubber bases  85   a  and two rubber bases  85   c .  FIG.  10 C  illustrates the bottom side of the operation unit  80  viewed along the direction perpendicular to the plane determined by the four rubber bases  85   a  and  85   c . A method for determining the plane has been described above with reference to  FIGS.  6 A to  6 C . 
     As illustrated in  FIG.  10 C , the band  92  is located within the region surrounded by the four rubber bases  85   a  and  85   c . When the operation unit  80  is placed on the top surface  109 , the band  92  is stored between the top surface  109  and the exterior cover on the bottom side of the operation unit  80 . For example, if the band  92  is leather, the bent band  92  has a restoring force to return to the shape before it was bent. Accordingly, the band  92  pushes up the operation unit  80  with respect to the top surface  109 . In other words, the band  92  may function as the fifth base. If the fifth base is formed outside the region surrounded by the four rubber bases  85   a  and  85   c , the orientation of the operation unit  80  placed on the top surface  109  may possibly be inclined. According to the present exemplary embodiment, the band  92  is provided within the region surrounded by the four rubber bases  85   a  and  85   c . Thus, it is possible to reduce the possibility that the orientation of the operation unit  80  inclines even when the operation unit  80  is placed on the top surface  109 . 
       FIG.  11 A  is a cross-sectional view illustrating the operation unit  80 .  FIG.  11 A  is an enlarged view illustrating attachment portions of the band  92  to the bottom side of the operation unit  80  (attachment regions  92   a  and  92   b ). As illustrated in  FIG.  11 A , a bottom  93   a  of the groove  93  is provided with the attachment portions  92   a  and  92   b , supporting regions  92   d  and  92   e , and a depression  92   c . The band  92  is attached to the bottom  93   a . More specifically, the band  92  is attached to the attachment portions  92   a  and  92   b  of the bottom  93   a . The depression  92   c  is formed between the attachment portion of the band  92  to the bottom side of the operation unit  80  at one end side of the band  92  (the attachment region  92   a ) and the attachment portion of the band  92  to the bottom side of the operation unit  80  at the other end side of the band  92  (attachment region  92   b ). The supporting regions  92   d  and  92   e  for supporting parts of the band  92  exist to the right and left of the depression  92   c , respectively. 
     More specifically, the supporting regions  92   d  and  92   e  are adjacent to the depression  92   c . When the bottom side of the operation unit  80  is upwardly oriented in the vertical direction, the depression  92   c  is located below the band  92 . In this state, a part of the band  92  covers the depression  92   c . The supporting regions  92   d  and  92   e  support parts of the band  92 . Since the depression  92   c  more concave than the supporting regions  92   d  and  92   e  is formed at the bottom  93   a , the user can easily put the fingertips through the band  92 . 
     As illustrated in  FIG.  11 B , an inclined surface  93   b  is formed toward the bottom of the groove  93  more on the front side than the groove  93 . The inclined surface  93   b  makes it easier for the user to put the fingertips into the groove  93  and then the depression  92   c  by sliding the fingertips along the inclined surface  93   b.    
     When one end side and the other end side of the band  92  are slid all the way toward the center of the band  92 , i.e., the band  92  is bent as much as possible, the space formed between the band  92  and the bottom side of the operation unit  80  is at least 30 mm in height and at least 90 mm in width. A space of this size enables the user to sufficiently put the palm between the band  92  and the bottom side of the operation unit  80 . The operation to “put the palm through the band” is defined as an operation to put the four fingers other than the thumb (index finger, middle finger, annular finger, and little finger) through the band  92 . The state where the palm is put through the band  92  refers to a state where the second joints of the index finger, middle finger, and annular finger, and the first joint of the little finger are put through the band  92 . More specifically, the user operates the operation unit  80  in a state where the fingertips are put through the band  92 . According to the exemplary embodiment, “the state where the palm is put through the band” and “the state where the fingertips are put through the band” means substantially the same state. According to the present exemplary embodiment, the space formed between the band  92  and the bottom side of the operation unit  80  is 35 mm in height and 100 mm in width. 
     As illustrated in  FIG.  12   , the height (h) of the space is determined by the height from the virtual line Q connecting the supporting regions  92   d  and  92   e  to the center of the band  92 . The height of the space refers to the distance from the center point of the virtual line Q to the intersection between the line perpendicular to the virtual line Q and the band  92 . The width (W) of the space refers to the value determined by the distance from the attachment portion of the band  92  to the bottom side of the operation unit  80  at one end side of the band  92  to the attachment portion of the band  92  to the bottom side of the operation unit  80  at the other end side of the band  92 . When the height and width of the space are measured, as illustrated in  FIG.  12   , the band  92  is bent so that the shape of the space becomes a rectangular parallelepiped. The space formed in this way is the space through which the user puts the palm. 
     According to the experiment of the inventor, 35 mm and 100 mm were obtained as most suitable values of the height and width of the space, respectively, based on the size of the user&#39;s palm. As described below, it is preferable that the height falls within a range from 30 to 60 mm and the width falls within a range from 90 to 180 mm depending on the material of the band  92 . If the height and width of the space are small, the palm of some users does not fit into the space. From this viewpoint, lower limits of the height and width of the space are determined to be 30 mm and 90 mm, respectively. On the other hand, if the height and width of the space are too large, the operation unit  80  slides along the palm by a large moving amount when the user twists the wrist. This increases the possibility of the band  92  slipping down from the palm. From this viewpoint, upper limits of the height and width of the space are determined to be 60 mm and 180 mm, respectively. 
     The band  92  according to the present exemplary embodiment is mainly composed of nylon having some elasticity which is not as large as that of rubber. This intends to minimize the tightening on the palm felt by the user who puts the palm between the band  92  and the bottom side of the operation unit  80 . Since the users have various sizes of the palm, some users mind the tightening on the palm by the band  92 . Accordingly, the band  92  according to the present exemplary embodiment is a nylon band having elasticity not as large as that of rubber. 
     Meanwhile, the use of rubber as the material of the band  92  enables reducing the possibility of the operation unit  80  slipping down from the palm. More specifically, the use of rubber reduces the possibility of the operation unit  80  sliding and slipping down from the palm when the user twists the wrist. The possibility of the state transition from the state in  FIG.  9 A  to the state in  FIG.  9 B  can be reduced. This ensures the stability of the orientation of the operation unit  80  on the palm. The material of the band  92  needs to be determined by comparing the degree of tightening on the palm by the band  92  with the stability of the orientation of the operation unit  80  on the palm. 
     Positional Relation Between Band and Cable 
       FIGS.  13 A and  13 B  illustrate the positional relation between the band  92  and the cable  90 .  FIG.  13 A  is a schematic view illustrating the operation unit  80  viewed from the left-hand side of the operation unit  80 . Referring to the example in  FIG.  13 A , the cable  90  is lead out from the wall on the rear side of the operation unit  80 . 
     The band  92  is provided on the bottom side of the operation unit  80 . Therefore, when the user puts the palm through the band  92 , the palm is in contact with the bottom side of the operation unit  80 . The position where the cable  90  is lead out from the operation unit  80  is more on the rear side than the band  92 . Therefore, there is an extremely low possibility that the cable  90  gets into the space between the user&#39;s palm put through the band  92  and the bottom side of the operation unit  80 . If the cable  90  exists between the palm and the bottom side of the operation unit  80 , it becomes difficult to stably place the operation unit  80  on the palm. Therefore, by disposing the band  92  on the bottom side of the operation unit  80  and leading out the cable  90  from the rear side of the operation unit  80  as described above, the operability of the operation unit  80  with the user&#39;s palm put through the band  92  improves. 
     The user can easily determine whether the position where the cable  90  is lead out from the operation unit  80  is more on the rear side than the band  92  by viewing the operation unit  80  placed on the top surface  109 . Firstly, the user places the operation unit  80  on the top surface  109  and then takes the posture in which he/she normally uses the operation unit  80 . More specifically, the user stands in the front of the image forming system  1 . In this case, the cable  90  extends from the operation unit  80  toward the rear side of the image forming system  1 . In this state, the user determines whether the position where the cable  90  is lead out from the operation unit  80  is more on the rear side than the band  92 . 
     In the example in  FIG.  13 B , the cable  90  is lead out from the bottom side of the operation unit  80  and then lead toward the rear side of the operation unit  80 . As illustrated in  FIG.  13 B , the cable  90  is lead out from the bottom side of the operation unit  80 . The lead-out opening is formed more on the rear side than the groove  93  where the band  92  is attached. A retaining member  96  for retaining a part of the cable  90  to the operation unit  80  is disposed more on the rear side than the lead-out opening. 
     Since the retaining member  96  is disposed more on the rear side than the lead-out opening, the cable  90  extends from the lead-out opening toward the rear side of the operation unit  80 . The interference between the band  92  and the cable  90  can be prevented by disposing the lead-out opening more on the rear side than the band  92  and disposing the retaining member  96  more on the rear side than the lead-out opening in this way. More specifically, it is possible to reduce the possibility of the cable  90  getting into the space between the user&#39;s palm put through the band  92  and the bottom side of the operation unit  80 . This configuration also improves the operability of the operation unit  80  with the user&#39;s palm put through the band  92 . 
     Band Premised on Passing of Fingers (Modification) 
       FIGS.  14 A and  14 B  illustrate the band  92  disposed on the operation unit  80  on the assumption that one or two fingers are put through the band  92 . The attachment configuration of the band  92  to the bottom side of the operation unit  80 , and the slide configuration of the band  92  to the bottom side of the operation unit  80  are similar to the configurations according to the above-described first exemplary embodiment. The configuration of the present modification is different from that of the above-described first exemplary embodiment only in the size of the space formed between the band  92  and the bottom side of the operation unit  80 . 
     The height and width of the space formed in the configuration according to the present modification are both 30 mm assuming that only one finger is put through the band  92 , or 30 mm and 60 mm, respectively, assuming that two fingers are put through the band  92 . The size of the space is determined for the same reason as that according to the first exemplary embodiment. 
     It is desirable that the height of the space falls within a range from 25 to 40 mm, and the width of the space falls within a range from 25 to 70 mm. The definition of the space measuring method is the also same as that according to the first exemplary embodiment. 
     Band Disposed at Positions Other than Arm (Second Exemplary Embodiment) 
       FIGS.  15 A and  15 B  illustrate the configuration in which the band  92  is disposed at positions other than the arm  822 . As illustrated in  FIGS.  15 A and  15 B , the band  92  is attached to the bottom side of the operation unit  80  more on the front side than the arm  822 . More specifically, the band  92  can also be attached to the operation unit  80  not having the arm  822 . 
     Even with the operation unit  80  having the arm  822 , the band  92  may be disposed at positions other than the arm  822 . When the band  92  is disposed on the arm  822 , the orientation of the arm  822  may slightly change when the user bends the fingers with the operation unit  80  placed on the palm. More specifically, when the relative positional relation between the arm  822  and the operation unit  80  changes, the relative positional relation between the palm and the operation unit  80  also changes. Some users may consider that the position change of the operation unit  80  on the palm is not desirable. Thus, according to the second exemplary embodiment, the band  92  is directly attached to the operation unit  80 . The band  92  attached in this way provides a more stable orientation of the operation unit  80  on the palm. 
     On the other hand, from the viewpoint of design flexibility for the operation unit  80 , the configuration of the second exemplary embodiment also has disadvantages. The operation unit  80  mounts a large number of parts including a circuit board, a touch panel, and a liquid crystal panel. In addition, it is demanded that the operation unit  80  is more compactly designed to improve the appearance and operability. More specifically, although the operation unit  80  needs to mount more parts to enhance its functions, the operation unit  80  needs to be designed to minimize the occupied volume. Forming the groove  93  for storing the band  92  and a position for fixing the band  92  on the operation unit  80  may cause limitations on the location of the circuit board inside the operation unit  80 . More specifically, the design flexibility of the operation unit  80  decreases. The arm  822  includes no circuit board member and stores a small number of parts. Therefore, the arm  822  often provides more space for forming the groove  93  than the main body of the operation unit  80 . As described above, from the viewpoint of orientation stability of the operation unit  80  on the palm, the configuration for directly attaching the band  92  to the operation unit  80  is more preferable than the configuration for providing the arm  822 . On the other hand, from the viewpoint of the improvement in design flexibility of the operation unit  80 , the configuration for attaching the band  92  to the arm  822  is more preferable than the configuration according to the second exemplary embodiment. 
     Arm Having Function of Band (Third Exemplary Embodiment) 
       FIGS.  16 A and  6 B  illustrate an example where the arm  822  has a function equivalent to the band  92 .  FIG.  16 A  is a perspective view illustrating the operation unit  80  with the arm  822  closed.  FIG.  16 B  is a perspective view illustrating the operation unit  80  with the arm  822  opened. As illustrated in  FIG.  16 B , the arm  822  has an opening  91  formed near the center. The user is able to put the palm through the opening  91 . 
     More specifically, when the user wants to hold the operation unit  80 , the user opens the arm  822 . 
     The size of the opening  91  is equivalent to the size of the space formed by the band  92  according to the first and the second exemplary embodiments. 
     Forming the opening  91  for putting the palm through the arm  822  itself in this way eliminates the need of providing a new member equivalent to the band  92 . The arm  822  can be assigned a function of supporting the operation unit  80  and a function of a member through which the palm is put. This configuration reduces the number of parts and the production cost. 
     In the configuration according to third exemplary embodiment, on the other hand, the user needs to purposely open the arm  822  to put the palm through the opening  91 . This configuration also has a disadvantage that the arm  822  itself is increased in size to ensure a sufficient size of the opening  91  to put the palm through the opening  91 . Any limitation on the size of the arm  822  means the reduction in design flexibility of the arm  822 . Using the band  92  as in the first and the second exemplary embodiments resolves the above-described disadvantages. 
     As described above, the configurations according to the first to the third exemplary embodiments have an effect of reducing the possibility of the operation unit  80  slipping down from the palm and hits the floor. Since each exemplary embodiment has advantages and disadvantages in addition to the above-described effect, the exemplary embodiments may be suitably used according to the required effect. 
     Operation Unit Capable of Wireless Communication (Fourth Exemplary Embodiment) 
     In the above-described exemplary embodiments, the operation unit  80  is connected to the image forming apparatus  2  via the cable  90 . However, the operation unit  80  may wirelessly communicate with the image forming apparatus  2 . 
       FIG.  17    illustrates a system configuration of the image forming apparatus  2  capable of wirelessly communicating with the operation unit  80 . As illustrated in  FIG.  17   , the image forming apparatus  2  includes a DCON control unit  10 , an SCON control unit  200 , and an RCON control unit  300  as control units for controlling the image forming apparatus  2  when the power voltage is supplied from the power source apparatus  17 . 
     The DCON control unit  10  controls various conveyance members, drive units such as motors for driving the image forming unit  15 , and sensors such as a sheet detection sensor of the image forming apparatus  2 . The SCON control unit  200  controls the entire image forming apparatus  2 , more specifically, communication with an external apparatus via an interface (not illustrated) and image processing. For more details, the SCON control unit  200  is capable of receiving an image forming job, transmitting main body information for the image forming apparatus  2 , and controlling image processing for an image read by a reader  14  and image data received from an external apparatus. The RCON control unit  300  performs various control for the reader  14  and the post-processing apparatus  16 . 
     A state where a power switch  79  is turned ON means a state where the image forming apparatus  2  is activated. More specifically, this state is a state where the power source apparatus  17  is supplied with commercial power via an outlet, and power voltages are supplied from the power source apparatus  17  to the DCON control unit  10 , the SCON control unit  200 , and the RCON control unit  300 . 
     When the image forming apparatus  2  is connected to a commercial power source, the power source apparatus  17  supplies a +5V power voltage to the SCON control unit  200  as a night power source. When the power switch  79  is turned ON, the power source apparatus  17  are capable of supplying a +12V and a +24V power voltage to the DCON control unit  10 , the SCON control unit  200 , and the RCON control unit  300  as non-night power sources. Although the present exemplary embodiment is configured to control the control units by supplying a plurality of different voltages thereto, the magnitudes and types of voltages are not limited to this configuration. 
     The DCON control unit  10  includes a CPU  11 , a ROM  12 , and a RAM  13  as built-in modules. The DCON control unit  10  is connected with the image forming unit  15  and a display panel  71  ( FIG.  2    and  FIG.  17   ). The DCON control unit  10  is also connected with a network connection unit  84  for connecting with external apparatuses (not illustrated) via a network. 
     The ROM  12  stores various image data and various programs for controlling the image forming apparatus  2 . The CPU  11  executes various calculation processing based on the control programs stored in the ROM  12 . The RAM  13  temporarily stores data. More specifically, the CPU  11  controls the image forming unit  15 , the reader  14  connected to the CPU  130 , and the post-processing apparatus  16  by using the RAM  13  as a work area based on the control programs stored in the ROM  12  to perform the above-described image forming operation. 
     The DCON control unit  10  is connected with a panel connection unit  800  for connecting with the operation unit  80 . The panel connection unit  800  includes a power feed connector  730   a , a panel attachment unit  730  to which the operation unit  80  is connected, and a wireless communication unit  810  that wirelessly communicates with the operation unit  80 . The power feed connector  730   a  of the panel attachment unit  730  is connected with a charging connector  55  of the operation unit  80 . 
     The wireless communication unit  810  includes a command communication unit  825  (transmission unit and reception unit) and an image transmission unit  830 . The CPU  11  reads an image stored in the ROM  12  and then transmits the image to the operation unit  80  via the image transmission unit  830  of the wireless communication unit  810 . The CPU  11  also generates an instruction to the operation unit  80  and transmits the instruction to the operation unit  80  via the command communication unit  825 . The CPU  11  also receives a notification and instruction generated by the operation unit  80 , via the command communication unit  825 . Although, in the present exemplary embodiment, the command communication unit  825  and the image transmission unit  830  are configured as separate units, the two units may be integrated into a single communication line. 
     The image forming apparatus  2  and the operation unit  80  wirelessly communicate with each other via Wi-Fi (registered trademark) direct communication, which is a communication form of direct wireless connection between apparatuses. More specifically, in this example, the image forming apparatus  2  and the operation unit  80  wirelessly communicate with each other without a server&#39;s intervention. Miracast, a display transmission technique applied with the Wi-Fi direct communication method, is used for mobile phones, displays, and projectors. The wireless communication system is not limited to the Wi-Fi direct communication method but may be configured to, for example, perform wireless communication by using a Wi-Fi router as an access point. However, from the security viewpoint, the Wi-Fi direct communication method is preferable. Also, instead of the Wi-Fi wireless communication method, the wireless communication system may be configured to perform wireless communication based on other methods such as Bluetooth (registered trademark) and Near Field Communication (NFC). 
     “Remote access” is known as a method for accessing other electronic apparatuses and various types of servers on remote locations from an electronic apparatus such as a personal computer (PC) and tablet terminal. Examples of remote access forms include a Virtual Private Network (VPN) method. VPN refers to a mechanism for building a virtual dedicated network on the Internet. This system generally employs a method called “Tunneling” for performing communication by building a virtual tunnel during data transmission and reception. Further, a technique called “Encapsulation” may be used to protect data from vicious intrusion into the tunnel, thus maintaining security. Since a VPN-based communication method performs communication via the Internet as described above, it is different from the method of communication between the operation unit  80  and the image forming apparatus  2  according to the present exemplary embodiment. 
     Another method called a screen transmission method transfers the screen of a target electronic apparatus such as a PC and tablet terminal to the screen of the currently operating electronic apparatus via the Internet. When performing this screen transfer, electronic apparatuses are connected with VPN via a relay server. 
     The DCON control unit  10  is connected with the power source apparatus  17 . The power source apparatus  17  receives power supplies from a commercial power source via an outlet plug  19 , converts the power into power to be used in each device, and supplies the power to each device. More specifically, when the main power switch  79  is turn ON from OFF, the power source apparatus  17  supplies power to the DCON control unit  10 . Subsequently, the power source apparatus  17  supplies power to the reader  14 , the image forming unit  15 , the post-processing apparatus  16 , the display panel  71 , the operation unit  80  attached to the panel attachment unit  730 , the wireless communication unit  810 , and the network connection unit  84  based on an instruction of the DCON control unit  10 . 
     The SCON control unit  200  including a CPU  120  controls the system of the entire image forming apparatus  2  and image processing on an image read by the reader  14 . Since the SCON control unit  200  controls the entire image forming apparatus  2 , a +5V power voltage is constantly supplied when the image forming apparatus  2  is connected to a commercial power source. 
     Then, the RCON control unit  300  including a CPU  130  controls the reader  14  and the post-processing apparatus  16 . The RCON control unit  300  outputs the image read via the reader  14  to the CPU  120 . Thus, the CPU  120  generates image processing information to be used for image forming performed by the DCON control unit  10  by controlling drive motors. 
     The DCON control unit  10 , the SCON control unit  200 , and the RCON control unit  300  are not limited to the above-described configuration but may include an Application Specific Integrated Circuit (ASIC) and other CPUs to perform each control. 
     The image forming apparatus  2  according to the present exemplary embodiment is able to shift to a plurality of states such as a standby mode in which the image forming operation can be performed, and a sleep mode in which the power voltage supply to each control unit is limited, i.e., a power-saving state where the power consumption is lower than that in the state where the image forming operation is enabled. The standby mode refers to a state where the power switch  79  is turned ON, and the power voltages are supplied to the DCON control unit  10 , the SCON control unit  200 , and the RCON control unit  300 . More specifically, the standby mode refers to a state where the power voltages are supplied to all of the control units and the image forming operation is enabled. 
     The sleep mode refers to a state where the power voltage is supplied to the SCON control unit  200  but no power voltages are supplied to the DCON control unit  10  and the RCON control unit  300 . 
     The transition from the sleep mode to the standby mode and vice versa is performed when the user (operator or service engineer) operates a sleep key (not illustrated) provided on the operation unit  80 . At this timing, when the sleep key of the operation unit  80  is operated, a sleep signal is output from the operation unit  80  to the power source apparatus  17 . Thus, the power source apparatus  17  controls the DCON control unit  10 , the SCON control unit  200 , and the RCON control unit  300 , and the image forming apparatus  2  enters the sleep mode. The image forming apparatus  2  may enter the sleep mode from the power switch ON state when no operation is made on the image forming apparatus  2  for a predetermined time period, i.e., a predetermined time period has elapsed since no image forming instruction is issued to the image forming apparatus  2 . The predetermined time period in this case may be preset to 60 seconds, for example, or may be arbitrarily set by the user. 
     This predetermined time period is measured by a timer (counter)  202  controlled by the DCON control unit  10 . The timer  202  measures the time period during which no image forming instruction is issued to the image forming apparatus  2  by the user. The timer  202  may measure the actual time or count a unique count value based on the actual time. When counting a count value, the timer  202  may count up (for example, 1 second, 2 seconds, 3 seconds, . . . ) or count down (for example, 60 seconds, 59 seconds, 58 seconds, . . . ). According to the present exemplary embodiment, the issuance of an image forming instruction to the image forming apparatus  2  refers to, for example, the transmission of a print job to the image forming apparatus  2 . The timing when no image forming instruction is issued refers to the timing when the image forming processing by the image forming unit  15  is completed. More specifically, the timing when no image forming instruction is issued is the timing when photosensitive drums stop rotating. However, this timing is not limited to the timing when the photosensitive drums stop rotating but may be, for example, the timing when an intermediate transfer belt stops rotating or the timing when paper with a toner image transferred thereon is discharged to a discharge tray  16   a.    
     The system configuration of the operation unit  80  capable of wirelessly communicating with the image forming apparatus  2  will be described below.  FIG.  18    illustrates a system configuration of the operation unit  80 . As illustrated in  FIG.  18   , the operation unit  80  includes a control unit  67  including a CPU  68 , a ROM  69  (storage unit), a RAM  36 , and a timer  37 . The timer  37  measures time when the control unit  67  performs various processing. 
     The ROM  69  stores data such as various programs for controlling the operation unit  80 . The CPU  68  performs various calculation processing based on the control programs stored in the ROM  69 . The RAM  36  temporarily stores data. More specifically, the CPU  68  controls a display  82 , a speaker unit  38 , and a lighting unit  39  connected to the control unit  67  by using the RAM  36  as a work area based on the control programs stored in the ROM  69 . 
     The operation unit  80  includes a connection unit  900  for connecting with the image forming apparatus  2 . 
     The connection unit  900  includes a charging connector  55  to be connected to the power feed connector  730   a  of the image forming apparatus  2 , and a wireless communication unit  910  that wirelessly communicates with the image forming apparatus  2 . 
     The wireless communication unit  910  includes a command communication unit  920  connected to the CPU  68 , and an image reception unit  930  connected to the display  82 . The CPU  68  generates an instruction or notification for the image forming apparatus  2 , and transmits the instruction or notification to the command communication unit  825  ( FIGS.  17  and  19   ) of the image forming apparatus  2  via an antenna (not illustrated) of the command communication unit  920 . The CPU  68  receives an instruction and information transmitted from the command communication unit  825  of the image forming apparatus  2  via the command communication unit  920 . 
     The image reception unit  930  receives image data transmitted from the image transmission unit  830  of the image forming apparatus  2  via an antenna (not illustrated), converts the image data into image data to be displayed on the display  82 , and displays the image data on the display  82 . Although, in the present exemplary embodiment, the command communication unit  920  and the image reception unit  930  are configured as separate units, the two units may be integrated into a single communication line. 
     The operation unit  80  also includes a panel power source unit  56 . The panel power source unit  56  includes a battery  57  and a power generation unit  58 . The battery  57  is the main power source of the operation unit  80  and includes a rechargeable battery. When a charging connector  55  is connected to the power feed connector  730   a  of the image forming apparatus  2 , power is supplied from the power source apparatus  17  of the image forming apparatus  2  to the battery  57 , and the battery  57  is charged. The power generation unit  58  also adjusts the power of the battery  57  to a voltage that can be used by each device included in the operation unit  80 . When the power of a power switch  52  is turned ON from OFF, the battery  57  is charged, and the power adjusted by the power generation unit  58  is supplied to the control unit  67 , the display  82 , the speaker unit  38 , the lighting unit  39 , and the connection unit  900 . 
     The wireless communication between the image forming apparatus  2  and the operation unit  80  will be described below. 
       FIG.  19    is a communication state transition diagram of the image forming apparatus  2  and the operation unit  80 . A sequence of wireless communication between the image forming apparatus  2  and the operation unit  80  will be described. In step S 11 , the user operates the power switch  79  to activate the image forming apparatus  2 . In step S 21 , the user operates a power switch  26  to activate the operation unit  80 . 
     When the operation unit  80  is activated, then in step S 22 , the command communication unit  920  of the operation unit  80  transmits a negotiation request to the command communication unit  825  of the image forming apparatus  2 . 
     In step S 12 , the command communication unit  825  of the image forming apparatus  2  transmits a response signal to the command communication unit  920  of the operation unit  80 . When the operation unit  80  receives the response signal, the connection sequence ends and wireless communication is established. 
     In steps S 13  and S 23 , the image forming apparatus  2  and the operation unit  80  mutually set wireless communication conditions, such as the transmission rate and the image compression ratio, via the command communication units  825  and  920 . Upon completion of the wireless communication setting, then in step S 14 , the image transmission unit  830  of the image forming apparatus  2  transmits an image signal stored in the ROM  69  of the image forming apparatus  2  to the image reception unit  930  of the operation unit  80  according to an instruction of the CPU  11  of the image forming apparatus  2 . 
     Then, the image reception unit  930  of the operation unit  80  converts the received image signal and displays the image on the display  82 . When the user operates the display  82 , then in step S 24 , the CPU  68  of the operation unit  80  transmits operation information of the display  82  to the command communication unit  825  of the image forming apparatus  2  via the command communication unit  920 . 
     The CPU  68  transmits the operation information of the display  82  to the image forming apparatus  2  as coordinate information. The coordinate information will be described below.  FIG.  20    illustrates the display  82  of the operation unit  80  provided with coordinate display. As illustrated in  FIG.  20   , the display  82  is divided in each of the X- and the Y-directions. The number of divisions depends on the type of the touch panel. With the resistance type touch panel according to the present exemplary embodiment, the display  82  is divided into 2,048 in the X direction and 1,024 in the Y direction. 
     A position on the touch panel is represented by the coordinates (X, Y) according to the distance from the reference point, i.e., the origin (0, 0). 
     For example, referring to  FIG.  20   , a position P is located at 1,024 in the X direction and 512 in the Y direction from the origin, and is represented by the coordinates (1024, 512). Coordinate data is transmitted from the touch panel  59  of the display  82  to the CPU  68  of the operation unit  80 , and then transmitted from the command communication unit  920  to the image forming apparatus  2  according to an instruction of the CPU  68 . According to the present exemplary embodiment, since the communication between the image forming apparatus  2  and the operation unit  80  is based on the 8-bit length, the numerical value of the coordinate data is divided by 8 before transmission. More specifically, the coordinates (1024, 512) are replaced with (128, 64). 
     The CPU  11  of the image forming apparatus  2  determines the position on the display  82  of the operation unit  80  touched by the user based on input coordinate data. In steps S 15  and S 16 , according to the touched position, the CPU  11  issues an instruction for transmitting image data, an instruction for lighting control for the lighting unit  25 , and an instruction for turning the sound of the speaker unit  38  ON or OFF, to the operation unit  80 . Also, at timing other than the reception of the operation information of the display  82  from the operation unit  80 , the image forming apparatus  2  issues the above-described instructions to the operation unit  80  according to the states of the image forming apparatus  2  and the operation unit  80 . 
     As described above, possible forms of the operation unit  80  include a form of wired communication and a form of wireless communication with the image forming apparatus  2 . Either in a form of wired communication or in a form of wireless communication between the image forming apparatus  2  and the operation unit  80 , the user can hold up the operation unit  80 . Disposing the band  92  on the bottom side of the operation unit  80  enables reducing the possibility of the operation unit  80  slipping down from the palm and hitting the floor, regardless of whether the operation unit  80  employs a wired communication method or a wireless communication method. 
     While the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the disclosure is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2021-015971, filed Feb. 3, 2021, which is hereby incorporated by reference herein in its entirety.