Abstract:
Each of a plurality of connected optional apparatuses includes a sliding member slidable in a direction of connection, and a display provided in the sliding member, the display having a plurality of unique identifiers. The sliding member is movable while contacting a sliding member of an adjacent one of the plurality of optional apparatuses, and when the plurality of optional apparatuses are connected, a moving amount of a sliding member of each of the plurality of optional apparatuses differs, and therefore displays a different unique identifier.

Description:
This application is a divisional of U.S. patent application Ser. No. 10/893,353, filed Jul. 19, 2004, and allowed Aug. 24, 2006. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a plurality of connected optional apparatuses, such as external sheet feeding apparatuses or external sheet discharging apparatuses, that are connected to an image forming apparatus, and to an image forming apparatus, such as a copier, a facsimile apparatus, and a printer, that can be connected to the optional apparatuses. 
   2. Description of the Related Art 
   An image forming apparatus is often configured to increase a sheet feeding capacity and a discharged-sheet mounting capacity by including a plurality of external sheet feeding apparatuses, such as optional feeders, or external sheet discharging apparatuses, such as optional trays, connected to the image forming apparatus. Such external apparatuses (hereinafter termed “optional apparatuses”) are generally disposed below or above an image forming apparatus. In many cases, optional apparatuses can be stacked in several stages. 
   In an image forming apparatus connecting to these optional apparatuses, discrimination among the optional apparatuses is generally performed by providing each of the optional apparatuses with an identifier, such as a sheet-feeding-port number in an external sheet feeding apparatus, or a discharged-sheet-tray number in an external sheet discharging apparatus. That is, each optional apparatus is discriminated by being provided with an identifier, such as a numeral, a letter, or the like. 
   Conventionally, when there is an identifier for each optional apparatus when a plurality of optional apparatuses are used in a stacked state, for example, the process of attaching a label on which a corresponding identifier is printed is performed after installing an optional apparatus, and as a result the operation of installing optional apparatuses becomes complicated. 
   In order to solve such a problem, Japanese Patent Application Laid-Open (Kokai) No. 11-246059 (1999) discloses a configuration for allowing automatic switching of an identifier for a connected optional apparatus. 
   This conventional configuration will be described illustrating optional feeders, serving as external sheet feeding apparatuses. As shown in  FIG. 8 , a sliding member  4  having an projection  9  protruding upward is provided so as to be vertically slidable in each optional feeder  2 . The sliding member  4  is urged upward by a coil spring  7 . Two identifiers “ 2 ” and “ 3 ” are integrally formed on the sliding member  4  at constant intervals in a sliding direction. When optional feeder  2  is in one stage, the identifier “ 2 ” disposed downward from among the two identifiers is displayed from a display window  8  provided in the surface of a protective housing of the optional feeder  2 . A hole  11  in image forming apparatus  1  is provided at a position facing the projection  9  of the sliding member  4  of the uppermost optional feeder  2 . When connecting the uppermost optional feeder  2  to the lower surface of an image forming apparatus  1 , the projection  9  is inserted into the hole  11 . Since the sliding member  4  does not move, the identifier of the optional feeder  2  is a sheet-feeding-unit number “ 2 ” provided at the lower portion of the sliding member  4 . 
   Since the base of the optional feeder  2  is flat, when an optional feeder  2  of the second stage is connected below the uppermost or first optional feeder  2 , the projection  9  of the lower optional feeder  2  contacts the base of the uppermost optional feeder  2  to push the sliding member  4  downward against the spring force of the coil spring  7 . As a result, the identifier “ 3 ” provided at the upper portion of the sliding member  4  is displayed thru display window  8  provided on the surface of the protective housing, to set the sheet-feeding-unit number of the lower optional feeder  2  to “ 3 ”. 
   In the above-described conventional configuration, however, since switching of the identifier is performed using the optional apparatus disposed adjacent to the first optional apparatus and switching can be performed only between two types of identifiers, it is impossible to deal with a configuration allowing stacking of at least three external sheet feeding apparatuses. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a sheet feeding apparatus that allows automatic switching of a peculiar display even in optional apparatuses that can be stacked at least to three stages. 
   According to one aspect of the present invention, each of a plurality of connected optional apparatuses includes a sliding member slidable in a direction of connection, and a display member connected to the sliding member. The display member contains a plurality of unique identifiers. The sliding member is in contact with a sliding member of an adjacent one of the plurality of optional apparatuses. When the plurality of optional apparatuses are connected, a moving amount of the sliding member of each of the plurality of optional apparatuses differs from each other of the plurality of optional apparatuses, thereby displaying a different unique identifier of the display member of each optional apparatus. 
   According to another aspect of the present invention, an image forming apparatus includes a main body of the image forming apparatus, and the above-described optional apparatuses. 
   The foregoing and other objects, advantages and features of the present invention will become more apparent from the following description of the preferred embodiments taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a cross-sectional view illustrating unique numeric identifier units of an optional apparatus according to a first embodiment of the present invention; 
       FIG. 2  is a front view illustrating an image forming apparatus and the optional apparatuses according to the first embodiment; 
       FIG. 3  is a cross-sectional view illustrating the image forming apparatus and the optional apparatuses according to the first embodiment; 
       FIG. 4  is a cross-sectional view illustrating a unique numeric identifier unit of an optional apparatus according to a second embodiment of the present invention; 
       FIG. 5  is a cross-sectional view illustrating peculiar-number display units of optional apparatuses according to the second embodiment; 
       FIG. 6  is a front view illustrating an image forming apparatus and external sheet feeding apparatuses according to the second embodiment; 
       FIG. 7  is a side view illustrating the image forming apparatus and the external sheet feeding apparatuses according to the second embodiment; and 
       FIG. 8  is a front view illustrating a conventional image forming apparatus and external sheet feeding apparatuses. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   First Embodiment 
   The configuration of an image forming apparatus including sheet feeding apparatuses according to a first embodiment of the present invention will now be described. 
   In  FIG. 3 , a sheet feeding cassette  101  is detachably provided within an image forming apparatus  1 . A central plate  102  for mounting sheets is provided within the sheet feeding cassette  101 , and is urged upward by a spring (not shown). A pickup roller  103  for feeding sheets mounted on the central plate  102  is provided in the image forming apparatus  1 . A sheet fed by the pickup roller  103  is conveyed to registration rollers  105  by a pair of conveying rollers  104 . 
   An image forming portion includes a process cartridge  106  including a photosensitive drum  107 , serving as an image bearing member, a developing roller  109 , an optical unit  108  for irradiating a laser beam modulated by image information, and fixing means  111 . The sheet on which an image is formed by the image forming portion is conveyed by a pair of conveying rollers  112  to a discharged-sheet tray  113  which is disposed at an upper portion of the image forming apparatus  1 . 
   Optional feeders  2 , serving as optional apparatuses of the present invention, are connected in multiple stages (three stages in the first embodiment) below the image forming apparatus  1 . Each of the optional feeders  2  has a feeder main body  120  and a sheet feeding cassette  121  provided so as to be detachable with respect to the feeder main body  120 . 
   A central plate  122  for mounting sheets is provided in the sheet feeding cassette  121 , and is urged upward by a spring (not shown). The feeder main body  120  includes a pickup roller  131  for feeding sheets mounted on the sheet feeding cassette  121 , and a pair of conveying rollers  132 . The sheet is conveyed by the pair of conveying rollers  132  toward the registration rollers  105  of the image forming apparatus  1 . The optional feeders each have the same configuration, and can be replaced or exchanged. 
   An outline of operations of the image forming apparatus  1  will now be described. 
   An electrostatic latent image is formed on the photosensitive drum  107  according to an electrophotographic method by projecting a laser beam from the optical unit  108 . By causing a toner, serving as a developer, to adhere to the photosensitive drum  107  on which the electrostatic latent image has been formed, using the developing roller  109 , the latent image is developed to become a toner image. 
   A sheet fed from the sheet feeding cassette  101  within the image forming apparatus  1 , or from the sheet feeding cassette  121  within one of the optional feeders  2 , is conveyed to the pair of registration rollers  105 , and is fed at a timing in which the sheet is aligned with the position of an image on the photosensitive drum  107  by the pair of registration rollers  105 . The toner image on the photosensitive drum  107  is transferred onto the fed sheet by a transfer roller  110 . Then, the sheet is conveyed to the fixing means  111 , where the toner image is heated and fixed on the sheet. The sheet after image fixing is discharged onto the discharged-sheet tray  113  by the pair of conveying rollers  112 . 
   The first embodiment will now be described in detail with reference to  FIGS. 1 and 2 .  FIG. 1  is a cross-sectional view illustrating unique-number display units of optional feeders, serving as optional apparatuses.  FIG. 2  is a front view when the optional feeders are connected to the image forming apparatus  1 . 
   A first optional feeder  2  is connected to the image forming apparatus  1  by mounting the image forming apparatus  1  on the optional feeder  2  by adjusting the relative position between positioning pins (not shown) provided on the upper surface of the optional feeder  2  and reference holes (not shown) provided in the base of the image forming apparatus  1 . Reference holes are also provided in the base of the first optional feeder  2  as in the image forming apparatus  1 , so that another optional feeder  2  can be connected by being superposed on the lower surface of the first optional feeder  2 . A character “ 1 ” indicating the sheet-feeding-unit number of the sheet feeding cassette  101  is marked on the surface of the protective housing near the sheet feeding cassette  101  provided in the image forming apparatus  1 . 
   Next, the configuration and the operation of the unique-number display unit of the optional feeders  2  will be described with reference to  FIG. 1 . 
   A sliding member  4  is held on a display base  3  fixed on the frame of optional feeder  2  so as to be vertically slidable. The sliding member  4  includes a display unit in which three characters “ 2 ”, “ 3 ” and “ 4 ”, serving as unique displays indicating the numbers for the sheet feeding units of the optional feeders  2 , are arranged in the sliding direction of the sliding member  4  at constant intervals P, and a projection  9  upwardly formed from the display unit. 
   One end of a coil spring  7  provided in parallel to the sliding member  4  is connected to a boss  5  integrally formed on the display base  3 , and another end of the coil spring  7  is engaged with a hook  6  integrally formed on the sliding member  4  to urge the sliding member  4  upward in the plane of  FIG. 1 . At that time, the sliding member  4  is positioned by contacting an upper portion of the display base  3 . In this state, the number “ 2 ” is displayed in a display window  8  formed on the surface of the protective housing of the optional feeder  2 . 
   The projection  9  of the sliding member  4  protrudes from an upper portion of the optional feeder  2 . A hole  10  through which the projection  9  can be inserted is provided in the base of the optional feeder  2  and the lower surface of the display base  3  at a position facing the projection  9  of another optional feeder  2  disposed below the first optional feeder  2 . When the lower second optional feeder  2  is connected, the projection  9  of this optional feeder  2  is inserted into the hole  10  of the upper optional feeder  2 , so that the lower optional feeder  2  can contact the lower surface of the sliding member  4  of the upper first optional feeder  2 . 
   The length L from the upper end of the projection p to the lower end of the sliding member  4  is set so as to satisfy the following equation:
 
 L=H+P   (1),
 
where P is the interval between adjacent peculiar displays, and H is the height of the optional feeder  2 .
 
   A hole  11  through which the projection  9  can be inserted is provided in the base of the image forming apparatus  1  at a position facing the projection  9  protruding from the first optional feeder  2 . Since the projection  9  of the sliding member  4  of the optional feeder  2  on the upper surface of which the image forming apparatus  1  is placed is completely inserted into the hole  11  of the image forming apparatus  1 , the sliding member  4  does not move. Accordingly, the unique display “ 2 ” is displayed in the display window  8  of the optional feeder  2 . 
   When connecting two optional feeders  2 , the projection  9  of the lower optional feeder  2  enters the hole  10  of the first optional feeder  2  and contacts the lower surface of the upper sliding member  4 , whereby the projection  9  is pressed downward against the spring force of the coil spring  7 . In the case of the second optional feeder  2 , i.e., the optional feeder  2  connected below the first optional feeder  2  placed below the image forming apparatus  1 , the moving amount of the sliding member  4  equals P (one pitch of the unique number on the sliding member  4 ) from the above-described equation (1). Accordingly, the unique display “ 3 ” is displayed in the display window of the second optional feeder  2 . 
   In the case of the third optional feeder  2 , i.e., the optional feeder  2  connected below the second optional feeder  2 , the moving amount of the sliding member  4  equals 2×P (two pitches of unique numbers on the sliding member  4 ). Accordingly, the unique number “ 4 ” is displayed in the display window of the third optional feeder  2 . 
   As described above, because the moving amount of the sliding member  4  differs among the optional feeders  2  by a quantity of multiples of the pitch of the unique display, the unique display differs among the optional feeders  2 . Accordingly, the unique display of the optional feeder  2  is displayed as “ 2 ”, “ 3 ” and “ 4 ” starting from the uppermost optional feeder  2 , so that the respective optional feeders  2  can be discriminated as sheet-feeding-unit numbers “ 2 ”, “ 3 ” and “ 4 ”. 
   In the first embodiment, the height of the display base  3  is set so that the lower surface of the sliding member  4  substantially contacts the bottom of the display base  3  at a position where the sliding member  4  is slid downward by two pitches of unique numbers, in a state in which two optional feeders  2  are stacked above. Accordingly, when stacking the optional feeders  2  in at least four stages, the projection  9  cannot be inserted into the upper optional feeder  2 , and the optional feeder  2  in at least four stages from bottom cannot correctly be mounted. That is, when not intending to stack the optional feeders  2  in at least four stages, this configuration can be adopted. 
   When stacking the optional feeders in at least four stages, by setting the number of characters formed in the sliding member  4  to the largest necessary number of optional feeders to be stacked, and forming the sliding member  4  to a size satisfying the above-described equation (1), the optional feeders can be stacked in a necessary number of stages. When stacking the optional feeders  2 , a unique identifier is automatically displayed in the display window of the corresponding optional feeder. 
   As described above, by adopting the configuration of the first embodiment, it is possible to reduce the moving amount of the sliding member  4  necessary for switching the unique display, reduce the height of unique-display switching means, and stack a large number of optional apparatuses having a small height H. 
   The configuration of the unique-number display unit of the first embodiment may be applied to an optional tray to be described below. 
   Second Embodiment 
   A second embodiment of the present invention will now be described in detail with reference to  FIGS. 4-7 .  FIG. 4  is a detailed cross-sectional view illustrating a unique-number display unit according to the second embodiment.  FIG. 5  is a cross-sectional view illustrating a state of stacking optional trays, serving as optional apparatuses.  FIG. 6  is a front view illustrating an image forming apparatus to which the optional trays are connected.  FIG. 7  is a side view of the image forming apparatus and the optional trays. Components corresponding to those in the first embodiment will be indicated by the same reference numerals, and the description will be omitted for components having the same functions as those in the first embodiment. 
   The second embodiment differs from the first embodiment in that optional trays  20  capable of being stacked above an image forming apparatus are used, a display member  12  interlocked with a sliding member  4  is newly adopted, and alphabetical characters are adopted for unique displays of the optional trays  20 . 
   The optional tray  20  is for discharging a sheet on which an image has been formed in an image forming apparatus  1 , and can hold a large number of discharged sheets, or hold discharged sheets by selectively sorting the sheets. 
   In  FIG. 4 , a sliding member  4  is held on a display base  3  fixed on the frame of the optional tray  20  so as to be vertically slidable, and is urged downward by a coil spring  7 . A projection  9  of the sliding member  4  is integrally formed at a lower portion of a display unit, and protrudes from a lower portion of the optional tray  20 . 
   A hole  10  through which the projection  9  of the sliding member  4  of an optional tray  20  to be connected above can be inserted is provided in the upper surface of the optional tray  20  and the upper surface of the display base  3  at a position facing the projection  9 . When another optional tray  20  is connected above, the projection  9  of the sliding member  4  of this optional tray  20  is inserted into the hole  10  of the lower optional tray  20 , so as to contact the upper surface of the display unit of the sliding member  4  of the lower optional tray  20 . 
   A rack  15  parallel to the sliding direction of the sliding member  4  is integrally formed in the sliding member  4 . A disk-shaped display unit  12  is rotatably held around a shaft  13  integrally formed with the display base  3  at a side of the sliding member  4 . Characters “A”, “B”, “C” and “D”, serving as unique displays of the optional trays  20 , are integrally formed on the surface of the display member  12  on a circle having a radius of R around the shaft  13  by being arranged with a circular pitch of P. 
   A pinion  14  having a pitch-radius circle r and concentric with the shaft  13  is integrally formed on a back of the display member  12  opposite to the surface having the characters, and meshes with the rack  15  formed at the sliding member  4 . 
   When the moving amount of the sliding member  4  necessary for rotating the display member  12  around the shaft  13  by an amount of the pitch P is represented by m, m is obtained according to the following equation (2), from the relationship between the pitch-circle radius R of the circle where unique letters are arranged and the pitch-circle radius r of the pinion  14 :
 
 m=P×r/R   (2).
 
   In the second embodiment, when the length from the lower end of the projection  9  to the upper end of the sliding member  4  is represented by L, and the moving amount of the sliding member  4  necessary for rotating the display unit  12  by an amount of the pitch P is represented by m, and H is the height of optional tray  20 , the sliding member  4  is set so as to satisfy the following equation (3):
 
 L=H+m   (3).
 
   A hole  11  through which the projection  9  can be inserted is provided in the upper surface of the image forming apparatus  1  at a position facing the projection  9  of an optional tray  20  to be connected above. In the case of the optional tray  20  connected above the image forming apparatus  1 , since the projection  9  is completely inserted into the hole  11  of the image forming apparatus  1 , the sliding member  4  does not move. Accordingly, the unique letter display “A” is displayed in a display window  8  of the optional feeder  20  to which the image forming apparatus  1  is directly connected. 
   When further connecting another optional tray  20 , the projection  9  of the optional tray  20  to be disposed above enters the hole  10  of the lower optional tray  20  and contacts the upper surface of the sliding member  4  of the lower optional tray  20 , to be pushed upward against the spring force of the coil spring  7 . 
   When the optional tray  20  connected below is in one stage, the moving amount of the sliding member  4  is m in the above-described Equation (3). As described with reference to Equation (2), the display member  12  is rotated by one pitch of the unique display in accordance with the movement of the sliding member  4 . Accordingly, the unique display “B” is displayed in the display window  8  of the optional tray  20 . 
   When the optional trays  20  are connected below in two stages, the moving amount of the sliding member  4  is 2×m. According to Equation (2), the display member  12  is rotated by two pitches of the unique display in accordance with the movement of the sliding member  4 . Accordingly, the letter “C” is displayed in the display window  8  of the optional tray  20 . 
   Similarly, when the optional trays  20  are connected below in three stages, the moving amount of the sliding member  4  is 3×m, and the letter “D” is displayed in the display window  8  of the optional tray  20 . 
   As described above, the unique displays of the respective optional trays  20  are displayed as “A”, “B”, “C” and “D” starting from the lowest tray, and the respective optional trays can be discriminated as sheet-discharging-unit numbers “A”, “B”, “C” and “D”. 
   By thus connecting the optional trays  20  upward, the unique letter displayed in the display window  8  is automatically switched. When stacking the optional trays  20  in at least five stages, by setting the number of characters to be formed on the display member  12  to the maximum necessary number of stacked trays, and forming the sizes of the projection  9  and the sliding member  4  so as to satisfy the above-described Equations (2) and (3), the necessary number of stacked trays can be obtained. 
   That is, by appropriately setting the relationship between the radius R of the pitch circle where unique displays are arranged and the pitch-circle radius r of the pinion  14 , the moving amount of the unique display can be set to a value larger than the moving amount of the sliding member  4 . Accordingly, although when the number of connected optional trays  20  is increased, the moving amount of the sliding member  4  for switching is reduced, the moving amount of the display can be increased. Hence, it is unnecessary to reduce the size of the display. 
   The configuration of the unique identifier display unit of the second embodiment may also be applied to the optional feeder in the first embodiment. Although in the foregoing embodiments, numerals and alphabets are used as the peculiar numbers, any other appropriate display may be used, provided that respective optional apparatuses can be discriminated. 
   The individual components shown in outline in the drawings are all well known in the optional apparatus and image forming apparatus arts and their specific construction and operation are not critical to the operation or the best mode for carrying out the invention. 
   While the present invention has been described with respect to what are presently considered to be the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, the present invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.