Patent Publication Number: US-9423764-B2

Title: Image forming apparatus

Description:
FIELD OF THE INVENTION AND RELATED ART 
     The present invention relates to an image forming apparatus having a component which can be opened or closed. 
     Generally speaking image forming apparatuses have an image forming section which forms an image on a recording medium, and a recording medium feeding-conveying section which feeds a sheet of recording medium into the main assembly of the apparatus and conveys the sheet to the image forming section. Some image forming apparatuses are structured so that an image formation unit which functions as an image forming section, and a recording medium feeding-conveying tray, are removably mountable in the main assembly of the apparatus. 
     Also generally speaking, image forming apparatuses are equipped with a door (component which can be opened or closed relative to main assembly of apparatus), which is for allowing an image formation unit to be removably installed in the main assembly of the apparatus. The image forming apparatuses disclosed in Japanese Laid-open Patent Applications 2012-198444 and 2006-259148 are structured so that the space through which their door moves as the door is opened or closed overlaps with the space through which their recording medium feeding-conveying tray moves as the tray is mounted into, or dismounted from, their main assembly. If a user tries to open the door further after the door comes into contact with the tray, the tray is subjected to a substantial amount of load by the door. 
     That is, conventionally structured image forming apparatuses are problematic in that it is possible that their recording medium feeding-conveying tray will be damaged, and therefore, be reduced in recording medium feeding-conveying performance. Moreover, as an image forming apparatus is reduced in size, it is reduced in the distance between a process cartridge, which functions as an image formation unit, and a recording medium feeding-conveying tray. Thus, it becomes necessary to structure an image forming apparatus so that its door can be opened wider, and/or the rotational axis of the hinge portion of the door is placed closer to the tray, than in the case of an image forming apparatus of a larger size. As an image forming apparatus is structured so that its door can be opened wider, and/or the rotational axis of the door is placed closer to the tray, it is more likely for the door and tray to interfere with each other. 
     SUMMARY OF THE INVENTION 
     The present invention is for solving the above described problem, and its primary object is to provide an image forming apparatus which is significantly smaller in the amount of the load to which a component, or components, other than its door for installing or uninstalling an image formation unit (cassette), is subjected as the door comes into contact into the other components, than any conventional image forming apparatus. 
     According to an aspect of the present invention, there is provided an image forming apparatus comprising a main assembly; a rotatable member supported by said main assembly rotatably about a first rotational center; an openable member supported by said rotatable member rotatably about a second rotational center; and an urging member provided between said openable member and said rotatable member and configured to apply an urging force for suppressing opening of the openable member, wherein said openable member is capable of switching a rotational center between the first rotational center and the second rotational center in opening and closing operation of said openable member. 
     According to another aspect of the present invention, there is provided an image forming apparatus comprising a main assembly; an openable member openable and closable relative to said main assembly; a rotatable member configured to rotate said openable member relative to said main assembly; a hole portion which is provided in said main assembly and through which a rotational shaft portion of said rotatable member is slidably inserted; and an urging member provided between said main assembly and said rotatable member and configured to apply an urging force for suppressing opening of the openable member, wherein the rotation of said openable member is switched in response to an urging force of said urging member between rotation about said rotational shaft portion without movement along said hole portion and rotation about said rotational shaft portion with movement along said hole portion. 
     Further features of the present invention 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 sectional view of the image forming apparatus in the first embodiment of the present invention, and shows the general structure of the apparatus. 
       Part (a) of  FIG. 2  is a perspective view of the image forming apparatus in the first embodiment when the door of the apparatus, which is for installing or uninstalling the process cartridges, is closed, and the recording medium feeding-conveying tray of the apparatus is completely inside the main assembly of the apparatus. Part (b) of  FIG. 2  is a perspective view of the image forming apparatus in the first embodiment when the recording medium feeding-conveying tray of the apparatus is completely inside the main assembly of the apparatus, and the door of the apparatus, which is for the installation or uninstallation of the process cartridges, is open for allowing process cartridges to be installed into, or uninstalled from, the main assembly of the apparatus. Part (c) of  FIG. 2  is a perspective view of the image forming apparatus in the first embodiment, when the door of the apparatus, which is for the installation or uninstallation of process cartridges is closed, and the recording medium feeding-conveying tray of the apparatus is not completely inside the main assembly of the apparatus. 
         FIG. 3  is a schematic perspective view of the image forming apparatus in the first embodiment, when the door of the apparatus, which is for installing or uninstalling process cartridges is open while the recording medium feeding-conveying tray of the apparatus is not completely inside the main assembly of the apparatus. 
       Part (a) of  FIG. 4  is a perspective view of the door assembly of the image forming apparatus in the first embodiment, which is for describing the rotational movement of the roughly semicircular arm, door, etc., of the door assembly, which occurs when the door does not come into contact with the recording medium feeding-conveying tray of the apparatus. Part (b) of  FIG. 4  is a perspective view of the door assembly of the image forming apparatus in the first embodiment, which is for describing the rotational movement of the roughly semicircular arm, door, etc., of the door assembly, which occurs when the door comes into contact with the recording medium feeding-conveying tray of the apparatus. 
       Part (a) of  FIG. 5  is a perspective view of the door assembly of the image forming apparatus in the second embodiment, which is for describing the rotational movement of the roughly semicircular arm, door, etc., of the door assembly, which occurs when the door does not come into contact with the recording medium feeding-conveying tray of the apparatus. Part (b) of  FIG. 5  is an enlarged perspective view of the pressure applying means, and its adjacencies, of the image forming apparatus in the second embodiment, and shows the structure of the means. 
       Part (a) of  FIG. 6  is a perspective view of the door assembly of the image forming apparatus in the second embodiment  444 , which is for describing the rotational movement of the roughly semicircular arm, door, etc., of the door assembly, which occurs when the door comes into contact with the recording medium feeding-conveying tray of the apparatus. Part (b) of  FIG. 6  is an enlarged perspective view of the pressure applying means, and its adjacencies, of the image forming apparatus in the second embodiment, and shows the structure of the means. 
         FIG. 7  is a perspective view of the image forming apparatus in the third embodiment of the present invention when the door of the apparatus is opened while the recording medium feeding-conveying tray is not completely inside the main assembly of the apparatus. 
       Part (a) of  FIG. 8  is a perspective view of the door assembly of the image forming apparatus in the third embodiment, which is for describing the rotational movement of the roughly semicircular arm, door, etc., of the door assembly, which occurs when the door does not comes into contact with the recording medium feeding-conveying tray of the apparatus. Part (b) of  FIG. 8  is a perspective view of the door assembly of the image forming apparatus in the third embodiment, which is for describing the rotational movement of the roughly semicircular arm, door, etc., of the door assembly, which occurs when the door comes into contact with the recording medium feeding-conveying tray of the apparatus. 
         FIG. 9  is a schematic sectional view of the comparative image forming apparatus when the door of the apparatus is opened while the recording medium feeding-conveying tray is not completely inside the main assembly of the apparatus. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, a few of the image forming apparatuses which are in accordance with the present invention are concretely described. By the way, the measurement, material, and shape of each of the structural components of each of the image forming apparatuses in the following embodiments, the positional relationship among the structural components, etc., are not intended to limit the present invention in scope. 
     [Embodiment 1] 
     To begin with, referring to  FIGS. 1-4 , the image forming apparatus in the first embodiment of the present invention is described about its structure. The image forming apparatus  301  shown in  FIGS. 1-3  is an example of color laser printer which uses an electrophotographic image forming method. 
     &lt;Image Forming Apparatus&gt; 
       FIG. 1  is a sectional view of the image forming apparatus  301 , and shows the structure of the apparatus. In  FIG. 1 , a referential code  302  stands for one of the process cartridges which are removably installable in the main assembly of the image forming apparatus  301  in  FIGS. 1-3 . A referential code  330  stands for a door  330  which is pivotally hinged to the main assembly of the image forming apparatus  301  so that it can be opened to allow the process cartridges  302  to be installed into, or uninstalled from, the main assembly. 
     Each process cartridge  302  contains a photosensitive drum  302   a  which functions as an image bearing member. Each process cartridge  302  contains: a charge roller  302   b  which functions as a charging means for uniformly charging the peripheral surface of the photosensitive drum  302   a;  a laser scanner  303  which functions as an exposing means which projects a beam  303   a  of laser light upon the uniformly charged peripheral surface of the photosensitive drum  302   a  while modulating the beam  303   a  according to the information of the image to be formed; and a development roller  302   c , as a developer bearing member, which functions as a developing means for developing an electrostatic latent image formed on the peripheral surface of the photosensitive drum  302   a  by the beam  303   a  of laser light projected from the laser scanner  303 , into a toner image by supplying the electrostatic latent image with toner (developer). The charge roller  302   b , laser scanner  303 , and development roller  302   c  are disposed in the adjacencies of the peripheral surface of the photosensitive drum  302   a.    
     The electrostatic latent image formed on the peripheral surface of the photosensitive drum  302   a  by the beam  303   a  of laser light projected from the laser scanner  303  while being modulated according to the information of the image to be formed is developed into a toner image, on the peripheral surface of the photosensitive drum  302   a , by the toner supplied to the electrostatic latent image through one of the known image formation processes. An ordinary color laser printer employs four process cartridges  303  which form yellow, magenta, cyan and black toner images, one for one. 
     The image forming apparatus  301  is provided with an intermediary transfer belt  304 , which is suspended and kept tensioned by a pair of rollers  304   a  and  304   b , being enabled to be circularly moved, on the top side of the four photosensitive drums  302   a.  Further, the image forming apparatus  301  is provided with four primary transfer rollers  305  which function as primary transferring means. The four primary transfer rollers  305  are disposed on the inward side of the loop which the intermediary transfer belt  304  forms, in such a manner that they oppose the corresponding photosensitive drums  302   a . As primary transfer bias voltage is applied to the primary transfer roller  305 , the toner formed on the peripheral surface of the corresponding photosensitive drum  302   a  is transferred onto the outward surface of the intermediary transfer belt  304 . That is, four toner images, different in color, are sequentially transferred onto the outward surface of the intermediary transfer belt  304 , effecting thereby a multicolor image on the outward surface of the intermediary transfer belt  304 . 
     Further, the image forming apparatus  301  in  FIG. 1  is provided with a recording medium feeding-conveying tray  307  in which multiple sheets  306  of recording medium are storable. The recording medium feeding-conveying tray  307 , which hereafter will be referred to simply as a sheet feeding tray  307 , is removably installable in the main assembly of the image forming apparatus  301 . As a sheet feeder roller  308  disposed in the adjacencies of the leading edge (right end in  FIG. 1 ) of the sheets  306  of recording medium in the sheet feeder tray  307  in  FIG. 1  is rotated, one or more of the sheets  306  are moved out of the tray  307 , and then, are moved one by one into the main assembly of the image forming apparatus  301 , by the coordination between the sheet feeder roller  308  and an unshown separating means. Thereafter, each sheet  306  is conveyed further downstream by a pair of registration rollers  309  with a preset timing. 
     Further, the image forming apparatus  301  is provided with a secondary transfer roller  310  which functions as the secondary transferring means. The secondary transfer roller  310  is disposed so that it opposes the intermediary transfer belt  304 . Each sheet  306  of recording medium is conveyed by the pair of registration rollers  309  with such a timing that the sheet  306  arrives at the secondary transfer nip at the same time as the toner images on the outward surface of the intermediary transfer belt  304 . Then, as the secondary transfer bias voltage is applied to the secondary transfer roller  310 , the toner image on the outward surface of the intermediary transfer belt  304  is transferred onto the sheet  306 . 
     After an unfixed toner image was formed on the outward surface of the intermediary transfer belt  304 , and was transferred onto the sheet  306  of recording medium, the sheet  306  is conveyed further downstream, and then is subjected to heat and pressure by a fixing device  312  which functions as a fixing means. Thus, the toner (toner image) is melted. Then, as the melted toner cools down, it becomes fixed to the sheet  306 . Thereafter, the sheet  306  is discharged onto a delivery tray  320 . That is, an image is formed on the surface of the sheet  306  through an image forming operation comprising the above described sequential steps. 
     Parts (a)-(c) of  FIG. 2  are schematic perspective views of the image forming apparatus  301 , when the door  330  is closed and the sheet feeder tray  307  is completely inside the main assembly of the apparatus, when the door  330  is open wide enough for the process cartridges  302  to be installed into, or uninstalled, from the main assembly of the image forming apparatus  301 , when the sheet feeder tray  307  is not completely inside the main assembly, and when the door  330  is closed, and the sheet feeder tray  307  is not completely inside the main assembly of the apparatus, respectively. More concretely, part (a) of  FIG. 2  shows the image forming apparatus  301  when the door  330  is closed, and the sheet feeder tray  307  is entirely in the main assembly of the image forming apparatus  301 . Referring to part (b) of  FIG. 2 , the door  330  can be pivotally moved away from (opened), or pivotally moved toward (closed), the main assembly of the image forming apparatus  301 . The door  330  is opened wider than it needs to be opened to provide a space which is large enough for the process cartridges  302  to be replaced, that is, to be installed into, or uninstalled from, the main assembly. That is, the image forming apparatus  301  is structured so that the door  330  can be opened wide enough to intrude into the path of the sheet feeder tray  307 . 
     Referring to part (c) of  FIG. 2 , the image forming apparatus  301  is structured so that the sheet feeder tray  307  in which sheets  306  are stored can be installed into, or uninstalled from (toward, or away from, user in part (c) of  FIG. 2 ), the main assembly of the image forming apparatus  301 , in the horizontal direction, that is, the direction which is roughly perpendicular to the direction (vertical direction in  FIG. 1 ) in which the sheet  306  is conveyed through a recording medium conveyance passage  1  shown in  FIG. 1 . 
     &lt;Hinge Portion of Door&gt; 
     Next, referring to  FIGS. 3, 4 ( a ) and  4 ( b ), the structure of the hinge portion  2  of the door  330  in this embodiment is described. Referring to  FIGS. 3, 4 ( a ) and  4 ( b ), a door supporting section  340  is fixed to the main assembly of the image forming apparatus  301 . It is provided with a through hole  340   a  which is shaped in such a manner that its cross section which is perpendicular to the front surface of the door  330  has such a curvature that is equal to the curvature of a circle which has a preset radius, and, the center of which coincides with the first axis D 1  of rotation, shown in part (a) of  FIG. 4 . 
     The door  330  is provided with a pair of arms  341 , each of which is put through the through hole  340   a  of the supporting section  340 . The arm  341  is roughly semicircular. More specifically, its cross section perpendicular to the direction in which the door  330  is opened or closed is rectangular, and its vertical cross section parallel to the direction of the door movement has such a curvature that is equal to the curvature of the above described circle which has the preset radius, and, the center of which coincides with the first axis D 1  of rotation, shown in part (a) of  FIG. 4 . Thus, as the door  330  is opened or closed, the semicircular arm  341  can slide through the through hole  340   a . With the supporting section  340  and arm  341  being structured as described above, the door  330  is supported by the supporting section  340  and arms  341  in such a manner that it is allowed to pivotally move relative to the main assembly of the image forming apparatus  301 , about a hypothetical axis AX 1  which coincides with the first axis D 1  of rotation shown in part (a) of  FIG. 4 . 
     The arm  341  is provided with a pair of rotation stoppers  341   a  and  341   b , which protrude from the lengthwise ends of the arm  341 , one for one. As the door  330  is pivotally moved (opened), the rotation stopper  341   a  comes into contact with the bottom surface of the supporting section  340 , more specifically, the portion of the bottom surface of the supporting section  340 , which is next to the through hole  340   a , controlling thereby the arm  341  in the angle of its rotational movement. The opposite end of the arm  341  from the rotation stopper  341   a  is provided with a shaft  342 , which protrudes from the arm  341 , inward of the main assembly of the image forming apparatus  301 . This shaft  342  is put through an unshown through hole, with which one end of a door anchoring section (bracket)  343  which is L-shaped in cross section, is provided. Thus, the door anchoring section (bracket)  343  is rotatable about the shaft  342 , more specifically, the axis (second axis D 2  of rotation) of the shaft  342 . That is, it is the door anchoring section (bracket)  343  to which the door  330  is fixed. In other words, the door  330  is supported by the shaft  342 , which is protrusive from the arm  341 , in such a manner that the door  330  is rotatable about the second axis D 2  of rotation. In part (b) of  FIG. 4 , the hypothetical axis of rotation which coincides with the second axis D 2 , that is, a hypothetical axis of rotation, is designated by a referential code AX 2 . 
     Regarding the movement of the door  330 , as the arm  341  supported by the supporting section  340  rotationally moves about the first axis D 1  of rotation, following the first locus R 1 , the door  330  rotationally moves with the arm  341 , about the first axis D 1  of rotation shown in part (a) of  FIG. 4 . 
     Further, the door  330  rotationally moves with the arm  341 , following the first locus shown in part (a) of  FIG. 4 . In order to prevent the arm  341  from disengaging from the through hole  340   a  of the supporting section  340  while the door  330  rotationally moves, one of the lengthwise ends of the arm  341  is provided with the stopper  341   a . Further, the other end of the arm  341  is provided with the shaft  342 , which perpendicularly protrudes inward from the arm  341 . Therefore, it is possible for the door  330  to rotationally move about the shaft  342  (second axis D 2  of rotation), following the second locus R 2 . 
     The shaft  342  with which the arm  341  is provided is fitted with a torsional coil spring  344  which functions as a pressure applying member. That is, the torsional coil spring  344  is supported by the shaft  342 . One end  344   a  of the torsional coil spring  344  is engaged with the arm  341 , and the other end  344   b  of the torsional coil spring  344  is engaged with the door anchoring section (bracket)  343 . Thus, the door  330  always remains under the pressure generated by the resiliency of the torsional coil spring  344 , in the opposite direction (in which door  330  is closed) from the direction indicated by an arrow mark R 2 , which also designates the second locus. That is, the door  330  always remains under the pressure generated by the torsional coil spring  344  in the direction to rotate the door  330  about the second locus R 2  in the closing direction. The torsional coil spring  344  which functions as a pressure applying member is fitted between the door anchoring section (bracket)  343  and arm  341 , and always keeps the door  330  under such pressure that works in the direction to prevent the door  330  from opening. 
     The door attachment bracket  343  to which the door  330  is attached remains pressured by the torsional coil spring  344  in the direction to prevent the door  330  from opening. That is, the door  330  remains pressured by the torsional coil spring  344  disposed between the arm  341  and door attachment bracket  343 , in the direction to prevent the door  330  from opening. Therefore, unless the door  330  is subjected to such force (moment) that is greater than the pressure generated by the resiliency (moment) of the torsional coil spring  344 , the torsional coil spring  344  prevents the door  330  from rotating in a manner to follow the second locus R 2  shown in part (b) of  FIG. 4 . 
     Further, the door attachment bracket  343  fitted around the shaft  342  of the arm  341  in such a manner that it is allowed to rotate about the shaft  342  is regulated in the angle of its rotation by the rotation stopper  341   b , with which the opposite end of the arm  341  from the door attachment bracket  343  is provided. That is, as the door attachment bracket  343  comes into contact with the rotation stopper  341   b , it is prevented from rotating further in the opening direction. In other words, the rotation stopper  341   b  regulates the door attachment bracket  343  in the angle of its rotational movement. 
     Referring to part (b) of  FIG. 2 , in this embodiment, when the door  330  is opened while the sheet feeder tray  307  is completely inside the main assembly of the image forming apparatus  301 , the door  330  always rotates following the first locus R 1  shown in part (a) of  FIG. 4 . 
     However, it sometimes occurs that the door  330  is opened while the sheet feeder tray  307  is not completely inside the main assembly of the image forming apparatus  301 , as shown in  FIG. 3 . In such a case, the door  330  rotates about the first axis D 1  of rotation, shown in part (a) of  FIG. 4 , following the first locus R 1 , until the door  330  comes into contact with the sheet feeder tray  307 . 
     If a user tries to further open the door  330  against the resiliency of the torsional coil spring  344  after the door  330  come into contact with the sheet feeder tray  307 , the door  330  is subjected to a load, the amount of which equals to the force applied by the user to further open the door. Consequently, the door  330  is made to rotate about the second axis D 2  of rotation, shown in part (b) of  FIG. 4 , following the second locus R 2 . 
     In this embodiment, the rotational axis of the door  330  switches between the first axis D 1  of rotation and the second axis D 2  of rotation based on the difference between the amount of the resiliency of the torsional coil spring  344  and the amount of force applied to the door  330  by the user. That is, as long as the door  330  does not come into contact with the sheet feeder tray  307  while it is opened, the amount of force to which the torsional coil spring  344  is subjected is smaller than the amount of the force generated by the resiliency of the torsional coil spring  344 . In such a case, the arm  341  rotates about the first axis D 1  of rotation, shown in part (a) of  FIG. 4 , following the first locus R 1 , and so does the door  330 . 
     On the other hand, in a case where the door  330  comes into contact with the sheet feeder tray  307  while the door  330  is opened or closed, the torsional coil spring  344  is subjected to such an amount of force that is greater than the amount of force generated by the resiliency of the torsional coil spring  344 . Thus, the door  330  rotates about the second axis D 2  of rotation, shown in part (b) of  FIG. 4 , following the second locus R 2 . 
       FIG. 9  is a drawing illustrating a comparative image forming apparatus  301 . If a user opens the door  330  while the sheet feeder tray  307  is not completely inside the main assembly of the image forming apparatus  301 , it sometimes occurs that the door  330  comes into contact with the sheet feeder tray  307 . If the user tries to further open the door  330  after the door  330  comes into contact with the sheet feeder tray  307 , the force applied to the door  330  by the user is applied to the sheet feeder tray  307  through the door  330 . In the case of the comparative image forming apparatus  301  shown in  FIG. 9 , the impactive force generated by the abrupt contact between the door  330  and sheet feeder tray  307  is entirely transmitted to the sheet feeder tray  307 . Thus, the sheet feeder tray  307  is subjected to a large amount of force. 
     In comparison, in the case of the image forming apparatus  301  in this embodiment, until the door  330  comes into contact with the sheet feeder tray  307 , the door  330  rotates with the arm  341  about the first axis D 1  of rotation, following the first locus R 1 , as shown in part (a) of  FIG. 4 , as in the case of the comparative image forming apparatus  301 . 
     Then, as such an amount of force that is greater than the force generated by the resiliency of the torsional coil spring  344  is applied to the door  330  against the resiliency of the torsional coil spring  344 , the door  330  rotates about the second axis D 2  of rotation, following the second locus R 2 , as shown in part (b) of  FIG. 4 . Thus, the impact which occurs as the door  330  comes into contact with the sheet feeder tray  307  is reduced. Therefore, the force to which the sheet feeder tray  307  is subjected as the door  330  comes into contact with the sheet feeder tray  307  while the door  330  is opened is significantly smaller than in the case of the comparative image forming apparatus  301 . 
     According to this embodiment, as the door  330  comes into contact with the sheet feeder tray  307  while the door  330  is opened or closed, the rotational axis of the door  330  shifts from the first axis D 1  of rotation, shown in part (a) of  FIG. 4 , to the second axis D 2  of rotation shown in part (b) of  FIG. 4 . Thus, it does not occur that the force applied to the door  330  to open the door  330  is entirely transmitted to the sheet feeder tray  307 . Therefore, the load to which the sheet feeder tray  307  is subjected is significantly smaller than in the case of the comparative image forming apparatus  301  (any conventional image forming apparatus). 
     [Embodiment 2] 
     Next, referring to  FIGS. 5 and 6 , the image forming apparatus  301  in the second embodiment of the present invention is described about its structure. The components of the image forming apparatus  301  in this embodiment, which are the same in structure as the counterparts in the first embodiment are given the same referential codes as the counterparts, and are not described here. Further, even if a component of the image forming apparatus  301  in this embodiment is different in referential code from the counterpart in the first embodiment, it is not described as long as the two components are the same in structure. 
     In the first embodiment, the torsional coil spring  344  which functions as a pressure applying member is fitted around the shaft  342 . Further, one end  344   a  of the torsional coil spring  344  is anchored to the rotational arm  341 , and the other end  344  is anchored to the door attachment bracket  343 . In other words, the image forming apparatus  301  in the first embodiment was structured so that the pressure generated by the resiliency of the torsional coil spring  344  is applied in the direction to prevent the door  330  from opening. 
     Referring to part (b) of  FIG. 5 , in this embodiment, a torsional coil spring  444  is fitted around the shaft  342 . One end  444   a  of the torsional coil spring  444  is anchored to the shaft  342  by being inserted into a groove  342   a  with which the shaft  342  is provided, and the other end  344   b  is anchored to the door attachment bracket  343 . Thus, the force generated by the resiliency of the torsional coil spring  444  is made to work in the direction to prevent the door  330  from opening. Otherwise, the image forming apparatus  301  in this embodiment is the same in structure as that in the first embodiment. Thus, this embodiment can provide the same effects as the first embodiment. 
     [Embodiment 3] 
     Next, referring to  FIGS. 7 and 8 , the image forming apparatus in the third embodiment of the present invention is described about its structure. By the way, the components of the image forming apparatus  301  in this embodiment, which are the same in structure as the counterparts in each of the preceding embodiments are given the same referential codes as the counterparts, and are not described here. Further, even if a component of the image forming apparatus  301  in this embodiment is different in referential code from the counterpart in the first embodiment, it is not described as long as the two components are the same in structure. 
     Referring to  FIGS. 7 and 8 , a supporting section (bracket)  540  which is solidly attached to the main assembly of the image forming apparatus  301  is provided with a through hole  540   a  which extends in the vertical direction of part (a) of  FIG. 8  and part (b) of  FIG. 8 . The arm  541  to which the door  330  is attached so that the door  330  can be pivotally moved (opened or closed) relative to the main assembly of the image forming apparatus  301  is provided with a shaft  541   a , which horizontally protrudes from one end of the arm  541 , and which is put through the above described through hole  540   a  in such a manner that it is allowed to vertically move though the hole  540   a.    
     It is to the other end of the arm  541  that the door  330  is solidly attached by a door bracket section  541   b  of the arm  541 . Thus, the door  330  is supported by the arm  540  in such a manner that it is rotationally movable about the axis D 3  of the shaft  541   a , as shown in part (a) of  FIG. 8 , following the first locus R 3 , shown in part (a) of  FIG. 8 . 
     Further, the image forming apparatus  301  is structured so that the shaft  541   a  with which the arm  541  is provided is allowed to move in the direction indicated by an arrow mark E in part (b) of  FIG. 8 , following the through hole  540   a . Moreover, there is disposed a coil spring  544  which functions as a pressure applying means, between one end (top end in part (a) of  FIGS. 8 and 8 ( b ) of the elongated hole  540   a , and the peripheral surface of the shaft  541   a.    
     Thus, the shaft  541   a  always remains pressured by the resiliency of the coil spring  544  in the opposite direction from the direction indicated by the arrow mark E in part (b) of  FIG. 8 . Thus, unless a force which is greater than the expansionary resiliency of the coil spring  544  acts on the door  330 , the coil spring  544  prevents the shaft  541   a  from moving in the direction indicated by the arrow mark E in part (a) of  FIG. 8 . That is, such a force that acts in a manner to regulate the opening of the door  330  is applied to the door  330  by the coil spring  544  disposed between the supporting section  540  with which the main assembly of the image forming apparatus  301  is provided, and the arm  541 . Thus, as the door  330  is rotationally (pivotally) moved, the shaft  541   a  moves through the elongated through hole  540   a , remaining under the pressure generated by the resiliency of the coil spring  544 . 
     Referring to  FIG. 7 , because the image forming apparatus  301  is structured as described above, it sometimes occurs that the door  330  is opened while the sheet feeder tray  307  is not completely inside the main assembly of the main assembly of the image forming apparatus  301 . In such a case, the door  330  rotationally (pivotally) moves about the axis D 3  of the shaft  541   a , following the first locus R 3 , shown in part (a) of  FIG. 8 , until the door  330  comes into contact the sheet feeder tray  307 . 
     If a user applies a certain amount of force to the door  330  to further open the door  330  while the door  330  is in contact with the sheet feeder tray  307 , the door  330  rotationally (pivotally) moves while causing the shaft  541   a  to move in the direction indicated by the arrow mark E in part (b) of  FIG. 8 , following the elongated through hole  540   a , against the force generated by the resiliency of the coil spring  544 . 
     That is, in a case where the door  330  does not come into contact with the sheet feeder tray  307  while the door  330  is opened or closed, the force which acts on the door  330  is smaller than the force generated by the resiliency of the coil spring  544 . Thus, the door  330  rotationally moves about the axis D 3 , without causing the shaft  541   a , which is under the pressure generated by the coil spring  544 , to move following the elongated through hole  540   a.    
     On the other hand, in a case where the door  330  comes into contact with the sheet feeder tray  307  while it is opened or closed, such a force that is greater than the pressure generated by the expansionary resiliency of the coil spring  544  acts on the door  330 . Thus, the door  330  rotates while causing the shaft  541   a  to move in the direction indicated by the arrow mark E in part (b) of  FIG. 8  along the elongated through hole  540   a , against the force generated by the expansionary resiliency of the coil spring  544 . 
     That is, the rotational movement of the door  330  against the force generated by the resiliency of the coil spring which functions as a pressure applying means is as follows. Until the door  330  comes into contact with the sheet feeder tray  307 , the shaft  541  does not moves along the elongated through hole  540   a,  and the door  330  rotates about the shaft  541  (pivots about axis of shaft  541 ). As the door  330  is opened further, the shaft  541   a  is moved upward along the elongated through hole  540   a , and the door  330  rotates about the axis of the upwardly moving shaft  541   a , as shown in part (b) of  FIG. 8 . 
     In the case of the comparative image forming apparatus  301  structured as shown in  FIG. 9 , the impact generated as the door  330  comes into contact with the sheet feeder tray  307  is entirely transmitted to the sheet feeder tray  307 . Thus, the sheet feeder tray  307  is subjected to a significant amount of force. In comparison, in this embodiment, as a user applies force (load) to the door  330  to further open the door  330  after the door  330  came into contact with the sheet feeder tray  307 , the shaft  541   a  moves in the direction indicated by the arrow mark E in part (b) of  FIG. 8  along the elongated through hole  540   a,  against the force generated by the resiliency of the coil spring  544 . 
     Therefore, in the case of the image forming apparatus  301  in this embodiment, the impact which occurs as the door  330  comes into contact with the sheet feeder tray  307  is not as large as that in the case of the comparative image forming apparatus  301 . Therefore, the force which applies to the sheet feeder tray  307  in the case of the image forming apparatus  301  in this embodiment is not as large as that in the case of the comparative image forming apparatus  301 . By the way, instead of the coil spring  544 , an elastic component, the resiliency of which acts in its lengthwise direction, may be disposed between the top wall of the elongated through hole  541   a  (top end in parts (a) and (b) of  FIG. 8 ), and the peripheral surface of the shaft  541   a . The effects of such a structural arrangement are the same as that of the image forming apparatus  301  in this embodiment. Otherwise, the structure of the image forming apparatus  301  in this embodiment is the same as that of the image forming apparatus  301  in each of the preceding embodiments. Further, the effects of this embodiment are the same as any of the preceding embodiments. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention 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. 2014-163549 filed on Aug. 11, 2014, which is hereby incorporated by reference herein in its entirety.