Abstract:
A medium ejection apparatus is provided which may be part of an image forming apparatus. The medium ejection apparatus may include an ejection roller configured to eject a recording medium and a pinch roller disposed opposite to the ejection roller. The pinch roller is configured to move toward and away from the ejection roller and to press a recording medium toward the ejection roller. Also, the medium ejection apparatus may include an elastic member configured to press the pinch roller toward the ejection roller and a lever disposed downstream of the pinch roller in a recording medium transport direction. The lever is configured to be moved between a first position and a second position. When the lever is in the second position, the lever contacts the pinch roller, which causes a force to be applied against the elastic member, and the pinch roller is spaced away from the ejection roller.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of prior U.S. application Ser. No. 12/392,356, filed Feb. 25, 2009, which claims priority from Japanese Patent Application No. 2008-044629, filed on Feb. 26, 2008, the entire subject matter of which is incorporated herein by reference. 
     
    
     FIELD 
       [0002]    Aspects of the invention relate to a medium ejection apparatus and an image forming apparatus having the medium ejection apparatus. 
       BACKGROUND 
       [0003]    A known image forming apparatus may include a lever in proximity to an ejection roller to ensure that each recording medium, e.g., a sheet of paper, on which an image has been formed, is stacked on an output tray. An upper end of the lever is attached to a main body of the image forming apparatus so that the lever is movable. The lever is configured to move downward under its gravity and to press a recording sheet having an image thereon ejected from the image forming apparatus downward or toward the output tray. 
         [0004]    As the lever is attached to the main body of the image forming apparatus in proximity to the ejection roller, it may be accidentally pressed down when a user takes a recording sheet placed on the output tray. Alternatively, when the user takes a stack of recording sheets from the output tray and then puts the stack back on the tray, the stack may hit the lever. The lever is susceptible to such a great force produced by a user or by contact with an object, and may separate from the main body of the image forming apparatus. 
       SUMMARY 
       [0005]    Illustrative aspects of the invention provide a medium ejection apparatus and an image forming apparatus including such a medium ejection apparatus configured to prevent a lever from separating from a main body of the image forming apparatus when the lever is subjected to a great force. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    Illustrative aspects will be described in detail with reference to the following figures in which like elements are labeled with like numbers and in which: 
           [0007]      FIG. 1  is a perspective view of an outer appearance of an illustrative example of an image forming apparatus using features described herein; 
           [0008]      FIG. 2  is a sectional view of the image forming apparatus of  FIG. 1 ; 
           [0009]      FIG. 3  is a perspective view of a top cover; 
           [0010]      FIG. 4  is a side view of the top cover; 
           [0011]      FIG. 5  is a top view showing a positional relationship between ejection rollers, pinch rollers, and levers when viewed from an arrow A of  FIG. 4 ; 
           [0012]      FIG. 6A  is an exploded top view of  FIG. 5 ; 
           [0013]      FIG. 6B  is a top view of the lever; and 
           [0014]      FIGS. 7A ,  7 B, and  7 C are sectional views taken along line A-A of  FIG. 5 , showing a series of operations of the lever responsive to an external force. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    An illustrative embodiment will be described in detail with reference to the accompanying drawings. An image forming apparatus  1  according to aspects of the invention applies to a monochrome laser printer. 
         [0016]    For ease of discussion, in the following description, the top or upper side, the bottom or lower side, the left or left side, the right or right side, the front or front side, and the rear or rear side are used to define the various parts when the image forming apparatus  1  is disposed in an orientation in which it is intended to be used, as shown in  FIG. 1 . 
         [0017]    As shown in  FIG. 1 , the image forming apparatus  1  may include a generally box-shaped main body  5 . A top surface of the main body  5  is a top cover  9  which includes an output tray  7 . The image forming apparatus  1  may further include an electrophotographic image forming unit  3  ( FIG. 2 ) that is configured to form an image on a recording medium, e.g., a sheet of plain paper and a transparency, (hereinafter referred to as a recording sheet) by transferring a developer image onto the recording sheet. A recording sheet on which an image has been formed at the image forming unit  3  is ejected and placed onto the output tray  7 . 
         [0018]    In this illustrative embodiment, the top cover  9  is detachably attached to the main body  5 . The main body  5  and the top cover  9  can be made of resin such as acrylonitrile butadiene styrene (ABS). 
         [0019]    The image forming unit  3  is accommodated in the main body  5  and includes, as is well known, a process cartridge  11 , a light exposing device  13 , and a fixing unit  15 . 
         [0020]    A sheet supply tray  17  may be disposed in a lower portion of the main body  5  and be configured to have a stack of sheets loaded therein. A feeder unit  19  is disposed at the front side of the sheet supply tray  17 . The feeder unit  19  includes a pick up roller  19 A, a separation roller  19 B, a separation pad  19 C, and a pair of registration rollers  19 D. A recording sheet is separated from the stack of recording sheets by the pickup roller  19 A, the separation roller  19 B, and the separation pad  19 C, and fed between the registration rollers  19 D to correct skew of the recording sheet, and is further fed to the process cartridge  11 . 
         [0021]    A developer image is transferred onto the recording sheet at the process cartridge  11 , and heated and fixed at the fixing unit  15 . The recording sheet, which is fed from the fixing unit  15 , changes its feeding direction upward about 180 degrees, and is ejected from an ejection portion  7 A, which opens to the output tray  7 . 
         [0022]    The process cartridge  11  includes a photosensitive drum  11 A on which the developer image is carried, and a charger  11 B configured to charge the photosensitive drum  11 A. The photosensitive drum  11 A is charged by the charger  11 B, and exposed to light by the light exposing device  13 , so that an electrostatic latent image can be formed on an outer surface of the photosensitive drum  11 A. When the photosensitive drum  11 A is supplied with developer, a developer image can be carried or formed on the outer surface of the photosensitive drum  11 A. 
         [0023]    As shown in  FIGS. 2-5 , ejection rollers  21 , pinch rollers  23 , and levers  25  are arranged in the ejection portion  7 A of the output tray  7 . 
         [0024]    The ejection rollers  21  are configured to rotate in contact with a recording sheet received from the image forming unit  3  and to eject the recording sheet to the output tray  7 . At least cylindrical portions of the ejection rollers  21  that contact the recording sheet are formed of an elastic material such as rubber. 
         [0025]    As shown in  FIG. 6A , a plurality of, e.g., four in this illustrative embodiment, ejection rollers  21  is disposed with each roller  21  in spaced relation to each other around a drive shaft  21 A extending in a widthwise direction of the ejection portion  7 A, i.e. in a right-left direction of the image forming apparatus  1 . The ejection rollers  21  are driven by the drive shaft  21 A that is rotatably attached to the top cover  9 . 
         [0026]    The pinch roller  23  is disposed facing a corresponding ejection roller  21  from below as shown in  FIG. 7A . The pinch rollers  23  are cylindrically shaped as shown in  FIG. 6A , and are configured to press the recording sheet toward the ejection rollers  21 . The pinch rollers  23  are movably attached to the top cover  9  such that they move toward and away from the corresponding ejection rollers  21 . 
         [0027]    Each pinch roller  23  is provided with support shaft portions  23 A ( FIG. 6A ), which are rotatably engaged in recessed portions in a pinch holder  23 B ( FIGS. 7A-7C ). 
         [0028]    The pinch holder  23 B is movably attached to the top cover  9  at an upstream side of a corresponding pinch roller  23  in a sheet ejection direction. The pinch holder  23 B is pressed toward the ejection roller  21  by an elastically deformable pressing member, e.g. a coiled spring  23 C. Thus, each pinch roller  23  can move toward or away from a corresponding ejection roller  21  and be normally pressed toward the corresponding ejection roller  21  by the coiled spring  23 C. 
         [0029]    As shown in  FIG. 6A , each pinch roller  23  further includes a cylindrical roller portion  23 D, and a flanged portion  23 E protruding outwardly from the entire perimeter of the roller portion  23 D. The roller portion  23 D and the flange portion  23 E are integrally formed of a resin material having a higher hardness than that for the ejection rollers  21 , for example, polyoxymethylene (POM). 
         [0030]    As shown in  FIG. 3 , the levers  25  extend toward the output tray  7  from the ejection portion  7 A. The levers  25  are formed of a resin material similar to the pinch roller  23  and are configured to press a recording sheet being ejected by the ejection rollers  21  downward. As shown in  FIG. 6B , each lever  25  includes shaft portions  25 A, a weight portion  25 B, and arm portions  25 C. As shown in  FIG. 7A , the shaft portion  25 A is disposed in an upper end of the lever  25 , and the shaft portion  25 A is attached to the top cover  9  so that the lever  25  is movable. 
         [0031]    As shown in  FIG. 6B , the weight portion  25 B extends in a direction parallel to an axial direction of the ejection rollers  21  (hereinafter referred to as a width direction), and is configured to contact the recording sheet being ejected by the ejection rollers  21  and press it downward. The arm portions  25 C extend from both ends of the weight portion  25 B toward the shaft portions  25 A. 
         [0032]    The shaft portions  25 A protrude toward the top cover  9 , and rotatably engage in recessed portions (not shown) of the top cover  9 , so as to movably support the lever  25 . When the lever  25  is attached to the top cover  9 , the arm portions  25 C are elastically deformed so that they move toward each other, and the shaft portions  25 A are inserted into the recessed portions of the top cover  9 . 
         [0033]    The lever  25  further includes a tongue portion  25 D between the arm portions  25 C. The tongue portion  25 D is provided with a contact portion  25 E at an end. As shown in  FIG. 7A , the contact portion  25 E contacts a contacted portion  9 A of the top cover  9  when there is no external force applied to the lever  25 . 
         [0034]    The lever  25  would rotate so that the weight portion  25 B moves toward the pinch roller  23  under its weight. However, when external force is not applied to the lever  25 , the contact portion  25 E contacts the contacted portion  9 A, and the lever  25  is prevented from contacting the pinch roller  23 . In this illustrative embodiment, the contact portion  25 E and the contacted portion  9 A restrict the movement of the lever  25  such that the lever  25  is prevented from making contact with the pinch roller  23 . 
         [0035]    The contact portion  25 E includes an elastic member  25 F in an area where the contact portion  25 E contacts the contacted portion  9 A. The elastic member  25 F is formed of an elastically deformable material such as rubber. The elastic member  25 F is configured to absorb noise produced when the contact portion  25 E contacts or hits the contacted area  9 A. 
         [0036]    As shown in  FIG. 7B , when the lever  25  receives external force and is moved downward, it contacts the flange portion  23 E of the pinch roller  23  ahead of the ejection roller  21 . 
         [0037]    As shown in  FIG. 6A , the levers  25  are disposed at positions corresponding to two ejection rollers  21  positioned outermost of the four ejection rollers  21  attached around the drive shaft  21 A. Positions and dimensions of the ejection rollers  21 , the pinch rollers  23  and the levers  25  are set to obtain the following positional relationship: 
         [0038]    In  FIG. 6A , S 1  represents an imaginary plane that is orthogonal to a sheet ejection direction where a recording sheet is ejected by the ejection rollers  21 . When the ejection roller  21 , the pinch roller  23  and the shaft portion  25 A of the lever  25  are projected to the imaginary plane S 1  in the sheet ejection direction, a projected image of the shaft portion  25 A overlaps at least one of projected images of the ejection roller  21  and the pinch roller  23  on the imaginary plane S 1 . In this illustrative embodiment, as shown in  FIG. 7A , the projected image of the shaft portion  25 A overlaps that of the ejection roller  21  on the imaginary plane S 1 . 
         [0039]    Specifically, as shown in  FIG. 6A , the ejection roller  21 , the pinch roller  23 , and the lever  25  are arranged in line along the sheet ejection direction. 
         [0040]    When there is no external force being applied to the lever  25  as shown in  FIG. 7A , the pinch roller  23  contacts the ejection roller  21  by a pressing force of the coiled spring  23 C, the contact portion  25 E contacts the contacted portion  9 A, and the lever  25  is spaced away from the pinch roller  23 . 
         [0041]    In a state where the lever  25  is away from the pinch roller  23 , when a recording sheet having the image thereon caught between the ejection roller  21  and the pinch roller  23  is ejected to the output tray  7 , the trailing end of the recording sheet is held by the lever  25 . 
         [0042]    The levers  25  are exposed outside at the output tray  7  because they have a function to hold recording sheets to be ejected to the output tray  7 . Thus, there is a high possibility that the user will touch or press the levers  25 , causing the levers  25  to be subjected to great downward force. 
         [0043]    The output tray  7  receives a recording sheet on which an image has been formed. If the image forming apparatus  1  is employed among a plurality of processors or users and there are recording sheets having images stacked on the output tray  7 , a user takes his or her recording sheet(s) from the stack and puts the remaining sheets back on the output tray  7 . In this case, the stack of recording sheets may contact the levers  25 , and the levers  25  may be subjected to great downward force according to the weight of the stack of recording sheets. 
         [0044]    As shown in  FIG. 7B , when a downward external force F acts on the lever  25 , the lever  25  is moved toward the pinch roller  23 , and contacts the flange portion  23 E of the pinch roller  23 . 
         [0045]    When the external force F is great, the lever  25  itself elastically deforms, and contacts the pinch roller  23  and the ejection roller  21  as shown in  FIG. 7C . 
         [0046]    In this illustrative embodiment, the ejection rollers  21 , the pinch rollers  23 , and the levers  25  are configured such that, when the lever  25  is moved downward by external force, it contacts the pinch roller  23  ahead of the ejection roller  21  as shown in  FIGS. 7A and 7B . 
         [0047]    With this configuration, when the external force F acts on the lever  25 , the lever  25  contacts the pinch roller  23  and the external force F is absorbed by the elastic deformation of the coiled spring  23 C that presses the pinch roller  23 . Thus, the lever  25  can be prevented from being separated from the top cover  9 , which is part of the main body of the image forming apparatus  1 . 
         [0048]    In this illustrative embodiment, the pinch rollers  23  and the levers  25  are formed of material having a hardness greater than that of the ejection rollers  21 . Thus, the pinch roller  23  can be prevented from getting damaged when the lever  25  contacts the pinch roller  23 . In addition, the ejection roller  21 , which has a lower hardness, can be prevented from getting damaged because it does not need to structurally absorb the external force acting on the lever  25 . 
         [0049]    In this illustrative embodiment, when the lever  25  is moved downward by the external force, it contacts the flange portion  23 E of the pinch roller  23  without contacting the roller portion  23 D. Thus, when the external force F acts on the lever  25 , the roller portion  23 D can be prevented from getting damaged. 
         [0050]    When the external force does not act on the lever  25 , the lever  25  does not contact the pinch roller  23 . Thus, in normal times when the external force F is not applied, the lever  25  is positioned away from the pinch roller  23 . 
         [0051]    Thus, noise produced by contact between the pinch roller  23  and the lever  25  can be prevented and the pinch roller  23  can be prevented from getting damaged. 
         [0052]    In addition, as the contact portion  25 E includes the elastic portion  25 F, it can absorb noise produced when the contact portion  25 E contacts the contacted portion  9 A and the lever  25  can be prevented from getting damaged. The elastic portion  25 E may be disposed on the contacted portion  9 A. 
         [0053]    In this illustrative embodiment, the shaft portion  25 A projected to the imaginary plane S 1  overlaps the ejection roller  21  projected to the imaginary plane S 1  on the imaginary plane S 1 . Thus, a force acting on the lever  25  or the shaft portion  25 A can be received at the ejection roller  21 , and the shaft portion  25 A can be prevented from being separated from the top cover  9 . 
         [0054]    Even if the external force F acting on the lever  25  is not excessively great, the lever  25  contacts the pinch roller  23  and the external force F is absorbed by the coil spring  23 C as described above. Thus, the lever  25  is not likely to sustain damage. However, if a strong external force is exerted on the lever  25 , it can not be fully absorbed only by the coil spring  23 C, and the lever  25  may get damaged. 
         [0055]    In this illustrative embodiment, however, when the strong external force is applied to the lever  25 , the lever  25  contacts the ejection roller  21  and the pinch roller  23 , so that the coil spring  23 C and the ejection roller  21  absorb the external force. Thus, the lever  25  can be prevented from getting damaged even if the strong external force is applied to the lever  25 . 
         [0056]    The above illustrative embodiment shows, but is not limited to, a monochrome laser printer. It will be appreciated that this illustrative embodiment also applies to other types of image forming apparatuses, a color laser printer, an inkjet printer, and a facsimile machine as well. 
         [0057]    The above illustrative embodiment shows, but is not limited to, the exposing device using laser beams to irradiate the photosensitive drum  11 A. An exposing device using a number of LEDs to irradiate the photosensitive drum  11   a  may be applied. 
         [0058]    While the features herein have been described in connection with various example structures and illustrative aspects, it will be understood by those skilled in the art that other variations and modifications of the structures and aspects described above may be made without departing from the scope of the inventions described herein. Other structures and aspects will be apparent to those skilled in the art from a consideration of the specification or practice of the features disclosed herein. It is intended that the specification and the described examples only are illustrative with the true scope of the inventions being defined by the following claims.