Patent Publication Number: US-7722031-B2

Title: Image forming apparatus including a sheet feed cassette capable of effectively transporting a sheet recording medium

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This patent specification is based on and claims priority under 35 U.S.C. §119 from Japanese patent application No. JP2006-038139, filed on Feb. 15, 2006, in the Japan Patent Office, the entire contents of which are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   Exemplary aspects of the present invention generally relate to a sheet feed cassette and an image forming apparatus including the same, and more particularly to a sheet feed cassette capable of effectively transporting a sheet recording medium, and an image forming apparatus including the same. 
   2. Discussion of the Background 
   Image forming apparatuses such as a copier, a printer, a facsimile, a multi-functional printer and so forth are equipped with a sheet feed cassette (a sheet feed cassette as used herein includes a sheet feed tray and a cassette does not require removability from the image forming apparatus, although this may be possible). The sheet feed cassette is attachable and detachable relative to the image forming apparatus and stores paper. Paper, as used herein, includes a sheet, transfer member, printable media and the like. Typically, but not necessarily, paper is the medium of the sheet on which an image is to be formed. It should be understood, however, that the sheets, etc., are not limited only to paper. 
   In the image forming apparatus, i.e., a multi-functional copier, sheet feed rollers or the like separate the stored paper one sheet at a time and transport the sheets to an image forming portion. In the image forming portion, a toner image is transferred on the paper. The paper carrying the toner image is transported to a fixing unit so that the toner image is fixed. Ultimately, the paper is ejected to a catch tray. The sheet feed cassette includes side frames which regulate the alignment of the paper in a width direction perpendicular to a sheet conveyance direction. The cassette further includes an end frame which regulates the paper in a front-rear direction of the sheet conveyance direction, and a bottom plate urged in an upward direction by a biasing mechanism. 
   In such image forming apparatuses, a release coated paper which contains an adhesive material may be used. When such a paper is transported, the adhesive material may leak out of an end portion of the paper or a cut, and may stick to the sheet conveyance path and a storage surface of the sheet feed cassette. Along with the sheet transporting operation, the adhesive material continues to stick causing the sheet conveyance path to become contaminated with adhesive. Consequently, problems such as an interruption during transportation of the paper, paper jams and skew may occur. 
   When the adhesive material sticks to the side frames and/or the end frame of the sheet feed cassette which may be in close contact with the paper, the paper may be adhered to the side frames and/or the end frame generating the similar problems described above, because the end portion of the paper is pressed. Similar problems described above may be generated in a case where the adhesive material sticks to the bottom plate of the sheet feed cassette. In this case, since the laden weight of the paper is applied on the bottom plate, the paper may easily adhere to the bottom plate. 
   SUMMARY OF THE INVENTION 
   In view of the foregoing, exemplary embodiments of the present invention provide an image forming apparatus having a sheet feed cassette that includes a protective sheet provided on or around the frame so as to prevent an adhesive material from sticking thereto. 
   In one exemplary embodiment of the above-mentioned sheet feed cassette, the protective sheet may be attachably and detachably provided. 
   In one exemplary embodiment of the above-mentioned sheet feed cassette, a front surface of the protective sheet may be formed of fluoroplastic. 
   In one exemplary embodiment of the above-mentioned sheet feed cassette, the protective sheet may include a plurality of the protective sheets, and the plurality of protective sheets may be replaceably overlaid on one another. 
   In one exemplary embodiment of the above-mentioned sheet feed cassette, the protective sheet may include a rear surface having an adhesive material so that the protective sheet may be affixed to the portion of the sheet feed cassette that contacts the sheet. 
   In one exemplary embodiment of the above-mentioned sheet feed cassette, the protective sheet may include a tab from which the protective sheet may be peeled off from the portion of the sheet feed cassette that contacts the sheet, and no adhesive material may be provided on a rear surface of the tab. 
   In one exemplary embodiment of the above-mentioned sheet feed cassette, the protective sheet may include a tab from which the protective sheet may be peeled off from the portion of the sheet feed cassette that contacts the sheet, and a sheet piece having no adhesive material may be affixed on the rear surface of the tab. 
   In one exemplary embodiment of the above-mentioned sheet feed cassette, the portion of the sheet feed cassette that contacts the sheet may include a side frame. 
   In one exemplary embodiment of the above-mentioned sheet feed cassette, the portion of the sheet feed cassette that contacts the sheet may include a bottom plate. 
   At least one embodiment of the present invention provides an image forming apparatus that may include a sheet conveyance path that transports a sheet, and a protective sheet provided on a portion of the sheet conveyance that contacts the sheet so as to prevent an adhesive material from sticking thereto. 
   The above-mentioned image forming apparatus may further include a protective sheet storage unit for storing the protective sheet for replacement. 
   The above-mentioned image forming apparatus may further include a storage area for storing a used protective sheet. 
   Additional features and advantages of the present invention will be more fully apparent from the following detailed description of exemplary embodiments, the accompanying drawings and the associated claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description of exemplary embodiments when considered in connection with the accompanying drawings, wherein: 
       FIG. 1  is a schematic diagram illustrating an example laser printer as an image forming apparatus according to one exemplary embodiment of a present invention; 
       FIG. 2  is a perspective view illustrating a sheet feed cassette; 
       FIG. 3  is an exploded perspective view illustrating a manner in which a protective sheet is affixed relative to a side frame; 
       FIG. 4  is a cross-sectional view illustrating the protective sheet of  FIG. 3 ; 
       FIG. 5  is a front view illustrating the protective sheet including a tab; 
       FIG. 6  is a perspective view illustrating a manner in which a plurality of the protective sheets including the tab are overlaid on one another; 
       FIG. 7  is a perspective view illustrating one variation of the tab of  FIG. 6 ; 
       FIG. 8  is a perspective view illustrating a manner in which another variation of the protective sheet is disposed; 
       FIG. 9  is a perspective view illustrating a manner in which another variation of the protective sheet is disposed; 
       FIG. 10A  is a cross-sectional view illustrating a manner in which a protective sheet according to another exemplary embodiment of the present invention is disposed; and 
       FIG. 10B  is a side view illustrating a manner in which the protective sheet of  FIG. 10A  is disposed. 
   

   DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
   In describing exemplary embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this patent specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner. For the sake of simplicity of drawings and descriptions, the same reference numerals are given to materials and constituent parts having the same functions, and descriptions thereof will be omitted unless otherwise stated. 
   Exemplary embodiments of the present invention are now explained below with reference to the accompanying drawings. In the later described comparative example, exemplary embodiment, and alternative example, the same reference numerals will be given to constituent elements such as parts and materials having the same functions, and the descriptions thereof will be omitted. 
   Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, particularly to  FIG. 1 , a structure of a laser printer as an image forming apparatus according to an exemplary embodiment of the present invention is described. 
   One exemplary embodiment of the present invention will be explained below with reference to  FIGS. 1 through 9 . With reference to  FIG. 1 , a description will now be given of an exemplary structure of a laser printer as an image forming apparatus according to one exemplary embodiment. The image forming apparatus includes a sheet feed cassette  1  attachably and detachably disposed at a bottom end portion of the image forming apparatus. 
   Paper or a recording sheet P which is printed within the image forming apparatus is ejected and stacked on a catch tray  2  formed on an upper surface of the apparatus main body. Paper, as used herein, includes a sheet, transfer member, printable media and the like. Typically, but not necessarily, paper is the medium of the sheet on which an image is to be formed. For simplicity, this Detailed Description section refers to paper, sheets thereof, paper feeder, etc. It should be understood, however, that the sheets, etc., are not limited only to paper. 
   Devices associated with image formation are installed in the apparatus main body. Such devices include: drum-type photoreceptors  3  of different colors of yellow (Y), magenta (M), cyan (C) and black (BK), each rotates in an arrow B direction, electrophotographic process members, an optical writing unit  4 , an intermediate transfer belt  5  which rotates in an arrow A direction, a fixing unit  6  and so forth associated with image formation. 
   The electrophotographic process members are disposed around the photoreceptors  3 . The optical writing unit  4  irradiates a laser beam for forming an electrostatic latent image. While a single polygonal mirror has been illustrated, two, three, four, or any desired number of polygonal mirrors may be utilized. The intermediate transfer belt  5  transfers toner images of different colors formed on the respective photoreceptors  3  to the recording sheet P. The fixing unit  6  performs fixing processing with respect to the recording sheet P on which the toner images are transferred. 
   A sheet feed/conveyance path of the recording sheet P relative to the intermediate transfer belt  5  is configured in a substantially vertical direction at a front side of the apparatus main body. The sheet feed cassette  1 , which feeds the recording sheet P to the sheet feed/conveyance path using the sheet feed roller  7  or the like, is disposed at the very bottom position of the apparatus main body and is drawable in a frontward direction shown by an arrow M. Alternatively, the tray can be removed and inserted from either side, or even the rear, if desired. Moreover, the tray/cassette may be fixed or non-removable. 
   The recording sheet P loaded on the sheet feed cassette  1  is fed by the sheet feed roller  7  and is ejected onto the catch tray  2  after passing through the sheet feed/conveyance path as shown by a dotted line in  FIG. 1 . The image forming apparatus further includes a manual feed tray  8  as shown in  FIG. 1 . 
   As shown in  FIG. 2 , the sheet feed cassette  1  includes a pair of side frames  10  and  11 , an end frame  12 , a bottom plate  13  and so forth. The side frames  10  and  11  are each disposed on the bottom plate  13  and integrally include rack portions  14  and  15  which extend in the sheet width direction perpendicular to the sheet feed direction shown by an arrow. The rack portions  14  and  15  fit with a single pinion  16  so as to be able to synchronously adjust the alignment of the paper in the paper width direction. The end frame  12  is movable in the sheet feed direction along a rail  17  and is allowed to be positioned at a given position by a stopper  18 . 
   As shown in  FIG. 3 , a protective sheet  20  having a similar or the same shape as that of the inner surface of a vertical wall  10   a  is affixed on an inner surface of a vertical wall  10   a  of the side frame  10  on the left side shown by hatching. The protective sheet  20  may be used for preventing an adhesive material from sticking to the vertical wall  10   a.    
   As shown in  FIG. 4 , according to an exemplary embodiment, the protective sheet  20  is formed of a surface layer or a parting layer  20   a  of fluoroplastic, a supporting layer  20   b  which may be chartaceous, an adhesive layer  20   c , and a release coated paper or tape  20   d . The adhesive layer  20   c  of the protective sheet  20  is affixed on the inner surface of the vertical wall  10   a , by first peeling off the release coated paper (protective tape)  20   d  and then pressing the protective sheet  20  against the vertical wall  10   a.    
   Though not shown, similar to the side frame  10  as described above, on the inner surface of the vertical wall of the side frame  11  on the right side and on the inner surface of the end frame  12  is affixed the protective sheet  20  having a size which corresponds to the size of the respective inner surfaces. 
   On the front surface of the bottom plate  13  is affixed the protective sheet  20  having a dimension indicated by a double-dotted line as shown in  FIG. 2 . When affixing the protective sheet  20  corresponding to the bottom plate  13 , the protective sheet  20  is placed on the bottom plate  13  in a state where the release coated paper  20   d  is not peeled off. 
   The side frames  10  and  11 , and the end frame  12  are positioned in accordance with the protective sheet  20 , and subsequently the release coated paper  20   d  of the protective sheet  20  is peeled off so as to affix the protective sheet  20 . In a case where the recording sheets of different sizes are used, the size of the protective sheet  20  is configured to correspond to the paper of the smallest size. 
   The dimension of the adhesive layer  20   c  on the rear surface of the protective sheet  20  does not have to cover the entire surface thereof. The adhesive layer  20   c  may have a narrow width. In such a case, the release coated paper  20   d  may have a tape-like shape. In a case where the release coated paper  20   d  has the tape-like shape, the peeling area becomes less so that the protective sheet  20  may be easily and quickly affixed. 
   When the recording sheets P are loaded in the sheet feed cassette  1 , the side frames  10  and  11 , the end frame  12 , and the bottom plate  13  may be the areas or the surfaces with which the recording sheets P contact. Thus, in a case where the paper such as the release coated paper containing an adhesive material is used, there may be a problem in which the adhesive material leaks out of the end portion of the paper or a cut, and sticks to the surfaces of the side frames  10  and  11 , the end frame  12  and the bottom plate  13 . 
   However, when the protective sheet  20  is affixed on the places with which the paper may come into contact as described in the exemplary embodiment, it may be possible to prevent the adhesive material from sticking. The parting layer  20   a  that constitutes the front surface of the protective sheet  20  is not limited to fluoroplastic, and may be of other materials which prevent the adhesive material from sticking. 
   According to one exemplary embodiment, the protective sheet  20  is affixed on the portion of the sheet feed cassette, i.e., the side frames  10  and  11 , the end frame  12 , and the bottom plate  13 , that contacts the sheet. Thereby, it may be possible to prevent the adhesive material from sticking. Alternatively, the protective sheet  20  may be affixed only on the side frames  10  and  11 . Furthermore, the similar effects may be attained when the protective sheet  20  may be affixed only to a portion of the side frames  10  and  11 . 
   It may be possible that the protective sheet  20  may be contaminated over time so that the adhesive material may stick thereon through contamination. Consequently, the function of the protective sheet  20  for preventing the adhesive material from sticking may be deteriorated. In such a case, it may be necessary to change or replace the protective sheet  20 . 
   In order to facilitate the replacement, as shown in  FIG. 5 , for example, a tab  20   e  as a protruding portion may be formed at an end portion of the protective sheet  20  so that the tab  20   e  may serve as the point of peeling from where the protective sheet  20  may be peeled. In this case, the adhesive layer  20   c  is not provided on the rear surface of the tab  20   e . Thus, the tab  20   e  is an adhesiveless surface. When replacing the protective sheet  20 , the adhesion of the adhesive layer  20   c  of the protective sheet  20  is configured such that the protective sheet  20  may be peeled off at ease. 
   As shown in  FIG. 6 , a plurality of the protective sheets  20  may be overlaid on one another. Accordingly, when the protective sheet  20  is contaminated, the contaminated protective sheet  20  may be peeled off one sheet at a time so that a new state, that is, a clean state is recovered. The same may be said when a material with less parting capability is used on the front surface. In other words, when the adhesive material sticks to the protective sheet  20 , the contaminated protective sheet  20  may be peeled off one sheet at a time so that a new state is recovered. 
   In order not to provide adhesion on the rear surface of the tab  20   e , as shown in  FIG. 7 , a sheet piece  21 , which may be of a piece of paper, may be affixed on the rear surface of the tab  20   e  in a state where the adhesive layer  20   c  is provided on the entire rear surface of the protective sheet  20  including the rear surface of the tab  20   e.    
   As shown in  FIG. 8 , notch portions  22   a  and  22   b  may be provided on a side frame  22 . A protective sheet  23  may be disposed on the side frame  22 . The protective sheet  23  may include fitting tabs  23   a  and  23   b  which are provided in a protruding manner and are fitted with the notch portions  22   a  and  22   b . The protective sheet  23  does not include an adhesive layer, and is positioned simply by the fitting tabs  23   a  and  23   b , thereby making it easy to replace. Such a method in which no adhesive layer is provided to the protective sheet  23  may similarly be applied to the end frame  12  and the bottom plate  13 . 
   The adhesion protecting function which prevents the adhesive material from sticking may still be attained without having the protective sheet affixed on the entire surfaces of the side frames or the like. For example, as shown in  FIG. 9 , when a plurality of the protective sheets  24  having a small dimension are affixed partially on the inner surface of the vertical wall  10   a  of the side frame  10 , the end portion of the paper comes into contact with only the protective sheets  24 , and the area of the paper relative to the surface without the protective sheets  24  is in a non-contact state. 
   The protective sheets  24  having a small dimension is easy to affix and to handle, while achieving the same adhesion protecting function, which prevents the adhesive material from sticking, similarly to the case in which the protective sheet is affixed on the entire surface. 
   Reference is now made to  FIGS. 10A and 10B  to illustrate another exemplary embodiment. In the one exemplary embodiment described above, exemplary aspects to prevent the adhesive material from sticking to the sheet feed cassette  1  are provided. A similar problem as discussed above may occur in a conveyance path in an image forming apparatus when a recording sheet that contains an adhesive material is transported. 
   In another exemplary embodiment, ways in which the problem may be reduced or even eliminated are addressed. As shown in  FIG. 1 , the paper may be rubbed against the conveyance path, especially against an area S indicated by a dotted circle where the sheet conveyance path is curved. Consequently, the adhesive material may easily stick to the area S. 
   In  FIG. 10A , reference numerals  25  and  26  indicate a pair of conveyance rollers. A reference numeral  27  indicates a lower guide plate, and  28  indicates an upper guide plate. On an inner surface of the lower guide plate  27 , a protective sheet  30  having a similar structure as that of the protective sheet  20  described above is attachably and detachably affixed along a curved surface. The protective sheet  30  may include a plurality of protective sheets which are overlaid on one another. 
   The protective sheet  30  may be formed of a surface layer or a parting layer of fluoroplastic, a supporting layer which may be chartaceous, an adhesive layer, and a release coated paper or tape. The adhesive layer of the protective sheet is affixed on the inner surface of the lower guide plate  27 , by first peeling off the release coated paper (protective tape), and then pressing the protective sheet against lower guide plate  27 . 
   A tab, which is similar to the tab  20   e  as a protruding portion described above, may be formed at an end portion of the protective sheet  30  so that the tab may serve as the point of peeling from where the protective sheet  30  may be peeled. 
   A sheet piece, which is similar to the sheet piece  21  as described above, may be affixed on the rear surface of the tab in a state where the adhesive layer is provided on the entire rear surface of the protective sheet  30  including the rear surface of the table. 
     FIG. 10B  is a side view of the paper path of  FIG. 10A . Using the arrangement of  FIGS. 10A and 10B , it may be possible to prevent the adhesive material from sticking on the inner surface of the lower guide plate  27 . Furthermore, an optimal conveyance state in the image forming apparatus may be maintained for an extended period of time. 
   It may be possible to provide a replacement protective sheet storage unit which stores the protective sheet for replacement so that the protective sheet may easily and quickly be replaced. The replacement protective sheet storage unit may be provided, for example, inside the front cover of the image forming apparatus in a pocket-like manner. 
   Furthermore, it may be possible to provide a waste protective sheet storage unit which stores a used protective sheet so that processing after replacement may easily and quickly be performed. The waste protective sheet storage unit may be provided, for example, integrally to a waste toner tank in the image forming apparatus in a pocket-like manner. Accordingly, the waste products may be stored in a concentrated manner. 
   One or more embodiments of the present invention may be conveniently implemented using a conventional general purpose digital computer programmed according to the teachings of the present specification, as will be apparent to those skilled in the computer art. Appropriate software coding can readily be prepared by skilled programmers based on the teachings of the present disclosure, as will be apparent to those skilled in the software art. One or more embodiments of the present invention may also be implemented by the preparation of application specific integrated circuits or by interconnecting an appropriate network of conventional component circuits, as will be readily apparent to those skilled in the art. 
   Any of the aforementioned methods may be embodied in the form of a system or device, including, but not limited to, any of the structure for performing the methodology illustrated in the drawings. 
   Further, any of the aforementioned methods may be embodied in the form of a program. The program may be stored on a computer readable media and is adapted to perform any one of the aforementioned methods, when run on a computer device (a device including a processor). Thus, the storage medium or computer readable medium, is adapted to store information and is adapted to interact with a data processing facility or computer device to perform the method of any of the above mentioned embodiments. 
   The storage medium may be a built-in medium installed inside a computer device main body or removable medium arranged so that it can be separated from the computer device main body. Examples of the built-in medium include, but are not limited to, rewriteable non-volatile memories, such as ROMs and flash memories, and hard disks. Examples of the removable medium include, but are not limited to, optical storage media such as CD-ROMs and DVDs; magneto-optical storage media, such as MOs; magnetism storage media, such as floppy disks, cassette tapes, and removable hard disks; media with a built-in rewriteable non-volatile memory, such as memory cards; and media with a built-in ROM, such as ROM cassettes. 
   Example embodiments being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.