Patent Publication Number: US-8113505-B2

Title: Image forming apparatus and paper feeding device thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 2008-0130234, filed on Dec. 19, 2008 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relate generally to an image forming apparatus having an improved paper feeding performance. 
     BACKGROUND OF RELATED ART 
     Generally speaking, image forming apparatuses refer to apparatuses forming images on printing media, and may include, e.g., a printer, a copier, a facsimile and a multifunction apparatus that combines some functions of the afore-mentioned. Hereinafter, for the sake of convenience and readability, the printing medium may be referred to as ‘paper’ in the descriptions below, which should not, however, be construed as limiting the printing medium to paper. 
     The image forming apparatus is equipped with a paper feeding device that supplies paper to a printing device also included in the apparatus. The paper received in the paper feeding device is picked up by a pickup unit, and is fed to the printing device along a predetermined path. 
     The paper feeding device may include a multi-sheet feeding prevention unit to prevent simultaneous feeding of multiple sheets of paper. The multi-sheet feeding prevention unit is typically disposed to face the pickup unit and to bias the paper toward the pickup unit. 
     While the image forming apparatus is performing a printing operation, the paper may be caught between the pickup unit and the multi-sheet feeding prevention unit, resulting in a paper because of the pressure exerted between the pickup unit and the multi-sheet feeding prevention unit. If the user forcibly pulls on the paper, the paper, the pickup unit, and/or the multi-sheet feeding prevention unit may become damaged. A paper feeding device capable of convenient removal of jammed paper is thus desirable. 
     SUMMARY OF DISCLOSURE 
     In accordance with one aspect of the present invention, an image forming apparatus may be provided to comprise a main body, a printing media feeding cassette, a pickup roller and a multi-sheet feeding prevention unit. The main body may be configured to support a printing device received therein. The printing media feeding cassette may be detachably mounted to the main body, and may be configured to support one or more printing media receive therein. The pickup roller may be configured to pick up a printing medium from the printing media feeding cassette. The multi-sheet feeding prevention unit may be configured to impart a pressing force on the pickup roller when the multi-sheet feeding prevention unit is in a contact position and to release the pressing force to the pickup roller when the multi-sheet feeding prevention unit is in a releasing position. The multi-sheet feeding prevention unit may be in the contact position when the printing media feeding caste is mounted to the main body, and may be in the releasing position when the printing media feeding cassette is at least partially detached from the main body. 
     The multi-sheet feeding prevention unit may comprise a multi-sheet feeding prevention member facing the pickup roller and a holder supporting the multi-sheet feeding prevention member. 
     The printing media feeding cassette, when it is mounted in the main body, may press against the holder so that the multi-sheet feeding prevention member is in a pressing contact with the pickup roller. 
     The multi-sheet feeding prevention unit may further comprise an elastic member to elastically bias the holder in such a manner elastically biasing the multi-sheet feeding prevention member toward the pickup roller. 
     One end of the elastic member may be supported by the holder while the other end of the elastic member may be supported by the printing media feeding cassette. 
     The holder may comprise a rotating shaft, a supporting arm and an operating arm. The supporting arm may extend from the rotating shaft, and may be configured to support the multi-sheet feeding prevention member. The operating arm may extend from the rotating shaft, and may be configured to face the printing media feeding cassette. 
     The image forming apparatus may further comprise an elastic member disposed between the operating arm and the printing media feeding cassette. 
     The multi-sheet feeding prevention unit may further comprise a cap coupled to the operating arm and configured to receive the elastic member. 
     The image forming apparatus may further comprise a guide frame having a guide surface by which the printing medium picked up by the pickup roller is guided along a paper feed path. The holder may be rotatably mounted to the guide frame. 
     According to another aspect of the present disclosure, an image forming apparatus may be provided to comprise a printing media feeding cassette, a pickup roller and a multi-sheet feeding prevention unit. The printing media feeding cassette may have a paper receiving surface on which one or more sheets of paper are to be stacked. The pickup roller may be configured to pick up a paper from the printing media feeding cassette. The multi-sheet feeding prevention unit may be moveable between a contact position and a releasing position, and may have a multi-sheet feeding prevention member supported on an end thereof. The multi-sheet feeding prevention unit may be configured to be in the contact position when the multi-sheet feeding prevention unit is in an interfering contact with the printing media feeding cassette. The multi-sheet feeding prevention member may impart a first pressing force on the pickup roller when the multi-sheet feeding prevention unit is in the contact position. The multi-sheet feeding prevention unit may be configured to be in the releasing position when the multi-sheet feeding prevention unit is not in contact with the printing media feeding cassette. The multi-sheet feeding prevention member may impart a second pressing force less than the first pressing force on the pickup roller when the multi-sheet feeding prevention unit is in the releasing position. 
     When the multi-sheet feeding prevention unit is in the releasing position, the multi-sheet feeding prevention member may not contact the pickup roller so that the second pressing force imparted on the pickup roller is zero. 
     The multi-sheet feeding prevention unit may further comprise a holder and an elastic member. The holder may be rotatably disposed in the image forming apparatus, and may be configured to support the multi-sheet feeding prevention member. One end of the elastic member may be supported by the holder while the other end may be supported by the printing media feeding cassette. 
     The holder may comprise a rotating shaft, a supporting arm and an operating arm. The supporting arm may extend from the rotating shaft in a first direction toward the pickup roller, and may support the multi-sheet feeding prevention member at one end thereof away from the rotating shaft. The operating arm may extend from the rotating shaft in a second direction away from the pickup roller, and may have a surface opposingly facing the printing media feeding cassette. 
     The printing media feeding cassette may be configured to press against the operating arm of the holder so as to bias the multi-sheet feeding prevention member toward the pickup roller. 
     The image forming apparatus may further comprise a guide frame having a guide surface by which the printing medium picked up by the pickup roller is guided along a paper feed path defined within the image forming apparatus. The holder may be rotatably supported on the guide frame. 
     According to yet another aspect of the present disclosure, a printing media feeding device may be useable in an image forming apparatus that includes a printing media feeding cassette in which to receive one or more printing media, and may comprise a pickup roller and a multi-sheet feeding prevention unit. The pickup roller may be configured to pickup up a printing medium from the printing media feeding cassette. The multi-sheet feeding prevention unit may have a multi-sheet feeding prevention member opposingly facing the pickup roller. The multi-sheet feeding prevention unit may be configured to rotate about a rotational shaft in cooperation with the printing media feeding cassette of the image forming apparatus. 
     The multi-sheet feeding prevention unit may be rotatable about the rotational shaft between a pressing position and a releasing position. The multi-sheet feeding prevention unit may be in the pressing position when the multi-sheet feeding prevention unit is in an interfering contact with the printing media cassette installed in the image forming apparatus. The multi-sheet feeding prevention unit may be in the releasing position when the multi-sheet feeding prevention unit is not in contact with the printing media cassette. The multi-sheet feeding prevention member may impart a first pressing force on the pickup roller when the multi-sheet feeding prevention unit is in the pressing position. The multi-sheet feeding prevention member may impart a second pressing force less than the first pressing force on the pickup roller when the multi-sheet feeding prevention unit is in the releasing position. 
     The multi-sheet feeding prevention unit may further comprise a supporting arm and an operating arm. The supporting arm may extend from the rotational shaft in a first direction toward the pickup roller, and may support the multi-sheet feeding prevention member at one end thereof away from the rotational shaft. The operating arm may extend from the rotational shaft in a second direction away from the pickup roller, and may have a surface opposingly facing the printing media feeding cassette. 
     The multi-sheet feeding prevention unit may further comprise an elastic member disposed between the printing media feeding cassette and the operating arm. The elastic member may elastically bias the multi-sheet feeding prevention member toward the pickup roller when the multi-sheet feeding prevention unit is in a pressing contact with the printing media feeding cassette. 
     When the printing media feeding cassette is in pressing contact with the operating arm of the multi-sheet feeding prevention unit, the multi-sheet feeding prevention member may impart a first pressing force on the pickup roller. When the operating arm of the multi-sheet feeding prevention unit is not in contact with the printing media cassette, the multi-sheet feeding prevention member may impart a second pressing force less than the first pressing force on the pickup roller. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various features and advantages of the disclosure will become more apparent by the following detailed description of several embodiments thereof with reference to the attached drawings, of which: 
         FIG. 1  is a view showing the structure of an image forming apparatus according to an embodiment of the present disclosure; 
         FIG. 2  is a partially enlarged view of the relevant portion of the image forming apparatus of  FIG. 1 ; 
         FIG. 3  shows the portion of an image forming apparatus shown in  FIG. 2  with the paper feeding cassette separated; 
         FIG. 4  is a perspective view showing the structure of a paper feeding device of an image forming apparatus according to an embodiment of the present disclosure; and 
         FIG. 5  is a perspective view showing portions of the paper feeding cassette, a pickup guide and a multi-sheet feeding prevention unit of the image forming apparatus according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF SEVERAL EMBODIMENTS 
     Reference will now be made in detail to the embodiment, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. While the embodiments are described with detailed construction and elements to assist in a comprehensive understanding of the various applications and advantages of the embodiments, it should be apparent however that the embodiments can be carried out without those specifically detailed particulars. Also, well-known functions or constructions will not be described in detail so as to avoid obscuring the description with unnecessary detail. It should be also noted that in the drawings, the dimensions of the features are not intended to be to true scale and may be exaggerated for the sake of allowing greater understanding. 
       FIG. 1  is a view showing the structure of an image forming apparatus according to an embodiment of the present disclosure. 
     As shown in  FIG. 1 , an image forming apparatus  1  according to an embodiment may comprise a main body  10 , a paper feeding device  20 , a printing device  30  and a paper discharging device  100 . 
     The main body  10  may define the overall external appearance of the image forming apparatus, and may support various components therein. The paper feeding device  20  supplies paper to the printing device  30 . The paper feeding device  20  will be described in greater detail later. 
     The printing device  30  prints images on the paper fed from the paper feeding device  20 . By way of a non-limiting example, an electrophotographic type image forming apparatus is described below. However, it should be readily apparent to those skilled in the art that various aspects and embodiments herein described are applicable to other types of image forming apparatus, including, for example, an inkjet type image forming apparatus. According to an embodiment, the printing device  30  of an electrophotographic type image forming apparatus may comprise photosensitive mediums  40 K,  40 C  40 M and  40 Y, charging devices  50 , a laser scanning unit  60 , a developing unit  70 , a transfer unit  80  and a fixing unit  90 . 
     The charging devices  50  may uniformly electrify the surface of the respective corresponding one of the photosensitive mediums  40 K,  40 C  40 M and  40 Y. The laser scanning unit  60  may scan the electrified surfaces of the photosensitive mediums  40 K,  40 C  40 M and  40 Y with laser beams corresponding to the image data, thereby forming electrostatic latent images on the surfaces of the photosensitive mediums  40 K,  40 C  40 M and  40 Y. 
     The developing unit  70  may supply toner to the electrostatic latent images formed on the photosensitive mediums  40 K,  40 C  40 M and  40 Y, thereby developing the electrostatic latent images into visible toner images. For example, the developing unit  70  may be constituted by four developing devices  70 K,  70 C  70 M and  70 Y, storing black, cyan, magenta and yellow toners, respectively. 
     Each of the developing devices  70 K,  70 C  70 M and  70 Y may include a supplying roller  71  and a developing roller  72 . The supplying rollers  71  supply the toner to the corresponding developing roller  72 . The developing rollers  72  in turn supply the toner respectively to the photosensitive mediums  40 K,  40 C,  40 M and  40 Y to develop the electrostatic latent images into the visible toner images. 
     The transfer unit  80  may comprise a transfer belt  81 , first transfer rollers  82 , a second transfer roller  83  and supporting rollers  84 . The transfer rollers  81  may rotates while pressing against the corresponding one of the photosensitive mediums  40 K,  40 C  40 M and  40 Y. The transfer belt  81  may rotate while being supported by the supporting rollers  84  around a loop path that includes a portion in which the transfer belt  81  is interposed between the transfer rollers  81  and the photosensitive mediums  40 K,  40 C  40 M and  40 Y. 
     The visible images formed on the photosensitive mediums  40 K,  40 C  40 M and  40 Y may be transferred to the transfer belt  81  by the first transfer rollers  82  in an overlapping manner. The overlapped images on the transfer belt  81  may be transferred onto a paper fed from the paper feeding device  20  that pass between the second transfer roller  83  and the transfer belt  81 . 
     The paper that has passed through the transfer unit  80  may subsequently be introduced into the fixing device  90 , which may comprise a heating roller  91  and a pressing roller  92 . The paper bearing thereon the transferred toner images may be made to pass between the heating roller  91  and the pressing roller  92 , during which the toner images are fixed to the paper by heat and pressure. 
     Having passed through the fixing device  90 , the paper may be guided to the paper discharging unit  100 , and may be discharged to the outside by a discharging roller  101 . 
       FIG. 2  is a partially enlarged view of the circled portion of  FIG. 1 .  FIG. 3  shows the portion shown in  FIG. 2 , but with the paper feeding cassette separated from the main body  10 .  FIG. 4  is a perspective view showing the structure of the paper feeding device according to an embodiment. In  FIG. 4 , a pickup guide and the paper feeding cassette are separately illustrated. 
     Referring to  FIG. 1  to  FIG. 4 , the paper feeding device  20  according to an embodiment may comprise the paper feeding cassette  200 , a pickup roller  300  and a multi-sheet feeding prevention unit  400 . 
     The paper feeding cassette  200  is structured to receive papers S, and may be detachably mounted to the main body  10 . The pickup roller  300  may pick up the paper S from the paper feeding cassette  200 , and may feed the picked up paper S to a feeding roller  110  (shown in  FIG. 1 ). 
     A guide frame  120  may further be provided in front of the paper feeding cassette  200 . As shown in  FIG. 4 , the guide frame  120  may comprise a guide surface  122  having a plurality of ribs  121  extending along the paper feeding direction so as to guide the paper picked up by the pickup roller  300  to the feeding roller  110 . The feeding roller  110  may align the leading end of the paper being fed from the pickup roller  300 , and may feed the paper further along the paper path toward the second transfer roller  83 . 
     The multi-sheet feeding prevention unit  400  may press against the pickup roller  300  so that the pickup roller  300  can pick up the paper one sheet at a time. To that end, the multi-sheet feeding prevention unit  400  may be disposed at a lower part of the pickup roller  300 , and may press the rear side of the paper while the paper is being picked up, thereby reducing simultaneous pickup of multiple sheets, that is, a multi-sheet feeding. 
     The paper feeding cassette  200  may comprise a cassette body  210  and a knock-up plate  220  supporting the received paper S. The knock-up plate  220  may be pivotably mounted to the cassette body  210 . More particularly, the knock-up plate  220  may be connected to the cassette body  210  through a hinge shaft  221  (see  FIG. 4 ) formed at the rear end thereof, therefore allowing the leading end of the knock-up plate  220  to pivot up and down. 
     The pickup roller  300  may be disposed above the leading end of the knock-up plate  220 . The pickup roller  300  may be connected to a pickup shaft  310  rotatably mounted to the main body  10 . The pickup shaft  310  may be rotated by a rotational force received from a driving motor (not shown) mounted in the main body  10 . 
     The pickup roller  300  may comprise a rotating pickup member  320  configured to contact the paper stacked on the knock-up plate  220  and a pair of idle rollers  330  mounted at the sides of the rotating pickup member  320  that may rotate idly. 
     The rotating pickup member  320  may include a contact part  321  contacting the paper only in a predetermined section during the rotation of the rotating pickup member  320 . The contact part  321  may protrude in the radial direction of the idle roller  330 . As shown in  FIG. 2 , when the contact part  321  of the rotating pickup member  320  is in contact with the paper, the idle roller  330  may be separated from the paper. On the other hand, when the contact part  321  is out of contact with the paper, the idle roller  330  may be in contact with the paper. 
     When the paper S passes by an upper part of the multi-sheet feeding prevention unit  400 , the idle roller  330  presses the multi-sheet feeding prevention unit  400  with a predetermined pressure so that only the uppermost sheet of the paper may be picked up and fed from the knock-up plate  220 . 
     The paper feeding device  20  may comprise an elevating unit  500  to move the knock-up plate  220  up and down. The elevating unit  500  may comprise a spring  510  elastically biasing the knock-up plate  220  upward and a pair of cams  520  that may be connected to both sides of the pickup shaft  310 , and which may rotate along with the pickup roller  300 . 
     While the pickup shaft  310  is rotating, the cams  520  press the sidewalls of the knock-up plate  220 , thereby causing the knock-up plate  220  to pivot downward. Guide rollers  530  may be further formed at the sidewalls of the knock-up plate  220  at locations corresponding to the cams  520  so as to allow the cams  520  to press the knock-up plate  220  more efficiently. 
     When the cams  520  rotate to a position where they are separated from the knock-up plate  220 , the knock-up plate  220  is pivoted upward by the spring  510 . 
       FIG. 5  is a perspective view showing the pickup guide, a portion of the paper feeding cassette and the multi-sheet feeding prevention unit of an image forming apparatus according to an embodiment of the present disclosure. 
     As shown in  FIGS. 2 ,  3  and  5 , the multi-sheet feeding prevention unit  400  may comprise a multi-sheet feeding prevention member  410  facing the pickup roller  300 , and a holder  420  supporting the multi-sheet feeding prevention member  410 . 
     The multi-sheet feeding prevention member  410  may be configured to press against the pickup roller  300  when the pickup roller  300  picks up the paper. The multi-sheet feeding prevention unit  400  may further comprise a friction pad  411  imparting frictional force on the paper being passed through the pickup roller  300 . 
     The holder  420  may be rotatably mounted to the guide frame  120  at a position corresponding to the pickup roller  300 . The guide frame  120  may include a holder receiving part  123  that receives the holder  420 . A shaft connection hole  124  may be formed on each side of the holder receiving part  123 . In addition, a guide protrusion  125  including a shaft supporting recess  125   a  may be formed on the bottom surface of the holder receiving part  123 . 
     The holder  420  may comprise a rotating shaft  422 , a supporting arm  424  extending from the rotating shaft  422  in one direction and an operating arm  426  extending from the rotating shaft  422  in another substantially opposing direction. Both ends of the rotating shaft  422  may be received into the shaft connection holes  124  whereas the middle portion of the rotating shat  422  may be supported by the shaft supporting recess  125   a.    
     An upper surface of the supporting arm  424  that faces the pickup roller  300  may have formed thereon a pad receiving recess  424   a  into which the friction pad  411  may be received. A locking protrusion  424   b  is protruded from an end of the supporting arm  424  such that the supporting arm  424  is supported by the guide surface  122  of the guide frame  120 . 
     The operating arm  426  faces the paper feeding cassette  200  adjacent the front portion of the paper feeding cassette  200 . A pressing part  230  may be formed on the front side of the paper feeding cassette  200  to press against the holder  420 . When the paper feeding cassette  200  is mounted to the main body  10 , the pressing part  230  may press the operating arm  426  of the holder  420 , thereby bringing the multi-sheet feeding prevention member  410  into close contact with the pickup roller  300 . 
     As shown in  FIG. 3 , when the paper feeding cassette  200  is separated from the main body  10 , the pressing part  230  of the paper feeding cassette  200  may be spaced apart from the operating arm  426 . Therefore, the pressing force exerted to the operating arm  426  is released. Accordingly, the supporting arm  424  may pivot downward by its own weight so as to separate the multi-sheet feeding prevention member  410  from the pickup roller  300 . In such state, a sheet of paper that has become jammed between the pickup roller  300  and the multi-sheet feeding prevention member  410  during a pickup operation, the user is able to remove the paper with ease. Moreover, damages to the components, such as, for example, the pickup roller  300 , the pickup shaft  310 , and/or the multi-sheet feeding prevention member  410 , that may have otherwise occurred in a conventional paper feeding device when the user forcibly pulls on the jammed paper, may be prevented. 
     An elastic member  430  may further be disposed between the pressing part  230  of the paper feeding cassette  200  and the operating arm  426  of the holder  420  in order to bias the holder  420  so that the multi-sheet feeding prevention member  410  elastically pushes the pickup roller  300 . The elastic member  430  may comprise, for example, a compressed coil spring. 
     One end of the elastic member  430  may be supported by the operating arm  426  while the other end may be supported by the pressing part  230  of the paper feeding cassette  200  mounted to the main body  10 . The operating arm  426  of the holder  420  may further be provided with a connection protrusion  426   a  for mounting the elastic member  430 . 
     Furthermore, the operating arm  426  may further comprise a cap  440  to prevent the separation of the elastic member  430 . The cap  440  may be constituted by a cap body  441  receiving the elastic member  430  and a hook part  442  formed at an end of the cap body  441  for coupling the cap body  441  with the operating arm  426 . The operating arm  426  may additionally include a penetration hole  426   b  for receiving the hook part  442 . The hook part  442  may extend from the cap body  441  by a sufficient length so as to allow the cap  440  to move forward and backward while coupled to the operating arm  426 . 
     Hereinafter, the paper feeding operation and the jam removal operation of the image forming apparatus will be described with reference to  FIGS. 2 and 3 . 
     In a state where the paper feeding cassette  200  is mounted to the main body  10  as shown in  FIG. 2 , the paper feeding cassette  200  elastically supports the elastic member  430  mounted to the operating arm  426  of the holder  420 , thereby pressing the operating arm  426 . Therefore, the multi-sheet feeding prevention member  410  mounted to the supporting arm  424  is brought into close contact with the pickup roller  300  by a rotational force applied in the direction A. 
     In such state, when the pickup roller  300  rotates, the uppermost sheet of the paper S stacked in the knock-up plate  220  is picked up by the pickup roller  300 . Since the multi-sheet feeding prevention member  410  presses against the pickup roller  300 , multi-sheet feeding of the paper may be prevented. 
     When a paper jam occurs during the paper pickup operation, the paper may be caught between the pickup roller  300  and the multi-sheet feeding prevention member  410  as shown in  FIG. 3 . 
     If the paper feeding cassette  200  is separated from the main body  10  in this state, the pressing force of the paper feeding cassette  200  exerted to the operating arm  426  is released, and therefore the holder  420  pivots in the direction B by its own weight. Accordingly, since the pressing force between the pickup roller  300  and the multi-sheet feeding prevention member  410  is released, the user is able to easily remove the jammed paper. 
     While the disclosure has been particularly shown and described with reference to several embodiments thereof with particular details, it will be apparent to one of ordinary skill in the art that various changes may be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the following claims and their equivalents.