Patent Publication Number: US-7221880-B2

Title: Waste toner transfer apparatus and electrophotographic printer using the same

Description:
BACKGROUND OF THE INVENTION 
   This application claims the benefit under 35 U.S.C. §119(a) of Korean Patent Application No. 2003-45386, filed on Jul. 4, 2003, in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference. 
   1. Field of the Invention 
   The present invention relates to an electrophotographic printer. More particularly, the present invention relates to a waste toner transfer apparatus to transfer waste toner generated during a printing process to a waste toner storage container and an electrophotographic printer using the same. 
   2. Description of the Related Art 
   In an image forming process of an electrophotographic printer, when an exposure unit scans light corresponding to image information onto a photoreceptor charged to a predetermined electric potential, an electrostatic latent image is formed on the photoreceptor. A developing unit supplies toner to the electrostatic latent image to form a toner image. Generally, four developing units containing cyan, magenta, yellow, and black toners are needed for a color electrostatic latent printer. The toner image is transferred to a recording medium directly, or via an intermediate medium, from the photoreceptor. While the recording medium passes through a fusing unit, the toner image is fused on the recording medium by heat and pressure. As a result of the above processes, a mono or color image is printed on the recording medium. 
   While a wet type electrophotographic printer uses a wet developer formed by dispersing toner powder in a liquid carrier, a dry type electrophotographic printer uses toner powder as a developer. In this case, waste toner remaining on a photoreceptor or on an intermediate transfer medium during the image forming process is removed therefrom and is collected in a storage container. The electrophotographic printer typically includes a waste toner transfer apparatus to transfer waste toner to the storage container. 
     FIG. 1  is a view illustrating a conventional waste toner transfer apparatus. Referring to  FIG. 1 , a cleaning apparatus  1  removes waste toner from a photoreceptor or an intermediate transfer medium (not shown). The waste toner removed by the cleaning apparatus  1  is transferred by a waste toner transfer apparatus  2  to a storage container (not shown). The waste toner enters a duct  4  through an inlet portion  3 . A shaft  5  rotated by a drive motor  6  is installed in the duct  4  and a conveying coil  7  is coupled to an end portion of the shaft  5 . The duct  4  and the storage container are connected by a pipe  8 . The conveying coil  7  is installed to extend through the inside of the pipe  8 . The waste toner entering the duct  4  through the inlet portion  3  is transferred by the conveying coil  7  to the storage container along the pipe  8 . The inlet portion  3  is generally formed to be inclined downward from the cleaning apparatus  1  toward the duct  4  so that the waste toner can slide and enter the duct  4  by gravity. 
   In the waste toner transfer apparatus  2  configured as above, although the waste toner is supposed to slide down by gravity along the inclined inlet portion  3 , waste toner particles sometimes coagulate into a waste toner lump due to an attraction force between the toner particles, and may adhere to an inner wall of the inlet portion  3 , especially the lower wall. When absorbing moisture in the air, the waste toner lump is further increased so that the inlet portion  3  is narrowed or clogged. When the inlet portion  3  is narrowed or clogged, waste toner accumulates in the cleaning apparatus  1 . Accordingly, the accumulated waste toner in the cleaning apparatus  1  may further harden in time. In this case, the waste toner may exert a load on the transfer unit  9  installed in the cleaning apparatus  1  to transfer the waste toner toward the inlet portion  3  so that the transfer unit  9  may be damaged. Further, the waste toner in the cleaning apparatus  1  exposed to the outside may contaminate the electrophotographic printer. 
   SUMMARY OF THE INVENTION 
   To solve the above and/or other problems, embodiments of the present invention provide a waste toner transfer apparatus which effectively transfers waste toner removed from an image holding body such as a photoreceptor or an intermediate transfer medium to a waste toner storage container, so that the waste toner does not accumulate during the transfer process, and an electrophotographic printer having the same. 
   According to an aspect of the present invention, there is provided a waste toner transfer apparatus in an electrophotographic printer to transfer waste toner removed by a cleaning unit from an image holding body where a toner image is temporarily held to a waste toner storage container. The waste toner transfer apparatus comprises a duct connecting the cleaning unit and the storage container, a transfer unit installed in the duct to transfer the waste toner to the storage container, and an agitation member installed in the duct to move therein and guide the waste toner from the cleaning unit to the transfer unit. 
   According to another aspect of the present invention, there is provided an electrophotographic printer including an image holding body for temporarily holding a toner image in an image forming process, a cleaning unit for removing waste toner remaining on the image holding body, a waste toner storage container, and a waster toner transfer apparatus for transferring the waste toner from the cleaning unit to the storage unit. The waste toner transfer apparatus comprises a duct connecting the cleaning unit and the storage container, a transfer unit installed in the duct to transfer the waste toner to the storage container, and an agitation member installed in the duct to move therein and guide the waste toner from the cleaning unit to the transfer unit. 
   The agitation member moves by being engaged with the transfer unit. The transfer unit comprises an auger having a shaft and a spiral wing formed on an outer circumference of the shaft, and one end of the agitation member contacts the auger so that the agitation member moves as the auger rotates. The agitation member is preferably formed of an elastically deformable material and elastically contacts the auger. The transfer unit further comprises a conveying coil having one end portion coupled to the shaft and a spiral coil shape extended to the storage container. The conveying coil rotates as the auger rotates. 
   The duct comprises a first duct extending downward from the cleaning unit, a second duct connected to the first duct, in which the auger is installed, and a third duct connecting the second duct and the storage container, in which the conveying coil is installed. The agitation member is preferably installed in the first duct. 
   In another embodiment, the transfer unit comprises a shaft which rotates, and a conveying coil inserted around one end portion of the shaft, having a spiral coil shape extending to the storage container, and rotated by the shaft. In this embodiment, the agitation member has one end contacting the conveying coil so that it moves as the conveying coil rotates. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other features and advantages of the present invention will become more apparent by describing in detail preferred embodiments thereof with reference to the attached drawings in which: 
       FIG. 1  is a view illustrating a conventional waste toner transfer apparatus; 
       FIG. 2  is a view illustrating a structure of an electrophotographic printer according to an embodiment of the present invention; 
       FIG. 3  is a view illustrating a structure of an electrophotographic printer according to another embodiment of the present invention; 
       FIG. 4  is a sectional view illustrating the waste toner transfer apparatus shown in  FIGS. 2 and 3 ; 
       FIG. 5  is a perspective view illustrating the waste toner transfer apparatus shown in  FIGS. 2 and 3 ; and 
       FIG. 6  is a perspective view illustrating the waste toner transfer apparatus according to yet another embodiment of the invention. 
   

   Throughout the drawings, it should be understood that like reference numbers refer to like features and structures. 
   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIG. 2 , an electrophotographic printer according to an embodiment of the present invention includes a photoreceptive drum  101 , an exposure unit  102 , a developing unit  103 , and a transfer belt  104 . 
   The photoreceptive drum  101 , as an example of a photoreceptor, has a photoconductive substance layer formed on the outer circumferential surface of a metal drum. A photoreceptive belt  112  as shown in  FIG. 3  can be used instead of the photoreceptive drum  101 . 
   The exposure unit  102  forms an electrostatic latent image by scanning light corresponding to image information onto the photoreceptor drum  101  charged to have a uniform electric potential. Generally, a laser scanning unit (LSU) using a laser diode as a light source is used as the exposure unit  102 . 
   Four developing units  103 C,  103 M,  103 Y, and  103 K contain solid powder toners of cyan (C), magenta (M), yellow (Y), and black (K) colors, respectively, and provide the toners to the electrostatic latent image formed on the photoreceptive drum  101  to form toner images. 
   The transfer belt  104  is an example of an intermediate transfer medium which transfers the toner image received from the photoreceptor to a recording medium S. A transfer drum  113  as shown in  FIG. 3  can be used instead of the transfer belt  104 . The toner images, sequentially formed on the photoreceptive drum  101 , for the cyan (C), magenta (M), yellow (Y), and black (K) colors are transferred to the transfer belt  104  to be overlapped so that a color toner image is formed. Preferably, the running linear velocity of the transfer belt  104  is the same as the linear velocity of the photoreceptive drum  101 . The length of the transfer belt  104  must be the same as or at least longer than the length of the recording medium S where the color toner image is finally transferred. 
   The transfer roller  105  is installed to face the transfer belt  104 . The transfer roller  105  is separated from the transfer belt  104  while the color toner image is transferred to the transfer belt  104 . When the color toner image is completely transferred to the transfer belt  104 , the transfer roller  105  contacts the transfer belt  104  with a predetermined pressure to transfer the color toner image to the recording medium S. When the recording medium S to which the toner image is transferred passes through a fusing unit  106 , the toner image is fused on the recording medium S by heat and pressure. A charger  107  initially charges the photoreceptive drum  101  to a uniform electric potential. A discharger  108  discharges any electrical charges remaining on the photoreceptive drum  101  after the image has been transferred. 
   The image forming process performed by the electrophotographic printer having the above-described structure is described below. 
   Color image information includes information on cyan (C), magenta (M), yellow (Y), and black (K) colors. In the present preferred embodiment, the color toner images corresponding to the cyan (C), magenta (M), yellow (Y), and black (K) colors are sequentially overlapped on the transfer belt  104  and the overlapped image is transferred to the recording medium S. Then, the transferred image is fused on the recording medium S so that a color image is formed. 
   When a light signal corresponding to the image information on cyan (C) color is scanned by the exposure unit  102  onto the photoreceptive drum  101  that has previously been charged to a uniform electric potential, resistance of a portion of the drum surface where the light is scanned decreases and as a result charges adhering to the external circumferential surface of the photoreceptive drum  101  dissipate. As a result, a difference in electric potential is generated between the scanned portion and the non-scanned portion of the photoreceptive drum  101  so that an electrostatic latent image is formed on the outer circumferential surface of the photoreceptive drum  101 . When the electrostatic latent image approaches the developing unit  103 C containing cyan (C) toner as the photoreceptive drum  101  rotates, the cyan (C) toner adheres to the electrostatic latent image so that a cyan toner image is formed. When the cyan toner image approaches the transfer belt  104  by the rotation of the transfer belt  104 , the cyan toner image is transferred to the transfer belt  104  by the difference in electric potential with the transfer belt  104  and/or a contact pressure. When the cyan toner image is completely transferred to the transfer belt  104 , the toner images corresponding to the magenta (M), yellow (Y), and black (K) colors are sequentially transferred to the transfer belt  104 , in the same process, and overlapped thereon to form a color toner image. When the recording medium S passes between the transfer belt  104  and the transfer roller  105 , the color toner image is transferred to the recording medium S. Next, the color toner image is fused by the fusing unit  106  onto the recording medium S by heat and pressure and the recording medium S is ejected, completing the image forming process. 
   The photoreceptive drum  101  and the transfer belt  104  are image holding bodies which temporarily hold a toner image before the toner image is transferred to the recording medium S. Some waste toner remains on the photoreceptive drum  101  and the transfer belt  104  in the process of transferring the toner image to the recording medium S via the photoreceptive drum  101  and the transfer belt  104 . The waste toner remaining on the image holding bodies is preferably removed for the next printing. The removed waste toner is held in a storage container  200  and is then disposed of. In some cases, some waste toner reenters the developing unit to be reused. However, for a color image forming apparatus, since toner having different colors are mixed, generally, the waste toner cannot be reused. 
   Referring to  FIG. 2 , waste toner from the photoreceptive drum  101  is removed by a cleaning unit  120 . The cleaning unit  120  includes a housing  121 , a blade  122  contacting the photoreceptive drum  101  to squeegee the waste toner, and an auger  123  to transfer the waste toner toward an outlet  124  of  FIG. 4  provided at one side end portion of the housing  121 . Also, waste toner from the transfer belt  104  is removed by a cleaning unit  130 . The cleaning unit  130  preferably has the same structure as that of the cleaning unit  120  for the photoreceptive drum  101 . 
   In the storage container  200 , an inlet  201  of  FIG. 4 , through which waste toner enters, is preferably disposed near the top of the container  200  to effectively hold the waste toner. In the embodiment of the invention shown in  FIG. 2 , where the transfer belt  104  is disposed above the photoreceptive drum  101 , the waste toner removed from the transfer belt  104  by the cleaning unit  130  is transferred to the storage container  200  directly through the inlet  201  from the cleaning unit  130 . However, the waste toner removed from the photoreceptive drum  101  by the cleaning unit  120  is transferred to the storage container  200  by a waste toner transfer apparatus  300  to overcome a difference in height between the cleaning unit  120  and the inlet  201  of the storage container  200 . 
     FIG. 3  shows an electrophotographic printer according to another embodiment of the present invention. Referring to  FIG. 3 , a photoreceptive belt  112  is provided parallel to a transfer drum  113 . The cleaning units  120  and  130  to remove waste toner from the photoreceptive belt  112  and the transfer drum  113  are provided. The electrophotographic printer having the above structure needs two waste toner transfer apparatuses  300  to transfer waste toner from the respective cleaning units  120  and  130  to the storage container  200 . 
     FIGS. 4 and 5  are a sectional view and a perspective view, respectively, illustrating the waste toner transfer apparatus shown in  FIGS. 2 and 3 . Referring to  FIGS. 4 and 5 , a duct  310  is connected to the outlet  124  of the cleaning unit  120  and a transfer unit  350  is installed inside the duct  310 . The duct  310  includes first through third ducts  301 ,  302  and  303 , in the presently preferred embodiment. Thus, a waste toner transfer route is formed from the cleaning unit  120  to the storage container  200 , via the first duct  301 , the second duct  302  and the third duct  303 . 
   The transfer unit  350  includes an auger  320 . The auger  320  has a shaft  321  and a wing  322  having a spiral shape formed on the outer circumference of the shaft  321 . A gear  330  is coupled to the shaft  321 . A drive motor  360  has a rotation shaft to which a worm gear  361  connected to the gear  330  is coupled. The drive motor  360  rotates the auger  320 . A spiral shaped conveying coil  340  may further be included in the transfer unit  350 . One end portion  341  of the conveying coil  340  is coupled to the shaft  321  of the auger  320  and the other end portion  342  is extended to the storage container  200 . The conveying coil  340  is rotated as the auger  320  rotates. 
   The first duct  301  is preferably installed to be inclined downward from the cleaning unit  120  toward the second duct  302  so that the waste toner can enter the second duct  302  by gravity. The auger  320  is installed in the second duct  302  and transfers the waste toner entering through the first duct  301  to the third duct  320 . The third duct  303  preferably has a flexible circular pipe shape so as to be easily connected between the second duct  302  and the storage container  200 . The conveying coil  340  is provided in the third duct  303 . 
   An agitation member  370  is installed in the first duct  301 . A first end portion  371  of the agitation member  370  is disposed close to an inlet side of the first duct  301  and a second end portion  372  contacts the auger  320 . Thus, the agitation member  370  is inclined downward from the first end portion  371  toward the second end portion  372 . Furthermore, the agitation member is preferably formed in a channel shape to help guide waster toner from the inlet side of the first duct  301  to the second end portion  372 . The second end portion  372  of the agitation member  370  preferably has a soft curved shape so as to gently contact the shaft  321  and/or the wing  322  and move up and down as the auger  320  rotates. The agitation member  370  is preferably, but not necessarily, an elastic member. In a preferred embodiment, the agitation member  370  is made of a thin steel plate. However, it should be understood that a wide variety of materials could be used in the construction of an agitation member  370 , including plastic. In this case, the first end portion  371  of the agitation member  370  is fixed to the inlet side of the first duct  301  and the second end portion  372  elastically (resiliently) contacts the auger  320 . When the agitation member  370  is a non-elastic member, although not shown in the drawings, the first end portion  371  of the agitation member  370  is preferably installed at the first duct  301  so that it is capable of pivoting. Preferably, the agitation member  370  moves by being engaged with the transfer unit  350  as in the illustrated embodiment. However, an additional drive means (not shown) may further be included to move the agitation member  370 . 
   The operation and effect of the waste toner transfer apparatus  300  is described below with reference to  FIGS. 2 through 5 . 
   The waste toner removed from the photoreceptive drum  101  by the cleaning apparatus  120  enters in the first duct  301 . The waste toner falls on the agitation member  370  from the cleaning unit  120  by gravity and slides along the agitation member  370  which is inclined, to enter the second duct  302 . When the drive motor  360  rotates, the auger  320  in the second duct  302  rotates and the conveying coil  340  in the third duct  303  also rotates. The waste toner in the second duct  302  enters the third duct  303  by being pushed by the spiral wing  322  of the auger  320  and is transferred to the storage container  200  along the conveying coil  340 . 
   Part of the waste toner falling on the agitation member  370  does not enter in the second duct  302  due to an attraction force between the toner particles and tends to be accumulated on the agitation member  370 . Accordingly, the first duct  301  may clog in time. To prevent this, in the waste toner transfer apparatus  300  according to an embodiment of the present invention, the agitation member  370  moves by being engaged with the transfer unit  350 . As shown in  FIG. 5 , the second end portion  372  of the agitation member  370  is in contact with the auger  320 . For the sake of explanation, it is assumed that the second end portion  372  initially contacts the shaft  321 . When the auger  320  rotates, the wing  322  rotates while advancing in a direction A shown in  FIG. 5 . The second end portion  372  ascends as it contacts the wing  322  and then descends and contacts the shaft  321  as the auger  320  continuously rotates. Since the agitation member  370  moves up and down in a direction B shown in  FIG. 5 , the waste toner falling on the agitation member  370  does not accumulate and naturally enters the second duct  302 . 
   In this embodiment, since the agitation member  370  acts as the channel to guide the waste toner from the cleaning unit  120  to the transfer unit  350 , the waste toner does not accumulate in the first duct  301 . As the waste toner slides down from the cleaning unit  120  to the transfer unit  350  through the agitation member  370  by gravity, moving the agitation member  370  in a normal direction to the direction of an axis of the transfer unit  350  can guide the waste toner to the transfer unit  350  more efficiently than moving the agitation member  370  in the same direction as the axis of the transfer unit  350 . 
     FIG. 6  shows a waste toner transfer apparatus according to another preferred embodiment of the present invention. Referring to  FIG. 6 , a transfer unit  390  includes a shaft  321  installed in the second duct  302  to rotate and the conveying coil  340  inserted around the shaft  321  and extending toward the third duct  303 . The conveying coil  340  is inserted further along the shaft  321  so that it can contact the end portion  372  of the agitation member  370 . Thus, as the conveying coil  340  rotates, the agitation member  370  in contact with the spiral of the conveying coil  340  moves up and down. 
   As described above, in the electrophotographic printer according to embodiments of the present invention, since the agitation member is provided, the waste toner effectively enters in the transfer unit by gravity and the agitation of the agitation member. 
   While this invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. For example, embodiments of the present invention could be employed in devices that use optical exposure units rather than laser scanning units to form a latent image on the photoreceptive drum or belt. Also, a non-photoreceptive drum or belt could also be used in a device utilizing an electrostatic print head, in which a latent image is formed onto an insulating surface of a drum or belt by depositing charge directly onto the insulating surface of the drum or belt. Devices that use a two-component solid toner could benefit from using a toner transfer device according to an embodiment of the present invention. Also, while multi-color printing devices have been described herein, those of ordinary skill in the art will readily appreciate that the concepts described herein can be applied to single color image forming devices as well.