Patent Publication Number: US-2005117945-A1

Title: Waste toner transferring apparatus and electrophotographic printer adopting the same

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
      This application claims the priority of Korean Patent Application No. 2003-84970, filed on Nov. 27, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to an electrophotographic printer. More particularly, the present invention relates to an electrophotographic printer including a waste toner transferring apparatus which transfers waste toner, which is generated during printing, to a container for containing the waste toner.  
      2. Description of the Related Art  
      In an image forming process that takes place in an electrophotographic printer, light corresponding to image information is applied from exposure equipment to a photoreceptor that is charged to have a uniform potential to form an electrostatic latent image on the photoreceptor. A developer supplies toner to the electrostatic latent image to form a toner image. Typical color electrophotographic printers use four developers containing cyan (C) toner, magenta (M) toner, yellow (Y) toner, and black (K) toner, respectively. The toner image formed on the photoreceptor is transferred directly to a recording medium (such as paper) or transferred to the same via an intermediate transfer medium. When the recording medium passes by a fuser, the toner image is fused to the recording medium by heat and pressure. Accordingly, a mono-color image or a color image is printed on the recording medium.  
      Dry-type electrophotographic printers use toner powder. Waste toner remaining on the photoreceptor or the intermediate transfer medium during image formation must be removed. The removed waste toner is typically contained in a container. Electrophotographic printers typically include a waste toner transferring apparatus for transferring waste toner to the container.  
       FIG. 1  is a schematic view of a conventional waste toner transferring apparatus. Waste toner removed from a photoreceptor or an intermediate transfer medium by a cleaning device (not shown) enters into a duct  2  via an inlet  1 . A shaft  4  is installed in the duct  2  and rotated by a driving motor  3 . A conveying coil  5  is wound around an end of the shaft  4 . Reference numeral  6  denotes a pipe via which the duct  2  is connected to a container (not shown). The conveying coil  5  extends to the inside of the pipe  6 . Through the use of the conveying coil  5 , the waste toner introduced into the duct  2  via the inlet  1  is transferred to the container via the pipe  6 .  
      If the waste toner is left in the duct  2  of the conventional waste toner transferring apparatus for a long period of time, fine particles of the waste toner may clump due to their affinity and become attached to an outer circumference of the shaft  4 . In particular, if the waste toner is left for a long period of time in an environment of high temperature and high humidity, the waste toner becomes solid. As shown in  FIG. 2 , when the solid waste toner attached to the shaft  4  fills a space B defined by the outer circumference of the shaft  4  and the conveying coil  5 , the solid waste toner is not detached from the space B even when the shaft  4  and the conveying coil  5  rotate. Then, the waste toner piles up in the cleaning device. If the waste toner continues to pile up, the waste toner may enter into the image forming apparatus.  
     SUMMARY OF THE INVENTION  
      The present invention provides an improved waste toner transferring apparatus which can effectively transfer waste toner removed from an image receiver, such as a photoreceptor, an intermediate transfer medium, or the like, to a container without the waste toner piling up, and an electrophotographic printer including the waste toner transferring apparatus.  
      According to an aspect of the present invention, there is provided a waste toner transferring apparatus in an electrophotographic printer, which transfers waste toner removed from image receivers which temporarily receive toner images, to a container. The apparatus comprises an auger, which includes a shaft and spiral wings formed on an outer circumference of the shaft and which transfers the waste toner while rotating, and elastic brushes, which are installed so as to be placed in grooves between the spiral wings. As the auger rotates, the elastic brushes elastically interfere with the spiral wings so that the waste toner does not remain in the grooves.  
      According to another aspect of the present invention, there is provided an electrophotographic printer comprising image receivers which temporarily receive toner images during image formation, a cleaning device which removes waste toner residuals from the image receivers, a container which holds the removed waste toner, and a waste toner transferring apparatus which transfers the waste toner from the cleaning device to the container. The used toner transferring apparatus includes an auger which includes a shaft and spiral wings formed on an outer circumference of the shaft and transfers the waste toner while rotating, and elastic brushes, which are installed so as to be placed in grooves between the spiral wings. As the auger rotates, the elastic brushes elastically interfere with the spiral wings so that the waste toner does not remain within the grooves.  
      The elastic brushes preferably elastically contact the outer circumference of the shaft. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:  
       FIG. 1  is a schematic view of a conventional waste toner transferring apparatus;  
       FIG. 2  is a detailed view of portion A of  FIG. 1 ;  
       FIG. 3  is a schematic view of an electrophotographic printer according to an embodiment of the present invention;  
       FIG. 4  is a vertical cross-section of a waste toner transferring apparatus according to an embodiment of the present invention;  
       FIG. 5  is a horizontal cross-section of the waste toner transferring apparatus of  FIG. 4 ; and  
       FIG. 6  is a cross-section taken along line II-II of  FIG. 5 . 
    
    
      Throughout the drawings, life reference numbers are used to depict like features and structures.  
     DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT  
      Referring to  FIG. 3 , an electrophotographic printer according to an embodiment of the present invention includes a photoconductive drum  101 , an exposure unit  102 , a developer  103 , and a transfer belt  104 .  
      The photoconductive drum  101 , which is an example of a photoreceptor, is preferably manufactured by forming a photoconductive material layer on an outer circumference of a metal drum. The photoconductive drum  101  may be replaced by a belt-type photoreceptor (not shown), as will be understood by those of ordinary skill in the art.  
      The exposure unit  102  projects light corresponding to image information onto the photoconductive drum  101 , which is charged to have a constant potential, thereby forming an electrostatic latent image on the photoconductive drum  101 . A laser scanning unit (LSU), which generally uses a laser diode as a light source, is used as the exposure unit  102 .  
      The developer  103  includes four developers C, M, Y, and K which contain cyan (C) toner powder, magenta (M) toner powder, yellow (Y) toner powder, and black (K) toner powder, respectively. The developers C, M, Y, and K supply the toner to the electrostatic latent image formed on the photoconductive drum  101 , thereby forming C, M, Y, and K toner images.  
      The transfer belt  104  is an example of an intermediate transfer medium which receives the toner images from the photoconductive drum  101  and transfers them to a recording medium S. Although not shown in  FIG. 3 , the transfer belt  104  may be replaced by a transfer drum. The C, M, Y, and K toner images sequentially formed on the photoconductive drum  101  are sequentially transferred to the transfer belt  104  and overlapped thereon to form a color toner image. Preferably, the linear velocity of the transfer belt  104  is equal to that of a rotation of the photoconductive drum  101 . The length of the transfer belt  104  must be equal to or greater than the recording medium S, which is a final destination of the color toner image.  
      Reference numeral  105  denotes a transfer roller which faces the transfer belt  104 . While the color toner image is being transferred to the transfer belt  104 , the transfer roller  105  is separated from the transfer belt  104 . After the color toner image is completely transferred to the transfer belt  104 , the transfer roller  105  is pressed against the transfer belt  104  and transfers the color toner image to the recording medium S. Reference numeral  106  denotes a fuser. When the recording medium S to which the toner image is transferred passes through the fuser  106 , the toner image is fused to the recording medium S by heat and pressure. Reference numeral  107  denotes a charger which charges the photoconductive drum  101  so that the photoconductive drum  101  has a uniform potential. Reference numeral  108  denotes a discharger which removes charges from the charged photoconductive drum  101 .  
      If the exposure unit  102  applies an optical signal corresponding to information about a cyan (C) component of an image to the photoconductive drum  101 , which is charged to a uniform potential, a resistance in a portion of the photoconductive drum  101  to which light is applied decreases, while charges are detached from an outer circumference of the photoconductive drum  101 . Hence, a potential difference is generated between the light-applied portion of the photoconductive drum  101  and the remaining portion. Consequently, an electrostatic latent image is formed on the outer circumference of the photoconductive drum  101 . When the electrostatic latent image approaches the developer C due to the rotation of the photoconductive drum  101 , the C toner contained in the developer C is attached to the electrostatic latent image, thereby forming a C toner image. When the C toner image approaches the transfer belt  104  due to the rotation of the photoconductive drum  101 , the C toner image is transferred to the transfer belt  104  by a potential difference between the photoconductive drum  101  and the transfer belt  104  and/or a contact pressure between them. After the C toner image is completely transferred to the transfer belt  104 , the M, Y, and K toner images are sequentially transferred to the transfer belt  104  in the above-described manner and overlap one another on the transfer belt  104 , thereby forming a color toner image. While 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. Subsequently, the color toner image is fused to the recording medium S by the heat and pressure of the fuser  106 , thereby completing color image formation.  
      The photoconductive drum  101  and the transfer belt  104  are image receivers which temporarily receive toner images before the toner images are transferred to the recording medium S. While the toner images are being transferred to the photoconductive drum  101 , the transfer belt  104 , and the recording medium S, some toner remains on the photoconductive drum  101  or the transfer belt  104 . To perform further printing, it is preferable to remove the waste toner from the image receivers. The removed waste toner is contained in a container  200  and discarded later. Some of the waste toner may re-enter the developer  103  and be recycled. However, in general color image forming apparatuses, different color toners are mixed together and thus cannot be recycled.  
      Referring to  FIG. 3 , in a cleaning device  120  for removing waste toner from the photoconductive drum  101 , waste toner removed from the photoconductive drum  101  by a blade  122  is temporarily contained within a housing  121 . A cleaning device  130  for removing waste toner remaining in the transfer belt  104  may have a similar structure as the cleaning device  120 . Reference numeral  200  denotes a container which contains waste toner. A waste toner transferring apparatus  300  transfers the waste toner that has been removed from the photoconductive drum  101  by the cleaning device  120  to the container  200 . The cleaning device  130  may be connected directly to the container  200 . Although not shown in  FIG. 3 , another waste toner transferring apparatus may be further included to transfer waste toner from the cleaning device  130  to the container  200 .  
       FIGS. 4 and 5  are vertical and horizontal cross-sections, respectively, of the waste toner transferring apparatus  300 .  FIG. 6  is a cross-section taken along line II-II of  FIG. 5 .  
      Referring to  FIGS. 4 and 5 , waste toner is introduced into a duct  310  via an inlet  301 . The inlet  301  is connected to an outlet  124  of the cleaning device  120 . An auger  320  is installed within the duct  310 . The duct  310  is connected to the container  200  via a pipe  340 .  
      The auger  320  includes a shaft  321  and a spiral wing  322  formed on an outer circumference of the shaft  321 . A gear  330  is combined with the shaft  321 . Reference numeral  360  denotes a driving motor to which a worm gear  361  is coupled. The worm gear  361  is connected to the gear  330 . The driving motor  360  rotates the auger  320 . A conveying coil  350  may be installed within the pipe  340 . One end of the conveying coil  350  is coupled to the shaft  321  of the auger  320 , and the other end extends to the container  200 . The conveying coil  350  rotates with a rotation of the auger  320 .  
      The waste toner removed from the photoconductive drum  101  by the cleaning device  120  enters into the duct  310  via the inlet  301 . The waste toner is collected in grooves  323 , each of which is formed between adjacent spiral wings  322  of the auger  320 . When the driving motor  360  rotates, the auger  320  in the duct  310  is rotated, and the conveying coil  350  connected to the auger  320  is also rotated. The waste toner collected in the grooves  323  is introduced into the pipe  340  by the thrust of the spiral wings  322 . Also, the introduced waste toner is transferred to the container  200  via the pipe  340  by the thrust of the conveying coil  350 .  
      While the image forming apparatus is not performing printing, the auger  320  does not rotate. Hence, the waste toner collected in the grooves  323  may be left for a long period of time. Since the waste toner is a fine powder, powder particles may combine together due to their affinity. If the combined waste toner absorbs humidity, it becomes solid and may become attached to the shaft  321  or the wings  322 . When the auger  320  transfers the solid waste toner collected in the grooves  323  to the pipe  340 , the transfer efficiency of the auger  320  is reduced. Also, even if the waste toner powder does not become solid, it may not be transferred to the pipe  340  while spinning around over the grooves  323 .  
      As shown in  FIGS. 5 and 6 , the waste toner transferring apparatus  300  includes elastic brushes  370  on the grooves  323  in order to prevent the incomplete transfer of waste toner. One end of each of the elastic brushes  370  is fixed to the duct  310 , and the other end is located within each of the grooves  323 . Preferably, the elastic brushes  370  extend so as to elastically contact the outer circumference of the shaft  321 . Accordingly, as the driving motor  360  rotates, the elastic brushes  370  interfere with the spiral wings  322  and elastically move in a direction indicated by an arrow C of  FIG. 5 . By moving as described above, the elastic brushes  370  loosen the waste toner collected in the grooves  323  and prevent the waste toner from becoming stuck in the grooves  323 . Hence, no waste toner remains on the outer circumference of the shaft  321  and the surfaces of the spiral wings  322 . Also, waste toner attached to the outer circumference of the shaft  321  or the surfaces of the spiral wings  322  for a long period of time can be removed to prevent the grooves  323  from being blocked by the solid waste toner.  
      An electrophotographic printer according to an embodiment of the present invention as described above can prevent waste toner from piling up and solidifying in grooves between the spiral wings, by including elastic brushes. Consequently, the waste toner transfer efficiency of an auger can be increased.  
      While the present invention has been particularly shown and described with reference to an exemplary embodiment thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.