Abstract:
A roller cleaning apparatus of a liquid electrophotographic printer cleans a circumferential surface of a roller where a film is formed due to contact with a photoreceptor medium. The apparatus includes an abrasion member installed to be in contact with the roller for abrading the film using friction. Thus, contamination of the roller can be prevented.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a roller cleaning apparatus of a liquid electrophotographic printer, and more particularly, to a roller cleaning apparatus of a liquid electrophotographic printer for removing a developer film formed on a roller rotating in contact with a photoreceptor medium. 
     2. Description of the Related Art 
     In general, a liquid electrophotographic printer develops an electrostatic latent image formed on a photoreceptor medium such as a photoreceptor web with developer of a predetermined color and transfers the developed image to a print paper so that a desired image is printed. 
     The liquid electrophotographic printer, as shown in FIG. 1, includes a developing unit  20  for developing an electrostatic latent image formed on a photoreceptor web  10  with developer which is a mixture of powdered toner having a predetermined color, liquid carrier and other additives in a predetermined ratio, a drying unit  30  having a drying roller  31  for drying the developed photoreceptor web  10  and a heating roller  32 , a transfer unit  40  for transferring the image on a surface of the photoreceptor web  10  via a transfer roller  41  and a fixation roller  42  to a print paper S. 
     The drying roller  31  absorbs the liquid carrier of the developer developed on the surface of the photoreceptor web  10 . However, as the drying roller  31  contacts the photoreceptor web  10 , not only carrier but also a small amount of toner is actually absorbed. Thus, with increased use of the drying roller  31 , a developer contamination film can form on the outer circumferential surface of the drying roller  31 . 
     Also, the transfer unit  40  transfers a toner image on the photoreceptor web  10  to the transfer roller  41  utilizing the difference in surface energy and then prints the image by transferring the toner image on the transfer roller  41  to a print paper S pressed by the fixation roller  42 . However, in doing so, part of the toner image on the transfer roller  41  may be fixed on the surface of the transfer roller  41 , forming a contaminated film. Also, as the developer is sticky, a paper jam can occur due to the print paper S adhering to the surface of the transfer roller  41  as the print paper S moves through the transfer unit  40 . 
     Therefore, there is a need for a cleaning apparatus for cleaning the outer circumferential surfaces of the drying roller  31  and the transfer roller  41  where a developer contamination film can be easily formed, as they closely contact the photoreceptor web  10  where a toner image is developed. 
     SUMMARY OF THE INVENTION 
     To meet the above needs, it is an objective of the present invention to provide a roller cleaning apparatus of a liquid electrophotographic printer having an improved structure to clean the outer circumferential surface of a roller such as a transfer roller or drying roller contacting a photoreceptor medium so that a developer contamination film can be removed. 
     Accordingly, to achieve the above objective, there is provided a roller cleaning apparatus of a liquid electrophotographic printer for cleaning a circumferential surface of a roller where a film is formed due to contact with a photoreceptor medium. The apparatus comprises an abrasion member installed to be in contact with the roller for abrading the film using friction. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above objective and advantages of the present invention will become more apparent by describing in detail a preferred embodiment thereof with reference to the attached drawings in which: 
     FIG. 1 is a view showing the structure of a conventional liquid electrophotographic printer; 
     FIG. 2 is a view showing a roller cleaning apparatus according to the first preferred embodiment of the present invention; 
     FIG. 3 is a view showing a roller cleaning apparatus according to the second preferred embodiment of the present invention; 
     FIG. 4 is a view showing a roller cleaning apparatus according to the third preferred embodiment of the present invention; 
     FIG. 5 is a view showing a roller cleaning apparatus according to the fourth preferred embodiment of the present invention; 
     FIG. 6 is a view showing a roller cleaning apparatus according to the fifth preferred embodiment of the present invention; and 
     FIG. 7 is a view showing a roller cleaning apparatus according to the sixth preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Of the transfer roller and the drying roller rotating in contact with a photoreceptor web, the transfer roller is more vulnerable to contamination by developer. Thus, the first, second and third preferred embodiments according to the present invention described below will concentrate on the transfer roller. 
     FIG. 2 shows a transfer roller cleaning apparatus of a liquid electrophotographic printer according to the first preferred embodiment of the present invention. 
     Referring to the drawing, a photoreceptor web  100  circulates around a developing unit  200 , a drying unit  300  and a transfer unit  400 . The developing unit  200  develops an image on the photoreceptor web  100  using a predetermined developer. The drying unit  300  dries the photoreceptor web  100  with a drying roller  310  and a heating roller  320 . The transfer unit  400  transfers a toner image transferred onto the transfer roller  410  to a print paper S. Reference numeral  420  denotes a fixation roller. A dressing roller  500 , which is rotated by a driving motor  510 , is in close contact with the transfer roller  410 . The dressing roller  500  is provided with foamed rubber mixed with whetstone powder of 10-40 wt %. Thus, the surface of the dressing roller  500  is formed to be rougher than a general rubber. Preferably, the size of whetstone powder particles is in the range between 220-1000 mesh. This is because, when the particles are too fine, the effect of cleaning is lowered whereas when the particles are too rough the transfer roller  410  may become damaged. Also, the dressing roller  500  rotates at a speed different from that of the transfer roller  410 . That is, the speed ratio of the dressing roller  500  and the transfer roller  410  is preferably set in a range from 0.1:1 to 2:1, excluding 1:1. Thus, the dressing roller  500  abrades the surface of the transfer roller  410  with a frictional force caused by the different rotational speeds between the two rollers  410  and  500 . Therefore, a contaminated film that forms on the outer circumferential surface of the transfer roller  410  can be removed. 
     Although the additional driving motor  510  is used to rotate the dressing roller  500  in the above-described embodiment, a driving source (not shown) for driving the photoreceptor web  100  can be used to rotate the dressing roller  500  and the transfer roller  410  at different speeds so as to set the above speed ratio. 
     FIG. 3 shows a roller cleaning apparatus of a liquid electrophotographic printer according to the second preferred embodiment of the present invention. The structural elements having the same reference numerals as those described with reference to FIG. 2 have the same functions. 
     In the present embodiment, it is a characteristic feature that an abrasion blade  600  is used to contact the transfer roller  410  instead of the dressing roller  500  of the first preferred embodiment. The abrasion blade  600  is formed of a mixture of foamed rubber and whetstone powder of 10-40 wt %. The whetstone powder having a particle size of 220-1000 mesh is selected. The abrasion blade  600  removes the contaminated film formed on the outer circumferential surface of the transfer roller  410  using a frictional force. Here, the transfer roller  410 , together with the fixation roller  420 , preferably descends to move into contact with the photoreceptor web  100  and ascends to move out of contact with the photoreceptor web  100 . Thus, to make the abrasion blade  600  contact the transfer roller  410  only when the transfer roller  410  closely contacts the photoreceptor web  100 , the abrasion blade  600  can be fixed to a frame (not shown) different from a frame (not shown) where the transfer roller  410  is installed. Also, the abrasion blade  600  can be fixed to a frame (not shown) by which the transfer roller  410  is supported so that the abrasion blade  600  can closely contact the transfer roller  410  while ascending or descending together with the transfer roller  410 . 
     FIG. 4 shows the third preferred embodiment of the present invention. In the present preferred embodiment, a sandpaper  651  installed on an elastic piece  650  abrades the outer circumferential surface of the transfer roller  410  while contacting the transfer roller  410 , instead of the abrasion blade  600  of the previous preferred embodiment. Here, the size of particles of the sandpaper  651  is preferably between 15 μm-40 μm. 
     The cleaning apparatus according to a preferred embodiment of the present invention, as shown in FIGS. 5 through 7, can be adopted to the drying roller  310  of the drying unit  300 . The drying roller  310  dries a toner image formed on the photoreceptor web  100  by the developing unit  200 , thereby making the toner image suitable for printing. The drying roller  310 , while contacting the photoreceptor web  100 , absorbs remaining carrier included in the toner image into a surface of the drying roller  310 . A dressing roller  700  rotated by a driving motor  710  at a speed different from that of the drying roller  310 , as shown in FIG. 5, or an abrasion blade  800  having one end thereof contacting the outer circumferential surface of the drying roller  310 , as shown in FIG. 6, is installed to abrade and remove the contaminated film adhering to the surface of the drying roller  310 . Here, the dressing roller  700  or the abrasion blade  800  is preferably formed of foamed rubber mixed with whetstone powder having a particle size of 220-1000 mesh at 10-40 wt %. Also, as shown in FIG. 7, a sandpaper  851  attached to an elastic piece  850  can abrade the drying roller  310 . 
     As described above, in the roller cleaning apparatus of a liquid electrophotographic printer according to the present invention, since a developer contamination film formed due to contact with the photoreceptor web is abraded and removed, contamination of the roller can be prevented.