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.

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 Figure 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.

JP 09 114269 discloses an image forming device having a grinding roller.

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 contaminated developer 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 utilizing the difference in surface energy and then prints the image by transferring the toner image on the transfer roller 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 wherein the print paper adheres to the surface of the transfer roller 41.

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 film can be easily formed, as they closely contact the photoreceptor web 10 where a toner image is developed.

To meet the above needs, it is an aim 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 contaminated film can be removed.

According to a first aspect of the present invention there is provided a roller cleaning apparatus for use in a liquid electrophotographic printer, said apparatus for cleaning a circumferential surface of a roller where a film is formed due to contact with a photoreceptor medium, said apparatus comprising an abrasion member arranged operatively to be in contact with said roller for abrading said film using friction; characterized by: the abrasion member being formed by mixing foamed rubber with whetstone powder of 10-40wt%.

Preferably, said abrasion member comprises a dressing roller, arranged for rotation at a speed different from that of said roller to be cleaned, for abrading an outer circumferential surface of said roller using friction due to the different rotational speeds.

Preferably, said abrasion member is an abrasion blade arranged operatively to closely contact the outer circumferential surface of said roller.

Preferably, said whetstone powder has the particle size of 220-1000 mesh.

Preferably, said roller is a transfer roller for printing an image developed on said photoreceptor medium on a print paper.

Preferably, said roller is a drying roller for drying the image developed on said photoreceptor medium.

According to a second aspect of the present invention there is provided a roller cleaning apparatus for use in a liquid electrophotographic printer, said apparatus for cleaning a circumferential surface of a roller where a film is formed due to contact with a photoreceptor medium, said apparatus comprising an abrasion member arranged operatively to be in contact with said roller for abrading said film using friction; characterized by: the abrasion member comprising: a sandpaper arranged operatively to contact the outer circumferential surface of said roller; and an elastic piece for elastically biasing said sandpaper toward said roller.

Preferably, said roller is a transfer roller for printing an image developed on said photoreceptor medium on a print paper.

Preferably, said roller is a drying roller for drying the image developed on said photoreceptor medium.

For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings in which:

• Figure 1 is a view showing the structure of a conventional liquid electrophotographic printer;
• Figure 2 is a view showing a roller cleaning apparatus according to the first preferred embodiment of the present invention;
• Figure 3 is a view showing a roller cleaning apparatus according to the second preferred embodiment of the present invention;
• Figure 4 is a view showing a roller cleaning apparatus according to the third preferred embodiment of the present invention;
• Figure 5 is a view showing a roller cleaning apparatus according to the fourth preferred embodiment of the present invention;
• Figure 6 is a view showing a roller cleaning apparatus according to the fifth preferred embodiment of the present invention; and
• Figure 7 is a view showing a roller cleaning apparatus according to the sixth preferred embodiment of the present 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 of the present invention described below will concentrate on the transfer roller.

Figure 2 shows a first preferred embodiment of a transfer roller cleaning apparatus for use in a liquid electrophotographic printer.

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, preferably in the range 10-40wt%. 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 between 0.1:1-2:2, 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.

Figure 3 shows a roller cleaning apparatus of a liquid electrophotographic printer according to a second preferred embodiment of the present invention. The structural elements having the same reference numerals as those described with reference to Figure 2 have the same functions.

In the second embodiment, 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 again preferably in the range 10-40wt%. The whetstone powder having the particle size of 220-1000 mesh is preferred. 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 preferably contacts or is separated from the photoreceptor web 100 while ascending or descending in a direction perpendicular to the drawing. 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. Here, the abrasion blade 600 is moveable with respect to the transfer roller 410, or vice versa. Alternatively, 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, and thereby remains stationary with respect to the transfer roller 410.

Figure 4 shows a third preferred embodiment of the present invention. In the third preferred embodiment, an abrasive member such as sandpaper 651 is installed at (i.e. supported by) an elastic piece 650 (a resilient biasing member) for abrading 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 figures 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 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 Figure 5, or an abrasion blade 800 having one end thereof contacting the outer circumferential surface of the drying roller 310, as shown in Figure 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 the particle size of 220-1000 mesh at 10-40wt%. Also, as shown in Figure 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 film formed due to contact with the photoreceptor web is abraded and removed, contamination of the roller can be prevented.