Electrophotography – Cleaning of imaging surface – Fibrous brush
Reexamination Certificate
2003-01-08
2004-06-22
Beatty, Robert (Department: 2852)
Electrophotography
Cleaning of imaging surface
Fibrous brush
Reexamination Certificate
active
06754466
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to electrostatographic copiers or printers and, more particularly, to an improved toner removal apparatus for cleaning residual toner from the surface of the photoreceptor of a copier or printer.
Xerography is one type of electrostatographic process, and in the xerographic process, a uniform electrostatic charge is placed upon a photoreceptor surface. The charged surface is then exposed to a light image of an original to selectively dissipate the charge to form a latent electrostatic image of the original. The latent image is developed by depositing finely divided and charged particles of toner upon the photoreceptor surface. The charged toner being electrostatically attracted to the latent electrostatic image areas to create a visible replica of the original. The developed image is then usually transferred from the photoreceptor surface to a final support material, such as paper, and the toner image is fixed thereto to form a permanent record corresponding to the original.
In a typical xerographic copier or printer, a photoreceptor surface is generally arranged to move in an endless path through the various processing stations of the xerographic process. When the photoreceptor surface is reusable, the toner image is then transferred to a final support material, such as paper, and the surface of the photoreceptor is prepared to be used once again for the reproduction of a copy of an original. Although a preponderance of the toner image is transferred to the paper during the transfer operation, some of the toner forming the image is unavoidably left behind on the photoreceptor surface. This remaining toner on the photoreceptor surface after the image transfer is referred to as residual toner. Residual toner also includes any patches or bands of toner not transferred to the final support material. Many typical copiers or printers use particularly placed and developed patches or bands of toner for process control, and these patches or bands of toner must also be removed by the toner removal apparatus. Thus, all residual toner must be removed from the photoreceptor to prevent degrading subsequent copies reproduced by the copier or printer. Optimally, the residual toner is removed without redepositing the toner onto the photoreceptor or smearing the toner on the photoreceptor surface as an unacceptable film.
One widely accepted method of cleaning residual toner from the surface of a photoreceptor of a typical copier or printer is by means of a cylindrical brush rotated in contact with the photoreceptor surface at a relatively high rate of speed. U.S. Pat. No. 2,832,977 discloses a rotatable brush mounted in close proximity to the photoreceptor surface to be cleaned and the brush is rotated so that the brush fibers continually wipe across the photoreceptor. In order to reduce the dirt level within the copier, a vacuum system is provided which pulls loosely held residual toner from the brush fibers and exhausts the toner from the copier. To assist the vacuum system in removal of the residual toner, the brush fibers are treated with a neutralizing ion spray from a corona generating device. This ion spray is intended to negate any triboelectrification generated when the brush wipes across the photoreceptor surface. Unfortunately, the brush became contaminated with toner after extended usage and had to be replaced more frequently than desired. With increased processing speeds of copiers and printers, the foregoing brush cleaning technique was not practical without improvements.
U.S. Pat. No. 3,572,923 discloses a cylindrical fibrous brush similar to the above mentioned patent, however, after the photoreceptor surface is cleaned, a second cleaning operation is performed on the cleaning brush in which residual toner collected on the brush is electrostatically transferred from the brush fibers to a biased transfer member. To provide appropriate electrostatic relationship between the cleaning members, the brush fibers are mounted on a non-conductive core and the brush is biased to attract toner from the photoreceptor surface to the brush.
U.S. Pat. No. 3,722,018 discloses a more efficient residual toner cleaning system by positioning a corona generating device in the residual toner cleaner of U.S. Pat. No. 3,572,923 to induce a charge on the brush fibers and toner thereon of a polarity opposite that of a biased transfer roll, so that the toner collected by the brush are efficiently transferred from the brush to the roll. U.S. Pat. No. 3,780,391 discloses that toner removal from the brush can also be accomplished by the use an electrically biased flicker bar.
U.S. Pat. No. 4,435,073 discloses a rotatable cylindrical brush cleaning apparatus for removing toner particles from a photoconductive surface. The brush is supported for rotation in a housing. The housing has an opening confronting the photoconductive surface and an aperture communicating through a conduit with a vacuum source. The brush extends from the housing opening into contact with the photoconductive surface. A plurality of flicker bars are mounted in the interior of the housing and in an air stream created by the vacuum source. The flicker bars are fabricated from materials which will not only cause the brush fibers to become electrostatically charged through wiping contact with the bars, but will cause the charge on the brush to reverse at least once for each revolution of the brush.
U.S. Pat. No. 4,851,880 discloses a rotating cylindrical brush and vacuum cleaning apparatus for removing toner particles from an image-bearing surface of a copier or printer. A housing that surrounds and substantially encloses the brush has an open portion adjacent the image-bearing surface. The brush extends through open portion of the housing and into engagement with the image-bearing surface. The rotation of the brush is in a direction opposite the direction of movement of the image-bearing surface. An elongated slot is located in the housing generally opposite the open portion and connects the interior of the housing to a vacuum source. Adjacent to the slot and on the interior of the housing is an airfoil to compress the brush fibers as the brush rotates thereby to loosen the toner particles in the brush fibers collected from the image-bearing surface. This loosening of the toner particles allows the vacuum to extract the toner particles through the housing slot. In an alternate embodiment, an additional airfoil of equal size is provided on the opposite side of the slot. The two airfoils compress the brush fibers on both sides of the slot and forces the air stream generated by the vacuum source to flow through brush fibers from opposite directions prior to exiting the housing through the slot.
U.S. Pat. No. 5,315,358 discloses one or more rotatable cylindrical brushes mounted in a housing having an opening therein to enable the brush or brushes to extend therefrom and into contact with a moving photoconductive surface to remove toner particles therefrom. A flicker bar is removably mounted within the housing and has an integral air channel therein. A vacuum source connected to the air channel in the flicker bar withdraws air and particles from the brush and housing. The solitary construction of the flicker bar provides a properly sized air channel that does not vary due to assembly tolerances.
Though several of the prior art residual toner cleaning devices provide successful residual toner removal, none of the prior art devices prevent excessive wear of the cleaning brushes, prevent toner filming, or enable effective cleaning with reduced air flow and thus less costly vacuum sources.
SUMMARY OF THE INVENTION
It is an object of the present invention to a more efficient toner removal apparatus for cleaning residual toner from a moving photoreceptor that enables a longer cleaning brush life and a reduced vacuum source size.
It is another object of the invention to provide an improved toner removal apparatus having an electrically biased, cylindrical brush mounted for rotation about its ax
Beatty Robert
Chittum Robert
Palazzo E. D.
Xerox Corporation
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