Electrophotography – Cleaning of imaging surface – Fibrous brush
Reexamination Certificate
2001-02-23
2003-03-25
Royer, William J. (Department: 2852)
Electrophotography
Cleaning of imaging surface
Fibrous brush
Reexamination Certificate
active
06539197
ABSTRACT:
FIELD OF THE INVENTION
The present invention is related to a cleaning device applicable to an electrostatic recording system, such as for instance a copying or a printing system, in order to remove residual developer from the surface of an image-forming member.
BACKGROUND OF THE INVENTION
In a typical printing or copying process, a charged latent image is formed on an image-forming member by image-wise exposure. The image-forming member can be an endless member such as a drum or a belt. Typical graphical processes include amongst others magnetography, ionography and electrography, particularly electrophotography. In the latter process for instance, the charged latent image is formed on a pre-charged photosensitive member by image-wise exposure to light. The latent image is subsequently made visible on the image-forming member with developer at a development zone, the developer comprising, or consisting of, charged toner. After the development of the latent image, the developed image is transferred to a recording medium, directly or via one or more intermediate image-carrying members, where it may be permanently fixed. Examples of intermediate image-carrying members are endless belts. In practice the transfer from an image-delivering member being either an image-forming member or an intermediate image-carrying member to an image-receiving member being either an intermediate image-carrying member or a recording medium may be incomplete. Multiple subsequent transfers are possible. In normal operating conditions, typical transfer efficiencies range from 95% to 100%. The residual image on the image-delivering member has to be removed because otherwise the image quality of subsequently formed or transferred images can be seriously disturbed.
This residual image has to be removed before re-entering into the development zone. Otherwise this could lead to serious image defects because of mixing up of the new developed or transferred image with the residual image.
This cleaning action is executed by a cleaning station positioned downstream from the transfer zone. The cleaning station comprises at least a revolving brush which can be engaged against the image-delivering member for removing residual developer therefrom, a high voltage collecting roller in rolling contact with the brush roller for brush de-toning and a scraper blade contacting the high voltage roller for scraping developer therefrom.
The cleaning of the high voltage roller is a problem. This roller is a rigid roller in rolling contact with the cleaning brush. In the contact zone, developer is transferred to the high voltage roller by biasing the high voltage roller such that an attractive electrical field is created. A cleaning blade is positioned downstream of the contact zone to scrape off the developer from the high voltage roller. Usually to maximize force, the cleaning blade is positioned at an obtuse contact angle. The contact angle is defined with respect to a line tangent to the point of contact of the cleaning blade with the rotating high voltage roller and is the angle between this tangent line, at the uncleaned section of the roller, and the cleaning blade. This obtuse contact angle is typically between 160 and 170 degrees. The cleaning blades used as such are usually very stiff and rigid amongst others to prevent flip over of the cleaning blade as for instance when there is no developer on the roller. As a consequence, more elastic cleaning blades are unsuited because such flip over is detrimental both with respect to the lifetime of the blade and the cleaning efficiency. A cleaning blade mounted at an obtuse contact angle is typically made of an incompressible rigid material such as stainless steel.
In U.S. Pat. No. 4870466 (lida, assigned to Ricoh) a cleaning blade is disclosed which is mounted at an acute contact angle, i.e. a trailing cleaning blade, with respect to the high voltage roller. However, the contact angle disclosed seems to be clearly smaller than 45 degrees. As a result, the contact area between the cleaning blade and the high voltage roller is rather large. It is found that cleaning at such small angles is inefficient. Moreover, the cleaning blade is mounted such that the waste toner which is removed from the high voltage roller can not fall down freely to be further removed, but instead, at least to some extent, will build up between the roller and the cleaning blade and as such may even push the cleaning blade away from the high voltage roller.
OBJECTS OF THE INVENTION
It is an object of the present invention to provide a cleaning blade to scrape off developer and debris from the surface of a collecting roller, being used as a brush de-toning device in a cleaning unit.
It is a preferred object of the invention to mount the cleaning blade such that the cleaning blade has a good cleaning ability for an extended period of time and that the waste developer which is scraped off the high voltage roller is allowed to freely fall down to be further removed by a revolving auger and/or an air flow.
It is a further preferred object of the invention to provide a compressible cleaning blade, which is not damaged when exposed to carrier particles and other debris, which may be present on the surface of the high voltage roller.
It is still a further preferred object of the invention to provide a wear-resistant cleaning blade and an associated mounting position which allows for an efficient cleaning of a collecting roller having a fairly rough surface, i.e. with Ra ranging from 0.05 to 0.15.
SUMMARY OF THE INVENTION
According to a first aspect of the invention there is provided a cleaning device being part of a copying or printing system for removing residual developer from the surface of an image-delivering member comprising:
a cleaning brush in rolling contact with said surface of said image-delivering member for removing residual developer therefrom, said cleaning brush being rotatable in a first predetermined direction;
a collecting roller in rolling contact with said revolving brush, said collecting roller being rotatable in a second predetermined direction;
means for biasing said collecting roller to generate an electrical field which attracts the residual developer from the cleaning brush and collects it onto its surface; and
a cleaning blade having a forward end portion in frictional contact with the collecting roller wherein, in an operative orientation of the device, said cleaning blade is in contact with said collecting roller at a contact position where the collecting roller is moving in an upward direction, said cleaning blade being mounted such that the contact angle (as hereinbefore defined) is less than 90 degrees.
In an embodiment of the invention, the cleaning device is retractable. The cleaning device is a part of a copying or printing system and is intended for removing residual developer from the surface of an image-delivering member such as for instance an image-forming member or an image-carrying member. Examples of image-forming members are drums or belts with a photoreceptive or a magneto-sensitive outer layer. Examples of image carrying members are seamed or seamless intermediate transfer belts. Such an intermediate transfer belt may be composed of an electrically semi-insulating or insulating material with a low surface energy, or comprises at least a top coating of such a material. Examples of such a material are polyesters such as e.g. Hytrel 7246, polyimides, polycarbonates or dissipative polymer blends.
The collecting roller in rolling contact with said revolving brush is electrically biased such that an electrical field is generated which attracts the residual developer from the cleaning brush and collects it onto its surface.
The cleaning blade is preferably composed of an elastic material with a hardness ranging from 50 to 80 Shore A.
We are aware that cleaning blades are widely used, particularly for cleaning the image-forming member. In electrophotography the image-forming member is usually a drum or a belt covered with an organic photo-conductive layer. The cleaning of
Knobbe Martens Olson & Bear LLP
Royer William J.
Xeikon International N.V.
LandOfFree
Printer cleaning device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Printer cleaning device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Printer cleaning device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3080511