Patent Application
20090269110
The present invention generally relates to electro-photographic printers and more particularly to maintenance of high performance electro-photographic printers and increasing electro-photographic printer utilization.
Purchasing a state of the art high performance electro-photographic printer may require a major investment from a business concern. To recoup that investment, the business concern may keep the electro-photographic printer running 24 hours a day, seven days a week. So, any time that the electro-photographic printer is not operating, the owner is losing money.
During printing, the surface of a photoconductor, e.g., a photoconductive drum, receives an electrostatic charge as it moves past a charging station. Then, the charged surface passes an exposure station that exposes an illuminated image on the moving surface, e.g., with a modulated laser beam directed to a rotating mirror to repeatedly sweep the laser across the surface. The modulated laser striking the surface at least partially discharges local surface areas, forming a latent image of charged and discharged areas. As the surface moves past a developing station, the developing station deposits toner that adheres, e.g., electrostatically to the charged areas, but not to discharged areas or vice versa. This forms a toned image on the surface. As the toned surface contacts a recording medium, e.g., paper in a transfer station, typically in the presence of an electric field between the photoconductor and the medium, toner from the toned image transfers to the recording medium.
Generally, some residual of the toner particles do not transfer to the medium, and toner residue remains on the surface. So typically, the surface passes by a cleaning station to remove residual toner before the surface passes the charging station again. Electro-photographic printers frequently use a rotating brush, such as a fur brush, in the cleaning station that engages the surface to facilitate removing this residual toner. Unfortunately, such a brush fails to remove all residual toner. Some toner particles may agglomerate into larger particles or into a toner film that collect on the photoconductor. The rotating brush may not readily remove either of these. Typically removal requires an operator or customer service representative to take the printer system down and hand clean the photoconductor with rags and chemicals. This downtime costs the owner from loss of productivity and also for customer service representative time.
Consequently, electrophotographic printers may employ a scraper blade held against the moving surface in addition to or instead of a brush. A typical scraper blade is a soft plastic or elastomeric material edge pressed against the photoconductor surface. The blade may cause wear and tear to the surface, scratching the surface. Further, residual toner may attach to the scraper blade surface itself, which impairs scraper bladed efficiency. Also contact stresses during the scraping process can cause the scraper blade may to wear unevenly. The uneven wear produces an uneven contact line making the scraper blade ineffective (e.g., causing streaking like old windshield wipers) and causing uneven photoconductor wear.
U.S. Pat. No. 7,319,841 to Bateman III, et al. entitled “Apparatus and Method for Cleaning Residual Toner with a Scraper Blade Periodically Held in Contact with a Toner Transfer Surface,” assigned to the assignee of the present invention and incorporated herein by reference, shows an improvement on the typical printer scraper blade. The Bateman III, et al. blade is attached to a brush housing and held away from the photoconductor during normal printing operation. Periodically, the Bateman III, et al. brush housing rotates to contact the scraper blade to the photoconductor surface. While photoconductor and blade wear and tear are dramatically reduced by Bateman III, et al., even intermittent use causes some scratching and wear, reducing the life of both the photoconductor and the blade. Replacing either also carries printer downtime costs.
Thus, there is a need for maintaining in state of the art high performance printers and especially, for maintaining the surface of a photoconductor free from residual toner.
It is therefore a purpose of the invention to reduce high performance printer down time;
It is another purpose of this invention to improve electro-photographic printer reliability;
It is yet another purpose of the invention to reduce electro-photographic printer operating and maintenance costs.
The present invention is related to a toner brush for a printer and a printer including the toner brush. The toner brush includes a substrate (e.g. a core cylinder) with a cleaning brush and a residual toner brush superimposed over one another. During printing the printer holds the residual toner brush against a photoconductor or photoconductive surface, e.g., a photoconductive drum. For deep cleaning, the printer moves the cleaning brush to the photoconductive surface and holds it against the surface during deep cleaning. Deep cleaning may be automatically or manually (e.g., by an operator) initiated.
The foregoing and other objects, aspects and advantages will be better understood from the following detailed description of a preferred embodiment of the invention with reference to the drawings, in which:
Turning now to the drawings, and more particularly,
Preferably, the toner brush 102 includes interleaved bristles in two groups, bristles in each group having a common nominal length and tensile strength or stiffness. In one group, the bristles are long and soft and in the other, the bristles are shorter and stiffer. Thus, as provided in more detail hereinbelow, in a first, normal operating position the toner brush 102 uses the group of longer, softer bristles to remove residual toner that remains on the photoconductor 104 after each printing. Periodically, the toner brush 102 moves to a second position to place short deep cleaning bristles in the other group in contact with the photoconductor 104 to remove toner deposits and agglomerate in a deep cleaning cycle. Since the preferred toner brush 102 removes virtually all toner in the deep cleaning cycles, down-time from manual cleaning is dramatically reduced or eliminated. Further, the deep cleaning bristles cause very little, if any, photoconductor surface damage or scratching, which reduces the cost incurred in replacing the photoconductors 104.
The core cylinder 110 may be any suitable material such as paper/cardboard, plastic or poly(tetrafluoroethylene) (PTFE). The longer bristles are, preferably, of a suitable soft non-absorbative natural (e.g., fur or hair) or man-made material (e.g., rayon, nylon, or a polyester polymer) for sweeping toner away. Preferably also, the shorter bristles are of a suitable non-absorbative natural (e.g., hog/boar bristle) or man-made non-conductive material (e.g., thicker rayon, nylon, or a rayon/nylon/polyester polymer or a polyester polymer) that is stiff enough to remove residual toner, wax, silica, and paper by-products or anything else that may collect on the photoconductor 104. Further, these shorter bristles may be embedded with an abrasive material, e.g., silica, tungsten oxide, tungsten carbide, silicon carbide, or walnut shells. Preferably, the bristles are chosen such that the stiffer short bristles have a minimum flex (e.g., at ½ inch or 1.25 cm) and the softer long bristles sweep the toner from the photoconductor 104 without the shorter bristles contacting the surface of photoconductor 104.
Advantageously, the preferred toner brush removes virtually all toner in the deep cleaning cycles, customer service representative time and printer down-time from manual cleaning is dramatically reduced or eliminated. Further, the deep cleaning bristles cause very little, if any, photoconductor surface damage or scratching, which reduces the cost incurred in replacing the photoconductors.
While the invention has been described in terms of preferred embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the appended claims. It is intended that all such variations and modifications fall within the scope of the appended claims. Examples and drawings are, accordingly, to be regarded as illustrative rather than restrictive.
