Metal working – Method of mechanical manufacture – Roller making
Reexamination Certificate
2000-04-14
2002-02-05
Rosenbaun, I. Cuda (Department: 3726)
Metal working
Method of mechanical manufacture
Roller making
C029S895210, C492S008000
Reexamination Certificate
active
06343419
ABSTRACT:
The present invention relates to a method and apparatus for developing a latent image. More specifically, the invention relates to a magnetic roll for development systems.
The features of the present invention are useful in the printing arts and more particularly in electrophotographic printing. In the well-known process of electrophotographic printing, a charge retentive surface, typically known as a photoreceptor, is electrostatically charged, and then exposed to a light pattern of an original image to selectively discharge the surface in accordance therewith. The resulting pattern of charged and discharged areas on the photoreceptor form an electrostatic charge pattern, known as a latent image, conforming to the original image. The latent image is developed by contacting it with a finely divided electrostatically attractable powder known as “toner.” Toner is held on the image areas by the electrostatic charge on the photoreceptor surface. Thus, a toner image is produced in conformity with a light image of the original being reproduced. The toner image may then be transferred to a substrate or support member (e.g., paper), and the image affixed thereto to form a permanent record of the image to be reproduced. Subsequent to development, excess toner left on the charge retentive surface is cleaned from the surface. The process is useful for light lens copying from an original or printing electronically generated or stored originals such as with a raster output scanner (ROS), where a charged surface may be imagewise discharged in a variety of ways.
In the process of electrophotographic printing, the step of conveying toner to the latent image on the photoreceptor is known as “development.” The object of effective development of a latent image on the photoreceptor is to convey toner particles to the latent image at a controlled rate so that the toner particles effectively adhere electrostatically to the charged areas on the latent image. A commonly used technique for development is the use of a two-component developer material, which comprises, in addition to the toner particles which are intended to adhere to the photoreceptor, a quantity of magnetic carrier granules or beads. The toner particles adhere triboelectrically to the relatively large carrier beads, which are typically made of steel. When the developer material is placed in a magnetic field, the carrier beads with the toner particles thereon form what is known as a magnetic brush, wherein the carrier beads form relatively long chains which resemble the fibers of a brush. This magnetic brush is typically created by means of a “developer roll.” The developer roll is typically in the form of a cylindrical sleeve rotating around a fixed assembly of permanent magnets called a magnetic roll. The carrier beads form chains extending from the surface of the developer roll, and the toner particles are electrostatically attracted to the chains of carrier beads. When the magnetic brush is introduced into a development zone adjacent the electrostatic latent image on a photoreceptor, the electrostatic charge on the photoreceptor will cause the toner particles to be pulled off the carrier beads and onto the photoreceptor. Another known development technique involves a single-component developer, that is, a developer which consists entirely of toner. In a common type of single-component system, each toner particle has both an electrostatic charge (to enable the particles to adhere to the photoreceptor) and magnetic properties (to allow the particles to be magnetically conveyed to the photoreceptor). Instead of using magnetic carrier beads to form a magnetic brush, the magnetized toner particles are caused to adhere directly to a developer roll. In the development zone adjacent the electrostatic latent image on a photoreceptor, the electrostatic charge on the photoreceptor will cause the toner particles to be attracted from the developer roll to the photoreceptor.
As stated earlier, development is typically accomplished by the use of a magnetic brush. The magnetic brush is typically formed by a developer roll which is typically in the form of a cylindrical sleeve which rotates around a fixed assembly of permanent magnets. When utilizing magnetic brush-type development, the cylindrical sleeve is typically made of an electrically conductive, non-magnetically conductive material, for example, aluminum.
Prior art developer rolls for use with magnetic pressure development typically include a magnetic roll about which a sleeve is positioned. The magnetic roll may be held stationary and the sleeve rotates. Conversely, the sleeve may rotate with the magnetic roll permanently positioned. In configurations where the magnetic roll is stationary and the sleeve rotates, the segments are so positioned to attract the toner particles toward the developer nip between the developer roll and the photoconductive surface of the drum.
Prior art developer rolls have typically been manufactured with a core or body and magnets positioned on the periphery of the core. Typically the magnets are glued to the periphery of the core. The gluing of magnets to a core contributes to a series of problems. The gluing leads to positioning errors both radially and tangentially, reducing the quality of the roll. Further, add cost may be required to perform subsequent machining of the periphery of the roll to obtain needed accurate tolerances. Furthermore, the adhesive use to glue the magnets to the core may require special handling to conform to environmental and safety regulations. In addition, the gluing of the magnets to the core is a labor intensive hand operation which is very costly. Also, the use of glued magnet segments leads to a magnetic roll that is hard to disassemble for remanufacturing. While it may be difficult to remove the glue to separate the magnets from the core, it is further more difficult to remove the residual glue from the core and the magnets. It is further difficult to dispose of the residual glue and remove from the magnets and core.
Recently, magnetic rolls had been manufactured by positioning the magnetic strips around the periphery of a mold and molding the core with the magnetic strips prepositioned in the core of the mold. This manufacturing procedure utilizes an expensive molding. Further, the process is limited to urethane resins. The process is expensive in that the curing time for the molding operation may be extensive. Also the elevated temperatures required result in long cure times. The requirement that the process utilize urethane foam limits the flexibility of the process and the limited strength and durability of the urethane foam affect the quality and suitability of this type of magnetic roll in many applications.
The magnetic roll of the present invention is intended to alleviate at least some of the aforementioned problems.
The following disclosures may be relevant to various aspects of the present invention:
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U.S. Pat. No. 5,453,471 discloses a hollow member which serves as a cylinder having an inner configuration which matches the outer configuration of a magnet roller to be manufactured. The member is mounted in a metallic mold and then the metallic mold is clamped. A molten resin containing magnetic particles is injected into the mold cavity of the hollow member through a runner.
U.S. Pat. No. 5,384,957 disclos
Alvarez Jorge A.
Litman Alan M.
Cuda Rosenbaun I.
Xerox Corporation
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