Metal deforming – With cutting – By composite tool
Reexamination Certificate
2000-10-24
2003-08-12
Crane, Daniel C. (Department: 3725)
Metal deforming
With cutting
By composite tool
C072S325000
Reexamination Certificate
active
06604399
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to blades that regulate a developer layer thickness on a development roller in a development device, methods of manufacturing the same, and dies for manufacturing the same. The present invention also relates to development devices and image-forming devices using the blade. The present invention is suitable, for example, for a blade that regulates a layer thickness of a nonmagnetic monocomponent developer on the development roller, a method of forming the layer of the nonmagnetic monocomponent developer using the blade, a development device having the blade, and an electrophotographic image-forming device having one or more of these elements. Notwithstanding, the present invention is not limited to embodiments using the nonmagnetic monocomponent developer.
Hereupon, the “nonmagnetic monocomponent developer” is a single component developer that is nonmagnetized and includes no carrier. The “electrophotographic image-forming device” by which we mean is an image-forming device employing the Carlson process described in U.S. Pat. No. 2,297,691, as typified by a laser printer, and denotes a nonimpact printer that provides recording by depositing a developer as a recording material on a recordable medium (e.g., printing paper, and OHP film).
With the recent development of office automation, the use of electrophotographic image-forming devices such as a laser printer for computer's output devices, facsimile units, photocopiers, etc. have spread steadily. The electrophotographic process generally uses a photoconductive insulator (e.g., photosensitive drum, and photosensitive belt), and follows the procedural steps of charging, exposure to light, development, transfer, fixing, and other post-processes.
The charging step uniformly electrifies the photosensitive drum (e.g., at −600V). The exposure step irradiates a laser beam or the like on the photosensitive drum, and changes the electrical potential at the irradiated area down, for example, to −50 V or so, forming an electrostatic latent image. The development step electrically deposits a developer onto the photosensitive drum using, for example, the reversal process, and visualizes the electrostatic latent image. The reversal process is a development method that forms an electric field by a development bias in areas where electric charge is eliminated by exposure to light, and deposits the developer having the same polarity as uniformly charged areas on the photosensitive drum by the electric field. The transfer step forms a toner image corresponding to the electrostatic latent image on a recordable medium. The fixing step fuses and fixes the toner image on the medium using heat, pressure or the like, thereby obtaining a printed matter. The post-processes may include charge neutralization and cleaning on the photosensitive drum from which toner has been transferred out, a collection and recycle and/or disposal of residual toner, etc.
The developer for use with the aforementioned development step can be broadly divided into a monocomponent developer using toner and a dual-component developer using toner and a carrier. The toner may be a particle prepared, for example, in such a manner that an additive and a colorant such as a dye and a carbon black, or the like are dispersed in a binder resin made of synthetic macromolecular compound, and then is ground into a fine powder of approximately 3 through 15 &mgr;m. The additive, which is a fine particle used as a toner surface reforming agent, has been used originally for improving fluidity of toner, but sometimes for improving image quality. The additive may be selected among colloidal silica, titanium oxide, alumina, zinc stearate, and others. A usable carrier may include, for example, an iron powder or ferrite bead of approximately 100 &mgr;m in diameter. The monocomponent developer advantageously results in (1) simple and miniature equipment due to omitting mechanisms for controlling a carrier deterioration and toner density, and mixing and agitation mechanisms, and (2) no carrier or other waste in used toner.
The monocomponent developer may be further classified into a magnetic monocomponent developer in which toner contains a magnetic powder, and nonmagnetic monocomponent developer in which toner does not contain the same. However, the magnetic monocomponent developer is disadvantageous in (1) the low transfer performance due to the high content of low electrical resistant magnetic powder which hinders the increase of the electric charge amount, (2) the difficulty in colorization due to its black-color magnetic powder of low transparency; (3) the low fixing performance, which thereby requires high temperature and/or high pressure, due to the magnetic powder, increasing a running cost. Accordingly, the nonmagnetic monocomponent developer without these disadvantages is expected to be in increasing demand in future.
For the nonmagnetic monocomponent developer, the toner having a relatively high volume resistivity (e.g., at 300 G&OHgr;·cm, etc.) is commonly used. In addition, the toner, as basically carries no electric charge, needs to be charged by the triboelectricity or charge injection in the development device.
The development process employing the nonmagnetic monocomponent developer is divided into contact- and noncontact-type development processes: The contact-type development process deposits a developer on the photosensitive drum by bringing the development roller carrying the developer into contact with the photosensitive drum; and the noncontact-type development process providing a certain gap (e.g., of about 350 &mgr;m) between the development roller and the photosensitive drum to space them from each other, and flies the developer from the development roller and deposits the same onto the photosensitive drum.
It is significant for the development process employing the nonmagnetic monocomponent developer to ensure a sufficient image density by controlling the amount of toner fed from the development roller to the photosensitive drum. Thus, it is very important to form a specified toner layer through controlling its thickness on the development roller. As a typical method for regulating a toner layer thickness, it has conventionally been proposed to provide an elastic blade (restriction blade) in contact with the development roller to maintain the layer thickness uniform.
The contact-type development device employing the typical nonmagnetic monocomponent developer generally comprises a reset roller, a development roller, and a blade. The development roller is connected with a bias power supply from which the development bias is applied. The reset roller, which is also called supply roller or application roller, comes in contact with the development roller and serves not only to supply toner to the development roller, but also to scrape off and remove the toner unused for the development and remaining on the development roller. The development roller, which is, for example, a roller made of resin, adsorbs the charged toner onto its surface in the form of a thin layer, and conveys it to a development area in contact with the photosensitive drum.
The blade is brought into contact with the development roller and serves to regulate the toner layer to a uniform thickness. The blade may be made up of a metal member, or of an elastic member such as urethane, and regulates the toner layer by bringing an end portion or non-end portion (namely midsection) thereof into contact with the development roller. Disadvantageously, too thin toner layer would lead to reduced and varied image densities, and too thick toner layer would increase the ratio of the toner having reverse charge or low charge, and produce fogging (a phenomenon of undesirably coloring with the toner areas that have no image and thus are expected to be of white clarity). Accordingly, the blade is required to form a toner layer having an adequate thickness.
A description will be given of a regulation of the toner layer thickness by the blade, w
Fujikura Keisuke
Sasaki Masayuki
Yoshida Sadaaki
Armstrong Westerman & Hattori, LLP
Crane Daniel C.
Fujitsu Limited
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