Ricoh Company, Ltd.

Fuchio Kanno

Koji Sakamoto

Wataru Yasuda

Toshio Kaneko

Kazuo Kobayashi

Hiromi Ogiyama

Mitsuo Tanaka

Michio Takahashi

A developing device for developing an electrostatic latent image formed on an image bearing member such as a photosensitive member for use in an electrophotographic copying machine and the like using magnetic toner particles includes a rotatable sleeve, a magnet roll disposed inside of the sleeve and a doctor blade pressed against the sleeve for charging and forming a thin film of toner particles to be used in developing the latent image. In one form, the blade is provided movably in parallel with the rotating axis of the sleeve. In another form, an electrically conductive brush is provided to remove residual charges from the sleeve after each developing operation. In a further form, the tip end of the blade is disposed between the two adjacent magnetic poles of the magnet roll. In a still further form, the blade is constructed to have a two-part structure.

Developing device

A device for developing an electrostatic latent image formed on a photosensitive member includes a composite sleeve which is comprised of a cylindrical support, a dielectric layer formed on the support and a plurality of fine magnets serving as floating electrodes embedded in the dielectric layer and which is driven to rotate to carry magnetic toner as magnetically attracted to its outer peripheral surface.

A device is provided for developing an electrostatic latent image formed on an image bearing member with a developer comprised of magnetically attractable, electrically insulating toner particles for developing the latent image by applying the toner particles in the form of a thin film uniform in charge and thickness. The developing device generally comprises a developing sleeve, which is driven to rotate to carry thereon toner particles, and a pressure plate is held in pressure contact with the sleeve to thereby form a thin film of charged toner particles on the sleeve upstream of the developing station. In one aspect of the present invention, the pressure plate has a low hardness or relatively easily wearable region which is in pressure contact with the sleeve so as to prevent toner particles from permanently sticking to the pressure plate. In another aspect, the pressure plate is structured to have a locally defined relatively easily deflectable region which is in pressure contact with the sleeve. In a further aspect, the pressure plate is movable with respect to the sleeve to thereby remove stuck toner particles from the pressure plate and from the sleeve. In a still further aspect, a separator strip is provided, interposed between the pressure plate and the sleeve, which also keeps toner particles from sticking to the pressure plate. In a still further aspect, a cleaner is provided for cleaning the pressure plate periodically or continuously in order to keep toner particles from sticking to the pressure plate and to allow a thin film of uniformly charged toner particles to be formed on the sleeve for use in developing the latent image at the developing station.

Developing device with regulated developer supply

A photosensitive drum includes a cylindrical core which may be fixedly mounted on a rotating shaft and which is comprised of an elastic material and an outer sleeve which is provided on the outer peripheral surface of the core and which includes a supporting layer and a photosensitive layer formed on the supporting layer. A combination of the elastic core and the outer sleeve is constructed such that the drum only deforms locally at a point where an external force is applied and its immediate vicinity while maintaining the other portion virtually unchanged. In one form, the outer sleeve is fixedly mounted on the core, and, in another form, the outer sleeve is detachably mounted on the core. In the latter case, it is so structured that no relative movement takes place between the core and the outer sleeve even if external forces are applied to the drum.

Locally deformable photosensitive drum for use in electrophotography

A device for developing an electrostatic latent image formed on a photosensitive member includes a developing sleeve which is driven to rotate in a predetermined direction and a pressure blade which is kept pressed against the sleeve to form a thin film of uniformly charged toner so as to apply for the latent image for development. In accordance with the present invention, the forward end portion of the pressure blade is specifically shaped such that a projection having the width which substantially corresponds to the width of an image forming area of the photosensitive member is provided to extend beyond a contact line between the sleeve and the blade thereby allowing to form the thin film of toner whose width substantially corresponds to the image forming area of the photosensitive member, thereby preventing the waste of toner from occurring.

A developing device includes a developing sleeve driven to rotate to transport a film of developer riding on its outer peripheral surface, the developing sleeve including an electrically conductive cylinder, a dielectric layer formed on the cylinder and a plurality of fine electrodes provided electrically isolated from each other at least at the outer peripheral surface of the dielectric layer. In one form, each of the fine electrodes is previously coated with an insulating material having the volume resistivity of 10.sup.12 ohms-cm or more to a thickness of 0.5 microns to 0.5 mm. An intermediate dielectric layer may be provided between the cylinder and the first dielectric layer. Further, an electrically conductive layer may be provided as sandwiched between the two dielectric layers. Moreover, the outermost surface of the sleeve may be appropriately roughened in view of the average diameter of toner particles used.

Developing device having dispersed floating electrodes in a dielectric

A device for developing an electrostatic latent image formed on an imaging surface by applying a thin film of uniformly charged magnetic toner includes a sleeve which is driven to rotate at constant speed in an intended direction, a hopper for supplying toner to said sleeve, a pressure blade pressed against the sleeve to form the thin film of charged toner on the sleeve and a discharging scraper provided with a plurality of holes and disposed in contact with the sleeve at a location downstream of the developing region, whereby remaining toner on the sleeve is scraped off the sleeve and returned to the sleeve after passing through the holes, to thereby have the charge remaining on the sleeve removed by the discharging scraper.

Voltage-controlled developing device

A developing device for developing an electrostatic latent image includes a tank for containing therein a quantity of developer, a developing sleeve driven to rotate in a predetermined direction and having an outer peripheral surface which defines a path for transporting the developer, a magnet roll disposed inside of the developing sleeve for keeping the developer attracted to the peripheral surface of the sleeve, and a pressure plate pressed against the sleeve to form a thin film of developer on the peripheral surface of the sleeve before being applied to the latent image.

A device for forming a toner film for use in developing an electrostatic latent image on an image bearing member, such as photosensitive member, is provided. A developing sleeve is rotatably provided and a magnet roll is also rotatably provided inside of the sleeve for magnetically attracting a blade of magnetic material to the outer peripheral surface of the sleeve thereby causing the toner carried on the sleeve to be formed into a film of desired thickness and charge. The magnet roll is formed with a plurality of magnetic poles elongated axially and arranged along the periphery of the roll in alternating polarities. Thus, the magnetic attractive force applied by the magnet roll to the blade changes periodically. In the present invention, the frequency of alternating magnetic field applied to the blade is set to be larger than the first order resonant frequency of the blade, thereby allowing to maintain the applied magnetic force as constant as possible.

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Yokohama, Japan

Fuchio Kanno