Abstract: An apparatus for developing a latent image recorded on a surface, including; a housing defining a chamber storing at least a supply of toner therein; a donor member spaced from the surface and adapted to transport toner from the chamber of the housing to a development zone adjacent the surface; a plurality of electrodes longitudinally disposed on the donor member; and a commutator brush contacting the electrodes along a portion of the circumference of the donor member, said commutator brush including means for generating pneumatic force to move said commutator brush into contact with the electrodes.

Abstract: An improved method for controlling the optical density of an image printed by an electrostatic printer is provided. The method compensates for optical density drift over the useful life of a toner receptacle by adjusting the voltage vector between the photoconductive belt and the toner particles. The method calculates an overall toner usage amount and adjusts the voltage vector when the amount reaches one or more predetermined values. In this manner, the present method controls the optical density of a printed image over the useful life of the toner receptacle.

Abstract: An image forming apparatus of the present invention is capable of forming an oscillation electric field in a developing region on the basis of the particle size of toner and the particle size of magnetic carrier. Assume that the oscillation electric field includes a phase for causing the toner to move toward a latent image and having a duration t.sub.1, that the electric field has a period T, that the toner has a weight-average particle size of L.sub.t, and that the carrier has a weight-average particle size of L.sub.c. Then, there hold a relation of 1.0.times.10.sup.-4 <t.sub.1.sup.2 /L.sub.t <1.0.times.10.sup.-3 ?sec.sup.2 /m! and a relation of T.sup.2 /L.sub.c <0.005 ?sec.sup.2 /m!. The apparatus insures images with uniform dots and including a minimum of noise.

Abstract: A uniform image is obtained by matching the sliding friction force, the moving speed and the developing agent in a developing region of two developing rollers and an electric characteristic of a photosensitive body used for image development. Two developing rollers rotating in directions opposite to each other are used, the moving direction of the first developing roller being opposite to the moving direction of the photosensitive body, and a circumferential speed ratio of a circumferential speed of the first developing roller to a circumferential speed of the photosensitive body is within a rage of 0.5 to 2.5; and the moving direction of the second developing roller is equal to the moving direction of the photosensitive body, and a circumferential speed ratio of a circumferential speed of the second developing roller to a circumferential speed of the photosensitive body is within a range of 1.5 to 3.5.

Abstract: A development apparatus according to the invention comprises at least two developer carrier members in juxtaposition for transporting a developer material to a development region between the developer carrier members and an image bearing member in opposed relation. An AC voltage applying device is adapted to apply AC voltages to the respective developer carrier members thereby applying AC electric fields to the respective gaps between the developer carrier members and the image bearing member based on an active period to apply the AC electric field and an inactive period to apply no AC electric field. When one of the adjacent developer carrier members is subject to the active period, the other developer carrier member is subject to the inactive period.

Abstract: A magnet roll including a cylindrical permanent magnet having a surface thereon a plurality of magnetic poles which extend along an axis of the magnet roll and an electroconductive ceramic layer formed at least on a circumferential surface of the cylindrical permanent magnet. The electroconductive ceramic layer may be TiC, WC, TiN, TiCN, CrN, ZrN, HfN, Ti+TiN, and Cr+CrN. The magnet roll is used in a developing method of developing a latent image on a photosensitive drum by a magnetic developer while applying a bias voltage to a developing zone, in which the number of the magnetic poles (N) satisfies the relation: N.gtoreq.(V.sub.1 /V.sub.2).times..pi.D/6, wherein V.sub.1 is a peripheral speed (mm/s) of the photosensitive drum, V.sub.2 is a peripheral speed of the magnet roll and D is an outer diameter (mm) of the magnet roll.

Abstract: Electrographic printing apparatus for forming a toner image on a recording medium, includes: a magnetic brush having a rotatable magnetic core and a stationary outer shell; a developer supply for supplying a magnetic developer powder including toner to the magnetic brush. A print head on the outer shell forms a plurality of parallel lines of developer. Toner is selectively transferred from a plurality of electrodes within each line to a receiver. A receiver electrode is arranged in spaced relation to the print head to define a recording region through which the receiver can be moved.

Abstract: A developing device capable stable production of halftone image having excellent texture while maintaining suitable image density by utilizing an AC electric field between a developer-carrying member and an image-carrying member and providing a rest period wherein the AC electric field is not active so as to develop electrostatic latent image formed on the image carrying member.

Abstract: A method for achieving adjusted toner concentration of printed image on a recording medium in an image forming apparatus using an electrophotographic developing process including a photosensitive drum for forming a latent image on its negatively charged photoconductive insulating surface exposed to light according to an image pattern and a developing roller charged with a negative developing voltage to charge by rubbing a toner supplied from a toner supplier with a negative voltage.

Abstract: The present invention provides a carrier for developer of an electrostatic latent image and related technologies. The carrier is excellent in the ability to impart charge suitably and stably to toner and has a structure durable enough to maintain the ability for a long period of time such that the structure can prevent the toner from being adhered onto the carrier surface for a long period of time.The carrier comprises a core covered with a resin coating layer containing resin particles and an electroconductive fine powder in the form of a dispersion in a matrix resin.The carrier can be produced by a method comprising the steps of preparing a coating solution by placing materials in a solvent which can dissolve the matrix resin, but cannot dissolve the resin particles, dispersing the particles of the resin, applying the solution to a core and removing the solvent. A high-quality image can be formed by use of the developer comprising the carrier and the toner.

Abstract: An image forming apparatus having an image carrying member for carrying an electrostatic image, fluororesin has a surface layer containing a fluororesin, and a developing device for developing the electrostatic image on the image carrying member. The image carrying member has a surface layer containing a fluororesin. The developing device has a developer carrying member, which is arranged as opposed to the image carrying member and which carries a developer, and a bias applying device for applying a development bias voltage to the developer carrying member. A period of a waveform of the bias voltage applied by the bias applying device has an oscillating part and a quiescent part.

Abstract: An image forming apparatus includes an image bearing member for bearing an electrostatic image; a developer carrying member, opposed to the image bearing member, for carrying a developer containing toner; bias voltage applying device for applying a developing bias voltage to the developer carrying member, the bias voltage satisfying: ##EQU1## V1 (V): a voltage applying force to the toner toward the developer carrying member away from the image bearing member;T1 (sec): a time period of application of the voltage V1;V2 (V): a voltage applying force to the toner away from the developer carrying member toward the image bearing member;T2 (sec): a time period of application of the voltage V2;T3 (V): a time period of application of a voltage V3 which is (V1+V2)/2;d (m): distance between the image bearing member and the developer carrying member.

Abstract: In a color image forming apparatus, as the second and subsequent development processes of the simultaneously transfer type, a non-contact type AC field double-element development is employed, and an absolute value of the difference between the maximum bias which provides the maximum toner developing electric field in the direction to the side of the latent image carrier and the average value of the developing bias is set larger than an absolute value of the difference between the minimum bias voltage which provides the minimum toner developing electric field in the direction to the side of the latent image carrier and the average value of the developing bias, while the bias voltage region located between the maximum bias voltage and the average bias voltage is set to a ratio of from 0.25 to 0.45 for one period of the AC voltage, and the frequency of the bias voltage is set from 4 kHz to 10 kHz.

Abstract: A magnetic brush developer roll structure comprising a stationary magnet assembly including a magnet assembly shaft supporting magnet material. Bearings carried by the shaft, in turn, support a rotatable shell or tube forming the outer member of the roll structure. The bearings together with the shell or tube delineate an essentially sealed cavity in which one or more electrical contact brushes are disposed. The brush rubs against an inner wall of the shell or tube and provides an electrical path thereto. Using a plurality of brushes results in improved reliability.

Abstract: In a developing method, a layer of electrically charged toner particles is formed on a surface of a developer carrying member, and magnetic particles which retain on their surfaces electrically charged toner particles are dispersed on the surface of the developing carrying member. The toner particles and magnetic particles are carried on the developing carrying member to a developing position where a surface of an electrostatic latent image bearing member for bearing an electrostatic latent image is opposed with a clearance to the surface of the developer carrying member. An alternating electric field is formed at the developing position against the electrostatic image and chains of magnetic particles are formed by stationary magnetic field generating apparatus disposed behind the developer carrying member.

Abstract: An apparatus for controlling the concentration of toner within a developer material of carrier and toner. The apparatus having a magnetic roll for transporting a combination of carrier material and toner particles, a donor roll for transporting toner particles from said magnetic roll to a photoreceptor transfer zone, the magnetic roll and the donor roll each having a voltage applied thereto. A sensor measures the dynamic current between the magnetic roll and the donor roll and generates a signal as a function thereof. The dynamic current between the magnetic roll and the donor roll is a function of the concentration of the toner particles and the carrier material. As a result of the sensor output signal toner particles are added to the developer sump to maintain proper triboelectric properties within the developer unit.