Abstract: A rotary developing device includes a developing unit having plurality of developing chambers arranged around an axis rotation with each having a developer agitating device located therein wherein the rotary developing device is rotatable about the axis to locate any one of the plurality of developing chambers at a developing position where an image carrier is located, the developer agitating device of one of the plurality of developing chambers located at the developing position and the developer agitating device of at least one of the other developing chambers being drivable and wherein the developer agitating device of the at least one of the other developing chambers has a higher agitation speed than the developer agitating device of the one developing chamber located at the developing position.

Abstract: In an image forming apparatus, a rotary developing device has a developing unit in which a plurality of developing chambers are arranged around an axis of rotation. The developing unit is rotated about the axis to bring one of the chambers to a developing position where an image carrier is located. In each of the chambers, part of a developer removed by a doctor blade is received by a guide and then released from the guide into the chamber. This part of the developer is agitated in the vertical direction together with the developer existing in the chamber by the rotation of the device. As a result, the developer is agitated and charged in a desirable manner.

Abstract: An image forming device includes a plurality of developing devices and a photosensitive drum. Each of the developing devices includes a developer carrying roller. One of the developing devices is moved to a developing position confronting the photosensitive drum which is formed with a latent image. A first developing bias including a d.c. component and an a.c. component is applied to the developer carrying roller and developer on the developer carrying roller is rendered in contact with the latent image on the photosensitive drum so that the latent image is developed. On the other hand, when the developer on the developer carrying roller comes in contact with and separates from the photosensitive drum due to the movement of the developing device, a second developing bias is applied to the developer carrying roller.

Abstract: A method for controlling a piezoelectric actuator includes: a safety range setting process in which a safety range V.sub.range1 or V.sub.range2 of an applied voltage is set so that an area of 180.degree. domain rotation is within one third or less of an area of full 180.degree. domain rotation S.sub.1 or S.sub.2 in a positive or negative region of the applied voltage; and a driving process in which the voltage is applied to the piezoelectric actuator with a limitation of the safety range V.sub.range1 or V.sub.range2. A controller which drives a piezoelectric actuator according to the controlling method is also provided. A temperature compensation is applied if necessary. The 180.degree. domain rotation is limited by the lower or upper limit of the safety range, so that local concentration of inner stress is suppressed and the actuator is driven at its maximum ability without cracks or splits.

Abstract: In an image forming apparatus, a rotary developing device has a developing unit in which a plurality of developing chambers are arranged around an axis of rotation. The developing unit is rotated about the axis to bring one of the chambers to a developing position where an image carrier is located. In each of the chambers, part of a developer removed by a doctor blade is received by a guide and then released from the guide into the chamber. This part of the developer is agitated in the vertical direction together with the developer existing in the chamber by the rotation of the device. As a result, the developer is agitated and charged in a desirable manner.

Abstract: A developing device is provided which has a developing chamber, a toner container and a hopper portion all provided together on a revolving holding mechanism. A drive device is provided to revolve the driving mechanism and a stopping device is provided to stop this holding mechanism revolving movement at least to provide the developing chamber in a facing relationship to an image carrier. Moreover, the relative position of the toner chamber and the hopper portion are such that the hopper portion can be replenished with toner from the toner chamber at least once during a complete rotation of the revolving holding mechanism. Replenishment can occur independently of image formation, while the holding mechanism is revolving or during a pause in the revolving of the holding mechanism.

Abstract: In an image forming apparatus, a developing device has a toner container having a toner outlet, and a receptacle having a mount portion for removably mounting the container. The insertion space of the mount portion and the toner outlet are each tapered such that the width in the up-and-down direction sequentially decreases toward the deepest end. In a developing device of the type causing the container to be rotated to bring the toner outlet into alignment with a toner inlet formed in the receptacle, the edge portion of the toner outlet is tapered to reduce a load during rotation and to ensure close contact at the end of the mounting of the container.

Abstract: An image forming apparatus of the type having a rotary developing device or revolver, and a power supply device. When the revolver is rotated to bring one of its developing sections to a developing position, the end of a developing roller disposed in the developing section faces a bracket mounted on a rear wall included in the apparatus body. A retractable rod-like terminal is mounted on the bracket and constantly biased by a spring. A bias for development is applied from a bias circuit to the developing roller via the retractable terminal.

Abstract: A developing device is provided with a toner container rotatable to a toner replenishing position. The toner container has a toner outlet in a wall of the container. This outlet includes an edge portion that is downstream in the direction of the rotation of the container that is jutted towards the center of toner container rotation which is inside the toner container. This inwardly jutted edge portion of the toner outlet provides a toner outlet profile having an edge that is lower than the other edge of the toner outlet in the direction of toner container rotation so that the lower edge does not engage into contact with a toner inlet on a wall of a developing chamber of a developing device until after the toner outlet is in a position overlapping at least most of the toner inlet.

Abstract: An image forming device includes a plurality of developing devices and a photosensitive drum. Each of the developing devices includes a developer carrying roller. One of the developing devices is moved to a developing position confronting the photosensitive drum which is formed with a latent image. A first developing bias including a d.c. component and an a.c. component is applied to the developer carrying roller and developer on the developer carrying roller is rendered in contact with the latent image on the photosensitive drum so that the latent image is developed. On the other hand, when the developer on the developer carrying roller comes in contact with and separates from the photosensitive drum due to the movement of the developing device, a second developing bias is applied to the developer carrying roller.

Abstract: An image forming apparatus of the type having a rotary developing device or revolver, and a power supply device. When the revolver is rotated to bring one of its developing sections to a developing position, the end of a developing roller disposed in the developing section faces a bracket mounted on a rear wall included in the apparatus body. A retractable rod-like terminal is mounted on the bracket and constantly biased by a spring. A bias for development is applied from a bias circuit to the developing roller via the retractable terminal.

Abstract: In an image forming apparatus, a rotary developing unit or revolver is loaded with a removable black developer container at the center thereof. The container is formed with a toner outlet. A receptacle assigned to black toner is provided at the end of the axis of the revolver and formed with a toner inlet. The receptacle constitutes a hopper portion. A supply roller is disposed in the receptacle. A screw conveyor extends out from a black developing chamber defined in the revolver into a communication chamber which communicates the receptacle to the developing chamber. A shutter is located at the loner inlet of the receptacle and rotatable due to its own weight while the revolver is in rotation. When more than a predetermined number of printings are produced by use of the black developing chamber, printing is interrupted. Then, the revolver is rotated to transfer the toner from the container to the hopper portion. The revolver may be rotated every time a single printing is produced.

Abstract: In an image forming apparatus, a rotary developing device effects development by revolving a plurality of developing sections around a rotary shaft until any one of them reaches a developing position where it faces an image carrier. Cartridges are respectively mounted to hoppers included in the developing sections. Guides are provided on the inner periphery of each cartridge in order to guide toner, moving due to the revolution or the developing device, toward a toner outlet formed in the cartridge. Even when the amount of toner remaining in the cartridge is small, the entire toner is replenished into the associated hopper and fully consumed.

Abstract: An image forming apparatus having a rotary developing device or revolver in which a plurality of developing sections are defined. The revolver is rotated over a target position by a first drive source, then returned by a second drive source producing a moment acting in the opposite direction, such as due to the drive of one of the developing sections, and then positively stopped by a positioning mechanism. The revolver is, therefore, accurately positioned at the target position without regard to, for example, irregularities in a motor for driving the revolver.

Abstract: A developing unit incorporated in an image forming apparatus and capable of transporting a developer or a toner deposited on a developing roller in a predetermined direction without rotating the developing roller, or developer carrier. The developing roller has an unrotatable base roller, a stationary body provided on the base roller and made of an insulating material, and a plurality of drive electrodes buried in the stationary body. The drive electrodes are divided into three electrode groups. Voltages whose polarities change at predetermined intervals are applied to the three electrode groups, causing the toner to be transported by the coaction of the charge of the toner and the charges of the drive electrodes. The drive electrodes are arranged at a pitch which is substantially one-third of the particle size of the toner, so that the toner may be deposited on the developing roller substantially without any clearance.

Abstract: An image forming apparatus having various process units at least one of which is removable for replacement. The apparatus has a mode selecting a device accessible for selecting desired one of a plurality of image modes. A photoconductive element, developing unit, image transferring unit and other replaceable process units each is provided with a storage for storing image forming conditions which match an image mode selected on the mode selecting device. A copy process and other conditions are set up on the basis of the conditions stored in the storage. Another storage is loaded with data associated with the service life of a replaceable process unit.

Abstract: A developing apparatus has a developer cartridge having a first developer storage room for storing an unused new developer, a second developer storage room for storing a used old developer, and shutter members for opening and closing openings of the first and second developer storage rooms; and a device for detachably attaching the developer cartridge to a section for exchanging the old developer for the new developer on a body side of the developing apparatus. The developer cartridge may be attached and detached from the developer exchanging section after deterioration of the developer in use is displayed, and the used developer is collected within the second developer storage room and the new developer is supplied into the developer cartridge after the collection of the used developer.