Abstract: A developing device used in an image forming apparatus has a developing roller at a lower opening of a toner hopper, and the developing roller contacts a photosensitive drum to form a developing portion therebetween. The hopper stores nonmagnetic toner and is provided with a toner stirring member and a toner feed roller being in press-contact with the developing roller in a lower part of the hopper. A doctor blade contacts a circumferential surface of the developing roller on an upstream side of the developing portion in a rotation direction of the drum. A conductive scooping sheet contacts the circumferential surface of the developing roller on a downstream side of the developing portion. A residual toner not used to develop a latent image on the drum and left on the developing roller is passed under the sheet into the hopper with the rotation of the developing roller.

Abstract: A roller-shaped contact charging member which is in contact with and electrically charges a photosensitive drum is provided on a center shaft, and includes a roller-shaped conductive foam material portion covering the shaft, and a tubular-shaped conductive resin material portion covering the foam portion. The foam portion has an electric resistance of 9.times.10.sup.5 .OMEGA. or less, the resin portion includes conductive agents and has a surface electric resistance in a range from 1.times.10.sup.5 .OMEGA./.quadrature. or more to 9.times.10.sup.7 .OMEGA./.quadrature. or less, and a hardness of the charging roller as a whole is Asker F 90.degree. or less. An image forming unit includes the charging member and the drum. An electrophotographic image forming apparatus supplies a recording paper to the unit, transfers an image from the drum to the paper, and discharges the image-transferred paper.

Abstract: A motor starts its rotation, and a clutch is operated to drive both of a first driving force transmission system for color printing, including drum gears, and a second driving force transmission system for monochrome printing, including a drum gear. The clutch is disengaged to stop the first system when a first sensor detects a mark on one photosensitive drum of the first system at the same time that a second sensor detects a mark on one drum driving gear of the first system. Next, when a third sensor detects a mark on another photosensitive drum of the second system at the same time that a fourth sensor detects a mark on another drum driving gear of the second system, the clutch is reengaged. Consequently, positionings of all the photosensitive body drums (drum gears) for color printing to the photosensitive drum (drum gear) for monochrome printing are performed without causing positional differences by inertia at the time of stop.

Abstract: An image forming apparatus has four color image forming and transferring portions and four image writing heads supported by a cover to be rotatably movable upwardly and downwardly. Each case of the portions is so shaped that it does not interfere with the rotational movement of the heads, and has the same shape. Particularly, two opposite side surfaces of the case is so shaped that it does not project into the movement locuses of the heads not to collide them.

Abstract: A toner collector includes a tube having at least one opening in an intermediate portion between both end portions, one of the both end portions being closed, a toner collecting bag covering the tube, and connected to the tube at the both end portions of the tube, and a waste toner transfer member, connected to the other of the both end portions of the tube, for transferring toner to the other of the both end portions from an outer side of the tube.

Abstract: A developer circular unit is detachably set in a copier or a copier type printer which print on images on a paper sheet with toner. The unit includes at least a developing device, a cleaner, and a developer conveying device having a pipe communicated with both the cleaner and the developing device and a toner flowing-back preventing mechanism. The action of the mechanism is automatically released by the first set of the unit in the copier or printer and/or the first use of the copier or printer after that first set.