Abstract: Formed between an opposing electrode and a toner support by a high voltage applied from a high-voltage power source is an electric field required for the toner carried on the toner support to jump toward the opposing electrode. The high-voltage power source and the duration of voltage application are adjusted so as to pick out suitable developer particles to be used for forming images.

Abstract: In a system having a developer support, an opposing member arranged facing the developer support, the process conditions including the property of the developer are adapted to satisfy the following relation:.DELTA.V/d=E>5.5-10.times..DELTA.AD,where .DELTA.V is the potential difference between the developer support and opposing member, d is the distance between the developer support and opposing member, AD is the bulk density of the developer, and E is the electric field strength which is calculated from the potential difference .DELTA.V and the distance d between the developer support and opposing member.

Abstract: An object of the present invention is to provide an image forming apparatus for enabling toner to easily pass through gates of control electrode and increasing the scattering efficiency of the toner to improve the printing quality. Since a sticking force between the toner and toner holder or among particles thereof is weakened and the toner is held on the toner holder with a slight binding force between the toner holder and the control electrode, a voltage applied for enabling the toner to pass through the gates of the control electrode and scatter toward the counter electrode can be minimized as long as the toner can pass through the gates of the control electrode. In other words, a pulse is applied to a shielded electrode just before the toner held on the toner holder passes through the gates of the control electrode, so that the sticking force between the toner and the toner holder or among particles thereof can be weakened, or the toner can be transformed into cloud-like particles.

Abstract: An image forming apparatus has a photoreceptor drum and a developing roller supported in the developing unit for retaining and conveying the developer, and further has a sealed viscous fluid damper having a viscous fluid sealed therein, arranged coaxially with the rotary shaft of the photoreceptor drum.

Abstract: An image forming apparatus includes an opening and closing member mounted to an apparatus main body so that it can be open and closed, and a head cover for protecting the surface of a control electrode when opening the opening and closing member without disturbing an operation of controlling the flying of a toner by the control electrode in a closed state of the opening and closing member as being moved interlocking with opening and closing operations of the opening and closing member. According to the described arrangement, when the opening and closing member is open to remove a jammed sheet, exchange a toner cartridge, carry out various checking for printing inferior or install and remove a unit including the control electrode with respect to the apparatus main body, the control electrode which would be exposed otherwise can be prevented from being touched with an operator's finger or other member of the apparatus, etc.

Abstract: A toner producing system which can efficiently produce toner having a sharp particle size distribution by suppressing the occurrence of microscopic powders and improve energy efficiency in pulverization. The system is furnished with a second pulverizing apparatus having a second colliding plate inclined at an angle in a range between 45.degree. and 90.degree. inclusive with respect to a direction in which a raw material subject to pulverization is introduced into a second pulverizing chamber through a second nozzle, and a third pulverizing apparatus having a third colliding plate with a conical member being placed thereon, so that the raw material introduced into a third pulverizing chamber through a third nozzle collides with an inner surface thereof following the collision with the third colliding plate.

Abstract: A two-component developer for electrophotography includes a toner comprising toner particles and an external additive composed of a compound of imidazole series or an imidazole derivative. The external additive has a volume median particle size below that of the toner particles, or of 0.1 to 100 .mu.m. The amount of external additive is 0.001 to 5% by weight based on the weight of the toner particles. As a result, scattering of toner may be prevented and the formation of fog in the background may be reduced. In addition, the electrostatic charge characteristics of the toner may be improved and the electrostatic charge rises in a satisfactory manner.

Abstract: A set of electrophotographic toners used for electrophotographic machines are disclosed which comprise an initial supply toner and a supplementary toner, both of which are composed of toner powder and additives adhering to the surface of the toner powder, wherein the weight ratio x of additives to toner powder in the initial supply toner is set to be greater than the weight ratio y of additives to toner powder in the supplementary toner.