Abstract: A sheet feeder incorporated in an image forming apparatus and allowing the distance between the preceding sheet and the succeeding sheet to be reduced to a minimum necessary one. A pair of control rollers whose transport speed is controllable are located upstream of an image forming section with respect to an intended direction of sheet transport. An image transfer and paper separation unit is located at the image forming section. The transport speed of the control rollers is made higher than an image forming speed for any desired period of time after the leading edge of a sheet has been gripped by said control rollers and before the leading edge reaches the image forming section. As a result the distance between the preceding and succeeding sheets is reduced to increase the number of images which can be formed for a unit time without the transport speed at the image forming section being increased.

Abstract: A developing unit includes a housing frame containing toner and having an opening; a developing roller rotatably mounted on the housing frame so as to face the opening of the housing frame; a thin blade which is in contact with a surface of the developing roller and scrapes off the toner adhered to the surface of the developing roller so that a thin toner layer is formed on the surface of the developing roller, the toner being supplied from the thin toner layer to a photosensitive belt: and a sealing sheet for sealing a continuous gap formed of a first gap between each end of the developing roller and the housing frame and a second gap between each end of the thin blade and the housing frame, the sealing sheet being divided into a first sealing sheet for sealing the first gap and a second sealing sheet for sealing the second gap.