Abstract: A sheet feeder for sheet-processing machines having a positively driven, gripping mechanism which travels over at least two deflection wheels including at least one sheet-transporting gripper which is opened or closed during the course of travel through a revolving path. A number of toothed belts can be used; each belt includes a plurality of spaced aparet recesses into which a support body carrying a gripper mechanism is removably inserted. The deflection wheels are provided with circumferential recesses which correspond to an inwardly protruding part of the support body of the gripper mechanism in the form of an actuating lever that is actuated on striking or leaving a cam race, which may be part of the circumferential recesses of the deflection wheels.