Abstract: A method of controlling a solenoid for controlling the force thereof, and a controllable force transducer includes that only a small part of the maximal stroke length of the solenoid is utilized, whereby the exerted force thereof is substantially constant within said stroke-length distance, when the solenoid is fed with a constant driving power. At a constant driving voltage, the feed current can be controlled for a proportional alteration of the exerted force of the solenoid within said stroke-length distance. The controller finds favourable use in a sheet separator.

Abstract: A method and an arrangement for feeding out end sheets from a stack of sheets comprises that a driver acting against the end sheet of the stack (1) first displaces the end sheet in the plane thereof toward a support for elastic bulging of the end sheet, and then displaces the buckled end sheet away from the support, to a separating arrangement for the separation of sheets that unintentionally are accompanying the end sheet (21) fed out. The driver being carried by a spring arrangement, which offers an increasing support force to the driver upon the advancement of the stack by means of a pusher acting against the rear end of the stack. A sensor detects the displacement position of the driver, and activates the driver for a sheet-outfeed operation when the distance sensor detects a displacement position of the driver corresponding to a predetermined abutment force of the driver against the end sheet. Between the sheet-outfeed operations, the pusher is unloaded.

Abstract: An arrangement for the separation of an end sheet (21) from a group of parallel sheets overlapping each other comprises a pair of parallel rotatable rollers, which between themselves form a roller nip, the group of sheets moving in the plane thereof toward the roller nip with heading edges substantially parallel to the rollers, and a first one of the rollers being arranged to rotate in a first direction in order to contact and convey the end sheet (2?) in the feed direction thereof. The second roller is arranged rotatable in the same rotational direction as the first roller. The envelope surface of the first roller has a higher friction coefficient than the second roller. A displacement arrangement is arranged to mutually bias the rollers into contact against each other, and that the rollers are mutually directed for the displacement toward and away from each other.