Separating arrangement

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.

1 . Arrangement for the separation of an end sheet ( 2 ′) from a group of parallel sheets, which overlap each other, and has been fed from a stack of sheets, the separating arrangement comprising 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 characterized in that, at the roller nip, the envelope surface of the second roller is arranged rotatable in a rotational direction opposite to the rotational direction of the envelope surface of the first roller, that the envelope surface of the first roller has a higher friction coefficient than the second roller, that 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. 
     
     
         2 . Separating arrangement according to  claim 1 , characterized in that the rollers are mutually biased by a displacement arrangement that is drivable to apply a selected mutual bias force between the rollers, substantially independently of an axial distance alteration between the rollers produced by wear, that means are provided for suspension of or reversal of the action direction of the displacement arrangement, in order to allow the rollers to separate for letting through a group of sheets that cannot be separated and thereby otherwise cannot pass through the roller nip, that a sensor is situated upstream of the pair of rollers and is arranged to detect the presence of a group of sheets comprising at least one sheet, and that evaluation members are provided in order to bring the bias arrangement to allow the sheaf of sheets to pass after a predetermined period of time of a sheet-presence signal from the sensor. 
     
     
         3 . Separating arrangement according to  claim 1 , characterized in that the bias arrangement comprises a linear solenoid, a small fraction of its maximal stroke length of which is made use of in order to compensate for wear of the mutual abutment surfaces of the rollers, whereby the applied bias force is essentially constant within said portion of the interval and the alteration of the axial distance of the rollers that is allowable in view of the wear. 
     
     
         4 . Separating arrangement according to  claim 3 , characterized by means for varying the driving power of the solenoid for controlling the bias force of the solenoid, the means comprising an arrangement to vary the current feed of the solenoid at a constant voltage, whereby the bias force is substantially proportional to the feed current. 
     
     
         5 . Separating arrangement according to  claim 1 , characterized in that a second sensor is arranged downstream of the pair of rollers and that the second sensor is arranged to distinguish between an individually passing sheet and a group of sheets, and that the second sensor is arranged to direct a diversion arrangement to divert a group of sheets having passed the roller nip to a store, and that the diversion arrangement is arranged to allow an individual sheet to pass to a transportation for forwarding.