front pressing device 4 or a back pressing device 5 against the middle roll 2 the rotational axis a 2 of which is fixed in place the front roll 1 and back roll 3 are movable i e their rotational axes a 1 and a 3 can be pivoted around a swiveling axis d 3 the jacket surfaces of rolls 1 2 3 each comprise the roll processing surface s 1 s 2 s 3 with which the product to be processed comes into contact during operation the product passing between the rolls 1 and 2 pressed against each other creates a roll nip between the processing surface s 1 of the front roll 1 and the processing surface s 2 of the middle roll 2 in like manner the product passing between the rollers 2 and 3 pressed against each other creates a roll nip during operation between the processing surface s 3 of the back roll 3 and the processing surface s 2 of the middle roll the front pressing device 4 and back pressing device 5 each have a force transducer 6 and a pneumatic drive 7 in the first exemplary embodiment shown on fig1 the force transducer is a toggle mechanism 6 which consists of a first lever 6 a and a second lever 6 b while the pneumatic drive 7 consists of a pneumatic cylinder 7 a and a pneumatic piston the force exerted by the pressing devices 4 and 5 flows from the pneumatic piston 7 b which is accommodated in the pneumatic cylinder 7 a and linked with the first lever 6 a on an articulated axis d 1 by means of a piston rod 7 b the first lever 6 a is hinged to a second articulated axis d 2 on.