Abstract: A calendering device has a plurality of pressure rollers and an opposing plurality of counterpressure rollers, each rotatably mounted on a piston rod movable in a direction for permitting the pressure rollers and counterpressure rollers to approach one another to calender a product. The pistons of the piston rods are mounted within pneumatic casings and are moved by a diaphragm within the pneumatic casings. There is no contact between the pistons and the walls of the pneumatic casings, thereby reducing the frictional resistance to the movement of the rollers. Means are provided for equalizing the pressure applied to a roller and its corresponding counter roller. Separate pneumatic casings and diaphragms may be provided for each piston rod, or several of the pressure rollers or countepressure rollers may be moved by a single diaphragm, which can be in the form of an elongated hose.

Abstract: To cover the concave face of a lens preform with a protective sheet of transparent plastic by an elastic pressing element, the invention proposes inserting an elastic membrane between the pressing element and the protective sheet. Before or during pressing, the membrane is lowered over the preform which has been provided with the protective sheet. As a result of its presence, the entire peripheral area of the protective sheet can be applied homogeneously against the edge of the preform.

Abstract: A calendering device has a plurality of pressure rollers and an opposing plurality of counterpressure rollers, each rotatably mounted on a piston rod movable in a direction for permitting the pressure rollers and counterpressure rollers to approach one another to calender a product. The pistons of the piston rods are mounted within pneumatic casings and are moved by a diaphragm within the pneumatic casings. There is no contact between the pistons and the walls of the pneumatic casings, thereby reducing the frictional resistance to the movement of the rollers. Means are provided for equalizing the pressure applied to a roller and its corresponding counter roller. Separate pneumatic casings and diaphragms may be provided for each piston rod, or several of the pressure rollers or counterpressure rollers may be moved by a single diaphragm, which can be in the form of an elongated hose.