Patterned flat plastic film production, in particular for linear Fresnel lenses, involves passing melt strip between belts which move around a forming roll followed by cooling plates

摘要

An extruded plastic strip(9) runs between two synchronously moving endless metal belts(1,4) running around part of a forming roll(5) and enters a cooling station with two flat cooling plates(11,12). The cooling plates compress the melt strip while cooling and an engraved pattern on one of the belts is impressed into the surface of the plastic strip. The melt strip(9) is pressed towards the forming roll(5) by an endless tensioning belt(4). Roll temperature is similar to that of the melt strip. In a process variation the melt strip may be prefabricated and is passed between heaters to soften before entering the compression gap between the belts. When forming a pattern on both sides of the plastic strip, both belts are engraved and one acts as a tensioning belt. Cooling plates may be internally cored for cooling fluid or have bores through which pressurized water flows to meet the rear face of the belts. An independent claim is included for the process plant which has two or more pairs of rolls and the tensioning belt(4) and engraving belt(1) run around part of the forming roll(5) surface.