Sheet of fibrous material comprising an annular window and method of manufacturing same

摘要

The fibrous material sheet comprises an annular window (10) formed by an annular film segment (4) having an internal edge (6) and an external edge (7) trapped in the fibrous material. The annular film segment has perforations along the edge. The edge of the annular film segment is toothed. The toothed edge has tooth in slots and triangular tooth. An independent claim is included for a method for the production of fibrous material sheet.