Method and device for producing security paper with window security thread

摘要

The invention relates to a circular sieve (12) of a circular sieve paper machine (10) for the production of security paper (42A, 42B) with a partially embedded window security thread (22), the circular sieve (12) during paper manufacture being a pulp in the form of fiber water -Suspension (14) scoops from a chest (16), and wherein the circular screen (12) contains a production screen jacket (30) with a circumferential direction (U) and a perpendicular transverse direction (Q) which along the circumferential direction (U) with a A plurality of raised thread window elements (34) is provided, on which the window security thread (22) rests during paper production in order to locally suppress the deposition of fiber-water suspension (14) to produce thread windows (40). According to the invention, the thread window elements (34) are arranged with a periodic offset (36) in the transverse direction (Q) along the circumference, the circular sieve circumference Ru being an integral multiple of the displacement period P. The invention also includes an associated method for the production a security paper.