CALENDERS; ACCESSORIES FOR PAPER-MAKING MACHINES

Description

D21G encompasses calendering equipment used in paper manufacturing to compress, smooth, and finish paper sheets, along with auxiliary devices integrated into papermaking lines. This includes calender rolls, nip structures, heating systems, and control mechanisms for regulating pressure, temperature, and sheet feed to achieve desired paper properties such as thickness uniformity, gloss, and density. The classification covers both standalone calendering units and machine components designed specifically to support the calendering process within integrated paper production systems.

Filing statistics

IPC subclass D21G recorded 4,256 patent applications worldwide between 2013 and 2023. Annual filings grew from 341 in 2013 to 352 in 2023 (+3%), peaking at 479 applications in 2020. The most active applicants in class D21 are VOITH PATENT (1,809 applications), STORA ENSO (1,467 applications) and KEMIRA (1,086 applications).

Source: EPO PATSTAT, worldwide filings