CALENDERS; ACCESSORIES FOR PAPER-MAKING MACHINES (winders or rewinders for finished products, means for adjustment of wrinkles or lateral extensions B65H)

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

CPC subclass D21G recorded 3,891 patent applications worldwide between 2013 and 2023. Annual filings grew from 292 in 2013 to 299 in 2023 (+2%), peaking at 419 applications in 2016. The most active applicants in class D21 are VOITH PATENT (1,857 applications), STORA ENSO (1,552 applications) and KEMIRA (1,173 applications).

Source: EPO PATSTAT, worldwide filings