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CPC technology class · D21

D21G - Calenders

Calenders; accessories for paper-making machines. 371 US utility patents granted 2015–2025, with the leading assignees and year-by-year grant trajectory.

371
US patents granted
#5/7
in D21
4.5%
D21 class share
+5%
5-yr velocity

The verdict

According to USPTO PatentsView, Calenders ranks #568 of 670 CPC technology areas - 371 US patents granted since 2015, with recorded grant volume up 5% over five years.

#568
of 670 CPC technology areas
371
US patents granted, 2015–2025
Seiko Epson
leading assignee (51)
+5%
grant velocity, last 5 yrs

How D21G's grant cadence moved

Between 2020–2024, D21G recorded 177 grants versus 168 in 2015–2019 (+5% equal-window velocity). Across complete years, output peaked in 2019 at 45 grants and bottomed in 2015 at 23 (+96% peak-over-trough). Lead assignee Voith Patent GmbH holds 5.9% of the class ; the top three share 14.6%.

Leaderboard read

D21G concentration, lead at 5.9%

Voith Patent GmbH leads this historical grant record at 5.9% of D21G - foreign corporation assignees hold 51% of class grants (102 of 200). Figures describe granted US utility patents in this CPC subclass, not current investment or legal strength.

Leader's share
5.9%

22 of 371 grants

Top three share
14.6%

of the class's recorded grants

Lead over #2
4

more grants than Gpcp IP Holdings LLC

Where D21G sits inside D21

Among 7 subclasses in D21 (PAPER-MAKING; Production OF Cellulose), D21G ranks #5 and holds 4.5% of the parent class's 8,169 recorded grants. Sibling chips below are the other subclasses in the same parent class, not the nationwide volume/lead-share peers further down.

D21H 4,080 D21C 1,427 D21F 1,255 D21B 452 D21D 314 D21J 270

Rising assignees active in D21G

Company-wide grant multiples (2022–2024 vs 2019–2021) among assignees with ≥5 patents in this subclass. Growth is company-wide; class patent counts are subclass-specific.

  1. #1 Andritz Kuesters GMBH 7.00x 1 → 7 company-wide · 6 in D21G
  2. #2 Industrial Video Solutions Inc. 5.00x 0 → 5 company-wide · 5 in D21G
  3. #3 IBS of America 1.67x 3 → 5 company-wide · 6 in D21G
  4. #4 Valmet Technologies Oy 1.52x 29 → 44 company-wide · 9 in D21G
  5. #5 Valmet Technologies, Inc. 1.25x 8 → 10 company-wide · 11 in D21G

D21G grants by year, peak 2019 (45)

US utility-patent grants per year in D21G, 2015–2025 - recent five years are up 5% versus 2015–2019.

20253035404550 20152016201720182019202020212022202320242025 25

Who leads D21G?

The 12 most active assignees in CALENDERS; Accessories FOR Paper-making Machines - wider bars mean more grants

patents

What this shows Seiko Epson is the most active filer in D21G, holding 51 of the 371 patents in this class. Concentration at the top signals how contestable this technology area is for new entrants.

Source USPTO PatentsView, granted utility patents As of 2015–2025 grant years
View data table
Top patent holders in CPC subclass D21G
Rank Company Patents in D21G
#1 Voith Patent GmbH 22
#2 Gpcp IP Holdings LLC 18
#3 International Paper Company 14
#4 Valmet Technologies, Inc. 11
#5 Andritz Inc. 9
#6 Valmet Technologies Oy 9
#7 Honeywell Limited 9
#8 Brunn Air Systems, Inc. 9
#9 Stowe Woodward Licensco LLC 8
#10 Georgia-Pacific Consumer Products LP 7
#11 Valmet Automation OY 6
#12 IBS of America 6
#13 Andritz Kuesters GMBH 6
#14 Kadant Inc. 6
#15 Procemex Oy 6
#16 Honeywell ASCa 5
#17 Industrial Video Solutions Inc. 5
#18 Valmet Aktiebolag 4
#19 Buckman Laboratories International, Inc. 3
#20 Structured I, LLC 3

Footprint here vs. claim strategy

Each dot is a leading D21G assignee, placed by how many patents it holds in this class (horizontal) against its company-wide average claims per patent (vertical) - a read on whether the class is led by broad-but-shallow filers or focused deep-claim players.

Top 14 D21G assignees by class footprint. Bubble size = patents in D21G. Source: USPTO PatentsView (claim depth is company-wide across all classes). Scatter plot of 14 data points (bubble-sized by third dimension). 10152025 510152025 Patents in D21G Avg claims / patent (company-wide) Voith PatentGpcp Ip HoldingsInternational PaperValmetAndritzValmet OyHoneywellBrunn Air SystemsStowe Woodward…Georgia-pacific…Valmet Automation OyIbs of AmericaAndritz KuestersKadant
Top 14 D21G assignees by class footprint. Bubble size = patents in D21G. Source: USPTO PatentsView (claim depth is company-wide across all classes).

Questions about D21G

Which company holds the most patents in D21G?
Seiko Epson Corporation leads D21G with 51 patents (5.9% of the subclass). By PatentsView assignee type, foreign corporations account for 51% of class grants.
Which D21G assignees grew fastest recently?
Among assignees with ≥5 grants in D21G, Andritz Kuesters GMBH shows the highest company-wide grant multiple (7.00x: 1 grants in 2019–2021 → 7 in 2022–2024) while holding 6 patents in this subclass. Growth is company-wide, not class-only.
How does D21G compare inside parent class D21?
Inside D21 (PAPER-MAKING; Production OF Cellulose), D21G ranks #5 of 7 subclasses by grant volume and holds 4.5% of the parent class total. The largest sibling is D21H (4,080 grants).

What to do with this data

D21G in context - here's where to go next.

Figures reflect USPTO PatentsView grant data through 2026-05-15; pending applications not yet granted are not counted.

Methodology - D21G figures are USPTO PatentsView granted-utility totals for this subclass (371 grants in the tracked window).

Every figure on PlainPatent is rendered directly from USPTO source data, no number is typed in by an editor. This page draws directly on USPTO source data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.