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PCE
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DIFF Subgroup
D21D 1/20

Methods of refining

Introduced: September 1968

Full Title

Full titles differ between systems:

IPC:

Methods of beating or refining; Beaters of the Hollander type > Methods of refining

CPC:

Methods of beating or refining; Beaters of the Hollander type (knotter screens D21F) > Methods of refining

IPC and CPC are identically structured here. All 6 subcodes exist in both systems.

Child Classifications

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  • D21D 1/28 Ball or rod mills IPC+CPC Available in IPC and CPC
  • D21D 1/32 Hammer mills IPC+CPC Available in IPC and CPC
  • D21D 1/40 Washing the fibres IPC+CPC Available in IPC and CPC

Top Applicants

Top Applicants (IPC)

Class D21,2013–2023, worldwide · Source: EPO PATSTAT

  1. VOITH PATENT DE 1,809
  2. STORA ENSO FI 1,467
  3. KEMIRA FI 1,086
  4. KIMBERLY-CLARK CORPORATION US 935
  5. VALMET TECHNOLOGIES FI 924
  6. VALMET SE 904
  7. P&G (PROCTER & GAMBLE COMPANY) US 862
  8. OJI HOLDINGS CORPORATION 696
  9. OMYA INTERNATIONAL CH 584
  10. SOUTH CHINA UNIVERSITY OF TECHNOLOGY 571

Top Applicants (CPC)

Class D21,2013–2023, worldwide · Source: EPO PATSTAT

  1. VOITH PATENT DE 1,857
  2. STORA ENSO FI 1,552
  3. KEMIRA FI 1,173
  4. KIMBERLY-CLARK CORPORATION US 1,107
  5. VALMET TECHNOLOGIES FI 965
  6. VALMET SE 943
  7. P&G (PROCTER & GAMBLE COMPANY) US 941
  8. OMYA INTERNATIONAL CH 821
  9. UPM-KYMMENE CORPORATION FI 512
  10. SEIKO EPSON CORPORATION JP 501