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IPC Subgroup
E21D 11/02

Lining predominantly with wood

Introduced: September 1968

Last revised: January 2006

Full Title

Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings , e.g. by assembling > Lining predominantly with wood

Classification Context

Section:
FIXED CONSTRUCTIONS
Class:
EARTH OR ROCK DRILLING; MINING
Subclass:
SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS

Filing statistics

IPC E21D 11/02 belongs to the parent subclass E21D, which recorded 106,833 patent applications worldwide between 2013 and 2023. Annual filings grew from 4,236 in 2013 to 15,272 in 2023 (+261%). The most active applicants in class E21 are HALLIBURTON ENERGY SERVICES GROUP (26,607 applications), PETROCHINA COMPANY (14,382 applications) and SINOPEC (CHINA PETROCHEMICAL CORPORATION) (10,137 applications).

Source: EPO PATSTAT, worldwide filings

1 direct subcode

Child Classifications

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Top Applicants

Top 10 applicants by patent filingsfor class E21, 2013–2023, worldwide · Source: EPO PATSTAT

  1. HALLIBURTON ENERGY SERVICES GROUP US 26,607
  2. PETROCHINA COMPANY 14,382
  3. SINOPEC (CHINA PETROCHEMICAL CORPORATION) 10,137
  4. CNPC (CHINA NATIONAL PETROLEUM CORPORATION) 6,517
  5. BAKER HUGHES US 6,269
  6. SCHLUMBERGER TECHNOLOGY US 5,929
  7. SAUDI ARABIAN OIL COMPANY SA 5,880
  8. SOUTHWEST PETROLEUM UNIVERSITY 4,477
  9. CHINA UNIVERSITY OF MINING AND TECHNOLOGY 4,357
  10. SCHLUMBERGER TECHNOLOGY NL 4,219