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IPC Subgroup
E21D 11/4

Devices or apparatus specially adapted for handling or placing units of linings for tunnels or galleries

Introduced: July 1974

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 > Devices or apparatus specially adapted for handling or placing units of linings for tunnels or galleries

Classification Context

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

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