Lining predominantly with metal

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 metal

Classification Context

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

6 direct subcodes

Child Classifications

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E21D 11/15 Plate linings; Laggings, i.e. linings designed for holding back formation material or for transmitting the load to main supporting members
E21D 11/18 Arch members
E21D 11/28 Longitudinal struts
E21D 11/3 Bases for lower arch members
E21D 11/34 Joints between vertical props and horizontal top bars
E21D 11/36 Linings or supports specially shaped for tunnels or galleries of irregular cross-section

Top Applicants

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

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