DIFF Subgroup
E21B 4/20 combined with surface drive (E21B4/10 takes precedence)
Introduced: January 1980
Title
Titles differ between systems:
IPC: combined with surface drive
CPC: combined with surface drive (E21B4/10 takes precedence)
Full Title
Full titles differ between systems:
IPC:
Drives for drilling, used in the borehole > combined with surface drive
CPC:
Drives for drilling, used in the borehole > combined with surface drive (E21B4/10 takes precedence)
No child classifications to compare. This is a leaf node in both IPC and CPC.