Granted Patent
Utility
US 4,481,121 · App. 06/617,141
Viscosifier for oil base drilling fluids
Inventor:
Horst K. F. Barthel
Patented Case
View Patent ↗
Granted: Nov 6, 1984
Filed: Jun 4, 1984
Inventor
Horst K. F. Barthel
Assignee (at issue)
Hughes Tool Company LLC
This patent predates the USPTO's electronic file wrapper — prosecution documents from this era exist only in the Patent Office's paper records. A certified copy of the file history can be ordered from the USPTO's paper archives.