Granted Patent
Utility
US 4,269,279 · App. 06/111,681
Spheroidal plastic coated magnetizable particles and their use in drilling fluids
Inventor:
Roy F. House
Patented Case
View Patent ↗
Granted: May 26, 1981
Filed: Jan 14, 1980
Inventor
Roy F. House
Assignee (at issue)
NL Industries, Inc.
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.