Granted Patent
Utility
US 4,248,264 · App. 06/108,368
Internal mud saver valve
Inventors:
William R. Hadsell, Tosh Miyagishima
Patented Case
View Patent ↗
Granted: Feb 3, 1981
Filed: Dec 31, 1979
Inventors
William R. Hadsell
Tosh Miyagishima
Assignee (at issue)
Hydril Company
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.