Granted Patent
Utility
US 4,770,387 · App. 06/922,859
Variable ram seal for blowout preventers
Inventor:
Stanley W. Granger
Patented Case
View Patent ↗
Granted: Sep 13, 1988
Filed: Oct 24, 1986
Inventor
Stanley W. Granger
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.