Granted Patent
Utility
US 4,890,674 · App. 07/285,517
Flapper valve protection
Inventor:
Nam V. Le
Patented Case
View Patent ↗
Granted: Jan 2, 1990
Filed: Dec 16, 1988
Inventor
Nam V. Le
Assignee (at issue)
Otis Engineering Corporation
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.