Granted Patent
Utility
US 4,813,481 · App. 07/089,979
Expendable flapper valve
Inventors:
Richard M. Sproul, Frank Giusti, Jr., Richard L. Grant, Kennedy J. Brown
Patented Case
View Patent ↗
Granted: Mar 21, 1989
Filed: Aug 27, 1987
Inventors
Richard M. Sproul
Frank Giusti, Jr.
Richard L. Grant
Kennedy J. Brown
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.