Granted Patent
Utility
US 4,452,272 · App. 06/236,645
Check valve
Inventor:
David Griswold
Patented Case
View Patent ↗
Granted: Jun 5, 1984
Filed: Feb 23, 1981
Inventor
David Griswold
Assignee (at issue)
Griswold Controls, LLC
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.