Granted Patent
Utility
US 4,974,911 · App. 07/378,358
Vent valve device
Inventor:
James E. Hart
Patented Case
View Patent ↗
Granted: Dec 4, 1990
Filed: Jul 11, 1989
Inventor
James E. Hart
Assignee (at issue)
American Standard 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.