Granted Patent
Utility
US 4,288,969 · App. 06/135,841
Stone trap seal
Inventor:
Kenneth R. Underhill
Patented Case
View Patent ↗
Granted: Sep 15, 1981
Filed: Mar 31, 1980
Inventor
Kenneth R. Underhill
Assignee (at issue)
Sperry Corp.
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.