Granted Patent
Utility
US 4,579,351 · App. 06/708,216
Dual spring expander for oil control piston rings
Inventor:
Vernon M. Daffron
Patented Case
View Patent ↗
Granted: Apr 1, 1986
Filed: Mar 5, 1985
Inventor
Vernon M. Daffron
Assignee (at issue)
TRW Automotive Products 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.