Granted Patent
Utility
US 4,874,313 · App. 07/248,678
Refractory clad lid for heating vessel
Inventor:
Ronald L. Schwenninger
Patented Case
View Patent ↗
Granted: Oct 17, 1989
Filed: Sep 26, 1988
Inventor
Ronald L. Schwenninger
Assignee (at issue)
PPG Industries, 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.