Granted Patent
Utility
US 4,274,186 · App. 06/080,241
Heat exchanger
Inventor:
William L. Pringle
Patented Case
View Patent ↗
Granted: Jun 23, 1981
Filed: Oct 1, 1979
Inventor
William L. Pringle
Assignee (at issue)
United States Steel Corporation
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.