Granted Patent
Utility
US 4,298,061 · App. 06/178,338
Heat exchanger with crimped flange seam
Inventor:
Russell W. Hoeffken
Patented Case
View Patent ↗
Granted: Nov 3, 1981
Filed: Aug 15, 1980
Inventor
Russell W. Hoeffken
Assignee (at issue)
The Singer Company Limited
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.