Granted Patent
Utility
US 4,893,390 · App. 07/239,348
Method and expander for manufacturing a furnace heat exchanger and plate assembly
Inventor:
Russell W. Hoeffken
Patented Case
View Patent ↗
Granted: Jan 16, 1990
Filed: Sep 1, 1988
Inventor
Russell W. Hoeffken
Assignee (at issue)
Snyder General 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.