Granted Patent
Utility
US 4,305,673 · App. 06/134,018
High efficiency mixing impeller
Inventor:
Norman R. Herbst
Patented Case
View Patent ↗
Granted: Dec 15, 1981
Filed: Mar 25, 1980
Inventor
Norman R. Herbst
Assignee (at issue)
Federal Signal 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.