Granted Patent
Utility
US 5,988,604 · App. 08/948,558
Mixing impellers especially adapted for use in surface aeration
Inventor:
John R. McWhirter
Patented Case
View Patent ↗
Granted: Nov 23, 1999
Filed: Oct 10, 1997
Inventor
John R. McWhirter
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.