Granted Patent
Utility
US 4,421,976 · App. 06/296,666
System for monitoring heater elements of electric furnaces
Inventor:
John J. Jurek
Patented Case
View Patent ↗
Granted: Dec 20, 1983
Filed: Aug 26, 1981
Inventor
John J. Jurek
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.