Granted Patent
Utility
US 4,581,521 · App. 06/674,694
Electrically heated pipe assembly
Inventor:
Frederick G. J. Grise
Patented Case
View Patent ↗
Granted: Apr 8, 1986
Filed: Nov 26, 1984
Inventor
Frederick G. J. Grise
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.