Granted Patent
Utility
US 4,331,450 · App. 06/184,813
Coal gasification plant slag tapping process
Inventor:
Richard Elliott
Patented Case
View Patent ↗
Granted: May 25, 1982
Filed: Sep 8, 1980
Inventor
Richard Elliott
Assignee (at issue)
British Gas
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.