Granted Patent
Utility
US 4,377,472 · App. 05/956,701
Phosphate flotation
Inventor:
Howard Allen
Patented Case
View Patent ↗
Granted: Mar 22, 1983
Filed: Nov 1, 1978
Inventor
Howard Allen
Assignee (at issue)
W. R. Grace & Co.
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.