Granted Patent
Utility
US 5,137,261 · App. 07/533,446
Ported gate valves, method and apparatus
Inventor:
Walter A. Clifford
Patented Case
View Patent ↗
Granted: Aug 11, 1992
Filed: Jun 5, 1990
Inventor
Walter A. Clifford
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.