Granted Patent
Utility
US 4,566,671 · App. 06/551,589
Gate valve having a secondary seal
Inventor:
John Beson
Patented Case
View Patent ↗
Granted: Jan 28, 1986
Filed: Nov 14, 1983
Inventor
John Beson
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.