Granted Patent
Utility
US 4,956,975 · App. 07/395,324
Shutoff valve for cryogenic liquid storage tank
Inventor:
Keith Gustafson
Patented Case
View Patent ↗
Granted: Sep 18, 1990
Filed: Aug 17, 1989
Inventor
Keith Gustafson
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.