Granted Patent
Utility
US 4,722,399 · App. 07/024,957
Self closing equalizing valve for a subsurface well safety valve
Inventor:
Ronald E. Pringle
Patented Case
View Patent ↗
Granted: Feb 2, 1988
Filed: Mar 12, 1987
Inventor
Ronald E. Pringle
Assignee (at issue)
Camco Inc.
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.