Granted Patent
Utility
US 4,977,957 · App. 07/415,677
Subsurface well safety valve with light weight components
Inventor:
Ronald E. Pringle
Patented Case
View Patent ↗
Granted: Dec 18, 1990
Filed: Oct 2, 1989
Inventor
Ronald E. Pringle
Assignee (at issue)
Camco International, 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.