Granted Patent
Utility
US 4,248,308 · App. 06/033,596
Externally adjusted spring actuated well valve
Inventor:
Ronald E. Pringle
Patented Case
View Patent ↗
Granted: Feb 3, 1981
Filed: Apr 27, 1979
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.