Granted Patent
Utility
US 4,869,318 · App. 07/242,530
Annulus valve for concentric tubing hangers
Inventor:
Rodney Kellett
Patented Case
View Patent ↗
Granted: Sep 26, 1989
Filed: Sep 12, 1988
Inventor
Rodney Kellett
Assignee (at issue)
Cameron Iron Works USA, 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.