Granted Patent
Utility
US 4,449,583 · App. 06/304,078
Well devices with annulus check valve and hydraulic by-pass
Inventor:
John E. Lawson
Patented Case
View Patent ↗
Granted: May 22, 1984
Filed: Sep 21, 1981
Inventor
John E. Lawson
Assignee (at issue)
Armco 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.