Granted Patent
Utility
US 4,986,357 · App. 07/506,313
Well tool having a variable area hydraulic actuator
Inventor:
Ronald E. Pringle
Patented Case
View Patent ↗
Granted: Jan 22, 1991
Filed: Apr 9, 1990
Inventor
Ronald E. Pringle
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.