Granted Patent
Utility
US 5,058,538 · App. 07/557,369
Hydraulically propelled phneumatically returned valve actuator
Inventors:
Frederick L. Erickson, William E. Richeson
Patented Case
View Patent ↗
Granted: Oct 22, 1991
Filed: Jul 24, 1990
Inventors
Frederick L. Erickson
William E. Richeson
Assignee (at issue)
North American Philips Corporation
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.