Granted Patent
Utility
US 4,021,589 · App. 05/681,207
Buoyancy materials
Inventor:
John R. Copley
Patented Case
View Patent ↗
Granted: May 3, 1977
Filed: Apr 28, 1976
Inventor
John R. Copley
Assignee (at issue)
Emerson & Cuming, 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.