Granted Patent
Utility
US 4,357,023 · App. 06/208,289
Ferrofluid rotary-shaft seal apparatus and method
Inventor:
Akira Yamamura
Patented Case
View Patent ↗
Granted: Nov 2, 1982
Filed: Nov 19, 1980
Inventor
Akira Yamamura
Assignee (at issue)
Ferrofluidics 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.