Granted Patent
Utility
US 4,738,431 · App. 06/942,998
Ball valve structure
Inventor:
Donald H. Perkins
Patented Case
View Patent ↗
Granted: Apr 19, 1988
Filed: Dec 18, 1986
Inventor
Donald H. Perkins
Assignee (at issue)
Otis Engineering 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.