Granted Patent
Utility
US 4,773,625 · App. 07/025,215
Corrosion-resistant overlay for the edge of butterfly valves
Inventor:
Douglas G. Calvin
Patented Case
View Patent ↗
Granted: Sep 27, 1988
Filed: Mar 12, 1987
Inventor
Douglas G. Calvin
Assignee (at issue)
Keystone International
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.