Granted Patent
Utility
US 6,557,220 · App. 10/063,982
Security clutch with self-centering spring
Inventor:
David Hamm
Patented Case
View Patent ↗
Granted: May 6, 2003
Filed: May 31, 2002
Inventor
David Hamm
Assignee (at issue)
B.A. BALLOU & CO. 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.