Granted Patent
Utility
US 6,189,534 · App. 09/170,037
Bi-functional in-line phonation valve
Inventors:
John Zowtiak, John O'Mahony, David Frigger
Patented Case
View Patent ↗
Granted: Feb 20, 2001
Filed: Oct 13, 1998
Inventors
John Zowtiak
John O'Mahony
David Frigger
Assignee (at issue)
MALLINCKRODT LLC
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.