Granted Patent
Utility
US 4,787,972 · App. 07/050,191
Two-stage filter apparatus
Inventor:
Warren Stubblebine
Patented Case
View Patent ↗
Granted: Nov 29, 1988
Filed: May 15, 1987
Inventor
Warren Stubblebine
Assignee (at issue)
STEIN & CO. GmbH
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.