Granted Patent
Utility
US 4,930,921 · App. 07/287,602
Tubular writting pen with superposed pressure equalization chambers
Inventor:
Gerold Anderka
Patented Case
View Patent ↗
Granted: Jun 5, 1990
Filed: Dec 22, 1988
Inventor
Gerold Anderka
Assignee (at issue)
Koh-I-Noor Rapidograph, 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.