Granted Patent
Utility
US 4,846,218 · App. 07/202,215
Check valve for liquid chromatography pumps
Inventor:
Paul E. Upchurch
Patented Case
View Patent ↗
Granted: Jul 11, 1989
Filed: Jun 3, 1988
Inventor
Paul E. Upchurch
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.