Granted Patent
Utility
US 5,239,285 · App. 07/586,290
Low salt level sensor
Inventor:
Stanley F. Rak
Patented Case
View Patent ↗
Granted: Aug 24, 1993
Filed: Sep 21, 1990
Inventor
Stanley F. Rak
Assignee (at issue)
CULLIGAN INTERNATIONAL COMPANY
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.