Granted Patent
Utility
US 4,421,643 · App. 05/946,979
Swimming pool filtering system
Inventor:
Stanley H. Frederick
Patented Case
View Patent ↗
Granted: Dec 20, 1983
Filed: Sep 29, 1978
Inventor
Stanley H. Frederick
Assignee (at issue)
International Telephone and Telegraph Corporation
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.