Granted Patent
Utility
US 6,244,457 · App. 08/979,570
Gauge hatch with diaphragm and liquid seal
Inventors:
Thomas C. Piotrowski, Martin Clift
Patented Case
View Patent ↗
Granted: Jun 12, 2001
Filed: Nov 26, 1997
Inventors
Thomas C. Piotrowski
Martin Clift
Assignee (at issue)
THE PROTECTOSEAL 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.