Granted Patent
Utility
US 6,629,621 · App. 09/879,843
Gauge hatch with liquid seal
Inventors:
Thomas C. Piotrowski, Martin Clift, Baohai Liu
Patented Case
View Patent ↗
Granted: Oct 7, 2003
Filed: Jun 12, 2001
Inventors
Thomas C. Piotrowski
Martin Clift
Baohai Liu
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.